rfc9043v1.txt   rfc9043.txt 
Internet Engineering Task Force (IETF) M. Niedermayer Internet Engineering Task Force (IETF) M. Niedermayer
Request for Comments: 9043 Request for Comments: 9043
Category: Informational D. Rice Category: Informational D. Rice
ISSN: 2070-1721 ISSN: 2070-1721
J. Martinez J. Martinez
June 2021 August 2021
FFV1 Video Coding Format Version 0, 1, and 3 FFV1 Video Coding Format Versions 0, 1, and 3
Abstract Abstract
This document defines FFV1, a lossless, intra-frame video encoding This document defines FFV1, a lossless, intra-frame video encoding
format. FFV1 is designed to efficiently compress video data in a format. FFV1 is designed to efficiently compress video data in a
variety of pixel formats. Compared to uncompressed video, FFV1 variety of pixel formats. Compared to uncompressed video, FFV1
offers storage compression, frame fixity, and self-description, which offers storage compression, frame fixity, and self-description, which
makes FFV1 useful as a preservation or intermediate video format. makes FFV1 useful as a preservation or intermediate video format.
Status of This Memo Status of This Memo
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3.6. Quantization Table Set Indexes 3.6. Quantization Table Set Indexes
3.7. Color Spaces 3.7. Color Spaces
3.7.1. YCbCr 3.7.1. YCbCr
3.7.2. RGB 3.7.2. RGB
3.8. Coding of the Sample Difference 3.8. Coding of the Sample Difference
3.8.1. Range Coding Mode 3.8.1. Range Coding Mode
3.8.2. Golomb Rice Mode 3.8.2. Golomb Rice Mode
4. Bitstream 4. Bitstream
4.1. Quantization Table Set 4.1. Quantization Table Set
4.1.1. "quant_tables" 4.1.1. "quant_tables"
4.1.2. context_count 4.1.2. "context_count"
4.2. Parameters 4.2. Parameters
4.2.1. version 4.2.1. "version"
4.2.2. micro_version 4.2.2. "micro_version"
4.2.3. coder_type 4.2.3. "coder_type"
4.2.4. state_transition_delta 4.2.4. "state_transition_delta"
4.2.5. colorspace_type 4.2.5. "colorspace_type"
4.2.6. chroma_planes 4.2.6. "chroma_planes"
4.2.7. bits_per_raw_sample 4.2.7. "bits_per_raw_sample"
4.2.8. log2_h_chroma_subsample 4.2.8. "log2_h_chroma_subsample"
4.2.9. log2_v_chroma_subsample 4.2.9. "log2_v_chroma_subsample"
4.2.10. extra_plane 4.2.10. "extra_plane"
4.2.11. num_h_slices 4.2.11. "num_h_slices"
4.2.12. num_v_slices 4.2.12. "num_v_slices"
4.2.13. quant_table_set_count 4.2.13. "quant_table_set_count"
4.2.14. states_coded 4.2.14. "states_coded"
4.2.15. initial_state_delta 4.2.15. "initial_state_delta"
4.2.16. ec 4.2.16. "ec"
4.2.17. intra 4.2.17. "intra"
4.3. Configuration Record 4.3. Configuration Record
4.3.1. reserved_for_future_use 4.3.1. "reserved_for_future_use"
4.3.2. configuration_record_crc_parity 4.3.2. "configuration_record_crc_parity"
4.3.3. Mapping FFV1 into Containers 4.3.3. Mapping FFV1 into Containers
4.4. Frame 4.4. Frame
4.5. Slice 4.5. Slice
4.6. Slice Header 4.6. Slice Header
4.6.1. slice_x 4.6.1. "slice_x"
4.6.2. slice_y 4.6.2. "slice_y"
4.6.3. slice_width 4.6.3. "slice_width"
4.6.4. slice_height 4.6.4. "slice_height"
4.6.5. quant_table_set_index_count 4.6.5. "quant_table_set_index_count"
4.6.6. quant_table_set_index 4.6.6. "quant_table_set_index"
4.6.7. picture_structure 4.6.7. "picture_structure"
4.6.8. sar_num 4.6.8. "sar_num"
4.6.9. sar_den 4.6.9. "sar_den"
4.7. Slice Content 4.7. Slice Content
4.7.1. primary_color_count 4.7.1. "primary_color_count"
4.7.2. plane_pixel_height 4.7.2. "plane_pixel_height"
4.7.3. slice_pixel_height 4.7.3. "slice_pixel_height"
4.7.4. slice_pixel_y 4.7.4. "slice_pixel_y"
4.8. Line 4.8. Line
4.8.1. plane_pixel_width 4.8.1. "plane_pixel_width"
4.8.2. slice_pixel_width 4.8.2. "slice_pixel_width"
4.8.3. slice_pixel_x 4.8.3. "slice_pixel_x"
4.8.4. sample_difference 4.8.4. "sample_difference"
4.9. Slice Footer 4.9. Slice Footer
4.9.1. slice_size 4.9.1. "slice_size"
4.9.2. error_status 4.9.2. "error_status"
4.9.3. slice_crc_parity 4.9.3. "slice_crc_parity"
5. Restrictions 5. Restrictions
6. Security Considerations 6. Security Considerations
7. IANA Considerations 7. IANA Considerations
7.1. Media Type Definition 7.1. Media Type Definition
8. References 8. References
8.1. Normative References 8.1. Normative References
8.2. Informative References 8.2. Informative References
Appendix A. Multithreaded Decoder Implementation Suggestions Appendix A. Multithreaded Decoder Implementation Suggestions
Appendix B. Future Handling of Some Streams Created by Appendix B. Future Handling of Some Streams Created by
Nonconforming Encoders Nonconforming Encoders
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description of the characteristics of the encoding images and description of the characteristics of the encoding images and
embedded Cyclic Redundancy Check (CRC) data to support fixity embedded Cyclic Redundancy Check (CRC) data to support fixity
verification of the encoding. Version 3 was flagged as stable on verification of the encoding. Version 3 was flagged as stable on
August 17, 2013 [FFV1_V3]. August 17, 2013 [FFV1_V3].
This document assumes familiarity with mathematical and coding This document assumes familiarity with mathematical and coding
concepts such as Range encoding [Range-Encoding] and YCbCr color concepts such as Range encoding [Range-Encoding] and YCbCr color
spaces [YCbCr]. spaces [YCbCr].
This specification describes the valid bitstream and how to decode This specification describes the valid bitstream and how to decode
such valid bitstream. Bitstreams not conforming to this it. Nonconformant bitstreams and the nonconformant handling of
specification or how they are handled is outside this specification. bitstreams are outside this specification. A decoder can perform any
A decoder could reject every invalid bitstream or attempt to perform action that it deems appropriate for an invalid bitstream: reject the
error concealment or re-download or use a redundant copy of the bitstream, attempt to perform error concealment, or re-download or
invalid part or any other action it deems appropriate. use a redundant copy of the invalid part.
2. Notation and Conventions 2. Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.1. Definitions 2.1. Definitions
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variable number of bits. variable number of bits.
RGB: A reference to the method of storing the value of a pixel by RGB: A reference to the method of storing the value of a pixel by
using three numeric values that represent Red, Green, and Blue. using three numeric values that represent Red, Green, and Blue.
YCbCr: A reference to the method of storing the value of a pixel by YCbCr: A reference to the method of storing the value of a pixel by
using three numeric values that represent the luma of the pixel using three numeric values that represent the luma of the pixel
(Y) and the chroma of the pixel (Cb and Cr). The term YCbCr is (Y) and the chroma of the pixel (Cb and Cr). The term YCbCr is
used for historical reasons and currently references any color used for historical reasons and currently references any color
space relying on one luma Sample and two chroma Samples, e.g., space relying on one luma Sample and two chroma Samples, e.g.,
YCbCr, YCgCo, or ICtCp. The exact meaning of the three numeric YCbCr (luma, blue-difference chroma, red-difference chroma),
values is unspecified. YCgCo, or ICtCp (intensity, blue-yellow, red-green).
2.2. Conventions 2.2. Conventions
2.2.1. Pseudocode 2.2.1. Pseudocode
The FFV1 bitstream is described in this document using pseudocode. The FFV1 bitstream is described in this document using pseudocode.
Note that the pseudocode is used to illustrate the structure of FFV1 Note that the pseudocode is used to illustrate the structure of FFV1
and is not intended to specify any particular implementation. The and is not intended to specify any particular implementation. The
pseudocode used is based upon the C programming language pseudocode used is based upon the C programming language
[ISO.9899.2018] and uses its "if/else", "while", and "for" keywords [ISO.9899.2018] and uses its "if/else", "while", and "for" keywords
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"a ^ b" means a raised to the b-th power. "a ^ b" means a raised to the b-th power.
"a & b" means bitwise "and" of a and b. "a & b" means bitwise "and" of a and b.
"a | b" means bitwise "or" of a and b. "a | b" means bitwise "or" of a and b.
"a >> b" means arithmetic right shift of the two's complement integer "a >> b" means arithmetic right shift of the two's complement integer
representation of a by b binary digits. This is equivalent to representation of a by b binary digits. This is equivalent to
dividing a by 2, b times, with rounding toward negative infinity. dividing a by 2, b times, with rounding toward negative infinity.
"a << b" means arithmetic left shift of two's complement integer "a << b" means arithmetic left shift of the two's complement integer
representation of a by b binary digits. representation of a by b binary digits.
2.2.3. Assignment Operators 2.2.3. Assignment Operators
"a = b" means a is assigned b. "a = b" means a is assigned b.
"a++" is equivalent to a is assigned a + 1. "a++" is equivalent to a is assigned a + 1.
"a--" is equivalent to a is assigned a - 1. "a--" is equivalent to a is assigned a - 1.
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"max(a,b)" means the larger of two values a and b. "max(a,b)" means the larger of two values a and b.
"median(a,b,c)" means the numerical middle value in a data set of a, "median(a,b,c)" means the numerical middle value in a data set of a,
b, and c, i.e., "a+b+c-min(a,b,c)-max(a,b,c)". b, and c, i.e., "a+b+c-min(a,b,c)-max(a,b,c)".
"a ==> b" means a implies b. "a ==> b" means a implies b.
"a <==> b" means a ==> b, b ==> a. "a <==> b" means a ==> b, b ==> a.
a_b means the b-th value of a sequence of a. "a_b" means the b-th value of a sequence of a.
a_(b,c) means the 'b,c'-th value of a sequence of a. "a_(b,c)" means the 'b,c'-th value of a sequence of a.
2.2.6. Order of Operation Precedence 2.2.6. Order of Operation Precedence
When order of precedence is not indicated explicitly by use of When order of precedence is not indicated explicitly by use of
parentheses, operations are evaluated in the following order (from parentheses, operations are evaluated in the following order (from
top to bottom, operations of same precedence being evaluated from top to bottom, operations of same precedence being evaluated from
left to right). This order of operations is based on the order of left to right). This order of operations is based on the order of
operations used in Standard C. operations used in Standard C.
a++, a-- a++, a--
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2.2.9.1. remaining_bits_in_bitstream 2.2.9.1. remaining_bits_in_bitstream
"remaining_bits_in_bitstream( NumBytes )" means the count of "remaining_bits_in_bitstream( NumBytes )" means the count of
remaining bits after the pointer in that "Configuration Record" or remaining bits after the pointer in that "Configuration Record" or
"Frame". It is computed from the "NumBytes" value multiplied by 8 "Frame". It is computed from the "NumBytes" value multiplied by 8
minus the count of bits of that "Configuration Record" or "Frame" minus the count of bits of that "Configuration Record" or "Frame"
already read by the bitstream parser. already read by the bitstream parser.
2.2.9.2. remaining_symbols_in_syntax 2.2.9.2. remaining_symbols_in_syntax
"remaining_symbols_in_syntax( )" is true as long as the RangeCoder "remaining_symbols_in_syntax( )" is true as long as the range coder
has not consumed all the given input bytes. has not consumed all the given input bytes.
2.2.9.3. byte_aligned 2.2.9.3. byte_aligned
"byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes "byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes
)" is a multiple of 8, otherwise false. )" is a multiple of 8, otherwise false.
2.2.9.4. get_bits 2.2.9.4. get_bits
"get_bits( i )" is the action to read the next "i" bits in the "get_bits( i )" is the action to read the next "i" bits in the
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color space (see Section 3.7). Each Sample is predicted by the color space (see Section 3.7). Each Sample is predicted by the
median predictor as described in Section 3.3 from other Samples median predictor as described in Section 3.3 from other Samples
within the same Plane, and the difference is stored using the method within the same Plane, and the difference is stored using the method
described in Section 3.8. described in Section 3.8.
3.1. Border 3.1. Border
A border is assumed for each coded "Slice" for the purpose of the A border is assumed for each coded "Slice" for the purpose of the
median predictor and context according to the following rules: median predictor and context according to the following rules:
* One column of Samples to the left of the coded slice is assumed as * One column of Samples to the left of the coded Slice is assumed as
identical to the Samples of the leftmost column of the coded slice identical to the Samples of the leftmost column of the coded Slice
shifted down by one row. The value of the topmost Sample of the shifted down by one row. The value of the topmost Sample of the
column of Samples to the left of the coded slice is assumed to be column of Samples to the left of the coded Slice is assumed to be
"0". "0".
* One column of Samples to the right of the coded slice is assumed * One column of Samples to the right of the coded Slice is assumed
as identical to the Samples of the rightmost column of the coded as identical to the Samples of the rightmost column of the coded
slice. Slice.
* An additional column of Samples to the left of the coded slice and * An additional column of Samples to the left of the coded Slice and
two rows of Samples above the coded slice are assumed to be "0". two rows of Samples above the coded Slice are assumed to be "0".
Figure 2 depicts a slice of nine Samples "a,b,c,d,e,f,g,h,i" in a Figure 2 depicts a Slice of nine Samples "a,b,c,d,e,f,g,h,i" in a
three-by-three arrangement along with its assumed border. three-by-three arrangement along with its assumed border.
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | a | b | c | | c | | 0 | 0 | | a | b | c | | c |
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left16s = l >= 32768 ? ( l - 65536 ) : l left16s = l >= 32768 ? ( l - 65536 ) : l
top16s = t >= 32768 ? ( t - 65536 ) : t top16s = t >= 32768 ? ( t - 65536 ) : t
diag16s = tl >= 32768 ? ( tl - 65536 ) : tl diag16s = tl >= 32768 ? ( tl - 65536 ) : tl
Background: a two's complement 16-bit signed integer was used for Background: a two's complement 16-bit signed integer was used for
storing Sample values in all known implementations of FFV1 bitstream storing Sample values in all known implementations of FFV1 bitstream
(see Appendix C). So in some circumstances, the most significant bit (see Appendix C). So in some circumstances, the most significant bit
was wrongly interpreted (used as a sign bit instead of the 16th bit was wrongly interpreted (used as a sign bit instead of the 16th bit
of an unsigned integer). Note that when the issue was discovered, of an unsigned integer). Note that when the issue was discovered,
the only impacted configuration of all known implementations was the the only impacted configuration of all known implementations was the
16-bit YCbCr with no pixel transformation and with the Range Coder 16-bit YCbCr with no pixel transformation and with the range coder
coder type, as the other potentially impacted configurations (e.g., coder type, as the other potentially impacted configurations (e.g.,
the 15/16-bit JPEG 2000 Reversible Color Transform (RCT) the 15/16-bit JPEG 2000 Reversible Color Transform (RCT)
[ISO.15444-1.2016] with Range Coder or the 16-bit content with the [ISO.15444-1.2019] with range coder or the 16-bit content with the
Golomb Rice coder type) were not implemented. Meanwhile, the 16-bit Golomb Rice coder type) were not implemented. Meanwhile, the 16-bit
JPEG 2000 RCT with Range Coder was deployed without this issue in one JPEG 2000 RCT with range coder was deployed without this issue in one
implementation and validated by one conformance checker. It is implementation and validated by one conformance checker. It is
expected (to be confirmed) that this exception for the median expected (to be confirmed) that this exception for the median
predictor will be removed in the next version of the FFV1 bitstream. predictor will be removed in the next version of the FFV1 bitstream.
3.4. Quantization Table Sets 3.4. Quantization Table Sets
Quantization Tables are used on Sample Differences (see Section 3.8), Quantization Tables are used on Sample Differences (see Section 3.8),
so Quantized Sample Differences are stored in the bitstream. so Quantized Sample Differences are stored in the bitstream.
The FFV1 bitstream contains one or more Quantization Table Sets. The FFV1 bitstream contains one or more Quantization Table Sets.
Each Quantization Table Set contains exactly five Quantization Tables Each Quantization Table Set contains exactly five Quantization Tables
with each Quantization Table corresponding to one of the five with each Quantization Table corresponding to one of the five
Quantized Sample Differences. For each Quantization Table, both the Quantized Sample Differences. For each Quantization Table, both the
number of quantization steps and their distribution are stored in the number of quantization steps and their distribution are stored in the
FFV1 bitstream; each Quantization Table has exactly 256 entries, and FFV1 bitstream; each Quantization Table has exactly 256 entries, and
the eight least significant bits of the Quantized Sample Difference the eight least significant bits of the Quantized Sample Difference
are used as an index: are used as an index:
Q_j[k] = quant_tables[i][j][k&255] Q_j[k] = quant_tables[i][j][k&255]
Figure 4 Figure 4: Description of the mapping from sample differences to the
corresponding Quantized Sample Differences.
In this formula, "i" is the Quantization Table Set index, "j" is the In this formula, "i" is the Quantization Table Set index, "j" is the
Quantized Table index, and "k" is the Quantized Sample Difference Quantized Table index, and "k" is the Quantized Sample Difference
(see Section 4.1.1). (see Section 4.1.1).
3.5. Context 3.5. Context
Relative to any Sample "X", the Quantized Sample Differences "L-l", Relative to any Sample "X", the Quantized Sample Differences "L-l",
"l-tl", "tl-t", "T-t", and "t-tr" are used as context: "l-tl", "tl-t", "T-t", and "t-tr" are used as context:
context = Q_0[l - tl] + context = Q_0[l - tl] +
Q_1[tl - t] + Q_1[tl - t] +
Q_2[t - tr] + Q_2[t - tr] +
Q_3[L - l] + Q_3[L - l] +
Q_4[T - t] Q_4[T - t]
Figure 5 Figure 5: Description of the computing of the Context.
If "context >= 0" then "context" is used, and the difference between If "context >= 0" then "context" is used, and the difference between
the Sample and its predicted value is encoded as is; else "-context" the Sample and its predicted value is encoded as is; else "-context"
is used, and the difference between the Sample and its predicted is used, and the difference between the Sample and its predicted
value is encoded with a flipped sign. value is encoded with a flipped sign.
3.6. Quantization Table Set Indexes 3.6. Quantization Table Set Indexes
For each Plane of each slice, a Quantization Table Set is selected For each Plane of each Slice, a Quantization Table Set is selected
from an index: from an index:
* For Y Plane, "quant_table_set_index[ 0 ]" index is used. * For Y Plane, "quant_table_set_index[ 0 ]" index is used.
* For Cb and Cr Planes, "quant_table_set_index[ 1 ]" index is used. * For Cb and Cr Planes, "quant_table_set_index[ 1 ]" index is used.
* For extra Plane, "quant_table_set_index[ (version <= 3 || * For extra Plane, "quant_table_set_index[ (version <= 3 ||
chroma_planes) ? 2 : 1 ]" index is used. chroma_planes) ? 2 : 1 ]" index is used.
Background: in the first implementations of the FFV1 bitstream, the Background: in the first implementations of the FFV1 bitstream, the
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is used, then it MUST be coded last. is used, then it MUST be coded last.
3.7.2. RGB 3.7.2. RGB
This color space allows three or four Planes. This color space allows three or four Planes.
An optional transparency Plane can be used to code transparency data. An optional transparency Plane can be used to code transparency data.
JPEG 2000 RCT is a Reversible Color Transform that codes RGB (Red, JPEG 2000 RCT is a Reversible Color Transform that codes RGB (Red,
Green, Blue) Planes losslessly in a modified YCbCr color space Green, Blue) Planes losslessly in a modified YCbCr color space
[ISO.15444-1.2016]. Reversible pixel transformations between YCbCr [ISO.15444-1.2019]. Reversible pixel transformations between YCbCr
and RGB use the following formulae: and RGB use the following formulae:
Cb = b - g Cb = b - g
Cr = r - g Cr = r - g
Y = g + (Cb + Cr) >> 2 Y = g + (Cb + Cr) >> 2
Figure 6: Description of the transformation of pixels from RGB Figure 6: Description of the transformation of pixels from RGB
color space to coded, modified YCbCr color space. color space to coded, modified YCbCr color space.
g = Y - (Cb + Cr) >> 2 g = Y - (Cb + Cr) >> 2
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| Pixel(1,2) | Pixel(2,2) | | Pixel(1,2) | Pixel(2,2) |
| Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) | | Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) |
+------------------------+------------------------+ +------------------------+------------------------+
In JPEG 2000 RCT, the coding order is left to right and then top to In JPEG 2000 RCT, the coding order is left to right and then top to
bottom, with values interleaved by Lines and stored in this order: bottom, with values interleaved by Lines and stored in this order:
Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2) Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2)
Cb(2,2) Cr(1,2) Cr(2,2) Cb(2,2) Cr(1,2) Cr(2,2)
3.7.2.1. Exception 3.7.2.1. RGB Exception
If "bits_per_raw_sample" is between 9 and 15 inclusive and If "bits_per_raw_sample" is between 9 and 15 inclusive and
"extra_plane" is 0, the following formulae for reversible conversions "extra_plane" is 0, the following formulae for reversible conversions
between YCbCr and RGB MUST be used instead of the ones above: between YCbCr and RGB MUST be used instead of the ones above:
Cb = g - b Cb = g - b
Cr = r - b Cr = r - b
Y = b + (Cb + Cr) >> 2 Y = b + (Cb + Cr) >> 2
Figure 8: Description of the transformation of pixels from RGB Figure 8: Description of the transformation of pixels from RGB
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b = Y - (Cb + Cr) >> 2 b = Y - (Cb + Cr) >> 2
r = Cr + b r = Cr + b
g = Cb + b g = Cb + b
Figure 9: Description of the transformation of pixels from coded, Figure 9: Description of the transformation of pixels from coded,
modified YCbCr color space to RGB color space (in case of modified YCbCr color space to RGB color space (in case of
exception). exception).
Background: At the time of this writing, in all known implementations Background: At the time of this writing, in all known implementations
of the FFV1 bitstream, when "bits_per_raw_sample" was between 9 and of the FFV1 bitstream, when "bits_per_raw_sample" was between 9 and
15 inclusive and "extra_plane" was 0, GBR Planes were used as BGR 15 inclusive and "extra_plane" was 0, Green Blue Red (GBR) Planes
Planes during both encoding and decoding. Meanwhile, 16-bit JPEG were used as Blue Green Red (BGR) Planes during both encoding and
2000 RCT was implemented without this issue in one implementation and decoding. Meanwhile, 16-bit JPEG 2000 RCT was implemented without
validated by one conformance checker. Methods to address this this issue in one implementation and validated by one conformance
exception for the transform are under consideration for the next checker. Methods to address this exception for the transform are
version of the FFV1 bitstream. under consideration for the next version of the FFV1 bitstream.
3.8. Coding of the Sample Difference 3.8. Coding of the Sample Difference
Instead of coding the n+1 bits of the Sample Difference with Huffman Instead of coding the n+1 bits of the Sample Difference with Huffman
or Range coding (or n+2 bits, in the case of JPEG 2000 RCT), only the or Range coding (or n+2 bits, in the case of JPEG 2000 RCT), only the
n (or n+1, in the case of JPEG 2000 RCT) least significant bits are n (or n+1, in the case of JPEG 2000 RCT) least significant bits are
used, since this is sufficient to recover the original Sample. In used, since this is sufficient to recover the original Sample. In
Figure 10, the term "bits" represents "bits_per_raw_sample + 1" for Figure 10, the term "bits" represents "bits_per_raw_sample + 1" for
JPEG 2000 RCT or "bits_per_raw_sample" otherwise: JPEG 2000 RCT or "bits_per_raw_sample" otherwise:
coder_input = ((sample_difference + 2 ^ (bits - 1)) & coder_input = ((sample_difference + 2 ^ (bits - 1)) &
(2 ^ bits - 1)) - 2 ^ (bits - 1) (2 ^ bits - 1)) - 2 ^ (bits - 1)
Figure 10: Description of the coding of the Sample Difference in Figure 10: Description of the coding of the Sample Difference in
the bitstream. the bitstream.
3.8.1. Range Coding Mode 3.8.1. Range Coding Mode
Early experimental versions of FFV1 used the Context-Adaptive Binary Early experimental versions of FFV1 used the Context-Adaptive Binary
Arithmetic Coding (CABAC) coder from H.264 as defined in Arithmetic Coding (CABAC) coder from H.264 as defined in
[ISO.14496-10.2014], but due to the uncertain patent/royalty [ISO.14496-10.2020], but due to the uncertain patent/royalty
situation, as well as its slightly worse performance, CABAC was situation, as well as its slightly worse performance, CABAC was
replaced by a Range coder based on an algorithm defined by G. Nigel replaced by a range coder based on an algorithm defined by G. Nigel
N. Martin in 1979 [Range-Encoding]. N. Martin in 1979 [Range-Encoding].
3.8.1.1. Range Binary Values 3.8.1.1. Range Binary Values
To encode binary digits efficiently, a Range coder is used. A Range To encode binary digits efficiently, a range coder is used. A range
coder encodes a series of binary symbols by using a probability coder encodes a series of binary symbols by using a probability
estimation within each context. The sizes of each of the two estimation within each context. The sizes of each of the two
subranges are proportional to their estimated probability. The subranges are proportional to their estimated probability. The
Quantization Table is used to choose the context used from the Quantization Table is used to choose the context used from the
surrounding image sample values for the case of coding the sample surrounding image sample values for the case of coding the Sample
differences. The coding of integers is done by coding multiple Differences. The coding of integers is done by coding multiple
binary values. The range decoder will read bytes until it can binary values. The range decoder will read bytes until it can
determine into which subrange the input falls to return the next determine into which subrange the input falls to return the next
binary symbol. binary symbol.
To describe Range coding for FFV1, the following values are used: To describe Range coding for FFV1, the following values are used:
C_i the i-th context. C_i the i-th context.
B_i the i-th byte of the bytestream. B_i the i-th byte of the bytestream.
skipping to change at line 770 skipping to change at line 771
t_i a temporary variable to transmit subranges between range coding t_i a temporary variable to transmit subranges between range coding
operations. operations.
b_i the i-th range-coded binary value. b_i the i-th range-coded binary value.
S_(0, i) the i-th initial state. S_(0, i) the i-th initial state.
j_n the length of the bytestream encoding n binary symbols. j_n the length of the bytestream encoding n binary symbols.
The following Range coder state variables are initialized to the The following range coder state variables are initialized to the
following values. The Range is initialized to a value of 65,280 following values. The Range is initialized to a value of 65,280
(expressed in base 16 as 0xFF00) as depicted in Figure 11. The Low (expressed in base 16 as 0xFF00) as depicted in Figure 11. The Low
is initialized according to the value of the first two bytes as is initialized according to the value of the first two bytes as
depicted in Figure 12. j_i tracks the length of the bytestream depicted in Figure 12. j_i tracks the length of the bytestream
encoding while incrementing from an initial value of j_0 to a final encoding while incrementing from an initial value of j_0 to a final
value of j_n. j_0 is initialized to 2 as depicted in Figure 13. value of j_n. j_0 is initialized to 2 as depicted in Figure 13.
R_0 = 65280 R_0 = 65280
Figure 11: The initial value for the Range. Figure 11: The initial value for the Range.
L_0 = 2 ^ 8 * B_0 + B_1 L_0 = 2 ^ 8 * B_0 + B_1
Figure 12: The initial value for Low is set according to the Figure 12: The initial value for Low is set according to the
first two bytes of the bytestream. first two bytes of the bytestream.
j_0 = 2 j_0 = 2
Figure 13: The initial value for j, the length of the bytestream Figure 13: The initial value for "j", the length of the
encoding. bytestream encoding.
The following equations define how the Range coder variables evolve The following equations define how the range coder variables evolve
as it reads or writes symbols. as it reads or writes symbols.
r_i = floor( ( R_i * S_(i, C_i) ) / 2 ^ 8 ) r_i = floor( ( R_i * S_(i, C_i) ) / 2 ^ 8 )
Figure 14: This formula shows the positioning of range split Figure 14: This formula shows the positioning of range split
based on the state. based on the state.
b_i = 0 <==> b_i = 0 <==>
L_i < R_i - r_i ==> L_i < R_i - r_i ==>
S_(i + 1, C_i) = zero_state_(S_(i, C_i)) AND S_(i+1,C_i) = zero_state_(S_(i, C_i)) AND
l_i = L_i AND l_i = L_i AND
t_i = R_i - r_i t_i = R_i - r_i
b_i = 1 <==> b_i = 1 <==>
L_i >= R_i - r_i ==> L_i >= R_i - r_i ==>
S_(i + 1, C_i) = one_state_(S_(i, C_i)) AND S_(i+1,C_i) = one_state_(S_(i, C_i)) AND
l_i = L_i - R_i + r_i AND l_i = L_i - R_i + r_i AND
t_i = r_i t_i = r_i
Figure 15: This formula shows the linking of the decoded symbol Figure 15: This formula shows the linking of the decoded symbol
(represented as b_i), the updated state (represented as (represented as b_i), the updated state (represented as
S_(i+1,C_i)), and the updated range (represented as a range from S_(i+1,C_i)), and the updated range (represented as a range from
l_i to t_i). l_i to t_i).
C_i != k ==> S_(i + 1, k) = S_(i, k) C_i != k ==> S_(i + 1, k) = S_(i, k)
Figure 16: If the value of "k" is unequal to the i-th value of Figure 16: If the value of "k" is unequal to the i-th value of
context, in other words, if the state is unchanged from the last context, in other words, if the state is unchanged from the last
symbol coding, then the value of the state is carried over to the symbol coding, then the value of the state is carried over to the
next symbol coding. next symbol coding.
t_i < 2 ^ 8 ==> t_i < 2 ^ 8 ==>
R_(i + 1) = 2 ^ 8 * t_i AND R_(i + 1) = 2 ^ 8 * t_i AND
L_(i + 1) = 2 ^ 8 * l_i + B_(j_i) AND L_(i + 1) = 2 ^ 8 * l_i + B_(j_i) AND
j_(i + 1) = j_i + 1 j_(i + 1) = j_i + 1
t_i >= 2 ^ 8 ==> t_i >= 2 ^ 8 ==>
R_(i + 1) = t_i AND R_(i + 1) = t_i AND
L_(i + 1) = l_i AND L_(i + 1) = l_i AND
j_(i + 1) = j_i j_(i + 1) = j_i
Figure 17: This formula shows the linking of the Range coder with Figure 17: This formula shows the linking of the range coder with
the reading or writing of the bytestream. the reading or writing of the bytestream.
range = 0xFF00; range = 0xFF00;
end = 0; end = 0;
low = get_bits(16); low = get_bits(16);
if (low >= range) { if (low >= range) {
low = range; low = range;
end = 1; end = 1;
} }
Figure 18: A pseudocode description of the initialization of Figure 18: A pseudocode description of the initialization of
Range coder variables in Range binary mode. range coder variables in Range binary mode.
refill() { refill() {
if (range < 256) { if (range < 256) {
range = range * 256; range = range * 256;
low = low * 256; low = low * 256;
if (!end) { if (!end) {
c.low += get_bits(8); c.low += get_bits(8);
if (remaining_bits_in_bitstream( NumBytes ) == 0) { if (remaining_bits_in_bitstream( NumBytes ) == 0) {
end = 1; end = 1;
} }
} }
} }
} }
Figure 19: A pseudocode description of refilling the binary value Figure 19: A pseudocode description of refilling the binary value
buffer of the Range coder. buffer of the range coder.
get_rac(state) { get_rac(state) {
rangeoff = (range * state) / 256; rangeoff = (range * state) / 256;
range -= rangeoff; range -= rangeoff;
if (low < range) { if (low < range) {
state = zero_state[state]; state = zero_state[state];
refill(); refill();
return 0; return 0;
} else { } else {
low -= range; low -= range;
skipping to change at line 915 skipping to change at line 916
Closed mode if the length can be determined. In this case, the Closed mode if the length can be determined. In this case, the
last (sentinel) symbol will be read uncorrupted and be of value 0. last (sentinel) symbol will be read uncorrupted and be of value 0.
The above describes the range decoding. Encoding is defined as any The above describes the range decoding. Encoding is defined as any
process that produces a decodable bytestream. process that produces a decodable bytestream.
There are three places where range coder termination is needed in There are three places where range coder termination is needed in
FFV1. The first is in the "Configuration Record", which in this case FFV1. The first is in the "Configuration Record", which in this case
the size of the range-coded bytestream is known and handled as Closed the size of the range-coded bytestream is known and handled as Closed
mode. The second is the switch from the "Slice Header", which is mode. The second is the switch from the "Slice Header", which is
range coded to Golomb-coded slices as Sentinel mode. The third is range coded to Golomb-coded Slices as Sentinel mode. The third is
the end of range-coded slices, which need to terminate before the CRC the end of range-coded Slices, which need to terminate before the CRC
at their end. This can be handled as Sentinel mode or as Closed mode at their end. This can be handled as Sentinel mode or as Closed mode
if the CRC position has been determined. if the CRC position has been determined.
3.8.1.2. Range Nonbinary Values 3.8.1.2. Range Nonbinary Values
To encode scalar integers, it would be possible to encode each bit To encode scalar integers, it would be possible to encode each bit
separately and use the past bits as context. However, that would separately and use the past bits as context. However, that would
mean 255 contexts per 8-bit symbol, which is not only a waste of mean 255 contexts per 8-bit symbol, which is not only a waste of
memory but also requires more past data to reach a reasonably good memory but also requires more past data to reach a reasonably good
estimate of the probabilities. Alternatively, it would also be estimate of the probabilities. Alternatively, it would also be
skipping to change at line 972 skipping to change at line 973
"get_symbol" is used for the read out of "sample_difference" "get_symbol" is used for the read out of "sample_difference"
indicated in Figure 10. indicated in Figure 10.
"get_rac" returns a boolean computed from the bytestream as described "get_rac" returns a boolean computed from the bytestream as described
by the formula found in Figure 14 and by the pseudocode found in by the formula found in Figure 14 and by the pseudocode found in
Figure 20. Figure 20.
3.8.1.3. Initial Values for the Context Model 3.8.1.3. Initial Values for the Context Model
When the "keyframe" value (see Section 4.4) is 1, all Range coder When the "keyframe" value (see Section 4.4) is 1, all range coder
state variables are set to their initial state. state variables are set to their initial state.
3.8.1.4. State Transition Table 3.8.1.4. State Transition Table
In this model, a state transition table is used, indicating to which In Range Coding Mode, a state transition table is used, indicating to
state the decoder will move based on the current state and the value which state the decoder will move based on the current state and the
extracted from Figure 20. value extracted from Figure 20.
one_state_i = one_state_i =
default_state_transition_i + state_transition_delta_i default_state_transition_i + state_transition_delta_i
Figure 22 Figure 22: Description of the coding of the state transition
table for a "get_rac" readout value of 1.
zero_state_i = 256 - one_state_(256-i) zero_state_i = 256 - one_state_(256-i)
Figure 23 Figure 23: Description of the coding of the state transition
table for a "get_rac" readout value of 0.
3.8.1.5. default_state_transition 3.8.1.5. default_state_transition
By default, the following state transition table is used: By default, the following state transition table is used:
0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42,
43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57,
skipping to change at line 1026 skipping to change at line 1029
180,181,182,183,184,185,186,187,188,189,190,190,191,192,194,194, 180,181,182,183,184,185,186,187,188,189,190,190,191,192,194,194,
195,196,197,198,199,200,201,202,202,204,205,206,207,208,209,209, 195,196,197,198,199,200,201,202,202,204,205,206,207,208,209,209,
210,211,212,213,215,215,216,217,218,219,220,220,222,223,224,225, 210,211,212,213,215,215,216,217,218,219,220,220,222,223,224,225,
226,227,227,229,229,230,231,232,234,234,235,236,237,238,239,240, 226,227,227,229,229,230,231,232,234,234,235,236,237,238,239,240,
241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0, 241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0,
Figure 24 Figure 24: Default state transition table for Range coding.
3.8.1.6. Alternative State Transition Table 3.8.1.6. Alternative State Transition Table
The alternative state transition table has been built using iterative The alternative state transition table has been built using iterative
minimization of frame sizes and generally performs better than the minimization of frame sizes and generally performs better than the
default. To use it, the "coder_type" (see Section 4.2.3) MUST be set default. To use it, the "coder_type" (see Section 4.2.3) MUST be set
to 2, and the difference to the default MUST be stored in the to 2, and the difference to the default MUST be stored in the
"Parameters", see Section 4.2. At the time of this writing, the "Parameters", see Section 4.2. At the time of this writing, the
reference implementation of FFV1 in FFmpeg uses Figure 25 by default reference implementation of FFV1 in FFmpeg uses Figure 25 by default
when Range coding is used. when Range coding is used.
skipping to change at line 1074 skipping to change at line 1077
209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225, 209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225,
226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242, 226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242,
241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255, 241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255,
Figure 25: Alternative state transition table for Range coding. Figure 25: Alternative state transition table for Range coding.
3.8.2. Golomb Rice Mode 3.8.2. Golomb Rice Mode
The end of the bitstream of the Frame is padded with 0-bits until the The end of the bitstream of the Frame is padded with zeroes until the
bitstream contains a multiple of eight bits. bitstream contains a multiple of eight bits.
3.8.2.1. Signed Golomb Rice Codes 3.8.2.1. Signed Golomb Rice Codes
This coding mode uses Golomb Rice codes. The VLC is split into two This coding mode uses Golomb Rice codes. The VLC is split into two
parts. The prefix stores the most significant bits, and the suffix parts: the prefix and suffix. The prefix stores the most significant
bits or indicates if the symbol is too large to be stored (this is
known as the ESC case, see Section 3.8.2.1.1). The suffix either
stores the k least significant bits or stores the whole number in the stores the k least significant bits or stores the whole number in the
ESC case (see Section 3.8.2.1.1). ESC case.
int get_ur_golomb(k) { int get_ur_golomb(k) {
for (prefix = 0; prefix < 12; prefix++) { for (prefix = 0; prefix < 12; prefix++) {
if (get_bits(1)) { if (get_bits(1)) {
return get_bits(k) + (prefix << k); return get_bits(k) + (prefix << k);
} }
} }
return get_bits(bits) + 11; return get_bits(bits) + 11;
} }
skipping to change at line 1125 skipping to change at line 1130
+----------------+-------+ +----------------+-------+
| 0000 0000 01 | 9 | | 0000 0000 01 | 9 |
+----------------+-------+ +----------------+-------+
| 0000 0000 001 | 10 | | 0000 0000 001 | 10 |
+----------------+-------+ +----------------+-------+
| 0000 0000 0001 | 11 | | 0000 0000 0001 | 11 |
+----------------+-------+ +----------------+-------+
| 0000 0000 0000 | ESC | | 0000 0000 0000 | ESC |
+----------------+-------+ +----------------+-------+
Table 1 Table 1: Description
of the coding of the
prefix of signed
Golomb Rice codes.
ESC is an ESCape symbol to indicate that the symbol to be stored is ESC is an ESCape symbol to indicate that the symbol to be stored is
too large for normal storage and that an alternate storage method is too large for normal storage and that an alternate storage method is
used. used.
3.8.2.1.2. Suffix 3.8.2.1.2. Suffix
+---------+----------------------------------------+ +---------+----------------------------------------+
| non-ESC | the k least significant bits MSB first | | non-ESC | the k least significant bits MSB first |
+---------+----------------------------------------+ +---------+----------------------------------------+
| ESC | the value - 11, in MSB first order | | ESC | the value - 11, in MSB first order |
+---------+----------------------------------------+ +---------+----------------------------------------+
Table 2 Table 2: Description of the coding of the suffix
of signed Golomb Rice codes.
ESC MUST NOT be used if the value can be coded as non-ESC. ESC MUST NOT be used if the value can be coded as non-ESC.
3.8.2.1.3. Examples 3.8.2.1.3. Examples
Table 3 shows practical examples of how signed Golomb Rice codes are Table 3 shows practical examples of how signed Golomb Rice codes are
decoded based on the series of bits extracted from the bitstream as decoded based on the series of bits extracted from the bitstream as
described by the method above: described by the method above:
+=====+=======================+=======+ +=====+=======================+=======+
skipping to change at line 1171 skipping to change at line 1180
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| any | 000000000000 10000000 | 139 | | any | 000000000000 10000000 | 139 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
Table 3: Examples of decoded, Table 3: Examples of decoded,
signed Golomb Rice codes. signed Golomb Rice codes.
3.8.2.2. Run Mode 3.8.2.2. Run Mode
Run mode is entered when the context is 0 and left as soon as a Run mode is entered when the context is 0 and left as soon as a
nonzero difference is found. The sample difference is identical to nonzero difference is found. The Sample Difference is identical to
the predicted one. The run and the first different sample difference the predicted one. The run and the first different Sample Difference
are coded as defined in Section 3.8.2.4.1. are coded as defined in Section 3.8.2.4.1.
3.8.2.2.1. Run Length Coding 3.8.2.2.1. Run Length Coding
The run value is encoded in two parts. The prefix part stores the The run value is encoded in two parts. The prefix part stores the
more significant part of the run as well as adjusting the "run_index" more significant part of the run as well as adjusting the "run_index"
that determines the number of bits in the less significant part of that determines the number of bits in the less significant part of
the run. The second part of the value stores the less significant the run. The second part of the value stores the less significant
part of the run as it is. The "run_index" is reset to zero for each part of the run as it is. The "run_index" is reset to zero for each
Plane and slice. Plane and Slice.
log2_run[41] = { log2_run[41] = {
0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7, 4, 4, 5, 5, 6, 6, 7, 7,
8, 9,10,11,12,13,14,15, 8, 9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23, 16,17,18,19,20,21,22,23,
24, 24,
}; };
skipping to change at line 1318 skipping to change at line 1327
Section 2.2.1 is used to explain the structure of each FFV1 bitstream Section 2.2.1 is used to explain the structure of each FFV1 bitstream
component. Table 4 lists symbols used to annotate that pseudocode in component. Table 4 lists symbols used to annotate that pseudocode in
order to define the storage of the data referenced in that line of order to define the storage of the data referenced in that line of
pseudocode. pseudocode.
+========+==================================================+ +========+==================================================+
| symbol | definition | | symbol | definition |
+========+==================================================+ +========+==================================================+
| u(n) | Unsigned, big-endian integer symbol using n bits | | u(n) | Unsigned, big-endian integer symbol using n bits |
+--------+--------------------------------------------------+ +--------+--------------------------------------------------+
| sg | Signed scalar symbol that is Golomb Rice coded |
| | with the method described in Section 3.8.2 |
+--------+--------------------------------------------------+
| br | Boolean (1-bit) symbol that is range coded with | | br | Boolean (1-bit) symbol that is range coded with |
| | the method described in Section 3.8.1.1 | | | the method described in Section 3.8.1.1 |
+--------+--------------------------------------------------+ +--------+--------------------------------------------------+
| ur | Unsigned scalar symbol that is range coded with | | ur | Unsigned scalar symbol that is range coded with |
| | the method described in Section 3.8.1.2 | | | the method described in Section 3.8.1.2 |
+--------+--------------------------------------------------+ +--------+--------------------------------------------------+
| sr | Signed scalar symbol that is range coded with | | sr | Signed scalar symbol that is range coded with |
| | the method described in Section 3.8.1.2 | | | the method described in Section 3.8.1.2 |
+--------+--------------------------------------------------+ +--------+--------------------------------------------------+
| sd | Sample difference symbol that is coded with the | | sd | Sample Difference symbol that is coded with the |
| | method described in Section 3.8 | | | method described in Section 3.8 |
+--------+--------------------------------------------------+ +--------+--------------------------------------------------+
Table 4: Definition of pseudocode symbols for this document. Table 4: Definition of pseudocode symbols for this document.
The following MUST be provided by external means during the The following MUST be provided by external means during the
initialization of the decoder: initialization of the decoder:
"frame_pixel_width" is defined as Frame width in pixels. "frame_pixel_width" is defined as Frame width in pixels.
"frame_pixel_height" is defined as Frame height in pixels. "frame_pixel_height" is defined as Frame height in pixels.
Default values at the decoder initialization phase: Default values at the decoder initialization phase:
"ConfigurationRecordIsPresent" is set to 0. "ConfigurationRecordIsPresent" is set to 0.
4.1. Quantization Table Set 4.1. Quantization Table Set
The Quantization Table Sets are stored by storing the number of equal The Quantization Table Sets store a sequence of values that are equal
entries -1 of the first half of the table (represented as "len - 1" to one less than the count of equal concurrent entries for each set
in the pseudocode below) using the method described in of equal concurrent entries within the first half of the table
Section 3.8.1.2. The second half doesn't need to be stored as it is (represented as "len - 1" in the pseudocode below) using the method
identical to the first with flipped sign. "scale" and "len_count[ i described in Section 3.8.1.2. The second half doesn't need to be
][ j ]" are temporary values used for the computing of stored as it is identical to the first with flipped sign. "scale" and
"len_count[ i ][ j ]" are temporary values used for the computing of
"context_count[ i ]" and are not used outside Quantization Table Set "context_count[ i ]" and are not used outside Quantization Table Set
pseudocode. pseudocode.
Example: Example:
Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0 Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0
Stored values: 1, 3, 1 Stored values: 1, 3, 1
"QuantizationTableSet" has its own initial states, all set to 128. "QuantizationTableSet" has its own initial states, all set to 128.
skipping to change at line 1406 skipping to change at line 1413
-quant_tables[ i ][ j ][ 127 ] | -quant_tables[ i ][ j ][ 127 ] |
len_count[ i ][ j ] = v | len_count[ i ][ j ] = v |
} | } |
4.1.1. "quant_tables" 4.1.1. "quant_tables"
"quant_tables[ i ][ j ][ k ]" indicates the Quantization Table value "quant_tables[ i ][ j ][ k ]" indicates the Quantization Table value
of the Quantized Sample Difference "k" of the Quantization Table "j" of the Quantized Sample Difference "k" of the Quantization Table "j"
of the Quantization Table Set "i". of the Quantization Table Set "i".
4.1.2. context_count 4.1.2. "context_count"
"context_count[ i ]" indicates the count of contexts for Quantization "context_count[ i ]" indicates the count of contexts for Quantization
Table Set "i". "context_count[ i ]" MUST be less than or equal to Table Set "i". "context_count[ i ]" MUST be less than or equal to
32768. 32768.
4.2. Parameters 4.2. Parameters
The "Parameters" section contains significant characteristics about The "Parameters" section, which could be in a global header of a
the decoding configuration used for all instances of Frame (in FFV1 container file that may or may not be considered to be part of the
versions 0 and 1) or the whole FFV1 bitstream (other versions), bitstream, contains significant characteristics about the decoding
including the stream version, color configuration, and Quantization configuration used for all instances of Frame (in FFV1 versions 0 and
Tables. Figure 28 describes the contents of the bitstream. 1) or the whole FFV1 bitstream (other versions), including the stream
version, color configuration, and Quantization Tables. Figure 28
describes the contents of the bitstream.
"Parameters" has its own initial states, all set to 128. "Parameters" has its own initial states, all set to 128.
pseudocode | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Parameters( ) { | Parameters( ) { |
version | ur version | ur
if (version >= 3) { | if (version >= 3) { |
micro_version | ur micro_version | ur
} | } |
skipping to change at line 1471 skipping to change at line 1480
} | } |
ec | ur ec | ur
intra | ur intra | ur
} | } |
} | } |
Figure 28: A pseudocode description of the bitstream contents. Figure 28: A pseudocode description of the bitstream contents.
CONTEXT_SIZE is 32. CONTEXT_SIZE is 32.
4.2.1. version 4.2.1. "version"
"version" specifies the version of the FFV1 bitstream. "version" specifies the version of the FFV1 bitstream.
Each version is incompatible with other versions: decoders SHOULD Each version is incompatible with other versions: decoders SHOULD
reject FFV1 bitstreams due to an unknown version. reject FFV1 bitstreams due to an unknown version.
Decoders SHOULD reject FFV1 bitstreams with "version <= 1 && Decoders SHOULD reject FFV1 bitstreams with "version <= 1 &&
ConfigurationRecordIsPresent == 1". ConfigurationRecordIsPresent == 1".
Decoders SHOULD reject FFV1 bitstreams with "version >= 3 && Decoders SHOULD reject FFV1 bitstreams with "version >= 3 &&
skipping to change at line 1498 skipping to change at line 1507
+-------+-------------------------+ +-------+-------------------------+
| 1 | FFV1 version 1 | | 1 | FFV1 version 1 |
+-------+-------------------------+ +-------+-------------------------+
| 2 | reserved* | | 2 | reserved* |
+-------+-------------------------+ +-------+-------------------------+
| 3 | FFV1 version 3 | | 3 | FFV1 version 3 |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 5 Table 5: The definitions for
"version" values.
* Version 2 was experimental and this document does not describe it. * Version 2 was experimental and this document does not describe it.
4.2.2. micro_version 4.2.2. "micro_version"
"micro_version" specifies the micro-version of the FFV1 bitstream. "micro_version" specifies the micro-version of the FFV1 bitstream.
After a version is considered stable (a micro-version value is After a version is considered stable (a micro-version value is
assigned to be the first stable variant of a specific version), each assigned to be the first stable variant of a specific version), each
new micro-version after this first stable variant is compatible with new micro-version after this first stable variant is compatible with
the previous micro-version: decoders SHOULD NOT reject FFV1 the previous micro-version: decoders SHOULD NOT reject FFV1
bitstreams due to an unknown micro-version equal or above the micro- bitstreams due to an unknown micro-version equal or above the micro-
version considered as stable. version considered as stable.
skipping to change at line 1531 skipping to change at line 1541
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 6: The definitions for Table 6: The definitions for
"micro_version" values for FFV1 "micro_version" values for FFV1
version 3. version 3.
* Development versions may be incompatible with the stable variants. * Development versions may be incompatible with the stable variants.
4.2.3. coder_type 4.2.3. "coder_type"
"coder_type" specifies the coder used. "coder_type" specifies the coder used.
+=======+=================================================+ +=======+=================================================+
| value | coder used | | value | coder used |
+=======+=================================================+ +=======+=================================================+
| 0 | Golomb Rice | | 0 | Golomb Rice |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 1 | Range Coder with default state transition table | | 1 | Range coder with default state transition table |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 2 | Range Coder with custom state transition table | | 2 | Range coder with custom state transition table |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
Table 7 Table 7: The definitions for "coder_type" values.
Restrictions: Restrictions:
If "coder_type" is 0, then "bits_per_raw_sample" SHOULD NOT be > 8. If "coder_type" is 0, then "bits_per_raw_sample" SHOULD NOT be > 8.
Background: At the time of this writing, there is no known Background: At the time of this writing, there is no known
implementation of FFV1 bitstream supporting the Golomb Rice algorithm implementation of FFV1 bitstream supporting the Golomb Rice algorithm
with "bits_per_raw_sample" greater than eight, and Range Coder is with "bits_per_raw_sample" greater than eight, and range coder is
preferred. preferred.
4.2.4. state_transition_delta 4.2.4. "state_transition_delta"
"state_transition_delta" specifies the Range coder custom state "state_transition_delta" specifies the range coder custom state
transition table. transition table.
If "state_transition_delta" is not present in the FFV1 bitstream, all If "state_transition_delta" is not present in the FFV1 bitstream, all
Range coder custom state transition table elements are assumed to be range coder custom state transition table elements are assumed to be
0. 0.
4.2.5. colorspace_type 4.2.5. "colorspace_type"
"colorspace_type" specifies the color space encoded, the pixel "colorspace_type" specifies the color space encoded, the pixel
transformation used by the encoder, the extra Plane content, as well transformation used by the encoder, the extra Plane content, as well
as interleave method. as interleave method.
+=======+==============+================+==============+============+ +=======+==============+================+==============+============+
| value | color space | pixel | extra Plane | interleave | | value | color space | pixel | extra Plane | interleave |
| | encoded | transformation | content | method | | | encoded | transformation | content | method |
+=======+==============+================+==============+============+ +=======+==============+================+==============+============+
| 0 | YCbCr | None | Transparency | Plane then | | 0 | YCbCr | None | Transparency | Plane then |
| | | | | Line | | | | | | Line |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
| 1 | RGB | JPEG 2000 RCT | Transparency | Line then | | 1 | RGB | JPEG 2000 RCT | Transparency | Line then |
| | | | | Plane | | | | | | Plane |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
| Other | reserved | reserved for | reserved for | reserved | | Other | reserved | reserved for | reserved for | reserved |
| | for future | future use | future use | for future | | | for future | future use | future use | for future |
| | use | | | use | | | use | | | use |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
Table 8 Table 8: The definitions for "colorspace_type" values.
FFV1 bitstreams with "colorspace_type == 1 && (chroma_planes != 1 || FFV1 bitstreams with "colorspace_type == 1 && (chroma_planes != 1 ||
log2_h_chroma_subsample != 0 || log2_v_chroma_subsample != 0)" are log2_h_chroma_subsample != 0 || log2_v_chroma_subsample != 0)" are
not part of this specification. not part of this specification.
4.2.6. chroma_planes 4.2.6. "chroma_planes"
"chroma_planes" indicates if chroma (color) Planes are present. "chroma_planes" indicates if chroma (color) Planes are present.
+=======+===============================+ +=======+===============================+
| value | presence | | value | presence |
+=======+===============================+ +=======+===============================+
| 0 | chroma Planes are not present | | 0 | chroma Planes are not present |
+-------+-------------------------------+ +-------+-------------------------------+
| 1 | chroma Planes are present | | 1 | chroma Planes are present |
+-------+-------------------------------+ +-------+-------------------------------+
Table 9 Table 9: The definitions for
"chroma_planes" values.
4.2.7. bits_per_raw_sample 4.2.7. "bits_per_raw_sample"
"bits_per_raw_sample" indicates the number of bits for each Sample. "bits_per_raw_sample" indicates the number of bits for each Sample.
Inferred to be 8 if not present. Inferred to be 8 if not present.
+=======+=================================+ +=======+=================================+
| value | bits for each Sample | | value | bits for each Sample |
+=======+=================================+ +=======+=================================+
| 0 | reserved* | | 0 | reserved* |
+-------+---------------------------------+ +-------+---------------------------------+
| Other | the actual bits for each Sample | | Other | the actual bits for each Sample |
+-------+---------------------------------+ +-------+---------------------------------+
Table 10 Table 10: The definitions for
"bits_per_raw_sample" values.
* Encoders MUST NOT store "bits_per_raw_sample = 0". Decoders SHOULD * Encoders MUST NOT store "bits_per_raw_sample = 0". Decoders SHOULD
accept and interpret "bits_per_raw_sample = 0" as 8. accept and interpret "bits_per_raw_sample = 0" as 8.
4.2.8. log2_h_chroma_subsample 4.2.8. "log2_h_chroma_subsample"
"log2_h_chroma_subsample" indicates the subsample factor, stored in "log2_h_chroma_subsample" indicates the subsample factor, stored in
powers to which the number 2 is raised, between luma and chroma width powers to which the number 2 is raised, between luma and chroma width
("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width"). ("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width").
4.2.9. log2_v_chroma_subsample 4.2.9. "log2_v_chroma_subsample"
"log2_v_chroma_subsample" indicates the subsample factor, stored in "log2_v_chroma_subsample" indicates the subsample factor, stored in
powers to which the number 2 is raised, between luma and chroma powers to which the number 2 is raised, between luma and chroma
height ("chroma_height = 2 ^ -log2_v_chroma_subsample * height ("chroma_height = 2 ^ -log2_v_chroma_subsample *
luma_height"). luma_height").
4.2.10. extra_plane 4.2.10. "extra_plane"
"extra_plane" indicates if an extra Plane is present. "extra_plane" indicates if an extra Plane is present.
+=======+============================+ +=======+============================+
| value | presence | | value | presence |
+=======+============================+ +=======+============================+
| 0 | extra Plane is not present | | 0 | extra Plane is not present |
+-------+----------------------------+ +-------+----------------------------+
| 1 | extra Plane is present | | 1 | extra Plane is present |
+-------+----------------------------+ +-------+----------------------------+
Table 11 Table 11: The definitions for
"extra_plane" values.
4.2.11. num_h_slices 4.2.11. "num_h_slices"
"num_h_slices" indicates the number of horizontal elements of the "num_h_slices" indicates the number of horizontal elements of the
slice raster. Slice raster.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.2.12. num_v_slices 4.2.12. "num_v_slices"
"num_v_slices" indicates the number of vertical elements of the slice "num_v_slices" indicates the number of vertical elements of the Slice
raster. raster.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.2.13. quant_table_set_count 4.2.13. "quant_table_set_count"
"quant_table_set_count" indicates the number of Quantization "quant_table_set_count" indicates the number of Quantization
Table Sets. "quant_table_set_count" MUST be less than or equal to 8. Table Sets. "quant_table_set_count" MUST be less than or equal to 8.
Inferred to be 1 if not present. Inferred to be 1 if not present.
MUST NOT be 0. MUST NOT be 0.
4.2.14. states_coded 4.2.14. "states_coded"
"states_coded" indicates if the respective Quantization Table Set has "states_coded" indicates if the respective Quantization Table Set has
the initial states coded. the initial states coded.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+================================+ +=======+================================+
| value | initial states | | value | initial states |
+=======+================================+ +=======+================================+
| 0 | initial states are not present | | 0 | initial states are not present |
| | and are assumed to be all 128 | | | and are assumed to be all 128 |
+-------+--------------------------------+ +-------+--------------------------------+
| 1 | initial states are present | | 1 | initial states are present |
+-------+--------------------------------+ +-------+--------------------------------+
Table 12 Table 12: The definitions for
"states_coded" values.
4.2.15. initial_state_delta 4.2.15. "initial_state_delta"
"initial_state_delta[ i ][ j ][ k ]" indicates the initial Range "initial_state_delta[ i ][ j ][ k ]" indicates the initial range
coder state, and it is encoded using "k" as context index and coder state, and it is encoded using "k" as context index for the
range coder and the following pseudocode:
pred = j ? initial_states[ i ][j - 1][ k ] : 128 pred = j ? initial_states[ i ][j - 1][ k ] : 128
Figure 29 Figure 29: Predictor value for the coding of
"initial_state_delta[ i ][ j ][ k ]".
initial_state[ i ][ j ][ k ] = initial_state[ i ][ j ][ k ] =
( pred + initial_state_delta[ i ][ j ][ k ] ) & 255 ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255
Figure 30 Figure 30: Description of the coding of
"initial_state_delta[ i ][ j ][ k ]".
4.2.16. ec 4.2.16. "ec"
"ec" indicates the error detection/correction type. "ec" indicates the error detection/correction type.
+=======+=================================================+ +=======+=================================================+
| value | error detection/correction type | | value | error detection/correction type |
+=======+=================================================+ +=======+=================================================+
| 0 | 32-bit CRC in "ConfigurationRecord" | | 0 | 32-bit CRC in "ConfigurationRecord" |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" | | 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
Table 13 Table 13: The definitions for "ec" values.
4.2.17. intra 4.2.17. "intra"
"intra" indicates the constraint on "keyframe" in each instance of "intra" indicates the constraint on "keyframe" in each instance of
Frame. Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=======================================================+ +=======+=======================================================+
| value | relationship | | value | relationship |
+=======+=======================================================+ +=======+=======================================================+
| 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) | | 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
| 1 | "keyframe" MUST be 1 (keyframes only) | | 1 | "keyframe" MUST be 1 (keyframes only) |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
Table 14 Table 14: The definitions for "intra" values.
4.3. Configuration Record 4.3. Configuration Record
In the case of a FFV1 bitstream with "version >= 3", a "Configuration In the case of a FFV1 bitstream with "version >= 3", a "Configuration
Record" is stored in the underlying container as described in Record" is stored in the underlying container as described in
Section 4.3.3. It contains the "Parameters" used for all instances Section 4.3.3. It contains the "Parameters" used for all instances
of Frame. The size of the "Configuration Record", "NumBytes", is of Frame. The size of the "Configuration Record", "NumBytes", is
supplied by the underlying container. supplied by the underlying container.
pseudocode | type pseudocode | type
-----------------------------------------------------------|----- -----------------------------------------------------------|-----
ConfigurationRecord( NumBytes ) { | ConfigurationRecord( NumBytes ) { |
ConfigurationRecordIsPresent = 1 | ConfigurationRecordIsPresent = 1 |
Parameters( ) | Parameters( ) |
while (remaining_symbols_in_syntax(NumBytes - 4)) { | while (remaining_symbols_in_syntax(NumBytes - 4)) { |
reserved_for_future_use | br/ur/sr reserved_for_future_use | br/ur/sr
} | } |
configuration_record_crc_parity | u(32) configuration_record_crc_parity | u(32)
} | } |
4.3.1. reserved_for_future_use 4.3.1. "reserved_for_future_use"
"reserved_for_future_use" is a placeholder for future updates of this "reserved_for_future_use" is a placeholder for future updates of this
specification. specification.
Encoders conforming to this version of this specification SHALL NOT Encoders conforming to this version of this specification SHALL NOT
write "reserved_for_future_use". write "reserved_for_future_use".
Decoders conforming to this version of this specification SHALL Decoders conforming to this version of this specification SHALL
ignore "reserved_for_future_use". ignore "reserved_for_future_use".
4.3.2. configuration_record_crc_parity 4.3.2. "configuration_record_crc_parity"
"configuration_record_crc_parity" is 32 bits that are chosen so that "configuration_record_crc_parity" is 32 bits that are chosen so that
the "Configuration Record" as a whole has a CRC remainder of zero. the "Configuration Record" as a whole has a CRC remainder of zero.
This is equivalent to storing the CRC remainder in the 32-bit parity. This is equivalent to storing the CRC remainder in the 32-bit parity.
The CRC generator polynomial used is described in Section 4.9.3. The CRC generator polynomial used is described in Section 4.9.3.
4.3.3. Mapping FFV1 into Containers 4.3.3. Mapping FFV1 into Containers
This "Configuration Record" can be placed in any file format that This "Configuration Record" can be placed in any file format that
supports "Configuration Records", fitting as much as possible with supports "Configuration Records", fitting as much as possible with
how the file format stores "Configuration Records". The how the file format stores "Configuration Records". The
"Configuration Record" storage place and "NumBytes" are currently "Configuration Record" storage place and "NumBytes" are currently
defined and supported for the following formats: defined and supported for the following formats:
4.3.3.1. Audio Video Interleave (AVI) File Format 4.3.3.1. Audio Video Interleave (AVI) File Format
The "Configuration Record" extends the stream format chunk ("AVI", The "Configuration Record" extends the stream format chunk ("AVI ",
"hdlr", "strl", "strf") with the "ConfigurationRecord" bitstream. "hdlr", "strl", "strf") with the "ConfigurationRecord" bitstream.
See [AVI] for more information about chunks. See [AVI] for more information about chunks.
"NumBytes" is defined as the size, in bytes, of the "strf" chunk "NumBytes" is defined as the size, in bytes, of the "strf" chunk
indicated in the chunk header minus the size of the stream format indicated in the chunk header minus the size of the stream format
structure. structure.
4.3.3.2. ISO Base Media File Format 4.3.3.2. ISO Base Media File Format
The "Configuration Record" extends the sample description box The "Configuration Record" extends the sample description box
("moov", "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box ("moov", "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box
that contains the "ConfigurationRecord" bitstream. See that contains the "ConfigurationRecord" bitstream. See
[ISO.14496-12.2015] for more information about boxes. [ISO.14496-12.2020] for more information about boxes.
"NumBytes" is defined as the size, in bytes, of the "glbl" box "NumBytes" is defined as the size, in bytes, of the "glbl" box
indicated in the box header minus the size of the box header. indicated in the box header minus the size of the box header.
4.3.3.3. NUT File Format 4.3.3.3. NUT File Format
The "codec_specific_data" element (in "stream_header" packet) The "codec_specific_data" element (in "stream_header" packet)
contains the "ConfigurationRecord" bitstream. See [NUT] for more contains the "ConfigurationRecord" bitstream. See [NUT] for more
information about elements. information about elements.
skipping to change at line 1838 skipping to change at line 1855
"NumBytes" is defined as the "Element Data Size" of the "NumBytes" is defined as the "Element Data Size" of the
"CodecPrivate" Element. "CodecPrivate" Element.
4.4. Frame 4.4. Frame
A "Frame" is an encoded representation of a complete static image. A "Frame" is an encoded representation of a complete static image.
The whole "Frame" is provided by the underlaying container. The whole "Frame" is provided by the underlaying container.
A "Frame" consists of the "keyframe" field, "Parameters" (if "version A "Frame" consists of the "keyframe" field, "Parameters" (if "version
<= 1"), and a sequence of independent slices. The pseudocode below <= 1"), and a sequence of independent Slices. The pseudocode below
describes the contents of a "Frame". describes the contents of a "Frame".
The "keyframe" field has its own initial state, set to 128. The "keyframe" field has its own initial state, set to 128.
pseudocode | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Frame( NumBytes ) { | Frame( NumBytes ) { |
keyframe | br keyframe | br
if (keyframe && !ConfigurationRecordIsPresent { | if (keyframe && !ConfigurationRecordIsPresent { |
Parameters( ) | Parameters( ) |
} | } |
while (remaining_bits_in_bitstream( NumBytes )) { | while (remaining_bits_in_bitstream( NumBytes )) { |
Slice( ) | Slice( ) |
} | } |
} | } |
The following is an architecture overview of slices in a Frame: The following is an architecture overview of Slices in a Frame:
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| first slice header | | first Slice header |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| first slice content | | first Slice content |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| first slice footer | | first Slice footer |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| --------------------------------------------------------------- | | --------------------------------------------------------------- |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| second slice header | | second Slice header |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| second slice content | | second Slice content |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| second slice footer | | second Slice footer |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| --------------------------------------------------------------- | | --------------------------------------------------------------- |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| ... | | ... |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| --------------------------------------------------------------- | | --------------------------------------------------------------- |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| last slice header | | last Slice header |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| last slice content | | last Slice content |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| last slice footer | | last Slice footer |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
4.5. Slice 4.5. Slice
A "Slice" is an independent, spatial subsection of a Frame that is A "Slice" is an independent, spatial subsection of a Frame that is
encoded separately from another region of the same Frame. The use of encoded separately from another region of the same Frame. The use of
more than one "Slice" per Frame provides opportunities for taking more than one "Slice" per Frame provides opportunities for taking
advantage of multithreaded encoding and decoding. advantage of multithreaded encoding and decoding.
A "Slice" consists of a "Slice Header" (when relevant), a "Slice A "Slice" consists of a "Slice Header" (when relevant), a "Slice
skipping to change at line 1953 skipping to change at line 1970
slice_width - 1 | ur slice_width - 1 | ur
slice_height - 1 | ur slice_height - 1 | ur
for (i = 0; i < quant_table_set_index_count; i++) { | for (i = 0; i < quant_table_set_index_count; i++) { |
quant_table_set_index[ i ] | ur quant_table_set_index[ i ] | ur
} | } |
picture_structure | ur picture_structure | ur
sar_num | ur sar_num | ur
sar_den | ur sar_den | ur
} | } |
4.6.1. slice_x 4.6.1. "slice_x"
"slice_x" indicates the x position on the slice raster formed by "slice_x" indicates the x position on the Slice raster formed by
"num_h_slices". "num_h_slices".
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.2. slice_y 4.6.2. "slice_y"
"slice_y" indicates the y position on the slice raster formed by "slice_y" indicates the y position on the Slice raster formed by
"num_v_slices". "num_v_slices".
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.3. slice_width 4.6.3. "slice_width"
"slice_width" indicates the width on the slice raster formed by "slice_width" indicates the width on the Slice raster formed by
"num_h_slices". "num_h_slices".
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.6.4. slice_height 4.6.4. "slice_height"
"slice_height" indicates the height on the slice raster formed by "slice_height" indicates the height on the Slice raster formed by
"num_v_slices". "num_v_slices".
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.6.5. quant_table_set_index_count 4.6.5. "quant_table_set_index_count"
"quant_table_set_index_count" is defined as the following: "quant_table_set_index_count" is defined as the following:
1 + ( ( chroma_planes || version <= 3 ) ? 1 : 0 ) 1 + ( ( chroma_planes || version <= 3 ) ? 1 : 0 )
+ ( extra_plane ? 1 : 0 ) + ( extra_plane ? 1 : 0 )
4.6.6. quant_table_set_index 4.6.6. "quant_table_set_index"
"quant_table_set_index" indicates the Quantization Table Set index to "quant_table_set_index" indicates the Quantization Table Set index to
select the Quantization Table Set and the initial states for the select the Quantization Table Set and the initial states for the
"Slice Content". "Slice Content".
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.7. picture_structure 4.6.7. "picture_structure"
"picture_structure" specifies the temporal and spatial relationship "picture_structure" specifies the temporal and spatial relationship
of each Line of the Frame. of each Line of the Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=========================+ +=======+=========================+
| value | picture structure used | | value | picture structure used |
+=======+=========================+ +=======+=========================+
| 0 | unknown | | 0 | unknown |
+-------+-------------------------+ +-------+-------------------------+
| 1 | top field first | | 1 | top field first |
+-------+-------------------------+ +-------+-------------------------+
| 2 | bottom field first | | 2 | bottom field first |
+-------+-------------------------+ +-------+-------------------------+
| 3 | progressive | | 3 | progressive |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 15 Table 15: The definitions for
"picture_structure" values.
4.6.8. sar_num 4.6.8. "sar_num"
"sar_num" specifies the Sample aspect ratio numerator. "sar_num" specifies the Sample aspect ratio numerator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if the Sample aspect ratio is unknown. Encoders MUST write 0 if the Sample aspect ratio is unknown.
If "sar_den" is 0, decoders SHOULD ignore the encoded value and If "sar_den" is 0, decoders SHOULD ignore the encoded value and
consider that "sar_num" is 0. consider that "sar_num" is 0.
4.6.9. sar_den 4.6.9. "sar_den"
"sar_den" specifies the Sample aspect ratio denominator. "sar_den" specifies the Sample aspect ratio denominator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if the Sample aspect ratio is unknown. Encoders MUST write 0 if the Sample aspect ratio is unknown.
If "sar_num" is 0, decoders SHOULD ignore the encoded value and If "sar_num" is 0, decoders SHOULD ignore the encoded value and
skipping to change at line 2070 skipping to change at line 2088
} | } |
} else if (colorspace_type == 1) { | } else if (colorspace_type == 1) { |
for (y = 0; y < slice_pixel_height; y++) { | for (y = 0; y < slice_pixel_height; y++) { |
for (p = 0; p < primary_color_count; p++) { | for (p = 0; p < primary_color_count; p++) { |
Line( p, y ) | Line( p, y ) |
} | } |
} | } |
} | } |
} | } |
4.7.1. primary_color_count 4.7.1. "primary_color_count"
"primary_color_count" is defined as the following: "primary_color_count" is defined as the following:
1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 ) 1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 )
4.7.2. plane_pixel_height 4.7.2. "plane_pixel_height"
"plane_pixel_height[ p ]" is the height in pixels of Plane p of the "plane_pixel_height[ p ]" is the height in pixels of Plane p of the
"Slice". It is defined as the following: "Slice". It is defined as the following:
chroma_planes == 1 && (p == 1 || p == 2) chroma_planes == 1 && (p == 1 || p == 2)
? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample)) ? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample))
: slice_pixel_height : slice_pixel_height
4.7.3. slice_pixel_height 4.7.3. "slice_pixel_height"
"slice_pixel_height" is the height in pixels of the slice. It is "slice_pixel_height" is the height in pixels of the Slice. It is
defined as the following: defined as the following:
floor( floor(
( slice_y + slice_height ) ( slice_y + slice_height )
* slice_pixel_height * slice_pixel_height
/ num_v_slices / num_v_slices
) - slice_pixel_y. ) - slice_pixel_y.
4.7.4. slice_pixel_y 4.7.4. "slice_pixel_y"
"slice_pixel_y" is the slice vertical position in pixels. It is "slice_pixel_y" is the Slice vertical position in pixels. It is
defined as the following: defined as the following:
floor( slice_y * frame_pixel_height / num_v_slices ) floor( slice_y * frame_pixel_height / num_v_slices )
4.8. Line 4.8. Line
A "Line" is a list of the sample differences (relative to the A "Line" is a list of the Sample Differences (relative to the
predictor) of primary color components. The pseudocode below predictor) of primary color components. The pseudocode below
describes the contents of the "Line". describes the contents of the "Line".
pseudocode | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Line( p, y ) { | Line( p, y ) { |
if (colorspace_type == 0) { | if (colorspace_type == 0) { |
for (x = 0; x < plane_pixel_width[ p ]; x++) { | for (x = 0; x < plane_pixel_width[ p ]; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} else if (colorspace_type == 1) { | } else if (colorspace_type == 1) { |
for (x = 0; x < slice_pixel_width; x++) { | for (x = 0; x < slice_pixel_width; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} | } |
} | } |
4.8.1. plane_pixel_width 4.8.1. "plane_pixel_width"
"plane_pixel_width[ p ]" is the width in pixels of Plane p of the "plane_pixel_width[ p ]" is the width in pixels of Plane p of the
"Slice". It is defined as the following: "Slice". It is defined as the following:
chroma_planes == 1 && (p == 1 || p == 2) chroma_planes == 1 && (p == 1 || p == 2)
? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) ) ? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) )
: slice_pixel_width. : slice_pixel_width.
4.8.2. slice_pixel_width 4.8.2. "slice_pixel_width"
"slice_pixel_width" is the width in pixels of the slice. It is "slice_pixel_width" is the width in pixels of the Slice. It is
defined as the following: defined as the following:
floor( floor(
( slice_x + slice_width ) ( slice_x + slice_width )
* slice_pixel_width * slice_pixel_width
/ num_h_slices / num_h_slices
) - slice_pixel_x ) - slice_pixel_x
4.8.3. slice_pixel_x 4.8.3. "slice_pixel_x"
"slice_pixel_x" is the slice horizontal position in pixels. It is "slice_pixel_x" is the Slice horizontal position in pixels. It is
defined as the following: defined as the following:
floor( slice_x * frame_pixel_width / num_h_slices ) floor( slice_x * frame_pixel_width / num_h_slices )
4.8.4. sample_difference 4.8.4. "sample_difference"
"sample_difference[ p ][ y ][ x ]" is the sample difference for "sample_difference[ p ][ y ][ x ]" is the Sample Difference for
Sample at Plane "p", y position "y", and x position "x". The Sample Sample at Plane "p", y position "y", and x position "x". The Sample
value is computed based on median predictor and context described in value is computed based on median predictor and context described in
Section 3.2. Section 3.2.
4.9. Slice Footer 4.9. Slice Footer
A "Slice Footer" provides information about slice size and A "Slice Footer" provides information about Slice size and
(optionally) parity. The pseudocode below describes the contents of (optionally) parity. The pseudocode below describes the contents of
the "Slice Footer". the "Slice Footer".
Note: "Slice Footer" is always byte aligned. Note: "Slice Footer" is always byte aligned.
pseudocode | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
SliceFooter( ) { | SliceFooter( ) { |
slice_size | u(24) slice_size | u(24)
if (ec) { | if (ec) { |
error_status | u(8) error_status | u(8)
slice_crc_parity | u(32) slice_crc_parity | u(32)
} | } |
} | } |
4.9.1. slice_size 4.9.1. "slice_size"
"slice_size" indicates the size of the slice in bytes. "slice_size" indicates the size of the Slice in bytes.
Note: this allows finding the start of slices before previous slices Note: this allows finding the start of Slices before previous Slices
have been fully decoded and allows parallel decoding as well as error have been fully decoded and allows parallel decoding as well as error
resilience. resilience.
4.9.2. error_status 4.9.2. "error_status"
"error_status" specifies the error status. "error_status" specifies the error status.
+=======+======================================+ +=======+======================================+
| value | error status | | value | error status |
+=======+======================================+ +=======+======================================+
| 0 | no error | | 0 | no error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| 1 | slice contains a correctable error | | 1 | Slice contains a correctable error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| 2 | slice contains a uncorrectable error | | 2 | Slice contains a uncorrectable error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+--------------------------------------+ +-------+--------------------------------------+
Table 16 Table 16: The definitions for "error_status"
values.
4.9.3. slice_crc_parity 4.9.3. "slice_crc_parity"
"slice_crc_parity" is 32 bits that are chosen so that the slice as a "slice_crc_parity" is 32 bits that are chosen so that the Slice as a
whole has a CRC remainder of 0. whole has a CRC remainder of 0.
This is equivalent to storing the CRC remainder in the 32-bit parity. This is equivalent to storing the CRC remainder in the 32-bit parity.
The CRC generator polynomial used is the standard IEEE CRC polynomial The CRC generator polynomial used is the standard IEEE CRC polynomial
(0x104C11DB7) with initial value 0, without pre-inversion, and (0x104C11DB7) with initial value 0, without pre-inversion, and
without post-inversion. without post-inversion.
5. Restrictions 5. Restrictions
To ensure that fast multithreaded decoding is possible, starting with To ensure that fast multithreaded decoding is possible, starting with
version 3 and if "frame_pixel_width * frame_pixel_height" is more version 3 and if "frame_pixel_width * frame_pixel_height" is more
than 101376, "slice_width * slice_height" MUST be less or equal to than 101376, "slice_width * slice_height" MUST be less or equal to
"num_h_slices * num_v_slices / 4". Note: 101376 is the frame size in "num_h_slices * num_v_slices / 4". Note: 101376 is the frame size in
pixels of a 352x288 frame also known as CIF (Common Intermediate pixels of a 352x288 frame also known as CIF (Common Intermediate
Format) frame size format. Format) frame size format.
For each Frame, each position in the slice raster MUST be filled by For each Frame, each position in the Slice raster MUST be filled by
one and only one slice of the Frame (no missing slice position and no one and only one Slice of the Frame (no missing Slice position and no
slice overlapping). Slice overlapping).
For each Frame with a "keyframe" value of 0, each slice MUST have the For each Frame with a "keyframe" value of 0, each Slice MUST have the
same value of "slice_x", "slice_y", "slice_width", and "slice_height" same value of "slice_x", "slice_y", "slice_width", and "slice_height"
as a slice in the previous Frame. as a Slice in the previous Frame.
6. Security Considerations 6. Security Considerations
Like any other codec (such as [RFC6716]), FFV1 should not be used Like any other codec (such as [RFC6716]), FFV1 should not be used
with insecure ciphers or cipher modes that are vulnerable to known with insecure ciphers or cipher modes that are vulnerable to known
plaintext attacks. Some of the header bits as well as the padding plaintext attacks. Some of the header bits as well as the padding
are easily predictable. are easily predictable.
Implementations of the FFV1 codec need to take appropriate security Implementations of the FFV1 codec need to take appropriate security
considerations into account. Those related to denial of service are considerations into account. Those related to denial of service are
skipping to change at line 2250 skipping to change at line 2269
payloads MUST NOT cause the decoder to overrun its allocated memory payloads MUST NOT cause the decoder to overrun its allocated memory
or to take an excessive amount of resources to decode. An overrun in or to take an excessive amount of resources to decode. An overrun in
allocated memory could lead to arbitrary code execution by an allocated memory could lead to arbitrary code execution by an
attacker. The same applies to the encoder, even though problems in attacker. The same applies to the encoder, even though problems in
encoders are typically rarer. Malicious video streams MUST NOT cause encoders are typically rarer. Malicious video streams MUST NOT cause
the encoder to misbehave because this would allow an attacker to the encoder to misbehave because this would allow an attacker to
attack transcoding gateways. A frequent security problem in image attack transcoding gateways. A frequent security problem in image
and video codecs is failure to check for integer overflows. An and video codecs is failure to check for integer overflows. An
example is allocating "frame_pixel_width * frame_pixel_height" in example is allocating "frame_pixel_width * frame_pixel_height" in
pixel count computations without considering that the multiplication pixel count computations without considering that the multiplication
result may have overflowed the arithmetic types range. The range result may have overflowed the range of the arithmetic type. The
coder could, if implemented naively, read one byte over the end. The range coder could, if implemented naively, read one byte over the
implementation MUST ensure that no read outside allocated and end. The implementation MUST ensure that no read outside allocated
initialized memory occurs. and initialized memory occurs.
None of the content carried in FFV1 is intended to be executable. None of the content carried in FFV1 is intended to be executable.
7. IANA Considerations 7. IANA Considerations
IANA has registered the following values. IANA has registered the following values.
7.1. Media Type Definition 7.1. Media Type Definition
This registration is done using the template defined in [RFC6838] and This registration is done using the template defined in [RFC6838] and
skipping to change at line 2292 skipping to change at line 2311
"coder_type": The "coder_type" of the FFV1 encoding as defined by "coder_type": The "coder_type" of the FFV1 encoding as defined by
Section 4.2.3. Section 4.2.3.
"colorspace_type": The "colorspace_type" of the FFV1 encoding as "colorspace_type": The "colorspace_type" of the FFV1 encoding as
defined by Section 4.2.5. defined by Section 4.2.5.
"bits_per_raw_sample": The "bits_per_raw_sample" of the FFV1 "bits_per_raw_sample": The "bits_per_raw_sample" of the FFV1
encoding as defined by Section 4.2.7. encoding as defined by Section 4.2.7.
"max_slices": The value of "max_slices" is an integer indicating "max_slices": The value of "max_slices" is an integer indicating
the maximum count of slices within a Frame of the FFV1 the maximum count of Slices within a Frame of the FFV1
encoding. encoding.
Encoding considerations: This media type is defined for Encoding considerations: This media type is defined for
encapsulation in several audiovisual container formats and encapsulation in several audiovisual container formats and
contains binary data; see Section 4.3.3. This media type is contains binary data; see Section 4.3.3. This media type is
framed binary data; see Section 4.8 of [RFC6838]. framed binary data; see Section 4.8 of [RFC6838].
Security considerations: See Section 6 of this document. Security considerations: See Section 6 of this document.
Interoperability considerations: None. Interoperability considerations: None.
skipping to change at line 2396 skipping to change at line 2415
[HuffYUV] Rudiak-Gould, B., "HuffYUV revisited", December 2003, [HuffYUV] Rudiak-Gould, B., "HuffYUV revisited", December 2003,
<https://web.archive.org/web/20040402121343/ <https://web.archive.org/web/20040402121343/
http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>. http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.
[ISO.14495-1.1999] [ISO.14495-1.1999]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Lossless and near-lossless "Information technology -- Lossless and near-lossless
compression of continuous-tone still images: Baseline", compression of continuous-tone still images: Baseline",
ISO/IEC 14495-1:1999, December 1999. ISO/IEC 14495-1:1999, December 1999.
[ISO.14496-10.2014] [ISO.14496-10.2020]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Coding of audio-visual objects "Information technology -- Coding of audio-visual objects
-- Part 10: Advanced Video Coding", ISO/IEC 14496-10:2020, -- Part 10: Advanced Video Coding", ISO/IEC 14496-10:2020,
September 2014. December 2020.
[ISO.14496-12.2015] [ISO.14496-12.2020]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Coding of audio-visual objects "Information technology -- Coding of audio-visual objects
-- Part 12: ISO base media file format", ISO/IEC -- Part 12: ISO base media file format", ISO/IEC
14496-12:2015, December 2015. 14496-12:2020, December 2020.
[ISO.15444-1.2016] [ISO.15444-1.2019]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- JPEG 2000 image coding system: "Information technology -- JPEG 2000 image coding system:
Core coding system", ISO/IEC 15444-1:2016, October 2016. Core coding system", ISO/IEC 15444-1:2019, October 2019.
[Matroska] Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media [Matroska] Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
Container Format Specifications", Work in Progress, Container Format Specifications", Work in Progress,
Internet-Draft, draft-ietf-cellar-matroska-07, 12 April Internet-Draft, draft-ietf-cellar-matroska-07, 12 April
2021, <https://tools.ietf.org/html/draft-ietf-cellar- 2021, <https://datatracker.ietf.org/doc/html/draft-ietf-
matroska-07>. cellar-matroska-07>.
[MediaConch] [MediaConch]
MediaArea.net, "MediaConch", 2018, MediaArea.net, "MediaConch", 2018,
<https://mediaarea.net/MediaConch>. <https://mediaarea.net/MediaConch>.
[NUT] Niedermayer, M., "NUT Open Container Format", December [NUT] Niedermayer, M., "NUT Open Container Format", December
2013, <https://ffmpeg.org/~michael/nut.txt>. 2013, <https://ffmpeg.org/~michael/nut.txt>.
[Range-Encoding] [Range-Encoding]
Martin, G. N. N., "Range encoding: an algorithm for Martin, G. N. N., "Range encoding: an algorithm for
removing redundancy from a digitised message", Proceedings removing redundancy from a digitised message", Proceedings
of the Conference on Video and Data Recording, Institution of the Conference on Video and Data Recording, Institution
of Electronic and Radio Engineers, Hampshire, England, of Electronic and Radio Engineers, Hampshire, England,
July 1979. July 1979.
[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
FFV1 codec in FFmpeg", <https://ffmpeg.org>. FFV1 codec in FFmpeg",
<https://ffmpeg.org/doxygen/trunk/ffv1_8h.html>.
[RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the
Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716, Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
September 2012, <https://www.rfc-editor.org/info/rfc6716>. September 2012, <https://www.rfc-editor.org/info/rfc6716>.
[Valgrind] Valgrind Developers, "Valgrind website", [Valgrind] Valgrind Developers, "Valgrind website",
<https://valgrind.org/>. <https://valgrind.org/>.
[YCbCr] Wikipedia, "YCbCr", 25 May 2021, [YCbCr] Wikipedia, "YCbCr", 25 May 2021,
<https://en.wikipedia.org/w/ <https://en.wikipedia.org/w/
index.php?title=YCbCr&oldid=1025097882>. index.php?title=YCbCr&oldid=1025097882>.
Appendix A. Multithreaded Decoder Implementation Suggestions Appendix A. Multithreaded Decoder Implementation Suggestions
This appendix is informative. This appendix is informative.
The FFV1 bitstream is parsable in two ways: in sequential order as The FFV1 bitstream is parsable in two ways: in sequential order as
described in this document or with the pre-analysis of the footer of described in this document or with the pre-analysis of the footer of
each slice. Each slice footer contains a "slice_size" field so the each Slice. Each Slice footer contains a "slice_size" field so the
boundary of each slice is computable without having to parse the boundary of each Slice is computable without having to parse the
slice content. That allows multithreading as well as independence of Slice content. That allows multithreading as well as independence of
slice content (a bitstream error in a slice header or slice content Slice content (a bitstream error in a Slice header or Slice content
has no impact on the decoding of the other slices). has no impact on the decoding of the other Slices).
After having checked the "keyframe" field, a decoder SHOULD parse After having checked the "keyframe" field, a decoder SHOULD parse
"slice_size" fields, from "slice_size" of the last slice at the end "slice_size" fields, from "slice_size" of the last Slice at the end
of the "Frame" up to "slice_size" of the first slice at the beginning of the "Frame" up to "slice_size" of the first Slice at the beginning
of the "Frame" before parsing slices, in order to have slice of the "Frame" before parsing Slices, in order to have Slice
boundaries. A decoder MAY fall back on sequential order e.g., in boundaries. A decoder MAY fall back on sequential order e.g., in
case of a corrupted "Frame" (e.g., frame size unknown or "slice_size" case of a corrupted "Frame" (e.g., frame size unknown or "slice_size"
of slices not coherent) or if there is no possibility of seeking into of Slices not coherent) or if there is no possibility of seeking into
the stream. the stream.
Appendix B. Future Handling of Some Streams Created by Nonconforming Appendix B. Future Handling of Some Streams Created by Nonconforming
Encoders Encoders
This appendix is informative. This appendix is informative.
Some bitstreams were found with 40 extra bits corresponding to Some bitstreams were found with 40 extra bits corresponding to
"error_status" and "slice_crc_parity" in the "reserved" bits of "error_status" and "slice_crc_parity" in the "reserved" bits of
"Slice". Any revision of this specification SHOULD care about "Slice". Any revision of this specification should avoid adding 40
avoiding the addition of 40 bits of content after "SliceContent" if bits of content after "SliceContent" if "version == 0" or "version ==
"version == 0" or "version == 1", otherwise a decoder conforming to 1", otherwise a decoder conforming to the revised specification could
the revised specification could not distinguish between a revised not distinguish between a revised bitstream and such buggy bitstream
bitstream and such buggy bitstream in the wild. in the wild.
Appendix C. FFV1 Implementations Appendix C. FFV1 Implementations
This appendix provides references to a few notable implementations of This appendix provides references to a few notable implementations of
FFV1. FFV1.
C.1. FFmpeg FFV1 Codec C.1. FFmpeg FFV1 Codec
This reference implementation [REFIMPL] contains no known buffer This reference implementation [REFIMPL] contains no known buffer
overflow or cases where a specially crafted packet or video segment overflow or cases where a specially crafted packet or video segment
skipping to change at line 2520 skipping to change at line 2540
C.2. FFV1 Decoder in Go C.2. FFV1 Decoder in Go
An FFV1 decoder [FFV1GO] was written in Go by Derek Buitenhuis during An FFV1 decoder [FFV1GO] was written in Go by Derek Buitenhuis during
the work to develop this document. the work to develop this document.
C.3. MediaConch C.3. MediaConch
The developers of the MediaConch project [MediaConch] created an The developers of the MediaConch project [MediaConch] created an
independent FFV1 decoder as part of that project to validate FFV1 independent FFV1 decoder as part of that project to validate FFV1
bitstreams. This work led to the discovery of three conflicts bitstreams. This work led to the discovery of three conflicts
between existing FFV1 implementations and this document without the between existing FFV1 implementations and draft versions of this
added exceptions. document. These issues are addressed by Section 3.3.1,
Section 3.7.2.1, and Appendix B.
Authors' Addresses Authors' Addresses
Michael Niedermayer Michael Niedermayer
Email: michael@niedermayer.cc Email: michael@niedermayer.cc
Dave Rice Dave Rice
Email: dave@dericed.com Email: dave@dericed.com
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