wdiff rfc7294.original rfc7294.txt

Audio/Video Transport Working Group
Internet Engineering Task Force (IETF) A. Clark
Internet-Draft
Request for Comments: 7294 Telchemy
Intended status:
Category: Standards Track G. Zorn
Expires: October 13, 2014
ISSN: 2070-1721 Network Zen
C. Bi
STTRI
Q. Wu, Ed. Wu
Huawei
April 11,
July 2014

RTCP XR

RTP Control Protocol (RTCP) Extended Report Block (XR) Blocks for Concealment metrics
Metrics Reporting on Audio Applications
draft-ietf-xrblock-rtcp-xr-loss-conceal-12.txt

Abstract

This document defines two RTCP XR RTP Control Protocol (RTCP) Extended Report Blocks
(XR) blocks that allows allow the reporting of concealment metrics for audio
applications of RTP.

Status of this This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on October 13, 2014.
http://www.rfc-editor.org/info/rfc7294.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2
1.1. Loss Concealment and Concealment Concealed Seconds Metrics
Reporting Block
Blocks . . . . . . . . . . . . . . . . . . . . . 3 . . . . 2
1.2. RTCP and RTCP XR Extended Reports . . . . . . . . . . . . . . . . . 4 3
1.3. Performance Metrics Framework . . . . . . . . . . . . . . 4 3
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4
2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 4
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 5 4
3. Loss Concealment Metrics Block . . . . . . . . . . . . . . . . . . . . 6 5
3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 5
3.2. Definition of Fields in Loss Concealment Metrics Block . . 6 5
4. Concealment Concealed Seconds Metrics Block . . . . . . . . . . . . . . . . . . 11 9
4.1. Report Block Structure . . . . . . . . . . . . . . . . . . 11 9
4.2. Definition of Fields in Concealed Seconds Metrics Block . 12 10
5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 16 14
5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 16 14
5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 16 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 14
6.1. New RTCP XR Block Type values Values . . . . . . . . . . . . . . 17 14
6.2. New RTCP XR SDP Parameters . . . . . . . . . . . . . . . . 17 15
6.3. Contact information Information for registrations Registrations . . . . . . . . . . 17 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 15
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 21 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 21 16
Appendix A. Metrics represented using RFC6390 Represented Using the Template . . . . . 22
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 29
B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-11 . . . . . . . . 29
B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-09 . . . . . . . . 29
B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-07 . . . . . . . . 29
B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-06 . . . . . . . . 29
B.5. draft-ietf-xrblock-rtcp-xr-loss-conceal-05 . . . . . . . . 29
B.6. draft-ietf-xrblock-rtcp-xr-loss-conceal-04 . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 from RFC 6390 17

1. Introduction

1.1. Loss Concealment and Concealment Concealed Seconds Metrics Reporting Block Blocks

At any instant, the audio output at a receiver may be classified as
either 'normal' or 'concealed'. 'Normal' refers to playout of audio
payload received from the remote end, end and also includes locally
generated signals such as announcements, tones tones, and comfort noise.
Concealment
'Concealed' refers to playout of locally-generated locally generated signals used to
mask the impact of network impairments or to reduce the audibility of
jitter buffer adaptations.

This draft document defines two new concealment related concealment-related block types to
augment those defined in [RFC3611] for use in a range of RTP
applications. These two block types extend the packet loss
concealment mechanism defined in section Section 4.7.6 of RFC3611. [RFC3611].

The first block type type, the Loss Concealment Metrics Block, provides
metrics for actions taken by the receiver to mitigate the effect of
packet loss and packet discard. Specifically, the first metric (On-Time (On-
Time Playout Duration) reports the duration of normal playout of data which
that the receiver obtained from the sender's stream. A second metric
(Loss Concealment Duration) reports the total time during which the
receiver played out media data which that was manufactured locally, because
the sender's data for these periods was not available due to packet
loss or discard. A similar metric (Buffer Adjustment Concealment
Duration) reports the duration of playout of locally-manufactured locally manufactured
data replacing data which that is unavailable due to adaptation of an
adaptive de-jitter buffer. Further metrics (Playout Interrupt Count
and Mean Playout Interrupt Size) report the number of times normal
playout was interrupted, interrupted and the mean duration of these interruptions.

Loss Concealment Duration and Buffer Adjustment Concealment Duration
are reported separately because buffer adjustment is typically
arranged to occur in silence periods periods, so it may have very little
impact on user experience, whilst loss concealment may occur at any
time.

The second block type type, the Concealed Seconds Metrics Block, provides
metrics for concealment seconds, Concealed Seconds, which are measured at the receiving
end of the RTP stream. Specifically, the first metric (Unimpaired
Seconds) reports the number of whole seconds occupied only with
normal playout of data which that the receiver obtained from the sender's
stream. The second metric (Concealed Seconds) reports the number of
whole seconds during which the receiver played out any locally-generated locally
generated media data. A third metric, Severely Concealed Seconds (SCS),
(SCSs), reports the number of whole seconds during which the receiver
played out locally-generated locally generated data
for more than to conceal a lost or discarded
frame percentage in excess of the configured SCS Threshold.

These metrics belongs to the class of transport-related terminal
metrics defined in [RFC6792].

1.2. RTCP and RTCP XR Extended Reports

The use of RTCP for reporting is defined in [RFC3550]. [RFC3611]
defined
defines an extensible structure for reporting using an RTCP Extended
Report (XR). This draft document defines a new Extended Report block that
MUST be used as defined in [RFC3550] and [RFC3611].

1.3. Performance Metrics Framework

The Performance Metrics Framework [RFC6390] provides guidance on the
definition and specification of performance metrics. The RTP
Monitoring Architectures Framework [RFC6792] provides guideline guidelines for reporting
block format using RTCP XR. The Metrics Block metrics blocks described in this
document are in accordance with those guidelines.

1.4. Applicability

These metrics are applicable to audio applications of RTP and the
audio component of Audio/Video audio/video applications in which the packet loss
concealment machinery is contained at the receiving end to mitigate
the impact of network impairments to user's perception of media
quality.

2. Terminology

2.1. Standards Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 RFC 2119 [RFC2119].

2.2. Notations

This

The report block makes blocks in this document make use of binary fractions. The
following terminology
used is used:

Numeric formats S X:Y

where S indicates a two's complement signed representation, X
the number of bits prior to the decimal place place, and Y the number
of bits after the decimal place.

Hence

Hence, 8:8 represents an unsigned number in the range 0.0 to
255.996 with a granularity of 0.0039. S7:8 would represent the
range -127.996 to +127.996. 0:16 represents a proper binary
fraction with range

0.0 to 1 - 1/65536 = 0.9999847

though note that use of flag values at the top of the numeric
range slightly reduces this upper limit. For example, if the
16- bit
16-bit values 0xfffe and 0xffff are used as flags for "over-
range" and "unavailable" conditions, a 0:16 quantity has range

0.0 to 1 - 3/65536 = 0.9999542

3. Loss Concealment Metrics Block

The metrics block described here are Loss Concealment Metrics Block is intended to be used as
described in this section, in conjunction with information from the
Measurement Information block Block [RFC6776]. Instances of this Metrics Block metrics
block refer by Synchronization synchronization source (SSRC) to the separate
auxiliary Measurement Information block [RFC6776] Block [RFC6776], which describes
measurement periods in use (see [RFC6776] section [RFC6776], Section 4.2). This Metrics Block
metrics block relies on the measurement period in the Measurement
Information block Block indicating the span of the report and SHOULD be
sent in the same compound RTCP packet as the measurement information block. Measurement Information
Block. If the measurement period is not received in the same
compound RTCP packet as this Metrics Block, metrics block, this metrics block MUST
be discarded.

3.1. Report Block Structure

The structure of the Loss Concealment Metrics Block is as follows.

0 1 2 3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=NLC BT=30 | I |plc| rsv. resv | block length=6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| On-time On-Time Playout Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loss Concealment Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Buffer Adjustment Concealment Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Playout Interrupt Count | Reserved. Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mean Playout Interrupt Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: Report Loss Concealment Metrics Block Structure

3.2. Definition of Fields in Loss Concealment Metrics Block

Block type (BT): 8 bits

A Loss Concealment Metrics Report Block is identified by the constant NLC.

[Note to RFC Editor: please replace NLC with the IANA provided
RTCP XR block type for this block.] 30.

Interval Metric flag (I): 2 bit bits
This field is used to indicate whether the Loss Concealment loss concealment
metrics are Sampled, Interval Interval, or Cumulative metrics:

I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive
metrics reports.

I=11: Cumulative Duration - the reported value applies to the
accumulation period characteristic of cumulative measurements.

I=01: Sampled Value - the reported value is a sampled
instantaneous value ( Not (not allowed in this block).

I=00: Reserved value- value - this value is reserved for future use.

In this document, Loss Concealment Metrics metrics can only be measured
over definite intervals, intervals and cannot be sampled. Senders MUST NOT
use the values I=00 or I=01. If a block is received with I=00 or
I=01, the receiver MUST discard the block.

Packet Loss Concealment Method (plc): 2 bits

This field is used to identify the packet loss concealment method
in use at the receiver, according to the following code:

bits 014-015

0 = silence insertion

1 = simple replay, no attenuation

2 = simple replay, with attenuation

3 = enhancement

Other values reserved are reserved.

Note that the enhancement method (plc =3 ) (plc=3) for packet loss
concealment offers an improved audio quality and a better robustness
against packet losses [G.711] and is equivalent to
enhanced "enhanced" in section
Section 4.7.6 of [RFC3611].

Reserved (resv): 4 bits

These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See [RFC6709] section (see [RFC6709], Section 4.2).

block length: 16 bits
The length of this report block in 32-bit words, minus one. For
the Loss Concealment Metrics Block, the block length is equal to
6.

SSRC of source: Source: 32 bits

As defined in Section 4.1 of [RFC3611].

On-time

On-Time Playout Duration: 32 bits

'On-time' playout

'On-time playout' is the uninterrupted, in-sequence playout of
valid decoded audio information originating from the remote
endpoint. This includes comfort noise during periods of remote
talker silence, if VAD Voice Activity Detection (VAD) [VAD] is used,
and locally generated or regenerated tones and announcements.

An equivalent definition is that on-time playout is playout of any
signal other than those used for concealment.

On-time playout duration is expressed in units of RTP timestamp
and MUST include both speech and silence intervals, whether VAD is
used or not.

Two values are reserved: A a value of 0xFFFFFFFE indicates out of
range (that is, a measured value exceeding 0xFFFFFFFD) 0xFFFFFFFD), and a
value of 0xFFFFFFFF indicates that the measurement is unavailable.

Loss Concealment Duration: 32 bits

The duration, expressed in units of RTP timestamp, of audio
playout corresponding to Loss-type Loss-Type concealment.

Loss-type

Loss-Type concealment is reactive insertion or deletion of samples
in the audio playout stream due to effective frame loss at the
audio decoder. "Effective Effective frame loss" loss is the event in which a frame
of coded audio is simply not present at the audio decoder when
required. In this case, substitute audio samples are generally
formed, at the decoder or elsewhere, to reduce audible impairment.

Buffer Adjustment Concealment Duration: 32 bits

The duration, expressed in units of RTP timestamp, of audio
playout corresponding to Buffer Adjustment-type Adjustment-Type concealment, if
known.

Buffer Adjustment-type Adjustment-Type concealment is proactive or controlled
insertion or deletion of samples in the audio playout stream due
to jitter buffer adaptation, re-sizing decisions, or re-centering
decisions within the endpoint.

Because this insertion is controlled, rather than occurring
randomly in response to losses, it is typically less audible than
loss-type
Loss-Type concealment. For example, jitter buffer adaptation
events may be constrained to occur during periods of talker
silence, in which case only silence duration is affected, or
sophisticated time-stretching methods for insertion/deletion
during favorable periods in active speech may be employed.

Concealment events which that cannot be classified as Buffer
Adjustment-type Adjustment-
Type MUST be classified as Loss-type. Loss-Type.

Playout Interrupt Count: 16 bits

The number of interruptions to normal playout which that occurred during
the reporting period.

Two values are reserved: A a value of 0xFFFE indicates out of range
(that is, a measured value exceeding 0xFFFD) 0xFFFD), and a value of
0xFFFF indicates that the measurement is unavailable.

Reserved (resv):

Reserved: 16 bits

These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See [RFC6709] section (see [RFC6709], Section 4.2).

Mean Playout Interrupt Size: 32 bits

The mean duration, expressed in units of RTP timestamp, of
interruptions to normal playout which that occurred during the reporting
period.

4. Concealment Concealed Seconds Metrics Block

The Concealed Seconds Metrics Block

This sub-block described here is intended to be used as
described in this section, in conjunction with information from the
Measurement Information block [RFC6776] and Block [RFC6776]. It provides a description
of potentially audible impairments due to lost and discarded packets
at the endpoint, expressed on a time basis analogous to a traditional PSTN
Public Switched Telephone Network (PSTN) T1/E1 errored seconds
metric. Instances of this Metrics Block metrics block refer by Synchronization synchronization
source (SSRC) to the separate auxiliary Measurement Information block Block
[RFC6776] which that describes measurement periods in use (see [RFC6776] section [RFC6776],
Section 4.2). This Metrics Block metrics block relies on the measurement period in
the Measurement Information block Block indicating the span of the report
and SHOULD be sent in the same compound RTCP packet as the measurement information block.
Measurement Information Block. If the measurement period is not
received in the same compound RTCP packet as this Metrics Block, metrics block, this
metrics block MUST be discarded.

The following metrics are based on successive one second one-second intervals as
declared by a an RTP clock. This RTP clock does not need to be
synchronized to any external time reference. The starting time of
this clock is unspecified. Note that this implies that the same loss
pattern could result in slightly different count values, depending on
where the losses occur relative to the particular one-second
demarcation points. For example, two loss events occurring 50ms 50 ms
apart could result in either one concealed second Concealed Second or two, depending
on the particular one second one-second boundaries used.

The seconds in this sub-block are not necessarily calendar seconds.
At the tail end of a session, periods of time of less than one second
shall be incorporated into these counts if they exceed 500ms 500 ms and
shall be disregarded if they are less than 500ms. 500 ms.

4.1. Report Block Structure

The structure of the Concealed Seconds Metrics Block is as follows.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=NCS BT=31 | I |plc|Rserved| |plc| resv | block length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unimpaired Seconds |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Concealed Seconds |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Severely Concealed Seconds | RESERVED Reserved | SCS Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: Report Concealed Seconds Metrics Block Structure

4.2. Definition of Fields in Concealed Seconds Metrics Block

Block type (BT): 8 bits

A Concealed Seconds Metrics Report Block is identified by the constant NCS.

[Note to RFC Editor: please replace NCS with the IANA provided
RTCP XR block type for this block.]
31.

Interval Metric flag (I): 2 bit bits

This field is used to indicate whether the Concealment Concealed Seconds
Metrics
metrics are Sampled, Interval Interval, or Cumulative metrics:

I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive
metrics reports.

I=11: Cumulative Duration - the reported value applies to the
accumulation period characteristic of cumulative measurements.

I=01: Sampled Value - the reported value is a sampled
instantaneous value (Not allowed in this block).

I=00: Reserved value- value - this value is reserved for future use.

In this document, Concealment Concealed Seconds Metrics metrics can only be measured
over definite intervals, intervals and cannot be sampled. Senders MUST NOT
use the values I=00 or I=01. If a block is received with I=00 or
I=01, the receiver MUST discard the block.

Packet Loss Concealment Method (plc): 2 bits
This field is used to identify the packet loss concealment method
in use at the receiver, according to the following code:

bits 014-015

0 = silence insertion

1 = simple replay, no attenuation

2 = simple replay, with attenuation

3 = enhancement

Other values reserved are reserved.

Note that the enhancement method (plc =3 ) (plc=3) for packet loss
concealment offers an improved audio quality and a better
robustness against packet losses [G.711] and is equivalent to
enhanced
"enhanced" in section Section 4.7.6 of [RFC3611].

Reserved (resv): 4 bits

These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See [RFC6709] section (see [RFC6709], Section 4.2).

Block Length: 16 bits

The length of this report block in 32-bit words, minus one. For
the Concealment Concealed Seconds Metrics Block, the block length is equal to
4.

SSRC of source: Source: 32 bits

As defined in Section 4.1 of [RFC3611].

Unimpaired Seconds: 32 bits

A count of the number of unimpaired Unimpaired Seconds that have occurred.

An unimpaired Unimpaired Second is defined as a continuous period of one
second during which no frame loss or discard due to late arrival
has occurred. Every second in a session must be classified as
either OK or Concealed.

Normal playout of comfort noise or other silence concealment
signal silence-concealment
signals during periods of talker silence, if VAD is used, shall be
counted as unimpaired seconds. Unimpaired Seconds.

Concealed Seconds: 32 bits

A count of the number of Concealed Seconds that have occurred.

A Concealed Second is defined as a continuous period of one second
during which any frame loss or discard due to late arrival has
occurred.

Equivalently, a concealed second Concealed Second is one in which some Loss-type Loss-Type
concealment has occurred. Buffer adjustment-type Adjustment-Type concealment
SHOULD NOT cause Concealed Seconds to be incremented, with the
following exception. An implementation MAY cause Concealed
Seconds to be incremented for 'emergency' buffer adjustments made
during talkspurts.

Loss-type

Loss-Type concealment is reactive insertion or deletion of samples
in the audio playout stream due to effective frame loss at the
audio decoder. "Effective frame loss" is the event in which a
frame of coded audio is simply not present at the audio decoder
when required. In this case, substitute audio samples are
generally formed, at the decoder or elsewhere, to reduce audible
impairment.

However, an implementation SHOULD include buffer-type Buffer Adjustment-Type
concealment in counts of Concealed Seconds and Severely Concealed
Seconds if the event occurs at an 'inopportune' moment, with such as an
emergency or large, immediate adaptation during active speech, speech or for
an unsophisticated adaptation during speech without regard for the
underlying signal, in which cases signal. In these cases, the assumption of low-audibility low
audibility cannot hold. In other words, jitter buffer adaptation
events
which that may be presumed to be audible SHOULD be included in
Concealed Seconds and Severely Concealed Seconds counts.

Concealment events which that cannot be classified as Buffer Adjustment- type
Type MUST be classified as Loss-type. Loss-Type.

For clarification, the count of Concealed Seconds MUST include the
count of Severely Concealed Seconds.

Severely Concealed Seconds: 16 bits

A count of the number of Severely Concealed Seconds.

A Severely Concealed Second is defined as a non-overlapping period
of one second during which the cumulative amount of time that has
been subject to frame loss or discard due to late arrival, arrival exceeds
the SCS Threshold.

Two values are reserved: A a value of 0xFFFE indicates out of range
(that is, a measured value exceeding 0xFFFD) 0xFFFD), and a value of
0xFFFF indicates that the measurement is unavailable.

Reserved: 8 bits

These bits are reserved. They MUST be set to zero by senders and
ignored by receivers (See [RFC6709] section (see [RFC6709], Section 4.2).

SCS Threshold: 8 bits

The SCS Threshold is defined as the percentage of packets
corresponding to lost or discarded frames that must occur within a
one second period in order for the second to be classified as a
Severely Concealed Second. This is expressed in numeric format
0:8 and hence can represent a range of 0 to 99.6 percent loss or
discard.

A default threshold of 5% 5 percent effective frame loss (50ms (50 ms
effective frame loss ) per second is suggested. This corresponds
to an SCS Threshold in hexadecimal of 0x0D.

5. SDP Signaling

[RFC3611] defines the use of SDP (Session Description Protocol)
[RFC4566] for signaling the use of XR blocks. XR blocks MAY be used
without prior signaling.

5.1. SDP rtcp-xr-attrib Attribute Extension

This section augments the SDP attribute "rtcp-xr" [RFC3611] by
providing two additional values of "xr-format" to signal the use of
the two report blocks defined in this document.

xr-format =/ xr-conceal-block
/ xr-conc-sec-block

xr-conceal-block = "loss-conceal"
xr-conc-sec-block = "conc-sec" ["=" thresh]

thresh = 1*DIGIT ; threshold for SCS (ms)
DIGIT = <as defined in Section 3 of [RFC5234]>

5.2. Offer/Answer Usage

When SDP is used in offer-answer Offer/Answer context, the SDP Offer/Answer usage
defined in [RFC3611] applies. Note that "thresh" is declared by the
offer.

6. IANA Considerations

New block types for RTCP XR are subject to IANA registration. For
general guidelines on IANA considerations for RTCP XR, refer to
[RFC3611].

6.1. New RTCP XR Block Type values Values

This document assigns two block type values in the IANA "RTP Control
Protocol Extended Reports (RTCP XR) Block Type Registry ": Registry" under the
subregistry "RTCP XR Block Type":

Name: LCB
Long Name: Loss Concealment Metrics Block
Value <NLC> 30
Reference: Section 3.1

Name: CSB
Long Name: Concealment Concealed Seconds Metrics Block
Value <NCS> 31
Reference: Section 4.1

[Note to RFC Editor: please replace <NLC> and <NCS> with the RTCP XR
block type assigned by IANA for this block.]

6.2. New RTCP XR SDP Parameters

This document also registers two new parameters in the "RTP Control
Protocol Extended Reports (RTCP XR) Session Description Protocol
(SDP) Parameters Registry":

o "loss-conceal"

o "conc-sec"

6.3. Contact information Information for registrations Registrations

The contact information for the registrations is:

RAI Area Directors

rai-ads@tools.ietf.org

7. Security Considerations

It is believed that this proposed the RTCP XR report block introduces blocks defined in this document
introduce no new security considerations beyond those described in
[RFC3611].
This block does These blocks do not provide per-packet statistics statistics, so the
risk to confidentiality documented in Section 7, paragraph Paragraph 3 of
[RFC3611] does not apply.

8. Contributors

Geoff Hunt wrote the initial draft version of this document.

9. Acknowledgements

The authors gratefully acknowledge reviews and feedback provided by
Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor,
Alissa Cooper, Claus Dahm, Randy Ethier, Roni Even, Adrian Farrel,
Jim Frauenthal, Albert Higashi, Tom Hock, Shane Holthaus, Paul Jones,
Rajesh Kumar, Keith Lantz, Alfred C. Morton, Mohamed Mostafa, Amy
Pendleton, Colin Perkins, Mike Ramalho, Ravi Raviraj, Pete Resnick,
Albrecht Schwarz, Meral Shirazipour, Tom Taylor, Hideaki Yamada ,Alissa
Cooper,Meral Shirazipour and ,MORTON, ALFRED C (AL),Adrian Farrel and
Pete Resnick. Hideaki Yamada.

10. References

10.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.

[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611, November
2003.

[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.

[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.

[RFC6776] Clark, A. and Q. Wu, Q., "Measurement Identity and information Information
Reporting
using SDES item Using a Source Description (SDES) Item and XR an
RTCP Extended Report (XR) Block", RFC 6776, August October 2012.

10.2. Informative References

[G.711] ITU-T, "Pulse Code Modulation (PCM) of Voice Frequencies",
ITU-T Recommendation G.711, 1988.

[RFC6390] Clark, A. and B. Claise, "Framework "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
October 2011.

[RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design
Considerations for Protocol Extensions", RFC 6709,
September 2012.

[RFC6792] Wu, Q., Hunt, G., "Monitoring Architectures and P. Arden, "Guidelines for RTP", Use of the
RTP Monitoring Framework", RFC 6792, November 2012.

[VAD] "http://en.wikipedia.org/wiki/Voice_activity_detection". Wikipedia, "Voice activity detection", January 2014,
<http://en.wikipedia.org/w/
index.php?title=Voice_activity_detection&oldid=593287643>.

Appendix A. Metrics represented using RFC6390 Template

RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by Represented Using the new Template from RFC
number, when assigned. 6390

a. On-time On-Time Playout Duration Metric

* Metric Name: On-time On-Time Playout Duration

* Metric Description: 'On-time' playout 'On-time playout' is the uninterrupted,
in-sequence playout of valid decoded audio information
originating from the remote endpoint. On-time playout
Duration
duration is playout duration of any signal other than those
used for concealment concealment.

* Method of Measurement or Calculation: See section 3. 2, On-
time Playout Section 3.2, On-Time
Playout Duration definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 3.2, On-time On-Time Playout
Duration definition [RFCXXXX]. definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 3rd paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 3, 1st paragraph [RFCXXXX] for
measurement timing and section Section 3.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

b. Loss Concealment Duration Metric

* Metric Name: Loss Concealment Duration

* Metric Description: The duration of audio playout
corresponding to Loss-type Loss-Type concealment.

* Method of Measurement or Calculation: See section Section 3.2, Loss
Concealment Duration definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 3.2, Loss Concealment
Duration definition [RFCXXXX]. definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 3rd paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 3, 1st paragraph [RFCXXXX] for
measurement timing and section 3. 2 [RFCXXXX] Section 3.2 for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

c. Buffer Adjustment Concealment Duration Metric

* Metric Name: Buffer Adjustment Concealment Duration

* Metric Description: The duration of audio playout
corresponding to Buffer Adjustment-type Adjustment-Type concealment.

* Method of Measurement or Calculation: See section 3. 2, Section 3.2, Buffer
Adjustment Concealment Duration definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 3.2, Buffer Adjustment
Concealment Duration definition [RFCXXXX]. definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 3rd paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 3, 1st paragraph [RFCXXXX] for
measurement timing and section Section 3.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

d. Playout Interrupt Count Metric

* Metric Name: Playout Interrupt Count

* Metric Description: The number of interruptions to normal
playout which that occurred during the reporting period.

* Method of Measurement or Calculation: See section 3. 2, Section 3.2, Playout
Interrupt Count definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 3.2, Playout Interrupt Count
definition [RFCXXXX].
definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 3rd paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 3, 1st paragraph [RFCXXXX] for
measurement timing and section Section 3.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

e. Mean Playout Interrupt Size Metric

* Metric Name: Mean Playout Interrupt Size

* Metric Description: The mean duration of interruptions to
normal playout which that occurred during the reporting period.

* Method of Measurement or Calculation: See section 3. 2, Section 3.2, Playout
Interrupt Count definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 3.2, Playout Interrupt Count
definition [RFCXXXX].
definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 3rd paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 3, 1st paragraph [RFCXXXX] for
measurement timing and section Section 3.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

f. Unimpaired Seconds Metric

* Metric Name: Unimpaired Seconds

* Metric Description: A count of the number of unimpaired Unimpaired
Seconds that have occurred.

* Method of Measurement or Calculation: See section 4. 2, Section 4.2,
Unimpaired Seconds definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 4.2, Unimpaired Seconds
definition [RFCXXXX].
definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 5th paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 4, 1st paragraph [RFCXXXX] for
measurement timing and section Section 4.2 paragraph [RFCXXXX] for Interval
Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

g. Concealed Seconds Metric
* Metric Name: Concealed Seconds

* Metric Description: A count of the number of Concealed Seconds
that have occurred.

* Method of Measurement or Calculation: See section 4. 2, Section 4.2,
Concealed Seconds definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 4.2, Concealed Seconds
definition [RFCXXXX].
definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 5th paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 4, 1st paragraph [RFCXXXX] for
measurement timing and section Section 4.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

h. Severely Concealed Seconds Metric

* Metric Name: Severely Concealed Seconds

* Metric Description: A count of the number of Severely
Concealed Seconds that have occurred.

* Method of Measurement or Calculation: See section 4. 2, Section 4.2,
Severely Concealed Seconds definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 4.2, Severely Concealed
Seconds definition [RFCXXXX]. definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 5th paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 4, 1st paragraph [RFCXXXX] for
measurement timing and section Section 4.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611. RFC 3611.

i. SCS Threshold Metric

* Metric Name: SCS Threshold
* Metric Description: The amount of time corresponding to lost
or discarded frames that must occur within a one second one-second period
in order for the second to be classified as a Severely
Concealed Second.

* Method of Measurement or Calculation: See section 4. 2, Section 4.2, SCS
Threshold definition [RFCXXXX]. definition.

* Units of Measurement: See section Section 4.2, SCS Threshold
definition [RFCXXXX].
definition.

* Measurement Point(s) with Potential Measurement Domain: See
section
Section 1.1, 5th paragraph [RFCXXXX]. paragraph.

* Measurement Timing: See section Section 4, 1st paragraph [RFCXXXX] for
measurement timing and section Section 4.2 [RFCXXXX] for Interval Metric flag.

* Use and applications: Applications: See section 1.4 [RFCXXXX]. Section 1.4.

* Reporting model: Model: See RFC3611.

Appendix B. Change Log

Note to the RFC-Editor: please remove this section prior to
publication as an RFC.

B.1. draft-ietf-xrblock-rtcp-xr-loss-conceal-11

The following are the major changes to previous version :

o Address comments recieved in Gen-Art Review and OPS-DIR Review.

B.2. draft-ietf-xrblock-rtcp-xr-loss-conceal-09

The following are the major changes to previous version :

o Only Version Number changes.

B.3. draft-ietf-xrblock-rtcp-xr-loss-conceal-07

The following are the major changes to previous version :

o Change units for threshold and units used for reporting in loss
concealment block and concealment seconds block.

o Change 16bit "Mean Playout Interrupt Size" into 32bits.

B.4. draft-ietf-xrblock-rtcp-xr-loss-conceal-06

The following are the major changes to previous version :

o Comments in the WGLC are addressed in this version.

B.5. draft-ietf-xrblock-rtcp-xr-loss-conceal-05

The following are the major changes to previous version :

o Add text to clarify the definition of enhanced method.

o Add appendix to apply RFC6390 template to the metrics.

B.6. draft-ietf-xrblock-rtcp-xr-loss-conceal-04

The following are the major changes to previous version :

o Merge Concealment Seconds draft into this draft (i.e.,Loss
Concealment draft).

o Updated references. RFC 3611.

Authors' Addresses

Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, GA 30097
USA

Email:

EMail: alan.d.clark@telchemy.com

Glen Zorn
Network Zen
77/440 Soi Phoomjit, Rama IV Road
Phra Khanong, Khlong Toie
Bangkok 10110
Thailand

Phone: +66 (0) 87 502 4274
Email:
EMail: gwz@net-zen.net
Claire Bi
Shanghai Research Institure Institute of China Telecom Corporation Limited
No.1835,South
No. 1835, South Pudong Road
Shanghai 200122
China

Email:

EMail: bijy@sttri.com.cn

Qin Wu (editor)
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China

Email:

EMail: sunseawq@huawei.com