RTCP XR Report Block for Loss Concealment Metrics Reporting on Video Applications
draft-ietf-xrblock-rtcp-xr-video-lc-01

XRBLOCK                                                         R. Huang
INTERNET-DRAFT                                                    Huawei
Intended Status: Standards Track                                A. Clark
Expires: January 7, 2016                                        Telchemy
                                                            July 6, 2015

    RTCP XR Report Block for Loss Concealment Metrics Reporting on 
                           Video Applications
                 draft-ietf-xrblock-rtcp-xr-video-lc-01

Abstract

   This draft defines a new video loss concealment block type to augment
   those defined in [RFC3611] and [RFC7294] for use in a range of RTP
   video applications.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

Copyright and License Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
 

<Huang, et al.>         Expires January 7, 2016                 [Page 1]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

   (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
     1.1 RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . .  3
     1.2 Performance Metrics Framework  . . . . . . . . . . . . . . .  3
     1.3 Applicability  . . . . . . . . . . . . . . . . . . . . . . .  3
   2  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3  Video Loss Concealment Methods  . . . . . . . . . . . . . . . .  4
   4.  Video Loss Concealment Report Block  . . . . . . . . . . . . .  5
   5 SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1 SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . .  8
     5.2 Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . .  8
   6 Security Considerations  . . . . . . . . . . . . . . . . . . . .  9
   7 IANA Considerations  . . . . . . . . . . . . . . . . . . . . . .  9
     7.1 New RTCP XR Block Type Value . . . . . . . . . . . . . . . .  9
     7.2 New RTCP XR SDP Parameter  . . . . . . . . . . . . . . . . .  9
     7.3 Contact Information for registrations  . . . . . . . . . . .  9
   8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 10
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 11
   Appendix A. Metrics Represented Using the Template from RFC 6390 . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15

 

<Huang, et al.>         Expires January 7, 2016                 [Page 2]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

1  Introduction

   Multimedia applications often suffer from packet losses in IP
   networks. In order to get a reasonable degree of quality in case of
   packet losses, it is necessary to have loss concealment mechanisms at
   the decoder. Video loss concealment is a range of techniques to mask
   the effects of packet loss in video communications. 

   In some applications, reporting the information of receivers applying
   video loss concealment could give monitors or senders useful
   information on application QoE. One example is no-reference video
   quality evaluation. Video probes located upstream from the video
   endpoint or terminal may not see loss occurring between the probe and
   the endpoint, and may also not be fully aware of the specific loss
   concealment methods being dynamically applied by the video endpoint.
   Evaluating error concealment is important in the circumstance in
   estimating the subjective impact of impairments.  

   This draft defines one new video loss concealment block type to
   augment those defined in [RFC3611] and [RFC7294] for use in a range
   of RTP video applications. The metrics defined in this draft belong
   to the class of transport-related terminal metrics defined in
   [RFC6792].

1.1 RTCP and RTCP XR Reports

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

1.2 Performance Metrics Framework

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

1.3 Applicability

   These metrics are applicable to video applications of RTP and the
   video component of Audio/Video applications in which packet loss
   concealment mechanisms are incorporated into the receiving endpoint
   to mitigate the impact of network impairments on QoE. For example, in
   an IPTV system Set Top Boxes could use this RTCP XR block to report
   loss and loss concealment metrics to an IPTV management system to
 

<Huang, et al.>         Expires January 7, 2016                 [Page 3]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

   enable the service provider to monitor the quality of the IPTV
   service being delivered to end users.

2  Terminology

   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 [KEYWORDS].

3  Video Loss Concealment Methods

   Video loss concealment mechanisms can be classified into 4 types as
   follow:

   a) Frame freeze

   The impaired video frame is not displayed, instead, the previously
   displayed frame is frozen for the duration of the loss event.

   b) Inter-frame extrapolation

   If an area of the video frame is damaged by loss, the same area from
   the previous frame(s) can be used to estimate what the missing pixels
   would have been. This can work well in a scene with no motion but can
   be very noticeable if there is significant movement from one frame to
   another. Simple decoders may simply re-use the pixels that were in
   the missing area while more complex decoders may try to use several
   frames to do a more complex extrapolation. Another example of a
   sophisticated form of inter-frame repair is to estimate the motion of
   the damaged region based on the motion of surrounding regions, and
   use that to select what part of the previous frame to use for repair.

   c) Interpolation

   A decoder may user the undamaged pixels in the video frame to
   estimate what the missing block of pixels should have.

   d) Error Resilient Encoding

   The sender may encode the message in a redundant way so that receiver
   can correct errors using the redundant information. The redundant
   data useful for error resiliency performed at the decoder can be
   embedded into the compressed image/video bitstream. For example, the
   encoder may select a crucial area of an original video frame, extract
   some important characteristics of this area as the redundant
   information, e.g., redundant motion vector of the first macroblock in
   a slice of this area and redundant motion vector difference of other
   macroblocks in this slice of this area, and imperceptibly embed them
 

<Huang, et al.>         Expires January 7, 2016                 [Page 4]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

   into other parts of the video frame sent in a different RTP packet or
   in the next frame, e.g., other slices of this area. FEC is also
   another error resilient method.

   In this document, we differentiate between frame freeze and the other
   3 concealment mechanisms described.

4.  Video Loss Concealment Report Block

   This block reports the video loss concealment metrics to complement
   the audio metrics defined in [RFC7294]. The report block SHOULD be in
   conjunction with the information from the Measurement Information
   Block [RFC6776]. Instances of this metrics block refer by SSRC to the
   separate auxiliary Measurement Information Block [RFC6776]. This
   metrics block relies on the measurement period in the Measurement
   Information Block indicating the span of the report and SHOULD be
   sent in the same compound RTCP packet as the Measurement Information
   Block. If the measurement period is not received in the same compound
   RTCP packet as this metric block, this metric block MUST be
   discarded. It should be noted that the metrics in this report block
   are based on measurements that are typically made at the time that a
   video frame is decoded and rendered for playout. The metrics in this
   block MUST be measured at a consistent point.

   The video loss concealment report block has the following format:

    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=VLC     | I | V |  RSV  |       block length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         SSRC of Source                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Impaired Duration                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Concealed Duration                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Mean Frame Freeze Duration (optional)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    MIFP       |    MCFP       |     FFSC      |     Reserved  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 1: Format for the Video Loss Concealment Report Block

   Block Type (BT): 8 bits

 

<Huang, et al.>         Expires January 7, 2016                 [Page 5]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      A Video Loss Concealment Report Block is identified by the
      constant VLC.

      [Note to RFC Editor: Please replace VLC with the IANA provided
      RTCP XR block type for this block.]

   Interval Metric Flag (I): 2 bits

      This field indicates whether the reported metric is an interval,
      cumulative, or sampled metric [RFC6792]:

         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 - this value MUST NOT be used for this
         block type.

         I=00: Reserved.

   Video Loss Concealment Method Type (V): 2 bits

      This field is used to identify the video loss concealment method
      type used at the receiver. Each bit indicates one method type, as
      follow:

        V=10 - Frame freeze
        V=11 - Other Loss Concealment Method
        V=01&00 - Reserved

      If Frame freeze and other loss concealment method are used
      together for the media stream, 2 report blocks, one with V=10 for
      frame freeze and one with V=11 for other loss concealment method
      SHOULD be compounded together to report the whole concealment
      information.

   block length: 16 bits

      This field is in accordance with the definition in [RFC3611]. In
      this report block, it MUST be set to 6 when V=10 and be set to 5
      when V=11. The block MUST be discarded if the block length is set
      to a different value.

   SSRC of source: 32 bits

 

<Huang, et al.>         Expires January 7, 2016                 [Page 6]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      As defined in Section 4.1 of [RFC3611].

   Impaired Duration: 32 bits

      The total time length, expressed in units of RTP timestamp, of
      video impaired by  transmission loss before applying any loss
      concealment methods. 

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

   Concealed Duration: 32 bits

      The total time length, expressed in units of RTP timestamp, of
      concealed damaged video pictures on which loss concealment method
      corresponding to V is applied.

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

   Mean Frame Freeze Duration: 32 bits

      Mean Frame Freeze Duration is the mean duration, expressed in
      units of RTP timestamp, of the frame freeze events. The value of
      Mean Frame Freeze Duration shall be calculated by summing the
      total duration of all frame freeze events and dividing by the
      number of events. This metric is optional. It only exists
      whenV=10.

   Mean Impaired Frame Proportion (MIFP): 8 bits

      Mean Impaired Frame Proportion is the mean proportion of each
      video frame impaired by loss before applying any loss concealment
      method during the interval, expressed as a fixed point number with
      the binary point at the left edge of the field. It is calculated
      by summing the impaired proportion of each video frame and
      dividing by the number of frames during this period. The impaired
      proportion of each video frame is obtained by dividing the number
      of missing macroblocks from this video frame by the total
      macroblock number of the video frame, which is equivalent to
      taking the integer part after multiplying the fraction by 256. If
      a video frame is totally lost, a value of 0xFF shall be used for
      the frame when calculating the mean value.

   Mean Concealed Frame Proportion (MCFP): 8 bits

 

<Huang, et al.>         Expires January 7, 2016                 [Page 7]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      Mean Concealed Frame Proportion is the mean proportion of each
      video frame to which loss concealment (using V) was applied during
      the interval, expressed as a fixed point number with the binary
      point at the left edge of the field. It is calculated by summing
      the concealed proportion of each video frame and dividing by the
      number of frames during this period. The concealed proportion of
      each video frame is obtained by dividing the number of concealed
      macroblocks from this video frame by the total macroblock number
      of the video frame, which is equivalent to taking the integer part
      after multiplying the fraction by 256. If a lost video frame is
      totally concealed, a value of 0xFF and if there are no concealed
      macroblocks, a value of 0, shall be used for the frame when
      calculating the mean value.

   Fraction of Frames Subject to Concealment (FFSC): 8 bits

      Fraction of Frames Subject to Concealment is calculated by
      dividing the number of frames to which loss concealment (using V)
      was applied by the total number of frames and expressing this
      value as a fixed point number with the binary point at the left
      edge of the field. It is equivalent to taking the integer part
      after multiplying the fraction by 256. A value of 0 indicates that
      there were no concealed frame and a value of 0xFF indicates that
      the frames in the entire measurement interval are all concealed. 

   Reserved: 8 bits

      These bits are reserved for future use.  They MUST be set to zero
      by senders and ignored by receivers (see Section 4.2 of
      [RFC6709]).

5 SDP Signaling

   [RFC3611] defines the use of SDP (Session Description Protocol) for
   signaling the use of RTCP XR blocks. However XR blocks MAY be used
   without prior signaling (see section 5 of [RFC3611]).

5.1 SDP rtcp-xr-attrib Attribute Extension

   This session augments the SDP attribute "rtcp-xr" defined in Section
   5.1 of [RFC3611] by providing an additional value of "xr-format" to 
   signal the use of the report block defined in this document.

   xr-format =/ xr-vlc-block

   xr-vlc-block = "video-loss-concealment"

5.2 Offer/Answer Usage
 

<Huang, et al.>         Expires January 7, 2016                 [Page 8]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

   When SDP is used in offer-answer context, the SDP Offer/Answer usage
   defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters
   applies.  For detailed usage of Offer/Answer for unilateral
   parameter, refer to section 5.2 of [RFC3611].

6 Security Considerations

   It is believed that this RTCP XR block introduces no new security
   considerations beyond those described in [RFC3611]. This block does
   not provide per-packet statistics, so the risk to confidentially
   documented in Section 7, paragraph 3 of [RFC3611] does not apply.

   An attacker may put incorrect information in the Video Loss
   Concealment reports, which will be affect the estimation of video
   loss concealment mechanisms performance and QoE of users.
   Implementers should consider the guidance in [RFC7202] for using
   appropriate security mechanisms, i.e., where security is a concern,
   the implementation should apply encryption and authentication to the
   report block. For example, this can be achieved by using the AVPF
   profile together with the Secure RTP profile as defined in [RFC3711];
   an appropriate combination of the two profiles (an "SAVPF") is
   specified in [RFC5124]. However, other mechanisms also exist
   (documented in [RFC7201]) and might be more suitable.

7 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].

7.1 New RTCP XR Block Type Value

   This document assigns the block type value VLC in the IANA "RTP
   Control Protocol Extended Reports (RTCP XR) Block Type Registry" to 
   the "Video Loss Concealment Metrics Report Block".

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

7.2 New RTCP XR SDP Parameter

   This document also registers a new parameter "video-loss-concealment"
   in the "RTP Control Protocol Extended Reports (RTCP XR) Session
   Description Protocol (SDP) Parameters Registry".

7.3 Contact Information for registrations

   The following contact information is provided for all registrations
 

<Huang, et al.>         Expires January 7, 2016                 [Page 9]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

   in this document:

   Rachel Huang (rachel.huang@huawei.com)

   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu 210012
   China

8 Acknowledgements

   The author would like to thank Colin Perkins, Roni Even for their
   valuable comments.

9  References

9.1  Normative References

   [KEYWORDS] 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., Ed., Caceres, R., Ed., and A. Clark, Ed.,
              "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.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.

   [RFC5124]  Ott, J. and E. Carrara, "Extended Secure RTP Profile for
              Real-time Transport Control Protocol (RTCP)-Based Feedback
              (RTP/SAVPF)", RFC 5124, February 2008.

   [RFC5105]  Lendl, O., "ENUM Validation Token Format Definition",
              RFC 5105, December 2007.

   [RFC4588]  Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
              Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
              July 2006.

   [RFC6776]  Clark, A. and Q. Wu, "Measurement Identity and Information
              Reporting Using a Source Description (SDES) Item and an
 

<Huang, et al.>         Expires January 7, 2016                [Page 10]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

              RTCP Extended Report (XR) Block", RFC6776, October 2012.

   [RFC7201]  Westerlund, M. and C., Perkins, "Qptions for Securing RTP
              Sessions", RFC 7201, April 2014.

   [RFC7202]  Perkins, C. and M., Westerlund, "Securing the RTP
              Framework: Why RTP Does Not Mandate a Single Media
              Security Solution", RFC 7202, April 2014.

   [RFC7294] Clark, A., Zorn, G., Bi, C. and Q., Wu, "RTCP XR Report
              Block for Concealment Metrics Reporting on Audio
              Applications", April 2014.

9.2  Informative References

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

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

Appendix A. Metrics Represented Using the Template from RFC 6390

   a. Video Impaired Duration Metric

      * Metric Name: Video Impaired Duration Metric

      * Metric Description: The total time length of video impaired by
      transmission loss before applying any loss concealment methods.

      * Method of Measurement or Calculation: The metric is based on
      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout.

      * Units of Measurement: This metric is expressed in units of RTP
      timestamp.

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 1 of Section 4.

      * Use and Applications: The metric is applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
 

<Huang, et al.>         Expires January 7, 2016                [Page 11]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      network impairments on QoE.

   b. Video Concealed Duration Metric

      * Metric Name: Video Concealed Duration Metric

      * Metric Description: The total time length of concealed damaged
      video pictures on which loss concealment method corresponding to V
      is applied.

      * Method of Measurement or Calculation: The metric is based on
      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout.

      * Units of Measurement: This metric is expressed in units of RTP
      timestamp.

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 2 of Section 4.

      * Use and Applications: These metrics are applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
      network impairments on QoE.

   c. Mean Video Frame Freeze Duration Metric

      * Metric Name: Mean Video Frame Freeze Duration Metric

      * Metric Description: The mean duration of the frame freeze
      events.

      * Method of Measurement or Calculation: The metric is based on
      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout. The metric shall be
      calculated by summing the total duration of all frame freeze
      events and dividing by the number of events.

      * Units of Measurement: This metric is expressed in units of RTP
      timestamp.

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 2 of Section 4.
 

<Huang, et al.>         Expires January 7, 2016                [Page 12]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      * Use and Applications: These metrics are applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
      network impairments on QoE.

   d. Mean Impaired Video Frame Proportion Metric

      * Metric Name: Mean Impaired Video Frame Proportion Metric

      * Metric Description: Mean proportion of each video frame impaired
      by loss before applying any loss concealment method during the
      interval.

      * Method of Measurement or Calculation: The metric is based on
      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout. It is calculated by
      summing the impaired proportion of each video frame and dividing
      by the number of frames during this period. The impaired
      proportion of each video frame is obtained by dividing the number
      of lost RTP packets from this video frame by the total packet
      number of the video frame, which is equivalent to taking the
      integer part after multiplying the loss fraction by 256. If a
      video frame is totally lost, a value of 0xFF shall be used for the
      frame when calculating the mean value.

      * Units of Measurement: This metric is expressed as a fixed point
      number with the binary point at the left edge of the field.

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 2 of Section 4.

      * Use and Applications: These metrics are applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
      network impairments on QoE.

   e. Mean Concealed Video Frame Proportion Metric

      * Metric Name: Mean Concealed Video Frame Proportion Metric

      * Metric Description: Mean proportion of each video frame to which
      loss concealment (using V) was applied during the interval.

      * Method of Measurement or Calculation: The metric is based on
 

<Huang, et al.>         Expires January 7, 2016                [Page 13]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout. It is calculated by
      summing the concealed proportion of each video frame and dividing
      by the number of frames during this period. The concealed
      proportion of each video frame is obtained by dividing the number
      of concealed macroblocks from this video frame by the total
      macroblock number of the video frame, which is equivalent to
      taking the integer part after multiplying the fraction by 256. If
      a lost video frame is totally concealed, a value of 0xFF and if
      there are no concealed macroblocks, a value of 0, shall be used
      for the frame when calculating the mean value.

      * Units of Measurement: This metric is expressed as a fixed point
      number with the binary point at the left edge of the field.

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 2 of Section 4.

      * Use and Applications: These metrics are applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
      network impairments on QoE.

   f. Fraction of Video Frames Subject to Concealment Metric

      * Metric Name: Fraction of Video Frames Subject to Concealment
      Metric

      * Metric Description: Proportion of concealed video frames to
      which loss concealment (using V) was applied comparing to the
      total number of frames during the interval.

      * Method of Measurement or Calculation: The metric is based on
      measurements that are typically made at the time that a video
      frame is decoded and rendered for playout. This metric is
      calculated by dividing the number of frames to which loss
      concealment (using V) was applied by the total number of frames.
      It is equivalent to taking the integer part after multiplying the
      fraction by 256. A value of 0 indicates that there were no
      concealed frame and a value of 0xFF indicates that the frames in
      the entire measurement interval are all concealed.

      * Units of Measurement:  This metric is expressed as a fixed point
      number with the binary point at the left edge of the field.

 

<Huang, et al.>         Expires January 7, 2016                [Page 14]
INTERNET DRAFT       <Video LC Metrics for RTCP XR>         July 6, 2015

      * Measurement Point(s) with Potential Measurement Domain: It is
      measured at the receiving end of the RTP stream.

      * Measurement Timing: See paragraph 2 of Section 4.

      * Use and Applications: These metrics are applicable to video
      applications of RTP and the video component of Audio/Video
      applications in which packet loss concealment mechanisms are
      incorporated into the receiving endpoint to mitigate the impact of
      network impairments on QoE.

Authors' Addresses

   Rachel Huang
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing 210012
   China

   EMail: rachel.huang@huawei.com

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

   Email: alan.d.clark@telchemy.com

<Huang, et al.>         Expires January 7, 2016                [Page 15]