| Network Working Group | A. Clark |
| Internet-Draft | Telchemy |
| Intended status: Standards Track | Q. Wu |
| Expires: December 25, 2016 | Huawei |
| R. Schott | |
| DT | |
| G. Zorn | |
| Network Zen | |
| 2013 |
RTP Control Protocol (RTCP) Extended Report (XR) Blocks for QoE Metric Reporting
draft-ietf-xrblock-rtcp-xr-qoe-04
This document defines an RTP Control Protocol (RTCP) Extended Report (XR) Block including two new segment types and associated SDP parameters that allow the reporting of QoE metrics for use in a range of RTP applications.
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This document defines a new block type to augment those defined in [RFC3611], for use in a range of RTP applications.
The new block type provides information on multimedia quality using one of several standard metrics.
The metrics belong to the class of application level metrics defined in [RFC6792].
The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] defined an extensible structure for reporting using an RTCP Extended Report (XR). This draft defines a new Extended Report block for use with [RFC3550] and [RFC3611].
The Performance Metrics Framework [RFC6390] provides guidance on the definition and specification of performance metrics. The RTP Monitoring Architectures [RFC6792] provides guideline for reporting block format using RTCP XR. The XR Block described in this document are in accordance with the guidelines in [RFC6390] and [RFC6792].
The QoE Metrics Report Block can be used in any application of RTP for which QoE measurement algorithms are defined.
The factors that affect real-time AV application quality can be split into two categories. The first category consists of transport- dependent factors such as packet loss, delay and jitter (which also translates into losses in the playback buffer). The factors in the second category are application-specific factors that affect real time application (e.g., video) quality and are sensitivity to network errors. These factors can be but not limited to video codec and loss recovery technique, coding bit rate, packetization scheme, and content characteristics.
Compared with application-specific factors, the transport-dependent factors sometimes are not sufficient to measure real time data quality, since the ability to analyze the real time data in the application layer provides quantifiable measurements for subscriber Quality of Experience (QoE) that may not be captured in the transmission layers or from the RTP layer down. In a typical scenario, monitoring of the transmission layers can produce statistics suggesting that quality is not an issue, such as the fact that network jitter is not excessive. However, problems may occur in the service layers leading to poor subscriber QoE. Therefore monitoring using only network-level measurements may be insufficient when application layer content quality is required.
In order to provide accurate measures of real time application quality when transporting real time contents across a network, the synthentical multimedia quality Metrics is highly required which can be conveyed in the RTCP XR packets[RFC3611] and may have the following three benefits:
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 RFC 2119 [RFC2119].
The terminology used is
This block reports the multimedia application performance or quality beyond the information carried in the standard RTCP packet format. Information is recorded about multimedia application QoE metric which provides a measure that is indicative of the user's view of a service. Multimedia application QoE metric is commonly expressed as a MOS ("Mean Opinion Score"), MOS is on a scale from 1 to 5, in which 5 represents excellent and 1 represents unacceptable. MOS scores are usually obtained using subjective testing or using objective algorithm. However Subjective testing to estimate the multimedia quality may be not suitable for measuring the multimedia quality since the results may vary from test to test. Therefore using objective algorithm to calculate MOS scores is recommended. ITU-T recommendations define the methodologies for assessment of the performance of multimedia stream [G.107][P.564][G.1082][P.1201.1][P.1201.2][P.1202.1][P.NBAMS-HR] and provides a method to evaluate QoE estimation algorithms and objective model for video and audio. Hence this document recommends vendors and implementers to use these International Telecommunication Union (ITU)-specified methodologies to measure parameters when possible.
The report block contents are dependent upon a series of flag bits carried in the first part of the header. Not all parameters need to be reported in each block. Flags indicate which are and which are not reported. The fields corresponding to unreported parameters MUST be present, but are set to zero. The receiver MUST ignore any QoE Metrics Block with a non-zero value in any field flagged as unreported. The encoding of QoE metrics block payload consists of a series of 32 bit units called segments that describe MOS Type, MoS algorithm and MoS value.
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=QMB | I | Reserved | Block Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Segment n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The QoE Metrics Block has the following format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| CAID | PT | MOS Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| CAID | PT |CHID | MOS Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
[RFC3611] defines the use of SDP (Session Description Protocol) [RFC4566] for signaling the use of XR blocks. However XR blocks MAY be used without prior signaling (see section 5 of RFC3611).
This section augments the SDP [RFC4566] attribute "rtcp-xr" defined in [RFC3611] by providing an additional value of "xr-format" to signal the use of the report block defined in this document. Within the "xr-format", the syntax element "extmap" is an attribute as defined in [RFC4566] and used to signal the mapping of the local identifier (CAID) in the segment extension defined in section 3.2 to the calculation algorithm. Specific extensionattributes are defined by the specification that defines a specific extension name; there may be several.
xr-format =/ xr-qoe-block
xr-qoe-block = "qoe-metrics" ["=" extmap *("," extmap)]
extmap = mapentry "=" extensionname [SP extentionattributes]
direction = "sendonly" / "recvonly" / "sendrecv" / "inactive"
mapentry = "calg:" 1*5 DIGIT ["/" direction]
extensionname = "P564";ITU-T P.564 Compliant Algorithm [P.564]
/ "G107";ITU-T G.107 [G.107]
/ "TS101_329";ETSI TS 101 329-5 Annex E [ ETSI]
/"JJ201_01 ";TTC JJ201.01 [TTC]
/"P1201_01";ITU-T P.1201.2 [P.1201.1]
/"P1201_02";ITU-T P.1201.2 [P.1201.2]
/"P1202_01";ITU-T P.1202.1 [P.1202.1]
/"P1202_02";ITU-T P. NBAMS-HR [P.NBAMS-HR]
/ non-ws-string
extentionattributes = mediatype
/mosreference
/attributes-ext
mediatype = "a" ;voice
/ "v" ;video
/"m" ;multimedia
mosreference = "mosref=" ("0"; lower resolution
/ "1";higher resolution
/ 1*2DIGIT ) ;Value 2~15 are valid and
;reserved for future use
attributes-ext = non-ws-string
SP = <Define in RFC5234>
DIGIT = <as defined in Section 3.4 of [RFC5234]>
non-ws-string = 1*(%x21-FF)
a=extmap:<value> ["/"<direction>] <name> <extensionattributes>
Each local identifier (CAID)of calculation algorithm used in the segment defined in the section 3.2 is mapped to a string using an attribute of the form:
Example: a = calg:1=G107,calg:2=P1202.1
where <name> is a calculation algorithm name, as above, <value> is the local identifier (CAID)of the calculation algorithm associated with the segment defined in this document and is an integer in the valid range inclusive.
A usable mapping MUST use IDs in the valid range, and each ID in this range MUST be unique and used only once for each stream or each channel in the stream.
The mapping MUST be provided per media stream (in the media-level section(s) of SDP, i.e., after an "m=" line).
Note that the syntax element "mosreference" is referred to the media resolution(e.g., Narrowband (3.4kHz) Speech and Standard Definition (SD) Resolution Video with lower resolution, Wideband (7kHz) Speech and High Definition (HD) Resolution Video with higher resolution). MOS scores reported in the QoE block may vary with the Mos reference; For example MOS values for narrowband, wideband codecs occupy the same range but should be reported in different value. For video application,MoS scores for SD resolution, HD resolution video also occupy the same ranges and should be reported in different value.
When SDP is used in offer-answer context, the SDP Offer/Answer usage defined in [RFC3611] applies. In the offer answer context, the signaling described above may be used in three ways:
A direction attribute MAY be included in an extmap; without it, the direction implicitly inherits, of course, from the stream direction.
Segment extension, with their directions, may be signaled for an "inactive" stream. It is an error to use an extension direction incompatible with the stream direction (e.g., a "sendonly" attribute for a "recvonly" stream).
If an segment extension map is offered as "sendrecv", explicitly or implicitly, and asymmetric behavior is desired, the SDP may be modified to modify or add direction qualifiers for that segment extension.
Local identifiers in the valid range inclusive in an offer or answer must not be used more than once per media section. A session update MAY change the direction qualifiers of segment extensions under use. A session update MAY add or remove segment extension(s). Identifiers values in the valid range MUST NOT be altered (remapped).
If a party wishes to offer mutually exclusive alternatives, then multiple segment extensions with the same identifier in the (unusable) range 4096-4351 may be offered; the answerer should select at most one of the offered extensions with the same identifier, and remap it to a free identifier in the valid range, for that extension to be usable. Note that two segment types defined in section 3 are also two exclusive alternatives.
If more segment extensions are offered in the valid range, the answerer should choose those that are desired, and place the offered identifier value "as is" in the SDP answer.
Similarly, if more segment extensions are offered than can be fit in the valid range, identifiers in the range 4096-4351 may be offered; the answerer should choose those that are desired, and remap them to a free identifier in the valid range.
Example (port numbers, RTP profiles, payload IDs and rtpmaps, etc. all omitted for brevity): The offer:
Note that the range 4096-4351 for these negotiation identifiers is deliberately restricted to allow expansion of the range of valid identifiers in future. segment extensions with an identifier outside the valid range cannot, of course, be used.
The answerer is interested in transmission P.1202.1 only on video, but doesn't understand P.1202.1 at all. It is interested in transmission G.107 on audio. It therefore adjusts the declarations:
a=rtcp-xr:qoe-metrics=calg:1=P1202.1v, calg:2=G107a
New block types for RTCP XR are subject to IANA registration. For general guidelines on IANA considerations for RTCP XR, refer to [RFC3611].
This document assigns the block type value MMQ in the IANA "RTCP XR Block Type Registry" to the "QoE Metrics Block".
[Note to RFC Editor: please replace MMQ with the IANA provided RTCP XR block type for this block.]
This document also registers a new parameter "qoe-metrics" in the "RTCP XR SDP Parameters Registry".
Qin Wu sunseawq@huawei.com 101 Software Avenue, Yuhua District Nanjing, JiangSu 210012 China
The contact information for the registrations is:
Name Name Description Reference Type ========= =================================== ========== ==== P564 ITU-T P.564 Compliant Algorithm [P.564] Voice G107 ITU-T G.107 [G.107] Voice TS101_329 ETSI TS 101 329-5 Annex E [ETSI] Voice JJ201_01 TTC JJ201.01 [TTC] Voice P1201_01 ITU-T P.1201.01 [P.1201.1] Multimedia P1201_02 ITU-T P.1201.02 [P.1201.2] Multimedia P1202_01 ITU-T P.1202.01 [P.1202.01] Video P1202_02 ITU-T P. NBAMS-HR [P. NBAMS-HR] Video
This document creates a new registry to be called "RTCP XR QoE metric block - multimedia application Calculation Algorithm" as a sub- registry of the "RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry". This registry applies to the multimedia session where each type of media are sent in a separate RTP stream and also applies to the session where Multi-channel audios are carried in one RTP stream. Policies for this new registry are as follows:
The new RTCP XR report blocks proposed in this document introduces no new security considerations beyond those described in [RFC3611].
This draft merges ideas from two drafts addressing the QoE metric Reporting issue. The authors of these drafts are listed below (in alphabetical order):
The authors would like to thank Bill Ver Steeg, David R Oran, Ali Begen,Colin Perkins, Roni Even,Youqing Yang, Wenxiao Yu and Yinliang Hu for their valuable comments and suggestions on this document.
To evaluate user quality of experience levels using objective test data. MoS Scores provide a familiar, easily understood numeric representation of video, audio, and overall audiovisual quality. Unlike audio, video is even more sensitive to transport impairments than voice, and even low rates of packet loss can cause severe degradation in perceived quality. However, all occurrences of packet loss do not have an equal impact on perceptual quality, in part because of the way video frames are structured during the encoding process – such as frame properties including frame type and quantization parameter (QP), frame structure, and in part due to subjective factors – such as the degree to which perception is affected by the levels of motion and detail in the video sequence, demux/decoder statistics characteristic parameters including jitter buffer metrics and packet loss concealment metrics. When a video stream is sent from the media source to RTP receiving end and get monitored, in order to provide accurate evaluation of video quality, One possible evaluation method of QoE is the network nodes that implement network management tools may get frame properties,perception degree as MoS calculation input parameters from media source, and demux/decoder statistics characteristic parameters and transport impairment as other MoS calculation input parameters from the RTP receiving end and use appropriate MoS calculation algorithm to calculate MoS scores. Such MoS Scores value can be useful for troubleshooting or comparing video quality across different service types.
The following are the major changes compared to previous version:
The following are the major changes compared to previous version:
The following are the major changes compared to previous version:
The following are the major changes compared to previous version:
The following are the major changes compared to previous version: