1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T P.1203.2 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2017) SERIES P: TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Models and tools for quality assessment of streamed media Parametric
2、bitstream-based quality assessment of progressive download and adaptive audiovisual streaming services over reliable transport Audio quality estimation module Recommendation ITU-T P.1203.2 ITU-T P-SERIES RECOMMENDATIONS TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Voc
3、abulary and effects of transmission parameters on customer opinion of transmission quality Series P.10 Voice terminal characteristics Series P.30 P.300 Reference systems Series P.40 Objective measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements rel
4、ated to speech loudness Series P.70 Methods for objective and subjective assessment of speech quality Series P.80 Methods for objective and subjective assessment of speech and video quality Series P.800 Audiovisual quality in multimedia services Series P.900 Transmission performance and QoS aspects
5、of IP end-points Series P.1000 Communications involving vehicles Series P.1100 Models and tools for quality assessment of streamed media Series P.1200 Telemeeting assessment Series P.1300 Statistical analysis, evaluation and reporting guidelines of quality measurements Series P.1400 Methods for obje
6、ctive and subjective assessment of quality of services other than speech and video Series P.1500 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T P.1203.2 (10/2017) i Recommendation ITU-T P.1203.2 Parametric bitstream-based quality assessment of progressive download
7、 and adaptive audiovisual streaming services over reliable transport Audio quality estimation module Summary Recommendation ITU-T P.1203.2 specifies the short-term audio quality estimation module for Recommendation ITU-T P.1203. The ITU-T P.1203 series of ITU-T Recommendations specifies modules for
8、a set of model algorithms for monitoring the integral media session quality for transport control protocol (TCP) type video streaming. The models comprise modules for short-term video-quality and audio-quality estimation (the latter specified in this Recommendation). The per-one-second outputs of th
9、ese short-term modules are integrated into estimates of audio-visual quality and together with information about initial loading delay and media playout stalling events, they are further integrated into the final model output, the estimate of integral quality. The respective ITU-T work item has form
10、erly been referred to as “Parametric non-intrusive assessment of TCP-based multimedia streaming quality“ or “P.NATS“. The Recommendation ITU-T P.1203.2 part of Recommendation ITU-T P.1203 provides details for the module for bitstream-based, short-term audio quality estimation. Only one audio module
11、is recommended for all four modes 0 to 3 of the Recommendation ITU-T P.1203 model series, corresponding to mode 0. The model is identical to the audio coding quality estimation component of the user datagram protocol (UDP) streaming related prediction model described in Recommendation ITU-T P.1201.
12、History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T P.1203.2 2016-11-29 12 11.1002/1000/13160 2.0 ITU-T P.1203.2 2017-10-29 12 11.1002/1000/13401 Keywords Adaptive streaming, audio, audiovisual, IPTV, mean opinion score (MOS), mobile video, mobile TV, monitoring, multimedia, pro
13、gressive download, QoE, TV, video. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T P.1203.2 (10/2017) FOREWORD The Internatio
14、nal Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operati
15、ng and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, prod
16、uce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In thi
17、s Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., in
18、teroperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest
19、 that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence
20、, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be re
21、quired to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2017 All rights reserved. No part of this publication may be reprod
22、uced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T P.1203.2 (10/2017) iii Table of Contents Page 1 Scope . 1 2 References . 3 3 Definitions 3 3.1 Terms defined elsewhere 3 3.2 Terms defined in this Recommendation . 4 4 Abbreviations and acronyms 4 5 Conventions 4
23、6 Pa module in ITU-T P.1203 context . 4 6.1 Pa module modes . 5 7 Model input . 5 7.1 I.11 input specification . 6 8 Model algorithm and output . 6 Bibliography. 8 Rec. ITU-T P.1203.2 (10/2017) 1 Recommendation ITU-T P.1203.2 Parametric bitstream-based quality assessment of progressive download and
24、adaptive audiovisual streaming services over reliable transport Audio quality estimation module 1 Scope This RecommendatioSn describes the short term audio quality estimation module which is an integral part of the ITU-T P.1203 series. ITU-T P.1203 describes a set of objective parametric quality ass
25、essment modules. Combined, these modules can be used to predict the impact of audio and video media encodings as well as Internet protocol (IP) network impairments on the quality experienced by an end-user of multi-media streaming applications. The addressed streaming techniques comprise progressive
26、 download as well as adaptive streaming, for both mobile and fixed network streaming applications over transport control protocol (TCP) or other TCP like protocols which are not affected by transmission errors. The model described is restricted to information provided to it by an appropriate packet-
27、 or bitstream-analysis module. The overall ITU-T P.1203 model is applicable for the effects due to audio- and video-coding as well as initial loading delay and stalling (which are both caused by rebuffering at the client) as the typical degradations associated with progressive download. As final out
28、put, the ITU-T P.1203 series models target integral audio-visual media quality scores. This Recommendation describes only one audio quality module. With regard to the required input data, this audio module corresponds to mode 0 of ITU-T P.1203. The same, purely header-based/bitrate-based audio quali
29、ty module is also specified in ITU-T P.1201.2. Using a large number of subjective experiments, it was validated that this model also leads to accurate predictions within the scope of ITU-T P.1203. The audio module predicts mean opinion scores (MOS) on a 5-point absolute category rating (ACR) scale (
30、see ITU-T P.910) as a per-one-second MOS score. During the development of ITU-T P.1201, explicit short-term audio quality tests were carried out in order to validate the stand-alone use of the audio module for the estimation of audio-only quality. It could be shown within the scope of ITU-T P.1201 t
31、hat this is possible. It must be noted however, that since the subjective tests conducted for ITU-T P.1201 included packet loss degradations, range-equalization and other biases may need to be considered (see for example b-Zielinski_2008) if the module is to be used stand-alone within the scope of I
32、TU-T P.1203. This model cannot provide a comprehensive evaluation of audio transmission quality as perceived by an individual end user because its scores reflect the impairments due to audio coding only. Furthermore, the scores predicted by a parametric model necessarily reflect an average perceptua
33、l impairment. Note also that the model was developed and validated for one specific encoder and decoder implementation. If a different encoder and decoder pair is used in a monitoring situation the scores may not reflect that. Effects such as audio level or noise (and corresponding similar audio fac
34、tors) or other impairments related to the audio signals are not reflected in the scores computed by this model. Moreover, the scores predicted by a parametric model (i.e., without access to payload information, such as the audio signals) necessarily reflect a somewhat simplified representation of th
35、e perceptual impairment of the considered stream. 2 Rec. ITU-T P.1203.2 (10/2017) However, presuming that it is applied in an appropriate manner, according to this Recommendation, the model still enables estimation of some coding quality related information and thus valid and in most cases accurate
36、predictions. Tables 1.1 and 1.2 indicate the areas and parameter ranges for which the Pa module specified in this Recommendation has been validated and for which applications it can be used, with some caution. Table 1.1 Application areas, test factors and coding technologies where ITU-T P.1203.2 for
37、 adaptive streaming and progressive download has been verified and is known to produce reliable results Applications for which the model is intended In-service monitoring of TCP-based audio. Both so called over the top (OTT) services (for example YouTube) and operator managed video services (over TC
38、P), using the protocols HTTP/TCP/IP and RTMP/TCP/IP. Note that this model is agnostic to the type of container format (e.g. Flash (FLV), MP4, WebM or 3GP. Performance and quality assessment of live networks (including codecs) considering the effect due to encoding bit rate. Audio test factors for wh
39、ich the model has been validated Input audio length Maximum 20 seconds. The video model produces a per-second score considering input data from a measurement window of max. 20 s length. Bitstream container Coded audio bitstream contained in MPEG-2 transport stream (TS) segments Encoder/Decoder imple
40、mentation The model has been trained using the following audio encoder: AAC-LC: libfdk_aac, low complexity (LC) mode (ffmpeg). A common framework was developed based on the above codec, all the test data was generated using the common framework. Audio sample rate 48 000 samples/s Audio bit rate 16,
41、32, 64 and 98 kBit/s/channel Audio bit rate was always varied in a correlated fashion with the video bit rate, i.e., high video bit rate corresponds to high audio bit rate and vice versa. Bearing to this condition it has been observed that audio quality has very little effect on the overall audio-vi
42、sual quality. Segment length 1-9 seconds NOTE The segment length determines how often the audio quality can be adapted. Audio channels 2 (stereo) Table 1.2 Application areas, test factors and coding technologies for which ITU-T P.1203.2 is assumed to give valid results Test factors where the model c
43、an be used but the results may not be reliable (conditions not included in subjective tests underlying the model development) All factors as indicated in Table 1.1, with additions as described below: Codecs: HE-AACv2, AC3, MPEG-LII Bit rates: 4.75-576 kbit/s NOTE ITU-T P.1203 was tested on AAC-LC on
44、ly. The audio module alone has been tested with the codecs mentioned above with dedicated audio-quality tests during ITU-T P.1201 development. Rec. ITU-T P.1203.2 (10/2017) 3 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this tex
45、t, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition o
46、f the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T P.800.1 Recommendation ITU-T
47、P.800.1 (2016), Mean opinion score (MOS) terminology. ITU-T P.910 Recommendation ITU-T P.910 (2008), Subjective video quality assessment methods for multimedia applications. ITU-T P.911 Recommendation ITU-T P.911 (1998), Subjective audiovisual quality assessment methods for multimedia applications.
48、ITU-T P.1201 Recommendation ITU-T P.1201 (2012), Parametric non-intrusive assessment of audiovisual media streaming quality. ITU-T P.1201.1 Recommendation ITU-T P.1201.1 (2012), Parametric non-intrusive assessment of audiovisual media streaming quality Lower resolution application area. ITU-T P.1201
49、.2 Recommendation ITU-T P.1201.2 (2012), Parametric non-intrusive assessment of audiovisual media streaming quality Higher resolution application area. ITU-T P.1202 Recommendation ITU-T P.1202 (2012), Parametric non-intrusive bitstream assessment of video media streaming quality. ITU-T P.1202.1 Recommendation ITU-T P.1202.1 (2012), Parametric non-intrusive bitstream assessment of video media streaming quality Lower resolution application area. ITU-T P.1203 Recommendation ITU-T P.1203 (2016), Parametric bitstream-based
