1、 Recommendation ITU-R BS.2094-1 (06/2017) Common definitions for the audio definition model BS Series Broadcasting service (sound) ii Rec. ITU-R BS.2094-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spec
2、trum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication
3、 Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statem
4、ents and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also av
5、ailable online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satelli
6、te services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals
7、 and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2017 ITU 2017 All rights reserved. No part of this publication may be reproduced, by any mea
8、ns whatsoever, without written permission of ITU. Rec. ITU-R BS.2094-1 1 RECOMMENDATION ITU-R BS.2094-1 Common definitions for the audio definition model (2016-2017) Scope This Recommendation contains a set of common definitions for multichannel audio configurations that use the audio definition mod
9、el (Recommendation ITU-R BS.2076) to describe them. Keywords ADM, audio, multichannel, channel-based, tracks, metadata, bw64, exchange, audio programme, BWF, immersive, HOA, Higher Order Ambisonic The ITU Radiocommunication Assembly, considering a) that storage media based on information technology,
10、 including data disks and tapes, have penetrated all areas of audio production for radio broadcasting, namely non-linear editing, on-air play-out and archives; b) that the adoption of a single file format for signal interchange would greatly simplify the interoperation of individual pieces of equipm
11、ent, and remote studios, and it would facilitate the desirable integration of editing, on-air play-out, and archiving; c) that compatibility with currently-available commercial file formats would minimize the industry efforts required to implement a new format in the equipment; d) that future audio
12、systems will require metadata associated with the audio to be carried in the file; e) that future audio systems will use a variety of multichannel configurations including channel-, object-, and scene-based audio such as specified in Recommendation ITU-R BS.2051; f) that future audio systems will us
13、e the audio definition model (Recommendation ITU-R BS.2076) to describe the technical format of the audio being delivered and exchanged; g) that the majority of audio in existence and produced in the short-term future is and will be channel-based using a commonly used set of configurations; h) that
14、using different metadata descriptions for identical audio configurations will cause compatibility problems and unnecessary overheads, recommends that, for exchanging any audio that uses the audio definition model (Recommendation ITU-R BS.2076) as the metadata model, a set of common definitions be us
15、ed to describe any audio configurations as defined in Annex 1. 2 Rec. ITU-R BS.2094-1 Annex 1 (normative) Common definitions for the audio definition model 1 Introduction Recommendation ITU-R BS.2076 Audio Definition Model, is a metadata model used to describe the technical content and format of aud
16、io. It can be used to describe any type of audio signal to allow it to be rendered correctly, whether it be object-, scene-, or channel-based. While the audio definition model (ADM) is extremely flexible and allows any type of audio format to be defined, the vast majority of audio in existence is ba
17、sed on a few commonly-used channel-based configurations. Therefore, it is not efficient for these commonly used formats to need to be explicitly defined every time they are used. It would also be problematic for identical formats to be defined in different ways by different organisations or applicat
18、ions. To provide consistency and efficiency in the use of the ADM, a set of common definitions has been drawn up. These are based on what is commonly used in the audio industry, including those specified in Recommendations ITU-R BS.2051 and ITU-R BS.775 to produce definitions that should be used whe
19、n these configurations are used in files and streams. This set of common definitions is intended to be a living resource, with new definitions added in the future should they be required. 2 Contents of the common definitions As the vast majority of existing audio (and in the short-term future) is ch
20、annel-based, most of the common definitions will be for channel-based audio. The initial set will concentrate on commonly used channel-based configurations. The other assumption used is that the track formats are pulse code modulation (PCM), so it does not include coded audio. The ADM consists of se
21、veral different elements used for defining audio. They either describe the content or the format. The set of common definitions is only concerned about the format elements as these can be defined without knowledge of the content of the audio. These elements are: audioTrackFormat audioStreamFormat au
22、dioChannelFormat audioBlockFormat audioPackFormat Apart from audioPackFormat the elements are very closely tied together with one of each used for each channel definition. However, it does not mean that all four of these elements are required to be used at all times. It is perfectly acceptable to us
23、e a common audioChannelFormat/ audioBlockFormat definition with custom-made audioTrackFormat and audioStreamFormat definitions. 3 Common definitions usage The common definitions exist as an extensible markup language (XML) file which can be either stored locally with the application that is handling
24、 the audio files, or referred to remotely. It is not intended to be carried in the audio file itself, as one of the intentions of it is to reduce the amount of metadata required to be carried in audio files. Rec. ITU-R BS.2094-1 3 Any code that reads audio files that contain ADM-defined audio (so BW
25、F, BW64, RF64 typically) should always aim to read the common definitions first before reading the ADM metadata stored within the audio file itself. The relationship between the audio file and the common definitions file is shown in Fig. 1. FIGURE 1 Relationship between audio file and common definit
26、ions file BS .20 94 01-A udi o fi l eCo n t ai n s au d i o s am p l esC o m m o n def i ni ti o ns fi l eRe ad t h i s b ef o re ch u n kOt her chu nks L o o k u p t ab l e fo r t ra ck san d t h ei r ADMd ef i n i t i o n sCo n t ai n s ADMme t ad at a re l ev an t o n l yt o t h i s fi l eTrackan
27、dPacksIDPacksIDO b j ec t T ra ck sU IDT ra ck an d Pac k sIDThe chunk contains an ID reference to both an audioTrackFormat and an audioPackFormat definition for each track in the file. These references should be looked up in the common definitions file first to see whether that contains the IDs, an
28、d if not then the audio files chunk should be referred to. When inspecting the content-related ADM metadata in the chunk, in particular the audioObject elements, it may have references to IDs that exist in the common definitions file, most probably audioPackFormat IDs. This ordering of the chunks is
29、 not strict, and it may be preferable to place the chunk after the chunk. 4 Set of common definitions The set of common definitions consists of commonly used channel-based configurations, some of which are recognised standards and some are common proprietary configurations. The definitions consist o
30、f a set of audioChannelFormat definitions for channels associated with many different speaker locations, including all those in Recommendation ITU-R BS.2051. Each of these channel definitions has an associated audioStreamFormat and audioTrackFormat definition for PCM audio signals to cover the most
31、typical use case. The set of audioPackFormat definitions for the various speaker combinations use only channels from this common set. The audioChannelFormat and the audioPackFormat IDs follow this format: audioChannelFormatID: AC_yyyy0xxx audioPackFormatID: AP_yyyy0xxx where the first four hexadecim
32、al digits (yyyy) indicate what the type of audio is. If this value is set to 0001 then the type is DirectSpeakers, if it is 0002 then it is Matrix, 0003 for Objects, 0004 for HOA and 0005 for Binaural. The final four digits (0xxxx) have values below 1000, so belong to the set of common definitions a
33、s listed here. 4 Rec. ITU-R BS.2094-1 4.1 Common definitions for the DirectSpeakers audio type 4.1.1 Common audioChannelFormats for DirectSpeakers TABLE 1 AudioChannelFormat definitions for DirectSpeakers audioChannelFormatID audioChannelFormatName Azimuth Elevation speakerLabel AC_00010001 FrontLef
34、t 30 0 M+030 AC_00010002 FrontRight 30 0 M-030 AC_00010003 FrontCentre 0 0 M+000 AC_00010004* LowFrequencyEffects 0 30 LFE AC_00010005 SurroundLeft 110 0 M+110 AC_00010006 SurroundRight 110 0 M-110 AC_00010007 FrontLeftOfCentre 22 0 M+022 AC_00010008 FrontRightOfCentre 22 0 M-022 AC_00010009 BackCen
35、tre 180 0 M+180 AC_0001000a SideLeft 90 0 M+090 AC_0001000b SideRight 90 0 M-090 AC_0001000c TopCentre 0 90 T+000 AC_0001000d TopFrontLeft 30 30 U+030 AC_0001000e TopFrontCentre 0 30 U+000 AC_0001000f TopFrontRight 30 30 U-030 AC_00010010 TopSurroundLeft 110 30 U+110 AC_00010011 TopBackCentre 180 30
36、 U+180 AC_00010012 TopSurroundRight 110 30 U-110 AC_00010013 TopSideLeft 90 30 U+090 AC_00010014 TopSideRight 90 30 U-090 AC_00010015 BottomFrontCentre 0 30 B+000 AC_00010016 BottomFrontLeftMid 45 30 B+045 AC_00010017 BottomFrontRightMid 45 30 B-045 AC_00010018 FrontLeftWide 60 0 M+060 AC_00010019 F
37、rontRightWide 60 0 M-060 AC_0001001a BackLeftMidDiffuse 135 0 M+135_Diff AC_0001001b BackRightMidDiffuse 135 0 M-135_Diff Rec. ITU-R BS.2094-1 5 TABLE 1 (end) audioChannelFormatID audioChannelFormatName Azimuth Elevation speakerLabel AC_0001001c BackLeftMid 135 0 M+135 AC_0001001d BackRightMid 135 0
38、 M-135 AC_0001001e TopBackLeftMid 135 30 U+135 AC_0001001f TopBackRightMid 135 30 U-135 AC_00010020* LowFrequencyEffectsL 45 30 LFE1 AC_00010021* LowFrequencyEffectsR 45 30 LFE2 AC_00010022 TopFrontLeftMid 45 30 U+045 AC_00010023 TopFrontRightMid 45 30 U-045 AC_00010024 FrontLeftScreen Left screen e
39、dge (or 25 if unknown) 0 M+SC AC_00010025 FrontRightScreen Right screen edge (or -25 if unknown) 0 M-SC AC_00010026 FrontLeftMid 45 0 M+045 AC_00010027 FrontRightMid 45 0 M-045 AC_00010028 UpperTopBackCentre 180 45 UH+180 * These channels also feature a low pass frequency cut-off of 120 Hz. Each cha
40、nnel definition is listed in Table 1, where the audioChannelFormatID, audioChannelFormatName and speakerLabel elements are listed. The azimuth and elevation columns represent the position that would be specified within the position sub-element (the distance is 1.0 for all these channel definitions).
41、 The XML below shows how the first entry in this table is represented in XML. urn:itu:bs:2051:0:speaker:M+030 30.0 0.0 1.0 4.1.2 Common audioStreamFormats and audioTrackFormats for DirectSpeakers The common format type for audioStreamFormat and audioTrackFormat is PCM. As previously mentioned, the a
42、udioStreamFormat and audioTrackFormat, which relate to each audioChannelFormat definition use the same ID prefixes and the same names with PCM_ appended, such as PCM_FrontLeft. The XML code below shows both the audioStreamFormat and audioTrackFormat definition for the first entry in the Table. AC_00
43、010001 AT_00010001_01 AS_00010001 6 Rec. ITU-R BS.2094-1 4.1.3 Common audioPackFormats for DirectSpeakers The audioPackFormat definitions cover a range of speaker configurations. Table 2 shows the set of configurations that have been defined. The ones that are in Recommendation ITU-R BS.2051 are ind
44、icated. The last column gives the references to each channel the pack consists of. Instead of giving the whole ID (e.g. AP_00010001), only the last two digits are listed for clarity; so they would be AP_000100xx where xx is the digits listed to give the full audioPackFormatIDRef. The audioPackFormat
45、 names have been given both a traditional name and the name formatted in the style of Recommendation ITU-R BS.2051 (U+M+L) separated by an underscore. Spaces are not used in the names as they can cause problems. TABLE 2 AudioPackFormat definitions audioPackFormatID audioPackFormatName Recommendation
46、 derived from audioChannelIDRef audioChannelName Channel name in Recommendation speakerLabel AP_00010001 mono_(0+1+0) BS.775 AC_00010003 FrontCentre Centre M+000 AP_00010002 stereo_(0+2+0) BS.775, BS.2051 (A) AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AP_0001000a 3.0_(0+3+0)
47、 BS.775 AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AC_00010003 FrontCentre Centre M+000 AP_0001000b 4.0_(0+4+0) BS.775 AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AC_00010003 FrontCentre Centre M+000 AC_00010009 BackCentre Mono Surround M+180 AP_00010
48、00c 5.0_(0+5+0) BS.775 AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AC_00010003 FrontCentre Centre M+000 AC_00010005 SurroundLeft Left Surround M+110 AC_00010006 SurroundRight Right Surround M-110 Rec. ITU-R BS.2094-1 7 TABLE 2 (continued) audioPackFormatID audioPackFormatName
49、 Recommendation derived from audioChannelIDRef audioChannelName Channel name in Recommendation speakerLabel AP_00010003 5.1_(0+5+0) BS.775, BS.2051 (B) AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AC_00010003 FrontCentre Centre M+000 AC_00010004 LowFrequencyEffects Low Frequency Effects LFE AC_00010005 SurroundLeft Left Surround M+110 AC_00010006 SurroundRight Right Surround M-110 AP_0001000d 6.1_(0+6+0) N/A AC_00010001 FrontLeft Left M+030 AC_00010002 FrontRight Right M-030 AC_00010003 FrontCentre Cent
