1、BSI Standards Publication BS ISO/IEC 23003-4:2015 Information technology MPEG audio technologies Part 4: Dynamic Range ControlBS ISO/IEC 23003-4:2015 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO/IEC 23003-4:2015. The UK participation in its preparation was
2、 entrusted to Technical Committee IST/37, Coding of picture, audio, multimedia and hypermedia information. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users
3、 are responsible for its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 87316 4 ICS 35.040 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of
4、 the Standards Policy and Strategy Committee on 30 November 2015. Amendments/corrigenda issued since publication Date T e x t a f f e c t e dBS ISO/IEC 23003-4:2015 Information technology MPEG audio technologies Part 4: Dynamic Range Control Technologies de linformation Technologies audio MPEG Parti
5、e 4: Contrle de gamme dynamique INTERNATIONAL STANDARD ISO/IEC 23003-4 Reference number ISO/IEC 23003-4:2015(E) First edition 2015-11-15 ISO/IEC 2015 BS ISO/IEC 23003-4:2015ii ISO/IEC 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015, Published in Switzerland All rights reserved. Un
6、less otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the
7、 address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/IEC 23003-4:2015(E)BS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E)Forewo
8、rd v Introduction vi 1 Scope . 1 2 Normative references 1 3 T erms, definitions and mnemonics . 1 3.1 Terms . 1 3.2 Mnemonics . 2 4 Symbols (and abbreviated terms) 2 5 Technical overview . 3 6 DRC decoder 4 6.1 DRC decoder configuration 4 6.1.1 Overview . 4 6.1.2 Description of logical blocks 5 6.1.
9、3 Derivation of peak and loudness values 8 6.2 Dynamic DRC gain payload 11 6.3 DRC set selection 12 6.3.1 Overview 12 6.3.2 Pre-selection based on Signal Properties and Decoder Configuration 13 6.3.3 Selection based on requests 16 6.3.4 Final selection .18 6.3.5 Applying multiple DRC sets .18 6.3.6
10、Album mode 19 6.3.7 Ducking .19 6.3.8 Precedence .19 6.4 Time domain DRC application 19 6.4.1 Overview 19 6.4.2 Framing .20 6.4.3 Time resolution 20 6.4.4 Time alignment 20 6.4.5 Decoding 20 6.4.6 Gain modifications and interpolation .24 6.4.7 Spline interpolation . .28 6.4.8 Look-ahead in decoder 2
11、8 6.4.9 Node reservoir 29 6.4.10 Applying the compression 30 6.4.11 Multi-band DRC filter bank 33 6.5 Sub-band domain DRC .37 6.6 Loudness normalization 40 6.6.1 Overview 40 6.6.2 Loudness normalization based on target loudness 40 6.7 DRC in streaming scenarios 43 6.7.1 DRC configuration 43 6.7.2 Er
12、ror handling .43 6.8 DRC configuration changes during active processing 43 7 Syntax 45 7.1 Syntax of DRC payload .45 7.2 Syntax of DRC gain payload .46 7.3 Syntax of static DRC payload 47 7.4 Syntax of DRC gain sequence .59 Annex A (normative) Tables .60 Annex B (normative) External Interface to DRC
13、 tool 74 ISO/IEC 2015 All rights reserved iii Contents PageBS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E)Annex C (informative) A udio c odec specific information 85 Annex D (informative) DRC gain generation and encoding .90 Annex E (informative) DRC set selection and adjustment at decoder 95 Annex F
14、 (informative) Loudness normalization 100 Annex G (informative) Peak limiter 101 Bibliography .106 iv ISO/IEC 2015 All rights reservedBS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E) Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commissio
15、n) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and
16、 IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC
17、 JTC 1. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of document should be noted. This document was drafted in accordance with
18、the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details o
19、f any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endors
20、ement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following URL: Foreword Supplementary information. The committee respon
21、sible for this document is ISO/IEC JTC 1, Information Technology, Subcommittee SC 29, Coding of audio, picture, multimedia, and hypermedia. ISO/IEC 23003 consists of the following parts, under the general title Information technology MPEG audio technologies: Part 1: MPEG Surround Part 2: Spatial Aud
22、io Object Coding Part 3: Unified speech and audio coding Part 4: Dynamic Range Control ISO/IEC 2015 All rights reserved vBS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E) Introduction Consumer audio systems and devices are used in a large variety of configurations and acoustical environments. For many
23、of these scenarios, the audio reproduction quality can be improved by appropriate control of content dynamics and loudness. This part of ISO/IEC 23003 provides a universal dynamic range control tool that supports loudness normalization. The DRC tool offers a bitrate efficient representation of dynam
24、ically compressed versions of an audio signal. This is achieved by adding a low-bitrate DRC metadata stream to the audio signal. The DRC tool includes dedicated sections for clipping prevention, ducking, and for generating a fade-in and fade-out to supplement the main dynamic range compression funct
25、ionality. The DRC effects available at the DRC decoder are generated at the DRC encoder side. At the DRC decoder side, the audio signal may be played back without applying the DRC tool, or an appropriate DRC tool effect is selected and applied based on the given playback scenario.vi ISO/IEC 2015 All
26、 rights reservedBS ISO/IEC 23003-4:2015Information technology MPEG audio technologies Part 4: Dynamic Range Control 1 Scope This part of ISO/IEC 23003 specifies technology for loudness and dynamic range control. This International Standard is applicable to most MPEG audio technologies. It offers fle
27、xible solutions to efficiently support the widespread demand for technologies such as loudness normalization and dynamic range compression for various playback scenarios. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispen
28、sable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 14496-12, Information technology Coding of audio-visual objects Part 12: ISO base media file format ISO/I
29、EC 23001-8, Information technology MPEG systems technologies Part 8: Coding-independent code points 3 T erms, d efinitions and mnemonics For the purposes of this document, the terms and definitions given in ISO/IEC 14496-12 and the following apply. 3.1 Terms 3.1.1 DRC sequence series of DRC gain val
30、ues that can be applied to one or more audio channels 3.1.2 DRC set defined set of DRC sequences that produce a desired effect if applied to the audio signal 3.1.3 album collection of audio recordings that are mastered in a consistent way. Traditionally, a collection of songs released on a Compact D
31、isk belongs into this category, for example INTERNATIONAL ST ANDARD ISO/IEC 23003-4:2015(E) ISO/IEC 2015 All rights reserved 1BS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E) 3.2 Mnemonics bslbf bit string, left bit first, where “left” is the order in which bit strings are written in ISO/IEC 14496. Bi
32、t strings are written as a string of 1s and 0s within single quote marks, for example 1000 0001. Blanks within a bit string are for ease of reading and have no significance uimsbf unsigned integer, most significant bit first vlclbf variable length code, left bit first, where “left” refers to the ord
33、er in which the variable length codes are written bit(n) a bit string with n bits in the same format as bslbf unsigned int(n) an unsigned integer with n bits in the same for- mat as uimsbf signed int(n) a signed integer with n bits, most significant bit first 4 Symbols (and abbreviated terms) a i Fi
34、lter coefficient b Band index of DRC filter bank (starting at 0) b i Filter coefficient deltaTmin Smallest permitted DRC gain sample interval in units of the audio sample interval. f c Cross-over frequency in Hz f c,norm Cross-over frequency expressed as fraction of the audio sample rate. f c,norm,S
35、B (s) Cross-over frequency of audio decoder sub-band s expressed as fraction of the audio sample rate. The cross-over frequency is the upper band edge frequency of the sub- band. f s Audio sample rate in Hz. If an audio decoder is present, it is the sample rate of the de- coded time-domain audio sig
36、nal. N DRC Maximum permitted number of DRC samples per DRC frame. Identical to the number of intervals with a duration of deltaTmin per DRC frame. N Codec Codec frame size in units of the audio sample interval 1/f s M DRC DRC frame size in units of the audio sample interval 1/f s Ratio of a circles
37、circumference to its diameter s Audio decoder sub-band index (starting at 0) TRUE/FALSE Values of Boolean data type, which correspond to numerical 1 and 0, respectively. z Complex variable of the z-transform2 ISO/IEC 2015 All rights reservedBS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E) 5 Technical
38、overview The technology described in this part of ISO/IEC 23003 is called DRC tool. It provides efficient control of dynamic range, loudness, and clipping based on metadata generated at the encoder. The decoder can choose to selectively apply the metadata to the audio signal to achieve a desired res
39、ult. Metadata for dynamic range compression consists of encoded time-varying gain values that can be applied to the audio signal. Hence, the main blocks of the DRC tool include a DRC gain encoder, a DRC gain decoder, a DRC gain modification block, and a DRC gain application block. These blocks are e
40、xercised on a frame-by-frame basis during audio processing. Various DRC configurations can be conveyed in a separate bitstream element, such as configurations for a downmix or combined DRCs. The DRC set selection block decides based on the playback scenario and the applicable DRC configurations whic
41、h DRC gains to apply to the audio signal. Moreover, the DRC tool supports loudness normalization based on loudness metadata. A typical system for loudness and dynamic range control in the time domain is shown in Figure 1. A more complex system including downmixer and peak limiter is shown in Figure
42、2. The decoder part of the DRC tool is driven by metadata that efficiently represents the DRC gain samples and parameters for interpolation. The gain samples can be updated as fast as necessary to accurately represent gain changes down to at least 1 ms update intervals. In the following the decoder
43、part of the DRC tool is referred to as “DRC decoder”, which includes everything except the audio decoder and associated bitstream de-multiplexing. Figure 1 Block diagram of a typical system with audio decoder and DRC tool modules to achieve loudness normalization (LN) and dynamic range control Figur
44、e 2 Block diagram of a more complex system including downmixer and peak limiter (TD = time-domain, SD = subband-domain) ISO/IEC 2015 All rights reserved 3BS ISO/IEC 23003-4:2015ISO/IEC 23003-4:2015(E) 6 DRC decoder 6.1 DR C dec oder c onfigur ation 6.1.1 Overview The DRC configuration information ca
45、n be received in-stream using the static payloads uniDrcConfig() and loudnessInfoSet() described below, or it can be delivered by a higher layer, such as 14496-12 (see Table 1). The basic decoding process of the static information is virtually the same. The difference consists mainly in a few syntax
46、 changes and reduced field sizes to increase the bit rate efficiency of the in- stream configuration. The syntax of the in-stream static payload is given in 7.3. The associated metadata encoding is given inA.6. The static DRC payload is evaluated once at the beginning of the decoding process and it
47、is monitored subsequently. For static DRC payload changes during playback see 6.8. T a b l e 1 O v e r v i e w o f c o n f i g u r a t i o n ( s e t u p ) a n d s e p a r a t e m e t a d a t a t r a c k i n I S O / I E C 1 4 49 6 - 1 2 Sample Entry Code Setup (in sample entry) Track reference Sample
48、 format Audio Track As specified for the audio codec in use (un- changed) DRCInstructions box using negative values for drcLoca- tion adrc referring to the metadata tracks carry- ing gain values As specified for the audio codec in use (unchanged) Metadata Track unid (none) (none) Each sample is a un
49、- iDrcGain() payload The static payload is divided into five logical blocks: channelLayout(); downmixInstructions(); drcCoefficientsBasic(), drcCoefficientsUniDrc(); drcInstructionsBasic(), drcInstructionUniDrc(); loudnessInfo(). Except for the channelLayout(), multiple instances of a logical block can appear. The DRC decoder combines the information of the matching instances of up to five logical blocks for a given playback scenario. Matching instances a
