1 General
1.1 Scope
This Standard specifies the extension of GB/T 17191.3 to:
1) lower sampling frequencies;
2) the coded representation of multichannel and multilingual high quality audio, and the method for decoding of multichannel and multilingual high quality audio signals. The input of the encoder and the output of the decoder are compatible with existing PCM standards.
This Standard is applicable to broadcasting, transmission and storage media.
1.2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below.
GB/T 14857-1993 The Specifications of Encoding Parameters of Digital Television for Studio
GB/T 17191.3-1993 Information Technology — Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mbit/s — Part 3: Audio
GB/T 17576-1998 Compact Disc Digital Audio System
IEEE Draft Standard P1180/D2:1990 Specification for the Implementation of 8×8 Inverse Discrete Cosine Transform
ITU-R Recommendation 648:1986 Recording of Audio Signals
ITU-R Recommendation 775:1992 Multichannel Stereophonic Sound System with and without Accompanying Picture
ITU-R Recommendation 955-2:1990 Sound Broadcasting by Satellite for Mobile, Portable and Fixed Receivers, including 500 MHz to 3 000 MHz
ITU-T Recommendation G.722:1988 7 kHz Audio Coding within 64 kbit/s
ITU-T Recommendation J.52:1995 Digital Transmission of High Quality Sound Program Signals Using One, Two or Three 64 kbit/s Channels per Mono Signal (and up to Six per Stereo Signal)
ETS 300401: 1995 Radio Broadcasting System; Digital Audio Broadcasting (DAB) to Mobile, Portable and Fixed Receivers
2 Technical Elements
2.1 Definitions
For the purposes of this Standard, the following definitions apply.
2.1.1 16×8 prediction (video)
A prediction mode similar to field-based prediction but where the predicted block size is 16×8 luminance samples.
2.1.2 AC coefficient (video)
Any DCT coefficient for which the frequency in one or both dimensions is non-zero.
2.1.3 Access unit (system)
A coded representation of a presentation unit. In the case of audio, an access unit is the coded representation of an audio frame.
In the case of video, an access unit includes all the coded data for a picture, and any stuffing that follows it, up to but not including the start of the next access unit. If a picture is not preceded by a group_start_code or a sequence_header_code, the access unit begins with the picture start code. If a picture is preceded by a group_start_code and/or a sequence_header_code, the access unit begins with the first byte of the first of these start codes. If it is the last picture preceding a sequence_end_code in the bitstream all bytes between the last byte of the coded picture and the sequence_end_code (including the sequence_end_code) belong to the access unit.
2.1.4 Adaptive bit allocation (audio)
The assignment of bits to subbands in a time and frequency varying fashion according to a psychoacoustic model.
2.1.5 Adaptive multichannel prediction (audio)
A method of multichannel data reduction exploiting statistical inter-channel dependencies.
2.1.6 Adaptive noise allocation (audio)
The assignment of coding noise to frequency bands in a time and frequency varying fashion according to a psychoacoustic model.
2.1.7 Adaptive segmentation (audio)
A subdivision of the digital representation of an audio signal in variable segments of time.
2.1.8 Alias (audio)
Mirrored signal component resulting from sub-Nyquist sampling.
2.1.9 Analysis filterbank (audio)
Filterbank in the encoder that transforms a broadband PCM audio signal into a set of subsampled subband samples.
2.1.10 Ancillary data (audio)
Part of the bitstream that might be used for transmission of ancillary data.
2.1.11 Audio access unit (audio)
For Layers I and II, an audio access unit is defined as the smallest part of the encoded bitstream which can be decoded by itself, where decoded means "fully reconstructed sound". For Layer III, an audio access unit is part of the bitstream that is decodable with the use of previously acquired main information.
2.1.12 Audio buffer (audio)
A buffer in the system target decoder for storage of compressed audio data.
2.1.13 Audio sequence (audio)
A non-interrupted series of audio frames (base frames plus optional extension frames) in which the following parameters are not changed:
— ID
— Layer
— Sampling Frequency
For Layer I and II, a decoder is not required to support a continuously variable bitrate (change in the bitrate index) of the base stream. Such a relaxation of requirements does not apply to the extension stream.
Foreword II
Foreword of ISO/IEC III
Introduction IV
0.1 Extension of GB/T 17191.3 Audio Coding to Lower Sampling Frequencies IV
0.2 Low bitrate coding of multichannel audio V
1 General
1.1 Scope
1.2 Normative references
2 Technical Elements
2.1 Definitions
2.2 Symbols and abbreviations
2.3 Method of describing bit stream syntax
2.4 Requirements for Extension of GB/T 17191.3 to Lower Sampling Frequencies
2.5 Requirements for Extension of GB/T 17191.3 to Multichannel Audio
Annex A (Normative) Diagrams
Annex B (Normative) Tables
Annex C (Informative) The Encoding Process
Annex D (Informative) Psychoacoustic Models
Annex E (Informative) Ancillary Data Use
