Section 1: General
1.1 Scope
This Standard specifies the coded representation of high quality audio for storage media and the method for decoding of high quality audio signals. The input of the encoder and the output of the decoder are compatible with existing PCM standards such as stíwdard Coinpact Disc and Digital Audio Tape.
This Standard is intended for application to digital storage media providing a total continuous transfer rate of about 1,s Mbitdsec for both audio and video bitstreams, such as CD, DAT and magnetic hard disc. The storage inedia may either be connected directly to the decoder, or via other means such as communication lines and the GB/T 17191 multiplexed stream defined in GB/T17191. This Standard is intended for sampling rates of 32 kHz, 44, l kHz, and 48 kHz.
1.2 Normative References
The following International Standards constitute 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 17191.1-1997 Information Technology - Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5Mbit/s--Part 1: Systems
GB/T 17191.2-1997 Information Technology--Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5Mbit/s--Part 2: Video
CCIR Recoinmendation 601-2 Encoding Parameters of Digital Television for Studios.
CCIR Report 624-4 Characteristics of Systems For Monochrome And Colour Television.
CCIR Recommendation 648 Recording of Audio Signals.
CCIR Report 955-2 Sound Broadcasting by Satellite for Portable and Mobile Receivers, Including Annex Ⅳ Summary Description of Advanced Digital System II.
CCITT Recoinmendation J. 17 Pre-Emphasis Used on Sound-Programme Circuits.
IEEE Draft Staiidard P1180/D2 1990 Specification for the Implementation of 8x8 Inverse Discrete Cosine Transfom.
IEC Publication 908:1987 CD Digital Audio System.
Section 2: Technical Elements
2.1 Definitions
For the purposes of GB/T 17191, the following definitions apply. If specific to a part, this is noted in square brackets.
2.1.1 Ac coefficient [video]: Any DCT coefficient for which the frequency in one or both dimensions is non-zero.
2.1.2 Access unit [system]: In the case of compressed audio an access unit is an audio access unit. In the case of compressed video an access unit is the coded representation of a picture.
2.1.3 Adaptive segmentation [audio]: A subdivision of the digitai representlition of an audio signal in variable segments of time.
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 noise allocation [audio]: The assignment of coding noise to frequency bands in a time and frequency varying fashion according to a psychoacoustic model.
2.1.6 Alias [audio]: Mirrored signal component resulting from sub-Nyquist sampling.
2.1.7 Analysis filterbank [audio]: Filterbank in the encoder that transforms a broadband PCM audio signal into a set of subsampled subband samples.
2.1.8 Audio access unit [audio]: For Layers I aid II an audio access unit is defined as the smallest part of the encoded bitstream which mi 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.
2.1.9 Audio buffer [audio]: A buffer in the system karget decoder for storage of compressed audio data.
2.1.10 Audio sequence [audio]: A non-interrupted series of audio frames in which the following parameters are not changed:
Foreword I
ISO/IEC Foreword II
Introduction III
Section 1: General
1.1 Scope
1.2 Normative References
Section 2: Technical Elements
2.1 Definitions
2.2 Symbols and Abbreviations
2.3 Method of Describing Bitstream Syntax
2.4 Requirements
Annex A (Normative) Diagrams
Annex B (Normative) Tables
Annex C (Informative) The Coding Process
Annex D (Informative) Psychoacoustic models
Annex E (Informative) Bit Sensitivity to Errors
