GB/T 17975.7-2002
Information technology--Generic coding of moving pictures and associated audio information Part 7: Advanced audio coding (English Version)

Standard No.

GB/T 17975.7-2002

Language

Chinese, Available in English version

Release Date

2002

Published By

General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China

Latest

GB/T 17975.7-2002

Scope

This standard describes the MPEG-2 audio non-backward compatible standard, called MPEG-2 Advanced Audio Coding, or AAC. Compared with the existing MPEG-2 BC (MPEG-1 backward compatible), AAC is a higher-quality multi-channel standard. For five full-bandwidth channel audio signals, at a digital rate of 320 kbit/s, the MPEG-2 AAC audio standard meets the ITU-R "indistinguishable" quality requirements. The working process of the AAC decoder utilizes a series of mandatory or optional modules. Table 1 lists these modules and whether they are mandatory. Mandatory modules are required in any framework. Optional modules can be omitted in some frameworks. Table 1 ┏━━━━━━━━┳┳━━━━━┓┓ Module name┃ Mandatory/Optional┃ ┣━━━━━━━━╋━━━━━━━ ━┫ ┃ Bitstream assembler┃ Required┃ ┣━━━━━━━━╋━━━━━━━┫ ┃ Noiseless decoding┃ Required┃ ┣━━━━━━━━╋ ━━━━━━━┫ ┃ Dequantizer┃ Required┃ ┣━━━━━━━━╋━━━━━━┫┫ Scale factor┃ Required┃ ┣━━━━━ ━━━━╋━━━━━━━┫ ┃ M/S ┃ Optional┃ ┣━━━━━━━╋━━━━━━━┫ ┃ Prediction┃ Optional┃ ┣━ ━━━━━━━━╋━━━━━━┫┫ ┃ Strength/Coupling┃ Optional┃ ┣━━━━━━━╋━━━━━━┫ ┃ TNS ┃ Yes ┃ ┣━━━━━━━━━╋━━━━━━┫┫ Filter Bank┃ Mandatory┃ ┣━━━━━━━━╋━━━━━━┫┫ ┃ Gain Control┃ Optional┃ ┗━━━━━━━━┻━━━━━━━┛ Brief description of MPGE-2 AAC module Figure 1.1 and Figure 1.2 show the basic structure of MPEG-2 . As Table 1 points out, the decoder includes mandatory and optional modules, see Figure 1.2. The flow of data in the figure is from left to right and from top to bottom. The task of the decoder is to find out the description of the quantized audio spectrum in the bit stream, solve the quantized value and other reconstruction information, restore the quantized spectrum, and process the recovered spectrum through the available modules in the bit stream, so as to approximate the input bit stream. The actual signal spectrum, and finally transform the spectral value from the frequency domain to the time domain, where the optional gain control module is available or not. After the initialization of the reconstruction and the calibration of the spectrum reconstruction, a series of optional modules are provided to correct one or more spectrums, so that the coding efficiency is higher. For each optional block that operates in the frequency domain, the default option is "pass". In any case, when this option is omitted, the spectral signal at its input is passed through the block without modification.

GB/T 17975.7-2002 history

• 2002 GB/T 17975.7-2002 Information technology--Generic coding of moving pictures and associated audio information Part 7: Advanced audio coding
• 2002 GB/T 17975.7-2000 Information technology-Generic coding of moving picture and associated audio information-Part 7:Advanced audio coding

GB/T 17975.7-2002 -All Parts