标准编号：ISO/IEC 13818-7:2006
中文名称：信息技术 电影和辅助声频信息的普通编码 第7部分：高级声频编码（AAC）.
英文名称：Information technology — Generic coding of moving pictures and associated audio information — Part 7: Advanced Audio Coding (AAC)
发布日期：2006-01
标准范围
1 GeneralThis International Standard describes the MPEG-2 audio non-backwards compatible standard called MPEG-2Advanced Audio Coding, AAC [1], a higher quality multichannel standard than achievable while requiringMPEG-1 backwards compatibility. This MPEG-2 AAC audio standard allows for ITU-R “indistinguishable” quality according to [2] at data rates of 320 kbit/s for five full-bandwidth channel audio signals.The AAC decoding process makes use of a number of required tools and a number of optional tools. Table 1lists the tools and their status as required or optional. Required tools are mandatory in any possible profile.Optional tools may not be required in some profiles.2 MPEG-2 AAC Tools OverviewThe basic structure of the MPEG-2 AAC system is shown in Figure 1 and Figure 2. As is shown in Table 1,there are both required and optional tools in the decoder. The data flow in this diagram is from left to right, topto bottom. The functions of the decoder are to find the description of the quantized audio spectra in thebitstream, decode the quantized values and other reconstruction information, reconstruct the quantizedspectra, process the reconstructed spectra through whatever tools are active in the bitstream in order to arriveat the actual signal spectra as described by the input bitstream, and finally convert the frequency domainspectra to the time domain, with or without an optional gain control tool. Following the initial reconstruction andscaling of the spectrum reconstruction, there are many optional tools that modify one or more of the spectra inorder to provide more efficient coding. For each of the optional tools that operate in the spectral domain, theoption to “pass through” is retained, and in all cases where a spectral operation is omitted, the spectra at itsinput are passed directly through the tool without modification.The input to the bitstream demultiplexer tool is the MPEG-2 AAC bitstream. The demultiplexer separates theparts of the MPEG-AAC data stream into the parts for each tool, and provides each of the tools with thebitstream information related to that tool.
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