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Chapter 11. General Audio Coding > MPEG-2 Advanced Audio Coding

11.2. MPEG-2 Advanced Audio Coding

After the completion of the MPEG-2 multichannel audio standard in 1994 [MPEG2-3], the MPEG Audio subgroup started another standardization effort to define a multichannel coding standard allowing a higher quality than is achievable while requiring MPEG-1 backward compatibility, as was the case for the first MPEG-2 multichannel audio standard. The aim of this development, initially called the MPEG-2 Non-Backward Compatible (NBC) coding scheme [BBQF97], was to reach indistinguishable quality according to the EBU definition [N1419] at bit rates of 384 kbit/s or lower for five full bandwidth channel signals. The standardization process was successfully completed in 1997, renamed MPEG-2 Advanced Audio Coding (MPEG-2 AAC) subsequently, and became Part 7 of the MPEG-2 standard (ISO/IEC 13818-7) [AAC].

In formal verification tests, MPEG-2 AAC demonstrated near-transparent subjective audio quality at a bit rate of 256 to 320 kbit/s for five channels [KirW97] and at 96 to 128 kbit/s for stereophonic signals [N2006]. Although originally designed for near-transparent audio coding, testing inside MPEG revealed that the coder exhibits excellent performance also at very low bit rates down to 16 kbit/s. As a result, MPEG-2 AAC was adopted as the core of the MPEG-4 General Audio (T/F) coder [MPEG4-3].


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