MPEG-2 Part 3 explained

Part 3 of the MPEG-2 standard (formally known as ISO/IEC 13818-3, also known as MPEG-2 Audio or MPEG-2 BC) defines audio coding:

• MPEG Multichannel - It enhances MPEG-1's audio by allowing the coding of audio programs with more than two channels, up to 5.1 multichannel. This method is backwards-compatible (also known as MPEG-2 BC^{[1] [2]}), allowing MPEG-1 audio decoders to decode the two main stereo components of the presentation.^[3]
• MPEG-2 Part 3 also defined additional bit rates and sample rates for MPEG-1 Audio Layer I, MPEG-1 Audio Layer II and MPEG-1 Audio Layer III (the first version of MP3).^[4]

The MPEG-2 Part 3 should not be confused with MPEG-2 Part 7: AAC a.k.a. MPEG-2 NBC (Non-Backward Compatible) - the MPEG-2 Advanced Audio Coding with support for multichannel encoding (up to 48 channels).

Overview

See main article: MPEG-1 Audio Layer I, MPEG-1 Audio Layer II, MP3 and MPEG Multichannel. MPEG-2 Part 3 introduced new audio encoding methods compared to MPEG-1 Part 3:^[5] MPEG-2 BC (backward compatible with MPEG-1 audio formats)

• low bitrate encoding with halved sampling rate (MPEG-1 Layer 1/2/3 LSF - "Low Sampling Frequencies")
• multichannel encoding with up to 5.1 channels

Notes and References

1. Web site: MPEG Audio FAQ Version 9 - MPEG-1 and MPEG-2 BC . ISO . October 1998 . ISO . 2009-10-28.
2. Web site: AAC . MPEG.ORG . 2009-10-28 . https://web.archive.org/web/20070831110756/http://www.mpeg.org/MPEG/audio/aac.html . 2007-08-31 . dead .
3. Web site: MPEG-2 Audio Layer I/II . Werner Oomen . Leon van de Kerkhof . chiariglione.org . 2009-12-29.
4. Predrag Supurovic, MPEG Audio Frame Header, Retrieved on 2009-07-11
5. Web site: MPEG Audio FAQ Version 9 - MPEG Audio . D. Thom, H. Purnhagen, and the MPEG Audio Subgroup . October 1998 . 2009-10-31.