Editing MPEG-2 (section)

===Audio===
MPEG-2 introduces new audio encoding methods compared to MPEG-1:<ref name="mpeg-audio">{{cite web | url=http://mpeg.chiariglione.org/faq/audio.htm | title=MPEG Audio FAQ Version 9 - MPEG Audio | author=D. Thom, H. Purnhagen, and the MPEG Audio Subgroup | date=October 1998 | access-date=2009-10-31 | url-status=live | archive-url=https://web.archive.org/web/20110807233226/http://mpeg.chiariglione.org/faq/audio.htm | archive-date=2011-08-07 }}</ref>

==== MPEG-2 Part 3 ====
{{Main|MPEG-2 Part 3}}

MPEG-2 Part 3 (ISO/IEC 13818-3), titled ''Audio'', enhances [[MPEG-1]]'s audio by allowing the coding of audio programs with more than two [[surround sound|channel]]s, up to 5.1 multichannel. This method is backwards-compatible with MPEG-1, allowing MPEG-1 audio decoders to decode the two main stereo components of the presentation.<ref name="mpeg-2-layer-1-2">{{cite web | url=http://mpeg.chiariglione.org/technologies/mpeg-2/mp02-aud/index.htm | title=MPEG-2 Audio Layer I/II | author1=Werner Oomen | author2=Leon van de Kerkhof | publisher=chiariglione.org | access-date=2009-12-29 | url-status=live | archive-url=https://web.archive.org/web/20100430183150/http://mpeg.chiariglione.org/technologies/mpeg-2/mp02-aud/index.htm | archive-date=2010-04-30 }}</ref> This extension is called [[MPEG Multichannel]] or MPEG-2 BC (backwards-compatible).<ref name="mpeg-audio-faq-bc">{{cite web | url=http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm | title=MPEG Audio FAQ Version 9 - MPEG-1 and MPEG-2 BC | author=ISO | date=October 1998 | publisher=ISO | access-date=2009-10-28 | url-status=live | archive-url=https://web.archive.org/web/20100218081343/http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm | archive-date=2010-02-18 }}</ref><ref name="mpeg-bc">{{cite web | url=http://www.mpeg.org/MPEG/audio/aac.html | title=AAC | author=MPEG.ORG | access-date=2009-10-28 | url-status=dead | archive-url=https://web.archive.org/web/20070831110756/http://www.mpeg.org/MPEG/audio/aac.html | archive-date=2007-08-31 }}</ref><ref name="iso13818-7-2006-pdf">{{citation | url=http://webstore.iec.ch/preview/info_isoiec13818-7%7Bed4.0%7Den.pdf | title=ISO/IEC 13818-7, Fourth edition, Part 7 - Advanced Audio Coding (AAC) | author=ISO | date=2006-01-15 | access-date=2009-10-28 | url-status=live | archive-url=https://web.archive.org/web/20090306055335/http://webstore.iec.ch/preview/info_isoiec13818-7%7Bed4.0%7Den.pdf | archive-date=2009-03-06 }}</ref><ref name="iso13818-7-2004-pdf">{{citation|url=http://jongyeob.com/moniwiki/pds/upload/13818-7.pdf |archive-url=https://web.archive.org/web/20110713115817/http://jongyeob.com/moniwiki/pds/upload/13818-7.pdf |url-status=dead |archive-date=2011-07-13 |title=ISO/IEC 13818-7, Third edition, Part 7 - Advanced Audio Coding (AAC) |author=ISO |date=2004-10-15 |access-date=2009-10-19 }}</ref>

MPEG-2 Part 3 also defines additional bit rates and sampling rates for MPEG-1 Audio Layers I, II, and III.<ref>Predrag Supurovic, [https://www.datavoyage.com/mpgscript/mpeghdr.htm MPEG Audio Frame Header], Retrieved on 2009-07-11</ref> This extension is known as MPEG-2 LSF (low sampling frequencies), since the new sampling rates are one-half multiples (16, 22.05 and 24&nbsp;kHz) of the sampling rates defined in MPEG-1 (32, 44.1 and 48&nbsp;kHz).

==== MPEG-2 Part 7 ====
{{Main|Advanced Audio Coding}}

MPEG-2 Part 7 (ISO/IEC 13818-7), titled ''Advanced Audio Coding (AAC)'' specifies a rather different, non-backwards-compatible audio format.<ref name="iso13818-7-2006-pdf" /> This format is most commonly called Advanced Audio Coding (AAC), but was originally called MPEG-2 NBC (non-backwards-compatible).<ref name="mpeg-audio-faq-bc" /><ref name="mpeg-bc" /><ref name="mpeg-audio-florence">{{cite web|url=http://mpeg.chiariglione.org/meetings/firenze/prfloren.htm |title=Florence Press Release |author=ISO |date=March 1996 |publisher=ISO |access-date=2009-10-28 |url-status=dead |archive-url=https://web.archive.org/web/20100408061828/http://mpeg.chiariglione.org/meetings/firenze/prfloren.htm |archive-date=2010-04-08 }}</ref>

AAC is more efficient than the previous MPEG audio standards, and is in some ways less complicated than its predecessor, [[MPEG-1#Layer III|MPEG-1 Part 3 Audio Layer 3]], in that it does not have the hybrid filter bank. It supports from 1 to 48 channels at sampling rates of 8 to 96&nbsp;kHz, with multichannel, multilingual, and multiprogram capabilities.<ref name="mpeg-audio"/>

AAC is also defined in [[MPEG-4 Part 3]].{{Citation needed|date=August 2023}}