Editing MPEG-4 Part 3 (section)

==Bifurcation in the AAC technical standard==
{{Main|Advanced Audio Coding}}
The [[Advanced Audio Coding]] in MPEG-4 Part 3 (MPEG-4 Audio) Subpart 4 was enhanced relative to the previous standard [[MPEG-2]] Part 7 (Advanced Audio Coding), in order to provide better [[sound quality]] for a given encoding bitrate.

It is assumed that any Part 3 and Part 7 differences will be ironed out by the ISO standards body in the near future to avoid the possibility of future bitstream incompatibilities. At present<!-- ? --> there are no known player or codec incompatibilities due to the newness of the standard.

The MPEG-2 Part 7 standard (Advanced Audio Coding) was first published in 1997 and offers three default profiles:<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 |page=32 |date=2004-10-15 |access-date=2009-10-19 }}</ref><ref name="iso13818-7-1997">{{cite web | url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=25040 | title=ISO/IEC 13818-7:1997, Information technology -- Generic coding of moving pictures and associated audio information -- Part 7: Advanced Audio Coding (AAC) | author=ISO | year=1997 | access-date=2009-10-19 }}</ref> Low Complexity profile (LC), Main profile and Scalable Sampling Rate profile (SSR).

The MPEG-4 Part 3 Subpart 4 (General Audio Coding) combined the profiles from MPEG-2 Part 7 with Perceptual Noise Substitution (PNS) and defined them as Audio Object Types (AAC LC, AAC Main, AAC SSR).<ref name="mpeg4audio-profiles" />