Editing MPEG-2 (section)

==Main characteristics==
MPEG-2 is widely used as the format of [[digital television]] signals that are broadcast by [[terrestrial television|terrestrial]] (over-the-air), [[Cable television|cable]], and [[direct broadcast satellite]] [[Television|TV]] systems. It also specifies the format of movies and other programs that are distributed on [[DVD]] and similar discs. [[TV stations]], [[TV receiver]]s, DVD players, and other equipment are often designed to this standard. MPEG-2 was the second of several standards developed by the Moving Pictures Expert Group ([[MPEG]]) and is an international standard ('''[[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] 13818''', titled ''Information technology — Generic coding of moving pictures and associated audio information''). Parts 1 and 2 of MPEG-2 were developed in a collaboration with [[ITU-T]], and they have a respective catalog number in the ITU-T Recommendation Series.

While MPEG-2 is the core of most digital television and DVD formats, it does not completely specify them. Regional institutions can adapt it to their needs by restricting and augmenting aspects of the standard. See [[H.262/MPEG-2 Part 2#Video profiles and levels|Video profiles and levels]].

===Systems===
{{see also|MPEG program stream|MPEG transport stream}}

MPEG-2 Part 1 (ISO/IEC 13818-1 and ITU-T Rec. H.222.0<ref name="H.222.0">{{cite web |url=http://www.itu.int/rec/T-REC-H.222.0 |title=H.222.0 : Information technology - Generic coding of moving pictures and associated audio information: Systems |author=ITU-T |access-date=2010-06-03 |url-status=live |archive-url=https://web.archive.org/web/20120903192809/http://www.itu.int/rec/T-REC-H.222.0 |archive-date=2012-09-03 }}</ref><ref>{{cite web |url=http://www.itu.int/dms_pubrec/itu-t/rec/h/T-REC-H.222.0-200605-I!!SUM-HTM-E.htm |title=H.222.0 Summary |author=ITU-T |date=May 2006 |access-date=2010-06-03 |url-status=dead |archive-url=https://web.archive.org/web/20110519041216/http://www.itu.int/dms_pubrec/itu-t/rec/h/T-REC-H.222.0-200605-I!!SUM-HTM-E.htm |archive-date=2011-05-19 }}</ref>), titled ''Systems'', defines two distinct, but related, [[Digital container format|container formats]]. One is the ''transport stream'', a data packet format designed to transmit one data packet in four [[Asynchronous Transfer Mode|ATM]] data packets for streaming digital video and audio over fixed or mobile transmission mediums, where the beginning and the end of the stream may not be identified, such as [[radio frequency]], [[Electrical cable|cable]] and linear recording mediums, examples of which include [[ATSC]]/[[Digital Video Broadcasting|DVB]]/[[ISDB]]/[[SBTVD]] broadcasting, and [[HDV]] recording on tape. The other is the ''program stream'', an extended version of the [[MPEG-1#Part 1: Systems|MPEG-1]] container format with less overhead than ''transport stream''. ''Program stream'' is designed for random access storage mediums such as [[hard disk drive]]s, [[optical disc]]s and [[flash memory]].

''Transport stream'' file formats include [[M2TS]], which is used on [[Blu-ray]] discs, [[AVCHD]] on re-writable DVDs and [[HDV]] on [[compact flash]] cards. ''Program stream'' files include [[VOB]] on [[DVD]]s and [[Enhanced VOB]] on the short lived [[HD DVD]]. The standard MPEG-2 ''transport stream'' contains packets of 188 bytes. M2TS prepends each packet with 4 bytes containing a 2-bit copy permission indicator and 30-bit timestamp.

[[International Organization for Standardization|ISO]] authorized the "[[SMPTE]] Registration Authority, LLC" as the registration authority for MPEG-2 format identifiers. The registration descriptor of MPEG-2 transport is provided by ISO/IEC 13818-1 in order to enable users of the standard to unambiguously carry data when its format is not necessarily a recognized international standard. This provision will permit the MPEG-2 transport standard to carry all types of data while providing for a method of unambiguous identification of the characteristics of the underlying private data.<ref>[http://smpte-ra.org/mpegreg/mpeg.html SMPTE Registration Authority, LLC - registration authority for MPEG-2 format identifiers] {{webarchive|url=https://web.archive.org/web/20100128120057/http://www.smpte-ra.org/mpegreg/mpeg.html |date=2010-01-28 }} Retrieved on 2009-07-06</ref>

===Video===
{{Main|H.262/MPEG-2 Part 2}}

MPEG-2 Part 2 (ISO/IEC 13818-2 and ITU-T Rec. H.262), titled ''Video'', is similar to the previous [[MPEG-1#Part 2: Video|MPEG-1 Part 2]] standard, but adds support for [[interlaced video]], the format used by analog broadcast TV systems. MPEG-2 video is not optimized for low [[bit rate]]s, especially less than 1&nbsp;Mbit/s at [[standard-definition]] resolutions. All standards-compliant MPEG-2 Video decoders are fully capable of playing back MPEG-1 Video streams conforming to the constrained parameters bitstream (CPB) limits.

With some enhancements, MPEG-2 Video and Systems are also used in some [[High-definition television|HDTV]] transmission systems, and is the standard format for over-the-air [[ATSC]] digital television.<ref>{{Cite web |date=2022-07-21 |title=MPEG Standards- Know what video format to choose |url=https://www.captioningstar.com/blog/mpeg-standards-know-what-video-format-to-choose-mpeg-2-or-mpeg-4/,%20https://www.captioningstar.com/blog/mpeg-standards-know-what-video-format-to-choose-mpeg-2-or-mpeg-4/ |access-date=2024-06-28 |language=en-US}}</ref>

===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}}