MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM) is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III (MP3). While MP3 is much more popular for PC and Internet applications, MP2 remains a dominant standard for audio broadcasting.
|MPEG-1 or MPEG-2 Audio Layer 2|
|Internet media type|
|Type of format||Audio compression format, audio file format|
|Standard||ISO/IEC 11172-3, |
MPEG-1 Audio Layer 2 encoding was derived from the MUSICAM (Masking pattern adapted Universal Subband Integrated Coding And Multiplexing) audio codec, developed by Centre commun d'études de télévision et télécommunications (CCETT), Philips, and the Institut für Rundfunktechnik (IRT) in 1989 as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of a system for the broadcasting of audio and data to fixed, portable or mobile receivers (established in 1987).
It began as the Digital Audio Broadcast (DAB) project managed by Egon Meier-Engelen of the Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt (later on called Deutsches Zentrum für Luft- und Raumfahrt, German Aerospace Center) in Germany. The European Community financed this project, commonly known as EU-147, from 1987 to 1994 as a part of the EUREKA research program.
The Eureka 147 System comprised three main elements: MUSICAM Audio Coding (Masking pattern Universal Sub-band Integrated Coding And Multiplexing), Transmission Coding & Multiplexing and COFDM Modulation.
MUSICAM was one of the few codecs able to achieve high audio quality at bit rates in the range of 64 to 192 kbit/s per monophonic channel. It has been designed to meet the technical requirements of most applications (in the field of broadcasting, telecommunication and recording on digital storage media) — low delay, low complexity, error robustness, short access units, etc.
As a predecessor of the MP3 format and technology, the perceptual codec MUSICAM is based on integer arithmetics 32 subbands transform, driven by a psychoacoustic model. It was primarily designed for Digital Audio Broadcasting and digital TV, and disclosed by CCETT(France) and IRT (Germany) in Atlanta during an IEEE-ICASSP conference. This codec incorporated into a broadcasting system using COFDM modulation was demonstrated on air and on the field  together with Radio Canada and CRC Canada during the NAB show (Las Vegas) in 1991. The implementation of the audio part of this broadcasting system was based on a two chips encoder (one for the subband transform, one for the psychoacoustic model designed by the team of G. Stoll (IRT Germany), later known as Psychoacoustic model I in the ISO MPEG audio standard) and a real time decoder using one Motorola 56001 DSP chip running an integer arithmetics software designed by Y.F. Dehery's team (CCETT, France). The simplicity of the corresponding decoder together with the high audio quality of this codec using for the first time a 48 kHz sampling frequency, a 20 bits/sample input format (the highest available sampling standard in 1991, compatible with the AES/EBU professional digital input studio standard) were the main reasons to later adopt the characteristics of MUSICAM as the basic features for an advanced digital music compression codec such as MP3.
The audio coding algorithm used by the Eureka 147 Digital Audio Broadcasting (DAB) system has been subject to the standardization process within the ISO/Moving Pictures Expert Group (MPEG) in 1989–94. MUSICAM audio coding was used as a basis for some coding schemes of MPEG-1 and MPEG-2 Audio. Most key features of MPEG-1 Audio were directly inherited from MUSICAM, including the filter bank, time-domain processing, audio frame sizes, etc. However, improvements were made, and the actual MUSICAM algorithm was not used in the final MPEG-1 Layer II audio standard.
Since the finalisation of MPEG-1 Audio and MPEG-2 Audio (in 1992 and 1994), the original MUSICAM algorithm is not used anymore. The name MUSICAM is often mistakenly used when MPEG Audio Layer II is meant. This can lead to some confusion, because the name MUSICAM is trademarked by different companies in different regions of the world. (Musicam is the name used for MP2 in some specifications for Astra Digital Radio as well as in the BBC's DAB documents.)
The Eureka Project 147 resulted in the publication of European Standard, ETS 300 401 in 1995, for DAB which now has worldwide acceptance. The DAB standard uses the MPEG-1 Audio Layer II (ISO/IEC 11172-3) for 48 kHz sampling frequency and the MPEG-2 Audio Layer II (ISO/IEC 13818-3) for 24 kHz sampling frequency.
In the late 1980s, ISO's Moving Picture Experts Group (MPEG) started an effort to standardize digital audio and video encoding, expected to have a wide range of applications in digital radio and TV broadcasting (later DAB, DMB, DVB), and use on CD-ROM (later Video CD). The MUSICAM audio coding was one of 14 proposals for MPEG-1 Audio standard that were submitted to ISO in 1989.
The MPEG-1 Audio standard was based on the existing MUSICAM and ASPEC audio formats. The MPEG-1 Audio standard included the three audio "layers" (encoding techniques) now known as Layer I (MP1), Layer II (MP2) and Layer III (MP3). All algorithms for MPEG-1 Audio Layer I, II and III were approved in 1991 as the committee draft of ISO-11172 and finalized in 1992 as part of MPEG-1, the first standard suite by MPEG, which resulted in the international standard ISO/IEC 11172-3 (a.k.a. MPEG-1 Audio or MPEG-1 Part 3), published in 1993. Further work on MPEG audio was finalized in 1994 as part of the second suite of MPEG standards, MPEG-2, more formally known as international standard ISO/IEC 13818-3 (a.k.a. MPEG-2 Part 3 or backward compatible MPEG-2 Audio or MPEG-2 Audio BC), originally published in 1995. MPEG-2 Part 3 (ISO/IEC 13818-3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sampling rates are exactly half that of those originally defined for MPEG-1 Audio. MPEG-2 Part 3 also enhanced MPEG-1's audio by allowing the coding of audio programs with more than two channels, up to 5.1 multichannel.
The Layer III (MP3) component uses a lossy compression algorithm that was designed to greatly reduce the amount of data required to represent an audio recording and sound like a decent reproduction of the original uncompressed audio for most listeners.
CCETT (France), IRT (Germany) and Philips (The Netherlands) won an Emmy Award in Engineering 2000 for development of a digital audio two-channel compression system known as Musicam or MPEG Audio Layer II.
MPEG-1 Audio Layer II is defined in ISO/IEC 11172-3 (MPEG-1 Part 3)
The format is based on successive digital frames of 1152 sampling intervals with four possible formats:
MPEG audio may have variable bit rate (VBR), but it is not widely supported. Layer II can use a method called bit rate switching. Each frame may be created with a different bit rate. According to ISO/IEC 11172-3:1993, Section 126.96.36.199: To provide the smallest possible delay and complexity, the (MPEG audio) decoder is not required to support a continuously variable bit rate when in layer I or II.
Layer II is commonly used within the broadcast industry for distributing live audio over satellite, ISDN and IP Network connections as well as for storage of audio in digital playout systems. An example is NPR's PRSS Content Depot programming distribution system. The Content Depot distributes MPEG-1 L2 audio in a Broadcast Wave File wrapper. MPEG2 with RIFF headers (used in .wav) is specified in the RIFF/WAV standards. As a result, Windows Media Player will directly play Content Depot files, however, less intelligent .wav players often do not. As the encoding and decoding process would have been a significant drain on CPU resources in the first generations of broadcast playout systems, professional broadcast playout systems typically implement the codec in hardware, such as by delegating the task of encoding and decoding to a compatible soundcard rather than the system CPU.
All DVD-Video players in PAL countries contain stereo MP2 decoders, making MP2 a possible competitor to Dolby Digital in these markets. DVD-Video players in NTSC countries are not required to decode MP2 audio, although most do. While some DVD recorders store audio in MP2 and many consumer-authored DVDs use the format, commercial DVDs with MP2 soundtracks are rare.
MPEG 1 layer 2 is the standard audio format used in the MHP standard for set-top boxes.
MPEG 1 layer 2 is the audio format used in HDV camcorders.
MP2 files are compatible with some Portable audio players.
The term MP2 and filename extension .mp2 usually refer MPEG-1 Audio Layer II data, but can also refer to MPEG-2 Audio Layer II, a mostly backward compatible extension which adds support for multichannel audio, variable bit rate encoding, and additional sampling rates, defined in ISO/IEC 13818-3. The abbreviation MP2 is also sometimes erroneously applied to MPEG-2 video or MPEG-2 AAC audio.
2K resolution is a horizontal resolution of approximately 2,000 pixels on a display device or content. Digital Cinema Initiatives (DCI) defines 2K resolution standard as 2048×1080.In the movie projection industry, DCI is the dominant standard for 2K output.480i
480i is a shorthand name for the video mode used for standard-definition analog or digital television in Caribbean, Myanmar, Japan, South Korea, Taiwan, Philippines, Laos, Western Sahara, and most of the Americas (with the exception of Argentina, Paraguay and Uruguay). The 480 identifies a vertical resolution of 480 lines, and the i identifies it as an interlaced resolution. The field rate, which is 60 Hz (or 59.94 Hz when used with NTSC color), is sometimes included when identifying the video mode, i.e. 480i60; another notation, endorsed by both the International Telecommunication Union in BT.601 and SMPTE in SMPTE 259M, includes the frame rate, as in 480i/30. The other common standard, used in the other parts of the world, is 576i.
In analogue contexts, this resolution is often called "525 lines". It is mandated by CCIR Systems M and J, which are usually paired with NTSC color - which led to the "NTSC" name being often inaccurately used to refer to this video mode. Other color encodings have also been used with System M, notably PAL-M in Brazil.480p
480p is the shorthand name for a family of video display resolutions. The p stands for progressive scan, i.e. non-interlaced. The 480 denotes a vertical resolution of 480 pixels, usually with a horizontal resolution of 640 pixels and 4:3 aspect ratio (480 × 4⁄3 = 640) or a horizontal resolution of 854 or less (848 should be used for mod16 compatibility) pixels for an approximate 16:9 aspect ratio (480 × 16⁄9 = 853.3). Since a pixel count must be a whole number, in Wide VGA displays it is generally rounded up to 854 to ensure inclusion of the entire image. The frames are displayed progressively as opposed to interlaced. 480p was used for many early Plasma televisions. Standard definition has always been a 4:3 aspect ratio with a pixel resolution of 640 × 480 pixels.576p
576p is the shorthand name for a video display resolution. The p stands for progressive scan, i.e. non-interlaced, the 576 for a vertical resolution of 576 pixels, usually with a horizontal resolution of 720 or 704 pixels. The frame rate can be given explicitly after the letter.CCIR System G
CCIR System G is an analog broadcast television system used in many countries. There are several systems in use and letter G is assigned for the European UHF system which is also used in the majority of Asian and African countries. (However some countries in Europe use different systems.)CCIR System H
CCIR System H is an analog broadcast television system primarily used in Belgium, the Balkans and Malta on the UHF bands.DVR-MS
DVR-MS (Microsoft Digital Video Recording) is a proprietary video and audio file container format, developed by Microsoft used for storing TV content recorded by Windows XP Media Center Edition, Windows Vista and Windows 7.
Multiple data streams (audio and video) are wrapped in an ASF container with the extension DVR-MS. Video is encoded using the MPEG-2 standard and audio using MPEG-1 Audio Layer II or Dolby Digital AC-3 (ATSC A/52). The format extends these standards by including metadata about the content and digital rights management. Files in this format are generated from the Stream Buffer Engine (SBE.dll), a DirectShow component introduced in Windows XP Service Pack 1.Dolby AC-4
Dolby AC-4 is an audio compression technology developed by Dolby Laboratories. Dolby AC-4 bitstreams can contain audio channels and/or audio objects. Dolby AC-4 has been adopted by the DVB project and standardized by the ETSI.GTV (Australian TV station)
GTV is a commercial television station in Melbourne, Australia, owned by the Nine Network. The station is currently based at a new high-tech, purpose-built studio at 717 Bourke Street, Docklands.Ghost-canceling reference
Ghost-canceling reference (GCR) is a special sub-signal on a television channel that receivers can use to attenuate the ghosting effect of a television signal split into multiple paths between transmitter and receiver.
In the United States, the GCR signal is a chirp in frequency of the modulating signal from 0 Hz to 4.2 MHz, transmitted during the vertical blanking interval over one video line (line 19 in the U.S.), shifted in phase by 180° once per frame, with this pattern inverted every four lines. Television receivers generate their own local versions of this signal, and use the comparison between the local and remote signals to tune out any ghost images on the screen.
GCR was introduced after its recommendation in 1993 by the Advanced Television Systems Committee.MPEG-1 Audio Layer I
MPEG-1 Audio Layer I, commonly abbreviated to MP1, is one of three audio formats included in the MPEG-1 standard. It is a deliberately simplified version of MPEG-1 Audio Layer II, created for applications where lower compression efficiency could be tolerated in return for a less complex algorithm that could be executed with simpler hardware requirements. While supported by most media players, the codec is considered largely obsolete, and replaced by MP2 or MP3.
For files only containing MP1 audio, the file extension .mp1 is used.
MPEG-1 layer I was also used by the Digital Compact Cassette format, in the form of the PASC audio compression codec. Because of the need of a steady stream of frames per second on a tape-based medium, PASC uses the rarely used (and under-documented) padding bit in the MPEG header to indicate that a frame was padded with 32 extra 0-bits (four 0-bytes) to change a short 416-byte frame into 420 bytes. The varying frame size only occurs when a 44.1 kHz 16-bit stereo audio signal is encoded at 384 kilobits per second, because the bitrate of the uncompressed signal is not an exact multiple of the bitrate of the compressed bit stream.MPEG-2 Part 3
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), allowing MPEG-1 audio decoders to decode the two main stereo components of the presentation.
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 (a.k.a. MP3).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).SKY PerfecTV!
SKY PerfecTV! (スカパー!, Sukapā!) is a direct broadcast satellite (DBS) service that provides satellite television, audio programming, and interactive television services to households in Japan, owned by parent company SKY Perfect JSAT Corporation.
SKY PerfecTV! is also a direct broadcast satellite (DBS) service. While SKY PerfecTV! Premium Service use DVB-S and DVB-S2, SKY PerfecTV! Basic Service use ISDB-S.STW
STW is an Australian television station owned by the Nine Network that is based in Perth, Australia.
STW broadcasts with a transmitter mast located in Walliston. The station callsign, STW, is an acronym of Swan Television, Western Australia.TVW
TVW is a television station broadcasting in Perth, Western Australia, wholly owned by the Seven Network, whose principal owner is Perth-born Kerry Stokes. It was the first television station in Western Australia, commencing service on 16 October 1959. It broadcasts a modulated 64-QAM signal of four DVB channels (Seven Network, 7Two, 7Mate and TV4ME) on VHF channel 6 at 177.5 MHz from Bickley in the Perth Hills. The primary channel was available as a PAL-B modulated simulcast on VHF channel 7 at 182.25 MHz before being discontinued in the first half of 2013, which was the station's primary signal since its inception. The TVW callsign stands for Television Western Australia.VIT signals
In television broadcasting, VIT signals (vertical interval test signals) are a group of test signals inserted in the composite video signal. These signals are used to weight the transmission characteristics of the system between the test generator and the output of the demodulator, where the system includes the microwave links, or TVROs as well as the TV transmitters and the transposers. There are both ATSC and EBU standards for VIT. (Because analogue television is being phased out globally, VIT standards are considered superseded.)VOB
VOB (Video Object) is the container format in DVD-Video media. VOB can contain digital video, digital audio, subtitles, DVD menus and navigation contents multiplexed together into a stream form. Files in VOB format may be encrypted.White Book (CD standard)
The White Book refers to a standard of compact disc that stores not only sound but also still pictures and motion video. It was released in 1993 by Sony, Philips, Matsushita, and JVC. These discs, most commonly found in Asia, are usually called "Video CDs" (VCD). In some ways, VCD can be thought of as the successor to the Laserdisc and the predecessor to DVD. Note that Video CD should not be confused with CD Video which was an earlier and entirely different format.
Several extensions to the White Book were published in later years: VCD 2.0 in 1995, VCD-Internet in 1997, and Super Video CD (SVCD) in 1998. The standard is not freely available and must be licensed from Philips.The White Book also defines the more general CD-i Bridge format (also called CD-Bridge or simply "bridge discs"), which are CD-ROM XA discs with an additional Green Book CD-i specific application program. The CD-ROM XA information in bridge discs can be obtained through CD-ROM drives, while CD-i players can use the CD-i program to read bridge discs as well (hence the "bridge" status between CD-ROMs and CD-i discs). Bridge discs must conform to both the CD-ROM XA and Green Book CD-i specifications. VCDs and SVCDs fall under the category of bridge discs, as do Photo CDs and Karaoke CDs.The following is a summary of the specifications for VCDs and SVCDs. For more details, see Video CD and Super Video CD.
File system: ISO 9660-compliant
Format: Mode 2, Form 2/XA
Maximum Length: Usually 74 minutes
Format: MPEG-1 Audio Layer II
Bit rate: 224 kilobits per second
Sample rate: 44,100 Hz
Number of Channels: 2 (stereo)
Format: MPEG-1 Part 2 (VCD), H.262/MPEG-2 Part 2 (SVCD)
Resolution: 352×240 pixel for NTSC video, 352×288 pixel for PAL video (VCD); 480×480 pixel for NTSC video, 480×576 for PAL video (SVCD)
Frame rate: 29.97 Hz (NTSC), 25 Hz (PAL)
Bit rate: About 1.13 Mbit/s
See Compression methods for techniques and Compression software for codecs