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MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively)[1] without excessive quality loss, making Video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) possible.[2][3]
Today, MPEG-1 has become the most widely compatible lossy audio/video format in the world, and is used in a large number of products and technologies. Perhaps the best-known part of the MPEG-1 standard is the MP3 audio format it introduced.
The MPEG-1 standard is published as ISO/IEC-11172. The standard consists of the following five Parts:
Systems (storage and synchronization of video, audio, and other data together)
Video (compressed video content)
Audio (compressed audio content)
Conformance testing (testing the correctness of implementations of the standard)
Reference software (example software showing how to encode and decode according to the standard)


History

Modeled on the successful collaborative approach and the compression technologies developed by the Joint Photographic Experts Group and CCITT's Experts Group on Telephony (creators of the JPEG image compression standard and the H.261 standard for video conferencing respectively) the Moving Picture Experts Group (MPEG) working group was established in January 1988. MPEG was formed to address the need for standard video and audio formats, and build on H.261 to get better quality through the use of more complex encoding methods.[2][4]
Development of the MPEG-1 standard began in May 1988. 14 video and 14 audio codec proposals were submitted by individual companies and institutions for evaluation. The codecs were extensively tested for computational complexity and subjective (human perceived) quality, at data rates of 1.5 Mbit/s. This specific bitrate was chosen for transmission over T-1/E-1 lines and as the approximate data rate of audio CDs.[5] The codecs that excelled in this testing were utilized as the basis for the standard and refined further, with additional features and other improvements being incorporated in the process.[6]
After 20 meetings of the full group in various cities around the world, and 4½ years of development and testing, the final standard (for parts 1-3) was approved in early November 1992 and published a few months later.[7] The reported completion date of the MPEG-1 standard, varies greatly: a largely complete draft standard was produced in September 1990, and from that point on, only minor changes were introduced.[2] The draft standard was publicly available for purchase.[8] The standard was finished with the 6 November 1992 meeting[9]. The Berkeley Plateau Multimedia Research Group developed a MPEG-1 decoder in November 1992.[10] In July 1990, before the first draft of the MPEG-1 standard had even been written, work began on a second standard, MPEG-2,[11] intended to extend MPEG-1 technology to provide full broadcast-quality video (as per CCIR 601) at high bitrates (3 - 15 Mbit/s), and support for interlaced video.[12] Due in part to the similarity between the two codecs, the MPEG-2 standard includes full backwards compatibility with MPEG-1 video, so any MPEG-2 decoder can play MPEG-1 videos.[13]
Notably, the MPEG-1 standard very strictly defines the bitstream, and decoder function, but does not define how MPEG-1 encoding is to be performed (although a reference implementation is provided in ISO/IEC-11172-5).[1] This means that MPEG-1 coding efficiency can drastically vary depending on the encoder used, and generally means that newer encoders perform significantly better than their predecessors.[14] The first three parts (Systems, Video and Audio) of ISO/IEC 11172 were published in August 1993.

Patents

MPEG-1 video and Layer I/II audio may be able to be implemented without payment of license fees.[16][17] [18][19][20] The ISO patent database lists one patent for ISO 11172, US 4,472,747, which expired in 2003.[21] The near-complete draft of the MPEG-1 standard was publicly available as ISO CD 11172[8] by December 6, 1991.[22] Due to its age, many of the patents on the technology have expired. Neither the Kuro5hin article "Patent Status of MPEG-1,H.261 and MPEG-2"[23] nor a thread on the gstreamer-devel[24] mailing list were able to list a single unexpired MPEG-1 video and Layer I/II audio patent. A full MPEG-1 decoder and encoder can not be implemented royalty free since there are companies that require patent fees for implementations of MPEG-1 Layer 3 Audio however.

Applications

• Most popular computer software for video playback includes MPEG-1 decoding, in addition to any other supported formats.

• The popularity of MP3 audio has established a massive installed base of hardware that can playback MPEG-1 Audio (all 3 layers).

• "Virtually all digital audio devices" can playback MPEG-1 Audio.[25] Many millions have been sold to-date.

• Before MPEG-2 became widespread, many digital satellite/cable TV services used MPEG-1 exclusively.[4][14]

• The widespread popularity of MPEG-2 with broadcasters means MPEG-1 is playable by most digital cable and satellite set-top boxes, and digital disc and tape players, due to backwards compatibility.

• MPEG-1 is the exclusive video and audio format used on Video CD (VCD), the first consumer digital video format, and still a very popular format around the world.

• The Super Video CD standard, based on VCD, uses MPEG-1 Audio exclusively, as well as MPEG-2 video.

• The DVD-Video format uses MPEG-2 video primarily, but MPEG-1 support is explicitly defined in the standard.

• The DVD Video standard originally required MPEG-1 Layer II audio for PAL countries, but was changed to allow AC-3/Dolby Digital-only discs. MPEG-1 Layer II audio is still allowed on DVDs, although newer extensions to the format, like MPEG Multichannel, are rarely supported.

• Most DVD players also support Video CD and MP3 CD playback, which use MPEG-1.

• The international Digital Video Broadcasting (DVB) standard primarily uses MPEG-1 Layer II audio, and MPEG-2 video.

• The international Digital Audio Broadcasting (DAB) standard uses MPEG-1 Layer II audio exclusively, due to MP2's especially high quality, modest decoder performance requirements, and tolerance of errors.