MPEG-1


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 about 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting practical.
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 first version of the MP3 audio format it introduced.
The MPEG-1 standard is published as ISO/IEC 11172, titled Information technology—Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s.
The standard consists of the following five Parts:
  1. Systems.
  2. Video
  3. Audio, including MP3 and MP2
  4. Conformance testing
  5. Reference software

    History

The predecessor of MPEG-1 for video coding was the H.261 standard produced by the CCITT. The basic architecture established in H.261 was the motion-compensated DCT hybrid video coding structure. It uses macroblocks of size 16×16 with block-based motion estimation in the encoder and motion compensation using encoder-selected motion vectors in the decoder, with residual difference coding using a discrete cosine transform of size 8×8, scalar quantization, and variable-length codes for entropy coding. H.261 was the first practical video coding standard, and all of its described design elements were also used in MPEG-1.
Modeled on the successful collaborative approach and the compression technologies developed by the Joint Photographic Experts Group and CCITT's Experts Group on Telephony, the Moving Picture Experts Group working group was established in January 1988, by the initiative of Hiroshi Yasuda and Leonardo Chiariglione. MPEG was formed to address the need for standard video and audio formats, and to build on H.261 to get better quality through the use of somewhat more complex encoding methods.
Development of the MPEG-1 standard began in May 1988. Fourteen video and fourteen audio codec proposals were submitted by individual companies and institutions for evaluation. The codecs were extensively tested for computational complexity and subjective 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. 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.
After 20 meetings of the full group in various cities around the world, and 4½ years of development and testing, the final standard was approved in early November 1992 and published a few months later. 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. The draft standard was publicly available for purchase. The standard was finished with the 6 November 1992 meeting. The Berkeley Plateau Multimedia Research Group developed an MPEG-1 decoder in November 1992. In July 1990, before the first draft of the MPEG-1 standard had even been written, work began on a second standard, MPEG-2, intended to extend MPEG-1 technology to provide full broadcast-quality video at high bitrates and support for interlaced video. 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.
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. 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. The first three parts of ISO/IEC 11172 were published in August 1993.
PartNumberFirst public
release date
latest
correction		TitleDescription
Part 1 19931999Systems
Part 2 19932006Video
Part 3 19931996Audio
Part 4 19952007Compliance testing
Part 5 19982007Software simulation

Patents

Due to its age, MPEG-1 is no longer covered by any essential patents and can thus be used without obtaining a licence or paying any fees. The ISO patent database lists one patent for ISO 11172, US 4,472,747, which expired in 2003. The near-complete draft of the MPEG-1 standard was publicly available as ISO CD 11172 by December 6, 1991. Neither the July 2008 Kuro5hin article "Patent Status of MPEG-1, H.261 and MPEG-2", nor an August 2008 thread on the gstreamer-devel mailing list were able to list a single unexpired MPEG-1 Video and MPEG-1 Audio Layer I/II patent. A May 2009 discussion on the whatwg mailing list mentioned US 5,214,678 patent as possibly covering MPEG-1 Audio Layer II. Filed in 1990 and published in 1993, this patent is now expired.
A full MPEG-1 decoder and encoder, with "Layer III audio", could not be implemented royalty free since there were companies that required patent fees for implementations of MPEG-1 Audio Layer III, as discussed in the MP3 article. All patents in the world connected to MP3 expired 30 December 2017, which makes this format totally free for use. On 23 April 2017, Fraunhofer IIS stopped charging for Technicolor's MP3 licensing program for certain MP3 related patents and software.

Former patent holders

The following corporations filed declarations with ISO saying they held patents for the MPEG-1 Video format, although all such patents have since expired.
  • BBC
  • Daimler Benz AG
  • Fujitsu
  • IBM
  • Matsushita Electric Industrial Co., Ltd.
  • Mitsubishi Electric
  • NEC
  • NHK
  • Philips
  • Pioneer Corporation
  • Qualcomm
  • Ricoh
  • Sony
  • Texas Instruments
  • Thomson Multimedia
  • Toppan Printing
  • Toshiba
  • Victor Company of Japan

    Applications

  • Most popular 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 play back MPEG-1 Audio.
  • "Virtually all digital audio devices" can play back MPEG-1 Audio. Many millions have been sold to-date.
  • Before MPEG-2 became widespread, many digital satellite/cable TV services used MPEG-1 exclusively.
  • 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 was used for full-screen video on Green Book CD-i, and on Video CD.
  • 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 Audio Layer II for PAL countries, but was changed to allow AC-3/Dolby Digital-only discs. MPEG-1 Audio Layer II 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 standard primarily uses MPEG-1 Audio Layer II, and MPEG-2 video.
  • The international Digital Audio Broadcasting standard uses MPEG-1 Audio Layer II exclusively, due to its especially high quality, modest decoder performance requirements, and tolerance of errors.
  • The Digital Compact Cassette uses PASC to encode its audio. PASC is an early version of MPEG-1 Audio Layer I with a fixed bit rate of 384 kilobits per second.

    Part 1: Systems

Part 1 of the MPEG-1 standard covers systems, and is defined in ISO/IEC-11172-1.
MPEG-1 Systems specifies the logical layout and methods used to store the encoded audio, video, and other data into a standard bitstream, and to maintain synchronization between the different contents. This file format is specifically designed for storage on media, and transmission over communication channels, that are considered relatively reliable. Only limited error protection is defined by the standard, and small errors in the bitstream may cause noticeable defects.
This structure was later named an MPEG program stream: "The MPEG-1 Systems design is essentially identical to the MPEG-2 Program Stream structure." This terminology is more popular, precise and will be used here.

Elementary streams, packets, and clock references

  • Elementary Streams are the raw bitstreams of MPEG-1 audio and video encoded data. These files can be distributed on their own, such as is the case with MP3 files.
  • Packetized Elementary Streams are elementary streams packetized into packets of variable lengths, i.e., divided ES into independent chunks where cyclic redundancy check checksum was added to each packet for error detection.
  • System Clock Reference is a timing value stored in a 33-bit header of each PES, at a frequency/precision of 90 kHz, with an extra 9-bit extension that stores additional timing data with a precision of 27 MHz. These are inserted by the encoder, derived from the system time clock. Simultaneously encoded audio and video streams will not have identical SCR values, however, due to buffering, encoding, jitter, and other delay.