MPEG-1 Audio Layer I,commonly abbreviated toMP1,is one of three audio formats included in theMPEG-1standard. It is a deliberately simplified version ofMPEG-1 Audio Layer II (MP2),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 mostmedia players,the codec is considered largely obsolete, and replaced by MP2 orMP3.
| Filename extension |
.mp1 |
|---|---|
| Internet media type | |
| Initial release | December 6, 1991[3] |
| Latest release | ISO/IEC 13818-3:1998 April 1998 |
| Type of format | Lossyaudio |
| Contained by | MPEG-ES |
| Standard | ISO/IEC 11172-3,[4] ISO/IEC 13818-3[5] |
| Open format? | Yes |
| Free format? | Expired patents |
| Website | http://mpeg.chiariglione.org/standards/mpeg-1/audio |
For files only containing MP1 audio, the file extension.mp1is used.
A limited version of MPEG-1 layer I was also used by theDigital Compact Cassetteformat, in the form of the PASC (Precision Adaptive Subband Coding) audio compression codec. The bit rate of PASC was fixed at 384 kilobits per second, and when encoding audio at a sample frequency of 44.1 kHz, PASC regards the padding slots as 'dummy'[6]and sets them to zero, whereas the ISO/IEC 11172-3 standard uses them to store data.
Specification
editMPEG-1 Layer I is defined in ISO/IEC 11172-3, the first version of which was published in 1993.
- Sampling rates: 32,44.1and 48 kHz
- Bitrates: 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416 and 448 kbit/s[7]
An extension has been provided in MPEG-2 Layer I and is defined in ISO/IEC 13818-3, which first version was published in 1995.
- Additional sampling rates: 16, 22.05 and 24 kHz
- Additional bitrates: 48, 56, 80, 112, 144 and 176 kbit/s[7]
MP1 uses a comparatively simplesub-band coding,using 32 sub-bands.[8]
References
edit- ^M. Nilsson (November 2000).The audio/mpeg Media Type.Network Working Group.doi:10.17487/RFC3003.RFC3003.Proposed Standard.
- ^S. Casner; P. Hoschka (July 2003).MIME Type Registration of RTP Payload Formats.Network Working Group.doi:10.17487/RFC3555.RFC3555.Obsolete.Obsoleted byRFC4855,4856.Updated byRFC3625,4629.
- ^Patel K, Smith BC, Rowe LA (1993-09-01)."Performance of a software MPEG video decoder".Proceedings of the first ACM international conference on Multimedia - MULTIMEDIA '93.ACM Multimedia. New York City: Association for Computing Machinery. pp.75–82.doi:10.1145/166266.166274.ISBN978-0-89791-596-0.S2CID3773268.Reference 3 in the paper is to Committee Draft of Standard ISO/IEC 11172, December 6, 1991.
- ^"ISO/IEC 11172-3:1993 - Information technology -- Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s -- Part 3: Audio".ISO. 1993.Retrieved2010-07-14.
- ^"ISO/IEC 13818-3:1995 - Information technology -- Generic coding of moving pictures and associated audio information -- Part 3: Audio".ISO. 1995.Retrieved2010-07-14.
- ^"Philips DCC System Description Draft".Archive.org.Philips Consumer Electronics B.V. September 1994.Retrieved14 April2021.
The padding bit [...] indicates whether the current frame has a 'dummy' slot
- ^ab"MPEG Audio Frame Header".2003-08-03. Archived fromthe originalon 2015-02-08.Retrieved2009-05-29.
- ^"MPEG-1 audio layer 1".TheFreeDictionary.