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 (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 most media players, the codec is considered largely obsolete, and replaced by MP2 or MP3.
| Filename extension |
.mp1 |
|---|---|
| Internet media type |
audio/mpeg, audio/MPA |
| Initial release | December 6, 1991 |
| Latest release | ISO/IEC 13818-3:1998 April 1998 |
| Type of format | Lossy audio |
| Contained by | MPEG-ES |
| Standard | ISO/IEC 11172-3, ISO/IEC 13818-3 |
| 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 .mp1 is used.
A limited version of MPEG-1 layer I was also used by the Digital Compact Cassette format, 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' and sets them to zero, whereas the ISO/IEC 11172-3 standard uses them to store data.