MPEG-1 Audio Layer I
Encyclopedia
MPEG-1 Audio Layer I, commonly abbreviated to MP1, is one of three audio formats included in the MPEG-1
standard. While supported by most media players, the codec is considered largely outdated, and replaced by MP2
or MP3
.
For files only containing MP1 audio, the file extension .mp1 is used.
MPEG-1 Layer I is defined in ISO/IEC 11172-3, which first version was published in 1993.
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.
MP1 uses a comparatively simple sub-band coding
, using 32 sub-bands.
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 44.1kHz 16 bits 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-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 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...
standard. While supported by most media players, the codec is considered largely outdated, and replaced by MP2
MPEG-1 Audio Layer II
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...
or MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
.
For files only containing MP1 audio, the file extension .mp1 is used.
MPEG-1 Layer I is defined in ISO/IEC 11172-3, which first version was published in 1993.
- Sampling rates: 32, 44.1 and 48 kHz
- Bitrates: 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416 and 448 kbit/s
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
MP1 uses a comparatively simple sub-band coding
Sub-band coding
Sub-band coding is any form of transform coding that breaks a signal into a number of different frequency bands and encodes each one independently. This decomposition is often the first step in data compression for audio and video signals....
, using 32 sub-bands.
MPEG-1 layer I was also used by the Digital Compact Cassette
Digital Compact Cassette
Digital Compact Cassette was a magnetic tape sound recording format introduced by Philips and Matsushita in late 1992 and pitched as a successor to the standard analog cassette. It was also a direct competitor to Sony's MiniDisc but neither format toppled the then ubiquitous analog 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 44.1kHz 16 bits 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.