General Layout of MPEG-1 Audio Elementary Stream
The digitized sound signal is divided up into blocks of 384 samples in Layer I and 1152 samples in Layers II and III. The sound sample block is encoded within an audio frame:
- header
- error check
- audio data
- ancillary data
The header of a frame contains general information such as the MPEG Layer, the sampling frequency, the number of channels, whether the frame is CRC protected, whether the sound is the original:
| Field Name | # of bits | Description |
|---|---|---|
| sync word | 12 | 0xFFF |
| ID | 1 | '1'=mpeg1 '0'=mpeg2 |
| layer | 2 | '11'=1 '10'=2 '01'=3 |
| no protection | 1 | '0'=Protected by CRC (16bit CRC follows header) '1'=Not Protected |
| bit rate index | 4 | |
| sampling frequency | 2 | kHz '00'=44.1 '01'=48 '10'=32 |
| padding | 1 | |
| private | 1 | |
| mode | 2 | '00'=Stereo '01'=joint stereo '10'=dual channel '11'=single channel |
| mode extension | 2 | |
| copyright | 1 | 0=none 1=yes |
| original or copy | 1 | 0=copy 1=original |
| emphasis | 2 |
Although most of this information may be the same for all frames, MPEG decided to give each audio frame such a header in order to simplify synchronization and bitstream editing.
Read more about this topic: Elementary Stream
Famous quotes containing the words general, elementary and/or stream:
“The general so likes your music, that he desires you for love’s sake to make no more noise with it.”
—William Shakespeare (1564–1616)
“As if paralyzed by the national fear of ideas, the democratic distrust of whatever strikes beneath the prevailing platitudes, it evades all resolute and honest dealing with what, after all, must be every healthy literature’s elementary materials.”
—H.L. (Henry Lewis)
“In contrast to the flux and muddle of life, art is clarity and enduring presence. In the stream of life, few things are perceived clearly because few things stay put. Every mood or emotion is mixed or diluted by contrary and extraneous elements. The clarity of art—the precise evocation of mood in the novel, or of summer twilight in a painting—is like waking to a bright landscape after a long fitful slumber, or the fragrance of chicken soup after a week of head cold.”
—Yi-Fu Tuan (b. 1930)