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Compressed audio means an audio file that has been reduced in size through the use of a compression algorithm. A compression algorithm extracts patterned or repetitive data, and replaces this with a data summary that can be used by a decompression algorithm to reconstruct the original file. This section describes the audio input and output formats that are handled by the Windows Media Format SDK.
This section describes the audio input and output formats that are handled by the Windows Media Audio codec.
For input, any combination of a sampling rate of 8 kilohertz (kHz), 11 kHz, 16 kHz, 22 kHz, 32 kHz, or 44 kHz, 8-bit or 16-bit data, and one or two channels (mono or stereo) can be used. However, it is highly recommended that you avoid 8-bit sound, and not use mono input to produce stereo output.
The following table shows possible audio and audio-video writer output. For each entry, m means that mono output is possible, s means that stereo output is possible, sm means both mono and stereo output are possible, and – means the output format is not available. For audio-video writer output, vm means that this configuration is optimized for video with mono audio, and vs means that this configuration is optimized for video with stereo audio.
| Sample rate | Frequency |
||||||
Kbps |
8000 Hz | 11025 Hz | 16000 Hz | 22050 Hz | 32000 Hz | 44100 Hz | 48000 Hz |
| 5 | m | – | – | – | – | – | – |
| 6 | m | – | – | – | – | – | – |
| 8 | m | m | – | – | – | – | – |
| 10 | – | m | m | – | – | – | – |
| 12 | s | – | m | – | – | – | – |
| 16 | – | – | sm vm |
m | – | – | – |
| 20 | – | – | s | sm vm vs |
m | – | – |
| 22 | – | – | – | s | s | – | – |
| 32 | – | – | – | s vs |
sm vm |
m | – |
| 36 | – | – | – | – | s | – | – |
| 40 | – | – | – | – | s | – | – |
| 44 | – | – | – | – | s | – | – |
| 48 | – | – | – | – | s | s | – |
| 64 | – | – | – | – | s vs |
s vs |
– |
| 80 | – | – | – | – | – | s | s |
| 96 | – | – | – | – | – | s | – |
| 128 | – | – | – | – | – | s | s |
| 160 | – | – | – | – | – | s | – |
The audio reader takes the input format from the Windows Media audio file that it receives, and produces output in PCM format.
The ACELP codec can handle the following combinations of audio input and output.
| Sample rate | Frequency |
|
Kbps |
8000 Hz | 16000 Hz |
| 5 | m | – |
| 6.5 | m | – |
| 8.5 | m | – |
| 16 | – | m |
See Also
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