From http://net.eagle.blog.163.com/blog/static/124195920069148310829/
ACM (audio compression manager) Technical Manual
L what is ACM?
ACM is the abbreviation of "audio compression manager". It is translated as the sound compression manager and compiled by Microsoft.
The interface function library used to call the codec function. It should have been declared in the mmsystem. Pas unit, but Borland
Delphi omitted it. Of course, there has been its pas file published, you can go to the http://www.delphi-jedi.org
Download. Of course, this is not enough if you want to make more extensive applications.
L first, let's see how ACM works.
ACM allows applications to directly call a device based on the driver interfaces provided by the existing wave table audio device. ACM can handle
Diverse audio data, such as adding an external multimedia digital signal Decoder (codec), ACM can use
The drivers include: compressor and decompressor driver and format conversion.
Driver and filter driver.
The multimedia digital signal codecs (codec) support the conversion of media formats. For example, convert a PCM (pulse code
Modulation) file to ADPCM (adaptive Differential Pulse Code Modulation) file. Format Converter
What we do is to convert the media format rather than the media data type. For example, the 44-khz or 16-bit audio data can be converted to 44-khz,
8-bit. The filter does not process the media data format, but still changes the audio style of the wave table. For example, the filter can be connected.
A stream data and its echo. A simple ACM driver, even a filtering identifier, or a format identifier all support the above
Format.
Each buffered data decomposed by ACM audio data is sent to the converter. The converter decompress the data and decompress it.
Data queues to a new buffer, which can be compared to "ing". Then ACM outputs the" ing" data to the wave table driver.
Waiting for playback. It should be noted that, no matter whether the corresponding "ing" data is properly converted, ACM will automatically queue in the New Buffer
Reserved data segment.
For audio input, ACM uses a background job to receive data sources from the relevant driver, compress the data segment, and then
Feedback to the output device, so a buffer unit is a processing cycle. After the data is compressed, it is directly sent to the relevant
Application.
