ACM Wrapper Filter
The ACM Wrapper filter enables Audio Compression Manager (ACM) codecs to join a filter graph. It can act either as a decompression filter or as a compression filter.
As a decompression filter, the ACM Wrapper appears in the "DirectShow Filters" category (CLSID_LegacyAmFilterCategory) and has a merit of MERIT_NORMAL. The connection media type on the input pin determines which codec the filter uses. Typically, the application does not need to add the filter to the filter graph; it is pulled in automatically by the Filter Graph Manager when needed. Decompression is only to PCM audio.
As a compression filter, the ACM Wrapper appears in the "Audio Compressors" category (CLSID_AudioCompressorCategory) and has a merit of MERIT_DO_NOT_USE. Each codec appears as a separate instance. For compression, you cannot directly create the filter with CoCreateInstance. Instead, you must use the system device enumerator. For more information, see Using the System Device Enumerator.
|Filter interfaces||IBaseFilter, IPersist, IPersistPropertyBag|
|Input pin media types||MEDIATYPE_Audio, MEDIASUBTYPE_NULL, FORMAT_WaveFormatEx|
|Input pin interfaces||IMemInputPin, IPin, IQualityControl|
|Output pin media types||MEDIATYPE_Audio, MEDIASUBTYPE_PCM, FORMAT_WaveFormatEx.Any combination of the following are possible:
|Output pin interfaces||IAMStreamConfig, IMediaPosition, IMediaSeeking, IPin, IQualityControl|
|Property Page CLSID||No property page.|
|Merit||MERIT_NORMAL or MERIT_DO_NOT_USE|
|Filter Category||CLSID_LegacyAmFilterCategory or CLSID_AudioCompressorCategory|