Extra Bytes
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8/28/2008
The cbSize member in a WAVEFORMATEX (Waveform Audio) structure must contain the number of extra bytes allocated for the WAVEFORMATEX structure. Given that the only mandatory extra field passed to the ACM codec is the wSamplesPerBlockmember, this value must always be at least 2.
In order for the ACM codec to function with VoIP, the following restrictions must be followed:
- The cbSize member can be any value from 0 to 16. However, it cannot be greater than 16.
- The VoIP code does not examine the additional fields for WAVEFORMATEX and initializes them to 0 when opening the ACM codec. Values for these fields cannot be specified by an OEM.