However, the WAVEFORMATEXTENSIBLE structure can specify both the mapping of channels to speakers and the number of bits of precision in each sample. In addition, although WAVEFORMATEX specifies the size of the container for each audio sample, it cannot specify the number of bits of precision in a sample (for example, 20 bits of precision in a 24-bit container). To determine whether the Initialize method can create a shared-mode or exclusive-mode stream with a particular format, call the IAudioClient::IsFormatSupported method.īy itself, a WAVEFORMATEX structure cannot specify the mapping of channels to speaker positions. However, to avoid resampling, the engine might use a mix format with a sample rate that the device supports. If the device supports only integer PCM samples, then the engine converts the samples to or from integer PCM values at the connection between the device and the engine. Thus, the caller might not succeed in creating an exclusive-mode stream with a format obtained by calling GetMixFormat.įor example, to facilitate digital audio processing, the audio engine might use a mix format that represents samples as floating-point values. This format is not necessarily a format that the audio endpoint device supports. The mix format is the format that the audio engine uses internally for digital processing of shared-mode streams. When creating a shared-mode stream for an audio endpoint device, the Initialize method always accepts the stream format obtained from a GetMixFormat call on the same device. The client can call this method before calling the IAudioClient::Initialize method. The Windows audio service is not running. The audio endpoint device has been unplugged, or the audio hardware or associated hardware resources have been reconfigured, disabled, removed, or otherwise made unavailable for use. If it fails, possible return codes include, but are not limited to, the values shown in the following table. For information about WAVEFORMATEX, WAVEFORMATEXTENSIBLE, and CoTaskMemFree, see the Windows SDK documentation.
If the GetMixFormat call fails, *ppDeviceFormat is NULL. The caller is responsible for freeing the storage, when it is no longer needed, by calling the CoTaskMemFree function. The method allocates the storage for the structure. The method writes the address of a WAVEFORMATEX (or WAVEFORMATEXTENSIBLE) structure to this variable. This parameter must be a valid, non- NULL pointer to a pointer variable. Pointer to a pointer variable into which the method writes the address of the mix format.
The GetMixFormat method retrieves the stream format that the audio engine uses for its internal processing of shared-mode streams.
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