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Getting Format Capabilities on Devices That Support Only IWMDMDevice

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The recommended method for querying a device for its playback capabilities is IWMDMDevice3::GetFormatCapability. However, if a device does not support this method, the application instead can call IWMDMDevice::GetFormatSupport to retrieve an array of supported audio formats as _WAVEFORMATEX structures and MIME formats as strings from the device.

The following steps show how an application can use this method to query a device for supported formats:

  1. Call GetFormatSupport to retrieve arrays of both audio and mime formats.
  2. Loop through the retrieved audio formats and examine each _WAVEFORMATEX structure to try to find an acceptable audio format
  3. Loop through the retrieved MIME format strings (if desired) to find an acceptable file type. The SDK does not define constants for MIME formats; you should use industry standard values (which can be found at the iana.org Web site). A device should list the specific MIME types that it supports.

The following C++ code demonstrates retrieving format capabilities from a device, using GetFormatSupport.

// Function to print out device caps for a device 
// that supports only IWMDMDevice.
void CWMDMController::GetCaps(IWMDMDevice* pDevice)
{
    HRESULT hr = S_OK;

    // Get all capabilities for audio and mime support.
    _WAVEFORMATEX* pAudioFormats;
    LPWSTR* pMimeFormats;
    UINT numAudioFormats = 0;
    UINT numMimeFormats = 0;
    hr = pDevice->GetFormatSupport(
        &pAudioFormats,
        &numAudioFormats,
        &pMimeFormats,
        &numMimeFormats);
    if (FAILED(hr)) return;

    // Print out audio format data.
    if (numAudioFormats > 0)
    {
        // TODO: Display a banner for the supported audio-format listing.
    }
    else
    {
        // TODO: Display a message indicating that no audio formats are supported.
    }
    for (int i = 0; i < numAudioFormats; i++)
    {
// TODO: For each valid audio format, display the max channel, 
// max samples/second, avg. bytes/sec, block alignment, and 
// max bits/sample values.
    }

    // Print out MIME formats.
    if (numMimeFormats > 0)
        // TODO: Display a banner to precede the MIME format listing.
    else
        // TODO: Display a banner indicating that no MIME formats are supported.
    for (i = 0; i < numMimeFormats; i++)
    {
        // TODO: Display the specified MIME format.
    }
    return;
}

See Also