Capturing TV Audio

To capture audio from analog television to a file, use the Audio Capture Filter. Use the System Device Enumerator to create the Audio Capture Filter. There may be several audio capture devices on the user's system; the user must select the device that represents the sound card.

Connect the audio capture output pin to the mux filter:

hr = pBuild->RenderStream(
   &PIN_CATEGORY_CAPTURE, // Capture pin.
   &MEDIATYPE_Audio,      // Audio media type.
   pAudioCap,             // Pointer to the audio capture filter.
   NULL,                  // Optional audio compressor filter.
   pMux);                 // Pointer to the mux filter.

The input pins do not have to be connected to anything. Each input pin represents a physical input on the audio capture device. Use the IAMAudioInputMixer interface to enable the input that receives the audio stream from the tuner. The input pins are identified by name, such as "Line In" or "CD Audio." Unfortunately, the names can change from one device to the next. Also, different TV tuner cards use different inputs to the sound card. Therefore, it is up to the user to identify which input to use.

IEnumPins *pEnum = NULL;
hr = pAudioCap->EnumPins(&pEnum);
if (SUCCEEDED(hr))
{
    IPin *pPin = NULL;
    while (S_OK == pEnum->Next(1, &pPin, NULL))
    {
        IAMAudioInputMixer *pMix;
        hr = pPin->QueryInterface(IID_IAMAudioInputMixer, (void**)&pMix);
        if (SUCCEEDED(hr))
        {
            // Use IPin::QueryPinInfo to get the pin name.
            pPin->Release();
            if (...) // If the user selects this pin:
            {
                pMix->put_Enable(TRUE);
                pMix->put_MixLevel(1.0);
                pMix->Release();
                break;
            }
            pMix->Release();
        }
    }
}
pEnum->Release();

See Also

• Audio Capture