sipsorcery's blog

Building a video softphone part V

April 26, 2012 by sipsorcery

I’ve been able to sort of accomplish my goal of recording audio and video streams to the same MP4 file. The attached code sample does the job however there is something wrong with the way I’m doing the sampling as the audio and video are slightly out of sync and also the audio is truncated from the end. I though it was worth posting the sample though as it’s taken me a few days to finally get it working. The key was getting the audio’s media attributes correctly set for the writer.

// Configure the audio stream.
// See http://msdn.microsoft.com/en-us/library/windows/desktop/dd742785(v=vs.85).aspx for AAC encoder settings.
// http://msdn.microsoft.com/en-us/library/ff819476%28VS.85%29.aspx
CHECK_HR(MFCreateMediaType( pAudioOutType ), L"Configure encoder failed to create media type for audio output sink." );
CHECK_HR( pAudioOutType->SetGUID( MF_MT_MAJOR_TYPE, MFMediaType_Audio ), L"Failed to set audio writer attribute, media type." );
CHECK_HR( pAudioOutType->SetGUID( MF_MT_SUBTYPE, MFAudioFormat_AAC ), L"Failed to set audio writer attribute, audio format (AAC).");
CHECK_HR( pAudioOutType->SetUINT32( MF_MT_AUDIO_NUM_CHANNELS, 2 ), L"Failed to set audio writer attribute, number of channels." );
CHECK_HR( pAudioOutType->SetUINT32( MF_MT_AUDIO_BITS_PER_SAMPLE, 16 ), L"Failed to set audio writer attribute, bits per sample." );
CHECK_HR( pAudioOutType->SetUINT32( MF_MT_AUDIO_SAMPLES_PER_SECOND, 44100 ), L"Failed to set audio writer attribute, samples per second.");
CHECK_HR( pAudioOutType->SetUINT32( MF_MT_AUDIO_AVG_BYTES_PER_SECOND, 16000 ), L"Failed to set audio writer attribute, average bytes per second.");
//CHECK_HR( pAudioOutType->SetUINT32( MF_MT_AAC_AUDIO_PROFILE_LEVEL_INDICATION, 0x29 ), L"Failed to set audio writer attribute, level indication.");
CHECK_HR( pWriter->AddStream( pAudioOutType, audioStreamIndex ), L"Failed to add the audio stream to the sink writer.");
pAudioOutType->Release();

RecordMP4 code sample