RE: UNANSWERED: audio extraction problem: single track works, four separate tracks doesn't

Ugh, I figured this out, thanks.  As I was writing the mail back to the list, I realized my issue.

 

So, I’m using the mNumberChannelDescriptions to assign m_dwChannels (the # of source channels), and then m_dwSampleRate, m_dwBitsPerSample are pulled from the asbd on the media sample description.    In the case where the source file has four separate tracks, mChannelsPerFrame on the media sample description just comes back with 1 channel, and that was causing problems if I used that value.

 

This code seems to work correctly for 4 channel audio contained in one track or in four separate tracks:

 

                                         BailIfOSErr( MovieAudioExtractionGetProperty(m_audioExtractionSession, kQTPropertyClass_MovieAudioExtraction_Audio,

                                                kQTMovieAudioExtractionAudioPropertyID_AudioChannelLayout, size, layout, NULL) );

 

 

                                         m_dwChannels = layout->mNumberChannelDescriptions;

 

[…]

 

                                         asbd.mFormatID = 'lpcm';

                                         asbd.mSampleRate = m_dwSampleRate;

                                         asbd.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;

                                         asbd.mChannelsPerFrame = m_dwChannels;

                                         asbd.mBitsPerChannel = m_dwBitsPerSample;

                                         asbd.mFramesPerPacket = 1;

                                         asbd.mBytesPerPacket = asbd.mBytesPerFrame = ((asbd.mBitsPerChannel >> 3) * asbd.mChannelsPerFrame);

 

                                         //

                                         // Set the new audio extraction ASBD

                                         //

                                         BailIfOSErr( MovieAudioExtractionSetProperty(m_audioExtractionSession,

                                                              kQTPropertyClass_MovieAudioExtraction_Audio,

                                                              kQTMovieAudioExtractionAudioPropertyID_AudioStreamBasicDescription,

                                                              sizeof (asbd), &asbd) );