Ok, so this means for a track with 2 channels, I get 2 items per
sample (Float32 in my case).
But, since I only want one of those (and with a track with 10 odd
channels even) how do I further refine it to pick only the one I
want?
Let's say you set "all channels discrete" on a source movie with 10
channels of audio in a single audio track, and you know you want
just the second channel of audio. In your resulting
AudioBufferList, just use the contents of:
bufferList->mBuffers[1].mData.
The data is still non-interleaved. Unless you specifically set it
to be interleaved (you do this by mucking with the flags and
various other fields in the audio stream basic description).
Ok, I get it, thanks.
A bit of a waste of buffer space. This could be a big deal. If each
buffer is 128K and there are say, realistically, 6 channels, and
maybe 4 instances of my component, then I have 128K * 4 * 6 = 6MB of
unused buffers.
Would be nice if I left the buffer pointer as NULL if the extraction
API just skipped that channel instead of bailing completely.
Not too big a deal on OSX I guess, but on Windows....
But I have another issue.
The missing data I discovered was my bug :) But its related to:
When I set: kQTMovieAudioExtractionMoviePropertyID_CurrentTime
How do I know which sample number is being returned?
Presumably if the timescale is 600, and the sample rate os 128K or
so, 1/600th covers a lot of samples, so which one did you pick to
return as the first byte?
So I go to time: 123456, the time scale is 600, the sample number
you return as byte 0 is ????
I can make a guess using 64bit math, which is what I am doing, but I
MAY need more accuracy.
I'll know more once I get this all working and throw it by some
scientist types :)
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