AUAudioFilePlayer priming for compressed files
AUAudioFilePlayer priming for compressed files
- Subject: AUAudioFilePlayer priming for compressed files
- From: Brian Whitman <email@hidden>
- Date: Mon, 19 Mar 2007 12:43:16 -0400
For ExtAudioFile/CAAudioFile you can "trick" the AudioConverter into
making compressed file reads sample accurate by seeking back a few
mp3-sized frames and throwing away the samples up to your desired
start point. I'd love to get this working with the AudioFilePlayer
AU, as trying to chop up compressed files and play them back in order
does not work. But since the AudioFilePlayer does all the seeking/
reading for you, I can't tell if this is possible. I saw the
kAudioUnitProperty_ScheduledFilePrime property but no docs for it
other than to set it to default. Is there a way to "prime" the file
player AU a few frames in the past before scheduling?
We currently do this the long way, using MovieAudioExtraction into an
ABL for ScheduledSoundPlayer. We have to start decoding from 0 to be
sample accurate in QT's MAE-- an enormous waste of CPU when you're
trying to get 0.3s of audio out near the end of a 10m track.
AudioFile was better for mp3s-- you only had to go a few frames back,
not all the way to the beginning. So we'd love to shoehorn that into
AudioFilePlayer and chuck all of the manual management of IO and PCM
ram.
-Brian
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