Re: ExtAudioFileWrite writes zeroes?
Re: ExtAudioFileWrite writes zeroes?
- Subject: Re: ExtAudioFileWrite writes zeroes?
- From: William Stewart <email@hidden>
- Date: Mon, 2 Jul 2007 19:38:08 -0700
If you are getting zeroes in the file that is because you are feeding
in zeroes, so it really depends on what (and where) exactly you are
getting the data from to write.
For instance, if you get the data from a render notification callback
(AudioUnitAddRenderNotify), then make sure you are only grabbing the
data when the *ioAction flag signals PostRender... But, I don't know
if this is the problem or not (you need to provide more info)
Bill
On 27/06/2007, at 4:30 PM, patrick machielse wrote:
I have an application which processes audio files and uses the
ExtendedAudioFile API to write the processed data to file. The
processing is done in several steps. In each step I set up an
AUGraph which starts with an AudioFilePlayerAU, followed by a
number of other units and ending in a Generic Output unit. Saving
is done on a render notification callback installed on the output
unit. All processing is done offline.
In the last processing step I have a very short AUGraph; a file
player, 1 audio unit, and a generic output unit. The input file
format is CAF, and the output format is WAV. All the calls to
ExtAudioFileWrite() succeed, and the file length is exactly as long
as it should be, but regularly a large part of the file is just
zeroes. Just before this happens there are mostly a few 'white outs'.
I have similar (but longer...) AUGraph that reads mp3 (mostly) and
writes out CAF files without any problems. I looks as if
simultaneously reading in and writing out large audio files somehow
goes wrong.
I've tried to increase the io buffer to 1 MB (from the default
value of 64k) but this hasn't improved the situation. Should I use
a larger buffer still? Should I try to write the file asynchronously?
patrick
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