Re: AudioQueueOflineRender() and 'alac' files on iPhone
Re: AudioQueueOflineRender() and 'alac' files on iPhone
- Subject: Re: AudioQueueOflineRender() and 'alac' files on iPhone
- From: William Stewart <email@hidden>
- Date: Wed, 25 Mar 2009 14:40:05 -0700
Have you looked at the tech note we have on this? That comes with an
alac file for testing, so I believe this is working
Bill
On Mar 25, 2009, at 8:54 AM, Roni Music wrote:
I'm using AudioQueueOflineRender() on the iPhone OS 2.2.1
decoding data in a secondary high priority thread that fills my
buffer and then playing back the samples using
kAudioUnitSubType_RemoteIO.
I try to keep around 1000 ms of decoded audio samples in my buffer.
It works like a charm except for 'alac' files.
When calling AudioQueueOflineRender() and asking for 2048 frames
and timing that call it looks like this:
100 ms
1 ms
113 ms
1 ms
107 ms
1 ms
etc
which works fine but occasionally, say once every 2-3 minutes, the
AudioQueueOflineRender() call takes
more than 1000 ms, even 1500 ms, which makes my buffer run dry and I
have glitches in the audio output.
This never happens for any other file type such as mp3, aac/m4a etc.
I can increase my buffer size to say 2000 ms for 'alac' files only
which fixes the problem but makes the app much less responsive and
startup time also increases. And it feels like a "hack".
Is this normal or is it a known problem with 'alac' files?
I've tried to use the CFRunLoopRef from my secondary thread when
setting up AudioQueueNewOutput() since this is the thread that calls
AudioQueueOflineRender() but it makes no difference and I'm also not
sure if this is correct?
The "mandatory" zero frame AudioQueueOflineRender() call has a
tendency to deadlock when doing it this way so it doesn't seem to be
the way to go.
Any advice?
Thanks,
Rolf
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