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Problem with AudioQueueOfflineRender in iOS4
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Problem with AudioQueueOfflineRender in iOS4


  • Subject: Problem with AudioQueueOfflineRender in iOS4
  • From: Zachary Kulis <email@hidden>
  • Date: Thu, 24 Jun 2010 16:27:32 -0400

Hi all,

I finally installed XCode 3.2.3 and the iOS4.0 SDK today, and I'm
experiencing some very strange behavior with the AudioQueueOfflineRender
API. I am using the API to decode MP3 files on-the-fly into PCM data.
This strategy has worked fine in OS 2.2.1-OS 3.2. After upgrading my
iPhone to iOS4, however, the AudioQueueOfflineRender() function
occasionally reports that it has decoded 0 frames, even though no error
code is returned and there are plenty of enqueued packets ready for
decoding (approximately 1.5 seconds of compressed audio enqueued).

The really odd thing is that if I put a do {}
while(numFramesRendered==0) around this AudioQueueOfflineRender()
function call, the decoder eventually decodes the requested frames.
However, strange things start to happen after about 5-10 seconds into
the audio stream; the sound quality deteriorates and random
crackling/static is present in the decoded PCM data. As time progresses,
the audio quality continues to deteriorate, until finally a loud
squealing sound develops (almost like feedback), and the decoded audio
is completely obscured.

I've tried running the same code on my iPod Touch 2G (which is currently
running OS 3.1.2), and everything seems fine. The problem only occurs
under iOS4.0, regardless of which OS I target for deployment in XCode
(i.e., even if I target OS 3.1.2 in XCode, the problem still occurs on
my iPhone).

Any help/insight would be greatly appreciated.

Thanks,
Zach

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  • Follow-Ups:
    • Re: Problem with AudioQueueOfflineRender in iOS4
      • From: infrequent <email@hidden>
References: 
 >VoiceProcessingIO - echo cancellation issues (From: Zachary Kulis <email@hidden>)
 >Re: VoiceProcessingIO - echo cancellation issues (From: Raphaël - Mancing Dolecules <email@hidden>)
 >Re: VoiceProcessingIO - echo cancellation issues (From: Zachary Kulis <email@hidden>)
 >Re: VoiceProcessingIO - echo cancellation issues (From: Raphaël - Mancing Dolecules <email@hidden>)

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