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Audio glitches during playback thru Remote IO unit (iPhone)
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Audio glitches during playback thru Remote IO unit (iPhone)


  • Subject: Audio glitches during playback thru Remote IO unit (iPhone)
  • From: "Zhiye (Sterling) Li" <email@hidden>
  • Date: Wed, 12 Aug 2009 00:42:24 -0500

Hello,

Hope somebody can help me figure this out.

In my iPhone application, I am using the Remote IO unit to do the recording and playback. The recording has no problem at all, but when playing back an audio file, the audio clicks once every a few minutes, sometimes even more frequently.

Here's my playback callback funtion:

static OSStatus    PlaybackCallback(
                            void                                             *inRefCon,
                            AudioUnitRenderActionFlags     *ioActionFlags,
                            const AudioTimeStamp              *inTimeStamp,
                            UInt32                                         inBusNumber,
                            UInt32                                        inNumberFrames,
                            AudioBufferList                          *ioData)

{   AppDelegate *THIS = (AppDelegate *)inRefCon;
   
    if (!THIS.auOutputFlag) {
        // fill the buffer with zeros.
        memset(ioData->mBuffers[0].mData,0,ioData->mBuffers[0].mDataByteSize);
        return noErr;
    }
   
    // Read data from file
    ExtAudioFileRead (THIS.audiofile,&inNumberFrames,ioData);   

    return noErr;
}

Since it doesn't glitch at the same place every time, it means the recording is fine. I have tried the double-buffering method, but it didn't make it any better and the audio still clicks. Changing the buffer size also didn't solve the problem. The most frustrating thing is that all the Remote IO sample code I have found do not playback audio from a file... this has driven me crazy... Has anyone ever used remote io to playback an audio file? Anyone  had the same or similar problem before? Hope somebody can help me out. Thank you in advance!


Zhiye
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