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Re: Static when playing back buffers

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Re: Static when playing back buffers

Subject: Re: Static when playing back buffers
From: Pier <email@hidden>
Date: Fri, 09 Nov 2012 11:31:18 +0800

hi all,

I noticed that Mr Craig Bakalian had the same problem..

http://www.mailinglistarchive.com/html/email@hidden/2006-10/msg00017.html

Apparently the reason I have 2 buffers is that the Audio Unit returns an interleaved format. (left, right channels)

To write to a file, I can do this

AudioUnitGetProperty(mAudioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, mBusNumber, &clientFormat, &size);

ExtAudioFileSetProperty(mExtAudioFile, kExtAudioFileProperty_ClientDataFormat, size, &clientFormat);

to set the extAudioFile to be the same format as the interleaved output of the AudioUnit. And it works producing a file recording of the mixed output from the mixer AudioUnit.

However in my case I wish to directly manipulate the buffers and save it into TPCircularBuffer for use later. I feel like I'm really close to getting this but I'm still hearing static when I pull from these buffers and put them in TPCircularBuffer and play them back later.

How can I do so? :/

Thanks.

Pier.

On Thu, Nov 8, 2012 at 5:16 PM, Pier <email@hidden> wrote:

Hi,

I used

  AURenderCallbackStruct mcallbackStruct;

mcallbackStruct.inputProc = mixedRecordingCallback;

mcallbackStruct.inputProcRefCon = &rio;

  status = AudioUnitAddRenderNotify(_mixerUnit, mcallbackStruct.inputProc, mcallbackStruct.inputProcRefCon);

to add the callback to my mixer AudioUnit.

I'm getting static when trying to playback finalOutputBuffer (captured below).

I've noticed that there are 2 buffers in ioData this time round - that never happened before. I suspect that this could be the problem, has anyone had any experience with this?

Thanks.

Pier.

static OSStatus mixedRecordingCallback(void *inRefCon,

   AudioUnitRenderActionFlags *ioActionFlags,

   const AudioTimeStamp *inTimeStamp,

   UInt32 inBusNumber,

   UInt32 inNumberFrames,

   AudioBufferList *ioData)

{



if (*ioActionFlags & kAudioUnitRenderAction_PostRender) {



RIO *rio = (RIO*)inRefCon;

static int TEMP_kAudioUnitRenderAction_PostRenderError = (1 << 8);

SInt16 *targetBuffer;





if (rio->recordingMixed)

{

if (0 == inBusNumber && !(*ioActionFlags & TEMP_kAudioUnitRenderAction_PostRenderError)) {

NSLog(@"Recording Mixed Output : Bus %ld", inBusNumber);



for (int i=0; i < ioData->mNumberBuffers; i++)

{

targetBuffer= (SInt16*)ioData->mBuffers[i].mData;

TPCircularBufferProduceBytes(&rio->finalOutputBuffer, targetBuffer, inNumberFrames * sizeof(SInt16));

}



}

}

}

return noErr;

}

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