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Re: Capturing AU output to file
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Re: Capturing AU output to file


  • Subject: Re: Capturing AU output to file
  • From: Jeff Evans <email@hidden>
  • Date: Fri, 10 Apr 2009 17:20:35 -0700

Continuing to search for causes of the fmt? error I've run into two issues

- I see that the Core Audio documentation describing the AudioStreamBasicDescription is tagged as a "Legacy document - not to be used for new development." Is there something else that we should be using instead? I ran into a similar Legacy Document warning elsewhere once and was basically told that it didn't mean anything, though - maybe this one is like that?

- ExtAudioFileCreateNew is deprecated, replaced by ExtAudioFileCreateWithURL. I've tried, just for kicks, to use the new one instead - it's much cleaner and can erase an existing file - but it comes up as "undefined" in XCode even if I switch the project settings to 10.5 and the target SDK to 10.5. I can see that this call is defined in the version of ExtAudioFile.h found in the 10.5 SDK. Is this a known glitch?

	Thanks, Jeff

On Apr 10, 2009, at 2:57 PM, Doug Wyatt wrote:



e.g. to make a 16-bit stereo AIFF:

AudioStreamBasicDescription filefmt;

filefmt.mSampleRate = auRenderSampleRate;
// you probably don't want to guess on the sample rate; get the AU's rate


filefmt.mFormatID = kAudioFormatLinearPCM;
filefmt.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
filefmt.mBytesPerPacket = filefmt.mBytesPerFrame = 4;
filefmt.mFramesPerPacket = 1;
filefmt.mChannelsPerFrame = 2;
filefmt.mBitsPerChannel = 16;



On Apr 10, 2009, at 14:40 , Doug Wyatt wrote:


On Apr 10, 2009, at 14:34 , Jeff Evans wrote:

Thanks, Doug - though as you say, AudioUnitGetProperty is used to fill in the ASBD based on the characteristics of the synth, which is the DLS synth. Then that ASBD is applied to the external file using ExtAudioFileSetProperty. The sample code doesn't include any other way of setting the output format, aside from specifying the type (WAVE, AIFF, CAF, etc.). I don't see why this sample code would work, given what you say below. Actually I have no proof that the sample code does work, I suppose.

In any event I've tried specifying CAF file output too, but ExtAudioFileCreateNew still fails with the unsupported format error with the ASBD filled out as per the sample code. Is the sample code missing some way to set up a separate ASBD for the output file?

Sorry, I have no idea of what sample code you are looking at or where to find it. I do, however, have a copy of CAAudioUnitOutputCapturer.h in front of me. What is the audio data format being passed to the constructor? If you get an error even when specifying CAF, then most likely the data format is not correctly filled out.


Doug




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References: 
 >Capturing AU output to file (From: Jeff Evans <email@hidden>)
 >Re: Capturing AU output to file (From: Doug Wyatt <email@hidden>)
 >Re: Capturing AU output to file (From: Jeff Evans <email@hidden>)
 >Re: Capturing AU output to file (From: Doug Wyatt <email@hidden>)
 >Re: Capturing AU output to file (From: Doug Wyatt <email@hidden>)

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