Question

I am trying to convert caf file to m4a file using AudioUnit. I have implemented the code to convert. When I tried to run the application, I am getting following error message;

couldn t set destination client format (-66672)

I got the sample code from following link;
http://developer.apple.com/library/ios/#samplecode/iPhoneExtAudioFileConvertTest/Introduction/Intro.html

CODE:

size = sizeof(clientFormat);
XThrowIfError(ExtAudioFileSetProperty(sourceFile, kExtAudioFileProperty_ClientDataFormat, size, &clientFormat), "couldn t set source client format");
//UInt32 encoderSpecifier = kAudioFormatMPEG4AAC;
//XThrowIfError(AudioFormatGetPropertyInfo(kAudioFormatProperty_Encoders, sizeof(encoderSpecifier), &encoderSpecifier, &size), "AudioFormatGetPropertyInfo: couldn t get property info");
size = sizeof(clientFormat);
XThrowIfError(ExtAudioFileSetProperty(destinationFile, kExtAudioFileProperty_ClientDataFormat, size, &clientFormat), "couldn t set destination client format");
AudioConverterRef audioConverter;
size = sizeof(audioConverter);
XThrowIfError(ExtAudioFileGetProperty(destinationFile, kExtAudioFileProperty_AudioConverter, &size, &audioConverter), "Couldn t get Audio Converter!");

I am not getting the solution for it. I have tried like setting the properties to the output file. But I am getting the same issue.

Please help me to resolve it.

Answer 1

I encountered this one too - It s not well-documented, but the reason is probably that you have to set the audio category to one compatible with hardware encoding.

In particular, any audio session that provides mixing with other sounds on the device will stop the encoder from working.

I know that AVAudioSessionCategoryPlayAndRecord, AVAudioSessionCategorySoloAmbient and AVAudioSessionCategoryAudioProcessing work for sure (as long as you re not overriding the kAudioSessionProperty_OverrideCategoryMixWithOthers property).

I ve actually assembled everything you need to encode any audio file to AAC into an asynchronous class: TPAACAudioConverter

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