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Help Please - failure in creating audio file.
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Help Please - failure in creating audio file.


  • Subject: Help Please - failure in creating audio file.
  • From: wm schauweker <email@hidden>
  • Date: Thu, 14 Jan 2010 19:13:43 -0800 (PST)

I would be most grateful for any guidance anyone could offer.

o On iPhone, using SDK 3.1.2, testing in emulator.
o I am trying to use Core Audio to create a file from audio sample data.
oThis is in the nature of an "export" routine - exporting audio data that was originally taken from an Audio Unit and stashed in a "sample" file.
o Now, I want to read the sample file and convert to .wav format.

After much hacking I have the following working to the point that I can create an AudioConverter. However the CreatAudioFile function is failing with a fmt? error. (I had the whole copy sequence working earlier, but the the formats were bogus - I specified only one channel, but the sample file format is two-channel mono - buffer of sound, buffer of silence, ... .)

Here are the ASBDs I am defining, and a snippet of the code in question:

        // Specify sample format. (AudioUnit input samples - 8.24 uninterleaved, 2 channels)
        inputFormat.mSampleRate = 44100.0;
        inputFormat.mFormatID = kAudioFormatLinearPCM;
        inputFormat.mFramesPerPacket = 1;
        inputFormat.mChannelsPerFrame = 2;
        inputFormat.mBytesPerFrame = 4;
        inputFormat.mBytesPerPacket = 4;
        inputFormat.mBitsPerChannel = 32;
        inputFormat.mReserved = 0;
        inputFormat.mFormatFlags =
        kLinearPCMFormatFlagIsSignedInteger |
        kLinearPCMFormatFlagIsPacked |
        kAudioFormatFlagIsNonInterleaved;

        // Specify output recording format. (16-bit samples, noninterleaved.)
        outputFormat.mSampleRate = 44100.0;
        outputFormat.mFormatID = kAudioFormatLinearPCM;
        outputFormat.mFramesPerPacket = 1;
        outputFormat.mChannelsPerFrame = 2;
        outputFormat.mBytesPerFrame = 2;
        outputFormat.mBytesPerPacket = 2;
        outputFormat.mBitsPerChannel = 16;
        outputFormat.mReserved = 0;
        outputFormat.mFormatFlags =
        kLinearPCMFormatFlagIsSignedInteger |
        kLinearPCMFormatFlagIsPacked |
        kAudioFormatFlagIsNonInterleaved;

   
        // Create AudioConverter
        XThrowIfError(AudioConverterNew(&inputFormat, &outputFormat, &converter), "Exporter: Error creating AudioConverter");
       
        // Open output file.
        CFURLRef exportURL = CFURLCreateFromFileSystemRepresentation(NULL, (UInt8*)exportPath_, strlen(exportPath_), false);
/** This is the call that is failing **/
        XThrowIfError(AudioFileCreateWithURL(exportURL,
                                               kAudioFileWAVEType,
                                               &outputFormat,
                                               kAudioFileFlags_EraseFile,
                                               &outputFile), "Exporter: Error opening export output file");


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