CAAudioUnitOutputCapturer.h

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*/
#ifndef __CAAudioUnitOutputCapturer_h__
#define __CAAudioUnitOutputCapturer_h__

#include <AudioToolbox/ExtendedAudioFile.h>

/*
    Class to capture output from an AudioUnit for analysis.

    example:

    CFURL fileurl = CFURLCreateWithFileSystemPath(NULL, CFSTR("/tmp/recording.caf"), kCFURLPOSIXPathStyle, false);

    CAAudioUnitOutputCapturer captor(someAU, fileurl, 'caff', anASBD);

    {
    captor.Start();
    ...
    captor.Stop();
    } // can repeat

    captor.Close(); // can be omitted; happens automatically from destructor
*/

class CAAudioUnitOutputCapturer {
public:
    enum { noErr = 0 };

    CAAudioUnitOutputCapturer(AudioUnit au, CFURLRef outputFileURL, AudioFileTypeID fileType, const AudioStreamBasicDescription &format, UInt32 busNumber = 0) :
        mFileOpen(false),
        mClientFormatSet(false),
        mAudioUnit(au),
        mExtAudioFile(NULL),
        mBusNumber (busNumber)
    {   
        CFShow(outputFileURL);
        OSStatus err = ExtAudioFileCreateWithURL(outputFileURL, fileType, &format, NULL, kAudioFileFlags_EraseFile, &mExtAudioFile);
        if (!err)
            mFileOpen = true;
    }
    
    void    Start() {
        if (mFileOpen) {
            if (!mClientFormatSet) {
                AudioStreamBasicDescription clientFormat;
                UInt32 size = sizeof(clientFormat);
                AudioUnitGetProperty(mAudioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, mBusNumber, &clientFormat, &size);
                ExtAudioFileSetProperty(mExtAudioFile, kExtAudioFileProperty_ClientDataFormat, size, &clientFormat);
                mClientFormatSet = true;
            }
            ExtAudioFileWriteAsync(mExtAudioFile, 0, NULL); // initialize async writes
            AudioUnitAddRenderNotify(mAudioUnit, RenderCallback, this);
        }
    }
    
    void    Stop() {
        if (mFileOpen)
            AudioUnitRemoveRenderNotify(mAudioUnit, RenderCallback, this);
    }
    
    void    Close() {
        if (mExtAudioFile) {
            ExtAudioFileDispose(mExtAudioFile);
            mExtAudioFile = NULL;
        }
    }
    
    ~CAAudioUnitOutputCapturer() {
        Close();
    }

private:
    static OSStatus RenderCallback( void *                          inRefCon,
                                    AudioUnitRenderActionFlags *    ioActionFlags,
                                    const AudioTimeStamp *          inTimeStamp,
                                    UInt32                          inBusNumber,
                                    UInt32                          inNumberFrames,
                                    AudioBufferList *               ioData)
    {
        if (*ioActionFlags & kAudioUnitRenderAction_PostRender) {
            CAAudioUnitOutputCapturer *This = (CAAudioUnitOutputCapturer *)inRefCon;
            static int TEMP_kAudioUnitRenderAction_PostRenderError  = (1 << 8);
            if (This->mBusNumber == inBusNumber && !(*ioActionFlags & TEMP_kAudioUnitRenderAction_PostRenderError)) {
                OSStatus result = ExtAudioFileWriteAsync(This->mExtAudioFile, inNumberFrames, ioData);
                if (result) DebugMessageN1("ERROR WRITING FRAMES: %d\n", result);
            }
        }
        return noErr;
    }
    
    bool                mFileOpen;
    bool                mClientFormatSet;
    AudioUnit           mAudioUnit;
    ExtAudioFileRef     mExtAudioFile;
    UInt32              mBusNumber;
};

#endif // __CAAudioUnitOutputCapturer_h__