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POHow to record sound produced by mixer unit output (iOS Core Audio & Audio Graph)
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copied!<p>I'm trying to record sound produced by a mixer unit output.</p> <p>For the moment, my code is based on the <a href="http://developer.apple.com/library/ios/#samplecode/MixerHost/Introduction/Intro.html">apple MixerHost iOS app</a> demo : A <strong>mixer node</strong> is connected to a <strong>remote IO node</strong> on the audio graphe.</p> <p>And i try to set an <em>input callback</em> on the <strong>remote IO node</strong> input on the mixer output.</p> <p>I do something wrong but I can not find the error.</p> <p>Here is the code below. This is done just after the Multichannel Mixer unit Setup :</p> <pre><code>UInt32 flag = 1; // Enable IO for playback result = AudioUnitSetProperty(iOUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, // Output bus &flag, sizeof(flag)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty EnableIO" withStatus: result]; return;} /* can't do that because *** AudioUnitSetProperty EnableIO error: -1073752493 00000000 result = AudioUnitSetProperty(iOUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 0, // Output bus &flag, sizeof(flag)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty EnableIO" withStatus: result]; return;} */ </code></pre> <p>Then create a stream format :</p> <pre><code>// I/O stream format iOStreamFormat.mSampleRate = 44100.0; iOStreamFormat.mFormatID = kAudioFormatLinearPCM; iOStreamFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked; iOStreamFormat.mFramesPerPacket = 1; iOStreamFormat.mChannelsPerFrame = 1; iOStreamFormat.mBitsPerChannel = 16; iOStreamFormat.mBytesPerPacket = 2; iOStreamFormat.mBytesPerFrame = 2; [self printASBD: iOStreamFormat]; </code></pre> <p>Then affect the format and specify sample rate :</p> <pre><code>result = AudioUnitSetProperty(iOUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, // Input bus &iOStreamFormat, sizeof(iOStreamFormat)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty StreamFormat" withStatus: result]; return;} result = AudioUnitSetProperty(iOUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, // Output bus &iOStreamFormat, sizeof(iOStreamFormat)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty StreamFormat" withStatus: result]; return;} // SampleRate I/O result = AudioUnitSetProperty (iOUnit, kAudioUnitProperty_SampleRate, kAudioUnitScope_Input, 0, // Output &graphSampleRate, sizeof (graphSampleRate)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty (set I/O unit input stream format)" withStatus: result]; return;} </code></pre> <p>Then, i try to set the render callback.</p> <p><strong>Solution 1 >>> my recording callback is never called</strong></p> <pre><code>effectState.rioUnit = iOUnit; AURenderCallbackStruct renderCallbackStruct; renderCallbackStruct.inputProc = &recordingCallback; renderCallbackStruct.inputProcRefCon = &effectState; result = AudioUnitSetProperty (iOUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, // Output bus &renderCallbackStruct, sizeof (renderCallbackStruct)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty SetRenderCallback" withStatus: result]; return;} </code></pre> <p><strong>Solution 2 >>> my app crashes at launch on this</strong></p> <pre><code>AURenderCallbackStruct renderCallbackStruct; renderCallbackStruct.inputProc = &recordingCallback; renderCallbackStruct.inputProcRefCon = &effectState; result = AUGraphSetNodeInputCallback (processingGraph, iONode, 0, // Output bus &renderCallbackStruct); if (noErr != result) {[self printErrorMessage: @"AUGraphSetNodeInputCallback (I/O unit input callback bus 0)" withStatus: result]; return;} </code></pre> <p>If anyone have an idea ...</p> <p><strong>EDIT Solution 3 (thanks to arlo anwser) >> There is now a format problem</strong></p> <pre><code>AudioStreamBasicDescription dstFormat = {0}; dstFormat.mSampleRate=44100.0; dstFormat.mFormatID=kAudioFormatLinearPCM; dstFormat.mFormatFlags=kAudioFormatFlagsNativeEndian|kAudioFormatFlagIsSignedInteger|kAudioFormatFlagIsPacked; dstFormat.mBytesPerPacket=4; dstFormat.mBytesPerFrame=4; dstFormat.mFramesPerPacket=1; dstFormat.mChannelsPerFrame=2; dstFormat.mBitsPerChannel=16; dstFormat.mReserved=0; result = AudioUnitSetProperty(iOUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &stereoStreamFormat, sizeof(stereoStreamFormat)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;} result = AudioUnitSetProperty(iOUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &stereoStreamFormat, sizeof(stereoStreamFormat)); if (noErr != result) {[self printErrorMessage: @"AudioUnitSetProperty" withStatus: result]; return;} AudioUnitAddRenderNotify( iOUnit, &recordingCallback, &effectState ); </code></pre> <p>and the file setup :</p> <pre><code>if (noErr != result) {[self printErrorMessage: @"AUGraphInitialize" withStatus: result]; return;} // On initialise le fichier audio NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *destinationFilePath = [[[NSString alloc] initWithFormat: @"%@/output.caf", documentsDirectory] autorelease]; NSLog(@">>> %@", destinationFilePath); CFURLRef destinationURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)destinationFilePath, kCFURLPOSIXPathStyle, false); OSStatus setupErr = ExtAudioFileCreateWithURL(destinationURL, kAudioFileWAVEType, &dstFormat, NULL, kAudioFileFlags_EraseFile, &effectState.audioFileRef); CFRelease(destinationURL); NSAssert(setupErr == noErr, @"Couldn't create file for writing"); setupErr = ExtAudioFileSetProperty(effectState.audioFileRef, kExtAudioFileProperty_ClientDataFormat, sizeof(AudioStreamBasicDescription), &stereoStreamFormat); NSAssert(setupErr == noErr, @"Couldn't create file for format"); setupErr = ExtAudioFileWriteAsync(effectState.audioFileRef, 0, NULL); NSAssert(setupErr == noErr, @"Couldn't initialize write buffers for audio file"); </code></pre> <p>And the recording callback :</p> <pre><code>static OSStatus recordingCallback (void * inRefCon, AudioUnitRenderActionFlags * ioActionFlags, const AudioTimeStamp * inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList * ioData) { if (*ioActionFlags == kAudioUnitRenderAction_PostRender && inBusNumber == 0) { EffectState *effectState = (EffectState *)inRefCon; ExtAudioFileWriteAsync(effectState->audioFileRef, inNumberFrames, ioData); } return noErr; } </code></pre> <p>There is something missing in the output file <a href="http://www.iphone.re/audio/output.caf">output.caf</a> :). I'm totally lost in formats to apply.</p>

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