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POHow do I use an effect audio unit?
 

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  1. POHow do I use an effect audio unit?
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    <p>I'm trying to play 8000hz samples and pass them through an effect. <br/>I aim to boost the audio volume (sample code doesn't do it, <i>yet</i>).<br/> I figured I needed an effect audio unit, chained to the remote audio unit.<br/> I also read about the effect unit being very strict with the format it can handle, mainly requiring 44.1khz samples, floating point and 32 bit samples (.<br/> So, I added a convertor unit.<br/> Also, since I figure (not sure though) iOS can't play 32 bit samples (thanks @hotpaw2 !) - I added another conversion back to 16 bits. The problem is, I always get error -10868 while initializing the audio graph.<br/> I get it without the last conversion unit as well.<br/> If I connect the convert unit to the output (no effect unit), everything works fine (8k samples play just fine).<br/> What's going on?</p> <pre><code> /* Must use play &amp; record category, for reasons beyond the scope of this question */ [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDuckOthers | AVAudioSessionCategoryOptionDefaultToSpeaker | AVAudioSessionCategoryOptionAllowBluetooth error:nil]; NSError* err = nil; if (![[AVAudioSession sharedInstance] setPreferredSampleRate:44100 error:&amp;err]){ NSLog(@"%@",err); } AudioUnit effect,convert,output,oconvert; AUNode neffect,nconvert,noutput,noconvert; AUGraph graph; AudioComponentDescription deffect,dconvert,doutput; AudioStreamBasicDescription in_format,out_format,effect_format; // Formats memset(&amp;in_format,0,sizeof(in_format)); memset(&amp;out_format, 0, sizeof(out_format)); memset(&amp;effect_format, 0, sizeof(effect_format)); in_format.mSampleRate = 8000; in_format.mChannelsPerFrame = 1; in_format.mFormatID = kAudioFormatLinearPCM; in_format.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked; in_format.mBitsPerChannel = 16; in_format.mFramesPerPacket = 1; in_format.mBytesPerFrame = in_format.mChannelsPerFrame * (in_format.mBitsPerChannel / 8); in_format.mBytesPerPacket = in_format.mBytesPerFrame * in_format.mFramesPerPacket; out_format.mSampleRate = 44100; out_format.mChannelsPerFrame = 1; out_format.mFormatID = kAudioFormatLinearPCM; out_format.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked; out_format.mBitsPerChannel = 16; out_format.mFramesPerPacket = 1; out_format.mBytesPerFrame = out_format.mChannelsPerFrame * (out_format.mBitsPerChannel / 8); out_format.mBytesPerPacket = out_format.mBytesPerFrame * out_format.mFramesPerPacket; effect_format.mSampleRate = 44100; effect_format.mChannelsPerFrame = 1; effect_format.mFormatID = kAudioFormatLinearPCM; effect_format.mFormatFlags = kAudioFormatFlagsNativeFloatPacked; effect_format.mBitsPerChannel = 32; effect_format.mFramesPerPacket = 1; effect_format.mBytesPerFrame = effect_format.mChannelsPerFrame * (effect_format.mBitsPerChannel / 8); effect_format.mBytesPerPacket = effect_format.mBytesPerFrame * effect_format.mFramesPerPacket; // Descriptions memset(&amp;doutput, 0, sizeof(doutput)); memset(&amp;deffect, 0, sizeof(deffect)); memset(&amp;dconvert, 0, sizeof(dconvert)); doutput.componentType = kAudioUnitType_Output; doutput.componentSubType = kAudioUnitSubType_RemoteIO; doutput.componentManufacturer = deffect.componentManufacturer = dconvert.componentManufacturer = kAudioUnitManufacturer_Apple; dconvert.componentType = kAudioUnitType_FormatConverter; dconvert.componentSubType = kAudioUnitSubType_AUConverter; deffect.componentType = kAudioUnitType_Effect; deffect.componentSubType = kAudioUnitSubType_DynamicsProcessor; // Create graph SdCheck(NewAUGraph(&amp;graph)); // Create nodes; SdCheck(AUGraphAddNode(graph, &amp;deffect, &amp;neffect)); SdCheck(AUGraphAddNode(graph, &amp;doutput, &amp;noutput)); SdCheck(AUGraphAddNode(graph, &amp;dconvert, &amp;nconvert)); SdCheck(AUGraphAddNode(graph, &amp;dconvert, &amp;noconvert)); // Open graph SdCheck(AUGraphOpen(graph)); // Get units SdCheck(AUGraphNodeInfo(graph, neffect,NULL, &amp;effect)); SdCheck(AUGraphNodeInfo(graph, noutput,NULL, &amp;output)); SdCheck(AUGraphNodeInfo(graph, nconvert,NULL, &amp;convert)); SdCheck(AUGraphNodeInfo(graph, noconvert,NULL, &amp;oconvert)); // Set formats SdCheck(AudioUnitSetProperty (output, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &amp;out_format, sizeof(out_format))); SdCheck(AudioUnitSetProperty (convert, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &amp;effect_format, sizeof(effect_format))); SdCheck(AudioUnitSetProperty (convert, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &amp;in_format, sizeof(in_format))); SdCheck(AudioUnitSetProperty (effect, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &amp;effect_format, sizeof(effect_format))); SdCheck(AudioUnitSetProperty (effect, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &amp;effect_format, sizeof(effect_format))); SdCheck(AudioUnitSetProperty (oconvert, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &amp;out_format, sizeof(out_format))); SdCheck(AudioUnitSetProperty (oconvert, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &amp;effect_format, sizeof(effect_format))); // Connect nodes SdCheck(AUGraphConnectNodeInput(graph, nconvert, 0, neffect, 0)); SdCheck(AUGraphConnectNodeInput(graph, neffect, 0, noconvert, 0)); SdCheck(AUGraphConnectNodeInput(graph, noconvert, 0, noutput, 0)); // Set render callback AURenderCallbackStruct input; memset(&amp;input, 0, sizeof(input)); input.inputProc = SdInputProc; input.inputProcRefCon = (__bridge void*)self; SdCheck(AUGraphSetNodeInputCallback(graph, nconvert, 0, &amp;input)); // Initialize graph /*** The following fails with error -10868 (unsupported format) ***/ SdCheck(AUGraphInitialize(graph)); </code></pre>
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