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POSilence when adding kAudioUnitSubType_MultiChannelMixer to AUGraph
 

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  1. POSilence when adding kAudioUnitSubType_MultiChannelMixer to AUGraph
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    <p>I'm having trouble inserting a mixer unit into an <code>AUGraph</code> that otherwise works OK on both Mac OS and iOS.</p> <p>My working graph looks like this:</p> <pre><code>(My Audio render callback) &lt;- [Format converter] &lt;- [DefaultOutput] </code></pre> <p>In addition, I'm able to successfully insert an EQ unit like this: </p> <pre><code>(My Audio render callback) &lt;- [Format converter] &lt;- [GraphicEQ] &lt;- [DefaultOutput] </code></pre> <p>My goal is to insert a mixer unit but no EQ so I can control the volume of my graph independently of the system volume on iOS. However, when I set up the graph it seems to <em>look</em> OK, but all I get is silence.</p> <p>Here's what the graph looks like: </p> <pre><code>(My Audio render callback) &lt;- [Format converter] &lt;- [MultiChannelMixer] &lt;- [DefaultOutput] </code></pre> <p>…and the output of CAShow:</p> <pre><code>AudioUnitGraph 0x397000: Member Nodes: node 1: 'auou' 'def ' 'appl', instance 0x8039704d O I node 2: 'aumx' 'mcmx' 'appl', instance 0x8039704e O I node 3: 'aufc' 'conv' 'appl', instance 0x8039704f O I Connections: node 3 bus 0 =&gt; node 2 bus 0 [ 2 ch, 44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved] node 2 bus 0 =&gt; node 1 bus 0 [ 2 ch, 44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved] Input Callbacks: {0x100035d90, 0x10037cd60} =&gt; node 3 bus 0 [2 ch, 44100 Hz] CurrentState: mLastUpdateError=0, eventsToProcess=F, isRunning=T (1) </code></pre> <p>And, finally, the code that's setting up the graph with error-checking and iOS-specific code removed: </p> <pre><code>// A description of the output device we're looking for. AudioComponentDescription outputDescription; outputDescription.componentType = kAudioUnitType_Output; outputDescription.componentSubType = kAudioUnitSubType_DefaultOutput; outputDescription.componentManufacturer = kAudioUnitManufacturer_Apple; outputDescription.componentFlags = 0; outputDescription.componentFlagsMask = 0; // A description of the mixer unit AudioComponentDescription mixerDescription; mixerDescription.componentType = kAudioUnitType_Mixer; mixerDescription.componentSubType = kAudioUnitSubType_MultiChannelMixer; mixerDescription.componentManufacturer = kAudioUnitManufacturer_Apple; mixerDescription.componentFlags = 0; mixerDescription.componentFlagsMask = 0; // A description for the libspotify -&gt; standard PCM device AudioComponentDescription converterDescription; converterDescription.componentType = kAudioUnitType_FormatConverter; converterDescription.componentSubType = kAudioUnitSubType_AUConverter; converterDescription.componentManufacturer = kAudioUnitManufacturer_Apple; converterDescription.componentFlags = 0; converterDescription.componentFlagsMask = 0; // Create an AUGraph OSErr status = NewAUGraph(&amp;audioProcessingGraph); // Open the graph. AudioUnits are open but not initialized (no resource allocation occurs here) AUGraphOpen(audioProcessingGraph); // Add audio output... status = AUGraphAddNode(audioProcessingGraph, &amp;outputDescription, &amp;outputNode); // Add mixer status = AUGraphAddNode(audioProcessingGraph, &amp;mixerDescription, &amp;mixerNode); // Get mixer unit so we can change volume etc status = AUGraphNodeInfo(audioProcessingGraph, mixerNode, NULL, &amp;mixerUnit); // Set mixer bus count UInt32 busCount = 1; status = AudioUnitSetProperty(mixerUnit, kAudioUnitProperty_ElementCount, kAudioUnitScope_Input, 0, &amp;busCount, sizeof(busCount)); // Create PCM converter status = AUGraphAddNode(audioProcessingGraph, &amp;converterDescription, &amp;inputConverterNode); // Connect converter to mixer status = AUGraphConnectNodeInput(audioProcessingGraph, inputConverterNode, 0, mixerNode, 0); // Connect mixer to output status = AUGraphConnectNodeInput(audioProcessingGraph, mixerNode, 0, outputNode, 0); // Set render callback AURenderCallbackStruct rcbs; rcbs.inputProc = AudioUnitRenderDelegateCallback; rcbs.inputProcRefCon = (__bridge void *)(self); status = AUGraphSetNodeInputCallback(audioProcessingGraph, inputConverterNode, 0, &amp;rcbs); // Init Queue status = AUGraphInitialize(audioProcessingGraph); AUGraphUpdate(audioProcessingGraph, NULL); AUGraphStart(audioProcessingGraph); </code></pre>
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    1. USiKenndac
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    2. VO
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      1. VTUpMod
    1. COso this worked with the GraphicEQ instead of the mixer ? With the same callback? can you get it working without the callback?
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      1. UShooleyhoop
 

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