void StreamPropertyListenerProc (object sender, PropertyFoundEventArgs args)
{
if (args.Property == AudioFileStreamProperty.DataFormat) {
dataFormat = audioFileStream.DataFormat;
return;
}
if (args.Property != AudioFileStreamProperty.ReadyToProducePackets)
return;
if (audioQueue != null) {
// TODO: Dispose
throw new NotImplementedException ();
}
audioQueue = new OutputAudioQueue (dataFormat);
audioQueue.OutputCompleted += HandleOutputCompleted;
AudioQueueStatus status;
aqTap = audioQueue.CreateProcessingTap (TapProc, AudioQueueProcessingTapFlags.PreEffects, out status);
if (status != AudioQueueStatus.Ok)
throw new ApplicationException ("Could not create AQ tap");
// create an augraph to process in the tap. needs to convert from tapFormat to effect format and back
/* note: this is invalidname's recipe to do an in-place effect when a format conversion is needed
before and after the effect, usually because effects want floats, and everything else in iOS
core audio works with ints (or, in rare cases, fixed-point).
the graph looks like this:
[render-callback] -> [converter] -> [effect] -> [converter] -> [generic-output]
prior to calling AudioUnitRender() on generic-output the ioData to a pointer that render-callback
knows about, and NULLs the ioData provided to AudioUnitRender(). the NULL tells generic-output to
pull from its upstream units (ie, the augraph), and copying off the ioData pointer allows the
render-callback to provide it to the front of the stream. in some locales, this kind of shell game
is described as "batshit crazy", but it seems to work pretty well in practice.
*/
auGraph = new AUGraph ();
auGraph.Open ();
var effectNode = auGraph.AddNode (AudioComponentDescription.CreateConverter (AudioTypeConverter.NewTimePitch));
effectUnit = auGraph.GetNodeInfo (effectNode);
var convertToEffectNode = auGraph.AddNode (AudioComponentDescription.CreateConverter (AudioTypeConverter.AU));
var convertToEffectUnit = auGraph.GetNodeInfo (convertToEffectNode);
var convertFromEffectNode = auGraph.AddNode (AudioComponentDescription.CreateConverter (AudioTypeConverter.AU));
var convertFromEffectUnit = auGraph.GetNodeInfo (convertFromEffectNode);
var genericOutputNode = auGraph.AddNode (AudioComponentDescription.CreateOutput (AudioTypeOutput.Generic));
genericOutputUnit = auGraph.GetNodeInfo (genericOutputNode);
// set the format conversions throughout the graph
var effectFormat = effectUnit.GetAudioFormat (AudioUnitScopeType.Output);
var tapFormat = aqTap.ProcessingFormat;
convertToEffectUnit.SetAudioFormat (tapFormat, AudioUnitScopeType.Input);
convertToEffectUnit.SetAudioFormat (effectFormat, AudioUnitScopeType.Output);
convertFromEffectUnit.SetAudioFormat (effectFormat, AudioUnitScopeType.Input);
convertFromEffectUnit.SetAudioFormat (tapFormat, AudioUnitScopeType.Output);
genericOutputUnit.SetAudioFormat (tapFormat, AudioUnitScopeType.Input);
genericOutputUnit.SetAudioFormat (tapFormat, AudioUnitScopeType.Output);
// set maximum fames per slice higher (4096) so we don't get kAudioUnitErr_TooManyFramesToProcess
const uint maxFramesPerSlice = 4096;
if (convertToEffectUnit.SetMaximumFramesPerSlice (maxFramesPerSlice, AudioUnitScopeType.Global) != AudioUnitStatus.OK)
throw new ApplicationException ();
if (effectUnit.SetMaximumFramesPerSlice (maxFramesPerSlice, AudioUnitScopeType.Global) != AudioUnitStatus.OK)
throw new ApplicationException ();
if (convertFromEffectUnit.SetMaximumFramesPerSlice (maxFramesPerSlice, AudioUnitScopeType.Global) != AudioUnitStatus.OK)
throw new ApplicationException ();
if (genericOutputUnit.SetMaximumFramesPerSlice (maxFramesPerSlice, AudioUnitScopeType.Global) != AudioUnitStatus.OK)
throw new ApplicationException ();
// connect the nodes
auGraph.ConnnectNodeInput (convertToEffectNode, 0, effectNode, 0);
auGraph.ConnnectNodeInput (effectNode, 0, convertFromEffectNode, 0);
auGraph.ConnnectNodeInput (convertFromEffectNode, 0, genericOutputNode, 0);
// set up the callback into the first convert unit
if (convertToEffectUnit.SetRenderCallback (ConvertInputRenderCallback, AudioUnitScopeType.Global) != AudioUnitStatus.NoError)
throw new ApplicationException ();
var res = auGraph.Initialize ();
if (res != AUGraphError.OK)
throw new ApplicationException ();
}
