Allowed time stretching filters by keeping per-channel timeStamps.

TheAmazingAudioEngine/AEAudioController.m

@@ -184,7 +184,10 @@ + (NSError*)audioControllerErrorWithMessage:(NSString*)message OSStatus:(OSStatu
     BOOL             muted;
     AudioStreamBasicDescription audioDescription;
     callback_table_t callbacks;
+    AudioTimeStamp   timeStamp;
+
     BOOL             setRenderNotification;
+
     AEAudioController *audioController;
     ABOutputPort    *audiobusOutputPort;
     AEFloatConverter *audiobusFloatConverter;
@@ -439,7 +442,8 @@ static OSStatus channelAudioProducer(void *userInfo, AudioBufferList *audio, UIn
             memset(audio->mBuffers[i].mData, 0, audio->mBuffers[i].mDataByteSize);
         }
 
-        status = callback(channelObj, channel->audioController, &arg->inTimeStamp, *frames, audio);
+        status = callback(channelObj, channel->audioController, &channel->timeStamp, *frames, audio);
+        channel->timeStamp.mSampleTime += *frames;
 
     } else if ( channel->type == kChannelTypeGroup ) {
         AEChannelGroupRef group = (AEChannelGroupRef)channel->ptr;
@@ -451,10 +455,10 @@ static OSStatus channelAudioProducer(void *userInfo, AudioBufferList *audio, UIn
         if ( group->level_monitor_data.monitoringEnabled ) {
             performLevelMonitoring(&group->level_monitor_data, audio, *frames);
         }
-    }
 
-    // Advance the sample time, to make sure we continue to render if we're called again with the same arguments
-    arg->inTimeStamp.mSampleTime += *frames;
+        // Advance the sample time, to make sure we continue to render if we're called again with the same arguments
+        arg->inTimeStamp.mSampleTime += *frames;
+    }
 
     return status;
 }
@@ -468,6 +472,9 @@ static OSStatus renderCallback(void *inRefCon, AudioUnitRenderActionFlags *ioAct
     }
 
     AudioTimeStamp timestamp = *inTimeStamp;
+    if (channel->timeStamp.mFlags == 0) {
+        channel->timeStamp = *inTimeStamp;
+    }
 
     if ( channel->audiobusOutputPort && ABOutputPortGetConnectedPortAttributes(channel->audiobusOutputPort) & ABInputPortAttributePlaysLiveAudio ) {
         // We're sending via the output port, and the receiver plays live - offset the timestamp by the reported latency
@@ -981,6 +988,7 @@ - (void)addChannels:(NSArray*)channels toChannelGroup:(AEChannelGroupRef)group {
         channelElement->pan         = [channel respondsToSelector:@selector(pan)] ? channel.pan : 0.0;
         channelElement->muted       = [channel respondsToSelector:@selector(channelIsMuted)] ? channel.channelIsMuted : NO;
         channelElement->audioDescription = [channel respondsToSelector:@selector(audioDescription)] && channel.audioDescription.mSampleRate ? channel.audioDescription : _audioDescription;
+        memset(&channelElement->timeStamp, 0, sizeof(channelElement->timeStamp));
         channelElement->audioController = self;
 
         group->channels[group->channelCount++] = channelElement;