Downmix: Move downmix to DSP chain and fix a bug

The downmix filter also had a bug related to the channel configuration
used by the HRTF filter.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>

Audio/Chain/BufferChain.h

@@ -15,6 +15,7 @@
 #import "DSPHRTFNode.h"
 #import "DSPEqualizerNode.h"
 #import "VisualizationNode.h"
+#import "DSPDownmixNode.h"
 #import "InputNode.h"
 
 @interface BufferChain : NSObject {
@@ -24,6 +25,7 @@
 	DSPFSurroundNode *fsurroundNode;
 	DSPHRTFNode *hrtfNode;
 	DSPEqualizerNode *equalizerNode;
+	DSPDownmixNode *downmixNode;
 	VisualizationNode *visualizationNode;
 
 	NSURL *streamURL;
@@ -89,6 +91,8 @@
 
 - (DSPEqualizerNode *)equalizer;
 
+- (DSPDownmixNode *)downmix;
+
 - (VisualizationNode *)visualization;
 
 - (double)secondsBuffered;

Audio/Chain/BufferChain.m

@@ -11,6 +11,8 @@
 #import "CoreAudioUtils.h"
 #import "OutputNode.h"
 
+#import "AudioPlayer.h"
+
 #import "Logging.h"
 
 @implementation BufferChain
@@ -30,6 +32,7 @@
 		fsurroundNode = nil;
 		equalizerNode = nil;
 		hrtfNode = nil;
+		downmixNode = nil;
 
 		visualizationNode = nil;
 	}
@@ -47,9 +50,10 @@
 	fsurroundNode = [[DSPFSurroundNode alloc] initWithController:self previous:rubberbandNode latency:0.03];
 	equalizerNode = [[DSPEqualizerNode alloc] initWithController:self previous:fsurroundNode latency:0.03];
 	hrtfNode = [[DSPHRTFNode alloc] initWithController:self previous:equalizerNode latency:0.03];
+	downmixNode = [[DSPDownmixNode alloc] initWithController:self previous:hrtfNode latency:0.03];
 
 	// Approximately five frames
-	visualizationNode = [[VisualizationNode alloc] initWithController:self previous:hrtfNode latency:5.0 / 60.0];
+	visualizationNode = [[VisualizationNode alloc] initWithController:self previous:downmixNode latency:5.0 / 60.0];
 
 	finalNode = visualizationNode;
 }
@@ -86,6 +90,7 @@
 
 	if(![converterNode setupWithInputFormat:inputFormat withInputConfig:inputChannelConfig outputFormat:outputFormat isLossless:[[properties valueForKey:@"encoding"] isEqualToString:@"lossless"]])
 		return NO;
+	[self initDownmixer];
 
 	[self setRGInfo:rgi];
 
@@ -116,6 +121,7 @@
 	DLog(@"Input Properties: %@", properties);
 	if(![converterNode setupWithInputFormat:inputFormat withInputConfig:inputChannelConfig outputFormat:outputFormat isLossless:[[properties objectForKey:@"encoding"] isEqualToString:@"lossless"]])
 		return NO;
+	[self initDownmixer];
 
 	[self setRGInfo:rgi];
 
@@ -149,12 +155,19 @@
 
 	if(![converterNode setupWithInputFormat:inputFormat withInputConfig:inputChannelConfig outputFormat:outputFormat isLossless:[[properties objectForKey:@"encoding"] isEqualToString:@"lossless"]])
 		return NO;
+	[self initDownmixer];
 
 	[self setRGInfo:rgi];
 
 	return YES;
 }
 
+- (void)initDownmixer {
+	AudioPlayer * audioPlayer = controller;
+	OutputNode *outputNode = [audioPlayer output];
+	[downmixNode setOutputFormat:[outputNode deviceFormat] withChannelConfig:[outputNode deviceChannelConfig]];
+}
+
 - (void)launchThreads {
 	DLog(@"Properties: %@", [inputNode properties]);
 
@@ -164,6 +177,7 @@
 	[fsurroundNode launchThread];
 	[equalizerNode launchThread];
 	[hrtfNode launchThread];
+	[downmixNode launchThread];
 	[visualizationNode launchThread];
 }
 
@@ -239,6 +253,7 @@
 	[fsurroundNode setShouldContinue:s];
 	[equalizerNode setShouldContinue:s];
 	[hrtfNode setShouldContinue:s];
+	[downmixNode setShouldContinue:s];
 	[visualizationNode setShouldContinue:s];
 }
 
@@ -274,6 +289,10 @@
 	return equalizerNode;
 }
 
+- (DSPDownmixNode *)downmix {
+	return downmixNode;
+}
+
 - (VisualizationNode *)visualization {
 	return visualizationNode;
 }

Audio/Chain/DSP/DSPDownmixNode.h

@@ -0,0 +1,32 @@
+//
+//  DSPDownmixNode.h
+//  CogAudio
+//
+//  Created by Christopher Snowhill on 2/13/25.
+//
+
+#ifndef DSPDownmixNode_h
+#define DSPDownmixNode_h
+
+#import <AudioToolbox/AudioToolbox.h>
+
+#import "DSPNode.h"
+
+@interface DSPDownmixNode : DSPNode {
+}
+
+- (id _Nullable)initWithController:(id _Nonnull)c previous:(id _Nullable)p latency:(double)latency;
+
+- (BOOL)setup;
+- (void)cleanUp;
+
+- (void)resetBuffer;
+
+- (void)process;
+- (AudioChunk * _Nullable)convert;
+
+- (void)setOutputFormat:(AudioStreamBasicDescription)format withChannelConfig:(uint32_t)config;
+
+@end
+
+#endif /* DSPDownmixNode_h */

Audio/Chain/DSP/DSPDownmixNode.m

@@ -0,0 +1,184 @@
+//
+//  DSPDownmixNode.m
+//  CogAudio Framework
+//
+//  Created by Christopher Snowhill on 2/13/25.
+//
+
+#import <Foundation/Foundation.h>
+
+#import "Downmix.h"
+
+#import "Logging.h"
+
+#import "DSPDownmixNode.h"
+
+@implementation DSPDownmixNode {
+	DownmixProcessor *downmix;
+
+	BOOL stopping, paused;
+	BOOL processEntered;
+	BOOL formatSet;
+
+	AudioStreamBasicDescription lastInputFormat;
+	AudioStreamBasicDescription inputFormat;
+	AudioStreamBasicDescription outputFormat;
+
+	uint32_t lastInputChannelConfig, inputChannelConfig;
+	uint32_t outputChannelConfig;
+
+	float outBuffer[4096 * 32];
+}
+
+- (id _Nullable)initWithController:(id _Nonnull)c previous:(id _Nullable)p latency:(double)latency {
+	self = [super initWithController:c previous:p latency:latency];
+	return self;
+}
+
+- (void)dealloc {
+	DLog(@"Downmix dealloc");
+	[self cleanUp];
+}
+
+- (BOOL)fullInit {
+	if(formatSet) {
+		downmix = [[DownmixProcessor alloc] initWithInputFormat:inputFormat inputConfig:inputChannelConfig andOutputFormat:outputFormat outputConfig:outputChannelConfig];
+		if(!downmix) {
+			return NO;
+		}
+	}
+	return YES;
+}
+
+- (void)fullShutdown {
+	downmix = nil;
+}
+
+- (BOOL)setup {
+	if(stopping)
+		return NO;
+	[self fullShutdown];
+	return [self fullInit];
+}
+
+- (void)cleanUp {
+	stopping = YES;
+	while(processEntered) {
+		usleep(500);
+	}
+	[self fullShutdown];
+	formatSet = NO;
+}
+
+- (void)resetBuffer {
+	paused = YES;
+	while(processEntered) {
+		usleep(500);
+	}
+	[super resetBuffer];
+	[self fullShutdown];
+	paused = NO;
+}
+
+- (void)setOutputFormat:(AudioStreamBasicDescription)format withChannelConfig:(uint32_t)config {
+	outputFormat = format;
+	outputChannelConfig = config;
+	formatSet = YES;
+}
+
+- (void)process {
+	while([self shouldContinue] == YES) {
+		if(paused) {
+			usleep(500);
+			continue;
+		}
+		@autoreleasepool {
+			AudioChunk *chunk = nil;
+			chunk = [self convert];
+			if(!chunk || ![chunk frameCount]) {
+				if([self endOfStream] == YES) {
+					break;
+				}
+				if(paused) {
+					continue;
+				}
+				usleep(500);
+			} else {
+				[self writeChunk:chunk];
+				chunk = nil;
+			}
+		}
+	}
+}
+
+- (AudioChunk *)convert {
+	if(stopping)
+		return nil;
+
+	processEntered = YES;
+
+	if(stopping || [self endOfStream] == YES || [self shouldContinue] == NO) {
+		processEntered = NO;
+		return nil;
+	}
+
+	if(![self peekFormat:&inputFormat channelConfig:&inputChannelConfig]) {
+		processEntered = NO;
+		return nil;
+	}
+
+	if(!inputFormat.mSampleRate ||
+	   !inputFormat.mBitsPerChannel ||
+	   !inputFormat.mChannelsPerFrame ||
+	   !inputFormat.mBytesPerFrame ||
+	   !inputFormat.mFramesPerPacket ||
+	   !inputFormat.mBytesPerPacket) {
+		processEntered = NO;
+		return nil;
+	}
+
+	if((formatSet && !downmix) ||
+	   memcmp(&inputFormat, &lastInputFormat, sizeof(inputFormat)) != 0 ||
+	   inputChannelConfig != lastInputChannelConfig) {
+		lastInputFormat = inputFormat;
+		lastInputChannelConfig = inputChannelConfig;
+		[self fullShutdown];
+		if(formatSet && ![self setup]) {
+			processEntered = NO;
+			return nil;
+		}
+	}
+
+	if(!downmix) {
+		processEntered = NO;
+		return [self readChunk:4096];
+	}
+
+	AudioChunk *chunk = [self readChunkAsFloat32:4096];
+	if(!chunk || ![chunk frameCount]) {
+		processEntered = NO;
+		return nil;
+	}
+
+	double streamTimestamp = [chunk streamTimestamp];
+
+	size_t frameCount = [chunk frameCount];
+	NSData *sampleData = [chunk removeSamples:frameCount];
+
+	[downmix process:[sampleData bytes] frameCount:frameCount output:&outBuffer[0]];
+
+	AudioChunk *outputChunk = [[AudioChunk alloc] init];
+	[outputChunk setFormat:outputFormat];
+	if(outputChannelConfig) {
+		[outputChunk setChannelConfig:outputChannelConfig];
+	}
+	if([chunk isHDCD]) [outputChunk setHDCD];
+	[outputChunk setStreamTimestamp:streamTimestamp];
+	[outputChunk setStreamTimeRatio:[chunk streamTimeRatio]];
+	[outputChunk assignSamples:&outBuffer[0] frameCount:frameCount];
+
+	processEntered = NO;
+	return outputChunk;
+}
+
+@end

Audio/Chain/DSP/Downmix.m

@@ -283,7 +283,11 @@ static void *kDownmixProcessorContext = &kDownmixProcessorContext;
 }
 
 - (void)process:(const void *)inBuffer frameCount:(size_t)frames output:(void *)outBuffer {
-	if(inputFormat.mChannelsPerFrame > 2 && outConfig == AudioConfigStereo) {
+	if(inputFormat.mChannelsPerFrame == 2 && outConfig == AudioConfigStereo &&
+	   inConfig == (AudioChannelSideLeft | AudioChannelSideRight)) {
+		// Workaround for HRTF output
+		memcpy(outBuffer, inBuffer, frames * outputFormat.mBytesPerPacket);
+	} else if(inputFormat.mChannelsPerFrame > 2 && outConfig == AudioConfigStereo) {
 		downmix_to_stereo((const float *)inBuffer, inputFormat.mChannelsPerFrame, inConfig, (float *)outBuffer, frames);
 	} else if(inputFormat.mChannelsPerFrame > 1 && outConfig == AudioConfigMono) {
 		downmix_to_mono((const float *)inBuffer, inputFormat.mChannelsPerFrame, inConfig, (float *)outBuffer, frames);

Audio/Chain/InputNode.m

@@ -166,6 +166,7 @@ static void *kInputNodeContext = &kInputNodeContext;
 			DSPFSurroundNode *fsurround = [bufferChain fsurround];
 			DSPEqualizerNode *equalizer = [bufferChain equalizer];
 			DSPHRTFNode *hrtf = [bufferChain hrtf];
+			DSPDownmixNode *downmix = [bufferChain downmix];
 			DLog(@"SEEKING! Resetting Buffer");
 
 			// This resets the converter's buffer
@@ -177,6 +178,7 @@ static void *kInputNodeContext = &kInputNodeContext;
 			[fsurround resetBuffer];
 			[equalizer resetBuffer];
 			[hrtf resetBuffer];
+			[downmix resetBuffer];
 
 			DLog(@"Reset buffer!");
 

Audio/Chain/OutputNode.h

@@ -56,6 +56,9 @@
 - (AudioStreamBasicDescription)format;
 - (uint32_t)config;
 
+- (AudioStreamBasicDescription)deviceFormat;
+- (uint32_t)deviceChannelConfig;
+
 - (void)setVolume:(double)v;
 
 - (void)setShouldContinue:(BOOL)s;

Audio/Chain/OutputNode.m

@@ -136,6 +136,14 @@
 	return config;
 }
 
+- (AudioStreamBasicDescription)deviceFormat {
+	return [output deviceFormat];
+}
+
+- (uint32_t)deviceChannelConfig {
+	return [output deviceChannelConfig];
+}
+
 - (void)setFormat:(AudioStreamBasicDescription *)f channelConfig:(uint32_t)channelConfig {
 	format = *f;
 	config = channelConfig;
@@ -161,6 +169,10 @@
 			[converter setOutputFormat:format];
 			[converter inputFormatDidChange:[bufferChain inputFormat] inputConfig:[bufferChain inputConfig]];
 		}
+		DSPDownmixNode *downmix = [bufferChain downmix];
+		if(downmix && output) {
+			[downmix setOutputFormat:[output deviceFormat] withChannelConfig:[output deviceChannelConfig]];
+		}
 	}
 }
 

Audio/CogAudio.xcodeproj/project.pbxproj

@@ -47,6 +47,10 @@
 		8328995727CB51B700D7F028 /* SHA256Digest.h in Headers */ = {isa = PBXBuildFile; fileRef = 8328995527CB51B700D7F028 /* SHA256Digest.h */; };
 		8328995827CB51B700D7F028 /* SHA256Digest.m in Sources */ = {isa = PBXBuildFile; fileRef = 8328995627CB51B700D7F028 /* SHA256Digest.m */; };
 		8328995A27CB51C900D7F028 /* Security.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 8328995927CB51C900D7F028 /* Security.framework */; };
+		833738EA2D5EA52500278628 /* DSPDownmixNode.h in Headers */ = {isa = PBXBuildFile; fileRef = 833738E92D5EA52500278628 /* DSPDownmixNode.h */; };
+		833738EC2D5EA53500278628 /* DSPDownmixNode.m in Sources */ = {isa = PBXBuildFile; fileRef = 833738EB2D5EA53500278628 /* DSPDownmixNode.m */; };
+		833738EF2D5EA5B700278628 /* Downmix.m in Sources */ = {isa = PBXBuildFile; fileRef = 833738EE2D5EA5B700278628 /* Downmix.m */; };
+		833738F02D5EA5B700278628 /* Downmix.h in Headers */ = {isa = PBXBuildFile; fileRef = 833738ED2D5EA5B700278628 /* Downmix.h */; };
 		8347C7412796C58800FA8A7D /* NSFileHandle+CreateFile.h in Headers */ = {isa = PBXBuildFile; fileRef = 8347C73F2796C58800FA8A7D /* NSFileHandle+CreateFile.h */; };
 		8347C7422796C58800FA8A7D /* NSFileHandle+CreateFile.m in Sources */ = {isa = PBXBuildFile; fileRef = 8347C7402796C58800FA8A7D /* NSFileHandle+CreateFile.m */; };
 		834A41A9287A90AB00EB9D9B /* freesurround_decoder.h in Headers */ = {isa = PBXBuildFile; fileRef = 834A41A5287A90AB00EB9D9B /* freesurround_decoder.h */; };
@@ -57,8 +61,6 @@
 		834FD4ED27AF91220063BC83 /* AudioChunk.m in Sources */ = {isa = PBXBuildFile; fileRef = 834FD4EC27AF91220063BC83 /* AudioChunk.m */; };
 		834FD4F027AF93680063BC83 /* ChunkList.h in Headers */ = {isa = PBXBuildFile; fileRef = 834FD4EE27AF93680063BC83 /* ChunkList.h */; };
 		834FD4F127AF93680063BC83 /* ChunkList.m in Sources */ = {isa = PBXBuildFile; fileRef = 834FD4EF27AF93680063BC83 /* ChunkList.m */; };
-		83504165286447DA006B32CC /* Downmix.h in Headers */ = {isa = PBXBuildFile; fileRef = 83504163286447DA006B32CC /* Downmix.h */; };
-		83504166286447DA006B32CC /* Downmix.m in Sources */ = {isa = PBXBuildFile; fileRef = 83504164286447DA006B32CC /* Downmix.m */; };
 		8350416D28646149006B32CC /* CoreMedia.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 8350416C28646149006B32CC /* CoreMedia.framework */; };
 		835C88B1279811A500E28EAE /* hdcd_decode2.h in Headers */ = {isa = PBXBuildFile; fileRef = 835C88AF279811A500E28EAE /* hdcd_decode2.h */; };
 		835C88B2279811A500E28EAE /* hdcd_decode2.c in Sources */ = {isa = PBXBuildFile; fileRef = 835C88B0279811A500E28EAE /* hdcd_decode2.c */; };
@@ -173,6 +175,10 @@
 		8328995527CB51B700D7F028 /* SHA256Digest.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = SHA256Digest.h; path = ../../Utils/SHA256Digest.h; sourceTree = "<group>"; };
 		8328995627CB51B700D7F028 /* SHA256Digest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = SHA256Digest.m; path = ../../Utils/SHA256Digest.m; sourceTree = "<group>"; };
 		8328995927CB51C900D7F028 /* Security.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Security.framework; path = System/Library/Frameworks/Security.framework; sourceTree = SDKROOT; };
+		833738E92D5EA52500278628 /* DSPDownmixNode.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = DSPDownmixNode.h; sourceTree = "<group>"; };
+		833738EB2D5EA53500278628 /* DSPDownmixNode.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = DSPDownmixNode.m; sourceTree = "<group>"; };
+		833738ED2D5EA5B700278628 /* Downmix.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = Downmix.h; sourceTree = "<group>"; };
+		833738EE2D5EA5B700278628 /* Downmix.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = Downmix.m; sourceTree = "<group>"; };
 		8347C73F2796C58800FA8A7D /* NSFileHandle+CreateFile.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "NSFileHandle+CreateFile.h"; path = "../../Utils/NSFileHandle+CreateFile.h"; sourceTree = "<group>"; };
 		8347C7402796C58800FA8A7D /* NSFileHandle+CreateFile.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = "NSFileHandle+CreateFile.m"; path = "../../Utils/NSFileHandle+CreateFile.m"; sourceTree = "<group>"; };
 		834A41A5287A90AB00EB9D9B /* freesurround_decoder.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = freesurround_decoder.h; sourceTree = "<group>"; };
@@ -183,8 +189,6 @@
 		834FD4EC27AF91220063BC83 /* AudioChunk.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = AudioChunk.m; sourceTree = "<group>"; };
 		834FD4EE27AF93680063BC83 /* ChunkList.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = ChunkList.h; sourceTree = "<group>"; };
 		834FD4EF27AF93680063BC83 /* ChunkList.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = ChunkList.m; sourceTree = "<group>"; };
-		83504163286447DA006B32CC /* Downmix.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = Downmix.h; sourceTree = "<group>"; };
-		83504164286447DA006B32CC /* Downmix.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = Downmix.m; sourceTree = "<group>"; };
 		8350416C28646149006B32CC /* CoreMedia.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = CoreMedia.framework; path = System/Library/Frameworks/CoreMedia.framework; sourceTree = SDKROOT; };
 		835C88AF279811A500E28EAE /* hdcd_decode2.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = hdcd_decode2.h; sourceTree = "<group>"; };
 		835C88B0279811A500E28EAE /* hdcd_decode2.c */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.c; path = hdcd_decode2.c; sourceTree = "<group>"; };
@@ -378,8 +382,6 @@
 				834FD4EF27AF93680063BC83 /* ChunkList.m */,
 				8EC1225D0B993BD500C5B3AD /* ConverterNode.h */,
 				8EC1225E0B993BD500C5B3AD /* ConverterNode.m */,
-				83504163286447DA006B32CC /* Downmix.h */,
-				83504164286447DA006B32CC /* Downmix.m */,
 				17D21C7A0B8BE4BA00D1EBDE /* InputNode.h */,
 				17D21C7B0B8BE4BA00D1EBDE /* InputNode.m */,
 				17D21C7C0B8BE4BA00D1EBDE /* Node.h */,
@@ -538,6 +540,8 @@
 		83A349692D5C3F430096D530 /* DSP */ = {
 			isa = PBXGroup;
 			children = (
+				833738ED2D5EA5B700278628 /* Downmix.h */,
+				833738EE2D5EA5B700278628 /* Downmix.m */,
 				83F8431E2D5C6272008C123B /* HeadphoneFilter.h */,
 				83F8431F2D5C6272008C123B /* HeadphoneFilter.mm */,
 				83A349702D5C41810096D530 /* FSurroundFilter.h */,
@@ -550,6 +554,8 @@
 				83A349762D5C50B20096D530 /* DSPHRTFNode.m */,
 				83F843222D5C66DA008C123B /* DSPEqualizerNode.h */,
 				83F843242D5C66E9008C123B /* DSPEqualizerNode.m */,
+				833738E92D5EA52500278628 /* DSPDownmixNode.h */,
+				833738EB2D5EA53500278628 /* DSPDownmixNode.m */,
 			);
 			path = DSP;
 			sourceTree = "<group>";
@@ -575,9 +581,9 @@
 				8399CF2C27B5D1D5008751F1 /* NSDictionary+Merge.h in Headers */,
 				17D21CA90B8BE4BA00D1EBDE /* OutputNode.h in Headers */,
 				8328995427CB511000D7F028 /* RedundantPlaylistDataStore.h in Headers */,
-				83504165286447DA006B32CC /* Downmix.h in Headers */,
 				839E56E52879450300DFB5F4 /* HrtfData.h in Headers */,
 				83B74281289E027F005AAC28 /* CogAudio-Bridging-Header.h in Headers */,
+				833738F02D5EA5B700278628 /* Downmix.h in Headers */,
 				17D21CC70B8BE4BA00D1EBDE /* Status.h in Headers */,
 				17D21CF30B8BE5EF00D1EBDE /* CogSemaphore.h in Headers */,
 				835DD2682ACAF1D90057E319 /* OutputCoreAudio.h in Headers */,
@@ -611,6 +617,7 @@
 				835FAC5E27BCA14D00BA8562 /* BadSampleCleaner.h in Headers */,
 				8E8D3D2F0CBAEE6E00135C1B /* AudioContainer.h in Headers */,
 				B0575F2D0D687A0800411D77 /* Helper.h in Headers */,
+				833738EA2D5EA52500278628 /* DSPDownmixNode.h in Headers */,
 				07DB5F3E0ED353A900C2E3EF /* AudioMetadataWriter.h in Headers */,
 				839E56EA28794F6300DFB5F4 /* HrtfTypes.h in Headers */,
 			);
@@ -692,16 +699,17 @@
 				83A349772D5C50B20096D530 /* DSPHRTFNode.m in Sources */,
 				17D21CA60B8BE4BA00D1EBDE /* InputNode.m in Sources */,
 				83A3496A2D5C3F430096D530 /* DSPRubberbandNode.m in Sources */,
-				83504166286447DA006B32CC /* Downmix.m in Sources */,
 				8399CF2D27B5D1D5008751F1 /* NSDictionary+Merge.m in Sources */,
 				83F843252D5C66E9008C123B /* DSPEqualizerNode.m in Sources */,
 				834A41AB287A90AB00EB9D9B /* channelmaps.cpp in Sources */,
+				833738EC2D5EA53500278628 /* DSPDownmixNode.m in Sources */,
 				831A50162865A8800049CFE4 /* rsstate.cpp in Sources */,
 				17D21CA80B8BE4BA00D1EBDE /* Node.m in Sources */,
 				17D21CAA0B8BE4BA00D1EBDE /* OutputNode.m in Sources */,
 				835C88B2279811A500E28EAE /* hdcd_decode2.c in Sources */,
 				835FAC5F27BCA14D00BA8562 /* BadSampleCleaner.m in Sources */,
 				834FD4ED27AF91220063BC83 /* AudioChunk.m in Sources */,
+				833738EF2D5EA5B700278628 /* Downmix.m in Sources */,
 				17D21CF40B8BE5EF00D1EBDE /* CogSemaphore.m in Sources */,
 				839B83FA286D91ED00F529EE /* VisualizationController.swift in Sources */,
 				839E89A02D5DBA1700A13526 /* VisualizationNode.m in Sources */,

Audio/Output/OutputCoreAudio.h

@@ -22,8 +22,6 @@ using std::atomic_long;
 #import <stdatomic.h>
 #endif
 
-#import "Downmix.h"
-
 #import <CogAudio/CogAudio-Swift.h>
 
 #import <simd/simd.h>
@@ -93,8 +91,6 @@ using std::atomic_long;
 
 	size_t _bufferSize;
 
-	DownmixProcessor *downmixer;
-
 	VisualizationController *visController;
 
 	int inputRemain;
@@ -108,7 +104,6 @@ using std::atomic_long;
 	float *samplePtr;
 	float tempBuffer[512 * 32];
 	float inputBuffer[4096 * 32]; // 4096 samples times maximum supported channel count
-	float downmixBuffer[4096 * 8];
 
 #ifdef OUTPUT_LOG
 	FILE *_logFile;
@@ -133,4 +128,7 @@ using std::atomic_long;
 
 - (void)sustainHDCD;
 
+- (AudioStreamBasicDescription)deviceFormat;
+- (uint32_t)deviceChannelConfig;
+
 @end

Audio/Output/OutputCoreAudio.m

@@ -41,16 +41,6 @@ static void *kOutputCoreAudioContext = &kOutputCoreAudioContext;
 		uint32_t origConfig = config;
 		origFormat = format;
 
-		UInt32 srcChannels = format.mChannelsPerFrame;
-		UInt32 dstChannels = deviceFormat.mChannelsPerFrame;
-		if(srcChannels != dstChannels) {
-			format.mChannelsPerFrame = dstChannels;
-			format.mBytesPerFrame = ((format.mBitsPerChannel + 7) / 8) * dstChannels;
-			format.mBytesPerPacket = format.mBytesPerFrame * format.mFramesPerPacket;
-			downmixer = [[DownmixProcessor alloc] initWithInputFormat:origFormat inputConfig:origConfig andOutputFormat:format outputConfig:deviceChannelConfig];
-		} else {
-			downmixer = nil;
-		}
 		if(!streamFormatStarted || config != realStreamChannelConfig || memcmp(&realStreamFormat, &format, sizeof(format)) != 0) {
 			realStreamFormat = format;
 			realStreamChannelConfig = config;
@@ -598,18 +588,13 @@ current_device_listener(AudioObjectID inObjectID, UInt32 inNumberAddresses, cons
 
 	samplePtr = &inputBuffer[0];
 
-	if(samplesRendered) {
-		if(downmixer) {
-			[downmixer process:samplePtr frameCount:samplesRendered output:&downmixBuffer[0]];
-			samplePtr = &downmixBuffer[0];
-		}
-
 #ifdef OUTPUT_LOG
+	if(samplesRendered) {
 		size_t dataByteSize = samplesRendered * sizeof(float) * deviceFormat.mChannelsPerFrame;
 
 		fwrite(samplePtr, 1, dataByteSize, _logFile);
-#endif
 	}
+#endif
 
 	return samplesRendered;
 }
@@ -687,8 +672,6 @@ current_device_listener(AudioObjectID inObjectID, UInt32 inNumberAddresses, cons
 		outputDeviceID = -1;
 		restarted = NO;
 
-		downmixer = nil;
-
 		lastClippedSampleRate = 0.0;
 
 		inputRemain = 0;
@@ -856,4 +839,12 @@ current_device_listener(AudioObjectID inObjectID, UInt32 inNumberAddresses, cons
 	shouldPlayOutBuffer = s;
 }
 
+- (AudioStreamBasicDescription)deviceFormat {
+	return deviceFormat;
+}
+
+- (uint32_t)deviceChannelConfig {
+	return deviceChannelConfig;
+}
+
 @end