From a8b01d6c294561f67c145ae66be7054ed514bcad Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Sun, 27 May 2018 18:45:09 -0700
Subject: [PATCH] Enable high quality surround sound when the video bitrate is
 over 15 Mbps

---
 src/AudioStream.c        | 13 ++++++++++---
 src/Connection.c         |  1 +
 src/Limelight-internal.h |  1 +
 src/SdpGenerator.c       | 14 ++++++++++++++
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/AudioStream.c b/src/AudioStream.c
index 8d9ecec..ff4c0b1 100644
--- a/src/AudioStream.c
+++ b/src/AudioStream.c
@@ -17,7 +17,7 @@ static unsigned short lastSeq;
 
 #define RTP_PORT 48000
 
-#define MAX_PACKET_SIZE 400
+#define MAX_PACKET_SIZE 1400
 
 // This is much larger than we should typically have buffered, but
 // it needs to be. We need a cushion in case our thread gets blocked
@@ -282,9 +282,16 @@ void stopAudioStream(void) {
 
 int startAudioStream(void* audioContext, int arFlags) {
     int err;
+    OPUS_MULTISTREAM_CONFIGURATION chosenConfig;
 
-    err = AudioCallbacks.init(StreamConfig.audioConfiguration,
-        opusConfigArray[StreamConfig.audioConfiguration], audioContext, arFlags);
+    memcpy(&chosenConfig, opusConfigArray[StreamConfig.audioConfiguration], sizeof(chosenConfig));
+    if (HighQualitySurroundEnabled) {
+        // With high quality mode enabled, the encoder stops using coupled streams
+        chosenConfig.coupledStreams = 0;
+        chosenConfig.streams = chosenConfig.channelCount;
+    }
+
+    err = AudioCallbacks.init(StreamConfig.audioConfiguration, &chosenConfig, audioContext, arFlags);
     if (err != 0) {
         return err;
     }
diff --git a/src/Connection.c b/src/Connection.c
index dee8bfa..b763043 100644
--- a/src/Connection.c
+++ b/src/Connection.c
@@ -18,6 +18,7 @@ DECODER_RENDERER_CALLBACKS VideoCallbacks;
 AUDIO_RENDERER_CALLBACKS AudioCallbacks;
 int NegotiatedVideoFormat;
 volatile int ConnectionInterrupted;
+int HighQualitySurroundEnabled;
 
 // Connection stages
 static const char* stageNames[STAGE_MAX] = {
diff --git a/src/Limelight-internal.h b/src/Limelight-internal.h
index 4ed1f02..e9bc8bb 100644
--- a/src/Limelight-internal.h
+++ b/src/Limelight-internal.h
@@ -20,6 +20,7 @@ extern DECODER_RENDERER_CALLBACKS VideoCallbacks;
 extern AUDIO_RENDERER_CALLBACKS AudioCallbacks;
 extern int NegotiatedVideoFormat;
 extern volatile int ConnectionInterrupted;
+extern int HighQualitySurroundEnabled;
 
 #ifndef UINT24_MAX
 #define UINT24_MAX 0xFFFFFF
diff --git a/src/SdpGenerator.c b/src/SdpGenerator.c
index c59df53..d63de22 100644
--- a/src/SdpGenerator.c
+++ b/src/SdpGenerator.c
@@ -12,6 +12,7 @@
 #define CHANNEL_MASK_51_SURROUND 0xFC
 
 #define LOW_BITRATE_THRESHOLD 5000
+#define HIGH_BITRATE_THRESHOLD 15000
 
 typedef struct _SDP_OPTION {
     char name[MAX_OPTION_NAME_LEN + 1];
@@ -362,6 +363,19 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
         }
 
         if (AppVersionQuad[0] >= 7) {
+            if (StreamConfig.bitrate > HIGH_BITRATE_THRESHOLD && audioChannelCount > 2) {
+                // Enable high quality mode for surround sound
+                err |= addAttributeString(&optionHead, "x-nv-audio.surround.AudioQuality", "1");
+
+                // Let the audio stream code know that it needs to disable coupled streams when
+                // decoding this audio stream.
+                HighQualitySurroundEnabled = 1;
+            }
+            else {
+                err |= addAttributeString(&optionHead, "x-nv-audio.surround.AudioQuality", "0");
+                HighQualitySurroundEnabled = 0;
+            }
+
             if (StreamConfig.bitrate < LOW_BITRATE_THRESHOLD && audioChannelCount == 2) {
                 // At low bitrates, cap the stereo audio bitrate to reduce data usage. For some reason,
                 // GFE seems to always enable high quality (512 Kbps) mode for stereo even though we