Remove separate codec, HDR, and remote bitrate adjustments

We currently scale bitrate based on both remote vs local, SDR vs HDR, and H.264 vs
HEVC vs AV1. This has led to a lot of user confusion wondering why the bitrate
doesn't seem to match their selection in some configurations.

In H.264 local streams, we will currently overshoot the selected bitrate by about
20% due to FEC, while remote streams will be right around the selected bitrate due
to remote-specific FEC bitrate adjustments.

HEVC and AV1 streams (as configured by most clients) basically behave similarly
between local and remote, since the codec bitrate adjustment factor of 75% is nearly
the same as the FEC bitrate adjustment factor of 80%. However, this adjustment was
only performed for SDR streams so local HDR streams would overshoot like H.264.

This change cleans up all this mess by using a single non-codec-specific video
bitrate adjustment for FEC in all cases. It also allows Sunshine to perform the FEC
adjustment on its end if the default FEC value of 20% has been overridden by the
user or if we implement dynamic FEC support in the future.

The net result is HEVC and AV1 SDR streams will only see a tiny bitrate increase,
but HDR and H.264 may see noticable 20% bitrate reductions that may require the
user to adjust their bitrate setting to reach the effective value they got before.
However, the new behavior should be more intuitive for users going forward since
changing codecs, using a VPN, or enabling HDR won't cause significant changes to the
video bitrate.

src/SdpGenerator.c

@@ -258,7 +258,7 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
     int audioChannelCount;
     int audioChannelMask;
     int err;
-    int bitrate;
+    int adjustedBitrate;
 
     // This must have been resolved to either local or remote by now
     LC_ASSERT(StreamConfig.streamingRemotely != STREAM_CFG_AUTO);
@@ -289,44 +289,43 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
     err |= addAttributeString(&optionHead, "x-nv-video[0].timeoutLengthMs", "7000");
     err |= addAttributeString(&optionHead, "x-nv-video[0].framesWithInvalidRefThreshold", "0");
 
+    // 20% of the video bitrate will added to the user-specified bitrate for FEC
+    adjustedBitrate = (int)(StreamConfig.bitrate * 0.80);
+
     // Use more strict bitrate logic when streaming remotely. The theory here is that remote
     // streaming is much more bandwidth sensitive. Someone might select 5 Mbps because that's
     // really all they have, so we need to be careful not to exceed the cap, even counting
     // things like audio and control data.
     if (StreamConfig.streamingRemotely == STREAM_CFG_REMOTE) {
-        // 20% of the video bitrate will added to the user-specified bitrate for FEC
-        bitrate = (int)(OriginalVideoBitrate * 0.80);
-
         // Subtract 500 Kbps to leave room for audio and control. On remote streams,
         // GFE will use 96Kbps stereo audio. For local streams, it will choose 512Kbps.
-        if (bitrate > 500) {
-            bitrate -= 500;
+        if (adjustedBitrate > 500) {
+            adjustedBitrate -= 500;
         }
     }
-    else {
-        bitrate = StreamConfig.bitrate;
-    }
-
-    // If the calculated bitrate (with the HEVC multiplier in effect) is less than this,
-    // use the lower of the two bitrate values.
-    bitrate = StreamConfig.bitrate < bitrate ? StreamConfig.bitrate : bitrate;
 
     // GFE currently imposes a limit of 100 Mbps for the video bitrate. It will automatically
     // impose that on maximumBitrateKbps but not on initialBitrateKbps. We will impose the cap
     // ourselves so initialBitrateKbps does not exceed maximumBitrateKbps.
-    bitrate = bitrate > 100000 ? 100000 : bitrate;
+    adjustedBitrate = adjustedBitrate > 100000 ? 100000 : adjustedBitrate;
 
     // We don't support dynamic bitrate scaling properly (it tends to bounce between min and max and never
     // settle on the optimal bitrate if it's somewhere in the middle), so we'll just latch the bitrate
     // to the requested value.
     if (AppVersionQuad[0] >= 5) {
-        snprintf(payloadStr, sizeof(payloadStr), "%d", bitrate);
+        snprintf(payloadStr, sizeof(payloadStr), "%d", adjustedBitrate);
 
         err |= addAttributeString(&optionHead, "x-nv-video[0].initialBitrateKbps", payloadStr);
         err |= addAttributeString(&optionHead, "x-nv-video[0].initialPeakBitrateKbps", payloadStr);
 
         err |= addAttributeString(&optionHead, "x-nv-vqos[0].bw.minimumBitrateKbps", payloadStr);
         err |= addAttributeString(&optionHead, "x-nv-vqos[0].bw.maximumBitrateKbps", payloadStr);
+
+        // Send the configured bitrate to Sunshine hosts, so they can adjust for dynamic FEC percentage
+        if (IS_SUNSHINE()) {
+            snprintf(payloadStr, sizeof(payloadStr), "%u", StreamConfig.bitrate);
+            err |= addAttributeString(&optionHead, "x-ml-video.configuredBitrateKbps", payloadStr);
+        }
     }
     else {
         if (StreamConfig.streamingRemotely == STREAM_CFG_REMOTE) {
@@ -334,7 +333,7 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
             err |= addAttributeString(&optionHead, "x-nv-video[0].peakBitrate", "4");
         }
 
-        snprintf(payloadStr, sizeof(payloadStr), "%d", bitrate);
+        snprintf(payloadStr, sizeof(payloadStr), "%d", adjustedBitrate);
         err |= addAttributeString(&optionHead, "x-nv-vqos[0].bw.minimumBitrate", payloadStr);
         err |= addAttributeString(&optionHead, "x-nv-vqos[0].bw.maximumBitrate", payloadStr);
     }
@@ -447,8 +446,7 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
     }
 
     if (AppVersionQuad[0] >= 7) {
-        // Decide to use HQ audio based on the original video bitrate, not the HEVC-adjusted value
-        if (OriginalVideoBitrate >= HIGH_AUDIO_BITRATE_THRESHOLD && audioChannelCount > 2 &&
+        if (StreamConfig.bitrate >= HIGH_AUDIO_BITRATE_THRESHOLD && audioChannelCount > 2 &&
                 HighQualitySurroundSupported && (AudioCallbacks.capabilities & CAPABILITY_SLOW_OPUS_DECODER) == 0) {
             // Enable high quality mode for surround sound
             err |= addAttributeString(&optionHead, "x-nv-audio.surround.AudioQuality", "1");
@@ -466,7 +464,7 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
 
             if ((AudioCallbacks.capabilities & CAPABILITY_SLOW_OPUS_DECODER) ||
                      ((AudioCallbacks.capabilities & CAPABILITY_SUPPORTS_ARBITRARY_AUDIO_DURATION) != 0 &&
-                       OriginalVideoBitrate < LOW_AUDIO_BITRATE_TRESHOLD)) {
+                       StreamConfig.bitrate < LOW_AUDIO_BITRATE_TRESHOLD)) {
                 // Use 10 ms packets for slow devices and networks to balance latency and bandwidth usage
                 AudioPacketDuration = 10;
             }