Add Sunshine protocol extension for passing HDR metadata

src/ControlStream.c

@@ -50,6 +50,7 @@ static bool stopping;
 static bool disconnectPending;
 static bool encryptedControlStream;
 static bool hdrEnabled;
+static SS_HDR_METADATA hdrMetadata;
 
 static int intervalGoodFrameCount;
 static int intervalTotalFrameCount;
@@ -275,6 +276,7 @@ int initializeControlStream(void) {
     encryptionCtx = PltCreateCryptoContext();
     decryptionCtx = PltCreateCryptoContext();
     hdrEnabled = false;
+    memset(&hdrMetadata, 0, sizeof(hdrMetadata));
 
     return 0;
 }
@@ -813,9 +815,24 @@ static void controlReceiveThreadFunc(void* context) {
 
                 BbInitializeWrappedBuffer(&bb, (char*)ctlHdr, sizeof(*ctlHdr), packetLength - sizeof(*ctlHdr), BYTE_ORDER_LITTLE);
 
-                // FIXME: There are 7 additional bytes that appear to always be all zeros. What do they mean?
-                // Is there some way that GFE tells us the HDR mastering metadata (NV_HDR_COLOR_DATA) set by the game?
                 BbGet8(&bb, &enableByte);
+                if (IS_SUNSHINE()) {
+                    // Zero the metadata buffer to properly handle older servers if we have to add new fields
+                    memset(&hdrMetadata, 0, sizeof(hdrMetadata));
+
+                    // Sunshine sends HDR metadata in this message too
+                    for (int i = 0; i < 3; i++) {
+                        BbGet16(&bb, &hdrMetadata.displayPrimaries[i].x);
+                        BbGet16(&bb, &hdrMetadata.displayPrimaries[i].y);
+                    }
+                    BbGet16(&bb, &hdrMetadata.whitePoint.x);
+                    BbGet16(&bb, &hdrMetadata.whitePoint.y);
+                    BbGet16(&bb, &hdrMetadata.maxDisplayLuminance);
+                    BbGet16(&bb, &hdrMetadata.minDisplayLuminance);
+                    BbGet16(&bb, &hdrMetadata.maxContentLightLevel);
+                    BbGet16(&bb, &hdrMetadata.maxFrameAverageLightLevel);
+                    BbGet16(&bb, &hdrMetadata.maxFullFrameLuminance);
+                }
 
                 hdrEnabled = (enableByte != 0);
                 ListenerCallbacks.setHdrMode(hdrEnabled);
@@ -1447,3 +1464,12 @@ int startControlStream(void) {
 bool LiGetCurrentHostDisplayHdrMode(void) {
     return hdrEnabled;
 }
+
+bool LiGetHdrMetadata(PSS_HDR_METADATA metadata) {
+    if (!IS_SUNSHINE() || !hdrEnabled) {
+        return false;
+    }
+
+    *metadata = hdrMetadata;
+    return true;
+}

src/Limelight.h

@@ -705,6 +705,34 @@ void LiCompleteVideoFrame(VIDEO_FRAME_HANDLE handle, int drStatus);
 // See ConnListenerSetHdrMode() for more details.
 bool LiGetCurrentHostDisplayHdrMode(void);
 
+typedef struct _SS_HDR_METADATA {
+    // RGB order
+    struct {
+        uint16_t x; // Normalized to 50,000
+        uint16_t y; // Normalized to 50,000
+    } displayPrimaries[3];
+
+    struct {
+        uint16_t x; // Normalized to 50,000
+        uint16_t y; // Normalized to 50,000
+    } whitePoint;
+
+    uint16_t maxDisplayLuminance; // Nits
+    uint16_t minDisplayLuminance; // 1/10000th of a nit
+
+    // These are content-specific values which may not be available for all hosts.
+    uint16_t maxContentLightLevel; // Nits
+    uint16_t maxFrameAverageLightLevel; // Nits
+
+    // These are display-specific values which may not be available for all hosts.
+    uint16_t maxFullFrameLuminance; // Nits
+} SS_HDR_METADATA, *PSS_HDR_METADATA;
+
+// This function populates the provided mastering metadata struct with the HDR metadata
+// from the host PC's monitor and content (if available). It is only valid to call this
+// function when HDR mode is active on the host. This is a Sunshine protocol extension.
+bool LiGetHdrMetadata(PSS_HDR_METADATA metadata);
+
 // This function requests an IDR frame from the host. Typically this is done using DR_NEED_IDR, but clients
 // processing frames asynchronously may need to reset their decoder state even after returning DR_OK for
 // the prior frame. Rather than wait for a new frame and return DR_NEED_IDR for that one, they can just