Implement HDR support for Linux KMS capture backend (#1994)

Co-authored-by: ReenigneArcher <42013603+ReenigneArcher@users.noreply.github.com>

docs/source/about/setup.rst

@@ -586,15 +586,29 @@ Considerations
 
 HDR Support
 -----------
-Streaming HDR content is supported for Windows hosts with NVIDIA, AMD, or Intel GPUs that support encoding HEVC Main 10.
-You must have an HDR-capable display or EDID emulator dongle connected to your host PC to activate HDR in Windows.
+Streaming HDR content is officially supported on Windows hosts and experimentally supported for Linux hosts.
 
-- Ensure you enable the HDR option in your Moonlight client settings, otherwise the stream will be SDR.
-- A good HDR experience relies on proper HDR display calibration both in Windows and in game. HDR calibration can differ significantly between client and host displays.
-- We recommend calibrating the display by streaming the Windows HDR Calibration app to your client device and saving an HDR calibration profile to use while streaming.
-- You may also need to tune the brightness slider or HDR calibration options in game to the different HDR brightness capabilities of your client's display.
-- Older games that use NVIDIA-specific NVAPI HDR rather than native Windows 10 OS HDR support may not display in HDR.
-- Some GPUs can produce lower image quality or encoding performance when streaming in HDR compared to SDR.
+- General HDR support information and requirements:
+
+  - HDR must be activated in the host OS, which may require an HDR-capable display or EDID emulator dongle connected to your host PC.
+  - You must also enable the HDR option in your Moonlight client settings, otherwise the stream will be SDR (and probably overexposed if your host is HDR).
+  - A good HDR experience relies on proper HDR display calibration both in the OS and in game. HDR calibration can differ significantly between client and host displays.
+  - You may also need to tune the brightness slider or HDR calibration options in game to the different HDR brightness capabilities of your client's display.
+  - Some GPUs video encoders can produce lower image quality or encoding performance when streaming in HDR compared to SDR.
+
+- Additional information:
+
+.. tab:: Windows
+
+     - HDR streaming is supported for Intel, AMD, and NVIDIA GPUs that support encoding HEVC Main 10 or AV1 10-bit profiles.
+     - We recommend calibrating the display by streaming the Windows HDR Calibration app to your client device and saving an HDR calibration profile to use while streaming.
+     - Older games that use NVIDIA-specific NVAPI HDR rather than native Windows HDR support may not display properly in HDR.
+
+.. tab:: Linux
+
+     - HDR streaming is supported for Intel and AMD GPUs that support encoding HEVC Main 10 or AV1 10-bit profiles using VAAPI.
+     - The KMS capture backend is required for HDR capture. Other capture methods, like NvFBC or X11, do not support HDR.
+     - You will need a desktop environment with a compositor that supports HDR rendering, such as Gamescope or KDE Plasma 6.
 
 .. seealso::
    `Arch wiki on HDR Support for Linux <https://wiki.archlinux.org/title/HDR_monitor_support>`__ and

src/platform/linux/graphics.cpp

@@ -662,19 +662,19 @@ namespace egl {
   }
 
   std::optional<sws_t>
-  sws_t::make(int in_width, int in_height, int out_width, int out_heigth, gl::tex_t &&tex) {
+  sws_t::make(int in_width, int in_height, int out_width, int out_height, gl::tex_t &&tex) {
     sws_t sws;
 
     sws.serial = std::numeric_limits<std::uint64_t>::max();
 
     // Ensure aspect ratio is maintained
-    auto scalar = std::fminf(out_width / (float) in_width, out_heigth / (float) in_height);
+    auto scalar = std::fminf(out_width / (float) in_width, out_height / (float) in_height);
     auto out_width_f = in_width * scalar;
     auto out_height_f = in_height * scalar;
 
     // result is always positive
     auto offsetX_f = (out_width - out_width_f) / 2;
-    auto offsetY_f = (out_heigth - out_height_f) / 2;
+    auto offsetY_f = (out_height - out_height_f) / 2;
 
     sws.out_width = out_width_f;
     sws.out_height = out_height_f;
@@ -806,12 +806,12 @@ namespace egl {
   }
 
   std::optional<sws_t>
-  sws_t::make(int in_width, int in_height, int out_width, int out_heigth) {
+  sws_t::make(int in_width, int in_height, int out_width, int out_height, GLint gl_tex_internal_fmt) {
     auto tex = gl::tex_t::make(2);
     gl::ctx.BindTexture(GL_TEXTURE_2D, tex[0]);
-    gl::ctx.TexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, in_width, in_height);
+    gl::ctx.TexStorage2D(GL_TEXTURE_2D, 1, gl_tex_internal_fmt, in_width, in_height);
 
-    return make(in_width, in_height, out_width, out_heigth, std::move(tex));
+    return make(in_width, in_height, out_width, out_height, std::move(tex));
   }
 
   void

src/platform/linux/graphics.h

@@ -314,9 +314,9 @@ namespace egl {
   class sws_t {
   public:
     static std::optional<sws_t>
-    make(int in_width, int in_height, int out_width, int out_heigth, gl::tex_t &&tex);
+    make(int in_width, int in_height, int out_width, int out_height, gl::tex_t &&tex);
     static std::optional<sws_t>
-    make(int in_width, int in_height, int out_width, int out_heigth);
+    make(int in_width, int in_height, int out_width, int out_height, GLint gl_tex_internal_fmt);
 
     // Convert the loaded image into the first two framebuffers
     int

src/platform/linux/kmsgrab.cpp

@@ -105,6 +105,7 @@ namespace platf {
     using crtc_t = util::safe_ptr<drmModeCrtc, drmModeFreeCrtc>;
     using obj_prop_t = util::safe_ptr<drmModeObjectProperties, drmModeFreeObjectProperties>;
     using prop_t = util::safe_ptr<drmModePropertyRes, drmModeFreeProperty>;
+    using prop_blob_t = util::safe_ptr<drmModePropertyBlobRes, drmModeFreePropertyBlob>;
 
     using conn_type_count_t = std::map<std::uint32_t, std::uint32_t>;
 
@@ -135,6 +136,9 @@ namespace platf {
       // For example HDMI-A-{index} or HDMI-{index}
       std::uint32_t index;
 
+      // ID of the connector
+      std::uint32_t connector_id;
+
       bool connected;
     };
 
@@ -336,13 +340,22 @@ namespace platf {
         return false;
       }
 
+      std::optional<std::uint64_t>
+      prop_value_by_name(const std::vector<std::pair<prop_t, std::uint64_t>> &props, std::string_view name) {
+        for (auto &[prop, val] : props) {
+          if (prop->name == name) {
+            return val;
+          }
+        }
+        return std::nullopt;
+      }
+
       std::uint32_t
       get_panel_orientation(std::uint32_t plane_id) {
         auto props = plane_props(plane_id);
-        for (auto &[prop, val] : props) {
-          if (prop->name == "rotation"sv) {
-            return val;
-          }
+        auto value = prop_value_by_name(props, "rotation"sv);
+        if (value) {
+          return *value;
         }
 
         BOOST_LOG(error) << "Failed to determine panel orientation, defaulting to landscape.";
@@ -392,6 +405,7 @@ namespace platf {
             conn->connector_type,
             crtc_id,
             index,
+            conn->connector_id,
             conn->connection == DRM_MODE_CONNECTED,
           });
         });
@@ -414,6 +428,9 @@ namespace platf {
       std::vector<std::pair<prop_t, std::uint64_t>>
       props(std::uint32_t id, std::uint32_t type) {
         obj_prop_t obj_prop = drmModeObjectGetProperties(fd.el, id, type);
+        if (!obj_prop) {
+          return {};
+        }
 
         std::vector<std::pair<prop_t, std::uint64_t>> props;
         props.reserve(obj_prop->count_props);
@@ -651,12 +668,24 @@ namespace platf {
               offset_y = crtc->y;
             }
 
-            this->card = std::move(card);
-
             plane_id = plane->plane_id;
             crtc_id = plane->crtc_id;
-            crtc_index = this->card.get_crtc_index_by_id(plane->crtc_id);
+            crtc_index = card.get_crtc_index_by_id(plane->crtc_id);
 
+            // Find the connector for this CRTC
+            kms::conn_type_count_t conn_type_count;
+            for (auto &connector : card.monitors(conn_type_count)) {
+              if (connector.crtc_id == crtc_id) {
+                BOOST_LOG(info) << "Found connector ID ["sv << connector.connector_id << ']';
+
+                connector_id = connector.connector_id;
+
+                auto connector_props = card.connector_props(*connector_id);
+                hdr_metadata_blob_id = card.prop_value_by_name(connector_props, "HDR_OUTPUT_METADATA"sv);
+              }
+            }
+
+            this->card = std::move(card);
             goto break_loop;
           }
         }
@@ -703,6 +732,83 @@ namespace platf {
         return 0;
       }
 
+      bool
+      is_hdr() {
+        if (!hdr_metadata_blob_id || *hdr_metadata_blob_id == 0) {
+          return false;
+        }
+
+        prop_blob_t hdr_metadata_blob = drmModeGetPropertyBlob(card.fd.el, *hdr_metadata_blob_id);
+        if (hdr_metadata_blob == nullptr) {
+          BOOST_LOG(error) << "Unable to get HDR metadata blob: "sv << strerror(errno);
+          return false;
+        }
+
+        if (hdr_metadata_blob->length < sizeof(uint32_t) + sizeof(hdr_metadata_infoframe)) {
+          BOOST_LOG(error) << "HDR metadata blob is too small: "sv << hdr_metadata_blob->length;
+          return false;
+        }
+
+        auto raw_metadata = (hdr_output_metadata *) hdr_metadata_blob->data;
+        if (raw_metadata->metadata_type != 0) {  // HDMI_STATIC_METADATA_TYPE1
+          BOOST_LOG(error) << "Unknown HDMI_STATIC_METADATA_TYPE value: "sv << raw_metadata->metadata_type;
+          return false;
+        }
+
+        if (raw_metadata->hdmi_metadata_type1.metadata_type != 0) {  // Static Metadata Type 1
+          BOOST_LOG(error) << "Unknown secondary metadata type value: "sv << raw_metadata->hdmi_metadata_type1.metadata_type;
+          return false;
+        }
+
+        // We only support Traditional Gamma SDR or SMPTE 2084 PQ HDR EOTFs.
+        // Print a warning if we encounter any others.
+        switch (raw_metadata->hdmi_metadata_type1.eotf) {
+          case 0:  // HDMI_EOTF_TRADITIONAL_GAMMA_SDR
+            return false;
+          case 1:  // HDMI_EOTF_TRADITIONAL_GAMMA_HDR
+            BOOST_LOG(warning) << "Unsupported HDR EOTF: Traditional Gamma"sv;
+            return true;
+          case 2:  // HDMI_EOTF_SMPTE_ST2084
+            return true;
+          case 3:  // HDMI_EOTF_BT_2100_HLG
+            BOOST_LOG(warning) << "Unsupported HDR EOTF: HLG"sv;
+            return true;
+          default:
+            BOOST_LOG(warning) << "Unsupported HDR EOTF: "sv << raw_metadata->hdmi_metadata_type1.eotf;
+            return true;
+        }
+      }
+
+      bool
+      get_hdr_metadata(SS_HDR_METADATA &metadata) {
+        // This performs all the metadata validation
+        if (!is_hdr()) {
+          return false;
+        }
+
+        prop_blob_t hdr_metadata_blob = drmModeGetPropertyBlob(card.fd.el, *hdr_metadata_blob_id);
+        if (hdr_metadata_blob == nullptr) {
+          BOOST_LOG(error) << "Unable to get HDR metadata blob: "sv << strerror(errno);
+          return false;
+        }
+
+        auto raw_metadata = (hdr_output_metadata *) hdr_metadata_blob->data;
+
+        for (int i = 0; i < 3; i++) {
+          metadata.displayPrimaries[i].x = raw_metadata->hdmi_metadata_type1.display_primaries[i].x;
+          metadata.displayPrimaries[i].y = raw_metadata->hdmi_metadata_type1.display_primaries[i].y;
+        }
+
+        metadata.whitePoint.x = raw_metadata->hdmi_metadata_type1.white_point.x;
+        metadata.whitePoint.y = raw_metadata->hdmi_metadata_type1.white_point.y;
+        metadata.maxDisplayLuminance = raw_metadata->hdmi_metadata_type1.max_display_mastering_luminance;
+        metadata.minDisplayLuminance = raw_metadata->hdmi_metadata_type1.min_display_mastering_luminance;
+        metadata.maxContentLightLevel = raw_metadata->hdmi_metadata_type1.max_cll;
+        metadata.maxFrameAverageLightLevel = raw_metadata->hdmi_metadata_type1.max_fall;
+
+        return true;
+      }
+
       void
       update_cursor() {
         if (cursor_plane_id < 0) {
@@ -881,6 +987,15 @@ namespace platf {
 
       inline capture_e
       refresh(file_t *file, egl::surface_descriptor_t *sd) {
+        // Check for a change in HDR metadata
+        if (connector_id) {
+          auto connector_props = card.connector_props(*connector_id);
+          if (hdr_metadata_blob_id != card.prop_value_by_name(connector_props, "HDR_OUTPUT_METADATA"sv)) {
+            BOOST_LOG(info) << "Reinitializing capture after HDR metadata change"sv;
+            return capture_e::reinit;
+          }
+        }
+
         plane_t plane = drmModeGetPlane(card.fd.el, plane_id);
 
         auto fb = card.fb(plane.get());
@@ -944,6 +1059,9 @@ namespace platf {
       int crtc_id;
       int crtc_index;
 
+      std::optional<uint32_t> connector_id;
+      std::optional<uint64_t> hdr_metadata_blob_id;
+
       int cursor_plane_id;
       cursor_t captured_cursor {};
 

src/platform/linux/vaapi.cpp

@@ -130,12 +130,12 @@ namespace va {
     }
 
     int
-    set_frame(AVFrame *frame, AVBufferRef *hw_frames_ctx) override {
+    set_frame(AVFrame *frame, AVBufferRef *hw_frames_ctx_buf) override {
       this->hwframe.reset(frame);
       this->frame = frame;
 
       if (!frame->buf[0]) {
-        if (av_hwframe_get_buffer(hw_frames_ctx, frame, 0)) {
+        if (av_hwframe_get_buffer(hw_frames_ctx_buf, frame, 0)) {
           BOOST_LOG(error) << "Couldn't get hwframe for VAAPI"sv;
           return -1;
         }
@@ -143,6 +143,7 @@ namespace va {
 
       va::DRMPRIMESurfaceDescriptor prime;
       va::VASurfaceID surface = (std::uintptr_t) frame->data[3];
+      auto hw_frames_ctx = (AVHWFramesContext *) hw_frames_ctx_buf->data;
 
       auto status = vaExportSurfaceHandle(
         this->va_display,
@@ -194,7 +195,25 @@ namespace va {
         return -1;
       }
 
-      auto sws_opt = egl::sws_t::make(width, height, frame->width, frame->height);
+      // Decide the bit depth format of the backing texture based the target frame format
+      GLint gl_format;
+      switch (hw_frames_ctx->sw_format) {
+        case AV_PIX_FMT_YUV420P:
+        case AV_PIX_FMT_NV12:
+          gl_format = GL_RGBA8;
+          break;
+
+        case AV_PIX_FMT_YUV420P10:
+        case AV_PIX_FMT_P010:
+          gl_format = GL_RGB10_A2;
+          break;
+
+        default:
+          BOOST_LOG(error) << "Unsupported pixel format for VA frame: "sv << hw_frames_ctx->sw_format;
+          return -1;
+      }
+
+      auto sws_opt = egl::sws_t::make(width, height, frame->width, frame->height, gl_format);
       if (!sws_opt) {
         return -1;
       }