Source: Add support for WGL_NV_DX_interop on windows

Allows us to share textures between OpenGL and Direct3D saving us the
reading into ram and then copying back into vram. On a 720p video it
saved ~1ms in Debug build.

src/mpv-backend.c

@@ -208,13 +208,18 @@ void mpvs_handle_events(struct mpv_source* context)
 
 void mpvs_render(struct mpv_source* context)
 {
-#if !defined(WIN32)
+#if defined(WIN32)
+    if (wgl_have_NV_DX_interop)
+        wgl_lock_shared_texture(context);
+#else
     // make sure that we restore the current program after mpv is done
     // as obs will not load the progam because it internally keeps track
     // of the current program and only loads it if it has changed
     GLuint currentProgram;
     context->_glGetIntegerv(GL_CURRENT_PROGRAM, (GLint*)&currentProgram);
 #endif
+
+
     mpv_render_frame_info info;
 
     mpv_render_param params[] = {
@@ -234,20 +239,23 @@ void mpvs_render(struct mpv_source* context)
         obs_log(LOG_ERROR, "mpv render error: %s", mpv_error_string(result));
 
 #if defined(WIN32)
-    if (context->media_state == OBS_MEDIA_STATE_PLAYING) {
-        uint8_t* ptr;
-        uint32_t linesize;
-        if (gs_texture_map(context->video_buffer, &ptr, &linesize)) {
-            context->_glBindFramebuffer(GL_FRAMEBUFFER, context->fbo);
-            context->_glReadPixels(0, 0, context->d3d_width, context->d3d_height, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
+    if (wgl_have_NV_DX_interop) {
+        wgl_unlock_shared_texture(context);
+    } else {
+        if (context->media_state == OBS_MEDIA_STATE_PLAYING) {
+            uint8_t* ptr;
+            uint32_t linesize;
+            if (gs_texture_map(context->video_buffer, &ptr, &linesize)) {
+                context->_glBindFramebuffer(GL_FRAMEBUFFER, context->fbo);
+                context->_glReadPixels(0, 0, context->d3d_width, context->d3d_height, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
+            }
+            gs_texture_unmap(context->video_buffer);
         }
-        gs_texture_unmap(context->video_buffer);
     }
-#endif
-
-#if !defined(WIN32)
+#else
     context->_glUseProgram(currentProgram);
 #endif
+
 }
 
 void mpvs_init(struct mpv_source* context)
@@ -461,7 +469,7 @@ void mpvs_generate_texture(struct mpv_source* context)
 #if defined(WIN32)
      if (context->video_buffer) 
         gs_texture_destroy(context->video_buffer);
-     context->video_buffer = gs_texture_create(context->d3d_width, context->d3d_height, GS_RGBA, 1, NULL, GS_DYNAMIC);
+     context->video_buffer = gs_texture_create(context->d3d_width, context->d3d_height, GS_RGBA, 1, NULL, wgl_have_NV_DX_interop ? 0 : GS_DYNAMIC);
 
      context->_glBindTexture(GL_TEXTURE_2D, 0);
 
@@ -481,6 +489,10 @@ void mpvs_generate_texture(struct mpv_source* context)
     context->_glGenFramebuffers(1, &context->fbo);
     context->_glBindFramebuffer(GL_FRAMEBUFFER, context->fbo);
     context->_glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, context->wgl_texture, 0);
+
+    if (wgl_have_NV_DX_interop) {
+        wgl_init_shared_gl_texture(context);
+    }
 #else
     if (context->video_buffer) {
         gs_texture_destroy(context->video_buffer);

src/mpv-source.h

@@ -161,4 +161,8 @@ struct mpv_source {
     obs_source_t* jack_source;
     char* jack_port_name;   // name of the jack capture source
     char* jack_client_name; // name of the jack client mpv opens for audio output
+
+#if defined(WIN32)
+    HANDLE gl_shared_texture_handle;
+#endif
 };

src/wgl.c

@@ -1,17 +1,16 @@
 #include "wgl.h"
-
-#include <glad/glad_wgl.h>
 #include <obs-module.h>
 #include <plugin-support.h>
-#include <Windows.h>
 
 WNDCLASSEX wc;
 HWND hwnd;
 HGLRC hrc;
 HDC hdc;
+HANDLE wgl_dx_device;
 
 static const char* dummy_window_class = "GLDummyWindow-obs-mpv";
 static bool registered_dummy_window_class = false;
+bool wgl_have_NV_DX_interop = false;
 
 struct dummy_context {
     HWND hwnd;
@@ -389,6 +388,13 @@ bool wgl_init()
     if (glVersion) {
         obs_log(LOG_INFO, "OpenGL Version: %s\n", glVersion);
     }
+
+    wgl_dx_device = wglDXOpenDeviceNV(gs_get_device_obj());
+    if (wgl_dx_device) {
+        wgl_have_NV_DX_interop = true;
+        obs_log(LOG_INFO, "NV_DX_interop extension is supported, sharing texture between OpenGL and Direct3D");
+    }
+
     init_result = true;
     return true;
 fail:
@@ -398,8 +404,9 @@ bool wgl_init()
 
 void wgl_deinit()
 {
-    // Cleanup
     wglMakeCurrent(NULL, NULL);
+    if (wgl_dx_device)
+        wglDXCloseDeviceNV(wgl_dx_device);
     wglDeleteContext(hrc);
     ReleaseDC(hwnd, hdc);
     DestroyWindow(hwnd);
@@ -415,3 +422,21 @@ void wgl_exit_context()
 {
     wglMakeCurrent(NULL, NULL);
 }
+
+void wgl_init_shared_gl_texture(void* context)
+{
+    struct mpv_source* src = context;
+    src->gl_shared_texture_handle = wglDXRegisterObjectNV(wgl_dx_device,
+        gs_texture_get_obj(src->video_buffer),
+        src->wgl_texture,
+        GL_TEXTURE_2D,
+        WGL_ACCESS_WRITE_DISCARD_NV);
+}
+
+void wgl_free_shared_gl_texture(void* context)
+{
+    struct mpv_source* src = context;
+    if (src->gl_shared_texture_handle)
+        wglDXUnregisterObjectNV(wgl_dx_device, src->gl_shared_texture_handle);
+    src->gl_shared_texture_handle = 0;
+}

src/wgl.h

@@ -1,10 +1,49 @@
 #pragma once
 #include <stdbool.h>
 
+#if defined(WIN32)
+#include <Windows.h>
+#include <glad/glad_wgl.h>
+#include "mpv-source.h"
+
+extern bool wgl_have_NV_DX_interop;
+extern HANDLE wgl_dx_device;
+
+static inline void wgl_lock_shared_texture(void* context)
+{
+    struct mpv_source* src = context;
+    wglDXLockObjectsNV(wgl_dx_device, 1, &src->gl_shared_texture_handle);
+}
+
+static inline void wgl_unlock_shared_texture(void* context)
+{
+    struct mpv_source* src = context;
+    wglDXUnlockObjectsNV(wgl_dx_device, 1, &src->gl_shared_texture_handle);
+}
+
+#else
+#    define wgl_have_NV_DX_interop 0
+
+static inline void wgl_lock_shared_texture(void* context)
+{
+    UNUSED_PARAMETER(context);
+}
+
+static inline void wgl_unlock_shared_texture(void* context)
+{
+    UNUSED_PARAMETER(context);
+}
+#endif
+
 bool wgl_init();
 
 void wgl_deinit();
 
 bool wgl_enter_context();
 
-void wgl_exit_context();
+void wgl_exit_context();
+
+void wgl_init_shared_gl_texture(void* context);
+
+void wgl_free_shared_gl_texture(void* context);
+