Use GL_NEAREST when possible without degrading quality

Author: cgutman

app/streaming/video/ffmpeg-renderers/eglvid.cpp

@@ -627,8 +627,6 @@ bool EGLRenderer::setupVideoRenderingState() {
     glGenTextures(EGL_MAX_PLANES, m_Textures);
     for (size_t i = 0; i < EGL_MAX_PLANES; ++i) {
         glBindTexture(GL_TEXTURE_EXTERNAL_OES, m_Textures[i]);
-        glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-        glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
         glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     }
@@ -682,8 +680,8 @@ bool EGLRenderer::setupOverlayRenderingState() {
     for (size_t i = 0; i < Overlay::OverlayMax; ++i) {
         // Set up the overlay texture
         glBindTexture(GL_TEXTURE_2D, m_OverlayTextures[i]);
-        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
@@ -786,13 +784,33 @@ void EGLRenderer::renderFrame(AVFrame* frame)
         }
     }
 
+    int drawableWidth, drawableHeight;
+    SDL_GL_GetDrawableSize(m_Window, &drawableWidth, &drawableHeight);
+    SDL_Rect src, dst;
+    src.x = src.y = dst.x = dst.y = 0;
+    src.w = frame->width;
+    src.h = frame->height;
+    dst.w = drawableWidth;
+    dst.h = drawableHeight;
+    StreamUtils::scaleSourceToDestinationSurface(&src, &dst);
+
     ssize_t plane_count = m_Backend->exportEGLImages(frame, m_EGLDisplay, imgs);
     if (plane_count < 0)
         return;
     for (ssize_t i = 0; i < plane_count; ++i) {
         glActiveTexture(GL_TEXTURE0 + i);
         glBindTexture(GL_TEXTURE_EXTERNAL_OES, m_Textures[i]);
         m_glEGLImageTargetTexture2DOES(GL_TEXTURE_EXTERNAL_OES, imgs[i]);
+
+        // Use GL_NEAREST to reduce sampling if the video region is a multiple of the frame size
+        if (dst.w % frame->width == 0 && dst.h % frame->height == 0) {
+            glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+            glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+        }
+        else {
+            glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+            glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        }
     }
 
     // We already called glClear() after last frame's SDL_GL_SwapWindow()
@@ -801,17 +819,7 @@ void EGLRenderer::renderFrame(AVFrame* frame)
         glClear(GL_COLOR_BUFFER_BIT);
     }
 
-    int drawableWidth, drawableHeight;
-    SDL_GL_GetDrawableSize(m_Window, &drawableWidth, &drawableHeight);
-
     // Set the viewport to the size of the aspect-ratio-scaled video
-    SDL_Rect src, dst;
-    src.x = src.y = dst.x = dst.y = 0;
-    src.w = frame->width;
-    src.h = frame->height;
-    dst.w = drawableWidth;
-    dst.h = drawableHeight;
-    StreamUtils::scaleSourceToDestinationSurface(&src, &dst);
     glViewport(dst.x, dst.y, dst.w, dst.h);
 
     glUseProgram(m_ShaderProgram);

app/streaming/video/ffmpeg-renderers/sdlvid.cpp

@@ -417,6 +417,9 @@ void SdlRenderer::renderFrame(AVFrame* frame)
             goto Exit;
         }
 
+        // Never alpha blend this texture when rendering
+        SDL_SetTextureBlendMode(m_Texture, SDL_BLENDMODE_NONE);
+
 #ifdef HAVE_CUDA
         if (frame->format == AV_PIX_FMT_CUDA) {
             SDL_assert(m_CudaGLHelper == nullptr);
@@ -567,6 +570,11 @@ void SdlRenderer::renderFrame(AVFrame* frame)
     // Ensure the viewport is set to the desired video region
     SDL_RenderSetViewport(m_Renderer, &dst);
 
+    // Use nearest pixel sampling if the video region size is a multiple of the frame size
+    SDL_SetTextureScaleMode(m_Texture,
+                            dst.w % frame->width == 0 && dst.h % frame->height == 0 ?
+                                SDL_ScaleModeNearest : SDL_ScaleModeLinear);
+
     // Draw the video content itself
     SDL_RenderCopy(m_Renderer, m_Texture, nullptr, nullptr);