UI: reduce frame drops. (#26266)

* reduce frame dropping

* This mode will not draw the same frame twice

* cleanup comment

* use previous texture if update is not triggered by vipc thread and without new frame

selfdrive/ui/qt/widgets/cameraview.cc

@@ -240,24 +240,13 @@ void CameraWidget::paintGL() {
   glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
 
   std::lock_guard lk(frame_lock);
-  if (frames.empty()) return;
 
-  int frame_idx = frames.size() - 1;
-
-  // Always draw latest frame until sync logic is more stable
-  // for (frame_idx = 0; frame_idx < frames.size() - 1; frame_idx++) {
-  //   if (frames[frame_idx].first == draw_frame_id) break;
-  // }
-
-  // Log duplicate/dropped frames
-  if (frames[frame_idx].first == prev_frame_id) {
-    qDebug() << "Drawing same frame twice" << frames[frame_idx].first;
-  } else if (frames[frame_idx].first != prev_frame_id + 1) {
-    qDebug() << "Skipped frame" << frames[frame_idx].first;
+  // use previous texture if update() is called without new frame.
+  VisionBuf *frame = nullptr;
+  if (!frames.empty()) {
+    frame = frames.front().second;
+    frames.pop_front();
   }
-  prev_frame_id = frames[frame_idx].first;
-  VisionBuf *frame = frames[frame_idx].second;
-  assert(frame != nullptr);
 
   glViewport(0, 0, width(), height());
   glBindVertexArray(frame_vao);
@@ -266,19 +255,21 @@ void CameraWidget::paintGL() {
 
 #ifdef QCOM2
   glActiveTexture(GL_TEXTURE0);
+  if (frame) {
     glEGLImageTargetTexture2DOES(GL_TEXTURE_EXTERNAL_OES, egl_images[frame->idx]);
     assert(glGetError() == GL_NO_ERROR);
+  }
 #else
   glPixelStorei(GL_UNPACK_ROW_LENGTH, stream_stride);
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, textures[0]);
-  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, stream_width, stream_height, GL_RED, GL_UNSIGNED_BYTE, frame->y);
+  if (frame) glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, stream_width, stream_height, GL_RED, GL_UNSIGNED_BYTE, frame->y);
   assert(glGetError() == GL_NO_ERROR);
 
   glPixelStorei(GL_UNPACK_ROW_LENGTH, stream_stride/2);
   glActiveTexture(GL_TEXTURE0 + 1);
   glBindTexture(GL_TEXTURE_2D, textures[1]);
-  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, stream_width/2, stream_height/2, GL_RG, GL_UNSIGNED_BYTE, frame->uv);
+  if (frame) glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, stream_width/2, stream_height/2, GL_RG, GL_UNSIGNED_BYTE, frame->uv);
   assert(glGetError() == GL_NO_ERROR);
 #endif
 
@@ -375,6 +366,7 @@ void CameraWidget::vipcThread() {
         std::lock_guard lk(frame_lock);
         frames.push_back(std::make_pair(meta_main.frame_id, buf));
         while (frames.size() > FRAME_BUFFER_SIZE) {
+          qDebug() << "Skipped frame" << frames.front().first;
           frames.pop_front();
         }
       }

selfdrive/ui/qt/widgets/cameraview.h

@@ -81,7 +81,6 @@ protected:
   std::mutex frame_lock;
   std::deque<std::pair<uint32_t, VisionBuf*>> frames;
   uint32_t draw_frame_id = 0;
-  uint32_t prev_frame_id = 0;
 
 protected slots:
   void vipcConnected(VisionIpcClient *vipc_client);