[feat] use original resolution ratio when upgrade/downgrade source frame

src/media/resolution_adapter/resolution_adapter.cpp

@@ -15,8 +15,22 @@ int ResolutionAdapter::GetResolution(int target_bitrate, int current_width,
   for (auto& resolution : GetBitrateLimits()) {
     if (target_bitrate >= resolution.min_start_bitrate_bps &&
         target_bitrate < resolution.max_bitrate_bps) {
+      // Adjust the resolution to maintain the same aspect ratio as the current
+      // resolution
+      float aspect_ratio = static_cast<float>(current_width) / current_height;
+      if (static_cast<float>(resolution.width) / resolution.height !=
+          aspect_ratio) {
+        if (aspect_ratio > 1.0f) {
+          *target_width = resolution.width;
+          *target_height = static_cast<int>(resolution.width / aspect_ratio);
+        } else {
+          *target_height = resolution.height;
+          *target_width = static_cast<int>(resolution.height * aspect_ratio);
+        }
+      } else {
         *target_width = resolution.width;
         *target_height = resolution.height;
+      }
       return 0;
     }
   }

src/media/video/encode/aom/aom_av1_encoder.h

@@ -46,6 +46,10 @@ class AomAv1Encoder : public VideoEncoder {
   int SetTargetBitrate(int bitrate);
 
   int GetResolution(int* width, int* height) {
+    if (seq_ == 0) {
+      return -1;
+    }
+
     *width = frame_width_;
     *height = frame_height_;
     return 0;

src/media/video/encode/nvcodec/nvidia_video_encoder.h

@@ -23,6 +23,10 @@ class NvidiaVideoEncoder : public VideoEncoder {
   int SetTargetBitrate(int bitrate);
 
   int GetResolution(int* width, int* height) {
+    if (seq_ == 0) {
+      return -1;
+    }
+
     *width = frame_width_;
     *height = frame_height_;
     return 0;

src/media/video/encode/openh264/openh264_encoder.h

@@ -33,6 +33,10 @@ class OpenH264Encoder : public VideoEncoder {
   int SetTargetBitrate(int bitrate);
 
   int GetResolution(int* width, int* height) {
+    if (seq_ == 0) {
+      return -1;
+    }
+
     *width = frame_width_;
     *height = frame_height_;
     return 0;

src/transport/ice_transport_controller.cpp

@@ -600,7 +600,11 @@ void IceTransportController::PostUpdates(webrtc::NetworkControlUpdate update) {
     if (target_bitrate != target_bitrate_ && video_encoder_) {
       target_bitrate_ = target_bitrate;
       int width, height, target_width, target_height;
-      video_encoder_->GetResolution(&width, &height);
+      int valid = video_encoder_->GetResolution(&width, &height);
+      if (valid != 0) {
+        width = source_width_;
+        height = source_height_;
+      }
       if (0 == resolution_adapter_->GetResolution(target_bitrate_, width,
                                                   height, &target_width,
                                                   &target_height)) {