diff --git a/media/base/video_adapter.cc b/media/base/video_adapter.cc
index 27b82646ac..8ba91d7189 100644
--- a/media/base/video_adapter.cc
+++ b/media/base/video_adapter.cc
@@ -145,8 +145,6 @@ VideoAdapter::VideoAdapter() : VideoAdapter(1) {}
 VideoAdapter::~VideoAdapter() {}
 
 bool VideoAdapter::KeepFrame(int64_t in_timestamp_ns) {
-  rtc::CritScope cs(&critical_section_);
-
   int max_fps = max_framerate_request_;
   if (max_fps_)
     max_fps = std::min(max_fps, *max_fps_);
diff --git a/media/base/video_adapter.h b/media/base/video_adapter.h
index 65c2d42267..b7acf0e67c 100644
--- a/media/base/video_adapter.h
+++ b/media/base/video_adapter.h
@@ -46,7 +46,8 @@ class VideoAdapter {
                             int* cropped_width,
                             int* cropped_height,
                             int* out_width,
-                            int* out_height);
+                            int* out_height)
+      RTC_LOCKS_EXCLUDED(critical_section_);
 
   // DEPRECATED. Please use OnOutputFormatRequest below.
   // TODO(asapersson): Remove this once it is no longer used.
@@ -57,7 +58,8 @@ class VideoAdapter {
   // maintain the input orientation, so it doesn't matter if e.g. 1280x720 or
   // 720x1280 is requested.
   // Note: Should be called from the source only.
-  void OnOutputFormatRequest(const absl::optional<VideoFormat>& format);
+  void OnOutputFormatRequest(const absl::optional<VideoFormat>& format)
+      RTC_LOCKS_EXCLUDED(critical_section_);
 
   // Requests output frame size and frame interval from |AdaptFrameResolution|.
   // |target_aspect_ratio|: The input frame size will be cropped to match the
@@ -70,7 +72,7 @@ class VideoAdapter {
   void OnOutputFormatRequest(
       const absl::optional<std::pair<int, int>>& target_aspect_ratio,
       const absl::optional<int>& max_pixel_count,
-      const absl::optional<int>& max_fps);
+      const absl::optional<int>& max_fps) RTC_LOCKS_EXCLUDED(critical_section_);
 
   // Same as above, but allows setting two different target aspect ratios
   // depending on incoming frame orientation. This gives more fine-grained
@@ -81,7 +83,7 @@ class VideoAdapter {
       const absl::optional<int>& max_landscape_pixel_count,
       const absl::optional<std::pair<int, int>>& target_portrait_aspect_ratio,
       const absl::optional<int>& max_portrait_pixel_count,
-      const absl::optional<int>& max_fps);
+      const absl::optional<int>& max_fps) RTC_LOCKS_EXCLUDED(critical_section_);
 
   // Requests the output frame size from |AdaptFrameResolution| to have as close
   // as possible to |sink_wants.target_pixel_count| pixels (if set)
@@ -93,11 +95,13 @@ class VideoAdapter {
   // The sink resolution alignment requirement is given by
   // |sink_wants.resolution_alignment|.
   // Note: Should be called from the sink only.
-  void OnSinkWants(const rtc::VideoSinkWants& sink_wants);
+  void OnSinkWants(const rtc::VideoSinkWants& sink_wants)
+      RTC_LOCKS_EXCLUDED(critical_section_);
 
  private:
   // Determine if frame should be dropped based on input fps and requested fps.
-  bool KeepFrame(int64_t in_timestamp_ns);
+  bool KeepFrame(int64_t in_timestamp_ns)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(critical_section_);
 
   int frames_in_ RTC_GUARDED_BY(critical_section_);  // Number of input frames.
   int frames_out_