diff --git a/api/frame_transformer_interface.h b/api/frame_transformer_interface.h
index 5efd3ea051..fba09d5ff0 100644
--- a/api/frame_transformer_interface.h
+++ b/api/frame_transformer_interface.h
@@ -62,6 +62,9 @@ class TransformableVideoFrameInterface : public TransformableFrameInterface {
   virtual std::vector<uint8_t> GetAdditionalData() const = 0;
 
   virtual const VideoFrameMetadata& GetMetadata() const = 0;
+  // TODO(https://crbug.com/webrtc/14709): Make pure virtual when Chromium MOCK
+  // has implemented this.
+  virtual void SetMetadata(const VideoFrameMetadata&) {}
 };
 
 // Extends the TransformableFrameInterface to expose audio-specific information.
diff --git a/api/test/mock_transformable_video_frame.h b/api/test/mock_transformable_video_frame.h
index 5cebcaba80..18b3de534e 100644
--- a/api/test/mock_transformable_video_frame.h
+++ b/api/test/mock_transformable_video_frame.h
@@ -31,6 +31,10 @@ class MockTransformableVideoFrame
               GetMetadata,
               (),
               (const, override));
+  MOCK_METHOD(void,
+              SetMetadata,
+              (const webrtc::VideoFrameMetadata&),
+              (override));
 };
 
 }  // namespace webrtc
diff --git a/modules/rtp_rtcp/source/frame_transformer_factory_unittest.cc b/modules/rtp_rtcp/source/frame_transformer_factory_unittest.cc
index e011a76ed5..65a0e4cbb4 100644
--- a/modules/rtp_rtcp/source/frame_transformer_factory_unittest.cc
+++ b/modules/rtp_rtcp/source/frame_transformer_factory_unittest.cc
@@ -48,6 +48,10 @@ class MockTransformableVideoFrame
               GetMetadata,
               (),
               (const, override));
+  MOCK_METHOD(void,
+              SetMetadata,
+              (const webrtc::VideoFrameMetadata&),
+              (override));
 };
 
 TEST(FrameTransformerFactory, CloneVideoFrame) {
diff --git a/modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.cc b/modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.cc
index 02194391af..27b6a17a20 100644
--- a/modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.cc
+++ b/modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.cc
@@ -69,6 +69,12 @@ class TransformableVideoSenderFrame : public TransformableVideoFrameInterface {
   }
 
   const VideoFrameMetadata& GetMetadata() const override { return metadata_; }
+  void SetMetadata(const VideoFrameMetadata& metadata) override {
+    header_.SetFromMetadata(metadata);
+    // We have to keep a local copy because GetMetadata() has to return a
+    // reference.
+    metadata_ = header_.GetAsMetadata();
+  }
 
   const RTPVideoHeader& GetHeader() const { return header_; }
   uint8_t GetPayloadType() const override { return payload_type_; }
@@ -83,8 +89,12 @@ class TransformableVideoSenderFrame : public TransformableVideoFrameInterface {
 
  private:
   rtc::scoped_refptr<EncodedImageBufferInterface> encoded_data_;
-  const RTPVideoHeader header_;
-  const VideoFrameMetadata metadata_;
+  RTPVideoHeader header_;
+  // This is a copy of `header_.GetAsMetadata()`, only needed because the
+  // interface says GetMetadata() must return a const ref rather than a value.
+  // TODO(crbug.com/webrtc/14709): Change the interface and delete this variable
+  // to reduce risk of it getting out-of-sync with `header_.GetAsMetadata()`.
+  VideoFrameMetadata metadata_;
   const VideoFrameType frame_type_;
   const uint8_t payload_type_;
   const absl::optional<VideoCodecType> codec_type_ = absl::nullopt;
diff --git a/video/rtp_video_stream_receiver_frame_transformer_delegate.cc b/video/rtp_video_stream_receiver_frame_transformer_delegate.cc
index 16015beee5..b1907fa7a2 100644
--- a/video/rtp_video_stream_receiver_frame_transformer_delegate.cc
+++ b/video/rtp_video_stream_receiver_frame_transformer_delegate.cc
@@ -15,6 +15,7 @@
 
 #include "absl/memory/memory.h"
 #include "modules/rtp_rtcp/source/rtp_descriptor_authentication.h"
+#include "rtc_base/checks.h"
 #include "rtc_base/thread.h"
 
 namespace webrtc {
@@ -53,6 +54,10 @@ class TransformableVideoReceiverFrame
   }
 
   const VideoFrameMetadata& GetMetadata() const override { return metadata_; }
+  void SetMetadata(const VideoFrameMetadata&) override {
+    RTC_DCHECK_NOTREACHED()
+        << "TransformableVideoReceiverFrame::SetMetadata is not implemented";
+  }
 
   std::unique_ptr<RtpFrameObject> ExtractFrame() && {
     return std::move(frame_);