Expose video mimeType for insertable streams

which allows determining what codec (data format) is used.
Chromium CL:
  https://chromium-review.googlesource.com/c/chromium/src/+/4941907

Split from
  https://webrtc-review.googlesource.com/c/src/+/318283
to reduce CL size and avoid audio woes.

BUG=webrtc:15579

Change-Id: I404107af526df3009c16d2a6148784fe87dfa807
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/323721
Reviewed-by: Tony Herre <herre@google.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#41007}

api/frame_transformer_interface.h

@@ -12,6 +12,7 @@
 #define API_FRAME_TRANSFORMER_INTERFACE_H_
 
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "api/scoped_refptr.h"
@@ -53,6 +54,11 @@ class TransformableFrameInterface {
   // sender frames to allow received frames to be directly re-transmitted on
   // other PeerConnectionss.
   virtual Direction GetDirection() const { return Direction::kUnknown; }
+  virtual std::string GetMimeType() const {
+    // TODO(bugs.webrtc.org/15579): Change this to pure virtual after it
+    // is implemented everywhere.
+    return "unknown/unknown";
+  }
 };
 
 class TransformableVideoFrameInterface : public TransformableFrameInterface {

api/test/mock_transformable_video_frame.h

@@ -11,6 +11,7 @@
 #ifndef API_TEST_MOCK_TRANSFORMABLE_VIDEO_FRAME_H_
 #define API_TEST_MOCK_TRANSFORMABLE_VIDEO_FRAME_H_
 
+#include <string>
 #include <vector>
 
 #include "api/frame_transformer_interface.h"
@@ -36,6 +37,7 @@ class MockTransformableVideoFrame
               GetDirection,
               (),
               (const, override));
+  MOCK_METHOD(std::string, GetMimeType, (), (const, override));
   MOCK_METHOD(VideoFrameMetadata, Metadata, (), (const, override));
   MOCK_METHOD(absl::optional<Timestamp>,
               GetCaptureTimeIdentifier,

modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.cc

@@ -10,6 +10,7 @@
 
 #include "modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate.h"
 
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -97,6 +98,13 @@ class TransformableVideoSenderFrame : public TransformableVideoFrameInterface {
   }
 
   Direction GetDirection() const override { return Direction::kSender; }
+  std::string GetMimeType() const override {
+    if (!codec_type_.has_value()) {
+      return "video/x-unknown";
+    }
+    std::string mime_type = "video/";
+    return mime_type + CodecTypeToPayloadString(*codec_type_);
+  }
 
  private:
   rtc::scoped_refptr<EncodedImageBufferInterface> encoded_data_;

modules/rtp_rtcp/source/rtp_sender_video_frame_transformer_delegate_unittest.cc

@@ -74,9 +74,15 @@ class RtpSenderVideoFrameTransformerDelegateTest : public ::testing::Test {
                           frame_to_transform) {
           frame = std::move(frame_to_transform);
         });
+    RTPVideoHeader rtp_header;
+
+    VideoFrameMetadata metadata;
+    metadata.SetCodec(VideoCodecType::kVideoCodecVP8);
+    metadata.SetRTPVideoHeaderCodecSpecifics(RTPVideoHeaderVP8());
+
     delegate->TransformFrame(
         /*payload_type=*/1, VideoCodecType::kVideoCodecVP8, /*rtp_timestamp=*/2,
-        encoded_image, RTPVideoHeader(),
+        encoded_image, RTPVideoHeader::FromMetadata(metadata),
         /*expected_retransmission_time=*/TimeDelta::PlusInfinity());
     return frame;
   }
@@ -135,6 +141,7 @@ TEST_F(RtpSenderVideoFrameTransformerDelegateTest,
   std::unique_ptr<TransformableFrameInterface> frame =
       GetTransformableFrame(delegate);
   ASSERT_TRUE(frame);
+  EXPECT_STRCASEEQ("video/VP8", frame->GetMimeType().c_str());
 
   rtc::Event event;
   EXPECT_CALL(test_sender_, SendVideo).WillOnce(WithoutArgs([&] {
@@ -162,6 +169,7 @@ TEST_F(RtpSenderVideoFrameTransformerDelegateTest, CloneSenderVideoFrame) {
 
   EXPECT_EQ(clone->IsKeyFrame(), video_frame.IsKeyFrame());
   EXPECT_EQ(clone->GetPayloadType(), video_frame.GetPayloadType());
+  EXPECT_EQ(clone->GetMimeType(), video_frame.GetMimeType());
   EXPECT_EQ(clone->GetSsrc(), video_frame.GetSsrc());
   EXPECT_EQ(clone->GetTimestamp(), video_frame.GetTimestamp());
   EXPECT_EQ(clone->Metadata(), video_frame.Metadata());
@@ -182,6 +190,7 @@ TEST_F(RtpSenderVideoFrameTransformerDelegateTest, CloneKeyFrame) {
 
   EXPECT_EQ(clone->IsKeyFrame(), video_frame.IsKeyFrame());
   EXPECT_EQ(clone->GetPayloadType(), video_frame.GetPayloadType());
+  EXPECT_EQ(clone->GetMimeType(), video_frame.GetMimeType());
   EXPECT_EQ(clone->GetSsrc(), video_frame.GetSsrc());
   EXPECT_EQ(clone->GetTimestamp(), video_frame.GetTimestamp());
   EXPECT_EQ(clone->Metadata(), video_frame.Metadata());

modules/rtp_rtcp/source/rtp_video_stream_receiver_frame_transformer_delegate.cc

@@ -10,6 +10,7 @@
 
 #include "modules/rtp_rtcp/source/rtp_video_stream_receiver_frame_transformer_delegate.h"
 
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -75,6 +76,10 @@ class TransformableVideoReceiverFrame
   }
 
   Direction GetDirection() const override { return Direction::kReceiver; }
+  std::string GetMimeType() const override {
+    std::string mime_type = "video/";
+    return mime_type + CodecTypeToPayloadString(frame_->codec_type());
+  }
 
   const RtpVideoFrameReceiver* Receiver() { return receiver_; }
 

modules/rtp_rtcp/source/rtp_video_stream_receiver_frame_transformer_delegate_unittest.cc

@@ -138,6 +138,7 @@ TEST(RtpVideoStreamReceiverFrameTransformerDelegateTest,
   ON_CALL(*mock_frame_transformer, Transform)
       .WillByDefault(
           [&callback](std::unique_ptr<TransformableFrameInterface> frame) {
+            EXPECT_STRCASEEQ("video/Generic", frame->GetMimeType().c_str());
             callback->OnTransformedFrame(std::move(frame));
           });
   delegate->TransformFrame(CreateRtpFrameObject(RTPVideoHeader(), csrcs));

test/mock_transformable_frame.h

@@ -33,6 +33,7 @@ class MockTransformableAudioFrame : public TransformableAudioFrameInterface {
   MOCK_METHOD(uint32_t, GetTimestamp, (), (const, override));
   MOCK_METHOD(void, SetRTPTimestamp, (uint32_t), (override));
   MOCK_METHOD(Direction, GetDirection, (), (const, override));
+  MOCK_METHOD(std::string, GetMimeType, (), (const, override));
 };
 
 }  // namespace webrtc