Filter overlapping RTP header extensions.

This removes unnecessary RTP header extension overhead since only one of
these extensions is used at a time.

BUG=webrtc:4254
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1429753003 .

Cr-Commit-Position: refs/heads/master@{#10455}

talk/media/webrtc/webrtcmediaengine.cc

@@ -68,4 +68,44 @@ MediaEngineInterface* WebRtcMediaEngineFactory::Create(
   return CreateWebRtcMediaEngine(adm, encoder_factory, decoder_factory);
 }
 
+const char* kBweExtensionPriorities[] = {
+    kRtpTransportSequenceNumberHeaderExtension,
+    kRtpAbsoluteSenderTimeHeaderExtension, kRtpTimestampOffsetHeaderExtension};
+
+const size_t kBweExtensionPrioritiesLength =
+    ARRAY_SIZE(kBweExtensionPriorities);
+
+int GetPriority(const RtpHeaderExtension& extension,
+                const char* extension_prios[],
+                size_t extension_prios_length) {
+  for (size_t i = 0; i < extension_prios_length; ++i) {
+    if (extension.uri == extension_prios[i])
+      return static_cast<int>(i);
+  }
+  return -1;
+}
+
+std::vector<RtpHeaderExtension> FilterRedundantRtpExtensions(
+    const std::vector<RtpHeaderExtension>& extensions,
+    const char* extension_prios[],
+    size_t extension_prios_length) {
+  if (extensions.empty())
+    return std::vector<RtpHeaderExtension>();
+  std::vector<RtpHeaderExtension> filtered;
+  std::map<int, const RtpHeaderExtension*> sorted;
+  for (auto& extension : extensions) {
+    int priority =
+        GetPriority(extension, extension_prios, extension_prios_length);
+    if (priority == -1) {
+      filtered.push_back(extension);
+      continue;
+    } else {
+      sorted[priority] = &extension;
+    }
+  }
+  if (!sorted.empty())
+    filtered.push_back(*sorted.begin()->second);
+  return filtered;
+}
+
 }  // namespace cricket

talk/media/webrtc/webrtcmediaengine.h

@@ -48,6 +48,14 @@ class WebRtcMediaEngineFactory {
       WebRtcVideoDecoderFactory* decoder_factory);
 };
 
+extern const char* kBweExtensionPriorities[];
+extern const size_t kBweExtensionPrioritiesLength;
+
+std::vector<RtpHeaderExtension> FilterRedundantRtpExtensions(
+    const std::vector<RtpHeaderExtension>& extensions,
+    const char* extension_prios[],
+    size_t extension_prios_length);
+
 }  // namespace cricket
 
 #endif  // TALK_MEDIA_WEBRTCMEDIAENGINE_H_

talk/media/webrtc/webrtcvideoengine2.cc

@@ -36,6 +36,7 @@
 #include "talk/media/base/videorenderer.h"
 #include "talk/media/webrtc/constants.h"
 #include "talk/media/webrtc/simulcast.h"
+#include "talk/media/webrtc/webrtcmediaengine.h"
 #include "talk/media/webrtc/webrtcvideoencoderfactory.h"
 #include "talk/media/webrtc/webrtcvideoframe.h"
 #include "talk/media/webrtc/webrtcvoiceengine.h"
@@ -1544,7 +1545,8 @@ bool WebRtcVideoChannel2::SetSendRtpHeaderExtensions(
     return false;
 
   std::vector<webrtc::RtpExtension> filtered_extensions =
-      FilterRtpExtensions(extensions);
+      FilterRtpExtensions(FilterRedundantRtpExtensions(
+          extensions, kBweExtensionPriorities, kBweExtensionPrioritiesLength));
   if (!RtpExtensionsHaveChanged(send_rtp_extensions_, filtered_extensions)) {
     LOG(LS_INFO) << "Ignoring call to SetSendRtpHeaderExtensions because "
                     "header extensions haven't changed.";

talk/media/webrtc/webrtcvideoengine2_unittest.cc

@@ -1066,6 +1066,29 @@ class WebRtcVideoChannel2Test : public WebRtcVideoEngine2Test {
     EXPECT_EQ(webrtc_ext, recv_stream->GetConfig().rtp.extensions[0].name);
   }
 
+  void TestExtensionFilter(const std::vector<std::string>& extensions,
+                           const std::string& expected_extension) {
+    cricket::VideoSendParameters parameters = send_parameters_;
+    int expected_id = -1;
+    int id = 1;
+    for (const std::string& extension : extensions) {
+      if (extension == expected_extension)
+        expected_id = id;
+      parameters.extensions.push_back(
+          cricket::RtpHeaderExtension(extension, id++));
+    }
+    EXPECT_TRUE(channel_->SetSendParameters(parameters));
+    FakeVideoSendStream* send_stream =
+        AddSendStream(cricket::StreamParams::CreateLegacy(123));
+
+    // Verify that only one of them has been set, and that it is the one with
+    // highest priority (transport sequence number).
+    ASSERT_EQ(1u, send_stream->GetConfig().rtp.extensions.size());
+    EXPECT_EQ(expected_id, send_stream->GetConfig().rtp.extensions[0].id);
+    EXPECT_EQ(expected_extension,
+              send_stream->GetConfig().rtp.extensions[0].name);
+  }
+
   void TestCpuAdaptation(bool enable_overuse, bool is_screenshare);
   void TestReceiverLocalSsrcConfiguration(bool receiver_first);
   void TestReceiveUnsignalledSsrcPacket(uint8_t payload_type,
@@ -1199,6 +1222,23 @@ TEST_F(WebRtcVideoChannel2Test, RecvAbsoluteSendTimeHeaderExtensions) {
                                  webrtc::RtpExtension::kAbsSendTime);
 }
 
+TEST_F(WebRtcVideoChannel2Test, FiltersExtensionsPicksTransportSeqNum) {
+  // Enable three redundant extensions.
+  std::vector<std::string> extensions;
+  extensions.push_back(kRtpAbsoluteSenderTimeHeaderExtension);
+  extensions.push_back(kRtpTimestampOffsetHeaderExtension);
+  extensions.push_back(kRtpTransportSequenceNumberHeaderExtension);
+  TestExtensionFilter(extensions, kRtpTransportSequenceNumberHeaderExtension);
+}
+
+TEST_F(WebRtcVideoChannel2Test, FiltersExtensionsPicksAbsSendTime) {
+  // Enable two redundant extensions.
+  std::vector<std::string> extensions;
+  extensions.push_back(kRtpAbsoluteSenderTimeHeaderExtension);
+  extensions.push_back(kRtpTimestampOffsetHeaderExtension);
+  TestExtensionFilter(extensions, kRtpAbsoluteSenderTimeHeaderExtension);
+}
+
 class WebRtcVideoChannel2WithSendSideBweTest : public WebRtcVideoChannel2Test {
  public:
   WebRtcVideoChannel2WithSendSideBweTest()
@@ -1230,13 +1270,10 @@ TEST_F(WebRtcVideoChannel2Test, RecvVideoRotationHeaderExtensions) {
 }
 
 TEST_F(WebRtcVideoChannel2Test, IdenticalSendExtensionsDoesntRecreateStream) {
-  const int kTOffsetId = 1;
-  const int kAbsSendTimeId = 2;
-  const int kVideoRotationId = 3;
+  const int kAbsSendTimeId = 1;
+  const int kVideoRotationId = 2;
   send_parameters_.extensions.push_back(cricket::RtpHeaderExtension(
       kRtpAbsoluteSenderTimeHeaderExtension, kAbsSendTimeId));
-  send_parameters_.extensions.push_back(cricket::RtpHeaderExtension(
-      kRtpTimestampOffsetHeaderExtension, kTOffsetId));
   send_parameters_.extensions.push_back(cricket::RtpHeaderExtension(
       kRtpVideoRotationHeaderExtension, kVideoRotationId));
 
@@ -1245,7 +1282,7 @@ TEST_F(WebRtcVideoChannel2Test, IdenticalSendExtensionsDoesntRecreateStream) {
       AddSendStream(cricket::StreamParams::CreateLegacy(123));
 
   EXPECT_EQ(1, fake_call_->GetNumCreatedSendStreams());
-  ASSERT_EQ(3u, send_stream->GetConfig().rtp.extensions.size());
+  ASSERT_EQ(2u, send_stream->GetConfig().rtp.extensions.size());
 
   // Setting the same extensions (even if in different order) shouldn't
   // reallocate the stream.