diff --git a/media/engine/webrtc_voice_engine.cc b/media/engine/webrtc_voice_engine.cc
index 95f4d39..0cf17ed 100644
--- a/media/engine/webrtc_voice_engine.cc
+++ b/media/engine/webrtc_voice_engine.cc
@@ -775,9 +775,7 @@
       out.push_back(codec);
 
       if (codec.name == kOpusCodecName && audio_red_for_opus_enabled_) {
-        std::string redFmtp =
-            rtc::ToString(codec.id) + "/" + rtc::ToString(codec.id);
-        map_format({kRedCodecName, 48000, 2, {{"", redFmtp}}}, &out);
+        map_format({kRedCodecName, 48000, 2}, &out);
       }
     }
   }
@@ -1656,37 +1654,6 @@
   return true;
 }
 
-// Utility function to check if RED codec and its parameters match a codec spec.
-bool CheckRedParameters(
-    const AudioCodec& red_codec,
-    const webrtc::AudioSendStream::Config::SendCodecSpec& send_codec_spec) {
-  if (red_codec.clockrate != send_codec_spec.format.clockrate_hz ||
-      red_codec.channels != send_codec_spec.format.num_channels) {
-    return false;
-  }
-
-  // Check the FMTP line for the empty parameter which should match
-  // <primary codec>/<primary codec>[/...]
-  auto red_parameters = red_codec.params.find("");
-  if (red_parameters == red_codec.params.end()) {
-    RTC_LOG(LS_WARNING) << "audio/RED missing fmtp parameters.";
-    return false;
-  }
-  std::vector<std::string> redundant_payloads;
-  rtc::split(red_parameters->second, '/', &redundant_payloads);
-  // 32 is chosen as a maximum upper bound for consistency with the
-  // red payload splitter.
-  if (redundant_payloads.size() < 2 || redundant_payloads.size() > 32) {
-    return false;
-  }
-  for (auto pt : redundant_payloads) {
-    if (pt != rtc::ToString(send_codec_spec.payload_type)) {
-      return false;
-    }
-  }
-  return true;
-}
-
 // Utility function called from SetSendParameters() to extract current send
 // codec settings from the given list of codecs (originally from SDP). Both send
 // and receive streams may be reconfigured based on the new settings.
@@ -1797,7 +1764,8 @@
     for (const AudioCodec& red_codec : codecs) {
       if (red_codec_position < send_codec_position &&
           IsCodec(red_codec, kRedCodecName) &&
-          CheckRedParameters(red_codec, *send_codec_spec)) {
+          red_codec.clockrate == send_codec_spec->format.clockrate_hz &&
+          red_codec.channels == send_codec_spec->format.num_channels) {
         send_codec_spec->red_payload_type = red_codec.id;
         break;
       }
diff --git a/media/engine/webrtc_voice_engine_unittest.cc b/media/engine/webrtc_voice_engine_unittest.cc
index 9f031ed..4b127af 100644
--- a/media/engine/webrtc_voice_engine_unittest.cc
+++ b/media/engine/webrtc_voice_engine_unittest.cc
@@ -1028,12 +1028,10 @@
   cricket::AudioRecvParameters parameters;
   parameters.codecs.push_back(kOpusCodec);
   parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs[1].params[""] = "111/111";
   EXPECT_TRUE(channel_->SetRecvParameters(parameters));
   EXPECT_THAT(GetRecvStreamConfig(kSsrcX).decoder_map,
               (ContainerEq<std::map<int, webrtc::SdpAudioFormat>>(
-                  {{111, {"opus", 48000, 2}},
-                   {112, {"red", 48000, 2, {{"", "111/111"}}}}})));
+                  {{111, {"opus", 48000, 2}}, {112, {"red", 48000, 2}}})));
 }
 
 // Test that we disable Opus/Red with the kill switch.
@@ -1497,13 +1495,15 @@
   EXPECT_FALSE(channel_->CanInsertDtmf());
 }
 
-// Test that we use Opus/Red by default when it is
-// listed as the first codec and there is an fmtp line.
+// Test that we use Opus/Red under the field trial when it is
+// listed as the first codec.
 TEST_P(WebRtcVoiceEngineTestFake, SetSendCodecsRed) {
+  webrtc::test::ScopedFieldTrials override_field_trials(
+      "WebRTC-Audio-Red-For-Opus/Enabled/");
+
   EXPECT_TRUE(SetupSendStream());
   cricket::AudioSendParameters parameters;
   parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs[0].params[""] = "111/111";
   parameters.codecs.push_back(kOpusCodec);
   SetSendParameters(parameters);
   const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
@@ -1512,41 +1512,15 @@
   EXPECT_EQ(112, send_codec_spec.red_payload_type);
 }
 
-// Test that we do not use Opus/Red by default when it is
-// listed as the first codec but there is no fmtp line.
-TEST_P(WebRtcVoiceEngineTestFake, SetSendCodecsRedNoFmtp) {
-  EXPECT_TRUE(SetupSendStream());
-  cricket::AudioSendParameters parameters;
-  parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs.push_back(kOpusCodec);
-  SetSendParameters(parameters);
-  const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
-  EXPECT_EQ(111, send_codec_spec.payload_type);
-  EXPECT_STRCASEEQ("opus", send_codec_spec.format.name.c_str());
-  EXPECT_EQ(absl::nullopt, send_codec_spec.red_payload_type);
-}
-
-// Test that we do not use Opus/Red by default.
+// Test that we do not use Opus/Red under the field trial by default.
 TEST_P(WebRtcVoiceEngineTestFake, SetSendCodecsRedDefault) {
-  EXPECT_TRUE(SetupSendStream());
-  cricket::AudioSendParameters parameters;
-  parameters.codecs.push_back(kOpusCodec);
-  parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs[1].params[""] = "111/111";
-  SetSendParameters(parameters);
-  const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
-  EXPECT_EQ(111, send_codec_spec.payload_type);
-  EXPECT_STRCASEEQ("opus", send_codec_spec.format.name.c_str());
-  EXPECT_EQ(absl::nullopt, send_codec_spec.red_payload_type);
-}
+  webrtc::test::ScopedFieldTrials override_field_trials(
+      "WebRTC-Audio-Red-For-Opus/Enabled/");
 
-// Test that the RED fmtp line must match the payload type.
-TEST_P(WebRtcVoiceEngineTestFake, SetSendCodecsRedFmtpMismatch) {
   EXPECT_TRUE(SetupSendStream());
   cricket::AudioSendParameters parameters;
-  parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs[0].params[""] = "8/8";
   parameters.codecs.push_back(kOpusCodec);
+  parameters.codecs.push_back(kRed48000Codec);
   SetSendParameters(parameters);
   const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
   EXPECT_EQ(111, send_codec_spec.payload_type);
@@ -1554,34 +1528,6 @@
   EXPECT_EQ(absl::nullopt, send_codec_spec.red_payload_type);
 }
 
-// Test that the RED fmtp line must show 2..32 payloads.
-TEST_P(WebRtcVoiceEngineTestFake, SetSendCodecsRedFmtpAmountOfRedundancy) {
-  EXPECT_TRUE(SetupSendStream());
-  cricket::AudioSendParameters parameters;
-  parameters.codecs.push_back(kRed48000Codec);
-  parameters.codecs[0].params[""] = "111";
-  parameters.codecs.push_back(kOpusCodec);
-  SetSendParameters(parameters);
-  const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
-  EXPECT_EQ(111, send_codec_spec.payload_type);
-  EXPECT_STRCASEEQ("opus", send_codec_spec.format.name.c_str());
-  EXPECT_EQ(absl::nullopt, send_codec_spec.red_payload_type);
-  for (int i = 1; i < 32; i++) {
-    parameters.codecs[0].params[""] += "/111";
-    SetSendParameters(parameters);
-    const auto& send_codec_spec = *GetSendStreamConfig(kSsrcX).send_codec_spec;
-    EXPECT_EQ(111, send_codec_spec.payload_type);
-    EXPECT_STRCASEEQ("opus", send_codec_spec.format.name.c_str());
-    EXPECT_EQ(112, send_codec_spec.red_payload_type);
-  }
-  parameters.codecs[0].params[""] += "/111";
-  SetSendParameters(parameters);
-  const auto& send_codec_spec2 = *GetSendStreamConfig(kSsrcX).send_codec_spec;
-  EXPECT_EQ(111, send_codec_spec2.payload_type);
-  EXPECT_STRCASEEQ("opus", send_codec_spec2.format.name.c_str());
-  EXPECT_EQ(absl::nullopt, send_codec_spec2.red_payload_type);
-}
-
 // Test that WebRtcVoiceEngine reconfigures, rather than recreates its
 // AudioSendStream.
 TEST_P(WebRtcVoiceEngineTestFake, DontRecreateSendStream) {