Fix list of resiliency mechanisms in setCodecPreferences

Add ulpfec and flexfec to list of resiliency mechanisms taken
into account and in general exclude Comfort Noise (CN) from media
codecs.

Also introduce RtpCodecCapability::IsMediaCodec & ::IsResiliencyCodec
behaving like the MediaCodec methods.

BUG=webrtc:15396

Change-Id: I79041898928190bfdd33a06d8f6975d7556c46b1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/330424
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41485}

api/BUILD.gn

@@ -508,6 +508,7 @@ rtc_library("rtp_parameters") {
     ":array_view",
     ":priority",
     ":rtp_transceiver_direction",
+    "../media:media_constants",
     "../rtc_base:checks",
     "../rtc_base:stringutils",
     "../rtc_base/system:rtc_export",

api/rtp_parameters.cc

@@ -15,6 +15,7 @@
 #include <utility>
 
 #include "api/array_view.h"
+#include "media/base/media_constants.h"
 #include "rtc_base/strings/string_builder.h"
 
 namespace webrtc {
@@ -47,6 +48,14 @@ RtcpFeedback::~RtcpFeedback() = default;
 RtpCodec::RtpCodec() = default;
 RtpCodec::RtpCodec(const RtpCodec&) = default;
 RtpCodec::~RtpCodec() = default;
+bool RtpCodec::IsResiliencyCodec() const {
+  return name == cricket::kRtxCodecName || name == cricket::kRedCodecName ||
+         name == cricket::kUlpfecCodecName ||
+         name == cricket::kFlexfecCodecName;
+}
+bool RtpCodec::IsMediaCodec() const {
+  return !IsResiliencyCodec() && name != cricket::kComfortNoiseCodecName;
+}
 RtpCodecCapability::RtpCodecCapability() = default;
 RtpCodecCapability::~RtpCodecCapability() = default;
 

api/rtp_parameters.h

@@ -167,6 +167,8 @@ struct RTC_EXPORT RtpCodec {
            parameters == o.parameters;
   }
   bool operator!=(const RtpCodec& o) const { return !(*this == o); }
+  bool IsResiliencyCodec() const;
+  bool IsMediaCodec() const;
 };
 
 // RtpCodecCapability is to RtpCodecParameters as RtpCapabilities is to

media/base/codec.cc

@@ -311,7 +311,8 @@ webrtc::RtpCodecParameters Codec::ToCodecParameters() const {
 }
 
 bool Codec::IsMediaCodec() const {
-  return !IsResiliencyCodec();
+  return !IsResiliencyCodec() &&
+         !absl::EqualsIgnoreCase(name, kComfortNoiseCodecName);
 }
 
 bool Codec::IsResiliencyCodec() const {

pc/peer_connection_encodings_integrationtest.cc

@@ -74,15 +74,6 @@ struct StringParamToString {
   }
 };
 
-// RTX, RED and FEC are reliability mechanisms used in combinations with other
-// codecs, but are not themselves a specific codec. Typically you don't want to
-// filter these out of the list of codec preferences.
-bool IsReliabilityMechanism(const RtpCodecCapability& codec) {
-  return absl::EqualsIgnoreCase(codec.name, cricket::kRtxCodecName) ||
-         absl::EqualsIgnoreCase(codec.name, cricket::kRedCodecName) ||
-         absl::EqualsIgnoreCase(codec.name, cricket::kUlpfecCodecName);
-}
-
 std::string GetCurrentCodecMimeType(
     rtc::scoped_refptr<const RTCStatsReport> report,
     const RTCOutboundRtpStreamStats& outbound_rtp) {
@@ -163,7 +154,7 @@ class PeerConnectionEncodingsIntegrationTest : public ::testing::Test {
             .codecs;
     codecs.erase(std::remove_if(codecs.begin(), codecs.end(),
                                 [&codec_name](const RtpCodecCapability& codec) {
-                                  return !IsReliabilityMechanism(codec) &&
+                                  return !codec.IsResiliencyCodec() &&
                                          !absl::EqualsIgnoreCase(codec.name,
                                                                  codec_name);
                                 }),

pc/rtp_transceiver.cc

@@ -51,9 +51,7 @@ RTCError VerifyCodecPreferences(
   // transceiver.direction.
 
   if (!absl::c_any_of(codecs, [&recv_codecs](const RtpCodecCapability& codec) {
-        return codec.name != cricket::kRtxCodecName &&
-               codec.name != cricket::kRedCodecName &&
-               codec.name != cricket::kFlexfecCodecName &&
+        return codec.IsMediaCodec() &&
                absl::c_any_of(recv_codecs,
                               [&codec](const cricket::Codec& recv_codec) {
                                 return recv_codec.MatchesRtpCodec(codec);
@@ -65,9 +63,7 @@ RTCError VerifyCodecPreferences(
   }
 
   if (!absl::c_any_of(codecs, [&send_codecs](const RtpCodecCapability& codec) {
-        return codec.name != cricket::kRtxCodecName &&
-               codec.name != cricket::kRedCodecName &&
-               codec.name != cricket::kFlexfecCodecName &&
+        return codec.IsMediaCodec() &&
                absl::c_any_of(send_codecs,
                               [&codec](const cricket::Codec& send_codec) {
                                 return send_codec.MatchesRtpCodec(codec);
@@ -101,11 +97,9 @@ RTCError VerifyCodecPreferences(
     }
   }
 
-  // Check we have a real codec (not just rtx, red or fec)
+  // Check we have a real codec (not just rtx, red, fec or CN)
   if (absl::c_all_of(codecs, [](const RtpCodecCapability& codec) {
-        return codec.name == cricket::kRtxCodecName ||
-               codec.name == cricket::kRedCodecName ||
-               codec.name == cricket::kUlpfecCodecName;
+        return !codec.IsMediaCodec();
       })) {
     LOG_AND_RETURN_ERROR(
         RTCErrorType::INVALID_MODIFICATION,