Introduce InbandComfortNoise RTP header extension.

BUG: webrtc:11085
Change-Id: I9b556a0d67d3c239abc247787103af9e50af4e65
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159710
Commit-Queue: Minyue Li <minyue@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30014}

modules/rtp_rtcp/include/rtp_rtcp_defines.h

@@ -55,6 +55,7 @@ enum RTPExtensionType : int {
   kRtpExtensionNone,
   kRtpExtensionTransmissionTimeOffset,
   kRtpExtensionAudioLevel,
+  kRtpExtensionInbandComfortNoise,
   kRtpExtensionAbsoluteSendTime,
   kRtpExtensionAbsoluteCaptureTime,
   kRtpExtensionVideoRotation,

modules/rtp_rtcp/source/rtp_header_extension_map.cc

@@ -49,6 +49,7 @@ constexpr ExtensionInfo kExtensions[] = {
     CreateExtensionInfo<RtpGenericFrameDescriptorExtension01>(),
     CreateExtensionInfo<RtpDependencyDescriptorExtension>(),
     CreateExtensionInfo<ColorSpaceExtension>(),
+    CreateExtensionInfo<InbandComfortNoiseExtension>(),
 };
 
 // Because of kRtpExtensionNone, NumberOfExtension is 1 bigger than the actual

modules/rtp_rtcp/source/rtp_header_extensions.cc

@@ -855,4 +855,49 @@ constexpr const char RepairedRtpStreamId::kUri[];
 constexpr RTPExtensionType RtpMid::kId;
 constexpr const char RtpMid::kUri[];
 
+// An RTP Header Extension for Inband Comfort Noise
+//
+// The form of the audio level extension block:
+//
+//  0                   1
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |  ID   | len=0 |N| level       |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// Sample Audio Level Encoding Using the One-Byte Header Format
+//
+//  0                   1                   2
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |      ID       |     len=1     |N|    level    |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// Sample Audio Level Encoding Using the Two-Byte Header Format
+
+constexpr RTPExtensionType InbandComfortNoiseExtension::kId;
+constexpr uint8_t InbandComfortNoiseExtension::kValueSizeBytes;
+constexpr const char InbandComfortNoiseExtension::kUri[];
+
+bool InbandComfortNoiseExtension::Parse(rtc::ArrayView<const uint8_t> data,
+                                        absl::optional<uint8_t>* level) {
+  if (data.size() != kValueSizeBytes)
+    return false;
+  *level = (data[0] & 0b1000'0000) != 0
+               ? absl::nullopt
+               : absl::make_optional(data[0] & 0b0111'1111);
+  return true;
+}
+
+bool InbandComfortNoiseExtension::Write(rtc::ArrayView<uint8_t> data,
+                                        absl::optional<uint8_t> level) {
+  RTC_DCHECK_EQ(data.size(), kValueSizeBytes);
+  data[0] = 0b0000'0000;
+  if (level) {
+    if (*level > 127) {
+      return false;
+    }
+    data[0] = 0b1000'0000 | *level;
+  }
+  return true;
+}
+
 }  // namespace webrtc

modules/rtp_rtcp/source/rtp_header_extensions.h

@@ -297,5 +297,23 @@ class RtpMid : public BaseRtpStringExtension {
   static constexpr const char kUri[] = "urn:ietf:params:rtp-hdrext:sdes:mid";
 };
 
+class InbandComfortNoiseExtension {
+ public:
+  using value_type = absl::optional<uint8_t>;
+
+  static constexpr RTPExtensionType kId = kRtpExtensionInbandComfortNoise;
+  static constexpr uint8_t kValueSizeBytes = 1;
+  static constexpr const char kUri[] =
+      "http://www.webrtc.org/experiments/rtp-hdrext/inband-cn";
+
+  static bool Parse(rtc::ArrayView<const uint8_t> data,
+                    absl::optional<uint8_t>* level);
+  static size_t ValueSize(absl::optional<uint8_t> level) {
+    return kValueSizeBytes;
+  }
+  static bool Write(rtc::ArrayView<uint8_t> data,
+                    absl::optional<uint8_t> level);
+};
+
 }  // namespace webrtc
 #endif  // MODULES_RTP_RTCP_SOURCE_RTP_HEADER_EXTENSIONS_H_

modules/rtp_rtcp/source/rtp_packet.cc

@@ -193,7 +193,8 @@ void RtpPacket::ZeroMutableExtensions() {
       case RTPExtensionType::kRtpExtensionRepairedRtpStreamId:
       case RTPExtensionType::kRtpExtensionRtpStreamId:
       case RTPExtensionType::kRtpExtensionVideoContentType:
-      case RTPExtensionType::kRtpExtensionVideoRotation: {
+      case RTPExtensionType::kRtpExtensionVideoRotation:
+      case RTPExtensionType::kRtpExtensionInbandComfortNoise: {
         // Non-mutable extension. Don't change it.
         break;
       }

modules/rtp_rtcp/source/rtp_utility.cc

@@ -543,6 +543,10 @@ void RtpHeaderParser::ParseOneByteExtensionHeader(
           RTC_LOG(WARNING)
               << "RtpExtensionColorSpace unsupported by rtp header parser.";
           break;
+        case kRtpExtensionInbandComfortNoise:
+          RTC_LOG(WARNING) << "Inband comfort noise extension unsupported by "
+                              "rtp header parser.";
+          break;
         case kRtpExtensionNone:
         case kRtpExtensionNumberOfExtensions: {
           RTC_NOTREACHED() << "Invalid extension type: " << type;

test/fuzzers/rtp_packet_fuzzer.cc

@@ -145,6 +145,11 @@ void FuzzOneInput(const uint8_t* data, size_t size) {
         packet.GetExtension<ColorSpaceExtension>(&color_space);
         break;
       }
+      case kRtpExtensionInbandComfortNoise: {
+        absl::optional<uint8_t> noise_level;
+        packet.GetExtension<InbandComfortNoiseExtension>(&noise_level);
+        break;
+      }
       case kRtpExtensionGenericFrameDescriptor02:
         // This extension requires state to read and so complicated that
         // deserves own fuzzer.