Add codec comparison function to SdpVideoFormat

SdpVideoFormat is used to configure video encoder and decoders.
This CL adds support for comparing two SdpVideoFormat objects
to determine if they specify the same video codec.

This functionality previously only existed in media/base/codec.h
which made the code sensitive to circular dependencies. Once
downstream projects stop using cricket::IsSameCodec, this code
can be removed.

Bug: chromium:1187565
Change-Id: I242069aa6af07917637384c80ee4820887defc7d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/213427
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33794}

api/video_codecs/sdp_video_format.cc

@@ -10,10 +10,57 @@
 
 #include "api/video_codecs/sdp_video_format.h"
 
+#include "absl/strings/match.h"
+#include "api/video_codecs/h264_profile_level_id.h"
+#include "api/video_codecs/video_codec.h"
+#include "api/video_codecs/vp9_profile.h"
+#include "rtc_base/checks.h"
 #include "rtc_base/strings/string_builder.h"
 
 namespace webrtc {
 
+namespace {
+
+std::string H264GetPacketizationModeOrDefault(
+    const SdpVideoFormat::Parameters& params) {
+  constexpr char kH264FmtpPacketizationMode[] = "packetization-mode";
+  const auto it = params.find(kH264FmtpPacketizationMode);
+  if (it != params.end()) {
+    return it->second;
+  }
+  // If packetization-mode is not present, default to "0".
+  // https://tools.ietf.org/html/rfc6184#section-6.2
+  return "0";
+}
+
+bool H264IsSamePacketizationMode(const SdpVideoFormat::Parameters& left,
+                                 const SdpVideoFormat::Parameters& right) {
+  return H264GetPacketizationModeOrDefault(left) ==
+         H264GetPacketizationModeOrDefault(right);
+}
+
+// Some (video) codecs are actually families of codecs and rely on parameters
+// to distinguish different incompatible family members.
+bool IsSameCodecSpecific(const SdpVideoFormat& format1,
+                         const SdpVideoFormat& format2) {
+  // The assumption when calling this function is that the two formats have the
+  // same name.
+  RTC_DCHECK(absl::EqualsIgnoreCase(format1.name, format2.name));
+
+  VideoCodecType codec_type = PayloadStringToCodecType(format1.name);
+  switch (codec_type) {
+    case kVideoCodecH264:
+      return H264IsSameProfile(format1.parameters, format2.parameters) &&
+             H264IsSamePacketizationMode(format1.parameters,
+                                         format2.parameters);
+    case kVideoCodecVP9:
+      return VP9IsSameProfile(format1.parameters, format2.parameters);
+    default:
+      return true;
+  }
+}
+}  // namespace
+
 SdpVideoFormat::SdpVideoFormat(const std::string& name) : name(name) {}
 
 SdpVideoFormat::SdpVideoFormat(const std::string& name,
@@ -37,6 +84,23 @@ std::string SdpVideoFormat::ToString() const {
   return builder.str();
 }
 
+bool SdpVideoFormat::IsSameCodec(const SdpVideoFormat& other) const {
+  // Two codecs are considered the same if the name matches (case insensitive)
+  // and certain codec-specific parameters match.
+  return absl::EqualsIgnoreCase(name, other.name) &&
+         IsSameCodecSpecific(*this, other);
+}
+
+bool SdpVideoFormat::IsCodecInList(
+    rtc::ArrayView<const webrtc::SdpVideoFormat> formats) const {
+  for (const auto& format : formats) {
+    if (IsSameCodec(format)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 bool operator==(const SdpVideoFormat& a, const SdpVideoFormat& b) {
   return a.name == b.name && a.parameters == b.parameters;
 }