Declare Plan B DEPRECATED

Bug: webrtc:11121
Change-Id: Id9b933a71a9bfd1d20ddd137f43459cdc8ed1896
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/238780
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35504}

api/peer_connection_interface.h

@@ -168,7 +168,11 @@ class StatsObserver : public rtc::RefCountInterface {
   ~StatsObserver() override = default;
 };
 
-enum class SdpSemantics { kPlanB, kUnifiedPlan };
+enum class SdpSemantics {
+  kPlanB_DEPRECATED,
+  kPlanB [[deprecated]] = kPlanB_DEPRECATED,
+  kUnifiedPlan
+};
 
 class RTC_EXPORT PeerConnectionInterface : public rtc::RefCountInterface {
  public:
@@ -622,24 +626,23 @@ class RTC_EXPORT PeerConnectionInterface : public rtc::RefCountInterface {
     // WebRTC 1.0 specification requires kUnifiedPlan semantics. The
     // RtpTransceiver API is only available with kUnifiedPlan semantics.
     //
-    // kPlanB will cause PeerConnection to create offers and answers with at
-    // most one audio and one video m= section with multiple RtpSenders and
-    // RtpReceivers specified as multiple a=ssrc lines within the section. This
-    // will also cause PeerConnection to ignore all but the first m= section of
-    // the same media type.
-    //
     // kUnifiedPlan will cause PeerConnection to create offers and answers with
     // multiple m= sections where each m= section maps to one RtpSender and one
     // RtpReceiver (an RtpTransceiver), either both audio or both video. This
     // will also cause PeerConnection to ignore all but the first a=ssrc lines
     // that form a Plan B stream.
     //
-    // For users who wish to send multiple audio/video streams and need to stay
+    // kPlanB will cause PeerConnection to create offers and answers with at
-    // interoperable with legacy WebRTC implementations or use legacy APIs,
+    // most one audio and one video m= section with multiple RtpSenders and
-    // specify kPlanB.
+    // RtpReceivers specified as multiple a=ssrc lines within the section. This
+    // will also cause PeerConnection to ignore all but the first m= section of
+    // the same media type.
+    //
+    // For users who have to interwork with legacy WebRTC implementations,
+    // it is possible to specify kPlanB until the code is finally removed.
     //
     // For all other users, specify kUnifiedPlan.
-    SdpSemantics sdp_semantics = SdpSemantics::kPlanB;
+    SdpSemantics sdp_semantics = SdpSemantics::kPlanB_DEPRECATED;
 
     // TODO(bugs.webrtc.org/9891) - Move to crypto_options or remove.
     // Actively reset the SRTP parameters whenever the DTLS transports

pc/peer_connection.cc

@@ -2540,7 +2540,7 @@ void PeerConnection::ReportSdpBundleUsage(
     } else {
       usage = kBundleUsageEmpty;
     }
-  } else if (configuration_.sdp_semantics == SdpSemantics::kPlanB) {
+  } else if (configuration_.sdp_semantics == SdpSemantics::kPlanB_DEPRECATED) {
     // In plan-b, simple/complex usage will not show up in the number of
     // m-lines or BUNDLE.
     usage = using_bundle ? kBundleUsageBundlePlanB : kBundleUsageNoBundlePlanB;

sdk/android/src/jni/pc/peer_connection.cc

@@ -112,13 +112,13 @@ SdpSemantics JavaToNativeSdpSemantics(JNIEnv* jni,
   std::string enum_name = GetJavaEnumName(jni, j_sdp_semantics);
 
   if (enum_name == "PLAN_B")
-    return SdpSemantics::kPlanB;
+    return SdpSemantics::kPlanB_DEPRECATED;
 
   if (enum_name == "UNIFIED_PLAN")
     return SdpSemantics::kUnifiedPlan;
 
   RTC_DCHECK_NOTREACHED();
-  return SdpSemantics::kPlanB;
+  return SdpSemantics::kPlanB_DEPRECATED;
 }
 
 ScopedJavaLocalRef<jobject> NativeToJavaCandidatePairChange(

sdk/objc/api/peerconnection/RTCConfiguration.mm

@@ -520,7 +520,7 @@
 + (webrtc::SdpSemantics)nativeSdpSemanticsForSdpSemantics:(RTCSdpSemantics)sdpSemantics {
   switch (sdpSemantics) {
     case RTCSdpSemanticsPlanB:
-      return webrtc::SdpSemantics::kPlanB;
+      return webrtc::SdpSemantics::kPlanB_DEPRECATED;
     case RTCSdpSemanticsUnifiedPlan:
       return webrtc::SdpSemantics::kUnifiedPlan;
   }
@@ -528,7 +528,7 @@
 
 + (RTCSdpSemantics)sdpSemanticsForNativeSdpSemantics:(webrtc::SdpSemantics)sdpSemantics {
   switch (sdpSemantics) {
-    case webrtc::SdpSemantics::kPlanB:
+    case webrtc::SdpSemantics::kPlanB_DEPRECATED:
       return RTCSdpSemanticsPlanB;
     case webrtc::SdpSemantics::kUnifiedPlan:
       return RTCSdpSemanticsUnifiedPlan;