Add sender controlled playout delay limits

webrtc/modules/rtp_rtcp/source/rtp_header_extension.h

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
index beaf989c895830eb3dacc6ecd6bd22ff70d48445..f7df4bbe4caf5d9536236145416f122c1a3e7346 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
@@ -26,6 +26,14 @@ const size_t kAudioLevelLength = 2;
 const size_t kAbsoluteSendTimeLength = 4;
 const size_t kVideoRotationLength = 2;
 const size_t kTransportSequenceNumberLength = 3;
+const size_t kPlayoutDelayLength = 4;
+
+// Playout delay in milliseconds. A playout delay limit (min or max)
+// has 12 bits allocated. This allows a range of 0-4095 values which translates
+// to a range of 0-40950 in milliseconds.
+const int kPlayoutDelayGranularityMs = 10;
+// Maximum playout delay value in milliseconds.
+const int kPlayoutDelayMaxMs = 40950;
 
 struct HeaderExtension {
   explicit HeaderExtension(RTPExtensionType extension_type)
@@ -58,6 +66,9 @@ struct HeaderExtension {
       case kRtpExtensionTransportSequenceNumber:
         length = kTransportSequenceNumberLength;
         break;
+      case kRtpExtensionPlayoutDelay:
+        length = kPlayoutDelayLength;
+        break;
       default:
         assert(false);
     }
@@ -79,10 +90,9 @@ class RtpHeaderExtensionMap {
 
   int32_t Register(const RTPExtensionType type, const uint8_t id);
 
-  // Active is a concept for a registered rtp header extension which doesn't
-  // take effect yet until being activated. Inactive RTP header extensions do
-  // not take effect and should not be included in size calculations until they
-  // are activated.
+  // Active on an extension indicates whether it is currently being added on
+  // on the RTP packets. The active/inactive status on an extension can change
+  // dynamically depending on the need to convey new information.
   int32_t RegisterInactive(const RTPExtensionType type, const uint8_t id);
   bool SetActive(const RTPExtensionType type, bool active);