Implement adaptive target delay extension

media/cast/net/rtp/rtp_packetizer.cc

Index: media/cast/net/rtp/rtp_packetizer.cc
diff --git a/media/cast/net/rtp/rtp_packetizer.cc b/media/cast/net/rtp/rtp_packetizer.cc
index dcfcc8bba45e4d4b4478e537116f4057791cfe66..3c282fcfc2dace8e38b7af89c7b4cd9119b280ab 100644
--- a/media/cast/net/rtp/rtp_packetizer.cc
+++ b/media/cast/net/rtp/rtp_packetizer.cc
@@ -7,16 +7,11 @@
 #include "base/big_endian.h"
 #include "base/logging.h"
 #include "media/cast/net/pacing/paced_sender.h"
+#include "media/cast/net/rtp/rtp_defines.h"
 
 namespace media {
 namespace cast {
 
-static const uint16 kCommonRtpHeaderLength = 12;
-static const uint16 kCastRtpHeaderLength = 7;
-static const uint8 kCastKeyFrameBitMask = 0x80;
-static const uint8 kCastReferenceFrameIdBitMask = 0x40;
-static const uint8 kRtpMarkerBitMask = 0x80;
-
 RtpPacketizerConfig::RtpPacketizerConfig()
     : payload_type(-1),
       max_payload_length(kMaxIpPacketSize - 28),  // Default is IP-v4/UDP.
@@ -47,7 +42,7 @@ uint16 RtpPacketizer::NextSequenceNumber() {
 }
 
 void RtpPacketizer::SendFrameAsPackets(const EncodedFrame& frame) {
-  uint16 rtp_header_length = kCommonRtpHeaderLength + kCastRtpHeaderLength;
+  uint16 rtp_header_length = kRtpHeaderLength + kCastHeaderLength;
   uint16 max_length = config_.max_payload_length - rtp_header_length - 1;
   rtp_timestamp_ = frame.rtp_timestamp;
 
@@ -73,9 +68,14 @@ void RtpPacketizer::SendFrameAsPackets(const EncodedFrame& frame) {
     // Build Cast header.
     // TODO(miu): Should we always set the ref frame bit and the ref_frame_id?
     DCHECK_NE(frame.dependency, EncodedFrame::UNKNOWN_DEPENDENCY);
-    packet->data.push_back(
-        ((frame.dependency == EncodedFrame::KEY) ? kCastKeyFrameBitMask : 0) |
-             kCastReferenceFrameIdBitMask);
+    uint8 byte0 = kCastReferenceFrameIdBitMask;
+    if (frame.dependency == EncodedFrame::KEY)
+      byte0 |= kCastKeyFrameBitMask;
+    if (frame.new_playout_delay_ms) {
+      // One extension block.
+      byte0 |= 1;

[Alpha Left Google, 2014/08/20 20:17:06]

I suggest having an additional counter for the number of extensions and then OR
later. It'll be more readable than hardcoding 1 and easy to add new extensions
later.

[hubbe, 2014/08/20 21:42:02]

Total overkill, but ok.

+    }
+    packet->data.push_back(byte0);
     packet->data.push_back(static_cast<uint8>(frame.frame_id));
     size_t start_size = packet->data.size();
     packet->data.resize(start_size + 4);
@@ -84,6 +84,12 @@ void RtpPacketizer::SendFrameAsPackets(const EncodedFrame& frame) {
     big_endian_writer.WriteU16(packet_id_);
     big_endian_writer.WriteU16(static_cast<uint16>(num_packets - 1));
     packet->data.push_back(static_cast<uint8>(frame.referenced_frame_id));
+    if (frame.new_playout_delay_ms) {
+      packet->data.push_back(kCastRTPExtensionAdaptiveLatency << 2);
+      packet->data.push_back(2);  // 2 bytes
+      packet->data.push_back(frame.new_playout_delay_ms >> 8);
+      packet->data.push_back(frame.new_playout_delay_ms);
+    }
 
     // Copy payload data.
     packet->data.insert(packet->data.end(),