Implement adaptive target delay extension

media/cast/net/rtp/rtp_packetizer.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/cast/net/rtp/rtp_packetizer.h"
 
 #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.
       sequence_number(0),
       ssrc(0) {}
 
 RtpPacketizerConfig::~RtpPacketizerConfig() {}
 
 RtpPacketizer::RtpPacketizer(PacedSender* const transport,
                              PacketStorage* packet_storage,
@@ skipping 10 matching lines @@
 }
 
 RtpPacketizer::~RtpPacketizer() {}
 
 uint16 RtpPacketizer::NextSequenceNumber() {
   ++sequence_number_;
   return sequence_number_ - 1;
 }
 
 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;
 
   // Split the payload evenly (round number up).
   size_t num_packets = (frame.data.size() + max_length) / max_length;
   size_t payload_length = (frame.data.size() + num_packets) / num_packets;
   DCHECK_LE(payload_length, max_length) << "Invalid argument";
 
   SendPacketVector packets;
 
   size_t remaining_size = frame.data.size();
   std::string::const_iterator data_iter = frame.data.begin();
   while (remaining_size > 0) {
     PacketRef packet(new base::RefCountedData<Packet>);
 
     if (remaining_size < payload_length) {
       payload_length = remaining_size;
     }
     remaining_size -= payload_length;
     BuildCommonRTPheader(
         &packet->data, remaining_size == 0, frame.rtp_timestamp);
 
     // 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 num_extensions = 0;
+    if (frame.new_playout_delay_ms)
+      num_extensions++;
+    uint8 byte0 = kCastReferenceFrameIdBitMask;
+    if (frame.dependency == EncodedFrame::KEY)
+      byte0 |= kCastKeyFrameBitMask;
+    DCHECK_LE(num_extensions, kCastExtensionCountmask);
+    byte0 |= num_extensions;
+    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);
     base::BigEndianWriter big_endian_writer(
         reinterpret_cast<char*>(&(packet->data[start_size])), 4);
     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);

[Tom Sepez, 2014/08/21 22:41:03]

nit: do you want to explicitly mask this rather than just letting it get
truncated in push_back()?

+    }
 
     // Copy payload data.
     packet->data.insert(packet->data.end(),
                         data_iter,
                         data_iter + payload_length);
     data_iter += payload_length;
 
     const PacketKey key =
         PacedPacketSender::MakePacketKey(frame.reference_time,
                                          config_.ssrc,
@@ skipping 26 matching lines @@
   base::BigEndianWriter big_endian_writer(
       reinterpret_cast<char*>(&((*packet)[start_size])), 10);
   big_endian_writer.WriteU16(sequence_number_);
   big_endian_writer.WriteU32(time_stamp);
   big_endian_writer.WriteU32(config_.ssrc);
   ++sequence_number_;
 }
 
 }  // namespace cast
 }  // namespace media