src/media/cast/net/rtp/rtp_packetizer.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/cast/net/rtp/rtp_packetizer.h"
   6
   7 #include "base/big_endian.h"
   8 #include "base/logging.h"
   9 #include "media/cast/net/pacing/paced_sender.h"
  10 #include "media/cast/net/rtp/rtp_defines.h"
  11
  12 namespace media {
  13 namespace cast {
  14
  15 RtpPacketizerConfig::RtpPacketizerConfig()
  16     : payload_type(-1),
  17       max_payload_length(kMaxIpPacketSize - 28),  // Default is IP-v4/UDP.
  18       sequence_number(0),
  19       ssrc(0) {}
  20
  21 RtpPacketizerConfig::~RtpPacketizerConfig() {}
  22
  23 RtpPacketizer::RtpPacketizer(PacedSender* const transport,
  24                              PacketStorage* packet_storage,
  25                              RtpPacketizerConfig rtp_packetizer_config)
  26     : config_(rtp_packetizer_config),
  27       transport_(transport),
  28       packet_storage_(packet_storage),
  29       sequence_number_(config_.sequence_number),
  30       rtp_timestamp_(0),
  31       packet_id_(0),
  32       send_packet_count_(0),
  33       send_octet_count_(0) {
  34   DCHECK(transport) << "Invalid argument";
  35 }
  36
  37 RtpPacketizer::~RtpPacketizer() {}
  38
  39 uint16 RtpPacketizer::NextSequenceNumber() {
  40   ++sequence_number_;
  41   return sequence_number_ - 1;
  42 }
  43
  44 void RtpPacketizer::SendFrameAsPackets(const EncodedFrame& frame) {
  45   uint16 rtp_header_length = kRtpHeaderLength + kCastHeaderLength;
  46   uint16 max_length = config_.max_payload_length - rtp_header_length - 1;
  47   rtp_timestamp_ = frame.rtp_timestamp;
  48
  49   // Split the payload evenly (round number up).
  50   size_t num_packets = (frame.data.size() + max_length) / max_length;
  51   size_t payload_length = (frame.data.size() + num_packets) / num_packets;
  52   DCHECK_LE(payload_length, max_length) << "Invalid argument";
  53
  54   SendPacketVector packets;
  55
  56   size_t remaining_size = frame.data.size();
  57   std::string::const_iterator data_iter = frame.data.begin();
  58   while (remaining_size > 0) {
  59     PacketRef packet(new base::RefCountedData<Packet>);
  60
  61     if (remaining_size < payload_length) {
  62       payload_length = remaining_size;
  63     }
  64     remaining_size -= payload_length;
  65     BuildCommonRTPheader(
  66         &packet->data, remaining_size == 0, frame.rtp_timestamp);
  67
  68     // Build Cast header.
  69     // TODO(miu): Should we always set the ref frame bit and the ref_frame_id?
  70     DCHECK_NE(frame.dependency, EncodedFrame::UNKNOWN_DEPENDENCY);
  71     uint8 num_extensions = 0;
  72     if (frame.new_playout_delay_ms)
  73       num_extensions++;
  74     uint8 byte0 = kCastReferenceFrameIdBitMask;
  75     if (frame.dependency == EncodedFrame::KEY)
  76       byte0 |= kCastKeyFrameBitMask;
  77     DCHECK_LE(num_extensions, kCastExtensionCountmask);
  78     byte0 |= num_extensions;
  79     packet->data.push_back(byte0);
  80     packet->data.push_back(static_cast<uint8>(frame.frame_id));
  81     size_t start_size = packet->data.size();
  82     packet->data.resize(start_size + 4);
  83     base::BigEndianWriter big_endian_writer(
  84         reinterpret_cast<char*>(&(packet->data[start_size])), 4);
  85     big_endian_writer.WriteU16(packet_id_);
  86     big_endian_writer.WriteU16(static_cast<uint16>(num_packets - 1));
  87     packet->data.push_back(static_cast<uint8>(frame.referenced_frame_id));
  88     if (frame.new_playout_delay_ms) {
  89       packet->data.push_back(kCastRtpExtensionAdaptiveLatency << 2);
  90       packet->data.push_back(2);  // 2 bytes
  91       packet->data.push_back(
  92           static_cast<uint8>(frame.new_playout_delay_ms >> 8));
  93       packet->data.push_back(
  94           static_cast<uint8>(frame.new_playout_delay_ms));
  95     }
  96
  97     // Copy payload data.
  98     packet->data.insert(packet->data.end(),
  99                         data_iter,
 100                         data_iter + payload_length);
 101     data_iter += payload_length;
 102
 103     const PacketKey key =
 104         PacedPacketSender::MakePacketKey(frame.reference_time,
 105                                          config_.ssrc,
 106                                          packet_id_++);
 107     packets.push_back(make_pair(key, packet));
 108
 109     // Update stats.
 110     ++send_packet_count_;
 111     send_octet_count_ += payload_length;
 112   }
 113   DCHECK(packet_id_ == num_packets) << "Invalid state";
 114
 115   packet_storage_->StoreFrame(frame.frame_id, packets);
 116
 117   // Send to network.
 118   transport_->SendPackets(packets);
 119
 120   // Prepare for next frame.
 121   packet_id_ = 0;
 122 }
 123
 124 void RtpPacketizer::BuildCommonRTPheader(Packet* packet,
 125                                          bool marker_bit,
 126                                          uint32 time_stamp) {
 127   packet->push_back(0x80);
 128   packet->push_back(static_cast<uint8>(config_.payload_type) |
 129                     (marker_bit ? kRtpMarkerBitMask : 0));
 130   size_t start_size = packet->size();
 131   packet->resize(start_size + 10);
 132   base::BigEndianWriter big_endian_writer(
 133       reinterpret_cast<char*>(&((*packet)[start_size])), 10);
 134   big_endian_writer.WriteU16(sequence_number_);
 135   big_endian_writer.WriteU32(time_stamp);
 136   big_endian_writer.WriteU32(config_.ssrc);
 137   ++sequence_number_;
 138 }
 139
 140 }  // namespace cast
 141 }  // namespace media