media/cast/net/rtp/rtp_packet_builder.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_packet_builder.h"
   6
   7 #include "base/big_endian.h"
   8 #include "base/logging.h"
   9
  10 namespace media {
  11 namespace cast {
  12
  13 const uint32 kCastRtpHeaderLength = 7;
  14 const uint32 kGenericRtpHeaderLength = 12;
  15 static const uint8 kRtpMarkerBitMask = 0x80;
  16
  17 RtpPacketBuilder::RtpPacketBuilder()
  18     : is_key_(false),
  19       frame_id_(0),
  20       packet_id_(0),
  21       max_packet_id_(0),
  22       reference_frame_id_(0),
  23       timestamp_(0),
  24       sequence_number_(0),
  25       marker_(false),
  26       payload_type_(0),
  27       ssrc_(0) {}
  28
  29 void RtpPacketBuilder::SetKeyFrame(bool is_key) { is_key_ = is_key; }
  30
  31 void RtpPacketBuilder::SetFrameIds(uint32 frame_id, uint32 reference_frame_id) {
  32   frame_id_ = frame_id;
  33   reference_frame_id_ = reference_frame_id;
  34 }
  35
  36 void RtpPacketBuilder::SetPacketId(uint16 packet_id) { packet_id_ = packet_id; }
  37
  38 void RtpPacketBuilder::SetMaxPacketId(uint16 max_packet_id) {
  39   max_packet_id_ = max_packet_id;
  40 }
  41
  42 void RtpPacketBuilder::SetTimestamp(uint32 timestamp) {
  43   timestamp_ = timestamp;
  44 }
  45
  46 void RtpPacketBuilder::SetSequenceNumber(uint16 sequence_number) {
  47   sequence_number_ = sequence_number;
  48 }
  49
  50 void RtpPacketBuilder::SetMarkerBit(bool marker) { marker_ = marker; }
  51
  52 void RtpPacketBuilder::SetPayloadType(int payload_type) {
  53   payload_type_ = payload_type;
  54 }
  55
  56 void RtpPacketBuilder::SetSsrc(uint32 ssrc) { ssrc_ = ssrc; }
  57
  58 void RtpPacketBuilder::BuildHeader(uint8* data, uint32 data_length) {
  59   BuildCommonHeader(data, data_length);
  60   BuildCastHeader(data + kGenericRtpHeaderLength,
  61                   data_length - kGenericRtpHeaderLength);
  62 }
  63
  64 void RtpPacketBuilder::BuildCastHeader(uint8* data, uint32 data_length) {
  65   // Build header.
  66   DCHECK_LE(kCastRtpHeaderLength, data_length);
  67   // Set the first 7 bytes to 0.
  68   memset(data, 0, kCastRtpHeaderLength);
  69   base::BigEndianWriter big_endian_writer(reinterpret_cast<char*>(data), 56);
  70   const bool includes_specific_frame_reference =
  71       (is_key_ && (reference_frame_id_ != frame_id_)) ||
  72       (!is_key_ && (reference_frame_id_ != (frame_id_ - 1)));
  73   big_endian_writer.WriteU8((is_key_ ? 0x80 : 0) |
  74                             (includes_specific_frame_reference ? 0x40 : 0));
  75   big_endian_writer.WriteU8(frame_id_);
  76   big_endian_writer.WriteU16(packet_id_);
  77   big_endian_writer.WriteU16(max_packet_id_);
  78   if (includes_specific_frame_reference) {
  79     big_endian_writer.WriteU8(reference_frame_id_);
  80   }
  81 }
  82
  83 void RtpPacketBuilder::BuildCommonHeader(uint8* data, uint32 data_length) {
  84   DCHECK_LE(kGenericRtpHeaderLength, data_length);
  85   base::BigEndianWriter big_endian_writer(reinterpret_cast<char*>(data), 96);
  86   big_endian_writer.WriteU8(0x80);
  87   big_endian_writer.WriteU8(payload_type_ | (marker_ ? kRtpMarkerBitMask : 0));
  88   big_endian_writer.WriteU16(sequence_number_);
  89   big_endian_writer.WriteU32(timestamp_);
  90   big_endian_writer.WriteU32(ssrc_);
  91 }
  92
  93 }  // namespace cast
  94 }  // namespace media