RTX包webrtc处理-白红宇

RTX包webrtc处理

阅读量：3559 次

发布时间：2019-05-20

本文共 2281 字，大约阅读时间需要 7 分钟。

0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         RTP Header                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |            OSN                |                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |   |                  Original RTP Packet Payload                  |   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

OSN：原rtp包seq number

webrtc代码实现，注释很详细

std::unique_ptr
   
     RTPSender::BuildRtxPacket(    const RtpPacketToSend& packet) {  // TODO(danilchap): Create rtx packet with extra capacity for SRTP  // when transport interface would be updated to take buffer class.  std::unique_ptr
    
      rtx_packet(new RtpPacketToSend(      &rtp_header_extension_map_, packet.size() + kRtxHeaderSize));  // Add original RTP header.  rtx_packet->CopyHeaderFrom(packet);  {    rtc::CritScope lock(&send_critsect_);    if (!sending_media_)      return nullptr;    RTC_DCHECK(ssrc_rtx_);    // Replace payload type.    auto kv = rtx_payload_type_map_.find(packet.PayloadType());    if (kv == rtx_payload_type_map_.end())      return nullptr;    rtx_packet->SetPayloadType(kv->second);    // Replace sequence number.    rtx_packet->SetSequenceNumber(sequence_number_rtx_++);    // Replace SSRC.    rtx_packet->SetSsrc(*ssrc_rtx_);    // Possibly include the MID header extension.    if (!mid_.empty()) {      // This is a no-op if the MID header extension is not registered.      rtx_packet->SetExtension
     
      (mid_);    }  }  uint8_t* rtx_payload =      rtx_packet->AllocatePayload(packet.payload_size() + kRtxHeaderSize);  RTC_DCHECK(rtx_payload);  // Add OSN (original sequence number).  ByteWriter
      
       ::WriteBigEndian(rtx_payload, packet.SequenceNumber());  // Add original payload data.  auto payload = packet.payload();  memcpy(rtx_payload + kRtxHeaderSize, payload.data(), payload.size());  // Add original application data.  rtx_packet->set_application_data(packet.application_data());  return rtx_packet;}