{"id":788,"date":"2022-08-16T09:59:55","date_gmt":"2022-08-16T01:59:55","guid":{"rendered":"https:\/\/www.fanyamin.com\/wordpress\/?p=788"},"modified":"2022-09-22T22:43:58","modified_gmt":"2022-09-22T14:43:58","slug":"webrtc-rtx","status":"publish","type":"post","link":"https:\/\/www.fanyamin.com\/wordpress\/?p=788","title":{"rendered":"WebRTC RTX"},"content":{"rendered":"

\u5728 WebRTC \u4e2d\u5e38\u7528\u7684 QoS \u7b56\u7565\u6709<\/p>\n

    \n
  1. \u53cd\u9988\uff1a\u4f8b\u5982 PLI , NACK<\/li>\n
  2. \u5197\u4f59\uff0c \u4f8b\u5982 FEC, RTX<\/li>\n
  3. \u8c03\u6574\uff1a\u4f8b\u5982\u7801\u7387\uff0c\u5206\u8fa8\u7387\u53ca\u5e27\u7387\u7684\u8c03\u6574<\/li>\n
  4. \u7f13\u5b58: \u4f8b\u5982 Receive Adaptive Jitter Buffer, Send Buffer<\/li>\n<\/ol>\n

    \u8fd9\u4e9b\u63aa\u65bd\u7684\u91c7\u7528\u9700\u8981\u57fa\u4e8e\u62e5\u585e\u63a7\u5236(congestion control) \u53ca\u5e26\u5bbd\u4f30\u8ba1(bandwidth estimation)\u6280\u672f, \u4e0d\u540c\u7684\u7f51\u7edc\u6761\u4ef6\u4e0b\u9700\u8981\u91c7\u7528\u4e0d\u540c\u7684\u63aa\u65bd\u3002<\/p>\n

    Webrtc \u9ed8\u8ba4\u662f\u5f00\u542f RTX (\u91cd\u4f20)\uff0c\u5b83\u4e00\u822c\u91c7\u7528\u4e0d\u540c\u7684 SSRC \u8fdb\u884c\u4f20\u8f93<\/p>\n

    RTX \u5305\u7684 Payload \u5728 RFC4588 \u4e2d\u6709\u8be6\u7ec6\u63cf\u8ff0\uff0c\u4e00\u822c NACK \u548c Bandwidth Probe \u4e5f\u53ef\u80fd\u8d70 RTX \u901a\u9053\u3002<\/p>\n

    FEC \u7528\u4f5c\u4e22\u5305\u6062\u590d\u9700\u8981\u5360\u7528\u66f4\u591a\u7684\u5e26\u5bbd\uff0c\u5373\u4f7f 5% \u7684\u4e22\u5305\u9700\u8981\u51e0\u4e4e\u4e00\u500d\u7684\u5e26\u5bbd\uff0c\u5728\u5e26\u5bbd\u6709\u9650\u7684\u60c5\u51b5\u4e0b\u53ef\u80fd\u4f1a\u4f7f\u60c5\u51b5\u66f4\u7cdf\u3002<\/p>\n

    RTX \u4e0d\u4f1a\u5360\u7528\u592a\u591a\u7684\u5e26\u5bbd\uff0c\u63a5\u6536\u65b9\u53d1\u9001 NACK \u6307\u660e\u54ea\u4e9b\u5305\u4e22\u5931\u4e86\uff0c\u53d1\u9001\u65b9\u901a\u8fc7\u5355\u72ec\u7684 RTP \u6d41\uff08\u4e0d\u540c\u7684 SSRC\uff09\u6765\u91cd\u4f20\u4e22\u5931\u7684\u5305\uff0c\u4f46\u662f RTX \u81f3\u5c11\u9700\u8981\u4e00\u4e2a RTT \u6765\u4fee\u590d\u4e22\u5931\u7684\u5305\u3002<\/p>\n

    \u97f3\u9891\u6d41\u5bf9\u4e8e\u5ef6\u8fdf\u5f88\u654f\u611f\uff0c\u800c\u4e14\u5360\u7528\u5e26\u5bbd\u4e0d\u591a\uff0c\u6240\u4ee5\u7528 FEC \u66f4\u597d\u3002
    \n\u89c6\u9891\u6d41\u5bf9\u4e8e\u5ef6\u8fdf\u6ca1\u90a3\u4e48\u654f\u611f\uff0c\u800c\u4e14\u5360\u7528\u5e26\u5bbd\u5f88\u591a\uff0c\u6240\u4ee5\u7528 RTX \u66f4\u597d\u3002<\/p>\n

    RTX packet \u7684\u5904\u7406<\/p>\n

    void RtxReceiveStream::SetAssociatedPayloadTypes(\n    std::map<int, int> associated_payload_types) {\n  RTC_DCHECK_RUN_ON(&packet_checker_);\n  associated_payload_types_ = std::move(associated_payload_types);\n}\n\nvoid RtxReceiveStream::OnRtpPacket(const RtpPacketReceived& rtx_packet) {\n  RTC_DCHECK_RUN_ON(&packet_checker_);\n  if (rtp_receive_statistics_) {\n    rtp_receive_statistics_->OnRtpPacket(rtx_packet);\n  }\n  rtc::ArrayView<const uint8_t> payload = rtx_packet.payload();\n\n  if (payload.size() < kRtxHeaderSize) {\n    return;\n  }\n\n  auto it = associated_payload_types_.find(rtx_packet.PayloadType());\n  if (it == associated_payload_types_.end()) {\n    RTC_DLOG(LS_VERBOSE) << "Unknown payload type "\n                         << static_cast<int>(rtx_packet.PayloadType())\n                         << " on rtx ssrc " << rtx_packet.Ssrc();\n    return;\n  }\n  RtpPacketReceived media_packet;\n  media_packet.CopyHeaderFrom(rtx_packet);\n\n  media_packet.SetSsrc(media_ssrc_);\n  media_packet.SetSequenceNumber((payload[0] << 8) + payload[1]);\n  media_packet.SetPayloadType(it->second);\n  media_packet.set_recovered(true);\n  media_packet.set_arrival_time(rtx_packet.arrival_time());\n\n  \/\/ Skip the RTX header.\n  rtc::ArrayView<const uint8_t> rtx_payload = payload.subview(kRtxHeaderSize);\n\n  uint8_t* media_payload = media_packet.AllocatePayload(rtx_payload.size());\n  RTC_DCHECK(media_payload != nullptr);\n\n  memcpy(media_payload, rtx_payload.data(), rtx_payload.size());\n\n  media_sink_->OnRtpPacket(media_packet);\n}<\/code><\/pre>\n
    Reference<\/h1>\n