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latency.md

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KVS/WebRTC SDK latency optimization checklist

Device(Camera):

  • DNS resolving time consuming
  • Modify the camera application to use the persistent connection
    • Dedicated signaling channel per device
    • Cache the signaling channel endpoint
      • To modify the policy of caching configuration: In WebRTC C SDK, “samples/Common.c”, modify “pSampleConfiguration→channelInfo.cachingPolicy = SIGNALING_API_CALL_CACHE_TYPE_FILE;” ENUM is defined in “src/include/com/amazonaws/kinesis/video/webrtcclient/Include.h”
    • Cache the TURN channel configure(5min), try to optimize DNS first
    • skip TURN DNS, just use ip address in the TURN URI
  • Apply ice filtering to exclude the IPv6 addresses
    • Disable IPv6 in device (generally). Disable IPv6 on master(camera) OS(etc. Linux)
    • Check device SDK will try IPv6 candidate from viewer or not
  • Add configuration for TURN On/Off
    • To modify ICE mode (TURN/STUN), please modify the code in WebRTC C SDK “sample/Common.c”: “configuration.iceTransportPolicy = ICE_TRANSPORT_POLICY_ALL;”, ENUM is defined in “src/include/com/amazonaws/kinesis/video/webrtcclient/Include.h”
  • Enable trickleIce using createSampleConfiguration and modify third parameter to true
    • When connect to Echo, please turn it off
  • Correlate the KVS Side metrics for WebRTC - send SDP offer/Answer link
    • API response latency/failure inside AWS service
  • KVS WebRTC Test Page
    • Google Chrome so that we can view the chrome://webrtc-internals
  • Cloudwatch metrics for KVS WebRTC

App (user):

  • In video player of mobile App, preload the WebRTC process before user click play button;
  • Cache the signaling channel endpoint, and periodically refresh the cached data; For input parameter, use the largest valid time value;
    • Timeout, refresh cycle is 1 hour.
  • Enable trickle ICE (both App & Device);
    • search code, look for “trickleICE”, and modify

How to optimize DNS resolving time consuming

  1. In src/source/Ice/Network.c, find STATUS getIpWithHostName(PCHAR hostname, PKvsIpAddress destIp) and insert timestamp measurment.
  2. If getIpWithHostName() takes long time (>1s), latency is caused by DNS resolving service
  3. Please
    • modify devices hostname file(Linux) to change DNS resolver.
    • contact IC module (e.g. Ingenic/Ankya...) supplier.
    • Parse the TURN url and return IP address.