WWDC2018： Measuring and Optimizing HLS Performance

https://developer.apple.com/videos/play/wwdc2018/502/#wwdc2018

• How to improve the quality of streaming and how to evaluate it

• 5 KPIs = evaluation criteria

  • Startup time (time to start playback)

    • Methods for improvement
    • If you want to play videos continuously, it’s good to preload the second video before going to it
    • Use AVQueuePlayer
    • Also, if you want to reduce buffering time, adjust the bitrate and other factors
      • Trade-off with initial video quality
    • This section wasn’t very helpful

  • Frequency of playback stalls

    • Can be measured using AVPlayerItemPlaybackStalled
    • To improve, make sure to have multiple bitrates available on the HLS server
    • ErrorLog and AccessLog can help identify issues
      • For example, if indicateBitrate is greater than observedBitrate, it means that data exceeding the bandwidth limit is being sent

  • Duration of playback stalls

    • Stall time per hour watched
    • Can be measured using playerItem.accessLog()

  • Video resolution

    • Look at the average bitrate

  • Streaming Error

    • The icon with a diagonal line on the play button
    • This can be addressed by examining the ErrorLog

• How to write m3u8

  • “Tell us everything you can” by Apple
  • Include codes, bandwidth, resolution, and everything else
  • If you do that, AVPlayer will do its best

• If you want to display thumbnails on the seek bar, you need to provide an I-frame playlist

• They also talked about multichannel audio, but I skipped that part because I’m not interested

• This talk seemed to focus more on playing existing videos rather than live streaming

• However, the optimization of stall time was useful as a reference.