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Delay from live default is too high under 2.3 #1542

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wilaw opened this issue Aug 16, 2016 · 1 comment
Closed
3 tasks done

Delay from live default is too high under 2.3 #1542

wilaw opened this issue Aug 16, 2016 · 1 comment
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@wilaw
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wilaw commented Aug 16, 2016

Environment
Steps to reproduce
  1. Use this sample /samples/live-streaming/live-delay-comparison-custom-manifest.html
  2. Start with the default setting and the default stream of http://vm2.dashif.org/livesim/testpic_2s/Manifest.mpd
  3. Live delay estimate is shown as 20s behind live. This is too high. Default live delay is 4 segment durations, which should be ~8s.
  4. Use setLiveDelayFragmentCount to 0 and reload stream
  5. Live delay is now shown as ~14s, which is still too high.
  6. Values of setLiveDelayFragmentCount to 1,2 or 3 all produce a live delay of ~15s. There should be more variation.
Observed behavior
  1. The player is holding a larger default live delay than it should by ~ 12s.
  2. This 12s live delay seems to be added to any holdback specified by setLiveDelayFragmentCount or setLiveDelay.
  3. Use of setLiveDelayFragmentCount does not produce anticipated live delay values or variance when adjusted 0,1,2,3.
Console output
@dsparacio dsparacio self-assigned this Aug 16, 2016
@dsparacio dsparacio added the Bug label Aug 16, 2016
@wilaw
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wilaw commented Aug 17, 2016

Resolved. System clock on test machine was 9.6s slow compared to UTC. That sample http://dashif.org/reference/players/javascript/nightly/dash.js/samples/live-streaming/live-delay-comparison-custom-manifest.html uses system clock as the reference point, hence the stream appeared to be 9.6s further behind live than it really was. Once system clock was re-synced, live stream delay was within expected bounds.

@wilaw wilaw closed this as completed Aug 17, 2016
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