Frame dropped at multi-period boundary due to inaccurate Period@duration #368
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type: bug
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shaka-bot
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Apr 13, 2018
This flag was introduced to workaround a rounding error in Chrome (probably in other browsers too). Also although this flag avoids the first frame of a Period to be dropped due to rounding error but it could cause the last frame of a Period to be dropped. Now that we use a high precision Period@duration, we do not expect to see rounding errors any more. The player would be a better place for the workaround even if it is still needed. Related issue: #368. Change-Id: I3bd517ecc6d548ff62e0c13394edb49d4bc68e8f
kqyang
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Apr 20, 2018
Chrome internally uses time accurate to microseconds, which is implemented per MSE spec (https://www.w3.org/TR/media-source/). Generate Period@duration with better precision to avoid possible buffered range gaps in Chrome (possibly other browsers too), which may lead to other problems like playback stall. b/74238961 Fixes #368. Change-Id: I357a0f62b67f75c7ca044bb99ea4e3c8bbb6fecd
kqyang
added a commit
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Apr 20, 2018
This flag was introduced to workaround a rounding error in Chrome (probably in other browsers too). Also although this flag avoids the first frame of a Period to be dropped due to rounding error but it could cause the last frame of a Period to be dropped. Now that we use a high precision Period@duration, we do not expect to see rounding errors any more. The player would be a better place for the workaround even if it is still needed. Related issue: #368. Change-Id: I3bd517ecc6d548ff62e0c13394edb49d4bc68e8f
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Cherry-picked for v2.0.3. |
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System info
Operating System: Debian 4.9.65
Shaka Packager Version: v2.0.2 with changes
Chrome Version: v65.0.3325.181
Player Version: Shaka Player v2.3.5
Issue and steps to reproduce the problem
Packager Command:
./packager ... --ad_cues '10;29;300'
Extra steps to reproduce the problem?
(1) Play the generated manifest (https://storage.googleapis.com/wvtemp/kqyang/ads4/out.mpd) in Shaka Player
What is the expected result?
Play smoothly.
What happens instead?
Seeing intermittent stalls at multi-period boundary, e.g. at ~12 seconds, ~30 seconds etc.
MPD:
Observation on Chrome with additional debugging:
Clearly there is a rounding error in Chrome causing the frame to be dropped, which causes a gap in buffered range. This in turn leads to playback stalls (not sure why yet).
Chrome internally uses time accurate to microseconds, which is required by MSE spec. To avoid rounding errors like this in browsers, we should generate Period@duration with better than microseconds accuracy.
This problem can also be workarounded in player by having a fudge factor in appendWindowEnd, like what Shaka Player already does in appendWindowStart.
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