diff options
| -rw-r--r-- | youtube/static/js/av-merge.js | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/youtube/static/js/av-merge.js b/youtube/static/js/av-merge.js index fb8b50c..8915ba6 100644 --- a/youtube/static/js/av-merge.js +++ b/youtube/static/js/av-merge.js @@ -316,7 +316,38 @@ Stream.prototype.segmentInBuffer = function(segmentIdx) { var entry = this.sidx.entries[segmentIdx]; // allow for 0.01 second error var timeStart = entry.tickStart/this.sidx.timeScale + 0.01; - var timeEnd = (entry.tickEnd+1)/this.sidx.timeScale - 0.01; + + /* Some of YouTube's mp4 fragments are malformed, with half-frame + playback gaps. In this video at 240p (timeScale = 90000 ticks/second) + https://www.youtube.com/watch?v=ZhOQCwJvwlo + segment 4 (starting at 0) is claimed in the sidx table to have + a duration of 388500 ticks, but closer examination of the file using + Bento4 mp4dump shows that the segment has 129 frames at 3000 ticks + per frame, which gives an actual duration of 38700 (1500 less than + claimed). The file is 30 fps, so this error is exactly half a frame. + + Note that the base_media_decode_time exactly matches the tickStart, + so the media decoder is being given a time gap of half a frame. + + The practical result of this is that sourceBuffer.buffered reports + a timeRange.end that is less than expected for that segment, resulting in + a false determination that the browser has deleted a segment. + + Segment 5 has the opposite issue, where it has a 1500 tick surplus of video + data compared to the sidx length. Segments 6 and 7 also have this + deficit-surplus pattern. + + This might have something to do with the fact that the video also + has 60 fps formats. In order to allow for adaptive streaming and seamless + quality switching, YouTube likely encodes their formats to line up nicely. + Either there is a bug in their encoder, or this is intentional. Allow for + up to 1 frame-time of error to work around this issue. */ + if (this.streamType == 'video') + var endError = 1/(this.avMerge.videoSource.fps || 30); + else + var endError = 0.01 + var timeEnd = (entry.tickEnd+1)/this.sidx.timeScale - endError; + var timeRanges = this.sourceBuffer.buffered; for (var i=0; i < timeRanges.length; i++) { if (timeRanges.start(i) <= timeStart && timeEnd <= timeRanges.end(i)) { |