UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.87 Safari/537.36

Example URL:
see attached HTML

Steps to reproduce the problem:
1. Download the attached bugreport.html
2. Prepare a streamable 4K h264 video as bugreport.mp4. Here are the steps I followed on OS X (the content’s license prevents me from sharing the resulting file): 
   a. Download http://hwcdn.net/j9t9v3v5/cds/Foreman_H264.mp4 
   b. Download FreeMonoBold.ttf from http://www.fonts2u.com/free-monospaced-bold.font and unzip it. 
   c. Install ffmpeg with freetype support: brew install ffmpeg --with-freetype 
   d. Run: ffmpeg -y -i Foreman_H264.mp4 -vf "drawtext=x=0:y=0:fontcolor=white:fontsize=72:fontfile=FreeMono/FreeMonoBold.ttf:text='%{pts\:flt}':box=1:boxcolor=black" -movflags "empty_moov+default_base_moof+frag_keyframe" bugreport.mp4 
3. Run an HTTP server: python -m SimpleHTTPServer 8000 
4. Open: http://localhost:8000/bugreport.html 
5. Watch both videos play at 16x speed. The top video plays using a regular “src” URL, the bottom uses Media Source Extensions. The video’s reported currentTime is shown above each video. When using SimpleHTTPServer, sometimes the top video will stop playing because the server doesn’t properly support HTTP range requests, but that is irrelevant to this issue, and reloading the page usually works around it.

What is the expected behavior?
Both videos should behave like the non-MSE video: when playback lags, the currentTime does not advance, so that it’s always close to the timestamp displayed in the video (or slightly behind).

What went wrong?
The currentTime of the MSE video races ahead of the displayed video frame, so that it reaches t=10 seconds while the video is still at t=2 seconds.

Did this work before? N/A 

Is it a problem with Flash or HTML5? HTML5

Does this work in other browsers? Yes 

Chrome version: 49.0.2623.87  Channel: n/a
OS Version: OS X 10.11.4
Flash Version: Shockwave Flash 21.0 r0

Firefox 45.0 behaves correctly on OS X and Ubuntu.

Playing videos at high speed makes it easier to reproduce the issue, but we’ve seen the same issue playing higher-resolution videos at 1x speed. We’ve reproduced the issue on OS X (with and without GPU decoding), Ubuntu (without GPU decoding), and Windows (without GPU decoding).
 

Deleted: bugreport.html 3.1 KB

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