Playback starts at segment boundary instead of whatever you set as currentTime

[dpieri]

Environment

• The MPD passes the DASH-IF Conformance Tool on http://dashif.org/conformance.html (Big Buck Bunny example)
• The stream has correct Access-Control-Allow-Origin headers (CORS)
• There are no network errors such as 404s in the browser console when trying to play the stream
• The issue observed is not mentioned on https://github.com/Dash-Industry-Forum/dash.js/wiki/FAQ
• The issue occurs in the latest reference client on http://reference.dashif.org/dash.js/ and not just on my page

• Link to playable MPD file: https://dash.akamaized.net/akamai/bbb_30fps/bbb_30fps.mpd
• Dash.js version: 2.6.4
• Browser name/version: Chrome 62
• OS name/version: OS X 10.11.6
• Codepen: https://codepen.io/anon/pen/eyYYVQ

Steps to reproduce

1. Set the native video element's currentTime to something that you know is not a segment boundary. Do this right after initializing the Dash player.
2. Do or don't start playing the video.

Observed behaviour

The video's currentTime will start of where you set it, but as the video buffers the time will go backwards. I've observed it go to 0, or to the start of an early segment. It seems it's related to how much of the video your browser already has cached.

Console output

Notice how after loading a fragment the time goes from 171.379 to 168.

[223] Getting the request for video time : 171.379 
[224] Index for video time 171.379 is 42 
[225] SegmentList: 168 / 349.267 
[226] ScheduleController video- getNextFragment - request is https://d11xfn549clyq.cloudfront.net/59efaac067282406f479dd24/video5400_dash.mp4 
[698] Buffered Range for type: video : 168  -  171.999999 
[699] Got enough buffer to start. 
[699] Requesting seek to time: 168 
[700] Seeking to: 168 

Originally reported in conversation about #2194 but @nicosang asked me to open a new issue for this.

[dpieri]

Using my Codepen example from above I think this issue was introduced in 2.6.0. I haven't been able to reproduce it in 2.5.0.

I've downgraded our own usage of Dashjs to 2.5.0. This bug is an upgrade blocker for us as one of our core UIs depends on precisely setting the video start time.

[epiclabsDASH]

@dpieri, could you please confirm PR #2341 fix this issue for you?

[dpieri]

Yes, it appears to be fixed! Thanks @epiclabsDASH!