Pr for media sequence

[jontsnz]

Description

The browser tab running video.js would show a "Page Unresponsive" dialog in Chrome when the EXT-X-MEDIA-SEQUENCE tag increased by a large number between subsequent m3u8 files. This happened because the saveExpiredSegmentInfo function was iterating over this large number.

This behaviour was raised in issue 1197

Proposed Solution

The proposed solution is to avoid the browser becoming unresponsive by only iterating over the media sequence difference if it is within a reasonable threshold.

To determine a reasonable threshold, I looked at Apple's "Live Playlist (Sliding Window) Construction" page which states:

The EXT-X-MEDIA-SEQUENCE tag value must be incremented by 1 for every media URI that's removed from the playlist file.

Based on this, I have used a threshold of 1000.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[welcome]

💖 Thanks for opening this pull request! 💖

Things that will help get your PR across the finish line:

• Run npm run lint -- --errors locally to catch formatting errors earlier.
• Include tests when adding/changing behavior.
• Include screenshots and animated GIFs whenever possible.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[brandonocasey]

Thanks for the pull request! I think 1000 is sufficiently large here. I just have a small comment on the log message. Do you think you might have some time to write a test?

[codecov]

Codecov Report

Merging #1204 (4909989) into main (e2b46e7) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1204   +/-   ##
=======================================
  Coverage   86.33%   86.34%           
=======================================
  Files          39       39           
  Lines        9691     9695    +4     
  Branches     2243     2244    +1     
=======================================
+ Hits         8367     8371    +4     
  Misses       1324     1324           

Impacted Files	Coverage Δ
src/sync-controller.js	96.95% <100.00%> (+0.06%)	⬆️

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[brandonocasey]

One last change brought up internally.

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉