TypeError: null is not an object (evaluating 'this.fragmentTracker.getPartialFragment')

[green-coder]

On hls v1.0.0, on a video which I cannot share.

By following the snippet from the documentation:

hls.on(Hls.Events.ERROR, function (event, data) {
  if (data.fatal) {
    switch (data.type) {
      case Hls.ErrorTypes.NETWORK_ERROR:
        // try to recover network error
        console.log('fatal network error encountered, try to recover');
        hls.startLoad();
        break;
      case Hls.ErrorTypes.MEDIA_ERROR:
        console.log('fatal media error encountered, try to recover');
        hls.recoverMediaError();
        break;
      default:
        // cannot recover
        hls.destroy();
        break;
    }
  }
});

After calling hls.recoverMediaError();, I get the error:

TypeError: null is not an object (evaluating 'this.fragmentTracker.getPartialFragment')

The error seems to come from

hls.js/src/controller/gap-controller.ts

Line 169 in b0fa62d

const partial = fragmentTracker.getPartialFragment(currentTime);

fragmentTracker seems to be null.

[robwalch]

Hi @green-coder,

Was hls.recoverMediaError() called after hls.destroy()?

I think fragmentTracker would only be null if the player was destroyed first. I cannot confirm without steps to reproduce.

Maybe we need something like #3710 for recoverMediaError? The thing is destroy removes all listeners and calling these two methods sequentially does not reproduce the issue for me. I do need a stream, and I need to know what sequence of events (and specific errors) lead to this exception.

[robwalch]

Please fill out the Bug Report Template as part of your issue, making sure to include:

• Test stream/page (if possible)
• Steps to reproduce
• Expected behavior
• Actual behavior

If the issue is related to your stream, and you cannot share the stream, please include all the information we would need to reproduce the issue. This includes how to generate a stream that reproduces the issue.

[green-coder]

hls.recoverMediaError() was called before hls.destroy(), on an event where fatal was false.

The stream on which I had the problem is one that does not play well specifically via Hls on Safari. I am sorry that I cannot share the stream, but I will come back if I can reproduce the problem on a sharable stream.

[robwalch]

Thanks @green-coder,

I've looked through the src and can't see how this could happen without either the gap-controller being initialized with a null for a fragmentTracker (unlikely) or gap-controller being destroyed first which is the only place its fragmentTracker is set to null.

gap-controller is the only module where fragmentTracker.getPartialFragment is called. and it's called with onTickEnd from the main stream-controller.

Maybe hls.destroy() was called in response to an event emitted in the stream-controller's tick. In that case, we might want to exit early from doTick or onTickEnd. Even that seems unlikely as checkBuffer which is part of that chain would exit early if the player was destroyed.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.