Apply default flags and duration from trex box

[kanongil]

This PR will...

Fix playback of streams using fMP4 where the sample duration is stored in the trex box.

Why is this Pull Request needed?

To successfully play more streams.

Are there any points in the code the reviewer needs to double check?

No.

Resolves issues:

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

[robwalch]

Hi @kanongil,

Do you have a sample stream I can verify this fix with?

[kanongil]

Yes, I have a public stream here: https://stream.sob.m-dn.net/live/sb1/index.m3u8

This specific stream is not LL-HLS enabled yet, and appears ok, but will report errors in the console (on v1.0.0-alpha.2).

[robwalch]

Thanks @kanongil! Great fix and much appreciated.

I wonder if there are other circumstances where we wouldn't be able to determine the duration of fmp4. The console.asserts are helpful for catching these instances, but I haven't seen a wide variety of fmp4 streams, certainly not one like this.

d41f681 replaces the asserts with warnings, and falls back to playlist duration to avoid serious playback issues caused by mangled timelines that result from mp4 duration not being parsed.