Sorting of pts causes Chrome to display incorrect CEA-608 embedded captions about mux.js

[ianwelsh]

I believe this is due to Chrome having an unstable Array.prototype.sort() implementation (https://bugs.chromium.org/p/v8/issues/detail?id=90), whereas Firefox and Safari have stable implementations.

Example

Pre-sort:

[{"type":0,"pts":8353875960,"ccData":8320},
{"type":0,"pts":8353875960,"ccData":37925},
{"type":0,"pts":8353875960,"ccData":38061}]

Post-sort in Chrome:

[{"type":0,"pts":8353875960,"ccData":37925},
{"type":0,"pts":8353875960,"ccData":38061},
{"type":0,"pts":8353875960,"ccData":8320}]

Post-sort in Firefox:

[{"type":0,"pts":8353875960,"ccData":8320},
{"type":0,"pts":8353875960,"ccData":37925},
{"type":0,"pts":8353875960,"ccData":38061}]

Any reason why I shouldn't take out the sort? Are there any conditions where the caption packets would get unsorted?

[dmlap]

@ianwelsh if the video is encoded with b-frames, caption packets will arrive out-of-order and so it's important to resort them before display. Good find about the unstable sort() though! I suspect you're right and that is causing the problem. We should find some way to disambiguate our comparator so that there are no equivalent caption packets during the sorting.