Ignore representations which use incompatible codecs for TrickMode

[avelad]

Resolves: #2846

[TheModMaker]

It's not the job of the DASH parser to filter compatible tracks, it should just parse and report the manifest. This would be better done in shaka.util.StreamUtils, which handles filtering out incompatible streams. You could just set the stream.trickModeVideo to null.

[avelad]

@TheModMaker In stream #2846 there are two representations with two different codecs (H264 and H265). Since right now there is only one trickMode track, if I choose H265 (which is the one that comes first) and then filter, I leave the user without that track. With my change this would not happen, since H264 would be chosen. I understand the parser shouldn't do this, but the change would be to add trickMode (#872) multi-track support and then do filtering (this is much more complex).

[TheModMaker]

In that case, how about just comparing the codec of the trick mode track to match the parent? We don't support codec switching, so the stream filtering will do this anyway. Then, you should include a comment referencing #1528. You can use shaka.util.MimeUtils.getCodecBase to compare the codecs.

[avelad]

@TheModMaker I updated the implementation based on your comment. Can you check again?

[TheModMaker]

I suggest changing this to use trickModeVideo field directly. That ensures we don't get false-positive if the video is null.

Suggested change

	expect(trickModeVideo).toBeUndefined();
	expect(manifest.variants[0].video.trickModeVideo).toBeFalsy();

[avelad]

Done!

[shaka-bot]

All tests passed!