- "manifest" -> "playlist"?
- Retaining Input instances for segments without clogging up memory indefinitely

idea: discontinuities with extra decoder config on the packet.
Also, why not just have the packet metadata on the packet? I think that would make things easier overall.
Also: for robustness, do a different track matching algorithm for hls playback. so not use pid but make it simpler like
  if theres only 1 video track then its obvious yknow. Need to see if this is actually needed in the case of ext-x-discontinuity

- EXT-X-MEDIA (DONE, but surface more metadata from it, like language and shit) - should it be passed down to the tracks??
- getSegments() API? Any point in partially reading the playlist file? Idk

- Timestamp across variants; i think the date should actually be used. Make the timestamp relative to the date? How does that play with timeResolution?

- ALL_FORMATS but for HLS only

- computeDuration and getFirstTimestamp are dangerous with HLS
- keep input/demuxer.isSupported()?