Fix CAN-SKIP-UNTIL and delta generation

[sgfn]

• Bumped playlist version for deltas to 9, as per https://datatracker.ietf.org/doc/html/draft-pantos-hls-rfc8216bis#section-8

• Sources for CAN-SKIP-UNTIL calculation:

  • https://developer.apple.com/videos/play/wwdc2020/10230/
  • https://mailarchive.ietf.org/arch/msg/hls-interest/RWf1XGVLE8QTjUI16mI9Ajso6YU/

As per comments in tests, delta can be created whenever the sum of durations of full segments in playlist exceeds 6 * TARGET-DURATION

[sgfn]

This is really strange. Without the pipe to Function.identity or IO.inspect, Dialyzer gives the following errors:

lib/membrane_http_adaptive_stream/hls.ex:123:pattern_match
The pattern can never match the type.

Pattern:
{:create_delta, _delta_ctx}

Type:
:dont_create_delta

________________________________________________________________________________
lib/membrane_http_adaptive_stream/hls.ex:179:pattern_match
The pattern can never match the type.

Pattern:
_track = %Membrane.HTTPAdaptiveStream.Manifest.Track{}, [{:delta?, true}]

Type:
atom() | map(), [{:delta?, false}, ...]

________________________________________________________________________________
lib/membrane_http_adaptive_stream/hls.ex:303:guard_fail
The guard clause:

when _segments_to_skip_count :: 0 > 0

can never succeed.

________________________________________________________________________________
lib/membrane_http_adaptive_stream/hls.ex:405:guard_fail
The guard clause:

when _duration :: 0 > 0

can never succeed.

________________________________________________________________________________
done (warnings were emitted)
Halting VM with exit status 2

Seems to be a bug in the utility.

[Karolk99]

if we want to merge it before the dialyzer fix I would prefer to use the @dialyzer tag to skip checking this function and some comment then Function.identity()

[Karolk99]

if we want to merge it before the dialyzer fix I would prefer to use the @dialyzer tag to skip checking this function and some comment then Function.identity()