Support DISCONTINUITY in HLS playlists

[jeroen]

The HLS framework currently doesn't support the DISCONTINUITY tag. We should look into adding it, since it's useful for broadcasters. Description:

The EXT-X-DISCONTINUITY tag indicates an encoding discontinuity between the media file that follows it and the one that preceded it. The set of characteristics that MAY change is:

• file format
• number and type of tracks
• encoding parameters
• encoding sequence
• timestamp sequence

Its format is:

#EXT-X-DISCONTINUITY

Two example streams are available on playertest:

• adaptive/bipbop/discontinuity.m3u8
  • This one has the first 3 fragments from gear1, then the first 3 fragments from gear4.
• adaptive/boxee/playlist.m3u8
  • This one has a single weak signal fragment, repeated 7 times.

The keys in supporting these streams seem:

1. Ensure the encoders get re-set (new SPS/PPS parsing, new Tag array, etc)
2. Ensure the timeline does not get re-set (while the timestamps in the tags may change).

[jeroen]

Some great feedback (including patch and test stream) from Tuomas Huhtanen. We should check them out and add the stream to our tests:

I did not find information how to contribute, so I'll add links to patches here. These patches are applicable to adaptive branch @ rev 2107. In order to be able to play our stream two modifications were necessary. First one is the Buffer check removal mentioned in previous post. Patch can be found at:

 http://norsu.saunalahti.fi/jwplayer/0001-Send-all-buffered-tags-to-NetStream..patch

The second modification was support for discontinuous ts-stream. The support is actually quite easy, minor change to sorting of tags and resetting the netstream on discontinuity. Patch for the discontinuity support can be found at:

 http://norsu.saunalahti.fi/jwplayer/0002-Add-support-for-playing-discontinuous-ts-stream.patch

For testing purposes, I created a playlist with two segments in assets/discontinuity. The patch for the test can be found at:

 http://norsu.saunalahti.fi/jwplayer/0001-Add-test-case-for-discontinuity-playlist.patch

[jeroen]

See the forum thread for additional updates and patches:

http://www.longtailvideo.com/support/forums/jw-player/player-development-and-customization/26771/

[jeroen]

Not seen any requests for this to date...

[sanil]

Discontinuity tag support added in [2989]