feat: Add MPD Patch support

[dave-nicholas]

Closes #2228

[github-actions]

Incremental code coverage: 92.32%

[joeyparrish]

Thank you for contributing!

I don't understand the patch adapter, though. I worry that it will not be representative of actual patch streams. I also see it being applied in the demo to a VOD manifest, which should have no need of patching. Patching is only useful for updates to live streams, correct?

[dave-nicholas]

Thank you for contributing!

I don't understand the patch adapter, though. I worry that it will not be representative of actual patch streams. I also see it being applied in the demo to a VOD manifest, which should have no need of patching. Patching is only useful for updates to live streams, correct?

Hi @joeyparrish

I agree with you that patch manifest adapter is not ideal, but I wanted to give the ability to test the feature in the demo app as open patch compliant streams are not easy to come by (at least I haven't seen any 😆 ). The reason I chose the ad enabled VOD is because of its behaviour of presenting new segments and periods regularly like a live stream.

I can remove remove the manifest adapter if you wish.

[dave-nicholas]

Hi @joeyparrish I have removed the patch adapter.
Please let me know if there any concerns or changes in approach that you would like me to make.
We will be taking this change into production shortly.

[Iragne]

Happy to support in this kink of new feature.
Let me know if you need help

[joeyparrish]

Overall, I would be comfortable with an "experimental" flag to enable this, but I want to ensure that the existing flow isn't broken. I'm most concerned about extra calls to combinePeriods (which can be expensive) and missing calls to set up caption streams.

[avelad]

@dave-nicholas @tykus160 Please add a Demo streams. You can use Dash-Industry-Forum/dash.js#4452 . With a reference stream in the Demo I will be able to review the change and test it for myself. Thanks!

[tobbee]

When running towards dash.js, some issues were fond in the ongoing development of MPD patch in livesim2. I think things should be good now, but if you find any issues, please report them to Dash-Industry-Forum/livesim2#174 or open a new issue if the PR is closed.

[tobbee]

The MPD Patch support is now on the public DASH-IF livesim2 server. Here is a possible test URL:

https://livesim2.dashif.org/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpd

[avelad]

The MPD Patch support is now on the public DASH-IF livesim2 server. Here is a possible test URL:

https://livesim2.dashif.org/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpd

@tobbee Your URL uses SegmentTimeline, is there any URL that uses SegmentList or SegmentBase?

[tykus160]

Added demo asset, thanks @tobbee. This PR still needs some love though, as initial scope of work is not sufficient to properly play DASH-IF asset. Me and @dave-nicholas will continue work on that.

[tobbee]

@avelad The output is "live" streams and available in three different formats:

• SegmentTemplate with $Number$: https://livesim2.dashif.org/livesim2/patch_60/testpic_2s/Manifest.mpd
• SegmentTimeline with $Number$: https://livesim2.dashif.org/livesim2/patch_60/segtimelinenr_1/testpic_2s/Manifest.mpd
• SegmentTimeline with $Time$: https://livesim2.dashif.org/livesim2/patch_60/segtimeline_1/testpic_2s/Manifest.mpd

SegmentList is not a format recommended by DASH-IF so it is not supported.
SegmentBase is only useful for VoD content in DASH OnDemand profile as far as I know, so it is irrelevant to live output.

I hope you can make these variants work (the first one has very little updates since no Segments are mentioned).

Once they work, one can also test with multiperiod variants by adding /periods_60 before testpic_2s in any of the above URLs like

https://livesim2.dashif.org/livesim2/patch_60/segtimeline_1/periods_60/testpic_2s/Manifest.mpd