Add support for DASH patch manifests (<PatchLocation>)

Have you read the FAQ and checked for duplicate open issues? Yes

Is your feature request related to a problem? Please describe.

Manifest updates can be expensive in some cases.

Describe the solution you’d like

DASH has now introduced <PatchLocation> and <Patch>, which give a way to update a small part of the existing manifest instead of re-parsing and merging every time.

Additional context

TODO: Get references to the spec on this (AMD.1, landing in 4th edition according to Hulu)

TOTO: Get sample content for this (should be coming soon to the DASH live sim, according to Hulu)

[technogeek00]

Chiming in to drop a link to the finalized text in the 5th edition which is freely available on ISO: https://standards.iso.org/ittf/PubliclyAvailableStandards/c083314_ISO_IEC 23009-1_2022(en).zip

I’d defer to Shaka team on the player semantics in the proposal, but left some comments on the path selection understanding as there are explicit path addressing restrictions that should simplify implementations and must be followed for a compliant implementation:

5.15.3.4 Element Addressing Restrictions The following element addressing restrictions apply for DASH MPD elements:

• Elements with an @id attribute with uniqueness requirement among its siblings present shall only be identified by the value of this attribute. In particular, Period, AdaptationSet, Representation, and SubRepresentation shall be only addressed via their @id.
• DescriptorType elements with an @schemeIdUri attribute shall be identified by the value of this attribute, for example SupplementalProperty.
• S elements shall be addressed in one of the following ways:
  • @t or @n attribute of S elements if the said attribute is present in the S element.
  • by position.
• All other elements shall be addressed by position, e.g. SegmentTemplate[1].

Examples:

/MPD/Period[@id="1"]/AdaptationSet[@id="1"]/SegmentTemplate[1]/SegmentTimeline[1]/S[@t="12345"]

/MPD/Period[@id="1"]/AdaptationSet[@id="1"]/SegmentTemplate[1]/SegmentTimeline[1]/S[42]@r

I’m happy to review a PR for standards compliance semantics when it is ready.

[dave-nicholas]

@technogeek00 Thank you greatly for your input, we are in the process of trying to get an AdapatationSet@id added to our streams. I am in the currently creating a POC that I will present for review once ready.