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w3c / media-capabilities

Media Capabilities API
https://w3c.github.io/media-capabilities/
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Media Capabilities and HDR Dynamic Metadata #213

Open pauljhearty opened 8 months ago

pauljhearty commented 8 months ago

Please confirm that there is no assumption that only one form of HDR Dynamic Metadata can exist in media sources. It is possible, and anticipated in multiple standards, that a source may support HDR10 alone or HDR10 with one or both of ST2094-10 and ST2094-40.

jernoble commented 7 months ago

Hello Paul,

The intent of the API is to query for whether the specific configuration is supported by the platform. The answers to those capabilities checks are not intended to be exclusive; in other words, a successful query for "smpteSt2094-10" does not imply that an otherwise identical query for "smpteSt2094-40" would fail.

However, that's based on an assumption that, for a piece of content with (e.g.) both "smpteSt2094-10" and "smpteSt2094-40" metadata in-band, a user agent can choose to use one metadata type or the other. If instead, these metadata types are combinatorial (i.o.w., if both sets of metadata are used during decoding and/or presentation) then the Media Capabilities API isn't expressive enough to answer a query about whether that combination of metadata are supported.

So hopefully you can help us answer this question: when multiple types of metadata are included in a stream, are those metadata types exclusive, or are they used in combination with each other?

pauljhearty commented 7 months ago

Thank you for the clarification, Jer.

The expectation is that a single HDR program could have one or more independent HDR dynamic metadata types delivered in-band. A device could support 0, 1 or more dynamic metadata types. In the instance that the device supports more than one dynamic metadata type, a selection could be made by the operative application or by user preference.

Hope this helps.

Paul

jernoble commented 7 months ago

The expectation is that a single HDR program could have one or more independent HDR dynamic metadata types delivered in-band. A device could support 0, 1 or more dynamic metadata types. In the instance that the device supports more than one dynamic metadata type, a selection could be made by the operative application or by user preference.

Okay, by "independent HDR dynamic metadata types", then I believe that answers your original question:

Please confirm that there is no assumption that only one form of HDR Dynamic Metadata can exist in media sources.

Confirmed. Querying for one dynamic metadata type or another is fully supported, and there is no assumption that multiple independent metadata types cannot be contained within the same media source.

chrisn commented 7 months ago

In the instance that the device supports more than one dynamic metadata type, a selection could be made by the operative application or by user preference.

In this case, the browser would select which one to use. I don't think there's a facility for a web app to request use of one metadata type over another within the same content.