IETF MOQ WG: Knowing the start of a Subgroup

Message Snapshot

• List: moq@ietf.org
• Thread subject: Knowing the start of a Subgroup
• Message subject: [Moq] Re: Knowing the start of a Subgroup
• Author: Magnus Westerlund
• Published: 2026-04-30T09:22:29.000Z
• Source tag: ietf-mailing-list
• Message URL: Open in IETF Mail Archive

Summary

Magnus Westerlund posted to the MOQ working group mailing list on April 30, 2026. Hi, My worry is exactly related to that one would like to bind sub-group IDs to catalog info making clear what improvement a particular s…

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This message came from the public MOQ working group archive and captures active discussion, meeting coordination, or implementation feedback around Media over QUIC.

Message Excerpt

Hi, My worry is exactly related to that one would like to bind sub-group IDs to catalog info making clear what improvement a particular subgroup contains. I think this matters in two ways. First related to end subscriber processing it during decoding operations. This also matters if one want to use the sub group filte…

Plain-Text Body

Hi,

My worry is exactly related to that one would like to bind sub-group IDs to catalog info making clear what improvement a particular subgroup contains. I think this matters in two ways. First related to end subscriber processing it during decoding operations. This also matters if one want to use the sub group filter as the subscriber need to know that the publisher uses the subgroup IDs consistently.

With the proposal in place I think it limits the possibility to apply additional constraints on the object IDs. For example if one want the object IDs in decoding order without gaps across a full tree of different sub-groups then one have a constraint that may be difficult to fulfil if one need to reconfigure the encoder between groups to handle bandwidth limitation between the original publisher and the relay. The reconfiguration could mean skipping a sub group completely in this group. This will require a gap in the object ID to skip over the object ID = sub group ID.

Yes clearly if one assign no additional semantics and accept gaps in object IDs the idea in #1608 can work. However, I think it is limitation that people with more advanced use cases in the future will be annoyed with and may result in significantly more additional signalling about gaps etc than an explicit start of sub-group indicator would require.

Cheers

Magnus

From: Cullen Fluffy Jennings fluffy@iii.ca Date: Thursday, 30 April 2026 at 07:08 To: Ian Swett ianswett=40google.com@dmarc.ietf.org Cc: MOQ Mailing List moq@ietf.org Subject: [Moq] Re: Knowing the start of a Subgroup

Three thoughts ….

1. I don’t deeply care about this one way or the other but I think we should make it mirror the end marker bits. If the original publisher knows it is the start, or knows it is the end, it should add the marker. I think we should deal with start of track, start of group, at the same time as subgroup as it is the same issue.

2. Imagine a case where you want to refer to the SubGroup ID in the catalog to explain what layer of a codec is in that subgroup. And assume you want the object ID to increment by 1 in the group. I'm just not seeing how it works in this case.

3. Mostly I don’t worry about how we spell it on the wire but FWIW … My gut feel is we are pinning to very weird implicit signaling by taking two things that have nothing to do with each other, the subgroup id and the object id, then saying if they are equal, it means some third thing. I’d rather just explicitly signal the third thing and not have it be some implicit convention on how to use the first two things.