Thanks for the follow-up and additional info.
You have posted the question on Azure Media Service, for targetted questions /specialized assistance, you post your question on respective forums (shared below), to receive insights from the targetted audience.
Having mentioned that, to help you pointed in the right direction, As outlined in this doc - Stream Live Events Replacement Service - the Stream live events service retires on January 31, 2024. Microsoft Teams live events, with encoder support, is the new platform to host and run live events.
What closed caption protocol does Teams live events support?
Teams live events supports CEA-608 and CEA-708 closed captions. Currently Teams live events supports only a single language track being sent in the stream.
Additional info:
If you may wish, please check out this training resources:
https://learn.microsoft.com/training/paths/m365-virtual-events-fundamentals/?source=recommendations --Deliver engaging and accessible virtual events with Microsoft Teams and Microsoft 365. Learn best practices for accessibility, inclusion, and engagement as you create your virtual event. Review processes that prioritize the clarity of your message, the attendee experience, and your ongoing engagement strategy.
Microsoft Stream (Classic) Support forum
Microsoft Teams : https://techcommunity.microsoft.com/t5/microsoft-teams/ct-p/MicrosoftTeams and https://support.microsoft.com/teams
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