v2: Extract Teletext-format subtitles from MPEG-TS stream (own PID)

[ason-assistant]

Version: V2

Feature request: extract Teletext-format subtitles carried in an MPEG-TS stream as their own PID, so they can be surfaced/routed alongside the audio/video PIDs the Demuxer already exposes.

Context

MPEG-TS input streams often include a subtitle track encoded as Teletext (EBU EN 300 472 / DVB Teletext) on a dedicated PID. Today the Demuxer isn't extracting these, so downstream consumers can't get at the subtitle data.

Ask

• Detect Teletext-carrying PIDs on the Demuxer.
• Expose them as an output like other tracks, tagged as Teletext + page number where available.
• Downstream module(s) can then convert / forward / re-mux the subtitle payload.

I checked existing tickets and there is no prior issue for this (searched "teletext" / "subtitle" / "subtitles").

Reported by Ivan via Telegram.

[ason-assistant]

Note from Ivan: it may be feasible to convert the extracted Teletext subtitles to WebVTT as part of this pipeline — worth investigating alongside the raw Teletext output so downstream web/HLS consumers can render subtitles natively.

[ason-assistant]

Follow-up from Ivan: the WebVTT path is even more attractive because there's already built-in WebVTT support in the HLS pipe — so converted Teletext subtitles could drop straight into the existing HLS output without new plumbing on the delivery side.