[vlc-devel] RFC: vlc_player: SPU tracks: subtitles, DVD/Bluray menus and teletext

Francois Cartegnie fcvlcdev at free.fr
Mon Oct 15 15:36:04 CEST 2018

Le 15/10/2018 à 14:48, Thomas Guillem a écrit :
> Hello,
> I have some questions about how we expose the SPU track listing with the future vlc_player.
>  - 1/ Do we want to expose all SPUS from the track listing ? Is it coherent to expose the DVD menu track (the one that highlight) ? IMHO, it should be hidden (but we need to patch dvdnav and maybe add  a new variable in subs_format_t to detect it).

dvdnav never sent SPU menus, that's bluray.

>  - 2/ What about teletext ? I think we want to expose the teletext page that are closed captions, (generally magazine=8, page >= 0x88), and hide the teletext menu (magazine = 1, page = 0) from the track listing. Users will be able to select teletext subtitles via the subtitle track menu, and activate the teletext menu via a specfic vlc player call. Questions: are we sure that the menu is always 100 ?

Teletext is multiplexed. Same stream can carry subtitles and menus. But
that can also be carried in multiple different ES.
DVB SI defines full signaling (type, page), hence the "split-es" code in
TS to create multiple ES, allowing to select language per page.
(as we can't expose/do sub-es selection in decoders)

Menu (if any) on first 3 digits page 100. Might be none.
888 (not only) is subtitles.

>  - 3/ Do we want to keep the name "SPU" ? It's a VLC internal term. If we hide SPU tracks that are not subtitles (DVD/Bluray menus and teletext menu), we could name it "Subtitle".

Subtitles can work, but technically teletext and DVB are bitmap, so
still SPU.

> From the UI perspective: QT and maybe all others UI  have a Subtitle menu that allow to select any SPU (even menus). I don't think we want to keep that.

See 1: Menus are not SPU. Only menu overlays are. It should not appear
as SPU, and probably should go inside same ES as sidedata (but would
need empty packets) or in a similar dvdnav way ES_out control.

Francois Cartegnie
VideoLAN - VLC Developer

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