[FFmpeg-devel] [Sponsored work] ASCII Text subtitles in DVB subtitles

[Andrey Utkin]

2014/1/12 Sylvain <sylvain at lahiette.com>:
> Thanks for you response.
>
> In fact it is possible to send text subtitles in EN 300 743, in
> addition of bitmap subtitles. The documents states that transfering
> text-only strings shall be negotiated between the broadcaster and the
> set-top-box manufacturer, as they need to agree on the font used on
> the decoder side (at least). See page 26 of  ETSI EN 300 743 V1.2.1,
> field "object_coded_method". .

There's indeed something looking like text info, but not exactly usual
text strings:

character_code (it is 16 bits each - my remark): Specifies a character
through its index number in the character table identified in the
subtitle_descriptor. Each reference to the character table is counted
as a separate character code, even if the resulting
character is non spacing. For instance floating accents are counted as
separate character codes.

Floating accents as separate character codes - looks unusual for any
encoding i know.
How exactly the character table should be defined in
subtitle_descriptor is not defined in the doc, and anywhere else.
So this looks to be left implementation specific, although i am not sure yet.
In such case i think it is not probable that a patch for such feature
could be included into ffmpeg mainstream. But anything is possible in
private development.

> In fact, i am searching a way to push TXT-subtiles, as well as bitmap
> subtiltes at the same time. Hence my request. I did not check for dvb-
> teletext and i will look into it to see if it fit my needs.

Please check it, it seems more usable way to move on.

-- 
Andrey Utkin