teletext / zvbi -> dvbsub

[laursen]

Hi I would like to sponsor project adding to ffmpeg encoding dvb_teletext (EN 300 472) into dvb_subtitles (EN 300 743).

Here is a sample file with DVB teletext subtitles:
​​http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket2086/teletextsubtitles.ts

There is 2 ways as faar as i can see :

1, Make libzvbi decode bitmaps the dvbsub encoder can take, or make the dvbsub encoder take the current zvbi bitmap output and make it into something that can be feed into the current dvbsub encoder.

From what i understand this is the problem :
ffmpeg -i ~/Downloads/teletextsubtitles.ts -acodec copy -vcodec copy
-scodec dvb_subtitle -y -f mpegts /dev/null
fails with message "Subtitle encoding failed". Problem is caused by
subtitle regions having 41 color in palette, which is too big for
supported modes in dvb_subtitle format.
Link : https://ffmpeg.org/pipermail/ffmpeg-devel/2014-January/153114.html

2, Make a rasterizer for the dvbsub and perhaps other subtitle encoders in ffmpeg, so the text based zvbi output can be feed into the dvbsub encoder.

I think method 2 would be a great addon to ffmpeg making it able convert text based subtitles into picture based it would help dvdsub encoder also. But it would also be fine with method 1.

I will provide more info and test files on request.

[Hyponic]

+1 this function would be very very helpful. i would easily sponsor this too.

[malakudi]

Can someone indicate what is the input that dvbsub encoder expects?

[laursen]

Replying to malakudi:

Can someone indicate what is the input that dvbsub encoder expects?

Seems like its RGB
​https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/dvbsub.c#L324

[Marton Balint]

I am just saying, that colors above index 8 are rarely used, so if you are not using txt_opacity you can probably hack libzvbi-teletextdec.c and set sub_rect->nb_colors to 16, and make this work until somebody fixes it properly.