dvdsub -> dvbsub: color palette and postion do not match

[Jarod42]

Summary of the bug:
Today I used ffmpeg to remux a VOB file to TS. After remuxing I realized, that the DVB subtitles did not match the original DVD subtitles. The colors did not match and the position was shifted.
I was able to reproduce this with this sample here (​http://samples.ffmpeg.org/MPEG-VOB/ClosedCaptions/Starship_Troopers.vob) and got the exact same results.

How to reproduce:

% ffmpeg -fflags +genpts -analyzeduration 100000k -probesize 100000k -i Starship_Troopers.vob -c:v copy  -c:a copy -c:s dvbsub -map 0:0 -map 0:4 -map 0:7 -metadata:s:s:0 language=eng -metadata:s:a:0 language=eng -f mpegts SST.ts

ffmpeg version N-46340-gff68ceb
built on Ubuntu 14.04 x86_64

See attached pics.

[Jarod42]

DVD Subtitles

[Jarod42]

DVB Subtitles

[Carl Eugen Hoyos]

Is encoding to dvbsub really necessary to reproduce the "issue" you see (that vob files do not contain a palette)? Or does using overlay show the same result indicating that this is not related to dvbsub at all?
Use the -palette option if you don't like the default palette:
​http://ffmpeg.org/ffmpeg-codecs.html#dvdsub

[Jarod42]

I need to create a TS from the video source, so converting dvdsubs to dvbsubs is required.
After figuring out, that the -palette option needs to be put before the input file, the color "mismatch" problem is solved.
The position of the subs however does not match the original. After a closer look at the converted subs I figured they are shrunk vertically. So I tried to resize them using -s:s:0 720x576 which unfortunately did not have any effect.

[Carl Eugen Hoyos]

Replying to Jarod42:

I need to create a TS from the video source, so converting dvdsubs to dvbsubs is required.

I understand that this is your usecase. But a bug report should be as simple as possible and reading your original report makes one believe that there is an issue creating dvbsub subtitles.

The position of the subs however does not match the original. After a closer look at the converted subs I figured they are shrunk vertically. So I tried to resize them using -s:s:0 720x576 which unfortunately did not have any effect.

I cannot reproduce this here and I don't see it looking at your screenshots either. Is the difference very small?

[Jarod42]

both subs on one pic

[Jarod42]

I created a third picture from the two already attached pics where I put the picture with the converted subs (yellow) over the original (white).
It is clear to see that they are not at the same position, nor are they the same size.

[Carl Eugen Hoyos]

I still cannot reproduce: The word three is over Ibanez' right hand here, both on the original (vob) file and for the reencoded transport stream.
Which application did you use for playing the transport stream?

[Jarod42]

I was using VLC 2.1.5 to replay the TS and that might be the cause. When using ffplay the subs are at the same position, before and after the conversion.

[Jarod42]

Screenshot taken from vdr-2.1.6

[Jarod42]

Today I did another test with VDR 2.1.6. I used it to replay the short sample with re-encoded subs to dvbsubs and a custom palette. The position of the subs do not match the ones from the VOB. So far ffplay seems to be the only program to display the subtititles at their correct position.

[Anshul]

When we play Starship_Troopers.vob using ffplay the subtitles are green color, while in vlc they are White with black Shadow, Imo it looks like there is some problem in decoder of dvbsubdec.

[Carl Eugen Hoyos]

A vob file does not contain subtitle colour information, there is no bug regarding the colour of the subtitle that can be fixed within the subtitle decoder when playing this file.