[FFmpeg-user] Burning DVD subtitles into video using overlay filter not working

[Thierry Lelegard]

> De: "Paul B Mahol" <onemda at gmail.com>

[...]

>>> First, use -loglevel debug and look at the "palette:" lines: maybe
>>> the
>>> subtitles are completely transparent.
>>
>> Got the following. See the full output at the end of the mail.
>>
>> [dvdsub @ 00000000021b74e0] palette: 0x000000 0xf0f0f0 0xcccccc 0x999999
>> 0x3333fa 0x1111bb 0xfa3333 0xbb1111 0x33fa33 0x11bb11 0xfafa33 0xbbbb11
>> 0xfa33fa 0xbb11bb 0x33fafa 0x11bbbb

[...]

>> # VobSub index file, v7 (do not modify this line!)
>> size: 1920x1080
>> org: 0, 0
>> scale: 100%, 100%
>> alpha: 100%
>> smooth: OFF
>> fadein/out: 0, 0
>> align: OFF at LEFT TOP
>> time offset: 0
>> forced subs: OFF
>> palette: 000000, f0f0f0, cccccc, 999999, 3333fa, 1111bb, fa3333, bb1111,
>> 33fa33, 11bb11, fafa33, bbbb11, fa33fa, bb11bb, 33fafa, 11bbbb
>> custom colors: OFF, tridx: 1000, colors: 000000, 444444, 888888, cccccc
>>
> 
> Well entries are really transparent.

Could you please elaborate on that? What does make you think this in the
above report? I am not sure on how to interpret the reported data.

If the subtitles are "transparent", why do vlc and mplayer display the
characters in white color with a black outline?

I also tried ffplay right now (same code base as ffmpeg I suppose).
It does display subtitles in white + black outline characters but
their size is messed up. They are much bigger than with vlc and
mplayer (roughly twice as big). Their position is also messed up
in a way which seems consistent with the wrong size (roughly shifted
left and up by twice the amount of pixels).

So, if ffplay displays "something" in the video (let's ignore the size
issue for now), which options or filters should be used with ffmpeg to
achieve the same result?

[...]