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

[Paul B Mahol]

On 8/30/13, Thierry Lelegard <thierry at lelegard.fr> wrote:
>> 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.

Actually looking at source code those logs does not output alpha bytes at all.

>
> 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?
>
> [...]
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