Transparent subtitle outlines (IDX/SUB) upon conversion to XSUB become solid, and colors become b&w

[userid99]

Summary of the bug:

Transparent subtitle outlines (IDX/SUB) upon conversion to XSUB become solid, and colors become black and white.

How to reproduce:

ffmpeg -v 9 -loglevel 99 -report -i transpidx.avi -i t

ranspidx.idx -vcodec copy -an transpxsub.avi

[userid99]

input idx file

[userid99]

input sub file

[Carl Eugen Hoyos]

Is this a regression?

[userid99]

Replying to cehoyos:

Is this a regression?

No

[Carl Eugen Hoyos]

For future tickets:
Please always provide a command line that allows to reproduce the problem including its complete, uncut console output.
Please do not provide output files unless a developer is unable to reproduce and asks for the output file.
Please do not attach more input files than necessary, it imo only leads to confusion.

This is currently a bug because the intended warning in the code is not shown, this will be fixed soon.

$ ffmpeg -f lavfi -i testsrc -i transpidx.idx -scodec xsub -t 14 out.avi
ffmpeg version N-59400-g8335016 Copyright (c) 2000-2013 the FFmpeg developers
  built on Dec 28 2013 22:21:53 with gcc 4.3 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      52. 59.100 / 52. 59.100
  libavcodec     55. 46.100 / 55. 46.100
  libavformat    55. 22.100 / 55. 22.100
  libavdevice    55.  5.102 / 55.  5.102
  libavfilter     4.  0.103 /  4.  0.103
  libswscale      2.  5.101 /  2.  5.101
  libswresample   0. 17.104 /  0. 17.104
  libpostproc    52.  3.100 / 52.  3.100
Input #0, lavfi, from 'testsrc':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
Input #1, vobsub, from 'transpidx.idx':
  Duration: N/A, bitrate: N/A
    Stream #1:0[0x0](de): Subtitle: dvd_subtitle, 640x480 (default)
Output #0, avi, to 'out.avi':
  Metadata:
    ISFT            : Lavf55.22.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 25 tbn, 25 tbc
    Stream #0:1(de): Subtitle: xsub (DXSB / 0x42535844), 640x480 (default)
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> mpeg4)
  Stream #1:0 -> #0:1 (dvdsub -> xsub)
Press [q] to stop, [?] for help
[avi @ 0x91f31e0] Encoder did not produce proper pts, making some up.
frame=  350 fps=206 q=2.6 Lsize=     559kB time=00:00:14.00 bitrate= 326.9kbi

The following work as expected
$ ffmpeg -f lavfi -i testsrc -i transpidx.idx -scodec dvbsub -t 14 out.ts
$ ffmpeg -f lavfi -i testsrc -i transpidx.idx -scodec dvdsub -t 14 out.vob
although the last frames look different with ffplay indicating a possible problem.

[Carl Eugen Hoyos]

A warning is now - since de40905f - shown (as originally intended) if the transparency gets messed up when encoding xsub.

[Elon Musk]

xsub, with tag DXSB does not support alpha. It knows only about background which is always transparent and foreground which is not transparent.
DXSA on other hand have support for alpha, but xsub encoder does not support it.