Subtitle (hdmv_pgs_subtitle) conversion fails

[bakhshian]

I need to convert the format of the subtitle stream of a movie so my device can play it.
Here is the list of all existing streams :

    Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x816 [SAR 1:1 DAR 40:17], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Stream #0:1(eng): Audio: dts (DTS), 48000 Hz, 5.1(side), s16, 1536 kb/s (default)
    Metadata:
      title           : 3/2+1
    Stream #0:2(eng): Subtitle: hdmv_pgs_subtitle (default)
    Stream #0:3(ger): Subtitle: hdmv_pgs_subtitle
    Stream #0:4(ger): Subtitle: hdmv_pgs_subtitle
    Stream #0:5(ger): Subtitle: hdmv_pgs_subtitle
    Stream #0:6(ger): Subtitle: hdmv_pgs_subtitle

I want to keep only the English subtitle and convert it too. The available codecs are :

> ffmpeg -codecs | grep sub
 DES    ass             Advanced SubStation Alpha subtitle
 DES    dvbsub          DVB subtitles
 DES    dvdsub          DVD subtitles
 D S    pgssub          HDMV Presentation Graphic Stream subtitles
 DES    srt             SubRip subtitle
 DES    xsub            DivX subtitles (XSUB)

I choose dvdsub as the new format and try to run ffmpeg command with the following arguments :

ffmpeg -i in.mkv -scodec dvdsub -vcodec copy -acodec copy out.mkv

It starts running, but after a while ( I think when it reaches the first frame with subtitle ) crashes. Here you can see the messages :

Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
  Stream #0:2 -> #0:2 (pgssub -> dvdsub)
Press [q] to stop, [?] for help
Subtitle encoding failed1.0 size=  182919kB time=00:00:00.00 bitrate=   0.0kbits/s 

The interesting point is that ffplay and mplayer both can play the input file and they show the subtitle properly.

Here is the output of ffmpeg -version command :

ffmpeg version 0.10.2-4:0.10.2-0ubuntu0jon1~oneiric1
built on Mar 18 2012 11:07:55 with gcc 4.6.1
configuration: --extra-version='4:0.10.2-0ubuntu0jon1~oneiric1' --arch=amd64 --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu --disable-stripping --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-runtime-cpudetect --enable-libfreetype --enable-vaapi --enable-frei0r --enable-gpl --enable-postproc --enable-x11grab --enable-librtmp --enable-libvo-aacenc --enable-version3 --enable-libvo-amrwbenc --enable-version3 --enable-libdc1394 --shlibdir=/usr/lib/x86_64-linux-gnu --enable-shared --disable-static
libavutil      51. 35.100 / 51. 35.100
libavcodec     53. 61.100 / 53. 61.100
libavformat    53. 32.100 / 53. 32.100
libavdevice    53.  4.100 / 53.  4.100
libavfilter     2. 61.100 /  2. 61.100
libswscale      2.  1.100 /  2.  1.100
libswresample   0.  6.100 /  0.  6.100
libpostproc    52.  0.100 / 52.  0.100

[cehoyos]

Please provide backtrace etc. for crashes, as explained on http://ffmpeg.org/bugreports.html

[bakhshian]

the report created by ffmpeg

[bakhshian]

Replying to cehoyos:

Please provide backtrace etc. for crashes, as explained on http://ffmpeg.org/bugreports.html

I attached the report file to the ticket. Would you please let me know if it is enough or something else is needed ?

[cehoyos]

In your original report you describe a "crash", the report you provided does not show any indication for a crash. Please clarify.

[bakhshian]

Replying to cehoyos:

In your original report you describe a "crash", the report you provided does not show any indication for a crash. Please clarify.

It exits after an error occurs. It prints the error message : Subtitle encoding failed. As you can see in the attached log file, it happens while converting the 4308 frame of the movie and the conversion fails. I am not sure if I can call it a crash or not.

[cehoyos]

Replying to bakhshian:

It exits after an error occurs. It prints the error message : Subtitle encoding failed. As you can see in the attached log file, it happens while converting the 4308 frame of the movie and the conversion fails. I am not sure if I can call it a crash or not.

It is not a crash.

Is the problem also reproducible if you cut the sample with dd (to make it short enough to attach / upload)?

[bakhshian]

Replying to cehoyos:

Replying to bakhshian:

It exits after an error occurs. It prints the error message : Subtitle encoding failed. As you can see in the attached log file, it happens while converting the 4308 frame of the movie and the conversion fails. I am not sure if I can call it a crash or not.

It is not a crash.

Is the problem also reproducible if you cut the sample with dd (to make it short enough to attach / upload)?

I cut 3minutes of the movie and converted its video and audio formats to make it small enough to upload. The same error occurs while trying to convert the subtitle codec. The file can be found under  ftp://upload.ffmpeg.org/incoming/. Its name is SCodecConversionFailsSample.mkv. There is another txt file with the same name describing the problem.

[bakhshian]

hi again,

was my problem re-producible by the given file ? or is it just a problem from my side ?

please help

[cehoyos]

Sorry for the delay, the issue is reproducible: encode_dvd_subtitles() is called with h->num_rects == 0

[cehoyos]

A possibly related bug is the null-pointer dereference in line 136 of xsubenc.c in xsub_encode():
$ ffmpeg -i SCodecConversionFailsSample.mkv -scodec xsub -f null -

[bakhshian]

Replying to cehoyos:

A possibly related bug is the null-pointer dereference in line 136 of xsubenc.c in xsub_encode():
$ ffmpeg -i SCodecConversionFailsSample.mkv -scodec xsub -f null -

Converting to xsub using '-f null' option, I get a more descriptive message :

[xsub @ 0x2026680] No more than 4 subtitle colors supported (256 found.)
[xsub @ 0x2026680] Only single rects supported (0 in subtitle.)

[Cigaes]

I would like to access the sample, to see if my recent patches in that area are enough to solve the problem.

[cehoyos]

Sample uploaded to samples/ffmpeg-bugs/trac/ticket1277

[Cigaes]

Thanks Carl Eugen.

This patch fixes the failure:
http://ffmpeg.org/pipermail/ffmpeg-devel/2012-August/129069.html

The resulting encoded subtile has completely wrong colors, but the following patch fixes it, and gives IMHO a very decent result given the limitations of the dvdsub format:
http://ffmpeg.org/pipermail/ffmpeg-devel/2012-August/129070.html

The resulting subtitle is still huge, though, and slightly differently so between MPlayer and ffplay, but that is definitely an improvement. See the attached screenshots.

I'll try to look into the size matter.

[Cigaes]

Screenshot of ffplay after encoding with the "ffmpeg: add an option to fix subtitles durations" patch

[Cigaes]

Screenshot of mplayer after encoding with the "ffmpeg: add an option to fix subtitles durations" patch

[Cigaes]

Screenshot of ffplay after encoding with the "dvdsubenc: make it usable for transcoding" patch

[Cigaes]

Screenshot of mplayer after encoding with the "dvdsubenc: make it usable for transcoding" patch

[Cigaes]

I believe the following patch series:
http://ffmpeg.org/pipermail/ffmpeg-devel/2012-August/129111.html
fixes all the issues. You need to add -fix_sub_duration to the input and either -analyzeduration 20E6 to the input or -s:s 1920x1080 to the output.
The subtitles will stay huge in certain players, but it works at least in MPlayer.

[Cigaes]

Screenshot of mplayer after encoding with the patch series suggested in comment #15

[bakhshian]

Thank you so much. Would you please let me know how can I apply this patch or when the new official release including these changes will be available ?

[cehoyos]

If you cannot apply the latest series of this patch - http://ffmpeg.org/pipermail/ffmpeg-devel/2012-August/129212.html - please wait until the patch is applied and the ticket closed.

[Cigaes]

The patch series was just pushed to the current Git head. Please close the bug if it fixes things for you.

[Sharkhunter]

Does these patches fix srt -> dvdsub as well? Previous adding srt -> dvdsub worked but crashed the video during playback (crash on first subtitle frame) now (at least Zeranoes win build" carshes completly without a trace...

[Cigaes]

No, it does not. srt is text, dvdsub is bitmap: converting one to the other would require rendering the text, using fonts and layout engine.

[Sharkhunter]

So burning srt to dvdsub will simply never work?

[Cigaes]

Not never, but nobody is currently working on it, and it will certainly have to wait for a proper API for decoded text subtitles.

Note that spumux can do it.

[Sharkhunter]

Mencoder can as well but it has other issues. It would just be nice to avoid using 3 or 4 programs just to get it working...

[Cigaes]

AFAIK, no, mencoder can not, unless you expressed your problem incorrectly. Also, remember this is an issue tracker, and this issue is, I hope, fixed.

[Sharkhunter]

Sure I just asked.

[cehoyos]

Replying to Sharkhunter:

Previous adding srt -> dvdsub worked but crashed the video during playback (crash on first subtitle frame) now (at least Zeranoes win build" carshes completly without a trace...

Did you report this?
Even if no backtrace is possible, complete, uncut console output missing.

[Sharkhunter]

Have now http://ffmpeg.org/trac/ffmpeg/ticket/1661