[FFmpeg-trac] #7183(undetermined:new): Concat very slow with dvd_subtitles

[FFmpeg]

#7183: Concat very slow with dvd_subtitles
-------------------------------------+-------------------------------------
             Reporter:  oerg866      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 FFMPEG will process concatenation of vob files with subtitles agonizingly
 slowly (less than real time speed on my i9-7900x with stream copy!) and
 the progress display is erratic.


 How to reproduce:

 {{{
 ffmpeg f concat -safe 0 -i list.txt -vcodec copy -acodec pcm_s16be -scodec
 copy mux.vob
 }}}

 list.txt contains several vob files with MPEG2 video, LPCM audio and
 subtitles.

 Separate concat with several files that have video, audio and subtitles
 and then remuxing to a final output works infinitely faster, like so:


 {{{
 ffmpeg -f concat -safe 0 -i list.txt -vcodec copy -acodec pcm_s16be
 mux1.vob
 ffmpeg -f concat -safe 0 -i list.txt -vn -an -scodec copy mux2.vob
 ffmpeg -i mux1.vob -i mux2.vob -map 0:v -map 0:a -map 1:s -vcodec copy
 -acodec pcm_s16be -scodec copy mux.vob
 }}}

 HOWEVER, this breaks subtitle timing (they play about two seconds too
 early. Also potential bug?)

 Below is a sample of ffmpeg's console output with the buggy command.

 {{{
 C:\OUTPUT>ffmpeg -f concat -safe 0 -i list.txt -vcodec copy -acodec
 pcm_s16be -scodec copy mux.vob
 ffmpeg version N-86691-gc885356 Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 7.1.0 (GCC)
   configuration: --enable-gpl --enable-version3 --enable-cuda --enable-
 cuvid --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-nvenc
 --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
 --enable-gnutls --enable-iconv --enable-libass --enable-libbluray
 --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme
 --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame
 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264
 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsnappy
 --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame
 --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-
 libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-
 libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma
 --enable-zlib
   libavutil      55. 67.100 / 55. 67.100
   libavcodec     57.100.103 / 57.100.103
   libavformat    57. 75.100 / 57. 75.100
   libavdevice    57.  7.100 / 57.  7.100
   libavfilter     6. 94.100 /  6. 94.100
   libswscale      4.  7.101 /  4.  7.101
   libswresample   2.  8.100 /  2.  8.100
   libpostproc    54.  6.100 / 54.  6.100
 Guessed Channel Layout for Input Stream #0.1 : stereo
 Input #0, concat, from 'list.txt':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, bottom first),
 720x576 [SAR 16:15 DAR 4:3], 25 fps, 25 tbr, 90k tbn, 90k tbc
     Stream #0:1: Audio: pcm_dvd, 48000 Hz, stereo, s16, 1536 kb/s
     Stream #0:2: Subtitle: dvd_subtitle
 File 'mux.vob' already exists. Overwrite ? [y/N] y
 Stream mapping:
   Stream #0:0 -> #0:0 (copy)
   Stream #0:1 -> #0:1 (pcm_dvd (native) -> pcm_s16be (native))
   Stream #0:2 -> #0:2 (copy)
 Press [q] to stop, [?] for help
 [svcd @ 0000000004928b60] VBV buffer size not set, using default size of
 130KB
 If you want the mpeg file to be compliant to some specification
 Like DVD, VCD or others, make sure you set the correct buffer size
 Output #0, svcd, to 'mux.vob':
   Metadata:
     encoder         : Lavf57.75.100
     Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, bottom first),
 720x576 [SAR 16:15 DAR 4:3], q=2-31, 25 fps, 25 tbr, 90k tbn, 90k tbc
     Stream #0:1: Audio: pcm_s16be, 48000 Hz, stereo, s16, 1536 kb/s
     Metadata:
       encoder         : Lavc57.100.103 pcm_s16be
     Stream #0:2: Subtitle: dvd_subtitle
 frame= 2003 fps=159 q=-1.0 size=     944kB time=00:01:20.04 bitrate=
 96.6kbits/s speed=6.34x
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7183>
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