cat *.VOB > output.vob
Now let's inspect the newly created file: we want to find what kind of stuff it contains. Use FFmpeg for that, as follows:
ffmpeg -i output.vob
For example, you might end up with something like:
Input #0, mpeg, from 'output.vob':
Duration: 01:50:40.99, start: 0.287267, bitrate: 7581 kb/s
Stream #0:0[0x1bf]: Data: dvd_nav_packet
Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first), 720x576 [SAR 64:45 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:2[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
Stream #0:3[0x89]: Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 768 kb/s
Stream #0:4[0x82]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/sMind the deep-buried streams!
Normally, while looking for streams, FFmpeg parses only few seconds of the input data as most formats have a global header there that describes everything present in the file. Unfortunately VOBs have no headers and it is likely to find movies that hold additional streams further down the VOB file.
Let FFmpeg scan it thoroughly by adding two more flags: -analyzeduration (in microseconds) and -probesize (in bytes). Honestly I'm not able to tell the difference between those options: put in there some fairly large numbers and tweak them until you are satisfied. For example:
ffmpeg -analyzeduration 100M -probesize 100M -i output.vob
And, not surprisingly, two more streams are found:
...
Stream #0:5[0x21]: Subtitle: dvd_subtitle
Stream #0:6[0x20]: Subtitle: dvd_subtitleWe are ready to pack our DVD into an .mkv/vob file. The command looks like:
ffmpeg \
-analyzeduration 100M -probesize 100M \
-i output.vob \
-map 0:1 -map 0:3 -map 0:4 -map 0:5 -map 0:6
-codec:v libx264 -crf 21 \
-codec:a libmp3lame -qscale:a 2 \
-codec:s copy \
-threads N
output.mkvThreads N is No. of CPU cores if CPU supports it.
ffmpeg -analyzeduration 100M -probesize 100M -i Aristocrats.vob -codec:v libx264 -crf 21 -codec:a libmp3lame -qscale:a 2 -codec:s copy -threads 2 AristocratsLive.vob