[FFmpeg-user] .vob output versus .mpg output versus .dvd output (?)

[Ronald F. Guilmette]

I've noticed that for some certian .vob input files, if I simply
pass both video and the output tracks to the output file, and if
the output file is a .mpg file, then ffmpeg will offer me the following
helpful suggestion:

    ac3 in MPEG-1 system streams is not widley supported, consider using
    the vob or the dvd muxer...

OK, so I'm considering it.  But I have no idea what the difference is.

If my output filename ends with .mpg, then ffmpeg produces an output file
which the mediainfo tool says is an MPEG-PS container.  If on the other
hand, I use ffmpeg to create an output file ending in .vob, then once again
the mediainfo tool says that this is an MPEG-PS container.  If I us ffmpeg
to create an output file ending in .dvd, then once again, the mediainfo tool
tells me that this also is an MPEG-PS container.

The audio and video tracks are simply passed in all three cases, and yet
the three output files have slightly dfferent sizes in each case.  This is
true, even though the audio and video streams are all the same in all cases,
and and even though mediainfo says that the output file is an MPEG-PS
container in all three cases.  So what are the exact differences between
.vob, .mpg, and .dvd output files and why are they all slighly different
lengths?