The size of a .VOB container file is, by definition of the DVD specification, limited to 1 GByte (1048 MB).

If we need a file that contains a whole movie, then we need to convert these files to another container (e.g. xvid, MKV, plain MPEG etc.), e.g. by using ffmpeg:

ffmpeg -i snatch_1.vob -f avi -vcodec mpeg4 -b 800k -g 300 -bf 2 -acodec libmp3lame -ab 128k snatch.avi
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Concatenating video files can only be done with some formats (e.g. MPEG).