[DCP-o-matic] Little help need → dvd to dcp

Hi… …not the first time I do that but today I fail… DCP-O-Matic 2.10.5 git 61b5d4ad8 on Ubuntu 14.04. I have a dvd to convert to dcp. First thing I did was concatenate the 4 vob into one file : cat VTS_01_1.VOB VTS_01_2.VOB VTS_01_3.VOB VTS_01_4.VOB | ffmpeg -i - brialy.mp4 Then I use some personal script to get some kind of 5.1 sound → file becomes brialy_51.mov Now in DCP-o-Matic conversion always stops @ same number of images ( about 4500 ). There's some warning in log @ line 2407 FFmpeg: Warning: data is not aligned! This can lead to a speedloss Files attached are log, ffprobe.log andmy script for 5.1 upmix. I suspect more has to be done regarding « concatenate » the vob into one single. Any hints / help welcome. Best regards, Gerald