Maybe there's a simple answer for this, but when looking at the files on a DVD (IFOs, VOBs,etc), is there a way to easily determine the longest/main track? I'm trying to automate the process of finding the main movie track on a DVD and am running into issues.

I thought this could be done by finding the BIGGEST track (look through VTS_XX_N.VOB files, where XX is the track number, and find the track with the largest filesize (sum sizes of VOB files for that track)), but apparently that isn't correct. One DVD had track 7 as the largest track (by my method), but mencoder didn't produce the correct output with this track, but worked with track 9 instead.

Am I missing something?

EDIT: I've heard of the utility 'lsdvd' for getting track information, but I was hoping to avoid compiling this, and use a basic method instead (ie: what I tried above). Does anyone have any idea WHY my idea didn't work?