A little confused on your "workflow" of what you started with (PC, MAC, Tablet) to get it on your tablet..
DVDs like CDs need a ripping program, with DVDs ripping program will result in a MPEG2 DVD compliant video file ending with .vob
Not sure if Android natively plays .vob so I suspect the program you was using was converting the .vob to something like .mp4 which is playable by Android..
I do all of my work for a PC.
Starting with a PC with DVD drive, you need a ripping program, one I use a lot is DVD Decrypter (free) but DVD Decrypter is no longer being developed so it may not Decrypt/rip some DVDs..
That gets me to .vob..
To convert .vob to other file formats I use a program called WM Converter which was bundled with WM Recorder Version 14 (a audio/video stream capture program). Sadly, it looks like the company that was behind those programs no longer exists (was bought by another company) and the new companies versions are more like Malware.. Fortunately for myself I had saved a copy of the WM Recorder install program..
Another free software you could use is Handbrake, the only issue I have found with newer versions of Handbrake is you do not have much choice in what the final file format is.. They have dropped support for a lot of older file formats.
Some conversion softwares designed for exporting to portable devices like cellphones and tablets may have presets which reduces bit rates to make for smaller file sizes, that often will reduce the final output quality but result in a much smaller file for portable devices with limited storage space.
A pretty good source for A/V software is
WWW.VIDEOHELP.COMMost of the software they have posted is fairly well checked and vetted to ensure they are not hosting virus laden software.
They also have a forum dedicated to all things A/V..