If you ripped the DVD (say, using AnyDVD) without re-encoding then it will playback identically to a DVD player (quality will be the same) – that’s what Tony is saying. IOW, to put it another way, there should be NO jaggies when played by the WD TV Live unit.
If you re-encoded the file using Handbrake to an MKV container then the quality can vary depending on what preset or settings you used. If you use the High Profile preset, for example, you should see no difference in quality, but if you used the iPhone preset you would.
All of my MKV files are made with Handbrake using the High Profile preset – and whether a blu-ray or a DVD the quality is exactly the same as the original disc.