Sometimes, Mpeg-4 (Divx/Xvid) doesn't compare mpeg-2. The major difference between the two is crispness. Mpeg-4 has more of a smooth, almost platic-y look. The very best Divx/Xvid encodes still don't compare to their DVD counterparts. They can come close though, and coupled with the fact they're a lot smaller than DVD's in terms of size, you're willing to live with the quality loss.
Why DivX has worse quality than DVD? The answer is very simple. DVD format (actually MPEG-2) has many distortions usually ignored by human eye. During re-compression process (DVD to DivX) DivX codec uses already distorted video signal. As a result of this fact, DivX introduces additional distortion to the original (already distorted) movie. That's why psycho-visual enhancements are visible as annoying divx video artifacts. We could say more about power of DivX codec while comparing 2 movies encoded from really original source. For example TV to DVD, and TV to DivX. But now, many movies available in Internet were ripped from DVD. So these divx movies were compressed 2 times with 2 steps of quality loss: with MPEG-2, and then with MPEG-4.
Another reason why mpeg-4 is so popular is that there are a lot of people that use only divx for watching popular movies and I don't think they can really tell the difference between DVD and Divx. To each their own.
Last update: 07:21 PM Sunday, February 26, 2006