Quantizer ...what is it exactly ?

[crusty]

I've been ripping DVD's for about two years now and I've got some pretty good looking movies as a result.

But in all the guides I've read I've yet have to come across a proper explanation of what a Quantizer exactly is and what it does.

I already know that a lower Quantizer means better quality, and I also know that you don't need to know exactly what it is in order to make use of it, but now I want to start messing around with Xvid, and proper use of the tweaks in Xvid requires me to have a better understanding as to what a Quantizer really is and does.

I've tried the search function, but there is no good explanation as what a Quantizer really is.

Could someone please explain it in plain english to me.....
...like I'm a six year old ??:D :D

Many TIA

[jggimi]

From Doom9's glossary (highlighting mine):Quantizer

To truly understand this term you'd have to take a course in signal processing. In laymen's terms it means compression factor. The higher this value the more compressed an image is (and therefore a high quantizer means low quality picture and small size whereas low quantizers means high quality picture and larger size).http://www.doom9.org/glossary.htm#quantizer

[crusty]

Ah...ok.

Not really helpful...but thanks anyway ;)
That was the part I already figured out for myself :D

So far as I know, DivX uses different Quantizers for Individual frames but the same Quantizer within one frame, whereas Xvid also uses different Quantizers within one frame.
Is this correct or am I way off here ?

[jggimi]

Not exactly a newbie question, is it?

I believe you're probably better off asking your DivX vs. Xvid Quantizer question in the Xvid (http://forum.doom9.org/forumdisplay.php?s=&forumid=52) forum, where there will be plenty of answers available from XviD developers.