What is a b frame?

[TyMac]

I frames are "index frames", P frames are predictive frames but what are B frames?

[unskinnyboy]

Bi-directionally predicted frames. More info here (http://en.wikipedia.org/wiki/B-frame).

EDIT: btw, I-frames are not Index frames, but Intra frames. An I-frame is encoded without referencing any other frame except itself.

[jggimi]

I have two resources for you to take a look at.

DivX Networks produced a terrific guide that covers MPEG technology with both great explanation and terrific graphics. It includes an explanation of the various frame types in an MPEG Group Of Pictures (GOP). Since DivX 6 was released, this older guide is somewhat hidden from the casual surfer, but still available at their site. Click on http://www.divx.com/divx/create/divxpro/guides/ to find it.

We also have a sticky in our DivX Encoding archives on GOP: http://forum.doom9.org/showthread.php?s=&threadid=19436

[unskinnyboy]

@jggimi, Where exactly in this (http://www.divx.com/divx/create/divxpro/guides/) link can I find the information which TyMac had asked about? I have been looking for 5 mins now and can't find anything relevant. :|

Thanks for the second link. Quite informational.

[jggimi]

Download the "Official DivX 5.2 User Guide" from one of the links on that page. It's a .pdf (packaged in an .exe) that is available in English, French, German, and Japanese.

[unskinnyboy]

Thanks. Got it.

Rant: A single pdf of size 6.77 MB packaged in an .exe of size 6.77 MB? Weirdest install ever. :confused: