bvop, pvop, nvop

[Anonoumus]

What do bvop, pvop, nvop mean? Are these special to any particular codec? Can you change them by re-encoding in Virtualdub using the free divx codec or xvid?

[jagabo]

P is for Predicted frame, a frame that only contains changes from a prior frame. B is for Birectional encoded frame, a frame that only contains differences from an earlier and/or later frame. N is for Null frame, an frame that doesn't contain a frame (just a place holder). You didn't ask but I (Intra) frames are complete images, much like a JPEG picture. More information here:

http://en.wikipedia.org/wiki/MPEG-2

Reencoding with Divx or any other MPEG family encoder will generate all new I, B, P and N frames. You'll lose a little quality by reencoding though.

[Anonoumus]

Thanks jagabo. I understand the 1st letter significance but what does VOP stand for?

[JimmyS]

Here is cut from this PDF of a presentation that sheds some light on the term VOP (video object plane)

http://www.visicast.co.uk/members/milestones/ViSiCAST-Deliverable-D1-4.pdf

1.2.2 The MPEG-4 Video Encoder configuration file
The MPEG-4 Video Encoder installation kit provides an example configuration file. The user has to
edit this file to obtain appropriate results in term of compression ratio vs video quality. Before
describing the encoding parameters, let us recall some basic principles of MPEG-4 Video encoding.
The video is composed of frames called VOPs (Video Object Planes). MPEG-4 offers 3 ways to
encode a VOP (Figure 2) :
• VOPs of type I (Intra) are encoded independently from other VOPs.
• VOPs of type P (Predictive) are predicted by motion compensation from the I-VOP.
• VOPs of type B (Bidirectional Interpolated) are predicted from two references, namely a future one
and a past one. These references can be P-VOP or I-VOP.


Looks like a more technical term for what we have been just reffering to as frames.

[Anonoumus]

A VOP is a frame!? Wow, I would have never guessed that. Thanks JimmyS and jagabo.

[M Bruner]

I VOP, you VOP and they VOP... ;D