"Kenneth" <kdw### [at] gmailcom> wrote:

> Chuck wrote:
> > Key frames - I know what a keyframe is (perhaps), just not how to identify
> > them in a video editor. I'm not sure but don't think ProShow gold will
> > identify them.
>
> Actually, VirtualDub itself shows which frames are keyframes ("I-frames"), in
> the little info bar a the bottom of the playback window. (When a group of
> POV-Ray animation images are first loaded into VD, they start off as all
> keyframes.)
>
> Essentially, video encoding is more efficient (smaller file size) when it uses
> fewer actual keyframes for the final video. The 'in-between' frames (called
> "P-frames" and "B-frames") are actually composed of only the *differences*
> between an I-frame and its surrounding frames-- with very little quality loss.
> Put very simply, those differences are made up of small 8X8- or 16X16-pixel
> blocks ("macroblocks".) The encoder tries to find 'matching' macroblocks among
> the adjacent frames (even if those blocks have moved during the frame changes.)
> It re-uses those blocks when it can, in the adjacent P-frames and B-frames. So
> the P's and B's contain much less 'new' information than would otherwise be the
> case.
>
> For an ALL-keyframe video, a crude analogy would be as if each individual frame
> is encoded as an individual and separate JPEG image. While that's possible to do
> (the "motion-JPEG" format does this, as far as I understand), it's not very
> efficient-- the video decoder has to decode ALL the macroblocks in each
> individual frame on-the-fly.

I appreciate the key-frame info. That raises a number of questions but would
stray from PovRay related topics so will do some private reading.

Another animation was created with the idea of generating 25 frames per second.
As expected the resulting animation is MUCH more smooth. Unfortunately I cannot
reproduce the original animation which started this thread and the current
attempts, while smooth, are not very interesting. I may upload one of them to
demonstrate the improvements anyway.

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