When I replay some movies I encoded using DivX, and jump to various parts of the movie, the frame is not updated, instead I only see a still of the previous frame, which slowly dissolves into the part of the movie I skipped to.
It slowly recovers by only updating pixels where movement is detected in the new scene.
Is there a flag somewhere in say the Xvid or DivX encoder to turn this on or off?
(Not sure if this impacts it, but my movie is greyscale).
DivX/XviD AVIs will jump to keyframe, and must then recreate the keyframe + delta info. to reach exact location.
They will thus 'jump' forwards fairly well, but do not take kindly to being asked to jump backwards...
When set to 10x the framerate, the minimum keyframe will not be called into action too much - only in unusual circumstances, ie. when there is no break or scene change.
In other words, it would be very unusual to have 240 frames without scene break/change, but if that occurred then keyframe would hit max. and would then be inserted. Generally, there are more keyframes than that.
Anyway that is how it works - keyframes, and they might be as much as 10 seconds apart (unusual but possible).
Regards
Thanks for the reply. It clarified my understanding.
Now, I'm not sure that you will be able to help with this, but strangely enough, I want to create that effect.
That is, when I skip to a different scene, instead of calculating this frame:
Previous available keyframe + Delta
I want the following to happen:
Complete frame before 'skip' + Delta of skipped location
From this I can see the consecutive delta's emerge with a ghost-like quality. This is what I want to reproduce to help me explain how video compression works.
Quote:From this I can see the consecutive delta's emerge with a ghost-like quality
Well, not at 24fps. There's nothing ghost-like about it (hopefully :^)
It all happens very fast and is transparent to the eye...
The PC will pause, find a keyframe and then adjust to the exact spot from there, and then render the frame. You should just see the frame.
The pause is much longer travelling backwards, but almost instant going forwards.
You can go to Doom9 to learn a lot about MPEG 1/2/4 compression - and lots of other stuff!
L8R
