[Kdenlive-devel] last CVS

[Jason Wood]

On Monday 18 Nov 2002 3:22 pm, Rolf Dubitzky wrote:
> Anyway, this reminds me of something very important we did not yet talk
> about concerning the communication part. We nned to tansport all kinds of
> snapshots from the effect engine to the GUI. A Track in the timeline should
> contain a very small snapshot of the first and last frame at least, and it
> would be nice to have the first frame of a clip in the file list too. How
> should we do that?
>
> We cannot have tenth of embeded XWindows.
> We probably don't want to push the images through a socket.
> We could use a pipe in the filesystem or shared memory.
> Shared mem is probably much faster but won't work if GUI and effect engine
> are on different systems.

I agree that we can't have lots and lots of embedded x-windows :-) But I was 
contemplating perhaps one window, which would act like a tooltip for when you 
are resizing - it would pop up when you start a resize, showing you the frame 
that you are on, and then vanish once the resize has finished.

Here are some thoughts on the thumbnail issue :

For the most part, thumbails will remain static on all but one clips. In other 
words, the only time that we need to recalculate thumbnail images is when we 
add a new clip to the timeline, or resize a clip (and hence, change the frame 
that should be displayed in the thumbnail.) It is possible that we would have 
to re-create all of the thumbnails if we zoom in or out, but this would only 
affect us if we drag thumbnails across the entire length of the clip.

So thumbnails are easy to cache - we will not need to constantly recalculate 
them.

If we consider the current size of the video tracks (they are 50 pixels high), 
then to get a correct aspect ratio, we have 66*50 = 3300 pixels to transfer; 
at 32bit color, that would be around 13K per snapshot.

It should be an asyncronous operation - the GUI should not wait around for the 
thumbnails to arrive.

I'm unsure as to how much effect throwing snapshots through pipe will have -  
if we consider 13K per snapshot, with 2 thumbnails per clip, then we would 
need approximately 38000 clips on the timeline to require 1 meg of data 
transfer.

I realise I haven't actually said which way I would prefer to do things yet, 
I'm still deciding :-)

Cheers,
Jason

-- 
Jason Wood
Homepage : www.uchian.pwp.blueyonder.co.uk