[Ffmpeg-devel] ScreenKast exporting

Bram Biesbrouck b
Mon Aug 28 15:51:11 CEST 2006

Hi all,

I'm the creator and main developer of the ScreenKast program and I'm looking 
for some help regarding my export routines (which are using the ffmpeg 
library). Quick introduction: ScreenKast is a Linux-program that can record 
movies from your screen, edit, export and publish them (on captorials.com).

Ok, so much for the introduction and slightly spammy advertisement, to the 
point now.
The thing is: ScreenKast records and saves it's data to a custom (free/open) 
file format (largely based and extended from the vncrec format). As said, I 
use ffmpeg to export to other video formats, but my knowledge of the ffmpeg 
API is too shallow, and I'd like to optimize the export-routines. So, I'm 
looking for some ffmpeg-gurus that are prepared to help me out.

Here's the concept: the recording is stored as zlib-compressed rect-updates, 
that get decompressed on the fly and drawn to an OpenGL canvas, together with 
text-balloons, commentboxes, etc. Currently, the ffmpeg export-code grabs 
that (entire) OpenGL canvas every time something changes, but this is too 
costly, because often, only small areas get updated.
So I'd like to switch to exporting only the changed area's, perhaps using 
variable bitrates, but like I said, my ffmpeg knowledge isn't good enough 
(spent the whole day on it, but didn't get far) and I don't really have lots 
of time to spare to master it.

Any of you guys that want to help me out?
I attached the ffmpeg-exporter class for a reference, it's largely based on 

The entire backend library can be found at:

For the interested, the gui and packages at:


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