[Ffmpeg-devel] Basic video understanding

Bram Biesbrouck b
Sun Oct 2 03:05:28 CEST 2005


First of all, I'd like to introduce myself to the list. I'm Bram from Belgium 
and I started writing an advanced screen capturing and screencast-creation 
program for the GNU/Linux platform. It will be published under the GPL soon I 

As I was quite new to the entire (advanced) graphics/codec/encoding/X/... 
world, I started my project with a lot of reading. I went through a bunch of 
X, Xlibs, ffmpeg and (some) mpeg documentation and then, started coding. 
Right now, I have a basic (working) program that lets the user select a 
window to capture and output the image-stream to a ffmpeg-supported format. 
As I said, still quite basic, and probably written a million times before 
(actually, I used the xvidcap project as a reference), but I wanted to lean 
it to myself.

Right now, I'm looking for a person who can give me some information and 
pointers to help me along the way. The screen capturing on my machine (not 
the fastest laptop on earth) is quite slow and I get a lot of buffer 
underruns while capturing. More yet, my understanding of the various (and 
sometimes probably quite simple) settings and inner workings of ffmpeg is too 
inadequate to move on. I ran some tests and even did some statistics, but 
some things, I just can't figure out. For example (and now, you'll probably 
laugh :)), if I feed the encoder 100 images at a frame rate of 25 fps, why 
isn't my movie always 4 seconds long? Sometimes more, sometimes less.

To sum up, I'm looking for a person that doesn't mind me bothering him/her 
with a few questions. Maybe I should just use the list for that purpose, but 
it would be a lot easier to have one or a few people that can help me; I 
would probably annoy the whole list with stupid questions. Please mail or 
reply me if you're interested.



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