[lug] Movie project

[D. Stimits]

Warren Sanders wrote:
> 
> I am looking for what might be available for simply recording a selected
> desktop such as screen 2 on KDE.  What I plan to do is record sound off
> a phone conference and merge it with the demonstration the conference is
> holding without sound via the web using something similar to
> Netmeeting.  They do application sharing and whiteboard stuff in the
> demonstration.  What I plan to do is run rdesktop to a windows box that
> will have this app. share running.  I'd like to be able to record this
> desktop to a low quality video, then later merge the phone conference to
> the movie and ultimately write it to CD.
> 
> Anyone know of anything that can do this or come close to it?  What
> might I be looking at as far as file size also?  Some of these
> conferences may last up to 6 hours with several breaks.  I'd also want
> to be able to switch to other desktops without interrupting the
> recording and not have the recording follow me; I want it to stay with
> the desktop 2.

Can't say I know of an answer, but I'm interested in finding out more
about the whiteboard stuff.

On top of that, maybe I can offer some clues (which someone else can
give you the real details of probably). I think most movies are in the
30 frame per second rate, but you can use the same picture for up to
maybe 3 frames (losing quality at 3, but I'd guess 2 of the same thing
in a row would not be that bad). Now the fun part would be figuring out
a compression scheme, if you recorded 10 frames per second, and each
frame had something like 24 bit, 600x800, you're looking at uncompressed
about 600 * 800 * 3 bytes, you're looking at about the size of a 1.44 MB
floppy each frame. Some software is really nice in that it lets you do a
key frame interpolation, so you still take only one snapshot every tenth
of a second, and it fills it with the missing 2 between each, but it
figures out what has changed and makes intermediate versions so they are
not the same thing (unfortunately, I think that is easier if one has 3D
objects that are each being moved, rather than just a pure pixmap
image). I have some software for animation that does basically all of
that, but I've never delved into its more advanced features. Some of the
formats like MP3 have a lot of design simply around the ability to
compress properly, and in some cases, deal with dropped frames in a way
similar to the interpolation. If you managed to take a snapshot 10 times
per second (or less if you had something to do interpolation) you could
eventually turn it into a movie with a lot of work, but also consider
that most hard drives couldn't save that much data over a period of
time, and even the raw number of small files would be a problem, some
scheme would be required to maybe tar 100 frames and compress...it would
be a fun project (not meant sarcastically, it really would be fun), and
you'd likely have to start by patching your kernel with preemption and
low latency patches (unless you run SMP, then you merely add the low
latency patch). Although I sound skeptical, I have little doubt that
someone has something up their sleeve to do at least parts of this
already, it's just too popular of a technology to not have the pieces,
even if nobody has put them together yet.

D. Stimits, stimits at idcomm.com