Comments on: graps : capture OpenGL Frames

By: Doug

Doug — Wed, 23 Sep 2009 23:50:44 +0000

what would be really cool is a way to direct the video stream out a 1394 port in DV format. I’m thinking screencasting here and capturing the video on a HD camcorder. My Sony HDR-HC5 only captures from a DV formatted Fireware/i.Link/IEEE1394 link.

By: Doug

Doug — Sun, 30 Mar 2008 23:31:49 +0000

Correction to the above entry: By setting the capture frame size to the exact size of the Java3D frame, the recording was clear as a bell. Sweet.

By: Doug

Doug — Sun, 30 Mar 2008 18:28:38 +0000

I was hopeful after capturing glxgears worked but when I try to capture from a Java3D window all I get is static. I can capture using glxdump but the performance is lacking and there are slight amounts of jumping to the video.

Has anybody and ideas about this or even seen this scenario( native GL app works, Java3D does not )?

By: Can Kavaklioglu

Can Kavaklioglu — Mon, 03 Dec 2007 12:20:16 +0000

Hello,

I will be using the flip function. I guess I found a bug. If the

j2 = image_height - j;

line is left as it is, the top row of the image does not get flipped. I think it should be

j2 = image_height - j -1;

At least this is the case in my code.

Thanks again.
Can Kavaklioglu

By: Can Kavakl?o?lu

Can Kavakl?o?lu — Sun, 25 Nov 2007 09:54:54 +0000

Many thanks for great explanation. Was looking for this trick for quite a time now.

One note, in the readme file it says the preferences file is called “~/grapsrc”. But the code is looking for “~/.grapsrc” with the dot . I guess you need to fix one of them.

I have used parts of your code and put a reference to your page from this project’s at:

http://robot.cmpe.boun.edu.tr/~ckavaklioglu/usarlinuxhook

Thanks again.
Can Kavaklioglu

By: Mineral

Mineral — Fri, 07 Sep 2007 01:41:41 +0000

Project is dead? I found similar project: wiki.vislab.usyd.edu.au/moinwiki/VideoCreationGuide (file glxdump.c), but your is more cool

Idea grab glXSwapBuffers is great! It can’t skip any frame! Low fps, but all frames will go via graps!

I was need write screensaver, but uncompressed images fast wasted my hdd… So I patched this for direct video encoding

At first, I found bug, see “grap.width*grap.width*3″ at sources
Next, file open, which write images, moved to “graps_firsttime”, and changed to constant name, so all frames go to single file. And removed header writing + file closing. As result I have single file of raw RGB24 video

Need patch? Can send to you.

Make fifo:
$ mkfifo videopipe
where “videopipe” - is file, which white graps

Then start video encoder, like this:
$ mencoder videopipe -rawvideo w=1000:h=700:fps=25:format=RGB24 -demuxer rawvideo -o output.avi -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=800

and start any openGL software, for example, screensaver:
$ bash run.sh kxsrun flyingtoasters — -geometry 1000×700

When openGL application stopped, video encoding will stop too. Enjoy

Very important make similar sizes at mencoder and at window size.

By: kopos

kopos — Tue, 30 Nov 1999 00:00:00 +0000

nice…
so its an alternative to fraps?! cool how does it compare in performance wrt fraps?

By: smr

smr — Tue, 30 Nov 1999 00:00:00 +0000

vs fraps
@kopos
i never tried fraps. but i guess nowhere close to fraps. in graps i’m using a hack to make it work. the point is that its small and it works.

By: chetan

chetan — Tue, 30 Nov 1999 00:00:00 +0000

images created upside down
Hi,

I tried using graps , but the images formed are upside-down !!!
Where may be the fault ?

By: smr

smr — Tue, 30 Nov 1999 00:00:00 +0000

Re:
Yeah… by default graps creates upside down images. coz thats what glReadPixel gives. Correcting this in realtime might cause fps to drop a little.
A flag can be enabled in graps config file to do this correction in realtime.