Qt doubts

[Mathias Puetz]

On Mon, 31 Jan 2000, you wrote:
>Hello everybody
>
>	I'm doing some research on image processing: I'm acquiring frames from
>the video-cassete through a frame grabber for post_processing. 
>
>	The fist thing I'd like to do is to watch TV on my computer. I created
>a window using the KDevelop wizard and I'm showing successive images
>using the Qt function btblt(view,0,0,&image). Well, it works but it's a
>bit slow. How could I improve the performance ?
>
>	By the way, I developed a device driver for the Data Translation DT3153
>frame grabber: it's not full-featured yeat but it's functional. Where
>could I publish it for the people who want to use it and perhaps help to
>develop it ?
Hi,

You may want to contact the video4linux people. Try

http://roadrunner.swansea.uk.linux.org/v4l.shtml

as a starter. These guys should know how to get fast
access to window buffers in X. Standard X Servers
(as of release XFRee86 3.3.6) don't allow direct
hardware access as far as I know, so with current
X it will never be as fast as M$-Win.
However there is hope, in the future XFree86 4.0
will support direct streaming support to write
directly into video ram (www.precisioninsight.com).
You may want to join the XFree86 developer mailing
list to find out more about this.

Qt bitblt should give you about the same
performance as standard XLib bitblt functions.
(If not send a bug report to Troll Tech)
It might also be an issue whether your image and
screen have the same color depth and whether your
XFree86 server accelerates the bitblt function
(and possibly depth conversion).
So it could be an issue of your graphic-card/XFree86
combo alltogether. Unless you have a Matrox card
which are very well accelerated under XFree86,
you may download a trial version of the Accelerated X
(www.xig.com) to see if this does any better (usually
it does).

Hope my hints were helpful,
Mathias

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| Mathias Puetz \__________________________________
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