[libdc1394-devel] Re: Newbie question about transfer rates

[Johann S. <j.s...@ir...>]

Korkut Gule wrote:
> I am using Basler A602f on Fedora Core 3 with 2.6.9 kernel. i've
> downloaded and installed latest libdc,coriander and camwire. I am able
> to run the sample apps too.
> 
> putting this aside, here is my question :
> 
> My problem is about scrambled images. With using cammonitor and latest
> libdc, when i am capturing at maximum size available with 100 fps,
> images starts to get choppy and scrambled.
> 
>  I've tried to increase the size of the frame buffer as well but it
> didnt helped.
> However when i reduce frame size to 200*100 for example, no more
> problem. So with my limited knowledge, I am thinking that this is an
> issue with DMA transfer speed (like frames are overlapping before
> transfer finishes and such).
> 
> when i run camlatency, it tells me that it captured with 50~ fps
> (around this number regardles to number of frames).

Hmmm...  I can't reproduce your problems on a first try.  My tests run 
without trouble using identical settings to yours.  I have an old 
Basler A602f and I'm using Fedora Core 2 (with a slightly tweaked 
kernel 2.6.5) with libdc1394 1.0 and raw1394 0.10.1.

I think you are right about it being a DMA transfer or timing problem. 
  Getting only half the frame rate suggests that you are only 
receiving every second frame correctly.

 From past experience, I would suggest that you are pushing the limits 
when you demand maximum frame size with maximum frame rate and maximum 
integration time.  I know that it should work in theory (and it does 
work with my set-up here) but I suspect that some part of the Linux 
IEEE 1394 system is just a bit flaky when try to run too fast.  It 
might even depend on what else is running on your system.  When we 
have serious work to to we tend to back off a bit and leave a guard 
band in terms of bandwidth and shutter timing.

What is in your .conf file?

Johann

-- 
Johann Schoonees                              Research engineer
Industrial Research Limited, PO Box 2225, Auckland, New Zealand
Phone +64 9 9203679 Fax +64 9 3028106 http://www.is.irl.cri.nz/
Camwire's home:  http://kauri.auck.irl.cri.nz/~johanns/camwire/