Oliver Neukum wrote:
> > Are you using CF too, or an other disk in PIO mode ?
> >
> > PIO mode access will generate quite some CPU load in kernel mode,
> > it seems that the kernel doesn't serve the USB stuff fast enough.
> > In my application I don't care if some frames get lost or damaged.
> > But the halting of the camera is not acceptable.
>
> Could you try enabling interrupts in the IDE code?
> This can be done with 'hdparm'. Please be cautious and remount
> your disks read only while you test this.
Hi Oliver,
I already tried that a long time ago: it doesn't make any difference:
the camera just goes dead when there is more than say 20-50 disk sectors
are accessed at once. Even accessing a single sector but in combination
with the kernel's read-ahead can be fatal.
Also (at least in my case) the *userspace* cpu-load does not have any
influence on the problem. I can create an artificial load of 20 and there
is no problem: the camera keeps working fine. But just accessing a bit
too many disk sectors (on CF in my case) kills the camera immediately.
Apparently the webcam driver or USB stack is extremely sensitive to
being serviced on time.
The main reason for using the Philips PCVC740K webcam is its very good
image quality and excellent working Auto Gain Control. If you know
about other (non-philips based) USB camera's that can do the same I'm
very interested.
I don't mind dropped or garbled frames at all. But the "dying" camera
is fatal. This problem is driving me nuts. Any help or other suggestions
are appreciated !
greetings,
Rob van Nieuwkerk
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