Re: [libdc1394-devel] To investigate video1394 in kernel module

[Kiran K. <kir...@gm...>]

Hi Daniel,

Thanks for responding....:)

I am currently swimming through the ocean of the ohci1394 iso_tasklet
interrupt mechanism. I suspected ohci_iso_recv_program would be the
candidate who interrupts Video1394....but so far unlucky.:(

Ok, let me tell you some details.

Going through some messages in libraw forum, I came to know that
kernel is holding the packets (for almost 8ms in my case) and
interrupts the user space application only after some delay (8ms)...I
am trying to determine whether that is true.

The reason for this digging is, I have a setup where Windows
outperfroms Linux...in  capture time. The Windows posts pulse at 8ms
compared to theoritical 6 ms.

Unfortunately Linux gives me 14ms and I am baffled to see that.

Just for ur information, in the setup, I am using 2 Basler A602f
cameras with external trigger.  The setup has Linux Kernel 2.6.19.2
(earlier tried with 2.6.15), libraw1394-1.2.1, libdc1394 2.0 rc3 and
rc4. gcc 4.0.3, Distribution Ubuntu 6.06.

The aperture is close to 600us. I am using DC1394_COLOR_CODING_MONO8
colour coding, Format 7, Video Mode DC1394_VIDEO_MODE_FORMAT7_0, image
size 320x240 in both Windows and Linux. The speed is 400Mbps, and
bytes per packet 2048.

Warm regards,

Kiran.

On 1/12/07, Daniel Drake <dd...@br...> wrote:
> On Fri, 2007-01-12 at 13:05 +0530, Kiran Kumar wrote:
> > Hi ,
> >
> > I want to investigate video1394 in kernel module, In order to know and
> > to reduce the grab timings. If any one of you help me out with
> > following details.
> >
> > -> A brief discription or names about the function which deals with
> > the grabbing the image
>
> That doesn't really exist. The OHCI/hardware layer sticks the frame in
> memory at a pretermined DMA address and notifies video1394 through the
> ohci1394 iso_tasklet interrupt mechanism.
>
> --
> Daniel Drake
> Brontes Technologies, A 3M Company
>
>
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