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Re: em28xx v4l-info returns gibberish on igepv2




On Wed, 2010-03-03 at 09:56 -0500, Devin Heitmueller wrote:
> On Wed, Mar 3, 2010 at 8:12 AM, John Banks <john.banks@xxxxxxxxxxxxxxx> wrote:
> > I have an usb capture card that accepts composite and svideo and outputs
> > raw video through v4l2.
> >
> > When running the card on my laptop (ubuntu karmic) I am able to use
> > gstreamer to dump the raw video to a file. It comes out as yuv and can
> > be easily played back.
> 
> Hi John
> 
> I saw your question on #linuxtv yesterday, and reached out to you but
> I guess you didn't see the message.
> 
> I did some ARM work for the em28xx last year, and assuming there has
> been no regression, it should be working fine.  The fact that even the
> enumstd ioctl is returning zero'd data suggests that you've got some
> sort of basic userland/kernel communications problem, since that
> command has no interaction with the hardware at all (the driver fills
> out the result with statically defined data).  It might also be some
> sort of bug in v4l2-info.
> 
> Have you tried writing a quick 50-line C program that performs the
> ioctl and dumps the result?  That might help you narrow down whether
> it's a v4l2-info problem.
> 
> Without a board though, I'm not quite sure how I could debug this.
> 
> Devin
> 

Hey Devin,

Sorry I must have missed your message on irc, I had hung around for most
of the day, must have just missed you at the end.

Having never used ioctl before I spent most of the day reading up.

I created a dump as you suggested and you are right, it seems to be a
v4l-info problem.

chimp@ll-1:~/source/ioctl$ ./ioctl 
index:
0
id:
34592
name:
NTSC
frameperiod-numerator:
1001
frameperiod-denominator:
30000
framelines:
525
reserved:

As you can see I get the correct output. I think it has to do with the
size of variables created in struct-v4l2.c as they don't match the
declaration in videodev2.h

Anyway this doesn't help to explain why I get the 0000's seen in the
hexdump of the file. I had been hoping that it was incorrectly reading
the variables it needed in order for it to create the output correctly.

I was originally using the gstreamer v4l2src module that was in the
repositories but I tried compiling the gstreamer provided by TI (it
contains extra plugins for use on the dsp) but the same problem
occurred.

If I want to further track down this problem, where should I look?

Cheers

-- 
John Banks - Head of Engineering
Noonan Media Ltd 

www.noonanmedia.com 

MB: +44 779 62 64 707 
E: john.banks@xxxxxxxxxxxxxxx

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