Re: em28xx v4l-info returns gibberish on igepv2
- Date: Thu, 04 Mar 2010 11:29:01 +0000
- From: John Banks <john.banks@xxxxxxxxxxxxxxx>
- Subject: 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.
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
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
If I want to further track down this problem, where should I look?
John Banks - Head of Engineering
Noonan Media Ltd
MB: +44 779 62 64 707
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