Re: PATCH: gspca-spc200nc-upside-down-v2

[Jean-Francois Moine <moinejf@free.fr>]

On Thu, 2008-08-21 at 15:51 +0200, Hans de Goede wrote:
> Jean-Francois Moine wrote:
	[snip]
> > Well, I looked at various messages in various mail-lists talking about
> > upside down. Sometimes, a webcam may be normal or upside down, or even
> > just mirrored. Two times only (Vimicro 0325 and 0326), they say that the
> > webcam is always upside down. So, is it useful to make a generic code
> > for this specific case?
> 
> Yes, as that will make these webcam work out of the box for end users. Please 
> stop thinking as a developer for a moment and start thinking as a simple end 
> user plugging such a cam into his asus eee pc, which is his first and only 
> linux machine. What do you think he will like better, the upside down picture 
> or the hey cool I plug in in this cam and it just works (tm) ?

It is possible if some system application (hal?) does the job.

> > For the general case (the webcam may have H or V flip, or both - upside
> > down). The user will see it. If she may use the HFLIP and VFLIP
> > controls, she will get a correct image.
> 
> Currently the 4 major (as in more then just a gimmick) end user v4l wewbcam 
> programs I'm aware of are:
> ekiga
> cheese
> flash plugin
> skype
> 
> And AFAIK (didn't check skype) non of these offer a simple GUI option for the 
> user to change vflip / hflip controls. Telling a user to go the cmdline is not 
> *userfriendly* and in this scenario is not necessary!

You did not try v4l2ucp?

	[snip]
> The reason why I'm spending tons of time on all this webcam stuff, is so that 
> end users can just plugin their cam and have it work. If that requires a 
> special flag for just these 2 cams so be it and I strongly believe we will 
> encounter other cams like this in the future.
	[snip]

Sorry, but I am not happy the way it is done. Here is an other proposal.

In the V4L2 spec, VIDIOC_QUERYCTRL returns the controls accepted (or
rejected) by the driver, and also information about these ones. As the
Vimicro/Z-star has no way to change H and V flips, the driver may give
these controls as READ_ONLY and set the control values according to the
device type.

Now, when accessing the device, the V4L library will get the flags and
values of the H and V flip. If HFLIP and VFLIP are settable, the driver
does all the job. If not (HFLIP and VFLIP are READ_ONLY or INVAL), the
library memorizes the control values of the driver (INVAL implies 0) and
also the values asked by the application. Frame decoding is then H
and/or H flipped according to (<driver value> ^ <user value>).

And now, for something completely different! I could not find a MS-win
snoop of these 'upside down' devices (0471:0325 and 0471:0326). I want
to check the initialization sequences and also the format of the frames.
May anybody send one to me? Thank you.

Cheers.

-- 
Ken ar c'hentañ |             ** Breizh ha Linux atav! **
Jef             |               http://moinejf.free.fr/


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