Re: Apparent inconsistency in the labels of Bayer tilings

[Hans de Goede <j.w.r.degoede@hhs.nl>]

kilgota@banach.math.auburn.edu wrote:
> 
> Thanks for the recommendation about gettimeofday. I will try putting 
> that in. Right now, I wonder if you know something about the following:
> 
> In order to make your Bayer demosaicing algorithm work, I had to do the 
> following because otherwise the colors were mapped backwards:
> 
> 1. create new entries in your libv4lconvert-priv.h like this
> 
> #ifndef V4L2_PIX_FMT_SBGGR8
> #define V4L2_PIX_FMT_SBGGR8 v4l2_fourcc('B','G','G','R')
> #endif
> 

Erm, that one is defined in linux/videodev2.h and has been for a long time:
#define V4L2_PIX_FMT_SBGGR8  v4l2_fourcc('B', 'A', '8', '1') /*  8  BGBG.. 
GRGR.. */

But I see I did not include it in libv4lconvert-priv.h, my bad.

Anyways to which fourcc you define V4L2_PIX_FMT_SBGGR8 should not matter, as 
for the meaning of the defines, as the command above shows in v4l BGGR means 
first line: BGBG.. second line: GRGR.., and then third line BGBG.. again, etc.

That seems pretty straightforward to me, how are libgphoto's defines supposed 
to be interpreted?

> #ifndef BAYER_TILE_BGGR
> #define BAYER_TILE_BGGR V4L2_PIX_FMT_SBGGR8
> #endif
> 
> and then use these. But in libgphoto2 the same photo from the same 
> camera has to use
> 
> BAYER_TILE_RGGB
> 
> So in other words when changing over the Bayer algorithm I also had to 
> change the label for the tiling from RGGB over to BGGR.
> 
> What gives? Do you happen to know? The two labels clearly disagree to 
> such an extent that they cannot both be right. Of course, the whole 
> thing is a matter of convention, presumably settled a long time ago by 
> someone who was neither of us. Also, the labeling of the Bayer tiles in 
> Gphoto was done long before I came along and thus I am not responsible 
> for it. So I explicitly do not give and do not have an opinion about who 
> is right.

The v4l convention also stems from before I came a long, I merely added the 
other 3 possible bayer patterns to the list.

Regards,

Hans


--
video4linux-list mailing list
Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/video4linux-list