Re: Pixel Formats

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

(A bit late, sorry)

On Thursday 07 March 2013 22:37:26 Guennadi Liakhovetski wrote:
> On Wed, 6 Mar 2013, Christian Rhodin wrote:
> > Hi,
> > 
> > I'm looking for some guidance on the correct way to handle a new pixel
> > format.  What I'm dealing with is a CMOS image sensor that supports
> > dynamic switching between linear and iHDR modes.  iHDR stands for
> > "interlaced High Dynamic Range" and is a mode where odd and even lines
> > have different exposure times, typically with an 8:1 ratio.  When I
> > started implementing a driver for this sensor I used
> > "V4L2_MBUS_FMT_SGRBG10_1X10" as the format for the linear mode and
> > defined a new format "V4L2_MBUS_FMT_SGRBG10_IHDR_1X10" for the iHDR
> > mode.  I used the format to control which mode I put the sensor in.  But
> > now I'm having trouble switching modes without reinitializing the
> > sensor.  Does anyone (everyone?) have an opinion about the correct way
> > to implement this?  I'm thinking that the format is overloaded because
> > it represents both the size and type of the data.  Should I use a single
> > format and add a control to switch the mode?
> 
> I would vote for a single format with a control, maybe even somehow
> cluster it with the normal exposure, but I'm not an expert in that, not
> sure if it would make sense.

>From the above explanation about iHDR I assume that enabling iHDR mode 
produces an image with the same resolution as linear mode, not an image with 8 
times the number of lines compared to the linear mode. Please correct me if 
I'm wrong.

If my understanding of iHDR mode is correct, I agree with Guennadi. I don't 
think enabling iHDR changes the format, it "just" modifies the exposure time 
algorithm. A V4L2 control would thus be better than adding an iHDR variant to 
all existing formats.

-- 
Regards,

Laurent Pinchart