[libcamera-devel] libcamera on Librem 5, phase detection auto focus

[Pavel Machek]

Hi!

> > So far I'm working with contrast detection, but samsung chip should
> > support phase detection auto focus, too. So far I hacked
> > drivers/media/i2c/s5k3l6xx.ko not to filter out those bits and took
> > photos (and looked at them in darktable), but I don't see any obvious
> > "defects" indicating presense of focus data. Do you have any pointers
> > to more information by chance?
> > 
> > I took deliberately defocused photo to make "defects" easier to see. I
> > guess I should take another one with less gain to keep other noise
> > down. Any ideas how to locate those bits?
> 
> The PDAF pixels will be located at fixed positions in the pixel array,
> documented by the sensor vendor. Some sensors will process the PDAF
> pixels and provide the processed information in the CSI-2 embedded data.
> I don't have access to the sensor datasheet, so I can't help much I'm
> afraid :-(

Yep, I think I'm figuring it out with some help.

In case of L5, pixels are in the pixel array, and it is blue
pixels. So... it is easy to take blurry 13M photo of barcode (with
hacked driver, see above), remove red and green channels, enhance
contrast... and pattern emerges. Pairs of pixels emerge, and they
should be those AF pixels.

Now I guess I'll need to select two lines of special pixels, compute
correlation between them, and adjust focus according to that.

Does not sound too bad...? But if someone already has code / tools to
help, let me know.

Best regards,
								Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.
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