[libcamera-devel] [PATCH 00/11] libcamera: introduce Software ISP and Software IPA

[Hans de Goede]

Hi,

On 12/18/23 11:05, Hans de Goede wrote:

<snip>

>> f8efb3be ("libcamera: software_isp: fix AWB algorithm not to increase luminance") makes the luminance not to change
>>     due to the colour gains applied. This improves the image a bit (makes it a bit less bright), but the effect
>>     is relatively small - within 10% depending on the light and the objects in the particular image. This change
>>     increases the load on CPU, so I am not sure if this image improvement is worth this higher CPU utilization.
> 
> Interesting since we have r g b lookup tables already the extra CPU load is only
> in generating the green table
> once per frame, the load of that should be negligible.
> 
> And with the separate gamma lookup we can then also give the gamma-lookup table a bit
> more precision giving it 1024 entries. The impact of this on performance should be
> minimal.

Quick remark on this fix, I had to change the y256 type from unsigned int to unsigned long
because with a FHD sensor 256 * averagesum of ~700000 pixels does not fit in 32 bits.

I have a WIP branch with your 3 improvements (with 1024 gamma entries) squashed in
here:

https://github.com/jwrdegoede/libcamera/commits/SoftwareISP-v04

Note I regularly do forced pushes there as I keep refining things.

Regards,

Hans





> 
>> f5906f15 ("[DNI] libcamera: software_isp: print colour gains to the log") prints the colour gains to the console
>>     so that one could see the effect of the previous patch - without it the green gain would always be 256, and the
>>     other two gains would increase in the same proportion. E.g. "gains R/G/B = 253/240/406" would become
>>     "gains R/G/B = 270/256/433" without commit f8efb3be.
> 
> I think we probably want something like this (but then in the IPA once the AWB calculations
> have moved there) and then using a log-level of debug. Doing a debug log once per frame
> should have no performance impact when debug logging is disabled.
> 
> Regards,
> 
> Hans
>