[libcamera-devel] [PATCH v2 4/4] ipu3: cio2: Tweak sensor size selection policy

[Jacopo Mondi]

On Tue, Aug 10, 2021 at 01:28:54PM +0530, Umang Jain wrote:
> Do not compare higher precision of the ratios, as it might lead to
> absurd selection of sensor size for a relatively low requested
> resolution size.

Just "lead to size selection mismatches" maybe ?
The example below is explicative enough

>
> For example:
> The imx258 driver supports the following sensor resolutions:
>
>  - 4208x3118 = 1.349583066
>  - 2104x1560 = 1.348717949
>  - 1048x780  = 1.343589744
>
> It can be inferred that, that the aspect ratio only differs by a small

s/that, that/that/

> factor with each other. It does not makes sense to select a 4208x3118
> for a requested size of say 640x480 or 1280x720, which is what is
> happening currently.
> ($) cam -c1 -swidth=640,height=480,role=raw
>     - CIO2 configuration: 4208x3118-SGRBG10_IPU3
>
> In order to address this constraint, only compare the ratio with single
> precision to make a better decision on the sensor resolution policy
> selection.
>
> ($) cam -c1 -srole=raw,width=640,height=480
>     - CIO2 configuration: 1048x780-SGRBG10_IPU3
>
> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> Tested-by: Umang Jain <umang.jain at ideasonboard.com>
> Tested-by: Jacopo Mondi <jacopo at jmondi.org>

I recall I asked about if we want rounding or truncating is fine. I
think you confirmed truncating is fine, which I agree.

Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
  j

> ---
>  src/libcamera/pipeline/ipu3/cio2.cpp | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> index 3c9331e3..6ccef301 100644
> --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> @@ -290,6 +290,11 @@ V4L2SubdeviceFormat CIO2Device::getSensorFormat(const std::vector<unsigned int>
>  				continue;
>
>  			float ratio = static_cast<float>(sz.width) / sz.height;
> +			/*
> +			 * Comparing ratios with a single precision digit
> +			 * is enough.
> +			 */
> +			ratio = static_cast<unsigned int>(ratio * 10) / 10.0;
>  			float ratioDiff = fabsf(ratio - desiredRatio);
>  			unsigned int area = sz.width * sz.height;
>  			unsigned int areaDiff = area - desiredArea;
> --
> 2.31.1
>