[PATCH 2/7] libcamera: rkisp1: Keep aspect ratio on imx8mp

[Jacopo Mondi]

Hi Stefan

On Wed, Nov 20, 2024 at 09:57:41AM +0100, Stefan Klug wrote:
> In the current code, the input stage of the image resizer is used to
> apply a crop to keep the aspect ratio in cases where the requested
> output aspect ratio differs from the one of the selected sensor mode. On
> the imx8mp the resizer hardware is not capable of cropping (for
> reference see also rkisp1-resizer.c:rkisp1_rsz_set_sink_crop() in the
> linux kernel v6.10).
>
> Therefore apply the necessary cropping on the output of the ISP (on the
> image stabilization block). The cropping code on the image resizer
> doesn't need modifications as the requested crop gets ignored by the
> kernel.
>
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>  src/libcamera/pipeline/rkisp1/rkisp1.cpp      | 15 +++++++++++++++
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp |  6 ++++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> index 5ffcfbce56be..9d36554cec6e 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> @@ -811,6 +811,21 @@ int PipelineHandlerRkISP1::configure(Camera *camera, CameraConfiguration *c)
>  	if (!isRaw_)
>  		format.code = MEDIA_BUS_FMT_YUYV8_2X8;
>
> +	/*
> +	 * On devices without DUAL_CROP (like the imx8mp) cropping needs to be
> +	 * done on the ISP/IS output.
> +	 */
> +	if (media_->hwRevision() == RKISP1_V_IMX8MP) {

I wish we had a better way to identify the single ISP features instead
of relying on the whole model..

> +		const auto &cfg = config->at(0);

This will only work on (!DUAL_CROP && single_stream) which is the
imx8mp case.

I would add a comment to clarify we can assume config->at(0) because
of this

> +		Size ispCrop = format.size.boundedToAspectRatio(cfg.size)
> +				       .alignedUpTo(2, 2);

Please align

		Size ispCrop = format.size.boundedToAspectRatio(cfg.size)
				          .alignedUpTo(2, 2);

> +		rect = ispCrop.centeredTo(Rectangle(format.size).center());
> +		if (ispCrop != format.size)
> +			LOG(RkISP1, Info) << "ISP output needs to be cropped to "
> +					  << rect;
> +		format.size = ispCrop;
> +	}
> +
>  	LOG(RkISP1, Debug)
>  		<< "Configuring ISP output pad with " << format
>  		<< " crop " << rect;

Unrelated, but we have

	LOG(RkISP1, Debug)
		<< "ISP input pad configured with " << format
		<< " crop " << rect;


	LOG(RkISP1, Debug)
		<< "Configuring ISP output pad with " << format
		<< " crop " << rect;

It would be nice to align the two messages.

Also, unrelated, but do you know why we were already setting both crop
and format on the source pad with the same sizes ? Setting a format source
pad propagates its sizes to the crop rectangle. Is this a better safe
then sorry ?

> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> index 236d05af7a2f..0651de464907 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> @@ -417,6 +417,12 @@ int RkISP1Path::configure(const StreamConfiguration &config,
>  	/*
>  	 * Crop on the resizer input to maintain FOV before downscaling.
>  	 *
> +	 * Note that this does not apply on the imx8mp, where the cropping needs

I would say, as you did already

	 * Note that this does not apply to devices without DUAL_CROP
         * support (like imx8mp) , where the cropping needs

> +	 * to be done on the ImageStabilizer output and therefore is configured

What about re-stating that the IS block is configured through the ISP
source pad crop rectangle ?

	 * to be done on the ImageStabilizer block on the ISP source pad and
         * therefore is configured

> +	 * before this stage. For simplicity we still set the crop. This gets
> +	 * ignored by the kernel driver because the hardware is missing the
> +	 * capability.
> +	 *

nits apart
Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>

Thanks
  j

>  	 * \todo The alignment to a multiple of 2 pixels is required but may
>  	 * change the aspect ratio very slightly. A more advanced algorithm to
>  	 * compute the resizer input crop rectangle is needed, and it should

the driver aligns to 2 anyway, so this todo is kind of moot maybe
> --
> 2.43.0
>