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

[Paul Elder]

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>

Reviewed-by: Paul Elder <paul.elder 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) {
> +		const auto &cfg = config->at(0);
> +		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;
> 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
> +	 * to be done on the ImageStabilizer output 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.
> +	 *
>  	 * \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
> -- 
> 2.43.0
>