[PATCH v2 2/8] libcamera: rkisp1: Keep aspect ratio on imx8mp

[Jacopo Mondi]

Hi Stefan

On Mon, Nov 25, 2024 at 04:14:11PM +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.
>
> While at it, remove a todo comment that is no longer needed.
>
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>
> Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
>
> ---
>
> Changes in v2:
> - Fixed alignment
> - Improved comments
> - Removed todo comment
> - Collected tags
> ---
>  src/libcamera/pipeline/rkisp1/rkisp1.cpp      | 16 ++++++++++++++++
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp | 13 ++++++++-----
>  2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> index 5ffcfbce56be..a66b9dda83ab 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
> @@ -811,6 +811,22 @@ 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) {
> +		/* imx8mp has only a single path. */
> +		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 "

very minor nit:

What do you think about dropping "needs to be" from the Info message.

Also, this is a fairly typical thing, cropping to the output aspect
ratio before scaling, is it worth a Info message ?

Thanks
   j

> +					  << 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..eee5b09e2ff0 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> @@ -417,11 +417,14 @@ int RkISP1Path::configure(const StreamConfiguration &config,
>  	/*
>  	 * Crop on the resizer input to maintain FOV before downscaling.
>  	 *
> -	 * \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
> -	 * also take into account the need to crop away the edge pixels affected
> -	 * by the ISP processing blocks.
> +	 * Note that this does not apply to devices without DUAL_CROP support
> +	 * (like imx8mp) , where the cropping needs 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.
> +	 *
> +	 * Alignment to a multiple of 2 pixels is required by the resizer.
>  	 */
>  	Size ispCrop = inputFormat.size.boundedToAspectRatio(config.size)
>  				       .alignedUpTo(2, 2);
> --
> 2.43.0
>