[libcamera-devel] [PATCH] ipa: rpi: imx708: Fix mode switch drop frame count

[David Plowman]

Hi Naush

Thanks for the patch.

On Mon, 26 Jun 2023 at 14:08, Naushir Patuck via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> The imx708 must drop a single frame on startup - but only when in HDR
> mode. Non-HDR modes do not need to drop frames. Fix the logic in
> hideFramesModeSwitch() which currently unconditionally advertises to
> drop one frame.
>
> Unfortunately there is no clear way to tell if the sensor is in the HDR
> mode. So for now, look the resolution and framerate to deduce this.
>
> Additionally ensure we override hideFramesStartup() and return the same
> number as hideFramesModeSwitch().
>
> Bug: https://github.com/raspberrypi/libcamera-apps/issues/524
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>

Indeed, it's not lovely is it? But in the absence of a "tonemapped HDR
format" or something to that effect, it's hard to think of a good
solution.

Reviewed-by: David Plowman <david.plowman at raspberrypi.com>

Thanks
David

> ---
>  src/ipa/rpi/cam_helper/cam_helper_imx708.cpp | 25 +++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/src/ipa/rpi/cam_helper/cam_helper_imx708.cpp b/src/ipa/rpi/cam_helper/cam_helper_imx708.cpp
> index 641ba18f4b9d..2cd7afdbd8ec 100644
> --- a/src/ipa/rpi/cam_helper/cam_helper_imx708.cpp
> +++ b/src/ipa/rpi/cam_helper/cam_helper_imx708.cpp
> @@ -21,6 +21,8 @@ using namespace RPiController;
>  using namespace libcamera;
>  using libcamera::utils::Duration;
>
> +using namespace std::literals::chrono_literals;
> +
>  namespace libcamera {
>  LOG_DECLARE_CATEGORY(IPARPI)
>  }
> @@ -56,7 +58,8 @@ public:
>                        int &vblankDelay, int &hblankDelay) const override;
>         bool sensorEmbeddedDataPresent() const override;
>         double getModeSensitivity(const CameraMode &mode) const override;
> -       unsigned int hideFramesModeSwitch() const override { return 1; } // seems to be required for HDR
> +       unsigned int hideFramesModeSwitch() const override;
> +       unsigned int hideFramesStartup() const;
>
>  private:
>         /*
> @@ -225,6 +228,26 @@ double CamHelperImx708::getModeSensitivity(const CameraMode &mode) const
>         return (mode.width > 2304) ? 1.0 : 2.0;
>  }
>
> +unsigned int CamHelperImx708::hideFramesModeSwitch() const
> +{
> +       /*
> +        * We need to drop the first startup frame in HDR mode.
> +        * Unfortunately the only way to currently determine if the sensor is in
> +        * the HDR mode is to match with the resolution and framerate - the HDR
> +        * mode only runs upto 30fps.
> +        */
> +       if (mode_.width == 2304 && mode_.height == 1296 &&
> +           mode_.minFrameDuration <= 1.0s / 30)
> +               return 1;
> +       else
> +               return 0;
> +}
> +
> +unsigned int CamHelperImx708::hideFramesStartup() const
> +{
> +       return hideFramesModeSwitch();
> +}
> +
>  void CamHelperImx708::populateMetadata(const MdParser::RegisterMap &registers,
>                                        Metadata &metadata) const
>  {
> --
> 2.34.1
>