[v3,03/19] libipa: camera_sensor_helper: Add quantizeGain() function

24113 diff mbox series

Add a small utility function that calculates the quantized gain that
gets applied by a sensor when the gain code is set to gainCode(gain).
This is needed by algorithms to calculate a digital correction gain that
gets applied to mitigate the error introduce by quantization.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>

---

Changes in v3:
- Remove virtual from quantizeGain()
- Improved documentation
- Collected tags
---
 src/ipa/libipa/camera_sensor_helper.cpp | 23 +++++++++++++++++++++++
 src/ipa/libipa/camera_sensor_helper.h   |  1 +
 2 files changed, 24 insertions(+)

Quoting Stefan Klug (2025-08-15 19:29:23)
> Add a small utility function that calculates the quantized gain that
> gets applied by a sensor when the gain code is set to gainCode(gain).
> This is needed by algorithms to calculate a digital correction gain that
> gets applied to mitigate the error introduce by quantization.
> 
> Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
> Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
> 
> ---
> 
> Changes in v3:
> - Remove virtual from quantizeGain()
> - Improved documentation
> - Collected tags
> ---
>  src/ipa/libipa/camera_sensor_helper.cpp | 23 +++++++++++++++++++++++
>  src/ipa/libipa/camera_sensor_helper.h   |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> index dcd69d9f2bbb..a490161faf4c 100644
> --- a/src/ipa/libipa/camera_sensor_helper.cpp
> +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> @@ -131,6 +131,29 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
>         }
>  }
>  
> +/**
> + * \brief Quantize the given gain value
> + * \param[in] _gain The real gain
> + * \param[out] quantizationGain The gain that is lost due to quantization
> + *
> + * This function returns the actual gain that is applied when the sensors gain

s/sensors/sensor's/

> + * is set to gainCode(gain).

s/(gain)/(_gain)/ I think might be clearer?

> + *
> + * It shall be guaranteed that gainCode(gain) == gainCode(quantizeGain(gain)).

Same here.

> + *
> + * If \a quantizationGain is provided it is filled with the gain that must be

Personally I'd prefer s/filled/populated/, since filling feels like there could
be an initial value that you "fill" until you reach the target value. It's just
a feeling though :)

> + * applied to correct the losses due to quantization.

s/applied to/applied to \a _gain/ and s/the/for the/ I think is slightly clearer.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

> + *
> + * \return The quantized real gain
> + */
> +double CameraSensorHelper::quantizeGain(double _gain, double *quantizationGain) const
> +{
> +       double g = gain(gainCode(_gain));
> +       if (quantizationGain)
> +               *quantizationGain = _gain / g;
> +       return g;
> +}
> +
>  /**
>   * \struct CameraSensorHelper::AnalogueGainLinear
>   * \brief Analogue gain constants for the linear gain model
> diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h
> index a9300a64f1e7..bd3d0beec77f 100644
> --- a/src/ipa/libipa/camera_sensor_helper.h
> +++ b/src/ipa/libipa/camera_sensor_helper.h
> @@ -29,6 +29,7 @@ public:
>         std::optional<int16_t> blackLevel() const { return blackLevel_; }
>         virtual uint32_t gainCode(double gain) const;
>         virtual double gain(uint32_t gainCode) const;
> +       double quantizeGain(double gain, double *quantizationGain) const;
>  
>  protected:
>         struct AnalogueGainLinear {
> -- 
> 2.48.1
>