[v2,2/3] ipa: libipa: agc_mean_luminance: Change luminance target to piecewise linear function

24982 diff mbox series

In some situations it is necessary to specify the target brightness
value depending on the overall lux level. This is a rework [1] to fit
current master. As the PWL loading code loads a plain value as single
point PWL, backwards compatibility to existing tuning files is ensured.

[1] https://patchwork.libcamera.org/patch/20231/

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>

---

Changes in v2:
- Collected tags
- Dropped special handling of plain values, as this is now part of the
  yaml PWL loader.
---
 src/ipa/libipa/agc_mean_luminance.cpp | 51 +++++++++++++++++++++++----
 src/ipa/libipa/agc_mean_luminance.h   | 11 ++++--
 src/ipa/rkisp1/algorithms/agc.cpp     |  1 +
 3 files changed, 55 insertions(+), 8 deletions(-)

Quoting Stefan Klug (2025-11-06 16:42:26)
> In some situations it is necessary to specify the target brightness
> value depending on the overall lux level. This is a rework [1] to fit
> current master. As the PWL loading code loads a plain value as single
> point PWL, backwards compatibility to existing tuning files is ensured.
> 
> [1] https://patchwork.libcamera.org/patch/20231/

reworking [1] to master should not be in the commit message. When this
is merged, old versions are irrelevant.

> 
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
> Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
> 
> ---
> 
> Changes in v2:
> - Collected tags
> - Dropped special handling of plain values, as this is now part of the
>   yaml PWL loader.
> ---
>  src/ipa/libipa/agc_mean_luminance.cpp | 51 +++++++++++++++++++++++----
>  src/ipa/libipa/agc_mean_luminance.h   | 11 ++++--
>  src/ipa/rkisp1/algorithms/agc.cpp     |  1 +
>  3 files changed, 55 insertions(+), 8 deletions(-)
> 
> diff --git a/src/ipa/libipa/agc_mean_luminance.cpp b/src/ipa/libipa/agc_mean_luminance.cpp
> index 64f36bd75dd2..b80af92a2c0f 100644
> --- a/src/ipa/libipa/agc_mean_luminance.cpp
> +++ b/src/ipa/libipa/agc_mean_luminance.cpp
> @@ -54,6 +54,14 @@ static constexpr double kDefaultRelativeLuminanceTarget = 0.16;
>   */
>  static constexpr double kMaxRelativeLuminanceTarget = 0.95;
>  
> +/*
> + * Default lux level
> + *
> + * If no lux level or a zero lux level is specified, but PWLs are used to
> + * specify luminance targets, this default level is used.
> + */
> +static constexpr unsigned int kDefaultLuxLevel = 500;
> +
>  /**
>   * \struct AgcMeanLuminance::AgcConstraint
>   * \brief The boundaries and target for an AeConstraintMode constraint
> @@ -145,16 +153,24 @@ static constexpr double kMaxRelativeLuminanceTarget = 0.95;
>  
>  AgcMeanLuminance::AgcMeanLuminance()
>         : exposureCompensation_(1.0), frameCount_(0), filteredExposure_(0s),
> -         relativeLuminanceTarget_(0)
> +         lux_(0)
>  {
>  }
>  
>  AgcMeanLuminance::~AgcMeanLuminance() = default;
>  
> -void AgcMeanLuminance::parseRelativeLuminanceTarget(const YamlObject &tuningData)
> +int AgcMeanLuminance::parseRelativeLuminanceTarget(const YamlObject &tuningData)
>  {
> -       relativeLuminanceTarget_ =
> -               tuningData["relativeLuminanceTarget"].get<double>(kDefaultRelativeLuminanceTarget);
> +       auto &target = tuningData["relativeLuminanceTarget"];
> +       auto pwl = target.get<Pwl>();
> +       if (!pwl) {
> +               LOG(AgcMeanLuminance, Error)
> +                       << "Failed to load relative luminance target.";
> +               return -EINVAL;
> +       }
> +
> +       relativeLuminanceTarget_ = std::move(*pwl);
> +       return 0;
>  }
>  
>  void AgcMeanLuminance::parseConstraint(const YamlObject &modeDict, int32_t id)
> @@ -385,7 +401,9 @@ int AgcMeanLuminance::parseTuningData(const YamlObject &tuningData)
>  {
>         int ret;
>  
> -       parseRelativeLuminanceTarget(tuningData);
> +       ret = parseRelativeLuminanceTarget(tuningData);
> +       if (ret)
> +               return ret;
>  
>         ret = parseConstraintModes(tuningData);
>         if (ret)
> @@ -403,6 +421,16 @@ int AgcMeanLuminance::parseTuningData(const YamlObject &tuningData)
>   * AGC calculations. It is expressed as gain instead of EV.
>   */
>  
> +/**
> + * \fn AgcMeanLuminance::setLux(int lux)
> + * \brief Set the lux level
> + * \param[in] lux The lux level
> + *
> + * This function sets the lux level to be used in the AGC calculations. A value
> + * of 0 means no measurement and a default value of \a kDefaultLuxLevel is used
> + * if necessary.
> + */
> +
>  /**
>   * \brief Set the ExposureModeHelper limits for this class
>   * \param[in] minExposureTime Minimum exposure time to allow
> @@ -538,7 +566,18 @@ double AgcMeanLuminance::constraintClampGain(uint32_t constraintModeIndex,
>   */
>  double AgcMeanLuminance::effectiveYTarget() const
>  {
> -       return std::min(relativeLuminanceTarget_ * exposureCompensation_,
> +       double lux = lux_;
> +       if (relativeLuminanceTarget_.size() > 1 && lux_ == 0) {
> +               LOG(AgcMeanLuminance, Debug)
> +                       << "Missing lux value for luminance target calculation, default to "
> +                       << kDefaultLuxLevel;
> +               lux = kDefaultLuxLevel;
> +       }
> +
> +       double luminanceTarget = relativeLuminanceTarget_.eval(
> +               relativeLuminanceTarget_.domain().clamp(lux));
> +
> +       return std::min(luminanceTarget * exposureCompensation_,
>                         kMaxRelativeLuminanceTarget);
>  }
>  
> diff --git a/src/ipa/libipa/agc_mean_luminance.h b/src/ipa/libipa/agc_mean_luminance.h
> index d7ec548e3e58..1fbff304a72b 100644
> --- a/src/ipa/libipa/agc_mean_luminance.h
> +++ b/src/ipa/libipa/agc_mean_luminance.h
> @@ -20,6 +20,7 @@
>  
>  #include "exposure_mode_helper.h"
>  #include "histogram.h"
> +#include "pwl.h"
>  
>  namespace libcamera {
>  
> @@ -50,6 +51,11 @@ public:
>                 exposureCompensation_ = gain;
>         }
>  
> +       void setLux(unsigned int lux)
> +       {
> +               lux_ = lux;
> +       }
> +
>         void setLimits(utils::Duration minExposureTime, utils::Duration maxExposureTime,
>                        double minGain, double maxGain, std::vector<AgcConstraint> constraints);
>  
> @@ -81,8 +87,8 @@ public:
>  
>  private:
>         virtual double estimateLuminance(const double gain) const = 0;
> +       int parseRelativeLuminanceTarget(const YamlObject &tuningData);
>  
> -       void parseRelativeLuminanceTarget(const YamlObject &tuningData);
>         void parseConstraint(const YamlObject &modeDict, int32_t id);
>         int parseConstraintModes(const YamlObject &tuningData);
>         int parseExposureModes(const YamlObject &tuningData);
> @@ -95,7 +101,8 @@ private:
>         double exposureCompensation_;
>         uint64_t frameCount_;
>         utils::Duration filteredExposure_;
> -       double relativeLuminanceTarget_;
> +       unsigned int lux_;
> +       Pwl relativeLuminanceTarget_;
>  
>         std::vector<AgcConstraint> additionalConstraints_;
>         std::map<int32_t, std::vector<AgcConstraint>> constraintModes_;
> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
> index f5a3c917cb69..1ecaff680978 100644
> --- a/src/ipa/rkisp1/algorithms/agc.cpp
> +++ b/src/ipa/rkisp1/algorithms/agc.cpp
> @@ -618,6 +618,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
>                 effectiveExposureValue *= frameContext.agc.quantizationGain;
>  
>         setExposureCompensation(pow(2.0, frameContext.agc.exposureValue));
> +       setLux(frameContext.lux.lux);

Should this be from the active state (the most current/latest known lux
level) rather than the frame context? Or do we know that the lux is run
before this and is correct for this frame ?

(Especially as Lux comes after Agc alphabetically)

Do we need to do anything to enforce that lux is run /before/ AGC
otherwise?

Otherwise I expect we'd see it default to zero and therefore default to
the kDefaultLux level 'always'?

--
Kieran


>  
>         utils::Duration newExposureTime;
>         double aGain, qGain, dGain;
> -- 
> 2.51.0
>