libcamera  v0.4.0
Supporting cameras in Linux since 2019
Classes | Public Member Functions | Protected Attributes | List of all members
libcamera::ipa::CameraSensorHelper Class Reference

Base class for computing sensor tuning parameters using sensor-specific constants. More...

Classes

struct  AnalogueGainExp
 Analogue gain constants for the exponential gain model. More...
 
struct  AnalogueGainLinear
 Analogue gain constants for the linear gain model. More...
 

Public Member Functions

 CameraSensorHelper ()=default
 Construct a CameraSensorHelper instance. More...
 
std::optional< int16_t > blackLevel () const
 Fetch the black level of the sensor. More...
 
virtual uint32_t gainCode (double gain) const
 Compute gain code from the analogue gain absolute value. More...
 
virtual double gain (uint32_t gainCode) const
 Compute the real gain from the V4L2 subdev control gain code. More...
 

Protected Attributes

std::optional< int16_t > blackLevel_
 The black level of the sensor. More...
 
std::variant< std::monostate, AnalogueGainLinear, AnalogueGainExpgain_
 The analogue gain parameters used for calculation. More...
 

Detailed Description

Base class for computing sensor tuning parameters using sensor-specific constants.

Instances derived from CameraSensorHelper class are sensor-specific. Each supported sensor will have an associated base class defined.

Constructor & Destructor Documentation

◆ CameraSensorHelper()

libcamera::ipa::CameraSensorHelper::CameraSensorHelper ( )
default

Construct a CameraSensorHelper instance.

CameraSensorHelper derived class instances shall never be constructed manually but always through the CameraSensorHelperFactoryBase::create() function.

Member Function Documentation

◆ blackLevel()

libcamera::ipa::CameraSensorHelper::blackLevel ( ) const
inline

Fetch the black level of the sensor.

This function returns the black level of the sensor scaled to a 16bit pixel width. If it is unknown an empty optional is returned.

Todo:
Fill the blanks and add pedestal values for all supported sensors. Once done, drop the std::optional<>.

Black levels are typically the result of the following phenomena:

  • Pedestal added by the sensor to pixel values. They are typically fixed, sometimes programmable and should be reported in datasheets (but documentation is not always available).
  • Dark currents and other physical effects that add charge to pixels in the absence of light. Those can depend on the integration time and the sensor die temperature, and their contribution to pixel values depend on the sensor gains.

The pedestal is usually the value with the biggest contribution to the overall black level. In most cases it is either known before or in rare cases (there is not a single driver with such a control in the linux kernel) can be queried from the sensor. This function provides that fixed, known value.

Returns
The black level of the sensor, or std::nullopt if not known

◆ gain()

double libcamera::ipa::CameraSensorHelper::gain ( uint32_t  gainCode) const
virtual

Compute the real gain from the V4L2 subdev control gain code.

Parameters
[in]gainCodeThe V4L2 subdev control gain

This function aims to abstract the calculation of the gain letting the IPA use the real gain for its estimations. It is the counterpart of the function CameraSensorHelper::gainCode.

Returns
The real gain

◆ gainCode()

uint32_t libcamera::ipa::CameraSensorHelper::gainCode ( double  gain) const
virtual

Compute gain code from the analogue gain absolute value.

Parameters
[in]gainThe real gain to pass

This function aims to abstract the calculation of the gain letting the IPA use the real gain for its estimations.

Returns
The gain code to pass to V4L2

Member Data Documentation

◆ blackLevel_

libcamera::ipa::CameraSensorHelper::blackLevel_
protected

The black level of the sensor.

See also
CameraSensorHelper::blackLevel()

◆ gain_

libcamera::ipa::CameraSensorHelper::gain_
protected

The analogue gain parameters used for calculation.

The analogue gain is calculated through a formula, and its parameters are sensor specific. Use this variable to store the values at init time.


The documentation for this class was generated from the following files: