NekoCWD/libcamera
NekoCWD/libcamera
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages 7 Wiki Activity Actions

libcamera: Rename "shutter speed" to "exposure time"

Browse source 
The terms "shutter" and "shutter speed" are used through libcamera to
mean "exposure time". This is confusing, both due to "speed" being used
as "time" while it should be the inverse (i.e. a maximum speed should
correspond to the minimum time), and due to "shutter speed" and
"exposure time" being used in different places with the same meaning.

To improve clarity of the code base and the documentation, use "exposure
time" consistently to replace "shutter speed".

This rename highlighted another vocabulary issue in libcamera. The
ExposureModeHelper::splitExposure() function used to document that it
splits "exposure time into shutter time and gain". It has been reworded
to "split exposure into exposure time and gain". That is not entirely
satisfactory, as "exposure" has a defined meaning in photography (see
https://en.wikipedia.org/wiki/Exposure_(photography)) that is not
expressed as a duration. This issue if left to be addressed separately.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Laurent Pinchart 2024-10-28 03:00:10 +02:00
parent e5f8d40bad
commit d0478c41f4
33 changed files with 334 additions and 327 deletions
Download patch file Download diff file Expand all files Collapse all files

27
src/ipa/rkisp1/algorithms/agc.cpp
View file

@ -183,7 +183,7 @@ int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
* except it's computed in the IPA and not here so we'd have to
* recompute it.
*/
context.activeState.agc.maxFrameDuration = context.configuration.sensor.maxShutterSpeed;
context.activeState.agc.maxFrameDuration = context.configuration.sensor.maxExposureTime;
/*
* Define the measurement window for AGC as a centered rectangle
@ -194,8 +194,8 @@ int Agc::configure(IPAContext &context, const IPACameraSensorInfo &configInfo)
context.configuration.agc.measureWindow.h_size = 3 * configInfo.outputSize.width / 4;
context.configuration.agc.measureWindow.v_size = 3 * configInfo.outputSize.height / 4;
setLimits(context.configuration.sensor.minShutterSpeed,
context.configuration.sensor.maxShutterSpeed,
setLimits(context.configuration.sensor.minExposureTime,
context.configuration.sensor.maxExposureTime,
context.configuration.sensor.minAnalogueGain,
context.configuration.sensor.maxAnalogueGain);
@ -424,12 +424,12 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
[](uint32_t x) { return x >> 4; });
expMeans_ = { params->ae.exp_mean, context.hw->numAeCells };
utils::Duration maxShutterSpeed =
utils::Duration maxExposureTime =
std::clamp(frameContext.agc.maxFrameDuration,
context.configuration.sensor.minShutterSpeed,
context.configuration.sensor.maxShutterSpeed);
setLimits(context.configuration.sensor.minShutterSpeed,
maxShutterSpeed,
context.configuration.sensor.minExposureTime,
context.configuration.sensor.maxExposureTime);
setLimits(context.configuration.sensor.minExposureTime,
maxExposureTime,
context.configuration.sensor.minAnalogueGain,
context.configuration.sensor.maxAnalogueGain);
@ -442,20 +442,21 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
double analogueGain = frameContext.sensor.gain;
utils::Duration effectiveExposureValue = exposureTime * analogueGain;
utils::Duration shutterTime;
utils::Duration newExposureTime;
double aGain, dGain;
std::tie(shutterTime, aGain, dGain) =
std::tie(newExposureTime, aGain, dGain) =
calculateNewEv(frameContext.agc.constraintMode,
frameContext.agc.exposureMode,
hist, effectiveExposureValue);
LOG(RkISP1Agc, Debug)
<< "Divided up shutter, analogue gain and digital gain are "
<< shutterTime << ", " << aGain << " and " << dGain;
<< "Divided up exposure time, analogue gain and digital gain are "
<< newExposureTime << ", " << aGain << " and " << dGain;
IPAActiveState &activeState = context.activeState;
/* Update the estimated exposure and gain. */
activeState.agc.automatic.exposure = shutterTime / context.configuration.sensor.lineDuration;
activeState.agc.automatic.exposure = newExposureTime
/ context.configuration.sensor.lineDuration;
activeState.agc.automatic.gain = aGain;
fillMetadata(context, frameContext, metadata);