[libcamera-devel,v2] ipa: ipu3: agc: Clamp shutter speed
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Message ID 20211026112750.113641-1-jeanmichel.hautbois@ideasonboard.com
State Accepted
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Series
  • [libcamera-devel,v2] ipa: ipu3: agc: Clamp shutter speed
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Commit Message

Jean-Michel Hautbois Oct. 26, 2021, 11:27 a.m. UTC 
In case the maximum exposure received from the sensor is very high, we
can have a very high shutter speed with a small analogue gain, and it
may result in very slow framerate. We are not really supporting it for
the moment, so clamp the shutter speed to an arbitrary value of 60ms.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Tested-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

---
v2:
- Reword the todo according to Laurent's comment
---
 src/ipa/ipu3/algorithms/agc.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Patch
diff mbox series 

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 6c151232..6b4ba4bf 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -34,6 +34,9 @@  static constexpr uint32_t kFrameSkipCount = 6;
 static constexpr double kMinAnalogueGain = 1.0;
 static constexpr double kMaxAnalogueGain = 8.0;
 
+/* \todo Honour the FrameDurationLimits control instead of hardcoding a limit */
+static constexpr utils::Duration kMaxShutterSpeed = 60ms;
+
 /* Histogram constants */
 static constexpr uint32_t knumHistogramBins = 256;
 static constexpr double kEvGainTarget = 0.5;
@@ -54,7 +57,8 @@  int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
 
 	/* \todo replace the exposure in lines storage with time based ones. */
 	minExposureLines_ = context.configuration.agc.minShutterSpeed / lineDuration_;
-	maxExposureLines_ = context.configuration.agc.maxShutterSpeed / lineDuration_;
+	maxExposureLines_ = std::min(context.configuration.agc.maxShutterSpeed / lineDuration_,
+				     kMaxShutterSpeed / lineDuration_);
 
 	minAnalogueGain_ = std::max(context.configuration.agc.minAnalogueGain, kMinAnalogueGain);
 	maxAnalogueGain_ = std::min(context.configuration.agc.maxAnalogueGain, kMaxAnalogueGain);