[libcamera-devel] [PATCH 2/2] libcamera: pipeline: uvcvideo: Implement AeFlickerMode

[Kieran Bingham]

UVC devices often provide controls to support setting the power line
frequency which adapts the camera processing to avoid flicker visible to
the user.

Now that libcamera has implemented AeFlickerMode, use the new control to
implement support for UVC devices.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 59 ++++++++++++++++++--
 1 file changed, 55 insertions(+), 4 deletions(-)

diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
index 38f48a5d9269..365410284e5b 100644
--- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
+++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
@@ -89,8 +89,8 @@ public:
 	bool match(DeviceEnumerator *enumerator) override;
 
 private:
-	int processControl(ControlList *controls, unsigned int id,
-			   const ControlValue &value);
+	int processControl(Request *request, ControlList *controls,
+			   unsigned int id, const ControlValue &value);
 	int processControls(UVCCameraData *data, Request *request);
 
 	UVCCameraData *cameraData(Camera *camera)
@@ -260,7 +260,8 @@ void PipelineHandlerUVC::stopDevice(Camera *camera)
 	data->video_->releaseBuffers();
 }
 
-int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
+int PipelineHandlerUVC::processControl(Request *request, ControlList *controls,
+				       unsigned int id,
 				       const ControlValue &value)
 {
 	uint32_t cid;
@@ -277,6 +278,8 @@ int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
 		cid = V4L2_CID_EXPOSURE_ABSOLUTE;
 	else if (id == controls::AnalogueGain)
 		cid = V4L2_CID_GAIN;
+	else if (id == controls::AeFlickerMode)
+		cid = V4L2_CID_POWER_LINE_FREQUENCY;
 	else
 		return -EINVAL;
 
@@ -331,6 +334,42 @@ int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
 		break;
 	}
 
+	case V4L2_CID_POWER_LINE_FREQUENCY: {
+		enum v4l2_power_line_frequency mode;
+		unsigned int period = request->controls().get(controls::AeFlickerPeriod)
+							 .value_or(0);
+		switch (value.get<int32_t>()) {
+		default:
+		case controls::FlickerOff:
+			mode = V4L2_CID_POWER_LINE_FREQUENCY_DISABLED;
+			break;
+		case controls::FlickerAuto:
+			mode = V4L2_CID_POWER_LINE_FREQUENCY_AUTO;
+			break;
+		case controls::FlickerManual:
+			switch (period) {
+			case 10000: /* 100Hz in microseconds */
+				mode = V4L2_CID_POWER_LINE_FREQUENCY_50HZ;
+				break;
+			case 8333: /* 120Hz in microseconds */
+				mode = V4L2_CID_POWER_LINE_FREQUENCY_60HZ;
+				break;
+			default:
+				LOG(UVC, Warning)
+					<< "Unsupported AeFlickerPeriod : "
+					<< period;
+				[[fallthrough]];
+			case 0:
+				mode = V4L2_CID_POWER_LINE_FREQUENCY_DISABLED;
+				break;
+			}
+			break;
+		}
+
+		controls->set(cid, static_cast<int32_t>(mode));
+		break;
+	}
+
 	default: {
 		int32_t ivalue = value.get<int32_t>();
 		controls->set(cid, ivalue);
@@ -346,7 +385,7 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
 	ControlList controls(data->video_->controls());
 
 	for (const auto &[id, value] : request->controls())
-		processControl(&controls, id, value);
+		processControl(request, &controls, id, value);
 
 	for (const auto &ctrl : controls)
 		LOG(UVC, Debug)
@@ -605,6 +644,9 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
 	case V4L2_CID_GAIN:
 		id = &controls::AnalogueGain;
 		break;
+	case V4L2_CID_POWER_LINE_FREQUENCY:
+		id = &controls::AeFlickerMode;
+		break;
 	default:
 		return;
 	}
@@ -689,6 +731,15 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
 		break;
 	}
 
+	case V4L2_CID_POWER_LINE_FREQUENCY: {
+		info = ControlInfo{
+			{ static_cast<int>(controls::FlickerOff) },
+			{ static_cast<int>(controls::FlickerAuto) },
+			{ static_cast<int>(controls::FlickerOff) }
+		};
+		break;
+	}
+
 	default:
 		info = v4l2Info;
 		break;
-- 
2.34.1