[libcamera-devel] [PATCH v1 2/3] ipa: raspberrypi: Better heruistics for calculating Unicam timeout

[Jacopo Mondi]

Hi Naush

On Thu, Feb 23, 2023 at 12:49:56PM +0000, Naushir Patuck via libcamera-devel wrote:
> Date: Thu, 23 Feb 2023 12:49:56 +0000
> From: Naushir Patuck <naush at raspberrypi.com>
> To: libcamera-devel at lists.libcamera.org
> Subject: [PATCH v1 2/3] ipa: raspberrypi: Better heruistics for calculating
>  Unicam timeout
> X-Mailer: git-send-email 2.25.1
>
> The existing mechanism of setting a timeout value simply uses the
> maximum possible frame length advertised by the sensor mode. This can be
> problematic when, for example, the IMX477 sensor can use a frame length
> of over 600 seconds. However, for typical usage the frame length will

Is this a typo or do we have exposures time of 10 minutes ?

> never go over several 100s of milliseconds, making the timeout very
> impractical.
>
> Store a list of the last 10 frame length values requested by the AGC. On
> startup, and at the end of every frame, take the maximum frame length
> value from this list and return that to the pipeline handler through the
> setCameraTimeoutValue() signal. This allows the timeout value to better
> track the actual sensor usage.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  src/ipa/raspberrypi/raspberrypi.cpp | 33 +++++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index f6826bf27fe1..b8fe0c002a13 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -8,6 +8,7 @@
>  #include <algorithm>
>  #include <array>
>  #include <cstring>
> +#include <deque>
>  #include <fcntl.h>
>  #include <math.h>
>  #include <stdint.h>
> @@ -64,6 +65,9 @@ using utils::Duration;
>  /* Number of metadata objects available in the context list. */
>  constexpr unsigned int numMetadataContexts = 16;
>
> +/* Number of frame length times to hold in the queue. */
> +constexpr unsigned int FrameLengthsQueueSize = 10;
> +
>  /* Configure the sensor with these values initially. */
>  constexpr double defaultAnalogueGain = 1.0;
>  constexpr Duration defaultExposureTime = 20.0ms;
> @@ -155,6 +159,7 @@ private:
>  	void fillDeviceStatus(const ControlList &sensorControls, unsigned int ipaContext);
>  	RPiController::StatisticsPtr fillStatistics(bcm2835_isp_stats *stats) const;
>  	void processStats(unsigned int bufferId, unsigned int ipaContext);
> +	void setCameraTimeoutValue();
>  	void applyFrameDurations(Duration minFrameDuration, Duration maxFrameDuration);
>  	void applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls);
>  	void applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls);
> @@ -220,6 +225,9 @@ private:
>
>  	/* Maximum gain code for the sensor. */
>  	uint32_t maxSensorGainCode_;
> +
> +	/* Track the frame length times over FrameLengthsQueueSize frames. */
> +	std::deque<Duration> frameLengths_;
>  };
>
>  int IPARPi::init(const IPASettings &settings, bool lensPresent, IPAInitResult *result)
> @@ -294,6 +302,7 @@ void IPARPi::start(const ControlList &controls, StartConfig *startConfig)
>  		ControlList ctrls(sensorCtrls_);
>  		applyAGC(&agcStatus, ctrls);
>  		startConfig->controls = std::move(ctrls);
> +		setCameraTimeoutValue();
>  	}
>
>  	/*
> @@ -340,8 +349,6 @@ void IPARPi::start(const ControlList &controls, StartConfig *startConfig)
>  	}
>
>  	startConfig->dropFrameCount = dropFrameCount_;
> -	const Duration maxSensorFrameDuration = mode_.maxFrameLength * mode_.maxLineLength;
> -	setCameraTimeout.emit(maxSensorFrameDuration.get<std::milli>());
>
>  	firstStart_ = false;
>  	lastRunTimestamp_ = 0;
> @@ -1434,9 +1441,20 @@ void IPARPi::processStats(unsigned int bufferId, unsigned int ipaContext)
>  		applyAGC(&agcStatus, ctrls);
>
>  		setDelayedControls.emit(ctrls, ipaContext);
> +		setCameraTimeoutValue();
>  	}
>  }
>
> +void IPARPi::setCameraTimeoutValue()
> +{
> +	/*
> +	 * Take the maximum value of the exposure queue as the camera timeout
> +	 * value to pass back to the pipe line handler.
> +	 */
> +	auto max = std::max_element(frameLengths_.begin(), frameLengths_.end());
> +	setCameraTimeout.emit(max->get<std::milli>());

I would store the last set timeout and only emit the signal when it
changes. Am I wrong or the signal is emitted every frame ?

> +}
> +
>  void IPARPi::applyAWB(const struct AwbStatus *awbStatus, ControlList &ctrls)
>  {
>  	LOG(IPARPI, Debug) << "Applying WB R: " << awbStatus->gainR << " B: "
> @@ -1522,6 +1540,17 @@ void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList &ctrls)
>  	 */
>  	if (mode_.minLineLength != mode_.maxLineLength)
>  		ctrls.set(V4L2_CID_HBLANK, static_cast<int32_t>(hblank));
> +
> +	/*
> +	 * Store the frame length times in a circular queue, up-to FrameLengthsQueueSize
> +	 * elements. This will be used to advertise a camera timeout value to the
> +	 * pipeline handler.
> +	 */
> +	if (frameLengths_.size() == FrameLengthsQueueSize)
> +		frameLengths_.pop_front();
> +
> +	frameLengths_.push_back(helper_->exposure(vblank + mode_.height,
> +						  helper_->hblankToLineLength(hblank)));

Alternatively you can push_front() and resize(FrameLengthsQueueSize).
If I read the documentation right
- When size < FrameLengthsQueueSize the deque is expanded to
  FrameLengthsQueueSize with default constructed elements (0)
- When size > the last elements are invalidated

Complexity is probably similar ?

Alternatively you can also construct the deque with 10 elements
initialized to 0 and unconditionally pop_front + push_back

>  }
>
>  void IPARPi::applyDG(const struct AgcStatus *dgStatus, ControlList &ctrls)
> --
> 2.25.1
>