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

[Dave Stevenson]

Hi Jacopo

On Wed, 1 Mar 2023 at 15:17, Jacopo Mondi via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> 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 ?

No typo.

IMX477 will do FRAME_LENGTH of 0xFFFF << 7 = 8388480 lines, and
LINE_LENGTH up to 0xfff0 (65520). PIXEL_RATE of 840MPix/s, gives
654.3secs, or 10.9mins.
Exposure has to be 22lines shorter than that max, but for timeouts
we're really talking frame times instead of exposure times.

IMX708 will also do FRAME_LENGTH of 0xFFFF << 7 = 8388480 lines, but
LINE_LENGTH is currently fixed at 0x3d20 (15648) for full res.
PIXEL_RATE of 595200000 pixels, gives max frame time of 220 seconds or
3.67mins.

:-)

  Dave

> > 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
> >