[libcamera-devel] [PATCH] ipa: raspberrypi: Rate-limit the controller algorithms
David Plowman
david.plowman at raspberrypi.com
Thu Apr 15 18:01:11 CEST 2021
Hi Naush
On Thu, 15 Apr 2021 at 15:40, Naushir Patuck <naush at raspberrypi.com> wrote:
>
> Hi David,
>
> Thank you for your feedback.
>
> On Thu, 15 Apr 2021 at 15:26, David Plowman <david.plowman at raspberrypi.com> wrote:
>>
>> Hi Naush
>>
>> Thanks for this patch, I think it's a good idea!
>>
>> On Thu, 15 Apr 2021 at 11:18, Naushir Patuck <naush at raspberrypi.com> wrote:
>> >
>> > The controller algorithms currently run on every frame provided to the
>> > IPA by the pipeline handler. This may be undesirable for very fast fps
>> > operating modes where it could significantly increase the computation
>> > cycles (per unit time) without providing any significant changes to the
>> > IQ parameters. The added latencies could also cause dropped frames.
>> >
>> > Pass the FrameBuffer timestamp to the IPA through the controls. This
>> > timestamp will be used to rate-limit the controller algorithms to run
>> > with a minimum inter-frame time given by a compile time constant,
>> > currently set to 16.66ms.
>> >
>> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
>> > ---
>> > src/ipa/raspberrypi/raspberrypi.cpp | 39 ++++++++++++++++++-
>> > .../pipeline/raspberrypi/raspberrypi.cpp | 5 +++
>> > 2 files changed, 42 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
>> > index dad6395f0823..aa071473d6e7 100644
>> > --- a/src/ipa/raspberrypi/raspberrypi.cpp
>> > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
>> > @@ -61,6 +61,14 @@ constexpr unsigned int DefaultExposureTime = 20000;
>> > constexpr double defaultMinFrameDuration = 1e6 / 30.0;
>> > constexpr double defaultMaxFrameDuration = 1e6 / 0.01;
>> >
>> > +/*
>> > + * Determine the minimum allowable inter-frame duration (in us) to run the
>> > + * controller algorithms. If the pipeline handler provider frames at a rate
>> > + * higher than this, we rate-limit the controller prepare() and process() calls
>>
>> It wasn't clear to me whether prepare() was being rate-limited too?
>> More on that below...
>>
>> > + * to lower than or equal to this rate.
>> > + */
>> > +constexpr double controllerMinFrameDuration = 1e6 / 60.0;
>> > +
>> > LOG_DEFINE_CATEGORY(IPARPI)
>> >
>> > class IPARPi : public ipa::RPi::IPARPiInterface
>> > @@ -68,7 +76,7 @@ class IPARPi : public ipa::RPi::IPARPiInterface
>> > public:
>> > IPARPi()
>> > : controller_(), frameCount_(0), checkCount_(0), mistrustCount_(0),
>> > - lsTable_(nullptr), firstStart_(true)
>> > + lastRunTimestamp_(0), lsTable_(nullptr), firstStart_(true)
>> > {
>> > }
>> >
>> > @@ -145,6 +153,12 @@ private:
>> > /* How many frames we should avoid running control algos on. */
>> > unsigned int mistrustCount_;
>> >
>> > + /* Frame timestamp for the last run of the controller. */
>> > + uint64_t lastRunTimestamp_;
>> > +
>> > + /* Do we run a Controller::process() for this frame? */
>> > + bool processPending_;
>> > +
>> > /* LS table allocation passed in from the pipeline handler. */
>> > FileDescriptor lsTableHandle_;
>> > void *lsTable_;
>> > @@ -406,7 +420,7 @@ void IPARPi::signalStatReady(uint32_t bufferId)
>> > {
>> > if (++checkCount_ != frameCount_) /* assert here? */
>> > LOG(IPARPI, Error) << "WARNING: Prepare/Process mismatch!!!";
>> > - if (frameCount_ > mistrustCount_)
>> > + if (processPending_ && frameCount_ > mistrustCount_)
>> > processStats(bufferId);
>>
>> Although not related directly to this bit of code, I wonder whether we
>> have an interaction between skipping the algorithms and the frame
>> dropping that we do at startup (while waiting for those algorithms to
>> converge)? i.e. are we elapsing those "drop frames" at a faster rate
>> than the IPA can run in order to achieve convergence during those
>> frames?
>
>
> Yes, this is possible. Perhaps I should change the logic a bit so that we
> run controller prepare()/process() on every frame when frameCount_ <= mistrustCount_.
> This is not going to cause any problems, as mistrustCount_ is only a few frames.
> What do you think?
I'm thinking that might not be quite right. Presumably we might want
to consider running the algos more until the PH reaches its
dropFrameCount (or whatever it's called). Presumably that number came
from the IPA originally in some way - so we must know what it is,
right?
>
>>
>>
>> >
>> > reportMetadata();
>> > @@ -894,6 +908,7 @@ void IPARPi::returnEmbeddedBuffer(unsigned int bufferId)
>> >
>> > void IPARPi::prepareISP(const ipa::RPi::ISPConfig &data)
>> > {
>> > + int64_t frameTimestamp = data.controls.get(controls::draft::SensorTimestamp);
>> > struct DeviceStatus deviceStatus = {};
>> > bool success = false;
>> >
>> > @@ -919,6 +934,26 @@ void IPARPi::prepareISP(const ipa::RPi::ISPConfig &data)
>> > fillDeviceStatus(exposureLines, gainCode, deviceStatus);
>> > }
>> >
>> > + if (lastRunTimestamp_ &&
>> > + frameTimestamp - lastRunTimestamp_ < controllerMinFrameDuration * 1e3) {
>> > + /*
>> > + * Ensure we update the controller metadata with the new frame's
>> > + * exposure/gain values so that the correct values are returned
>> > + * out in libcamera metadata later on. All other metadata values
>> > + * must remain the same as the last frame.
>> > + */
>> > + rpiMetadata_.Set("device.status", deviceStatus);
>> > + processPending_ = false;
>> > + LOG(IPARPI, Debug) << "Rate-limiting the controller! inter-frame duration: "
>> > + << frameTimestamp - lastRunTimestamp_
>> > + << ", min duration "
>> > + << controllerMinFrameDuration * 1e3;
>> > + return;
>> > + }
>> > +
>> > + lastRunTimestamp_ = frameTimestamp;
>> > + processPending_ = true;
>> > +
>> > ControlList ctrls(ispCtrls_);
>> >
>> > rpiMetadata_.Clear();
>>
>> So here I'm inferring that we don't skip prepare(). Mostly I think
>> this is fine as prepare() does much less work. Probably ALSC is the
>> worst as it interpolates lens shading tables.
>
>
> I stopped running prepare() as I wanted to avoid the whole cycle of pulling
> out controller metadata, setting ControlLists and writing controls to the v4l2 device.
> All of this probably adds quite a bit of latency that we probably do not need.
> Besides, running prepare() without running process() durning a normal
> (or steady state) run seems a bit pointless to me, unless I missed something?
>
>>
>> One little corner we might want to watch out for is something like the
>> AE/AGC lock count. This counts in Agc::Prepare() how long things
>> appear to be "steady", and if Process() runs less often than
>> Prepare(), it seems possible that Prepare() may see things as steadier
>> than they really are. Maybe we're ok, but it's just something to
>> check.
Ah OK, if you avoid Prepare() and Process() together then there can't
be a problem. Maybe I didn't understand exactly what was happening
here.
>>
>> Also, I have a feeling we may get conflicts here with the
>> CamHelper::Prepare/Process patch. Now it's a race to see who gets in
>> first! :)
>
>
> Yes, we do have a race on our hands here.
Hmm, can I grab the Raspberry Pi IPA mutex, please?!!
Thanks
David
>
> Regards,
> Naush
>
>
>>
>>
>> Thanks!
>>
>> David
>>
>> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
>> > index 2a917455500f..9cf9c8c6cebd 100644
>> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
>> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
>> > @@ -1414,6 +1414,11 @@ void RPiCameraData::unicamBufferDequeue(FrameBuffer *buffer)
>> > * DelayedControl and queue them along with the frame buffer.
>> > */
>> > ControlList ctrl = delayedCtrls_->get(buffer->metadata().sequence);
>> > + /*
>> > + * Add the frame timestamp to the ControlList for the IPA to use
>> > + * as it does not receive the FrameBuffer object.
>> > + */
>> > + ctrl.set(controls::draft::SensorTimestamp, buffer->metadata().timestamp);
>> > bayerQueue_.push({ buffer, std::move(ctrl) });
>> > } else {
>> > embeddedQueue_.push(buffer);
>> > --
>> > 2.25.1
>> >
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