[libcamera-devel] [PATCH v4 5/7] android: post_processor: Make post processing async

[Laurent Pinchart]

Hi Umang,

Thank you for the patch.

s/async/asynchronous/ in the subject line.

On Mon, Oct 11, 2021 at 01:05:03PM +0530, Umang Jain wrote:
> Introduce a dedicated worker class derived from libcamera::Thread.
> The worker class maintains a queue for post-processing requests
> and waits for a post-processing request to become available.
> It will process them as per FIFO before de-queuing it from the
> queue.
> 
> To get access to the source and destination buffers in the worker
> thread, we also need to save a pointer to them in the
> Camera3RequestDescriptor.
> 
> This patch also implements a flush() for the PostProcessorWorker
> class which is responsible to purge post-processing requests
> queued up while a camera is stopping/flushing.
> 
> The libcamera request completion handler CameraDevice::requestComplete()
> assumes that the request that has just completed is at the front of the
> queue. Now that the post-processor runs asynchronously, this isn't true
> anymore, a request being post-processed will stay in the queue and a new
> libcamera request may complete. Remove that assumption, and use the
> request cookie to obtain the Camera3RequestDescriptor.
> 
> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/android/camera_device.cpp |  25 +-------
>  src/android/camera_device.h   |   3 +
>  src/android/camera_stream.cpp | 108 +++++++++++++++++++++++++++++++---
>  src/android/camera_stream.h   |  39 +++++++++++-
>  4 files changed, 144 insertions(+), 31 deletions(-)
> 
> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> index eba370ea..61b902ad 100644
> --- a/src/android/camera_device.cpp
> +++ b/src/android/camera_device.cpp
> @@ -239,6 +239,7 @@ Camera3RequestDescriptor::Camera3RequestDescriptor(
>  	/* Clone the controls associated with the camera3 request. */
>  	settings_ = CameraMetadata(camera3Request->settings);
>  
> +	dest_.reset();

dest_ is a std::unique_ptr<>, its constructor will do the right thing,
you don't need to initialize it here.

>  	/*
>  	 * Create the CaptureRequest, stored as a unique_ptr<> to tie its
>  	 * lifetime to the descriptor.
> @@ -1094,28 +1095,8 @@ int CameraDevice::processCaptureRequest(camera3_capture_request_t *camera3Reques
>  
>  void CameraDevice::requestComplete(Request *request)
>  {
> -	Camera3RequestDescriptor *descriptor;
> -	{
> -		MutexLocker descriptorsLock(descriptorsMutex_);
> -		ASSERT(!descriptors_.empty());
> -		descriptor = descriptors_.front().get();
> -	}
> -
> -	if (descriptor->request_->cookie() != request->cookie()) {
> -		/*
> -		 * \todo Clarify if the Camera has to be closed on
> -		 * ERROR_DEVICE and possibly demote the Fatal to simple
> -		 * Error.
> -		 */
> -		notifyError(0, nullptr, CAMERA3_MSG_ERROR_DEVICE);
> -		LOG(HAL, Fatal)
> -			<< "Out-of-order completion for request "
> -			<< utils::hex(request->cookie());
> -
> -		MutexLocker descriptorsLock(descriptorsMutex_);
> -		descriptors_.pop();
> -		return;
> -	}
> +	Camera3RequestDescriptor *descriptor =
> +		reinterpret_cast<Camera3RequestDescriptor *>(request->cookie());
>  
>  	/*
>  	 * Prepare the capture result for the Android camera stack.
> diff --git a/src/android/camera_device.h b/src/android/camera_device.h
> index eee97516..725a0618 100644
> --- a/src/android/camera_device.h
> +++ b/src/android/camera_device.h
> @@ -59,6 +59,9 @@ struct Camera3RequestDescriptor {
>  	std::unique_ptr<CameraMetadata> resultMetadata_;
>  	libcamera::FrameBuffer *internalBuffer_;
>  
> +	std::unique_ptr<CameraBuffer> dest_;
> +	const libcamera::FrameBuffer *src_;

As mentioned in the review of the previous patch, you can have more than
one post-processed stream per request, so this won't be enough.

I'd recomment first refactoring the Camera3RequestDescriptor class and
add an internal

	struct Stream {
		camera3_stream_buffer_t buffer;
		std::unique_ptr<libcamera::FrameBuffer> frameBuffer;
	};

with the buffers_ and frameBuffers members replaced with

	std::vector<Stream> streams_;

Then you can extend the Stream structure in this patch to add the
necessary fields.

Thinking some more about it, src_ is likely not needed, as it's a
pointer to the FrameBuffer already stored in struct Stream. What you'll
need will be the ability to find the Stream instance corresponding to a
given libcamera stream, so maybe a map would be better than a vector.

It also seems like the PostProcessorWorker should move from processing
requests to processing streams, as there's one PostProcessorWorker for
each CameraStream. Maybe the struct Stream should contain a pointer to
its Camera3RequestDescriptor, that way you could pass the
Camera3RequestDescriptor::Stream pointer to CameraStream::process() and
to the post-processors, and then find the corresponding
Camera3RequestDescriptor in the completion handler.

> +
>  	camera3_capture_result_t captureResult_ = {};
>  	Status status_ = Status::Pending;
>  };
> diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> index cec07269..818ef948 100644
> --- a/src/android/camera_stream.cpp
> +++ b/src/android/camera_stream.cpp
> @@ -94,10 +94,12 @@ int CameraStream::configure()
>  		if (ret)
>  			return ret;
>  
> +		worker_ = std::make_unique<PostProcessorWorker>(postProcessor_.get());
>  		postProcessor_->processComplete.connect(
>  			this, [&](Camera3RequestDescriptor *request, PostProcessor::Status status) {
>  				cameraDevice_->streamProcessingComplete(this, request, status);
>  			});
> +		worker_->start();
>  	}
>  
>  	if (type_ == Type::Internal) {
> @@ -167,19 +169,26 @@ void CameraStream::process(const FrameBuffer &source,
>  	if (!postProcessor_)
>  		return;
>  
> -	/*
> -	 * \todo Buffer mapping and processing should be moved to a
> -	 * separate thread.
> -	 */
>  	const StreamConfiguration &output = configuration();
> -	CameraBuffer dest(*camera3Dest.buffer, output.pixelFormat, output.size,
> -			  PROT_READ | PROT_WRITE);
> -	if (!dest.isValid()) {
> +	request->dest_ = std::make_unique<CameraBuffer>(
> +		*camera3Dest.buffer, output.pixelFormat, output.size, PROT_READ | PROT_WRITE);
> +	if (!request->dest_->isValid()) {
>  		LOG(HAL, Error) << "Failed to create destination buffer";
>  		return;
>  	}
>  
> -	postProcessor_->process(source, &dest, request);
> +	request->src_ = &source;
> +
> +	/* Push the postProcessor request to the worker queue. */
> +	worker_->queueRequest(request);
> +}
> +
> +void CameraStream::flush()
> +{
> +	if (!postProcessor_)
> +		return;
> +
> +	worker_->flush();
>  }
>  
>  FrameBuffer *CameraStream::getBuffer()
> @@ -209,3 +218,86 @@ void CameraStream::putBuffer(FrameBuffer *buffer)
>  
>  	buffers_.push_back(buffer);
>  }
> +
> +CameraStream::PostProcessorWorker::PostProcessorWorker(PostProcessor *postProcessor)
> +	: postProcessor_(postProcessor)
> +{
> +}
> +
> +CameraStream::PostProcessorWorker::~PostProcessorWorker()
> +{
> +	{
> +		libcamera::MutexLocker lock(mutex_);
> +		state_ = State::Stopped;
> +	}
> +
> +	cv_.notify_one();
> +	wait();
> +}
> +
> +void CameraStream::PostProcessorWorker::start()
> +{
> +	{
> +		libcamera::MutexLocker lock(mutex_);
> +		state_ = State::Running;
> +	}
> +
> +	Thread::start();
> +}
> +
> +void CameraStream::PostProcessorWorker::queueRequest(Camera3RequestDescriptor *request)
> +{
> +	{
> +		MutexLocker lock(mutex_);
> +		ASSERT(state_ == State::Running);
> +		requests_.push(request);
> +	}
> +	cv_.notify_one();
> +}
> +
> +void CameraStream::PostProcessorWorker::run()
> +{
> +	MutexLocker locker(mutex_);
> +
> +	while (1) {
> +		cv_.wait(locker, [&] {
> +			return state_ != State::Running || !requests_.empty();
> +		});
> +
> +		if (state_ != State::Running)
> +			break;
> +
> +		Camera3RequestDescriptor *descriptor = requests_.front();
> +		requests_.pop();
> +		locker.unlock();
> +
> +		postProcessor_->process(*descriptor->src_, descriptor->dest_.get(),
> +					descriptor);
> +
> +		locker.lock();
> +	}
> +
> +	if (state_ == State::Flushing) {
> +		while (!requests_.empty()) {
> +			postProcessor_->processComplete.emit(requests_.front(),
> +							     PostProcessor::Status::Error);
> +			requests_.pop();
> +		}
> +		state_ = State::Stopped;
> +		locker.unlock();
> +		cv_.notify_one();
> +	}
> +}
> +
> +void CameraStream::PostProcessorWorker::flush()
> +{
> +	libcamera::MutexLocker lock(mutex_);
> +	state_ = State::Flushing;
> +	lock.unlock();
> +	cv_.notify_one();
> +
> +	lock.lock();
> +	cv_.wait(lock, [&] {
> +		return state_ == State::Stopped;
> +	});
> +}
> diff --git a/src/android/camera_stream.h b/src/android/camera_stream.h
> index a0c5f166..e410f35d 100644
> --- a/src/android/camera_stream.h
> +++ b/src/android/camera_stream.h
> @@ -7,21 +7,26 @@
>  #ifndef __ANDROID_CAMERA_STREAM_H__
>  #define __ANDROID_CAMERA_STREAM_H__
>  
> +#include <condition_variable>
>  #include <memory>
>  #include <mutex>
> +#include <queue>
>  #include <vector>
>  
>  #include <hardware/camera3.h>
>  
> +#include <libcamera/base/thread.h>
> +
>  #include <libcamera/camera.h>
>  #include <libcamera/framebuffer.h>
>  #include <libcamera/framebuffer_allocator.h>
>  #include <libcamera/geometry.h>
>  #include <libcamera/pixel_format.h>
>  
> +#include "post_processor.h"
> +
>  class CameraDevice;
>  class CameraMetadata;
> -class PostProcessor;
>  
>  struct Camera3RequestDescriptor;
>  
> @@ -125,8 +130,38 @@ public:
>  		     Camera3RequestDescriptor *request);
>  	libcamera::FrameBuffer *getBuffer();
>  	void putBuffer(libcamera::FrameBuffer *buffer);
> +	void flush();
>  
>  private:
> +	class PostProcessorWorker : public libcamera::Thread
> +	{
> +	public:
> +		enum class State {
> +			Stopped,
> +			Running,
> +			Flushing,
> +		};
> +
> +		PostProcessorWorker(PostProcessor *postProcessor);
> +		~PostProcessorWorker();
> +
> +		void start();
> +		void queueRequest(Camera3RequestDescriptor *request);
> +		void flush();
> +
> +	protected:
> +		void run() override;
> +
> +	private:
> +		PostProcessor *postProcessor_;
> +
> +		libcamera::Mutex mutex_;
> +		std::condition_variable cv_;
> +
> +		std::queue<Camera3RequestDescriptor *> requests_;
> +		State state_;
> +	};
> +
>  	int waitFence(int fence);
>  
>  	CameraDevice *const cameraDevice_;
> @@ -143,6 +178,8 @@ private:
>  	 */
>  	std::unique_ptr<std::mutex> mutex_;
>  	std::unique_ptr<PostProcessor> postProcessor_;
> +
> +	std::unique_ptr<PostProcessorWorker> worker_;
>  };
>  
>  #endif /* __ANDROID_CAMERA_STREAM__ */

-- 
Regards,

Laurent Pinchart