[libcamera-devel,4/4] qcam: Update window title with FPS

1584 diff mbox series

Provide an average FPS in the QCam title bar to show the current rate of
frame processing.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/qcam/main_window.cpp | 23 ++++++++++++++++++++---
 src/qcam/main_window.h   |  4 +++-
 2 files changed, 23 insertions(+), 4 deletions(-)

Hi Kieran,

Thank you for the patch.

On Tue, Jul 02, 2019 at 12:48:41PM +0100, Kieran Bingham wrote:
> Provide an average FPS in the QCam title bar to show the current rate of
> frame processing.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/qcam/main_window.cpp | 23 ++++++++++++++++++++---
>  src/qcam/main_window.h   |  4 +++-
>  2 files changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
> index 61d7aa9469f0..c093bd0c809e 100644
> --- a/src/qcam/main_window.cpp
> +++ b/src/qcam/main_window.cpp
> @@ -26,7 +26,7 @@ MainWindow::MainWindow(const OptionsParser::Options &options)
>  {
>  	int ret;
>  
> -	setWindowTitle();
> +	setWindowTitle("");

Ah now I see why you have added a MainWindow::setWindowTitle() method.

>  	viewfinder_ = new ViewFinder(this);
>  	setCentralWidget(viewfinder_);
>  	viewfinder_->setFixedSize(500, 500);
> @@ -52,10 +52,11 @@ MainWindow::~MainWindow()
>  	CameraManager::instance()->stop();
>  }
>  
> -void MainWindow::setWindowTitle()
> +void MainWindow::setWindowTitle(QString fps)

How about passing the fps as a floating point number instead of a
string, and doing the conversion internally ? Otherwise you should pass
a const QString &.

>  {
>  	QMainWindow::setWindowTitle("QCam : "
> -		+ QString::fromStdString(libcamera::version.toString()));
> +		+ QString::fromStdString(libcamera::version.toString())
> +		+ " (" + fps + ")");
>  }
>  
>  int MainWindow::openCamera()
> @@ -152,6 +153,9 @@ int MainWindow::startCapture()
>  		requests.push_back(request);
>  	}
>  
> +	firstFrameTime = 0;
> +	framesCaptured = 0;
> +
>  	ret = camera_->start();
>  	if (ret) {
>  		std::cout << "Failed to start capture" << std::endl;
> @@ -215,6 +219,19 @@ void MainWindow::requestComplete(Request *request,
>  
>  	display(buffer);
>  
> +	if (firstFrameTime == 0)
> +		firstFrameTime = buffer->timestamp();
> +
> +	uint64_t duration = buffer->timestamp() - firstFrameTime;
> +	if (duration)
> +		fps = framesCaptured * 1000000000.0 / duration;
> +	else
> +		fps = 0.0;
> +
> +	setWindowTitle(QString::number(fps, 'f', 2) + " fps");

I think we should update the title for every frame, but only
periodically (x times per second, which doesn't require a timer but can
simply use a difference between the current timestamp and the last
update timestamp here). Otherwise it would flash a bit too fast to be
really readable.

I think you should also compute the fps using a moving average instead
of an average since the beginning of the stream, as the latter isn't
that meaningful.

> +
> +	framesCaptured++;
> +
>  	request = camera_->createRequest();
>  	if (!request) {
>  		std::cerr << "Can't create request" << std::endl;
> diff --git a/src/qcam/main_window.h b/src/qcam/main_window.h
> index b30a86768efc..792f89c2d831 100644
> --- a/src/qcam/main_window.h
> +++ b/src/qcam/main_window.h
> @@ -33,7 +33,7 @@ public:
>  	~MainWindow();
>  
>  private:
> -	void setWindowTitle();
> +	void setWindowTitle(QString info);

You have name the parameter fps above.

>  
>  	int openCamera();
>  
> @@ -49,6 +49,8 @@ private:
>  	std::shared_ptr<Camera> camera_;
>  	bool isCapturing_;
>  	std::unique_ptr<CameraConfiguration> config_;
> +	uint64_t firstFrameTime;
> +	uint32_t framesCaptured;
>  
>  	ViewFinder *viewfinder_;
>  };