c++ - Recording Video from USB Cam with Qt5

Question

I am trying to record a video acquired from a webcam connect to the usb device. I am workin with Qt5.1.0 in Linux 64 bit.

I have the following code:

camera = new QCamera(this);
viewFinder = new QCameraViewfinder(this);
camera->setViewfinder(viewFinder);
recorder = new QMediaRecorder(camera,this);

QVideoEncoderSettings settings = recorder->videoSettings();
settings.setResolution(1280,720);
settings.setQuality(QMultimedia::VeryHighQuality);
settings.setFrameRate(30.0);

recorder->setVideoSettings(settings);
camera->setCaptureMode(QCamera::CaptureVideo);
camera->start();

QString name = filename + QDateTime::currentDateTime().toString("dd.MM.yy-h-m-s");
recorder->setOutputLocation(QUrl::fromLocalFile(outputpath + "/" + name + ".mp4"));
recorder->record();

When I run this code I get the following warning and error

CameraBin error: "Internal data flow error."

CameraBin error: "Could not negotiate format"

And in fact nothing is recorded.

If I change the line

   camera->setCaptureMode(QCamera::CaptureVideo);

for

   camera->setCaptureMode(QCamera::CaptureViewFinder);

No error is output, the file is generated, but it only contains one frame (fixed image)

If I remove this piece of code:

QVideoEncoderSettings settings = recorder->videoSettings();
settings.setResolution(1280,720);
settings.setQuality(QMultimedia::VeryHighQuality);
settings.setFrameRate(30.0);

I get two different errors:

CameraBin warning: "A lot of buffers are being dropped." 
CameraBin error: "Could not encode stream." 

But the video is actually recorded.

Answer 1

I'm having almost the same problem, with capturing an image. I discovered that it is only working with the default resolution 640 x 480. If you set the resolution to a higher value it does not work. I've also tried with 2 different cameras with no success, so it seems to be a qt5 problem. You could try to don't set a resolution, then you should be able to record a video, but only with the default resolution of 640 x 480.