Help capturing an image

SGaist

Hi,

There several strange (as in wrong) stuff in your code:

Why are you forcing the connection type to be DirectConnection ? There's rarely a need to specify the type of connection.
Why is savedImage a pointer rather than a QImage object ? There's usually no need for that

Additional questions:

Which version of Qt ?
On which OS ?

John1123

For DirectConnection, I added that because I thought I needed it; Ill take it off. savedImage is used in the file that calls the VideoCapture functions. I'm running QT on 6.6.3 and I'm on windows

SGaist

You should rather emit the new image from your VideoCapture class rather than fiddling with a variable that it should not know about.

John1123

Ok, ill look into emitting the image that it captures, but I still have the problem where capture() wont capture an image

SGaist

Did you try to save the image in a file to see how it looks ?

John1123

An image can't be captured in the first place, whenever I call capture it redirects to readyForCapture and isReadyForCapture changes from true to false. This also applies to captureToFile()

SGaist

Which version of Qt are you using ?
On which OS ?
With which device ?

John1123

I'm running QT on 6.6.3, I'm on windows, and I'm using my webcam

SGaist

Which version of Windows ?
What is the model of your webcam ?

John1123

my webcam is a Logi C615 HD WebCam, and im on windows 10

SGaist

Can you check again with 6.7 ?

John1123

I've checked again in 6.7 and it still doesn't work.

SGaist

Ok, then can you switch the backend to use the native rather than ffmpeg ?

John1123

How would I do that?

SGaist

It's described here.

John1123

So I've tried it, and now isReadyForCapture doesn't change to false after capture() is called but it still doesn't capture an image

SGaist

Can you provide a minimal compilable example that shows this behaviour ?

John1123

Sorry for the late reply but I'm unable to provide a minimal example. I've been digging around though and it seems to always crash after the signal imageAvailable(int id, const QVideoFrame &frame). I don't really know why that happens. I tried to do an
auto image = frame.toImage();
but this always crashes as well. I've looked into the camera example thats proved and in there it works fine

SGaist

Then I would compare what is done differently in your application based on the example.

John1123

Yeah I did that and mine looks like it should work. After looking some more though whenever I debug I get this error I do the frame.toImage().
Exception at 0x7ffa5092469e, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance)

I saw online that this happens when it tries to access an invalid address but I don't see how this happens for me. This is how I have my imageAvailable

void VideoCapture::imageAvailable(int id, const QVideoFrame &frame){
QVideoFrame frame2(frame);
frame2.map(QVideoFrame::ReadOnly);
if (frame2.isValid())
{
qDebug() << "\n" << "frame2 is valid!\n";
}
else
qDebug() << "\n" << "frame2 is NOT valid!\n";

if (frame2.isReadable())
{
    qDebug() << "\n" <<  "frame2 is readable!\n";
}
else
    qDebug() << "\n" <<  "frame2 is NOT readable!\n";

if (frame2.isMapped())
{
    qDebug() << "\n" <<  "frame2 is mapped!\n";
}
else
    qDebug() << "\n" <<  "frame2 is NOT mapped!\n";
qDebug() << "\n" <<  "frame2 map mode : " << frame2.mapMode() << "\n";
qDebug() << "\n" <<  "frame2 plane count : " << frame2.planeCount() << "\n";
qDebug() << "\n" <<  "frame2 size : " << frame2.size() << "\n";
qDebug() << "\n" <<  "frame2 pixelFormat : " << frame2.pixelFormat() << "\n";
qDebug() << "\n" <<  "frame2 mappedBytes_0 : " << frame2.mappedBytes(0) << "\n";
qDebug() << "\n" <<  "frame2 mappedBytes_1 : " << frame2.mappedBytes(1) << "\n";
qDebug() << "\n" <<  "frame2 mappedBytes_2 : " << frame2.mappedBytes(2) << "\n";
qDebug() << "\n" <<  "frame2 handleType : " << frame2.handleType() << "\n";
qDebug() << "\n" <<  "frame: " << frame << "\n";
qDebug() << "\n" <<  "frame2: " << frame2 << "\n";

qDebug() << "\n" << "before conversion\n";
frame2.toImage();
qDebug() << "\n" << "after conversion\n";

}

the printout says that its valid, readable, it mapped, map mode is 1, plane count is 2, size is 1980X1080, pixel format is Format_NV12, mapped bytes for 0 is 2073600, mapped bytes for 1 is 1036800, mapped bytes for 2 is 0, no handle.