Help capturing an image

[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.

[JonB]

@John1123 said in Help capturing an image:

Exception at 0x7ffa5092469e, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance)

This is a "first chance" exception. So far as I understand it, that is an MSVC-ism and is to be ignored as not relevant. Do you have any other problem/diagnostic other than a first chance exception?

[John1123]

Hi Jon, I don't have any other problem. When I build I don't get anything and when I run with the debugger on, that's the only issue that I have

[JonB]

@John1123 Then (assuming nothing actually goes wrong) ignore it!

[John1123]

That makes sense but I'm wondering if I should ignore it though, because when I run it, it crashes there