DirectShow and device property dialogs

unDerTech · wrote on 21 Jul 2020, 09:07

Hello, I need to show the dialogs page of a Video Device from Qt.
I need in order to use OPENCV and I need to configure the capture device to PAL_B, by default is NTSC.

It's possible to do this?

Thanks
Undy

SGaist · wrote on 21 Jul 2020, 18:10

Hi and welcome to devnet,

How will you be configuring these devices ?

unDerTech · wrote on 22 Jul 2020, 07:26

Hello, and thanks for answering.

That I need is to enum the video capture devices in a system, select one and call his property page.
This page, I think, can have up to 3 subpages, source, format and display.

I want to use opencv and QT and with a webcam works ok, but a camera with capture device, I need to configure it before use.
For example, the video capture device by default is configured to NTSC and my camera is PAL_B, opencv can't change this. I think I need call driver standard DSHOW config pages to do this.

Do you understand me?
Thanks

SGaist · wrote on 22 Jul 2020, 18:33

How are you doing it currently ?

unDerTech · wrote on 23 Jul 2020, 09:47

Currently only opening de camera. Previously with a video app, I configure de driver to PAL_B.
I can't open this dialog from Qt, pyrhon etc.

OpenCV is ok to work with webcams, but to work with video capture devices......... These devices need to configure their parameters in order to work.

Thanks

Bonnie · wrote on 23 Jul 2020, 13:59

If you open the device by opencv, then I don't think Qt can configure it.
Also, I don't find any Qt API that can show DSHOW config dialog.

Instead, I find that there is CAP_PROP_SETTINGS in cv::VideoCaptureProperties.

CAP_PROP_SETTINGS
Python: cv.CAP_PROP_SETTINGS

Pop up video/camera filter dialog (note: only supported by DSHOW backend currently. The property value is ignored)

Maybe you should have a look at that?

unDerTech · wrote on 24 Jul 2020, 09:02

Hi, effectively. Qt can not configure it, but neither can OpenCV .
CAP_PROP_SETTING have not access to these configurations.

The only way is by directshow API, (or VFW).
I have been able to find several examples in c++ but I don't unsterstand them and they don't work.

I'm using Qt with MVS2017 64 bits.

SGaist · wrote on 24 Jul 2020, 18:16

What example are these ?

unDerTech · wrote on 24 Jul 2020, 19:18

I am reading about..........

https://docs.microsoft.com/en-us/windows/win32/directshow/display-vfw-capture-dialog-boxes

https://stackoverflow.com/questions/54707428/how-to-show-video-capture-filter-dialog-camera-settings-like-brightness-exposu

etc etc

unDerTech · wrote on 27 Jul 2020, 07:31

Any idea?

Thanks