View Full Version : C++ | Using NDIlib_video_frame_v2_t with other programs || Using NDI as webcam

09-25-2018, 04:36 AM
I am trying to integrate NDI with openCV in a custom C++ program
It's goal is to connect an NDI source to OpenCV and run a face detection on it with the option to change a source during runtime.

The program can connect to a specified NDI source.
The OpenCV code is already written and uses a webcam as a video source.
The NDI frames are not used in any way, just received.

The missing stage taking these NDI frames and telling the computer "Hey! this is a webcam, you can use it for anything!"
After it's registered as a webcam the OpenCV is able to capture from it easily.

How can I acheive this?
I read a little about ffmpeg and directshow but couldn't rally understand how I'm supposed to use them in this case.
Also, can this actually be acheived in a single program? or would I need to write a seperate program to route the incoming video for the OpenCV one?

Hope I managed to explain my problem,
Thanks in advance,

09-25-2018, 10:03 AM

This is more of an OpenCV issue I think, but also might be solved with the right conversion (which I have little to no knowledge on how to do)

So I've managed to get the actual pixel data like this:

NDIlib_source_t source1;
source1.p_ndi_name = "BIRDDOG-XXXXX (SDI)";
source1.p_url_address = NULL;

NDIlib_recv_connect(pNDI_recv, &source1);

NDIlib_video_frame_v2_t video_frame;
NDIlib_audio_frame_v2_t audio_frame;
NDIlib_metadata_frame_t metadata_frame;
while (true) {
switch (NDIlib_recv_capture_v2(pNDI_recv, &video_frame, &audio_frame, &metadata_frame, 1000))
case NDIlib_frame_type_none:
case NDIlib_frame_type_video:
uint8_t* data = video_frame.p_data;

But when entered into open cv, like this:

cv::Mat mat1(yres, xres, CV_8UC3, data);
cv::imshow("Display window", mat1);

I receive this error:

Exception thrown at 0x000007FEB5819AB3 (opencv_world342.dll) in
opencvtest.exe: 0xC0000005: Access violation reading location 0x0000000003F65000.

I'd really appreciate any help since I don't know where else to look anymore,
Thanks in advance again,