Getting duplicate frame

[HackersSpirit]

I using following model of basler camera: acA1920-40uc
I have connect my camera to controller which moves in a particular direction and capture images.
If i move camera from A to B to C. It happens that i get similar image for all the location.
I have tried camera->StartGrabbing(GrabStrategy_LatestImageOnly); but i still get duplicate frame. I have used similar logic in python and issue does not occur.
I can use grabOne and software trigger but it creates an extra delay to fetch the frame which is not desirable in my case.
Sharing the cpp and python code. Please let me know in case of any issues.

Cpp:
Initialization:

void PrimaryCamera::initializeCamera()
{
    try
    {
        camera = new Pylon::CInstantCamera(CTlFactory::GetInstance().CreateFirstDevice());
        cout<<"Using Device"<<camera->GetDeviceInfo().GetModelName()<<endl;
        camera->MaxNumBuffer = 1;
        formatConverter.OutputPixelFormat = PixelType_BGR8packed;
        camera->Open();
        camera->StartGrabbing(GrabStrategy_LatestImageOnly);
        cout<<"\nCamera Initialized Successfully"<<endl;
    }catch(GenICam::GenericException &e) {
        cerr << "An exception occurred." << endl  << e.GetDescription() << endl;

    }

}

Capture Frame:

cv::Mat PrimaryCamera::captureBaslerFrame()
{
    if(camera->IsGrabbing()){
        camera->RetrieveResult(500, ptrGrabResult, TimeoutHandling_ThrowException);
        if (ptrGrabResult->GrabSucceeded()){
            formatConverter.Convert(pylonImage,ptrGrabResult);
            return cv::Mat(ptrGrabResult->GetHeight(),ptrGrabResult->GetWidth(), CV_8UC3,(uint8_t *)pylonImage.GetBuffer());

        }
    }else{
        cout<<"Currently camera is not grabbing frames"<<endl;
    }
}

Python:

try:
    camera = pylon.InstantCamera(pylon.TlFactory.GetInstance().CreateFirstDevice())
    print("Using device ", camera.GetDeviceInfo().GetModelName())
except:
    print("Oops!", sys.exc_info()[0], "occured.")
    sys.exit('no camera port found')

# Grabing Continusely (video) with minimal delay
camera.StartGrabbing(pylon.GrabStrategy_LatestImageOnly)
converter = pylon.ImageFormatConverter()
# # converting to opencv bgr format
converter.OutputPixelFormat = pylon.PixelType_BGR8packed
converter.OutputBitAlignment = pylon.OutputBitAlignment_MsbAligned


def grab_img():
    grabResult = camera.RetrieveResult(1000, pylon.TimeoutHandling_ThrowException)
    if grabResult.GrabSucceeded():
        image = converter.Convert(grabResult,)
        img = image.GetArray()
        grabResult.Release()
    return img

[thiesmoeller]

• the pylon APIs you use can't generate duplicate data, as there is a strict buffer management.
• As I don't see any trigger configuration, how to you synchronize the motion with the moments you want to capture an image.
• Without trigger the camera is free-running at 40fps with your model. So each frame you get is just taken 1/40 s apart from the frame before

[HackersSpirit]

@thiesmoeller : Thanks for the response.

• Actually i haven't used software or hardware trigger because the time taken by s/w trigger gives me frame in 100 to 120 millisec delay which is not desirable in my case and i haven't tried the hardware trigger.

• Secondly i for synchronization i move my controller by some distance give some time dealy for controller to stablize and then grab the frame.

• Following the same step in python give me distint image at each where as in cpp i get the same image/
  If you like i will share the output of both cpp and python.

-Please find the code below for clarity

-Python:

for i in range(3):
    #Writing data to serial port to move the controller by given distace
    ser.write(b"G0 X200 \n")
    ser.read()
    time.sleep(.2)
    img = grab_img()
    cv2.imwrite("path to save the image"+str(i)+".jpeg",img

Cpp

for(int i =0; i<3; i++)
     {
       //Writing serial data to the controller
         serialPort->writeDataWithAck("G0 X200");
         QTest::qSleep(200);
         Mat sample = getBaslerFrame();
         imwrite("path to save image"+to_string(i)+".jpeg",sample);
       }

Please let me know in case of any issue.
Can there be a possibilty burst mode is being selected when i start the camera ?
All the parameter changes were done using the pylon software and none is being set in the program.
But i was thinking any such possibility.

[HackersSpirit]

@thiesmoeller @basler: one observation which i would like to share. When i run the above getbasler frame in while loop and continuously fetch the frames duplicate image cannot be seen seen. May be a sort of workaround but exactly haven’t figured the core issue.

[thiesmoeller]

If you don't won't to synchronize with external hw trigger, but know the exakt timing
of your movement use
https://docs.baslerweb.com/#t=en%2Facquisition_frame_rate.htm to configure a larger spacing between your frames

[HackersSpirit]

@thiesmoeller : Thanks for the help. Finally i was able to find out the issue.
Actually earlier i was running a git example inorder to fetch the frame. When i went through the document i found out the problem was in initialization:
camera->MaxNumBuffer = 1;
The max size of the buffer the more samples can be stored.
This also answers the question why i was getting no repeated frame after continuously fetching the frame.