Fixed number of frames video buffer

Hi,

I get a new picture from my camera every 100ms. I want to store some frames to understand what happens before and after an event.

How can I implement a buffer that continuously saves the last 30 pictures?

The last lines of code shows what I want to do.

Any help with the saving of frames after the trigger event is also appreciated, but I think I can do it.

while true
    %get video
    I = videoinput('winvideo', 2, 'YUY2_1280x720');
    I.ReturnedColorspace = 'rgb';
    I = getsnapshot(I);
    vid.ROIPosition = [585 400 648 313]; % crop the image to smaller ROI
    
    % preprosess the image
    I = imresize(I,frameSize); 
    I= imsubtract(I,background);
    I = imadjust(I,[low high]);
  %----------------------------------- save last 30 frames of I
  %  if something happens 
  % save 30 more more frames 
  % merge the two videos
end 

[Walter Roberson]

https://www.mathworks.com/help/imaq/logging-data-to-disk.html

Built in logging to disk mode.

[Eirik Furuholt]

Hello Walter,

Thank you for your reply.

In the link you provided I cannot see a solution to logging just the last few seconds. This camera will run for weeks and I will quickly run out of disk space if I log continuously. Could you please explain further how I can log the last few seconds without losing frames?

Best regards

Eirik F.

Answer 1

[Shiva Kalyan Diwakaruni]

Hi,

You can try Creating a video reader object and read one or more video frames using the frame indices.

below is the link to documentation

https://www.mathworks.com/help/matlab/ref/videoreader.read.html

Hope it helps.