MATLAB - imwrite error in certain folders - matlab

Question

this is my first question so I hope I am writing in the right place.
I am currently working with a Grasshopper3 camera, model: GS3-U3-50S5M-C from Point Grey Research connected to MATLAB.
I am recording a lot of frames at a time in grayscale and in order to avoid filling up my memory I would like to move some of the frames to my disk as stacked TIFFs during the recordings. The stacked TIFF format is needed for other programs used.
I am doing this by moving the recorded frames from the camera to the workspace using getdata. This creates a 4-D uint8 object containing height, width, color plane and frame number of the frames. In order to save the frames as a stacked TIFF I use a for loop with imwrite to save one frame at a time as shown below. However when I do this I most often get the error:
Error using imwrite (line 454) Unable to open file "C:\Users\My_User\Desktop\CraneStuff3\Name.tif" for writing. You might not have write permission.
When this happens MATLAB has typically saved some of the frames, e.g. if I have recorded 500 frames it might save 300 before giving me the error. Sometimes it manages to save every frame with no error, sometimes it only saves 30 frames before failing. I do not understand how it can save some frames and then claim that it cannot open the file for writing.
I have noticed, however, that if I instead save the file in "C:\Users\My_User\Documents\MATLAB" it seems to never give any error and save every frame as wanted.
Does anyone know why this is the case or how I can fix my problem?
I have included my code below here.
Note: I tried saving the frames as a .mat-file. To do this I had to use version '-v7.3' in save.
Thank you advance.
% Connect to camera:
vid = videoinput('pointgrey',1,'F7_Mono8_2448x2048_Mode0');
vid.TriggerRepeat = 100;
vid.FrameGrabInterval = 1;
% Make a recording:
start(vid)
pause(50)
stop(vid)
% Get data from camera to workspace:
data = getdata(vid,vid.FramesAvailable);
% Save data to disk one image at a time:
num = size(data);
output_name = fullfile('C:\Users\My_User\Desktop\CraneStuff3', ['Name' '.tif']);
for k = 1:num(4)
imwrite(data(:,:,:,k),output_name,'WriteMode','append');
end

Answer 1

One possible solution is to try saving each of the frames separately into a tiff file.
If you save a .mat file, better use savefast