i want to do background subtraction and then save edited frames in a video but I cant go through the last part!

clear all;
close all;
%warning('OFF','all')
clc;
thresh = 0.05;%originalmente era 40 pero a mi me funciona con este valor 0.005 aproximadamente
c=0;
 
filename = 'YourAVI4.avi';
hvfr = vision.VideoFileReader(filename, 'ImageColorSpace', 'RGB');
v = VideoWriter('matin');
image = step(hvfr); 
 
% ----------------------- frame size variables -----------------------
 
bg = image; % read in 1st frame as background frame
open(v)
 
bg_bw = rgb2gray(bg); % convert background to greyscale
% ----------------------- set frame size variables -----------------------
fr_size = size(bg); 
width = fr_size(2);
height = fr_size(1);
fg = zeros(height, width);
while ~isDone(hvfr)
fr = step(hvfr);
c = c+1;
end
% --------------------- process frames -----------------------------------
while ~isDone(hvfr)
fr = step(hvfr);
 
fr_bw = rgb2gray(fr); % convert frame to grayscale 
fr_diff = abs(double(fr_bw) - double(bg_bw));
for j=1:width 
for k=1:height
if ((fr_diff(k,j) > thresh))
fg(k,j) = 255;
else
fg(k,j) = 0;
end
end
end
bg_bw = fr_bw; %to consider next two frames as candidates
writeVideo(v,fg)
%figure(1),subplot(3,1,1),imshow(fr)
%subplot(3,1,2),imshow(fr_bw)
%subplot(3,1,3),imshow(uint8(fg))
end
close(v)

[Walter Roberson]

writeVideo(v,fg)

fg will be double precision. What range of values can it be? What range of values does writeVideo permit for double precision data?

[matin]

i'm not sure, worse luck. I just want a way to get this worked! i need my output in video format

Answer 1

[Walter Roberson]

v = VideoWriter('matin');

No file extension and no profile. What will happen in that case?

https://www.mathworks.com/help/matlab/ref/videowriter.html#d118e1576353

If you do not specify a valid file extension, VideoWriter appends the extension .avi, .mj2, or .mp4, depending on the value of the profile argument. If you do not specify a value for profile, then VideoWriter creates a Motion JPEG compressed AVI file with the extension .avi.

Okay so you are getting an .avi file. What are the limits for avi?

https://www.mathworks.com/help/matlab/ref/videowriter.writevideo.html

When creating AVI or MPEG-4 files:

• img is an array of single, double, or uint8 values representing one or more grayscale or RGB color images, which writeVideo writes as one or more RGB video frames.
• Data of type single or double must be in the range [0,1], except when writing indexed AVI files.

Your values are double() so they must be in the range 0 to 1. But are they?

if ((fr_diff(k,j) > thresh))
fg(k,j) = 255;
else
fg(k,j) = 0;
end

No, they are 0 and 255.

Perhaps you should initialize fg to be uint8.

[matin]

Thanks an ocean. I’ll try more and ask here my further questions.