manipulating frame by frame on AVI video

hi all!

first of all i will say i usually don't write scripts and MATLAB is not my cup of tea ;-)

having said that- i really need some help with basic code that i need to write.

i am reading an AVI code and i need to mark one fixed pixel so when the movie is running i will see this mark

i tried to write a code but surprisingly it does not working.

the code;

clc
clear all
x=VideoReader('focus_m1.avi');
%frame = x.read(1);
nFrames = x.NumberOfFrames;

for i=1:10
    %i=1:nFrames
    currFrame = x.read(i)
    %fig = figure(i)
    imshow(currFrame)
    hold on
    plot (333,397,'r-.x','MarkerSize',20)
    M=getframe; 
end

movie(M)

any help will be a saver

yael

Answer 1

[yael]

hi Chandra Kurniawan

the frame size is 480X720, and for 10 frames it indid working but my movie is ~30000 frames and it takes hours! is some other way to do that?

Answer 2

[Walter Roberson]

The data you are trying to write out is constant, and in a constant location. You can read a frame, set the specific locations in the frame array to the constant values, and then write the adjusted frame, without ever displaying the frame.

[yael]

can you pleas re-write it so i will understand your meaning?

[Walter Roberson]

x = VideoReader('focus_m1.avi');

xout = VideoWriter('focus_m1x.avi');

xout.FrameRate = x.FrameRate;

open(xout);

red3x3 = repmat(reshape([1 0 0], [1 1 3]), 2, 2, 1); %3x3 block of red

nFrames = x.NumberOfFrames;

for i = 1 : nFrames

currFrame = x.read(i);

currFrame(333:335, 396:398, :) = red3x3;

xout.write(currFrame);

end

xout.close;

clear x; %no close method for reader

[yael]

hi walter

thanks for the code

there is one thing i dont understand what whs tour meaning:

red3x3 = repmat(reshape([1 0 0], [1 1 3]), 2, 2, 1); %3x3 block of red

(and matlab return: "Error using repmat Too many input arguments")

thanks