"Dot indexing is not supported for variables of this type." error in reading VideoReader Object by its index?

I am working in video shot boundary detection, for that I need to read a specific video frame by its index, But in such cases when the video is read by its index in the main file, it runs perfectly but when it is ran in a seperate function, It gives an error "Dot indexing is not supported for variables of this type. in matlab", I am providing the code for which it is givning the error.

V=VideoReader("anni007.mpg");
if class1(1)>2
    A=final(class1,V);  % class1 is a frame transition numbers
else
    class1 = class1(2:length(class1));
    A=final(class1,V);
end

function A2 = final(C,V)
count = 1; th1 = 0.2; th2 =1;th3= 1;
for i = 1:length(C)
    St = StdDifference(V,C(i));
    if (St(2) > th1 && St(3)< th1 && St(1) < th1) 
        A2(count) = C(i);
        count = count + 1;
    end
end
end

function d = StdDifference(V,i)
count = 1;
for j=i-2:i+1
    I = read(V,j);% This line the code gives error of "Dot indexing is not supported for variables of this type" I cannot understand why?
    J = read(V,j+1);
    Ir_std = std2(I(:,:,1));
    Ig_std = std2(I(:,:,2));
    Ib_std = std2(I(:,:,3));

    Jr_std = std2(J(:,:,1));
    Jg_std = std2(J(:,:,2));
    Jb_std = std2(J(:,:,3));

    d(count) = sqrt((Ir_std-Jr_std)^2+(Ig_std-Jg_std)^2+(Ib_std-Jb_std)^2);
    count = count + 1;
end
end

[KSSV]

This line:

A=final(class1,V);// class1 is a frame transition numbers

Should be:

A=final(class1,V); % class1 is a frame transition numbers

You have not commented in the right way. Which line is throwing error. Can you show us the full error, if you are getting it still.

[INDRANATH ROY]

Sorry i didn't write in a correct way... Actually the error is in STD difference function line no 4,as mentioned above...

[KSSV]

That line should not throw any error. Check your error once.

Learn debugging the code.

Read here: dbstop

[Jan]

@INDRANATH ROY: I've tried to format the code properly.

"Dot indexing is not supported for variables of this type" I cannot understand why?" - I cannot understand this also, because this line does not contain any dot. So please post the complete error message, which should tell also, in which line the error occurs.

[Walter Roberson]

If the VideoReader call failed then that read() might be the first place affected.

Also I wonder if there is additional code beyond what was posted, with that additional code happening to have a "clear all"

Answer 1

[yanqi liu]

yes，sir，may be use VideoReader to make video to frame image file list，and then use the images to analysis，such as

function nFrames = GetVideoImgList(videoFilePath)
xyloObj = VideoReader(videoFilePath);

nFrames = xyloObj.NumberOfFrames;
vidHeight = xyloObj.Height;
vidWidth = xyloObj.Width;

[pathstr, name, ext] = fileparts(videoFilePath);

video_imagesPath = fullfile(pwd, sprintf('%s_images', name));
if ~exist(video_imagesPath, 'dir')
    mkdir(video_imagesPath);
end
files = dir(fullfile(video_imagesPath, '*.jpg'));
if length(files) == nFrames
    return;
end
h = waitbar(0, '', 'Name', 'process...');
steps = nFrames;
for step = 1 : nFrames
    temp = read(xyloObj, step);
    temp_str = sprintf('%s\\%04d.jpg', video_imagesPath, step);
    imwrite(temp, temp_str);
    pause(0.01);
    waitbar(step/steps, h, sprintf('%d%%', round(step/nFrames*100)));
end
close(h)