MATLAB: Create a video from a 4D array

4dbufferMATLAB and Simulink Student Suitevideovideowriter

Hello, I have a problem in this code.

function [] = writeBufferToFinalVideo(buffer)
video = VideoWriter('example','MPEG-4'); 
video.FrameRate = 25; 
open(video)
for i = 1:size(buffer,4)    
    img = buffer(i); 
    img(img>1) = 1;                           
    img(img<0) = 0; 
    writeVideo(video,img); 
end
close(video);
end

My buffer is a 4-dimensional array that has frames inside. It is composed of: (height, width, numChannels, framesPerSymbol). The latter is the number of frames that are in a symbol, that is, the size of my buffer.

In my opinion, I think the code is correct, but I always get an empty video without the frames in my buffer.

Best Answer

If buffer is a 4D-array, then you will need to index it like this

img = buffer(:,:,:,i);

Related Solutions

MATLAB: Insert elements into a 4D array

There are 2 mistakes in the above implementation:

Accessing a frame of frameBuffer as frameBuffer(i) instead of frameBuffer(:,:,:,i)
The function shiftBuffer changes the values of frameBuffer locally in the function and in the main code the frameBuffer isn't changed.

I suggest you to make the following changes.

Change the function shiftBuffer as follows:

function frameBuffer = shiftBuffer(frameBuffer,frame,framesInBuffer)
frameBuffer(:,:,:,,framesInBuffer) = frame;
end

and the following lines in your code

frame = readFrame(videoObject);    
shiftBuffer(frameBuffer,frame);       % <--------- THIS IS THE PART
% We update the framesInBuffer counter

framesInBuffer = framesInBuffer + 1;

frame = readFrame(videoObject);
% We update the framesInBuffer counter
framesInBuffer = framesInBuffer + 1;
frameBuffer = shiftBuffer(frameBuffer,frame,framesInBuffer);

MATLAB: Enter values into a FIFO array

I think you are trying to save last five frames in a buffer, but a for loop is not required for that purpose

frameBuffer=zeros (height, width, numChannels, framesPerSymbol);
framesInBuffer = 0;

While loop

while hasFrame(videoObject)
    frame = double(readFrame(videoObject));

I made a change here

    frameBuffer = shiftBuffer(frameBuffer,frame);  
    framesInBuffer = framesInBuffer + 1;

    if framesInBuffer > framesPerSymbol
        framesInBuffer = framesPerSymbol;
        bypassEncoding = false;
    else
        bypassEncoding = true;
    end
    if ~bypassEncoding
        if canWeEncode(frameBuffer,alpha,threshold)    
            encodedBuffer = steganographicEncoding(frameBuffer,width,height,codeRows,codeCols,alpha,sigma);
            writeBufferToFinalVideo(encodedBuffer,100);
        else                                        
            writeFrameToFinalVideo(squeeze(frameBuffer(:,:,:,1)));
        end
    end
end

and a change here

function frameBuffer = shiftBuffer (frameBuffer,frame)
frameBuffer = circshift(frameBuffer,1,4); 
frameBuffer(:,:,:,1) = frame;
end

Best Answer

Related Solutions

MATLAB: Insert elements into a 4D array

MATLAB: Enter values into a FIFO array

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