How can I perfom an interpolation?

Hello, I have a code called codeAlpha, which has a value range of -1 to 1. My buffer is called frameBuffer and it has a size of (height, width, numChannels, framesPerSymbol), where framesPerSymbol is the size of the buffer. This buffer will store the frames of a video.

The ultimate goal of this code is to return a buffer called encodedBuffer which will have encoded images. These images will be obtained by adding frame (original image) + code (temporary interpolated) because the code goes from -1 to 1 and we want this transition to be controlled by N.

This is my code, I am currently having problems with the time dimension and it gives me an error.

codeAlpha = mapped*alpha;
bufferSize = size(frameBuffer,4);
numChannels = size(frameBuffer,3);
time = linspace(-1, 1, N);
frames = cat(4,zeros([size(codeAlpha),numChannels,bufferSize]));
for i = 1:length(time)
    frames(:,:,:,i) = codeAlpha.*time(:,:,:,i) + codeAlpha.*(1-time(:,:,:,i))*(-1);
end
for i =1:bufferSize
    encodedBuffer = frameBuffer + frames;
end

As an example I have been testing:

imgInicial = ones(2160,3840,3);
imgFinal = ones(2160,3840,3)*11;
frameBuffer = cat(4, imgInicial, imgFinal);
N = 5;

The code has the same dimensions as the images in the buffer.

I hope I have explained clearly, if you need me to explain something else, please let me know. Thank you very much in advance.

Answer 1

[dpb]

time = linspace(-1, 1, N);
frames = cat(4,zeros([size(codeAlpha),numChannels,bufferSize]));
for i = 1:length(time)
    frames(:,:,:,i) = codeAlpha.*time(:,:,:,i) + codeAlpha.*(1-time(:,:,:,i))*(-1);
    ...

What you trying to do here?

You've defined time as a vector of 100 points over range -1:1 but then try to reference it by a 4-D vector. That will return the whole thing by dimensions collapsing.

Look at the following minimal example that is small-enough and clean-enough to be able to visualize what's going on as outline...

B=ones(2,3,3,3);                % a trivially easy buffer array of three frames
t=linspace(-1,1,size(B,4));     % your weighting time vector sized on B to work in place
for i=1:numel(t),B(:,:,:,i)=B(:,:,:,i)*t(i);end % apply the weight -- other side is obvious
% show resulting B
>> B(:,:,:,1)
ans(:,:,1) =
    -1    -1    -1
    -1    -1    -1
ans(:,:,2) =
    -1    -1    -1
    -1    -1    -1
ans(:,:,3) =
    -1    -1    -1
    -1    -1    -1
>> B(:,:,:,2)
ans(:,:,1) =
     0     0     0
     0     0     0
ans(:,:,2) =
     0     0     0
     0     0     0
ans(:,:,3) =
     0     0     0
     0     0     0
>> B(:,:,:,3)
ans(:,:,1) =
     1     1     1
     1     1     1
ans(:,:,2) =
     1     1     1
     1     1     1
ans(:,:,3) =
     1     1     1
     1     1     1
>> 
% Show problem of wrong addressing for the time vector...
>> t(:,:,:,1)
ans =
    -1     0     1
>>