4-D uint8 , what does it mean?

Hello,

I've uploaded a video to matlab with the following code and I got this on workspace:

I want to know more about the meaning of "4-D uint8", what does it mean? what are the 4 dimentions , what is uint8 ?

what is the dimentions of the variable "frames"? How can I extract one column from the 4-D table?

Thank you

video = VideoReader("measurment.mp4");
for(i = 1: video.NumberOfFrames)
    frames(:,:,:,i) = read(video, i);
end

[Walter Roberson]

size(frames)

Answer 1

[Stephan]

There is a 2D for height and width of the video, which shows the resolution, the 3rd D is for example is of size 3 for RGB or of size 1 for grayscale.

This 3 dimensions would describe one image. Since you have a video, there are all those single frames in the 4th dimension one after eachother.

What you want i guess is readFrame since you use a for loop. What you did is reading the whole video into one 4D array. This would not need a loop.

[John D'Errico]

And uint8 means this is an array of integers that lies between 0 and 255.

[semicolon]

unit8 means 8bits for each number in the fields of the 4-D line: [h,w,color,time] ?

[Stephan]

Yes, you cant have arrays with mixed types - except for cell arrays or tables.

[Stephan]

semicolon's answer moved here:

thank you.

so my last question is how can I extract one column (colors, or more specifically- the red color) from the values that I've mesured ?

[Stephan]

You can access the red color channel with using index = 1 on the third dimension:

AllRedFromFrame42 = frames(:,:,1,42)
TheFirst_10_x_10_RedFromFrame13(1:10,10:,1,13)