How to read a video and then write it, resulting to exact same video file ( same file size , same pixel values )

I am using some code to read a video and then write the video again to a file. I will do some manipulation before i write it, but for now lets say we only want to write it back to disk.

But the video i am writing, whatever setting i use for videowriter, i can never get the same size of video ( size increases in disk or changes, and it also changes in pixel values. I can get the exact same pixel values, but only when writing uncompressed avi and this is multiplying the file size of the written file )

My original video is jpeg compressed but i dont know any more details about it, so i will use here the default traffic.avi matlab video which is also compressed.

If i use option Uncompressed avi i will get exact same pixel values, but times x the original filesize. If i use Motion JPEG AVI i will get a bit bigger filesize than original and also no matching pixel values...

Is there a way to write video using VideoWriter and some combination of properties to get the exact same pixel values and exact same file size as the original input?

I cant believe that this cannot happen in matlab.

This is and example code i am using with a default matlab file ( avi file can be also find at toolbox - images -imdata to check the size if you want )

i use this function ( its an official example matlab function ) to read video and the code below to do what i am trying to do

function video = readVideo(filename)

vr = VideoReader(filename);
H = vr.Height;
W = vr.Width;
C = 3;

% Preallocate video array
numFrames = floor(vr.Duration * vr.FrameRate);
video = zeros(H,W,C,numFrames);

% Read frames
i = 0;
while hasFrame(vr)
    i = i + 1;
    video(:,:,:,i) = readFrame(vr);
end

% Remove unallocated frames
if size(video,4) > i
    video(:,:,:,i+1:end) = [];
end

end

Vptr = VideoReader('traffic.avi');
writer = VideoWriter('delete_me.avi', 'Motion JPEG AVI');
writer.FrameRate = Vptr.FrameRate;
open(writer);
% Read and write each frame.
frameCounter = 1;
while hasFrame(Vptr)
  thisFrame = readFrame(Vptr);  % This is a uint8 variable.
  writeVideo(writer,thisFrame);
  frameCounter = frameCounter + 1;  
end
close(writer);


video = readVideo('traffic.avi');

video2 = readVideo('delete_me.avi');

isequal(video,video2)% 

[Murugan C]

Hi, sotiraw sotiroglou

Use this below code.

Vptr = VideoReader('traffic.avi');

writer = VideoWriter('delete_me.avi', 'Motion JPEG AVI');

writer.FrameRate = Vptr.FrameRate;

open(writer);

% Read and write each frame.

frameCounter = 1;

thisFrame = read(Vptr); % This is a uint8 variable.

numFrames = get(Vptr, 'NumberOfFrames');

for k = 1 : numFrames

read_frame = thisFrame(:,:,:,k); % reading frame by frame

writeVideo(writer,read_frame);

end

close(writer);

video = VideoReader('traffic.avi');

video2 = VideoReader('delete_me.avi');

if (get(video,'BitsPerPixel') && get(video2,'BitsPerPixel')) && ...

(get(video,'FrameRate') && get(video2,'FrameRate'))

disp('Both are equal data');

else

error('Both are not equal data : Please check your write data');

end

Answer 1

[Murugan C]

Hi, sotiraw sotiroglou

Use this below code.

Vptr = VideoReader('traffic.avi');

writer = VideoWriter('delete_me.avi', 'Motion JPEG AVI');

writer.FrameRate = Vptr.FrameRate;

open(writer);

% Read and write each frame.

frameCounter = 1;

thisFrame = read(Vptr); % This is a uint8 variable.

numFrames = get(Vptr, 'NumberOfFrames');

for k = 1 : numFrames

read_frame = thisFrame(:,:,:,k); % reading frame by frame

writeVideo(writer,read_frame);

end

close(writer);

video = VideoReader('traffic.avi');

video2 = VideoReader('delete_me.avi');

if (get(video,'BitsPerPixel') && get(video2,'BitsPerPixel')) && ...

(get(video,'FrameRate') && get(video2,'FrameRate'))

disp('Both are equal data');

else

error('Both are not equal data : Please check your write data');

end

Answer 2

[sotiraw sotiroglou]

I do this and the file size is still different between the two files ( 149 kb initial and 209 final for a sample video ) AND pixels also has different values in the two files. The code reports "both are equal data" but falsly ofcourse

[Murugan C]

Can you please upload your video. I wil look into.