Video compression code working - Please explain the code

ImFolder=uigetdir;

pngFile = dir(strcat(ImFolder,'\*.png'));

S = [pngFile(:).datenum];

[~,S] = sort(S);

pngFiles = pngFile(S);

VideoFile=strcat(ImFolder,'\Video');

writeObj = VideoWriter(VideoFile);

fps= 15;

writeObj.FrameRate = fps;

open(writeObj);

for t= 1:length(pngFiles)

Frame=imread(strcat(ImFolder,'\',pngFiles(t).name));

writeVideo(writeObj,im2frame(Frame));

end

close(writerObj);

Above is the code i have used to compress the video,

Execution Steps:

1) Initially i recorded a video of 10seconds(Resolution - 160*120) size of video 8mb

2) I extracted all the frames from the video and saved in a folder

3) In this step i used above code

After executing above code i selected the directory where all the frames had been stored

4) After execution i got a video file of size 550Kb and of the same length as the original video

So original video is reduced to 550kb from 8mb, code is working good for my project, please help me the analyze the above code, how actually the compression is done by the code.

Thank You

[prem]

If I copied the same code and tried, I got the compressed video is of size 0 bytes.How did u get it correctly? please help me

[Image Analyst]

Did you get any error messages? Do you have a folder of PNG files like he did? Is your folder correct? What is length(pngFiles) for you? Maybe you should start your own question after reading this: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[siva p]

If I copied the same code and tried, I got the compressed video is of size 17 mb but original video size is 6 mb and also not playing compressed video

[Walter Roberson]

The original video was probably compressed with a different method. You should try passing in a "profile" as the second argument to videowriter. videowriter() is not designed for high compression.

"and also not playing compressed video"

Please explain that further? What is not playing compressed video?

[raahul anand]

I now want to decompress the compressed video. Can anyone send me the code or link?

[Walter Roberson]

"I now want to decompress the compressed video"

VideoReader and readFrame each frame and do whatever with it.

[P B ARUNRAJ]

Can you send me the code? I have frames of the video ,I can compress but dont know how to decompress.

[Walter Roberson]

Reading the frames with VideoReader or Vision.VideoFileReader automatically decompresses the frames. There is sample reading code in the documentation for those routines.

[dhrgham hani]

HI

HOW ARE YOU?

"I now want the compressed video"

Can you send me the code?

Thank you.

[ei]

hi please i want to video compression code

[Walter Roberson]

For video compression,

writeObj = VideoWriter(VideoFile, 'MPEG-4');

now writeVideo the frames.

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/matlab/ref/videowriter-class.html

writerObj = VideoWriter(filename) constructs a VideoWriter object to write video data to an AVI file with Motion JPEG compression.

So it is going to use Motion JPEG in an AVI container.

Answer 2

[kushagra parashar]

??? Undefined function or method 'VideoWriter' for input arguments of type 'char'.

Error in ==> Untitled at 7 writeObj=VideoWriter(VideoFile);

i am getting this error...what should i do

[Walter Roberson]

VideoWriter was introduced in R2010b. Which MATLAB release are you using?

Answer 3

[chandra sekhar uppu]

my video after expansion its size increases from 3 mb to 56 mb and its length increases from 1 min to 2 min the video has slow down.. i have used code

vid=VideoReader('w.mp4');
no=vid.NumberOfFrames;
for i=1:1:no
    frames=read(vid,i);
    base=sprintf('Image%d.png',i);
    ful=fullfile(pwd,base);
    imwrite(frames,ful);
    im(i)=image(frames);
end

after i got frames i saved in a folder and apply this codee.. but i got 2 min and size of 50 mb

[Walter Roberson]

Notice that the code posted in the Question has

fps= 15;

writeObj.FrameRate = fps;

You should adjust that 15 to the rate you need.

With regards to the size: if you are creating a .mp4 output file then you should consider

writeObj = VideoWriter(VideoFile, 'MPEG-4');

[Sliver Gaming]

How do i code it :/