CODEWITHSUNDEEP
matlabmp4avi
user3204467
user3204467

Reputation: 11

batch converting mp4 to avi

I'm trying to convert a bunch of mp4 files to avis using the code below. I know that the conversion works as I've verified it on single files. However when I try to read in all mp4s from a directory the 'files' struct I've tried to create is empty. I'm relatively new to programming in MatLab so I'm sure I'm making many silly errors. How can I properly load in and iterate over multiple mp4 files in order to convert them all to avis? Thanks!

NB: I have tried different methods of conversion, but MatLab seems to be the best at ensuring no size or quality distortion.

files = dir(fullfile('E:\Heather\Summer2013\*.mp4'));
for i = 1:length(files)
filename = files(i).name;

    %create objects to read and write the video
    readerObj = VideoReader('files(i).name.mp4');
    writerObj = VideoWriter('files(i).name.avi','Uncompressed AVI');

    %open AVI file for writing
    open(writerObj);

    %read and write each frame
    for k = 1:readerObj.NumberOfFrames
       img = read(readerObj,k);
       writeVideo(writerObj,img);
    end
    close(writerObj);
end

Upvotes: 1

Views: 4805

Answers (2)

chappjc
chappjc

Reputation: 30589

A call to dir produces a struct array where file names are stored as strings in the name field. That is, files(i).name contains a string. To use it,

readerObj = VideoReader(files(i).name); % no quotes, no extension

To write with a different file extension, determine the file base with fileparts and add the .avi extension. For example:

>> str = 'mymovie.mp4';
>> [~,fileBase,fileExt] = fileparts(str)
fileBase =

mymovie

fileExt =

.mp4

>> writerObj = VideoWriter([fileBase '.avi'],'Uncompressed AVI');

Upvotes: 2

Daniel
Daniel

Reputation: 36720

You are trying to read the file with the name ('files(i).name.mp4') which obviously not exists. filename should be the corret parameter for the reader, for the writer you have to replace the extension.

Upvotes: 0

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