mp4 format video converted to avi format video wont load in matlab using mmreader()

i have converted an mp4 format video to avi format but loading it using mmreader() command gives the following error:

_ _ _ _ * ??? Initialization failed. (No combination of intermediate filters could be found to make the connection.)

Error in ==> mmreader.mmreader>mmreader.init at 364 obj.MMReaderImpl = audiovideo.mmreader(fullName);

Error in ==> mmreader.mmreader>mmreader.mmreader at 133 obj.init(fileName);

Error in ==> test1 at 5 video = mmreader('sample.avi');* _ _ _ _

can any one help me i don't understand the error my code is as following:

clear all

threshold= 15;

video = mmreader('sample.avi');

first_frame = video.read(1) ;

 first_frame_gray=rgb2gray(first_frame);

 total_frames= video.NumberOfFrames;

 [row,column,page]=size(first_frame);
 dummy_matrix = zeros(row,column);

for i=2:total_frames

    current_frame=video.read(i);

     current_frame_gray=rgb2gray(current_frame);

     frame_difference=abs(double(current_frame_gray)-double(first_frame_gray));

    for nr=1:row                 

        for nc=1:column

            if ((frame_difference(nr,nc) > threshold))          % if fr_diff > thresh then that pixel is in foreground

                dummy_matrix(nr,nc) = frame_difference(nr,nc);

            else

                dummy_matrix(nr,nc) = 0;   %if fr_diff < thresh then that pixel is black

            end

        end

    end
    first_frame_gray=  current_frame_gray;

    figure(1),subplot(2,1,1)

    imshow(current_frame)

    subplot(2,1,2)

    imshow(uint8(dummy_matrix))

    Movie(i-1)  = im2frame(uint8(dummy_matrix),gray);           % put frames into movie. i-1 cause it starts from 2

end

[Geoff Hayes]

Ayesha - have you read this link? It may provide some insight in to why you are unable to read the file.