how to convert set of tiff files to AVI file

I have a set of tiff files and I am trying to put that set of images into AVI file for processing but my code does not work for me. I have a problem massege ("IMG must be of one of the following classes: double, single, uint8") but I couldnt find a solution.

this is my code I am using

v = VideoWriter('testing.avi','Uncompressed AVI');
open(v);
for k=1:10      % assumes 10 images to write to file
    str1 = '%d.tiff';
    str1pass = sprintf(str1,k);
    writeVideo(v,str1pass);
end
close(v);

thanks for the helpers

Answer 1

[Walter Roberson]

v = VideoWriter('testing.avi','Uncompressed AVI');
open(v);
for k=1:10      % assumes 10 images to write to file
    str1 = '%d.tiff';
    str1pass = imread(sprintf(str1,k));
    writeVideo(v,str1pass);
end
close(v);

[shuki firuz]

thank you!