Writing array to AVI using writeVideo

I have double array I convert using I8bit = uint8(I); Here is snippet of my code that works:

vidProfile = 'Grayscale AVI' ;

v = VideoWriter(fname,vidProfile);

open(v);

writeVideo(v,I8bit);

close(v);

This provides no compression. If I try other profiles such as 'Archival' I get this error: 'Error using VideoWriter/writeVideo (line 408) IMG must be an array of either grayscale or RGB images.'

How do I compress 8bit grayscale for AVI?