The 'quality' property is valid only when a VideoWriter objects is used to create either a MPEG-4 or a MOTION JPEG AVI files.The property is a number between 0 and 100 which translates to video quality and file size. The VIDEOWRITER function internally translates this quality value to a bit-rate value. A quality value of 100 translates to the maximum bit-rate (least compression and hence largest file size) and a quality value of 0 translates to the lowest bit-rate (most compression and hence smallest file size).
Additional information about the VideoWriter class is available at the following link:
<http://www.mathworks.com/help/releases/R2012b/matlab/ref/videowriterclass.html>
