It is clearly an error to master a disc side with a running time of less than 30 minutes (for a 30cm disc, or 15 for the 20cm size) in CLV Extended Play format rather than CAV Standard Play. Besides the trick play and other advantages of CAV, LaserDisc mastering must be done in real time, and occupying an hour on the lathe rather than half an hour is uneconomical. Nevertheless, such sides are encountered from time to time.