sentences:  Pitch errors in lower performance devices are uncompensated and kept to a level generally not perceived by the average viewer, by limiting the amount of change of reading speed.Typically the change limit is in the order of 0.2%.Unfortunately, this limits the rate of delay change and when large video delay changes occur the slow tracking rate of these uncompensated synchronizers can cause the audio-video sync to be off for several seconds or minutes until the audio delay catches up with the video delay.