A digital receiver contains a local video clock that controls the video
presentation speed and a local audio clock that controls the audio
presentation speed separately and independently of the video presentation
speed. To control the video presentation speed, a comparator compares a
program clock reference in a video packet with a local time. A video
clock controller then speeds up or slows down the video clock as needed
to be back on schedule. To control the audio presentation speed, a
comparator compares a program clock reference in an audio packet with the
local time. An audio clock controller then speeds up or slows down the
audio clock as needed to be back on schedule.