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.