ecovery and econs tructio

The problem of clock recovery for an MPEG au- dio/video decoder, when the MPEG stream is transmitted over an ATM network and the decoded signal is to be converted to a PALNTSC format, is addressed. The presence of ATM cell delay variation represents a jitter source for the reconstruction of the main presentation reference signals associated with the coded streams. Since the PALNTSC synchronization signals are obtained from these signals, care must be taken to avoid Visi- ble artifacts in the displayed images, typically hue changes. It is shown that the clock recovery design, based on consumer quality video display requirements, is not more complex than ordinary PLL's used in transmission systems, while the buffer sue require- ments can be certainly contained within acceptable limits.