CLOCK RECOVERY AND RECONSTRUCTION OF PAL PICTURES FOR MPEG CODED STREAMS TRANSPORTED OVER ATM NETWORKS

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