An ITU standard for transmitting audio and video in 64 Kbits/sec ISDN channels (P represents number of channels used). Although video conferencing can be done in only one or two channels, more channels are required for smooth motion. Px64 uses two screen formats. The CIF (Common Intermediate Format) generates a 352x288 resolution, while QCIF (Quarter CIF) is 176x144. CIF transmits at 36.45 Mbits/sec; QCIF is 9.115 Mbits/sec. See H.261.