Statistical Performance Analysis of an Interframe Encoder for Broadcast Television Signals

This paper desribes an objective evaluation for coding performance of an interframe encoder (NETEC-22H). Also described is the coding performance improvement by an adaptive bit sharing multiplexer (ABS-MUX) in which transmission bit rate is dynamically allocated to several channels. Measurements made for actual broadcast TV programs over a time of 36 h show that an SNR of higher than 50 dB unweighted is obtained by this coding equipment for 99 percent of the time for broadcast TV programs at the transmission bit rate of 30 Mbits/s and for 93 percent of the time at 20 Mbits/s. The residual 1 percent at 30 Mbits/s or 7 percent at 20 Mbits/s is transmitted with a slightly lower SNR. The picture quality difference between the 20 and 30 Mbit/s transmission is about 6 dB in SNR on the average. It is also shown that a three-channel ABS-MUX (20 Mbits/s per channel on the average) reduces probability of coarse quantization by a factor of 5-10 compared with the fixed bit rate transmission at 20 Mbits/s.