This paper proposes a new adaptive prediction algorithm which exclusively selects, on a pel-by-pel basis, either intraframe or motion-compensated interframe prediction. Prediction selection is made referencing previous samples, thus transmission of the selection information is not needed. Compared with motion-compensated interframe coding, it has been shown that coding performance is improved to a great extent, by about 40% for pictures with very fast motion, which is beyond motion compensation capability, and by 50% for scene change where motion compensation is, in principle, of no use.

An efficient coding method for multi-level digital image data with up to about 16 levels is described, which can attain data compression nearly equal to the theoretical bound given by a two-dimensional Markov model entropy, without any loss of picture information. The method, ordering predictive coding, is composed of an ordering prediction followed by a run-length coding of a serial prediction error bit stream. It is proved that the ordering prediction is the optimized prediction scheme and has a lower prediction error entropy than that of DPCM and bit plane, and also proved that the run-length coding reduces the entropy almost near to that of the two-dimensional Markov model entropy.

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.

An interframe coding system is described which is capable of transmitting a 4-MHz National Television System Commission (NTSC) color television signal. 6.3 Mbit/s transmission gives acceptable picture quality for video telephone or conference TV use. The NTSC color television signal is converted into a timedivision multiplex (TDM) signal which is composed of time-compressed chrominance and luminance signal in sequence. This signal is encoded using a frame-difference coder of the kind that has been used for black-and-white television signals. A field-repeating technique is introduced into the coder, to prevent a buffer memory from overflowing and to improve picture quality. Statistical investigations show that the presence of the timecompressed chrominance signal gives less than 10 percent increase in the amount of information generated by picture movements; this increase scarcely affects the picture quality.