Kazumoto Iinuma

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.

Interframe Coding for 4-MHz Color Television Signals

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.

A Motion-Compensated Interframe CODEC

This paper describes an adaptive intra-interframe codec with motion-compensation followed by an entropy coding for prediction error signal as well as for motion vector information. This adaptive prediction is highly efficient even for very fast motion as well as scene change where motion compensation is ineffective. Prediction error and vector information are code-converted for transmission by means of an entropy coding where contiguous zero signal is run-length coded and non-zero signal is Huffman-coded. Based upon the algorithms described in this paper a practical codec has been developed for videoconference use at sub-primary rate. According to a brief subjective evaluation, the codec provides good picture quality even at a 384 kb/s transmission bit rate.

Low Bit Rate Motion Video Coder/Decoder For Teleconferencing

This paper describes motion video compression transmission for teleconferencing at a subprimary rate, i.e., at 384 kbits/s, including audio signal through the integrated services digital network (ISDN) HO channel. A subprimary rate video coder/decoder (codec), NETEC-XV, is available commercially that can operate at any bit rate (in multiples of 64 kbits/s) from 384 to 2048 kbits/s. In this paper, new algorithms are described that have been very useful in lowering the bit rate to 384 kbits/s. These algorithms are (1) separation of moving and still parts, followed by encoding of the two parts using different sets of parameters, and (2) scene change detection and its application to encoding parameter control. According to a brief subjective evaluation, the codec provides good picture quality even at a transmission bit rate of 384 kbits/s.