Hideyuki Asada

Optimized sampling and bit rates of digital NTSC picture codes based on subjective evaluation of reproduced pictures

This paper describes optimized digital NTSC picture coding in which circuit and system configurations are simplified by lowering the sampling frequency and quantizing level. The sampling frequency and quantizing level are determined based on the subjective evaluation of the reproduced picture quality. In accordance with the result of the subjective evaluation, the digital NTSC picture containing one third of the information as compared with that of the normal digital NTSC picture was found to be satisfactory. Although the digital NTSC picture coding system normally uses a sampling frequency of 4/spl times/ fsc (fsc: the color subcarrier frequency of the NTSC system) with a quantizing level of 8 bits, the subjective evaluation leads to the result of a sampling frequency of 2.28/spl times/ fsc with a quantizing level of 5 bits.

Optical fiber transmission of data packets multiplexed with digital audio and video signals

Describes a system for transmitting data packets multiplexed with digital audio and NTSC TV signals using optical fibers. Up to 18 channels are allocated for data packets transmitted at a maximum speed of 1.764 Mbps. Digital audio signals are inserted into the horizontal sync period of the NTSC TV signal. In addition to data packet transmission, the digital NTSC TV signal transmission system is used to easily distribute many types of information classified into categories. The proposed system is characterized by: firstly, this system can give a satisfactory picture quality enough to operate it together with video equipment even though the quality of the reproduced pictures is lower than that of normal digital NTSC TV picture codes obtained at a sampling frequency of 4.00/spl times/fsc with a quantizing level of 8 bits. Secondly, NTSC TV picture codes, audio codes, and data packets can satisfactorily be transmitted using inexpensive devices at a transmission rate of as low as 50 Mbps. Thirdly, this system is used for transmitting data packets and audio signal codes which are inserted in the horizontal sync period of the digital NTSC TV signal. Both data packets and audio signal codes can be distributed to the specific receivers specified by device address. A combination of edge-emitting LEDs (ELEDs) and optical fibers enable the transmission system to easily transmit a digital NTSC TV picture signal together with data packets and digital audio codes. A new approach of combining ELEDs and optical fibers to distribute CATV pictures and electronic information via the ISDN is also proposed.

Optical fiber digital transmission of multiplexed video and audio signals suitable for multimedia applications

This paper describes a new digital NTSC TV and audio signal transmission system in which circuit configurations are simplified and made more inexpensive than MPEG 2 on the basis of the subjective evaluation of the picture quality. An NTSC TV signal and an audio signal can easily be transmitted to the receiver at the same time, since the transmission rate is kept unchanged due to the insertion of the digital audio signal into the horizontal sync pulse of the digital NTSC TV signal. The proposed system has three features. Firstly, the system could give satisfactory picture quality enough to operate consumer-use visual appliances even though the quality of the reproduced pictures is lower than that of the normal digital NTSC TV picture codes obtained at a sampling frequency of 4.00/spl times/fsc with a quantizing level of 8 bits. Secondly, the system can satisfactorily transmit NTSC TV picture codes at a low transmission rate of 50 Mbps even if such an advanced compression technique as MPEG 2 has not been used. Thirdly, the system is used for transmission of the digital audio signals which are inserted into the horizontal sync pulse of the digital NTSC TV signal. A combination of edge-emitting LEDs (ELEDs) and single-mode (SM) optical fibers enable the system to easily transmit a digital NTSC TV picture signal together with digital audio signals over the distance of 10 km through the SM optical fibers.

Still picture transmission through optical fiber utilizing multifrequency sinewave signals

This paper describes an optical fiber multifrequency data transmission system which is used to transmit NTSC still picture codes utilizing video RAMs which temporarily store still picture codes. In addition to the basic multifrequency data transmission system, the RAM installed in the sender (TX-RAM) and associated read/write circuits are used so that the data rate of the NTSC picture codes at 14.3 MHz is converted to 20 kHz which is suitable for multifrequency data transmission. On the other hand, the RAM installed in the receiver (RX-RAM) and associated read/write circuits are used so that the data rate of the picture codes transmitted in accordance with the multifrequency data transmission scheme is converted to the original high speed data rate at 14.3 MHz. When the write strobe specifying the start of storing data in the TX-RAM is generated, the picture frame recognized as a still picture can be sent from the sender to the receiver through optical fibers. Picture codes were satisfactorily transmitted without any trouble, and the quality of the transmitted still picture was good enough to monitor the status of the plant apparatus.