Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1988-09-19
1989-04-25
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358142, 358144, 358 12, H04N 704
Patent
active
048252867
ABSTRACT:
A band limited composite video television signal has summed with it, at a reduced amplitude, a frequency modulated audio carrier signal at a higher frequency. The sum signal is sampled and digitized at a sampling frequency which is at least twice the audio carrier frequency and is more than three times the frequency of a color subcarrier in the composite video signal, and is not related thereto. The sampling frequency is derived from a transmission network, whereby stuffing of the digitized signal for transmission is eliminated, and multiplexing of several digitized signals is facilitated. At a decoder, the digital signal is converted back into an analog signal and the audio carrier signal amplitude boosted using filtering. Picture quality of a reproduced television signal is enhanced in that quantizing noise in the video signal becomes uncorrelated from line to line and frame to frame, due to dithering effects by the audio carrier signal.
REFERENCES:
patent: 4544950 (1985-10-01), Tu
Article entitled "Digital Video Transmission in Optical Fiber Networks", by Krish A. Prabhu, FPN (Fiber Product News), Mar. 1988, pp. 28 to 37.
Groody James J.
Haley R. John
Northern Telecom Limited
Parker Michael D.
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