Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1984-10-30
1987-04-14
Masinick, Michael A.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358166, 358141, 455 43, 455 70, H04N 5213
Patent
active
046582967
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and apparatus for reducing the visible noise observed on a picture due to the noise contribution of the transmission channel. It is intended primarily for channels used to transmit video information obtained by the sampling of a picture signal, which video information is transmitted accompanied by digital data which provides information regarding the transmitted signal.
The fundamental idea is to produce digital data indicative of a value of a parameter of the signal to be transmitted which can be used at the receiving apparatus to effect a noise reduction of the received signal.
The present invention provides apparatus for monitoring an information signal to be transmitted comprising means for receiving an input signal to be monitored, means for quantifying an optimum value of a parameter of the information signal to be transmitted and for generating a data signal indicative of the quantity of the parameter, and means for generating the data signal and the information signal.
The present invention further provides apparatus for receiving an information signal accompanied by a data signal containing information relating to the information signal, comprising means for receiving the data signal, means for receiving the information signal, means for processing the received information, and means responsive to the received data signal for controlling the processing means whereby to optimise reception of the information signal.
The noise reduction is effected in either or both of the following ways:
1. By reducing the thermal noise on the received video;
2. By reducing the number of threshold spikes on the received video when an F.M. channel is used.
Features and advantages of the present invention will become apparent from the following description of an embodiment thereof given by way of example when taken in conjunction with the accompanying drawings, in which:
FIG. 1 shows a representation of a frame of a television picture;
FIG. 2 shows a block diagram of a circuit according to the present invention and which is used at a transmitter;
FIG. 3 shows waveform to assist understanding of the operation of the circuit shown in FIG. 2;
FIG. 4 shows a modification for the circuit shown in FIG. 2; and
FIG. 5 shows a block diagram of a part of receiving apparatus for receiving a signal transmitted by the transmitter shown in FIG. 2.
The noise reduction method and apparatus of this invention would be especially suited for use in a T.V. system such as the M.A.C. system. In this system samples of an input picture signal are taken at times determined by certain clock frequencies. One clock frequency controls the sampling rate for luminance and another clock frequency controls the sampling rate for chrominance. The signals produced in this way are compressed such that one line of T.V. signal consists of a chrominance signal followed by a luminance signal, both accompanied by a digital data burst which provides sound channels and sync information.
It is proposed in the present invention to utilize the clock frequencies supplied by the M.A.C. system in such a way as to divide up a line of T.V. signal into signal elements or blocks, such that there will be a set of elements corresponding to the luminance signal and a set of elements corresponding to the chrominance signal. These signal elements do not have to be elements having a width of a single T.V. line, but could be elements having a width of, for example, a plurality of T.V. lines, e.g. 4. These signal elements can then be separately evaluated to produce the data associated with the noise reduction system. This data can then be transmitted with the other digital data inherent in the M.A.C. system.
(1) Thermal Noise Reduction
The full frame of a television picture is considered as being divided into a discrete number of boxes as shown in FIG. 1.
Noise reduction is effected by choosing optimum values for video pre and de-emphasis for each box. There are a plurality of choices e.g. 4 choices of pre and de-emphasis values. The data
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Independent Broadcasting Authority
Masinick Michael A.
Toth E. Anne
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