Line-sequential color television encoding and decoding system
AssigneeDecca Limited
InventorFrank Anthony Griffiths
Life of this patent
Estimating the term…
Abstract
A line-sequential color television system in which each line of a transmitted signal is compared in a decoder with an earlier line of corresponding chrominance and each line is averaged to form a luminance signal. The signals thereby derived are used to reconstitute the luminance component of the transmitted signal to preserve vertical detail therein notwithstanding any averaging of the transmitted signal for the extraction of chrominance components.
Claims47
A colour television signal decoder, comprising means for comparing each line of an input signal in the form of a luminance component combined with a line-sequential chrominance component of lesser band-width with a signal containing an earlier line of corresponding chrominance so as to derive a signal denoting vertical luminance changes;
- means for averaging the input signal over a plurality of lines so as to derive a luminance signal of lower frequency;
- and means for reconstituting the luminance component from the derived signals in the frequency range of the associated chrominance component.
A colour television signal decoder, comprising:
- means for comparing each line of an input signals in the form of a luminance component combined with a line sequential chrominance component of lesser band-width with a signal containing an earlier line of corresponding chrominance so as to derive a signal denoting vertical luminance changes;
- means for reducing the definition of the said signal that contains the said earlier line;
- means for averaging the said input signal over a plurality of lines so as to derive a luminance signal of lower frequency;
- and means for reconstituting the luminance component from the derived signals in the frequency range of the associated chrominance component.
In a colour television signal decoder, the combination comprising:
- means for presenting an input signal in the form of a line sequential colour television signal having a chrominance sequence which repeats every three lines;
- first, second and third delay-lines, each having a delay corresponding to one television line, coupled in tandem to receive said input signal;
- combining means coupled to the inputs of the said three delay-lines;
- and
- comparing means coupled to an output of the third delay-line and an output of said combining means.
A colour television signal decoder comprising:
- means for presenting a colour television signal in a form comprising a luminance component of relatively high frequency and a line sequential component of relatively lower frequency, the chrominance component cycling through a sequence of components in the form (R-M), (G-M) and (B-M) of which R, G and B present red, green and blue, and M represents (R+G+B)/3;
- means for combining each line of the television signal with earlier lines of corresponding chrominance so as to form a signal of reduced definition:
- means for combining together three successive lines of the reduced-definition signal so as to form a first, low frequency, luminance signal;
- and
- means for comparing each line of the signal of reduced definition with an earlier line thereof of corresponding associated chrominance so as to derive a second luminance signal containing higher frequency components than said first luminance signal;
- and
- means for combining said first and second luminance signals.
In a colour television signal decoder in which a colour input line-sequential television signal is fed through a plurality of one-line delays and the chrominance component signals which are thereby rendered simultaneously available are cyclically switched and are reconstituted with luminance components to form a composite colour television signal of normal band-width, the improvement which comprises:
- means for delaying each line of the input signal by a time corresponding to at least one cycle of the line sequence of chrominance of the input signal, whereby to render simultaneously available at least two lines of corresponding chrominance;
- means for comparing the two lines of corresponding chrominance to obtain an edge-defining signal which denotes "vertical" luminance changes;
- and means for reconstituting the said composite signal from said edge-defining signal in a frequency range which is common to the luminance and chrominance components of the input signal.
A colour television signal decoder, comprising:
- means for presenting an input signal in the form of a luminance component combined with a line-sequential chrominance component of lesser band-width
- means for combining, in proportions decreasing with age, each line of the input signal with earlier lines of corresponding chrominance so as to form a combined signal which contains a proportion of that input line and decreasing proportions of successively earlier lines of corresponding chrominance:
- means for comparing successive combined signals of corresponding chrominance as they are formed so as to derive a first derived luminance signal which denotes any vertical luminance change:
- means for averaging a plurality of successive combined signals of different chrominance so as to derive a second derived luminance signal denoting any resultant change in luminance from before to after said vertical luminance change;
- means for comparing the input signal with the said first and second derived signals so as to derive the said chrominance component;
- and,
- means for comparing the input signal with this derived chrominance component to recover the luminance component of the input signal.
A colour television signal decoder, comprising:
- a. means for providing an input signal in the form of a luminance component combined with a line-sequential chrominance component of lesser band-width than the said luminance component, said chrominance component cycling through a sequence of components in the form (R-M), (G-M) and (B-M) of which R, G and B represent red, green and blue colour signals and M represents (R+G+B)/3, the chrominance component being misregistered in advance of the luminance component by three scanning lines;
- b. means, including a delay of three lines, for receiving said input signal and combining each line of it with earlier lines occurring at integral multiples of three lines earlier so as to form, for each line of the input signal a combined signal constituted by proportions of lines of corresponding chrominance, said proportions decreasing with the age of said lines of corresponding chrominance,
- c. means for comparing combined signals which are separated by an interval of three lines so as to derive a first signal which denotes vertical luminance changes;
- d. means for combining three successive combined signals of different chrominance to derive a second, average signal, denoting longer term changes than does said first signal;
- e. means including two one-line delays in tandem for obtaining from the input signal the chrominance components of three successive lines in simultaneously available form;
- f. means for comparing the said first and second signals with said input signal to derive the chrominance component thereof for each line;
- g. means for restricting the band-width of said derived chrominance component to the said lesser band-width:
- h. means for comparing the input signal with said derived chrominance component to recover the luminance component of the input signal;
- and,
- i. means for reconstituting a composite colour television signal from the recovered luminance component and the simultaneously available chrominance components.
A colour television signal decoder, comprising:
- a. means for providing an input signal in the form of a luminance component combined with a line-sequential chrominance component of lesser band-width than the said luminance component, said chrominance component cycling through a sequence of components in the form (R-M), (G-M) and (B-M) of which R, G and B represent red, green and blue colour signals and M represent (R+G+B)/3, the chrominance component being misregistered in advance of the luminance component;
- b. means including a delay of three lines for comparing combined signals which are separated by an interval of three lines so as to derive a first signal which denotes vertical luminance changes,
- c. means for combining three successive combined signals of different chrominance to derive a second, average signal, denoting longer term changes than does said first signal;
- d. means including at least two one-line delays in tandem for obtaining from the input signal the chrominance components of at least three successive lines in simultaneously available form;
- e. means for comparing the said first and second signals with said input signal to derive the chrominance component thereof for each line;
- f. means for restricting the band-width of said derived chrominance component to the said lesser band-width:
- g. means for comparing the input signal with said derived chrominance component to recover the luminance component of the input signal;
- and,
- h. means for reconstituting a composite colour television signal from the recovered luminance component and the simultaneously available chrominance components.
In a colour television signal decoder in which a colour input line-sequential television signal having a line sequence recycling in a predetermined number of lines is fed through a plurality of one-line delays and the chrominance component signals which are thereby rendered simultaneously available are cyclically switched by switch means and are reconstituted with luminance components to form a composite colour television signal of normal band-width, the improvement which comprises:
- a chain of delay-lines numerically exceeding said predetermined number whereby said signals which are rendered simultaneously available include two signals,
- a cycle of chrominance apart;
- and
- means for combining said two signals.
A colour television signal encoder, comprising means for combining a luminance signal and a line-sequential chrominance signal, means for delaying the luminance signal relative to the chrominance signal by a time corresponding to a cycle of the sequence of components of the chrominance signal and means for adding to each line of the luminance signal a signal proportional to the difference between a later line associated with the same chrominance component and an adjacent line of the luminance signal.
A colour television signal encoder, comprising:
- a first channel for a luminance signal of wide band-width;
- a second channel for a line-sequential chrominance signal, said second channel comprising a plurality of one-line delays which provide a multiplicity of different delays
- each equal to a different multiple of a one-line period;
- means for combining the outputs of two different delays differing by one cycle of the line sequence of chrominance;
- so as to combine two signals of the same chrominance;
- an adder for combining the outputs of others of the delays so as to form from two signals of different chrominance a signal of the same chrominance as the said two signals of corresponding chrominance, said adder being connected to feed said means for combining;
- and
- means for adding the chrominance signal of the second channel to the luminance signal of the first channel.
A colour television signal encoder, comprising:
- means for combining a luminance signal and a line-sequential chrominance signal;
- and
- means for adding to each line of the luminance signal a signal representing the difference between a later line associated with the same chrominance component and a line adjacent to said later line.
In a colour television signal encoder wherein a luminance signal is combined with a cyclically line sequential chrominance signal which is of lesser band-width, the improvement which comprises:
- means for combining each line of that part of the luminance signal with said band-width with a fraction of at least the corresponding portion of a line which is one cycle of chrominance earlier;
- means for combining the said part a first fraction of the corresponding portion of the immediately preceding line;
- and
- means for forming the difference between the combination of said part and the first fraction and a second fraction of the said portion of the immediately preceding line.
In a colour television signal encoder wherein a luminance signal is combined with a chrominance signal which is of lesser band-width then said luminance signal and comprises a cyclic line sequence of different chrominance components, the improvement of a chroma softener which comprises:
- a plurality of delay lines coupled in tandem to receive at least one component of said chrominance signal, whereby a plurality of portions of successive lines of chrominance are rendered simultaneously available;
- and means for combining said portions in selected proportions to form each line of said chrominance component from a plurality of portions which represent the same chrominance component and come from different lines, whereby each line of the chrominance component is reduced in definition.
In an encoder which produces at an output a colour television signal constituted by a luminance signal of comparatively wide bandwidth and a chrominance signal comprising a line sequence of different components occupying part of the bandwidth of the luminance signal, the improvement which comprises:
- a delay, which receives at least that part of the luminance signal which shares a common frequency range with the chrominance signal, and provides a delay corresponding to at least one cycle of the line sequence of the chrominance components so as to make available for combination at least an instant line of the luminance signal and a line which precedes the said instant line by a cycle of chrominance;
- and
- means for combining a fraction of the said instant line with a lesser fraction of the earlier line.
An encoder for a line sequential colour television signal of which the chrominance components are in a cyclic line sequence, which encoder comprises:
- a. a luminance processing channel comprising:
- 1. a compensator which includes a succession of delay lines disposed for receiving a luminance signal and to make available, simultaneously with an instant line of the luminance signal, a plurality of following lines and means for adding together the instant line and selected proportions of the said following lines, said proportions defining at least one signal which represents the difference in a luminance detail between a line that follows the said instant line by the time of a cycle of the line sequence of chrominance and the line which is immediately before this later line;
- 2. a luminance softener which includes a recursive filter disposed to combine each instant line of the luminance signal with evanescent proportions of earlier lines which precede the respective instant line by integral multiples of said time;
- 3. a detail sharpener including means for combining each instant line of the luminance signal with a fraction of the immediately preceding line and means for forming the difference between the resultant combination and a fraction of the said immediately preceding line;
- and
- 4. means for limiting the effects of said compensator, luminance softener and detail sharpener to a low frequency part of the bandwidth of the luminance signal;
- b. a chroma processor which provides a chrominance signal in the form of a cyclic line sequence of different chrominance components occupying the said part of said bandwidth and which includes a chroma softener comprising means for combining each line of each chrominance component with like chrominance components derived from different lines of the chrominance signal;
- and
- c. means for combining the luminance signal and the line sequential chrominance signal for utilization thereof.
Dependencies are inferred from the claim text.