GB2252005A

GB2252005A - Video signal processing for recording and playback systems

Info

Publication number: GB2252005A
Application number: GB9123495A
Authority: GB
Inventors: Christopher Hugh Strolle
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1990-11-05
Filing date: 1991-11-05
Publication date: 1992-07-22
Also published as: GB9123495D0; KR950005068B1; JP2608213B2; DE4135629C2; DE4135629A1; KR920017498A; JPH04267692A

Description

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-U-- VIDEO SIGNAL PROCESSING The present invention relates generally to apparatus and methods for processing video signals comprising chrominance and luminance signals and, more particularly although not exclusively, to video signals as generally processed in a video tape recorder wherein a separate channel is used for recording a chrominance signal on a magnetic tape.

As is known, the spectrum of a luminance (and sync) television signal consists of a dc component and components at harmonics of the horizontal scan frequency, each with a cluster about it of components separated at the vertical scan rate. Chrominance information is generally transmitted in the spectral gaps between these components. In the NTSC system, for example, two components of the chrominance signal, the in-phase (I) and quadrature (Q) signals, are amplitude modulated in quadrature to each other onto a subcarrier whose frequency (3.579545 MHz) has been selected to cause the resulting chrominance sidebands to fall in the spectral gaps between the luminance spectral components. The composite signal thus includes interleaved luminance and chrominance signals. The subcarrier frequency results in horizontal, vertical, and temporal interleaving so as to minimize mutual interference from cross-talk between the luminance and chrominance signals.

In typical video recording systems such as video cassette recorders (VCR's) used in the home for recording television signals, it is known, for the purpose of recording on a magnetic tape, to transpose the chrominance signal conventionally situated in the upper portion of the frequency spectral band of a composite television signal to a position in the spectral band below the luminance signal. Such a modulation or down conversion is commonly known in the recording art as a "colour-under" recording system. In such a colour-under system, the in-phase (1) and quadrature (Q) components of the chrominance signal are processed conventionally, albeit at a different carrier frequency, to develop a colour signal (C) for displaying a scene.

The well-known VHS system utilized in many VCR's produces degraded picture quality in comparison with, for example, properly received and processed broadcast television signals because it does not provide the full necessary horizontal resolution. It has long been a goal of television engineers to find ways of transmitting more information in a channel of given bandwidth. The frame and line rates are generally fixed in accordance with standards, and therefore, a bandwidth limitation typically results in a reduction in horizontal resolution. The typical restricted bandwidth of, for example, the VHS system of about 2.0 to 2.5 MHz thus produces an image of inadequate horizontal resolution.

Various techniques are known for recording a full bandwidth signal on a limited bandwidth medium such as magnetic tape. Such a system is.

disclosed in our co-pending European Patent Application EP 91 307 342.5 filed 9 August 1991 and claiming priority from U. S. Patent Application Serial No. 071569,029, filed August 17, 1990 of Strolle et al., entitled AN IMPROVED VIDEO SIGNAL RECORDING SYSTEM. Furthermore, a number of prior Patent Applications and other publications are discussed in our co-pending European Patent Application EP. 91 307 342.5, a copy of which is filed with the present application, and the contents of which are incorporated herein by reference. Other systems, such as for example, that disclosed in U.S. Patent No 4,831,463, issued May 16, 1989 to Faroudja, require modification of the format such that a tape recorded in accordance with that system would result in undesirable artifacts or defects in the picture when played back on a standard unmodified VHS machine.

It is herein recognized that the spectrum of the chrominance signal as utilized in the colour-under format exhibits spectral gaps. Thus, for example, our co-pending Patent Application GB 9108836.9 filed 24 April 1991, a copy of which is filed with the present application, and the contents of which are incorporated herein by reference, and which corresponds to U.S. Patent Application Serial No. 07/531,070 of Strolle et al., entitled CHROMA CHANNEL ENCODED WITH AUXILIARY SIGNALS, discloses apparatus is and a method wherein auxiliary signals, for example, digital audio signals or motion signals, are modulated onto a phase alternating carrier which is then added to the modulated chrominance carrier and processed in the chrominance channel for recording on magnetic tape.

According to a first aspect of the present invention, there is provided, in a video signal processing system having a luminance signal and having a chroma carrier modulated with chrominance information, a system comprising:

means responsive to said chroma carrier for generating a phase alternating carrier having a phase alternating from field to field; means for modulating a selected luminance signal on said phase alternating carrier; and means for adding said phase alternating carrier to said chroma carrier modulated with chroma information.

Such a system may include filter means for selecting a spectral portion 5 of said luminance signal for providing said selected luminance signal.

According to another aspect of the present invention, there is provided a video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, the system comprising:

first, second, and third filter means for selecting respective first, second, and third spectral portions of said television signal, such that said first spectral portion includes a region about said chroma carrier, said third spectral portion includes the lower frequency end spectral region of said television signal, and said second spectral portion is intermediate said first and third spectral portions; frequency translating means coupled to said first and second filter means for frequency transposing signals in said second spectral portion into said first spectral portion to provide an augmented signal; high pass filter means coupled to said third filter means for high pass filtering signals in said third spectral portion to produce a high pass filtered signal; and means for summing coupled to said frequency translating means and to said high pass filter means for summing said augmented signal and said high pass filtered signal to produce an output signal.

Such a system may include means for providing a carrier signal to said frequency translating means, said carrier signal alternating field to field but not line to line.

Preferably, said carrier signal is at a frequency such that said signals in said second spectral portion are transposed into said first spectral portion with their significant spectral component frequencies lying intermediate significant spectral component frequencies of signals in said first spectral portion.

is Such a system may include means for processing said output signal for recording.

According to a further aspect of the present invention, there is provided a video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, the system comprising:

first, second, and third filter means for selecting respective first, second, and third spectral portions of said television signal, such that said first spectral portion includes a region about said chroma carrier and includes a chrominance signal and a first luminance signal portion, said third spectral portion includes the lower frequency end spectral region of said television signal, and said second spectral portion is intermediate said first and third spectral portions and includes a second luminance signal portion; frequency translating means coupled to said first and second filter means for frequency transposing said second luminance signal portion signals in said second spectral portion into said first spectral portion to provide an augmented chrominance signal; high pass filter means coupled to said third filter means for high pass filtering signals in said third spectral portion to produce a high pass filtered signal; means for summing coupled to said frequency translating means and to said high pass filter means for summing said augmented chrominance signal and said high pass filtered signal to produce an output signal; means for providing a carrier signal to said frequency translating means, said carrier signal alternating field to field but not line to line; said carrier signal being at a frequency such that said second luminance signal portion in said second spectral portion is transposed into said first spectral portion with its significant spectral component frequencies lying intermediate significant spectral component frequencies of said signals in said first spectral portion; means for processing and recording said output signal; means for playback retrieval of said output signal; means for separating by filtering said augmented chrominance signal and said second luminance signal; means for frequency transposing said second luminance signal to produce a transposed second luminance signal; means for summing said first and transposed second luminance signals to produce a summed output signal; and means for processing said summed output signal.

According to another aspect of the present invention, there is provided a video signal processing system for recording a wideband video signal on a limited bandwidth medium, the system comprising:

an input terminal for receiving a video signal; signal processing means coupled to said input terminal, for separating said video signal into a first frequency band including a chrominance signal and a first luminance signal component, a second frequency band including a second luminance signal component, and a third frequency band including a third luminance signal component, said signal processing means folding said second luminance signal into said first frequency band for providing an augmented chrominance signal; and means for recording said third luminance signal component and said augmented chrominance signal.

Preferably, said signal processing means comprises:

first bandpass filter means coupled to said input terminal for passing signals in said first frequency band; second bandpass filter means coupled to said input terminal for passing signals in said second frequency band; a source of a first modulating frequency; first modulator means, having a first input coupled to an output of said second bandpass filter and a second input coupled to said source of a first modulating frequency; first addi ' ng means having a first input coupled to an output of said first bandpass filter and having a second input coupled to an output of said modulator; and combining means coupled to an output of said adder for combining said 20 third luminance component and said augmented chrominance signal.

Preferably, said combining means comprises; filter means coupled to said input terminal for providing said third 25 luminance signal component; 1 a source of a second modulating frequency; second modulator means having a first input coupled to an output of said first adding means and having a second input coupled to said source of a second modulating frequency; and second adding means having a first input coupled to said filter means and having a second input coupled to an output of said second modulator means.

Preferably, said combining means comprises; a motion spread signal generator having an input coupled to said input terminal; soft switch means having a first input coupled to said output of said first bandpass filter means, having a second input, having an output coupled to said first input of first adding means, and having a control terminal coupled to an output of said motion spread signal generator; and 1 H comb filter means coupled between said output of said first bandpass filter means and a second input of said soft switch means.

Preferably, when no motion is detected, said soft switch means transmits substantially a signal from said first bandpass filter means and when motion is detected, said soft switch means transmits a signal by way of said 1 H comb filter.

Preferably, said first modulating frequency is locked to a horizontal sweep rate and exhibits field to field alternation.

According to a further aspect of the present invention, there is provided a video signal processing system for playback of a video signal including a luminance signal component and an augmented chrominance component including a folded luminance signal component recorded on a limited bandwidth medium, the system comprising:

signal processing means coupled to a source of a playback signal for receiving said augmented chrominance signal and for separating out a folded luminance component from said augmented chrominance signal; and adding means having a first input coupled to said source of a playback signal and having a second input coupled to said signal processing means for adding said luminance signal component and said folded luminance signal component.

Preferably, said signal processing means includes a 1 H line comb filter for separating out said chrominance component and a field comb filter for separating out said folded luminance signal component.

Preferably, said line and field comb filters have respective inputs coupled to said source of a playback signal.

Preferably, said signal processing means comprises first and second filter means having inputs coupled respectively to outputs of said line and field comb filters.

Preferably, said signal processing means comprises:

a source of a carrier signal; modulator means having a first input coupled to said source of a carrier signal and having a second input coupled to an output of said second filter means; and first adding means having a first input coupled to an output of said modulator means and having a second input coupled to an output of said first filter means.

Preferably, said signal processing means comprises:

second adding means having a first input coupled to an output of said first adding means and having a second input coupled to said source of a 15 playback signal.

Preferably, said source of a carrier signal provides a signal having a frequency locked to a horizontal sweep rate and exhibiting field to field alternation.

Preferably, said signal processing means comprises:

a motion spread signal generator having an input coupled to said source of a playback signal; line comb filter means having an input coupled to said source of a playback signal; soft switch means having a first input coupled to said output of said field comb filter, having a second input coupled to an output of said line comb filter means, having an output coupled to said input of said second filter means, and having a control terminal coupled to an output of said motion spread signal generator such that when motion is detected, said soft switch transmits a signal from said line comb filter and in the absence of significant motion transmits a signal from said field comb filter; and transmission switch means coupled between said input of said first filter means and said line comb filter and having a control terminal coupled to said motion spread signal generator, such that when motion is detected, said transmission switch does not transmit a signal and vice versa.

According to another aspect of the present invention, there is provided, in a video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, a method for recording comprising the steps of.

selecting by filtering first, second, and third spectral portions of said television signal, such that said first spectral portion includes a region about said chroma carrier, said third spectral portion includes the low frequency end spectral region of said television signal, and said second spectral portion is intermediate said first and third spectral portions; and frequency transposing signals in said second spectral portion into said first spectral portion to provide an augmented signal.

Such a method may comprise the steps of.

high pass filtering signals in said third spectral portion to produce a high pass filtered signal; and summing said augmented signal and high pass filtered signals to 5 produce an output signal.

Such a method may comprise the step of..

frequency transposing signals in said second spectral portion into said first spectral portion to provide said augmented signal by modulation of a carrier signal alternating field to field but not line to line.

Such a method may comprise the step of:

selecting a frequency for said carrier signal such that said signals in said second spectral portion are transposed into said first spectral portion with their significant spectral component frequencies lying intermediate significant spectral component frequencies of signals in said first spectral portion.

2Q Such a method may comprise the step of recording said output signal.

According to a further aspect of the present invention, there is provided, in -a video signal processing system for a television signal comprising a first luminance signal and a chrominance signal augmented by a second luminance signal, which has been transposed into a spectral portion occupied by said chrominance signal with its significant spectral component frequencies lying intermediate significant spectral component frequencies of said chrominance signal, a method for playing back, comprising the steps of.

separating by filtering said chrominance signal and said second luminance signal from said augmented chrominance signal; frequency transposing said second luminance signal; and summing said first and second luminance signals.

The invention extends to a video recorder and/or player incorporating a system, or adapted to operate in accordance with a method, according to any 10 of the preceding aspects of the invention.

For a better understanding of the invention, and to show how the same may be carried into effect,- reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 shows in block diagram form an example of an embodiment in accordance with the invention, for recording; Figure 2 is a frequency response graph helpful to an understanding of 20 examples of the invention; Figure 3 shows in block diagram form an example of an embodiment in accordance with the invention, for playback; Figure 4 shows in block diagram form an example of a further embodiment in accordance with the invention, for recording; and z Figure 5 shows in block diagram form an example of a further embodiment in accordance with the invention, for playback.

The preferred embodiments are herein described in the context of the NTSC standards in use in the United States, by way of example only.

Nevertheless, the principles of the invention are applicable to other systems such as, for example, the PAL and SECAM systems used in parts of Europe and elsewhere. It should also be noted that the invention is applicable to colour television transmission systems and recording systems in which the chrominance and luminance systems are not spectrally interleaved in accordance with a standard NTSC television system.

Figure 1 shows a block diagram illustrating a preferred embodiment of the invention. A video signal source 10 is coupled to an analog to digital format converter 12 for supplying a composite video signal thereto. The output of analog to digital converter 12 is coupled to the input of a lowpass filter 14. A luminance processor 16 is coupled to low-pass filter 14 for receiving and further processing the filtered luminance signal. Luminance processor 16 is coupled to the input of a digital to analog format converter 18 whose output is coupled to an FM modulator 19 whose output signal is high pass filtered by a high pass filter 21 and applied to one input of a signal adder 20.

The output of analog to digital converter 12 is further coupled to the inputs of first and second bandpass filters, 22 and 24, respectively. The output of filter 24 is coupled to one input of a modulator 26. The other input of modulator 26 is coupled to the output of a modulator 30. The two inputs of modulator 30 are coupled respectively to a signal source 61 of a frequency - 16of one-half of the field frequency and a signal source 62 having a frequency of n times the horizontal line frequency, respectively. Various values are possible for n. However, a suitable value for the exemplary embodiment herein described is n=400. For a value of n=400, the modulator frequency is approximately 6.3 MHz. This has the effect of shifting the midband detail signal which is centered at 2.7 MHz (2.25/2 + 3.15/2) to the high band detail signal which is centered at 3.6 MHz (3.15/2 + 4.05/2). Furthermore, 400 fH is ten times the colour under carrier of 40 fH, which will allow the two frequencies to be locked to one another, thereby eliminating or greatly reducing the possibility of unwanted beat frequencies. The output of modulator 26 is coupled to one input of an adder 32. The other input of adder 32 is coupled to the output of bandpass filter 22.

The output of adder 32 is coupled to one input of a modulator 34. The other input of modulator 34 is coupled to the output of a bandpass filter 36 whose input is coupled to the output of a modulator 38. Bandpass filter 34 selects 4.21 MHz carrier signal from the output of modulator 38 and supplies it to the input of modulator 34.

The output of analog to digital converter 12 is further coupled to a sync separator 40 whose output is coupled to the burst sync input of a chrominance carrier oscillator 42. The output of chrominance carrier oscillator 42 is coupled to an input of modulator 38. The other input of modulator 38 is supplied with a 629 kHz carrier signal which is phase locked to the input video signal. This 629 kHz carrier signal is derived from a 629 kHz oscillator 44 controlled by the horizontal sync derived from the video input signal and whose output is coupled to the input of modulator 38 by way of a phase shifter 46. Phase shifter 46 is controlled by a one-half field rate (30

Hz) switching signal derived in the recorder to identify the two recorded tracks on the magnetic tape. Thus, the modulation products of modulator 34 contain the chrominance signal (derived from the output of bandpass filter 22) and luminance components modulated on (3.58 4.21) MHz carriers. The 629 kHz sidebands are selected from the output of modulator 34 by a lowpass filter 48 coupled to modulator 34 by way of a digital to analog converter 50. The output of lowpass filter 48, providing the composite colour-under signal, is coupled to the other input of adder 20, referred to earlier. The output of adder 20 is coupled to the recording circuitry 52.

In operation, lowpass filter 14 selects a signal representing a portion of the composite video signal frequency spectrum as shown in the portion of the graph below 2.25 MHz in Figure 2. In the exemplary embodiment, ideally, the -6 dB point in the passband of lowpass filter 14 is preferably selected to be at 2.25 MHz. However, in practice, it is desirable to make these bandwidths somewhat wider so as not to introduce any attenuation at the band edges, since the analog transmission systems tends to determine the attenuation at these band edges anyway. This spectral portion of the composite video signal is summed together with other signals as will be further explained and thereafter processed in the normal manner to a frequency modulated signal that varies from about 3.4 at the sync tip level to about 4.4 MHz for a peak white signal, for recording on tape. Second and third portions of the composite video signal frequency spectrum are selected by bandpass filters 24 and 22, as shown in the graph in Figure 2. The lower frequency -6 dB point of bandpass filter 24 is set to coincide with that of lowpass filter 14 at 2.25 MHz and its higher frequency -6 dB point is set a 3.15 MHz. The lower frequency -6 dB point of bandpass filter 22 is set to coincide with the higher frequency -6 dB point of bandpass filter 24 at 3.15 MHz. The higher frequency -6 dB point of bandpass filter 22 is set at 4.05 MHz. The overall passband thereby tends to exhibit a reasonably flat response characteristic, with the lowest frequency spectral portion of the composite video signal which comprises primarily a standard luminance signal, being passed by lowpass filter 14, an intermediate frequency spectral portion being passed by bandpass filter 24 and a top frequency spectral portion being passed by bandpass filter 22. The chrominance subcarrier being at 3.58 MHz, most of the chrominance signal is passed by bandpass filter 22, i.e. the highest frequency filter.

The upper spectral portion passed by filter 22 represents "high band" picture detail and chrominance (chroma). The intermediate portion of the spectrum shown in Figure 2 is conventionally recorded. The upper spectral portion requires no additional modulation since it is in any case present. However, it is not useful without the mid-band portion. In accordance with this embodiment of the present invention, the mid-band spectral portion, corresponding to the passband of filter 24, is transposed in frequency and spectrally interleaved with the chrominance signal.

Thus, the output signal of bandpass filter 24 is transposed into the same band as the chrominance signal by modulation in modulator 26 by a subcarrier that differs from the chrominance subcarrier in that it alternates phase from field to field but does not alternate from line to line. The chrominance signal and the transposed luminance signal are herein referred to as the augmented chrominance signal. The output signal of bandpass filter 22 is then summed to the output of modulator 26 in adder 32. Thus, even though the chrominance information signal with its associated luminance signal, ie the augmented chrominance signal, on the one hand, and the luminance signal from bandpass filter 24, on the other hand, occupy the same frequency band, they are separately recoverable because of the difference in their respective carriers.

The augmented chrominance signal is thereafter processed in a known manner for recording on tape by a 629 kHz subcarrier. This is accomplished by the synchronized chrominance subcarrier oscillator (3.58 MHz) output signal being modulated in modulator 38 with a synchronised 629 kHz signal, and bandpass filtering the resulting output to select a 4. 21 MHz sideband.

This signal is then used to modulate the output signal of adder 32 in modulator 34 to produce modulation products which, after filtering, result in the augmented chrominance signal modulated on a 629 kHz carrier. This signal is then summed with the lowpass filtered and processed luminance signal applied to adder 20 which produces an output for recording in recorder portion 52.

Table 1 below shows a time domain analytical representation for a number of fields and lines. In Table 1, C is chroma (chrominance), L1 the luma (luminance) from bandpass filter 22 and L2 the luma from bandpass filter 24.

It is apparent from Table 1 that the L1 and L2 signals are unchanged in phase from line to line in the same field. However, the L2 signal reverses phase from field to field. On the other hand, the chrominance signal alternates in phase from line to line within the same field and on a given line alternates in every second field.

TABLE 1

FIELD #1 FIELD #2 FIELD #3 FIELD #4

LINE #1 C+Lj+L2 -C+Lj+L2 LINE #2 -C+LI-L2 C+L1AL2 LINE #3 -C+Lj+L2 C+Lj+L2 LINE #4 C+LI-1-2 -C+LI-l-2 LINE #5 C+LI+L2 -C+LI+L2 Figure 3 shows a block diagram for a preferred embodiment of a playback arrangement for reproducing a recording made in accordance with the present invention. A playback luma signal YPB is converted to digital format by an analog to digital converter 300. The output signal of analog to digital converter 300 is applied to an adder 302. A 3.58 MHz augmented chrominance playbacksignal CPB is converted to digital format by an analog to digital converter 304. The output signal of analog to digital converter 304 is comb filtered by a line comb filter comprising 1 H delay 306 and an adder 308. The comb filtered output is converted to an analog chroma signal by digital to analog converter 310. The augmented chroma signal is further comb filtered by a field comb filter comprising a 1 H delay 306 plus a 262 H delay 312, and an adder 314. The output of adder 314 is filtered by bandpass filter 316 having a passband substantially the same as that of bandpass filter 22 in Figure 1. The output of bandpass filter 316 is applied to an input of an adder 318. The augmented chroma signal is further comb filtered by a field comb filter comprising 262 H delay 312, and a subtractor 320. The output of subtractor 320 is applied to the input of a bandpass filter 322 having a passband substantially the same as that of bandpass filter 24 in Figure 1. The output of bandpass filter 322 is modulated by modulator 324 with a carrier that does not alternate line to line but that does alternate field to field. The carrier is derived from a modulator 326 having a signal of half the field frequency applied to one input thereof and a signal of n.fH applied to the other input thereof and having an output coupled to an input of modulator 324 whereof the other input is coupled to the output of bandpass filter 322.

In operation, the line comb filter comprising 1 H delay 306 and adder 308 remove luma components from the chroma channel. Thus, the playback system of Figure 3 maintains compatibility with existing VHS players. The field comb filter comprising the 1 H delay 306 plus 262 H delay 312, and adder 314 and the field comb filter comprising 262 H delay 312 and adder

320 separate the respective spectral portions of the luma signal as originally separated by bandpass filters 24 and 22 in Figure 1. After filtering by bandpass filters 316 and 322, the two signals are added together in adder 318 and thereafter added together with signal YPB, to yield a combined signal of substantially greater bandwidth than that of signal YPB. Furthermore, compatibility is maintained with existing machines and tapes. In practice, bandpass filters 316 and 322 are preferably arranged to have a slightly narrower bandwidth than their respective corresponding filters 22 and 24 in order to facilitate removal of unwanted components introduced adjacent to the filter band edges in the analog portions of the signal paths.

Figure 4 shows an alternative embodiment for a recording portion in accordance with the present invention. Elements in the Figure 4 embodiment which correspond to the same or similar elements in the Figure 1 embodiment are marked with the same reference in both figures. In the Figure 4 embodiment, the composite signal is applied to a lowpass filter 14 for processing as in the Figure 1 embodiment and to bandpass filters 22 and 24. The composite signal is also supplied, as before, to sync separator 40.

The output signal of bandpass filter 22 is further processed in a motion adaptive circuit. The operation of this circuit will be briefly described here, being essentially similar in principle to that described in the aforesaid European Patent Application EP 91307 342.5 to which reference is made for a more detailed description of the motion adaptive circuits. The output signal of bandpass filter 22 is thus further applied to a line comb filter comprising a 1 H delay 23 and an adder 25 in which the line delayed signal which is applied to an input of adder 25 is subtracted from the undelayed signal which is applied directly to the other input of adder 25. The output of adder 25 and the direct connected output of bandpass filter 22 are applied to respective signal inputs of a soft switch 25. Soft switch 25 is responsive to the level of a control signal applied to its control input for selecting one or the other of the signals applied to its signal inputs and providing the selected signal at its output.

The output of A/D converter 12 is also applied to a motion signal derivation circuit comprising a temporal highpass filter 27 whose output is coupled to the input of a horizontal highpass filter 29. A subtractor 31 is coupled between the input and output of horizontal highpass filter 29 for deriving a difference signal between the signals at the input and output. The difference signal is applied to a magnitude detector 33 whose output is applied to a signal spreader 35. The output of signal spreader 35 is applied to the control input of soft switch 37.

Briefly, when motion is detected in the picture being processed, magnitude detector 33 provides a digital output indicating that motion is present. Signal spreader 35 modifies this signal by spreading. Further details of this aspect are given in the above-mentioned European Patent Application EP 91 307 342.5 and in our co-pending application GB 91 08683.5 entitled CONTROL SIGNAL SPREADER, a copy of which is filed with the present application, and the contents of which are incorporated herein by reference.

Soft switch 37 will thus vary the proportion of the two signals present at its signal inputs in response to the signal at its control input supplied from signal spreader 35. If the value of the control signal is zero or nearly zero, indicating no motion or a low level of motion, the soft switch 37 produces an output signal which is completely the output signal of bandpass filter 22, that is, chroma plus high band detail. If the value of the control signal corresponds to a high level of motion, then soft switch 37 produces an output signal which is completely the output of adder 25 which is a chroma signal with the high band detail filtered out. The presence of motion causes cross talk between the two luma detail signals being sent, and therefore, only the midband detail signal is sent during motion. The line comb filter will separate out the luma signal but reduces the vertical resolution. Thus, the line comb filter signal is preferably used only in the presence of motion. At intermediate values of the motion signal, the output signal of soft switch 37, contains some proportion of each of its input signals. Further details of the operation of a soft switch such as 37 are given in the aforementioned European Patent Application EP 91 307 342.5.

The output of soft switch 37 is then added to the output of bandpass filter 24 in adder 32. Processing thereafter continues as in the embodiment of Figure 1.

-24 Figure 5 shows another example of an embodiment of the invention for playback of signals as recorded using the embodiment of Figure 4, or otherwise recorded in a conventional manner. Elements in the Figure 5 embodiment which correspond to the same or similar elements in the Figure 3 embodiment are marked with the same reference in both figures. In the Figure 5 embodiment, a motion control signal is derived in the arrangement comprising a motion detector 402 coupled to receive the input luminance signal and supplying a motion signal to a signal spreader 404 which, in turn, provides a motion control signal. An adder 400 forms a 1 H filter in the same manner as adder 308 and provides an input signal to a soft switch 406.

The other input of soft switch 406 is the output of adder 320. Thus, the input to bandpass filter 322 may be entirely the output signal of one of adder 400 and adder 320 or it may comprise a portion of each output signal, depending on the level of a control signal at the control input of soft switch 406. A controlled switch 408 is disposed in the path coupling the output of adder 314 to bandpass filter 316. Depending on the level of a control signal at a control input of controlled switch 408, the output of adder 314 is applied or not applied to the input of bandpass filter 316. The motion control signal from signal spreader 404 is applied to the respective control inputs of soft switch 406 and controlled switch 408. Accordingly, during still areas of the picture, controlled switch 408 is gated on, so that the output of adder 314 is applied to bandpass filter 316 so that the output signal contains horizontal detail.

When motion is detected, the detail signal from adder 314 is not used.

Furthermore, in the presence of a high level of motion, the output of soft switch 406 corresponds to the output signal of the line comb filter at the output of adder 400; in the absence of motion, the output corresponds to the output of the 263 H field comb filter at the output of adder 320.

It will be understood that compatibility with existing playback and recording systems is maintained because the line comb filters in the chrominance channels remove both the luminance signal from bandpass filter 22 and the luminance signal from bandpass filter 24.

While exemplary embodiments of the invention have been described using a 3.58 MHz chroma carrier with modulation subsequently of the chroma and detail signals on a 629 kHz carrier other embodiments of the invention may be readily adapted to application where the baseband signals can be modulated directly on a 629 kHz carrier.

Furthermore, where the chroma subcarrier is encoded with phase relationships that are different from the VHS system forming the context of the described embodiments, such in the PAL and Beta formats, embodiments of the present invention may be adapted to these, with appropriate adjustment of the subcarrier phases utilized.

In the illustrated embodiments, carrier switching phase switching field to field is implemented before modulation; clearly, this order can be reversed.

These and other modifications will be apparent to those skilled in the art and are intended to be within the scope and spirit of the invention.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. In a video signal processing system having a luminance signal and having a chroma carrier modulated with chrominance information, a system comprising:

A system in accordance with claim 1 including filter means for selecting a spectral portion of said luminance signal for providing said selected luminance signal.

2.

3. A video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, the system comprising:

first, second, and third filter means for selecting respective first, second, and third spectral portions of said television signal, such that said first spectral portion includes a region about said chroma carrier, said third spectral portion includes the lower frequency end spectral region of said television signal, and said second spectral portion is intermediate said first and third spectral portions; frequency translating means coupled to said first and second filter means for frequency transposing signals in said second spectral portion into said first spectral portion to provide an augmented signal; high pass filter means coupled to said third filter means for high pass filtering signals in said third spectral portion to produce a high pass filtered 10 signal; and means for summing coupled to said frequency translating means and to said high pass filter means for summing said augmented signal and said high pass filtered signal to produce an output signal.

is

4. A video signal processing system in accordance with claim 3, including means for providing a carrier signal to said frequency translating means, said carrier signal alternating field to field but not line to line.

5. A video signal processing system in accordance with claim 4, wherein said carrier signal is at a frequency such that said signals in said second spectral portion are transposed into said first spectral portion with their significant spectral component frequencies lying intermediate significant spectral component frequencies of signals in said first spectral portion.

6. A video signal processing system in accordance with claim 3, 4 or 5, including means for processing said output signal for recording.

7. A video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, the system comprising:

8. A video signal processing system for recording a wideband video signal on a limited bandwidth medium, the system comprising:

9. A video signal processing system in accordance with claim 8, wherein said signal processing means comprises:

first bandpass filter means coupled to said input terminal for passing signals in said first frequency band; second bandpass filter means coupled to said input terminal for passing signals in said second frequency band; a source of a first modulating frequency; first modulator means, having a first input coupled to an output of said second bandpass filter and a second input coupled to said source of a first modulating frequency; first adding means having a first input coupled to an output of said first bandpass filter and having a second input coupled to an output of said modulator; and combining means coupled to an output of said adder for combining said third luminance component and said augmented chrominance signal.

10. A video signal processing system in accordance with claim 9, wherein 5 said combining means comprises; filter means coupled to said input terminal for providing said third luminance signal component; a source of a second modulating frequency; second modulator means having a first input coupled to an output of said first adding means and having a second input coupled to said source of a second modulating frequency; and is second adding means having a first input coupled to said filter means and having a second input coupled to an output of said second modulator means.

11. A video signal processing system in accordance with claim 10, wherein said combining means comprises; a motion spread signal generator having an input coupled to said input terminal; soft switch means having a first input coupled to said output of said first bandpass filter means, having a second input, having an output coupled to said first input of first adding means, and having a control terminal coupled to an output of said motion spread signal generator; and 1 H comb filter means coupled between said output of said first 5 bandpass filter means and a second input of said soft switch means.

12. A video signal processing system in accordance with claim 11, wherein, when no motion is detected, said soft switch means transmits substantially a signal from said first bandpass filter means and when motion is detected, said soft switch means transmits a signal by way of said 1 H comb filter.

13. A video signal processing system in accordance with any of claims 9 to 12, wherein said first modulating frequency is locked to a horizontal sweep rate and exhibits field to field alternation.

14. A video signal processing system for playback of a video signal including a luminance signal component and an augmented chrominance component including a folded luminance signal component recorded on a limited bandwidth medium, the system comprising:

15. A video signal processing system in accordance with claim 14, wherein said signal processing means includes a 1 H line comb filter for separating out said chrominance component and a field comb filter for separating out said folded luminance signal component.

16. A video signal processing system in accordance with claim 15, wherein said line and field comb filters have respective inputs coupled to said source of a playback signal.

17. A video signal processing system in accordance with claim 15 or 16, wherein said signal processing means comprises first and second filter means 15 having inputs coupled respectively to outputs of said line and field comb filters.

18. A video signal processing system in accordance with claim 17, wherein said signal processing means comprises:

19. A video signal processing system in accordance with claim 18, wherein said signal processing means comprises:

second adding means having a first input coupled to an output of said first adding means and having a second input coupled to said source of a playback signal.

20. A video signal processing system in accordance with claim 18 or 19, wherein said source of a carrier signal provides a signal having a frequency locked to a horizontal sweep rate and exhibiting field to field alternation.

21. A video signal processing system in accordance with claim 20, wherein said signal processing means comprises:

a motion spread signal generator having an input coupled to said source of a playback signal; line comb filter means having an input coupled to said source of a playback signal; soft switch means having a first input coupled to said output of said field comb filter, having a second input coupled to an output of said line comb filter means,'having an output coupled to said input of said second filter means, and having a control terminal coupled to an output of said motion spread signal generator such that when motion is detected, said soft switch transmits a signal from said line comb filter and in the absence of significant motion transmits a signal from said field comb filter; and transmission switch means coupled between said input of said first filter means and said line comb filter and having a control terminal coupled to said motion spread signal generator, such that when motion is detected, said transmission switch does not transmit a signal and vice versa.

22. In a video signal processing system for a television signal comprising a luminance signal and a chroma carrier modulated with chrominance information, a method for recording comprising the steps of.

23. A method in accordance with claim 22, comprising the steps of.

high pass filtering signals in said third spectral portion to produce a high pass filtered signal; and summing said augmented signal and high pass filtered signals to produce an output signal.

24. A method in accordance with claim 22 or 23, comprising the step of.

25. A method in accordance with claim 24, comprising the step of.

26. A method in accordance with claims 23, 24 or 25, comprising the step of recording said output signal.

27. In a video signal processing system for a television signal comprising a first luminance signal and a chrominance signal augmented by a second luminance signal, which has been transposed into a spectral portion occupied by said chrominance signal with its significant spectral component frequencies lying intermediate significant spectral component frequencies of said chrominance signal, a method for playing back, comprising the steps of..

separating by filtering said chrominance signal and said second luminance signal from said augmented chrominance signal; frequency transposing said second luminance signal; and 1 summing said first and second luminance signals.

28. A video signal processing system substantially as hereinbefore described with reference to Figure 1, 3, 4 or 5 of the accompanying diagrammatic drawings.

29. A method of processing video signals, substantially as hereinbefore described with reference to Figure 1, 3, 4 or 5 of the accompanying diagrammatic drawings.

30. A video recorder and/or player incorporating a system, or adapted to operate in accordance with a method, according to any of the preceding claims.