CA1098205A - Mixing of secam color-t.v. signals - Google Patents
Mixing of secam color-t.v. signalsInfo
- Publication number
- CA1098205A CA1098205A CA292,982A CA292982A CA1098205A CA 1098205 A CA1098205 A CA 1098205A CA 292982 A CA292982 A CA 292982A CA 1098205 A CA1098205 A CA 1098205A
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- Prior art keywords
- color
- frequency
- component
- amplitude
- modulated
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
- H04N9/74—Circuits for processing colour signals for obtaining special effects
- H04N9/76—Circuits for processing colour signals for obtaining special effects for mixing of colour signals
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Processing Of Color Television Signals (AREA)
- Color Television Systems (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A plurality of SECAM color-T.V. signals are -to be mixed. Each comprises an AM luminance component and an FM color component. For each individual signal, the color component is separated from the luminance component, frequency-demodulated, am-plitude-modulated, and then superimposed upon the respective luminance component to form a frequency multiplexed modified signal.
The plurality of thusly modified signals are then mixed using a single mixing channel. The mixed luminance component and the mixed color component are separated on the basis of frequency, and the mixed color component is amplitude-demodulated,then frequency-modulated, and then superimposed upon the mixed luminance component, to yield a SECAM color-T.V. signal which constitutes a mix of the original signals.
A plurality of SECAM color-T.V. signals are -to be mixed. Each comprises an AM luminance component and an FM color component. For each individual signal, the color component is separated from the luminance component, frequency-demodulated, am-plitude-modulated, and then superimposed upon the respective luminance component to form a frequency multiplexed modified signal.
The plurality of thusly modified signals are then mixed using a single mixing channel. The mixed luminance component and the mixed color component are separated on the basis of frequency, and the mixed color component is amplitude-demodulated,then frequency-modulated, and then superimposed upon the mixed luminance component, to yield a SECAM color-T.V. signal which constitutes a mix of the original signals.
Description
The present invention relates to the mixing of two or more SECAM color-T.V. signals to produce a resultant combined SECAM
color-T.V~ signal which is a linear combination of the original signals.
A process for the mixing oE SEC~I color-T.V. signals is disclosed in "Fernsehtechnik,)!' Schoenfelder, H., Part 2, Justus von Liebig Verlag, Darmstadt, pp. 16/lB, 16/1 and 16/2. This process recognizes th~ additive mixing of fre~uency-modulated signals does not yield a linear combination of the signals being mixed. In a SECAM color-T.V. signal, the luminance component is amplltude-modulated, but the two color difference signals, transmitted during alternate respective horizonta1-line~per1ods, are frequency-modulated.
Accordingly, this known mixing process first takes~each SECAM color~
T.V. signal to be mixed, and separates~the frequency-modulated color~
information component thereof from the~ampl~itude-modulated luminance component. The frequency-modulated color-informat~-on component is then frequency-demodulated~ Because the~base (unmodulated) frequency ;
of the carrier signal for the two color-differ~ence signals alternates, : . ,. ~, ~ having~one value for one color-ùifference signal, and a different ~ value for the other color-difference signal, this *requency-demodula~
tion is performed on a line-by-line basis, to yleld the video-fre-quen~y color-difference signals in their alternate ho;rizontal line -periods. This is done for each of the original SECAM color-TOV.
signals to be mixed. Thereafter, the luminance components of the ~ :' signals are mixed, and separately therefrom the video-frequency color- ~
.
information signals are mixed; i.e., the mixing of the luminance com-ponents of the signals to be mixed and the mixing of the color-in-formation components of the signals to be mixed is performed in paral-lel, using two()mixing channels. Thereafter, the color-information component mix is frequency-modulated and superimposed upon the mixed ~ ~
~.'~ : :
color-T.V~ signal which is a linear combination of the original signals.
A process for the mixing oE SEC~I color-T.V. signals is disclosed in "Fernsehtechnik,)!' Schoenfelder, H., Part 2, Justus von Liebig Verlag, Darmstadt, pp. 16/lB, 16/1 and 16/2. This process recognizes th~ additive mixing of fre~uency-modulated signals does not yield a linear combination of the signals being mixed. In a SECAM color-T.V. signal, the luminance component is amplltude-modulated, but the two color difference signals, transmitted during alternate respective horizonta1-line~per1ods, are frequency-modulated.
Accordingly, this known mixing process first takes~each SECAM color~
T.V. signal to be mixed, and separates~the frequency-modulated color~
information component thereof from the~ampl~itude-modulated luminance component. The frequency-modulated color-informat~-on component is then frequency-demodulated~ Because the~base (unmodulated) frequency ;
of the carrier signal for the two color-differ~ence signals alternates, : . ,. ~, ~ having~one value for one color-ùifference signal, and a different ~ value for the other color-difference signal, this *requency-demodula~
tion is performed on a line-by-line basis, to yleld the video-fre-quen~y color-difference signals in their alternate ho;rizontal line -periods. This is done for each of the original SECAM color-TOV.
signals to be mixed. Thereafter, the luminance components of the ~ :' signals are mixed, and separately therefrom the video-frequency color- ~
.
information signals are mixed; i.e., the mixing of the luminance com-ponents of the signals to be mixed and the mixing of the color-in-formation components of the signals to be mixed is performed in paral-lel, using two()mixing channels. Thereafter, the color-information component mix is frequency-modulated and superimposed upon the mixed ~ ~
~.'~ : :
-2-: .
~ .
, ~ Z ~ 3 amplitude-modulated luminance components, to yield a standard SECA~ color-T.V. signal which constitutes a linear combination of the original signals, both with respect ~o luminance and color in~
formation. This technique, compared to the mixing techniques used for PAL and NTSC color-T.V. signals, disadvantageously necessitates the use of two mixing channels, one for the luminance information, another for the col~r in-formation. The two~r~xing channels hitherto required for mixing SECAM color-T.V. siynals inherently increases the cost and bulk of SECA~ mixing circuitry, relative to the one-mixing-channel circuitry which can be used for PAL and NTSC color-T.V.
signals. ;~
It is a ~eneral object of the invention to mix S~CAM
color-T.V. signals using only a single mixing channel This can be achieved as follo~s: Each SECAM color- -~
T.V. signal to be mixed is split into an amplitude-modulated lumin-ance component and a video-frequency color component. The deriving of the video-frequency color component can be performed as in the prior art, utiliziny line-by-line frequency-demodulation of the al-ternately transmitted color-difference signals. The video-frequency color component is then amplitude-modulated and thereafter super-imposed upon the aiready amplitude-modulated luminance component.
Both the luminance and the color component of the color-T.V. signal are now in amplitude-modulated form. This is done for each SECAM
color-T.V. signal to be mixed. The thusly modified SECA~q color-T.V.
signals can now be additively mixed, in a single mixing channel, the resultant of which is a linear com~ination o~ the thusly modi-fied SECAM color-T.V. signals, the mixed amplitude-modulated lumin-ance components and the mixed amplitude-modulated color components beiny present as a frequency multiplex. The frequency multiplex is then separated on the basis of ~requency into the mixed AM luminance ~ e~
component and the mixed A~l color component. The mixecl AM color component is amplitude-demodulated, to yield a video frequency mix of the color components. This video-frequency color-information mix is then frequency-modulated in accordance with SECA~ standards, and superimposed upon ~he mixed AM luminance component, to yield a standard SECA~ color-T.V. signal constituting a mi~ of the original signals.
Preferably, the individual amplitude-modulated color components are suppressed-carrier signals, and the carrier signal utilized for this amplitude modulation is horizontal-frequency coupled with a half-line offset relative to the SECA~ color-T.V.
signal undergoing this conversion of its color component; i.e., the carrier used for the amplitude modulation is coupled to the horizon-tal frequency of the T V. signal involved, and the frequency of the carrier is an odd mul-tiple o:f one-half the line frequency. This technique per se is disclosed, for example, in Telefunken Zeitung, 36, 1963. No. 1/2 pp. 89-99. When the video~frequency color com~
ponent is amplitude-modulated ln this way, the su~sequent sepaxation~
of the mixed amplitude~modulated color component from the mixed am-plitude-modulated luminance c~mponent can be effected using comb filter techniques, for example of the type disclosed in Telefunken Zeitung 37, 19~ lo. 2, pp 115-135.
The novel features which are considered as character- ;
istic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional ob~ects and advantages thereof, will be best understood from the following de-scription of specific embodiments when read in connection with the accompanyiny drawinys.
FIG. 1 depicts the frequency spectrum of the luminance %~
and color components of a standard S~CA~ color-T.V. signal, and of such a signal modified preliminary to mixing in accordance with the present invention; and FIG. 2 depicts an exemplary block circuit diagram of a mixing system utilizing only one mixing channel for the mixing of SECAM color-T.V. signals.
In the compatihle PAL, NTSC and SECAM color-T.~.
systems, color information is transmitted within the frequency range occupied by the luminance information. The color informa-tion is modulated onto a color carrier, which is additively superimposed upon the luminance signal containing luminance information. ~A7hen proceeding in accordance with SECAM-Standard SECAM IIIop-t., the co]or carrier has one of the -two color-difference signals modulated onto it during alternate horizontal-line intervals, with the other color-difference signal being modulated onto the color carrier duriny the intervening horizontal-line intervals, the color-difference sig-nals being frequency-modulated onto the color carrier. The unmodu-lat~d frequency of the color carrier alternates between two dif-ferent values, one used when modulating thereonto one color-differ-ence signal, the other used when modulating thereonto the other color-difference signal. - ?
FIG. 1 depicts the spectrum of the luminance and color information of the luminance and color channels. The solid line indicates the frequency range of the luminance signal. This fre-quency range, extending from 0 to about 5 MHx, also encompasses the frequency range of the color-information signal (shbwn hatched).
The narrow band of the color-information signal is located in the upper part of the frequency range of the luminance si~nal. The frequencies 4.25 and 4.~ MHz are the two base (unmodulated) values which the frequency of the color carrier alternately assumes, one 32~
for modulation of one color-difference signal, the other for modulation of the other color-difference signal. As ~lready stated, the color information is present in frequency-modulated form.
To effect the mixing of a plurality of SECAM color-T.V. signals, the frequency-modulated color signal is separated from the luminance signal and converted into an amplitude-modulated color-information signal. This converted (amplitude-modulated) color signal is then frequency-multiplexed with the luminance signal, which is already an amplitude-modulated signal. According to the preferred concept of the invention, a part of the frequency range of the luminance~signal channel, the part normally including the ~ ~
frequency range of a normal SECAM color-information slgnal, is ~; -suppressed and, in amplltude-modulated~form,~ relocated at a frequen~
cy location above the~upper limit of the freguency range of the normal luminance~signal channel, at about 6 MHz (see ~he hroken . -line ln FIG. 1). This frequency-multiplexed slgnal can then be ~-subjected to a mixing process using one-channel mixing circuitry. ;~
FIG. 2 is a block circuit diagram depicting such a one-channel mixing system. Blocks perEorming identical functions ~ -are denoted by coxresponding numerals. Let is be assumed that two .~
different SECAM color~T.V. signals FBASl and FBAS2, to be additively mixed, are supplied to respective input terminals 1 and 1'. The SECAM color-T.V. signal FBASl applied to terminal 1 is transmitted to a SECAM decoder 3, which decodes the SECAM color-T~V. signal to yield the AM luminance signal component Y and the video-frequency color-information signal component of the video signal. The lumin-ance signal Y is transmitted through a low-pass filter having a cutoff frequency of about 4 MHz to the input of an adding stage 5.
The color-information signal (which as already explained comprises s the two color-difference signals duriny alternate respective horizontal-line intervals) is amplitude-modulated by an amplitude modulator 6 onto a carrier having a frequency of about 6 MHZ, then transmitted throug~ a low-pass filter having a cutof frequency of about 8 MIIz, and then applied to the other input oE adding stage 5.
The amplitude modulator 6 receives its 6 MHz carrier signal from a carrier-signal generator 8. Advantageously, the amplitude modula-tor 6 is designed as a balanced modulator producing at its output a suppressed-carrier amplitude-modulated signal. The freauency of -the carrier frequency generator 8 is horizontal-line-freauency coupled by means of a synchronizing signal S applied to terminal 9 of generator 8, in such a manner as to establish a hal~-line offset.
The frequency-multiplexed signal produced at the output of adding stage 5, consisting of an amplitude-modulated luminance signal and an amplitude-modulated color signal, is now applied to one input of a mixer 2. The other input of mixer 2 receives the SECAM color-T.V. signal FBAS2 applied to the terminal 1', after this second signal has been converted in the same manner as described with respect to first signal FBASl. The mixer 2 can for example be an A~-mixer o~ the type used for NTSC or PAL color-T.V. signals.
The signal produced at the out~ut of mixer 2, freauency-multiplexed due to the mixing process, is applied to a low-pass filter 10 having a cutof freguency of about 4 MHz and to a high-pass ~ilter 11 like-wise having a cutoff frequency of about 4 MHz, to separate the mixed luminance information from the mixed color information. The selected ~-frequency coupling technique utilizing a half-line offset would ad-ditionally make possible the use o a comh filter to efect this signal separation. The still amplitude-modulated color-in~ormation signal is demodulated in an amplitude demodulator 12. The resultant signallconstituted of the two video-frequency color-difference signals 2~
B-Y and R-Y in alternate horizontal-line periods, is frequency-modulated in a frequency modulator 13 and, in an adding stage 14, additively superimposed upon the luminance signal Y. At output terminal 15 of add.ing stage 14, there is available a linear com- : ~ -bination of the two SECP~I color-T.V. signals FBASl, FBAS2 applied ~
to the input terminal 1, 1'. -.
Because a suppressed-carrier amplitude-modulated signal cannot of itself be demodulated, the amplitude demodulator 12 utilized is a synchronous demodulator, to which is fed the carrier signal generated by carrier signal generator 8. Connected between the amplitude modulators 6, 6', .... , and the amplitude .
demodulator 12 will typically be phase-adjusti~ng circuitry (non-illustrated), making it possible to match the phase of the received :~
.
carrier signal.
Frequency modulator 13, at its terminal 16, receives . ~.
a SECAM-system color carrier slgnal, the frequency of which alter- ~
: nates between two different values for alternate horiæontal-line :1 periods; also, the phase of this si:gnal is periodically ~hanged back~
and forth `in accordance wlth SECAM-standards. ~his SECl~-system color carrier signal serves to synchronize the frequen~y modulator 13 during horizontal-blanking i.ntervals. ~ .
Because the synchronously demodulated color-information signal produced at the output of amplitude demodulator 12 may in~
: clude a residual component of the carrier signal utilized in the : demodulation, this residual carrier component can be eliminated by passing the demodulated signal through a low-pass filter operative for suppressing those frequency components whose frequencies lie ~:
outside the frequency range of the video-frequency color-difference signals. -It will be understood that each of the elements de-%~
1 scribed above, or two or more together, may also ind a useful applica-tion in other types of circuits and systems, differing from the types described above.
While the invention has been illustrated and described as embodied in the mixing of two S~CAM color-~.V. signals to yield a linear composite thereof, it is not intended to be limited to the details shown, since var1ous modifications and structural changes may be made without departing in any way from the spirit of the present invention.
,~
~.~
~ ~"
_g_ . . .
~ .
, ~ Z ~ 3 amplitude-modulated luminance components, to yield a standard SECA~ color-T.V. signal which constitutes a linear combination of the original signals, both with respect ~o luminance and color in~
formation. This technique, compared to the mixing techniques used for PAL and NTSC color-T.V. signals, disadvantageously necessitates the use of two mixing channels, one for the luminance information, another for the col~r in-formation. The two~r~xing channels hitherto required for mixing SECAM color-T.V. siynals inherently increases the cost and bulk of SECA~ mixing circuitry, relative to the one-mixing-channel circuitry which can be used for PAL and NTSC color-T.V.
signals. ;~
It is a ~eneral object of the invention to mix S~CAM
color-T.V. signals using only a single mixing channel This can be achieved as follo~s: Each SECAM color- -~
T.V. signal to be mixed is split into an amplitude-modulated lumin-ance component and a video-frequency color component. The deriving of the video-frequency color component can be performed as in the prior art, utiliziny line-by-line frequency-demodulation of the al-ternately transmitted color-difference signals. The video-frequency color component is then amplitude-modulated and thereafter super-imposed upon the aiready amplitude-modulated luminance component.
Both the luminance and the color component of the color-T.V. signal are now in amplitude-modulated form. This is done for each SECAM
color-T.V. signal to be mixed. The thusly modified SECA~q color-T.V.
signals can now be additively mixed, in a single mixing channel, the resultant of which is a linear com~ination o~ the thusly modi-fied SECAM color-T.V. signals, the mixed amplitude-modulated lumin-ance components and the mixed amplitude-modulated color components beiny present as a frequency multiplex. The frequency multiplex is then separated on the basis of ~requency into the mixed AM luminance ~ e~
component and the mixed A~l color component. The mixecl AM color component is amplitude-demodulated, to yield a video frequency mix of the color components. This video-frequency color-information mix is then frequency-modulated in accordance with SECA~ standards, and superimposed upon ~he mixed AM luminance component, to yield a standard SECA~ color-T.V. signal constituting a mi~ of the original signals.
Preferably, the individual amplitude-modulated color components are suppressed-carrier signals, and the carrier signal utilized for this amplitude modulation is horizontal-frequency coupled with a half-line offset relative to the SECA~ color-T.V.
signal undergoing this conversion of its color component; i.e., the carrier used for the amplitude modulation is coupled to the horizon-tal frequency of the T V. signal involved, and the frequency of the carrier is an odd mul-tiple o:f one-half the line frequency. This technique per se is disclosed, for example, in Telefunken Zeitung, 36, 1963. No. 1/2 pp. 89-99. When the video~frequency color com~
ponent is amplitude-modulated ln this way, the su~sequent sepaxation~
of the mixed amplitude~modulated color component from the mixed am-plitude-modulated luminance c~mponent can be effected using comb filter techniques, for example of the type disclosed in Telefunken Zeitung 37, 19~ lo. 2, pp 115-135.
The novel features which are considered as character- ;
istic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional ob~ects and advantages thereof, will be best understood from the following de-scription of specific embodiments when read in connection with the accompanyiny drawinys.
FIG. 1 depicts the frequency spectrum of the luminance %~
and color components of a standard S~CA~ color-T.V. signal, and of such a signal modified preliminary to mixing in accordance with the present invention; and FIG. 2 depicts an exemplary block circuit diagram of a mixing system utilizing only one mixing channel for the mixing of SECAM color-T.V. signals.
In the compatihle PAL, NTSC and SECAM color-T.~.
systems, color information is transmitted within the frequency range occupied by the luminance information. The color informa-tion is modulated onto a color carrier, which is additively superimposed upon the luminance signal containing luminance information. ~A7hen proceeding in accordance with SECAM-Standard SECAM IIIop-t., the co]or carrier has one of the -two color-difference signals modulated onto it during alternate horizontal-line intervals, with the other color-difference signal being modulated onto the color carrier duriny the intervening horizontal-line intervals, the color-difference sig-nals being frequency-modulated onto the color carrier. The unmodu-lat~d frequency of the color carrier alternates between two dif-ferent values, one used when modulating thereonto one color-differ-ence signal, the other used when modulating thereonto the other color-difference signal. - ?
FIG. 1 depicts the spectrum of the luminance and color information of the luminance and color channels. The solid line indicates the frequency range of the luminance signal. This fre-quency range, extending from 0 to about 5 MHx, also encompasses the frequency range of the color-information signal (shbwn hatched).
The narrow band of the color-information signal is located in the upper part of the frequency range of the luminance si~nal. The frequencies 4.25 and 4.~ MHz are the two base (unmodulated) values which the frequency of the color carrier alternately assumes, one 32~
for modulation of one color-difference signal, the other for modulation of the other color-difference signal. As ~lready stated, the color information is present in frequency-modulated form.
To effect the mixing of a plurality of SECAM color-T.V. signals, the frequency-modulated color signal is separated from the luminance signal and converted into an amplitude-modulated color-information signal. This converted (amplitude-modulated) color signal is then frequency-multiplexed with the luminance signal, which is already an amplitude-modulated signal. According to the preferred concept of the invention, a part of the frequency range of the luminance~signal channel, the part normally including the ~ ~
frequency range of a normal SECAM color-information slgnal, is ~; -suppressed and, in amplltude-modulated~form,~ relocated at a frequen~
cy location above the~upper limit of the freguency range of the normal luminance~signal channel, at about 6 MHz (see ~he hroken . -line ln FIG. 1). This frequency-multiplexed slgnal can then be ~-subjected to a mixing process using one-channel mixing circuitry. ;~
FIG. 2 is a block circuit diagram depicting such a one-channel mixing system. Blocks perEorming identical functions ~ -are denoted by coxresponding numerals. Let is be assumed that two .~
different SECAM color~T.V. signals FBASl and FBAS2, to be additively mixed, are supplied to respective input terminals 1 and 1'. The SECAM color-T.V. signal FBASl applied to terminal 1 is transmitted to a SECAM decoder 3, which decodes the SECAM color-T~V. signal to yield the AM luminance signal component Y and the video-frequency color-information signal component of the video signal. The lumin-ance signal Y is transmitted through a low-pass filter having a cutoff frequency of about 4 MHz to the input of an adding stage 5.
The color-information signal (which as already explained comprises s the two color-difference signals duriny alternate respective horizontal-line intervals) is amplitude-modulated by an amplitude modulator 6 onto a carrier having a frequency of about 6 MHZ, then transmitted throug~ a low-pass filter having a cutof frequency of about 8 MIIz, and then applied to the other input oE adding stage 5.
The amplitude modulator 6 receives its 6 MHz carrier signal from a carrier-signal generator 8. Advantageously, the amplitude modula-tor 6 is designed as a balanced modulator producing at its output a suppressed-carrier amplitude-modulated signal. The freauency of -the carrier frequency generator 8 is horizontal-line-freauency coupled by means of a synchronizing signal S applied to terminal 9 of generator 8, in such a manner as to establish a hal~-line offset.
The frequency-multiplexed signal produced at the output of adding stage 5, consisting of an amplitude-modulated luminance signal and an amplitude-modulated color signal, is now applied to one input of a mixer 2. The other input of mixer 2 receives the SECAM color-T.V. signal FBAS2 applied to the terminal 1', after this second signal has been converted in the same manner as described with respect to first signal FBASl. The mixer 2 can for example be an A~-mixer o~ the type used for NTSC or PAL color-T.V. signals.
The signal produced at the out~ut of mixer 2, freauency-multiplexed due to the mixing process, is applied to a low-pass filter 10 having a cutof freguency of about 4 MHz and to a high-pass ~ilter 11 like-wise having a cutoff frequency of about 4 MHz, to separate the mixed luminance information from the mixed color information. The selected ~-frequency coupling technique utilizing a half-line offset would ad-ditionally make possible the use o a comh filter to efect this signal separation. The still amplitude-modulated color-in~ormation signal is demodulated in an amplitude demodulator 12. The resultant signallconstituted of the two video-frequency color-difference signals 2~
B-Y and R-Y in alternate horizontal-line periods, is frequency-modulated in a frequency modulator 13 and, in an adding stage 14, additively superimposed upon the luminance signal Y. At output terminal 15 of add.ing stage 14, there is available a linear com- : ~ -bination of the two SECP~I color-T.V. signals FBASl, FBAS2 applied ~
to the input terminal 1, 1'. -.
Because a suppressed-carrier amplitude-modulated signal cannot of itself be demodulated, the amplitude demodulator 12 utilized is a synchronous demodulator, to which is fed the carrier signal generated by carrier signal generator 8. Connected between the amplitude modulators 6, 6', .... , and the amplitude .
demodulator 12 will typically be phase-adjusti~ng circuitry (non-illustrated), making it possible to match the phase of the received :~
.
carrier signal.
Frequency modulator 13, at its terminal 16, receives . ~.
a SECAM-system color carrier slgnal, the frequency of which alter- ~
: nates between two different values for alternate horiæontal-line :1 periods; also, the phase of this si:gnal is periodically ~hanged back~
and forth `in accordance wlth SECAM-standards. ~his SECl~-system color carrier signal serves to synchronize the frequen~y modulator 13 during horizontal-blanking i.ntervals. ~ .
Because the synchronously demodulated color-information signal produced at the output of amplitude demodulator 12 may in~
: clude a residual component of the carrier signal utilized in the : demodulation, this residual carrier component can be eliminated by passing the demodulated signal through a low-pass filter operative for suppressing those frequency components whose frequencies lie ~:
outside the frequency range of the video-frequency color-difference signals. -It will be understood that each of the elements de-%~
1 scribed above, or two or more together, may also ind a useful applica-tion in other types of circuits and systems, differing from the types described above.
While the invention has been illustrated and described as embodied in the mixing of two S~CAM color-~.V. signals to yield a linear composite thereof, it is not intended to be limited to the details shown, since var1ous modifications and structural changes may be made without departing in any way from the spirit of the present invention.
,~
~.~
~ ~"
_g_ . . .
Claims (13)
1. A method of mixing a plurality of SECAM color-T.V.
signals, comprising, in combination, These steps:
for each SECAM color-T.V. signal, separating the fre-quency-modulated color component thereof from the amplitude-modulated luminance component, frequency-demodulating the color component to yield a video-frequency color component, amplitude-modulating the video-frequency color component to yield an amplitude-modulated color component, and then superimposing the amplitude-modulated color component onto the amplitude-modulated luminance component to form a frequency-multiplex signal corresponding to the original SECAM color-T.V. signal;
mixing these frequency-multiplex signals using a single mixing channel to yield a frequency-multiplex mix signal which is comprised of a luminance mix component and a color mix component;
separating the color mix component from the luminance mix component on the basis of frequency;
amplitude-demodulating the color mix component to yield a video-frequency mix of the color components of the original SECAM
color-T.V. signals;
frequency-modulating the video-frequency color-component mix to yield a frequency-modulated mixed color component for a SECAM
color-T.V. signal; and superimposing the frequency-modulated mixed color com-ponent onto the amplitude-modulated luminance mix component to yield a SECAM color-T.V. signal which constitutes a mix of the original SECAM color-T.V. signals.
signals, comprising, in combination, These steps:
for each SECAM color-T.V. signal, separating the fre-quency-modulated color component thereof from the amplitude-modulated luminance component, frequency-demodulating the color component to yield a video-frequency color component, amplitude-modulating the video-frequency color component to yield an amplitude-modulated color component, and then superimposing the amplitude-modulated color component onto the amplitude-modulated luminance component to form a frequency-multiplex signal corresponding to the original SECAM color-T.V. signal;
mixing these frequency-multiplex signals using a single mixing channel to yield a frequency-multiplex mix signal which is comprised of a luminance mix component and a color mix component;
separating the color mix component from the luminance mix component on the basis of frequency;
amplitude-demodulating the color mix component to yield a video-frequency mix of the color components of the original SECAM
color-T.V. signals;
frequency-modulating the video-frequency color-component mix to yield a frequency-modulated mixed color component for a SECAM
color-T.V. signal; and superimposing the frequency-modulated mixed color com-ponent onto the amplitude-modulated luminance mix component to yield a SECAM color-T.V. signal which constitutes a mix of the original SECAM color-T.V. signals.
2. The method defined in claim 1, when amplitude-modulating the video-frequency color component of the individual original signals utilizing for the amplitude modulation a carrier whose frequency is closer to the upper limit of the frequency range of the amplitude-modulated luminance component than to the lower limit thereof.
3. The method defined in claim 2, utilizing a carrier whose frequency is higher than the upper limit.
4. The method defined in claim 2, utilizing a carrier whose frequency is coupled to the horizontal-line frequency of the respective original SECAM color-T.V. signals.
5. The method defined in claim 4, utilizing a carrier whose frequency is offset relative to the horizontal-line frequency.
6. The method defined in claim 5, the frequency of the carrier being an odd multiple of one half the horizontal-line frequency.
7. The method defined in claim 1, when amplitude-modulating the video-frequency color component of the individual original signals suppressing the carrier in the resultant amplitude-modulated signal.
8. The method defined in claim 7, when amplitude-demodulating the color mix component utilizing a synchronous de-modulator.
9. The method defined in claim 1, prior to superimpos-ing the amplitude-modulated color component of each individual signal onto the respective amplitude-modulated luminance component thereof passing the luminance component through a low pass filter to suppress spectral components stemming from the frequency-modulated color component of the original SECAM color-T.V. signal.
10. The method defined in claim 1, prior to super-imposing the amplitude-modulated color component of each individual signal onto the respective amplitude-modulated luminance component thereof passing the amplitude-modulated color component through a low-pass filter to suppress those spectral components whose frequen-cies are above the upper sideband of the amplitude-modulated color component.
11. The method defined in claim 1, the separating of the color mix component from the luminance mix component comprising passing the frequency-multiplex mix signal through a low-pass filter to obtain the luminance mix component and through a high-pass filter to obtain the color mix component.
12. The method defined in claim 8, passing the output signal of the synchronous demodulator through a low-pass filter to suppress those spectral components whose frequencies are outside the frequency range of the video-frequency color components.
13. The method defined in claim 1, the separating of the color mix component from the luminance mix component comprising passing the frequency-multiplex mix signal through a comb filter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19762656467 DE2656467C3 (en) | 1976-12-14 | 1976-12-14 | Method for mixing color video signals of the SECAM standard |
| DEP2656467.0 | 1976-12-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1098205A true CA1098205A (en) | 1981-03-24 |
Family
ID=5995426
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA292,982A Expired CA1098205A (en) | 1976-12-14 | 1977-12-13 | Mixing of secam color-t.v. signals |
Country Status (7)
| Country | Link |
|---|---|
| CA (1) | CA1098205A (en) |
| DD (1) | DD133186A5 (en) |
| DE (1) | DE2656467C3 (en) |
| FR (1) | FR2374806A1 (en) |
| GB (1) | GB1542357A (en) |
| HU (1) | HU179126B (en) |
| SU (1) | SU803875A3 (en) |
-
1976
- 1976-12-14 DE DE19762656467 patent/DE2656467C3/en not_active Expired
-
1977
- 1977-12-09 SU SU772552305A patent/SU803875A3/en active
- 1977-12-12 DD DD20255277A patent/DD133186A5/en unknown
- 1977-12-13 CA CA292,982A patent/CA1098205A/en not_active Expired
- 1977-12-13 GB GB5175677A patent/GB1542357A/en not_active Expired
- 1977-12-13 HU HUBO001694 patent/HU179126B/en not_active IP Right Cessation
- 1977-12-14 FR FR7737714A patent/FR2374806A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DD133186A5 (en) | 1978-12-13 |
| DE2656467A1 (en) | 1978-06-22 |
| HU179126B (en) | 1982-08-28 |
| SU803875A3 (en) | 1981-02-07 |
| DE2656467C3 (en) | 1980-02-28 |
| FR2374806B1 (en) | 1984-10-19 |
| DE2656467B2 (en) | 1979-06-21 |
| GB1542357A (en) | 1979-03-14 |
| FR2374806A1 (en) | 1978-07-13 |
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