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
• • 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
  • H04N9/641—Multi-purpose receivers, e.g. for auxiliary information

Definitions

• the invention relates to a method for storing color television signals in a digital memory after the color television signal has been separated into the brightness information and the color information.
• the color signal component e.g. is decoded into components U and V in the case of television signals of the PAL or NTSC standard.
• the decoded signal components for brightness and color U and V are then digitized and stored in the memory. After reading out from the memory, the color signals must be encoded again. This means an additional circuit outlay due to the use of a decoder and a coder as well as for each color signal component of an analog-digital and digital-analog converter.
• the invention is based on the object of reducing this cost-intensive circuit outlay, which is also associated with additional adjustment work and possible misadjustments and with loss of quality due to the double implementation.
• the invention is based on exemplary embodiments with
• Fig. 1 shows the principle of the method
• FIG. 2 shows the invention using the example of processing a PAL or NTSC signal.
• FIG. 3 shows a detailed section of FIG. 2 and the invention using the example of processing a SECAM signal, a modification for processing a
• SECAM signal a simplified embodiment for a
• SECAM signal an exemplary embodiment for achieving the temporal compression of the color carrier
• the principle of the method is shown in FIG. 1 using the example of storing a PAL or NTSC-coded color television signal.
• the PAL-coded color television signal FBAS supplied by a signal source Q is divided into Lu a and Chro a shares. In the example shown, this is done with the help of a low pass TP and a band pass BP. Comb filters can also be used for this purpose.
• the Lu asignal Y reaches the analog-digital converter AD1, at the output of which the digitized signal Y 1 can be removed and is supplied to the memory SP.
• the chroma component CH together with the burst FB is fed to the analog-to-digital converter AD2, at whose output the digitized signal CH ! together with FB !
• the read signals Y ′′ and CH ′′, FB ′′ are converted back into analog signals Y, CH, FB with the digital-to-analog converters DA1 and DA2 and are passed to the adder as a composite signal via the adder circuit ADD Output. It can be seen that there is no decoding and coding of the color signal.
• Corresponding processing of a SECAM-coded color television signal takes place in such a way that it also manages without decoding and subsequent coding of the color signals.
• the color component is stored together with the identification signals in the memory SP.
• a television signal received via the antenna A is selected in the tuner T of a television receiver and converted into an FBAS1 signal in the intermediate frequency amplifier stage ZF.
• This FBAS1 signal arrives via an electronic switch U for further processing in a color television receiver for display on the screen as the main picture.
• an FBA52 signal which is supplied, for example, by a camera C, is divided into two branches Y and CH.
• the brightness signal Y is filtered out via a low-pass filter TP, the color signal CH reaches a mixer Ml, which mixes this signal down to approximately 570 KHz with the aid of an auxiliary frequency fhl generated by an oscillator OSC of, for example, 5 MHz, for example.
• the lower frequency position of the color signal brings the advantage of a simpler sampling in a subsequent analog-digital converter AD2 and the further digital signal processing as well as an unproblematic phase correction of this signal at the output of the memory.
• the mixed product CH 'from the mixing stage Ml is via a bandpass BP, which also consists of a Anti-aliasing filters can be filtered out.
• the color signal is not stored decoded into its components RY, BY here, but the vector of the color signal including the color synchronizing pulse is stored here. If decoding is omitted, subsequent coding of the color signal is also unnecessary.
• a phase correction circuit PH After conversion of the color signal read out in a digital-to-analog converter DA, this passes via a phase correction circuit PH to an addition circuit ADD, in which it is combined with the brightness signal Y taken from a digital-to-analog converter DA1 to (Y , CH, FB) 2 signal is formed, which is fed to the second input of the electronic switch U.
• the combined FBAS 1,2 signal can be taken from the output of the electronic switch U for further processing.
• the electronic changeover switch U is switched over by the control circuit CTR via the control line L1 in such a way that the additional image information is keyed into the first image information at the predetermined time.
• the burst of the sub-picture is required for the chroma phase synchronization of the sub-picture with the main picture, it is also stored.
• switches SI and S2 are closed with the aid of a control signal from the burst keying stage BA.
• the color synchronizing pulse FBI of the first image information and the switch S2 of the color synchronizing pulse FB2 of the second image information reach a phase comparator KPH, which is one of supplies the control voltage U1 dependent on the phase difference, which is applied to the control input of a voltage-controlled oscillator VCO via a low-pass filter TP.
• the oscillator VCO supplies a stable frequency fh.2 of 5 MHz, for example, with which the color signal CH ′′ read from the memory SP, including the burst of the second color information, is mixed up in a mixing stage M2.
• this signal is combined with the brightness signal Y of the second image information to form the (Y, CH, FB) 2 signal.
• a gain control VR is also inserted in the signal path of the color signal of the second image information, which changes the gain depending on a deviation of the two bursts of the main image and secondary image with the control voltage U2 generated by an amplitude comparator KA, so that no color saturation differences between Main and secondary picture occur.
• the phase and amplitude control for the secondary image can also take place a few lines before the secondary image is keyed in. This avoids any transient events in the keyed-in secondary image.
• the transmission of a SECAM signal is characterized in that the blue and the red color difference signal are transmitted alternately from line to line. Accordingly, the color difference signals are alternately written into the memory SP after the color signal CH separated from the FBAS2 signal is mixed down to a lower frequency position with an auxiliary frequency generated by an oscillator OSC in a mixing stage M1 and via a cloche filter. ter CF and was digitized by an analog-digital converter AD2. The signals read from the memory SP are converted back into analog signals by digital-analog converters DA and then mixed up with the aid of a mixing stage M2. The input and output side mixing processes can be dispensed with if a high clock frequency is selected for the digital converters and the memory.
• the circuit arrangement has two identification levels, one labeled IDW for writing and one labeled IDR for reading out the memory SP. This ensures a fixed assignment between the line address to be read (numbered) and the carrier-frequency color difference signal. For example, the R-Y signal is stored in an address with an even atomic number and the B-Y signal is stored in the memory SP in an address with an odd atomic number.
• the information of the instantaneous color difference signals R-Y or B-Y is available in parallel, which serves as a switching voltage for the correct keying into the main picture.
• the identification level IDR ensures that the secondary image read out with its color sequence fits into the color sequence of the main image.
• the sequence of the main picture is determined, which the control circuit CTR controls together with the identification signal of the address written in such a way that an address of the memory with an even number and an BY address of the main picture with an BY signal of the main picture and an address of the memory when the main picture is RY odd atomic number is read out.
• the correct reading is done by coupling with the signals for the vertical and horizontal deflection V2 and H2 of the secondary picture and the correct reading is done by coupling with the signals for the vertical and horizontal deflection VI and Hl of the main picture.
• the step-down transformation of the color carrier frequency can also take place in a different way than shown in FIG. 4, e.g. by division using a frequency divider e.g. through the divisor 4. This also reduces the bandwidth requirement for this signal.
• the color information After the color information has been read out of the memory, it can be transferred back into the original chroma frequency position by double squaring.
• this filter can be formed by a cloche filter. This has the advantage that the amplitude-reduced signal in the area of the quiescent carrier is reduced again in order to reduce Moiree interference on the transmitter side by means of an anti-cloche filter, as a result of which the digital-analog converter is better used are controlled and the signal-to-noise ratio is improved.
• the bandpass at the output of the color channel must then be designed as an anti-cloche filter CF 'in order to cancel the frequency response compensation of the cloche filter CF at the input of the analog-digital converter.
• This cloche filter can be designed in such a way that its output signal can be switched in its phase by 180 ° with the aid of a switching voltage obtained from the control circuit CTR and supplied via the line L2.
• This changeover has the task of changing the phase change of the standard-compliant SECAM carriers from line to line or from field lost in the size reduction of the secondary image to restore field.
• This switchover can take place horizontally or vertically, which further reduces a moiree interference that is still present.
• FIG. 5 shows a further possibility of processing a SECAM signal, in which the identification level IDR can be dispensed with when the SECAM signal is keyed in.
• the SECAM burst is also written into the memory SP and read from it again, which is compared with the burst of the main picture in the KPH stage. From this comparison, a control voltage for the memory control circuit CTR is formed, which e.g. interprets a "LOW" level in such a way that the read burst of the secondary picture corresponds to the burst of the main picture. With a "HIGH" level, the following line must be used for keying.
• a development according to FIG. 6 for SECAM is based on the following finding:
• the color carrier is read into a memory and, in order to achieve the temporal compression, with a clock rate increased by a factor of n, for example three times the clock rate. read out.
• Such an increase in frequency is unsuitable for the composite signal of the additional image, because the color carrier of this composite signal must also have the original color carrier frequency. Therefore, the frequency of the color carrier supplied to the memory is first reduced by the time compression factor.
• the frequency increase when reading out from the memory is compensated for by the frequency division in front of the memory, so that despite the increased readout frequency, a color carrier with the standardized frequency is created again.
• the SECAM television signal received with antenna A arrives via the tuner T and the IF amplifier ZF as a signal FBAS1 at an input of the switch U.
• the SECAM signal FBAS2 supplied by the camera C for the small additional picture is split into the luminance signal Y and the color carrier CH using the low-pass filter TP with a cut-off frequency of approximately 1.5 MHz and the bandpass filter CF serving as a so-called cloche filter.
• the read signal Y ′′ which is compressed in time by a factor of nl, for example 3, reaches the adder ADD via the converter DA1.
• the SECAM color carrier CH arrives at the frequency divider FT with the divider factor n2.
• the color carrier which is divided by n2 in frequency, reaches the memory SP as a signal CH 'via the converter AD2 and is read out as a time-compressed color carrier CH''in a time which is less by a factor of n1 and is transmitted via the converter DA2 and as a so-called anti-hole Filter bandpass filter CF fed to the adder ADD.
• the memory SP is controlled by the control circuit CTR.
• the output signal FB2 of the adder stage ADD represents the small additional picture.
• the switch U is switched by the circuit CTR via the line L1 such that the small picture corresponding to FB2 is inserted into the large picture corresponding to FBAS1.
• the frequency of the color carrier CH ' is increased by the factor nl when read out from the memory SP.
• the frequency division in the divider FT by n2 is thus compensated for by the frequency increase causing the time compression by the factor n1 in the memory SP. This results in the desired color without additional mixing, despite the time compression in the memory SP.
• the frequency divider FT thus does not require a carrier for mixing, but only divides the frequency of the color carrier CH by a whole value n2.
• Such passive or active frequency dividers for dividing the frequency of a SECAM color carrier are e.g. described in DE-AS 19 02 740.
• the divider factor n2 of the frequency divider FT can be switched over the line L2 if necessary.
• the frequency increase occurring per se with time compression of a signal is avoided.
• This has the advantage that, despite the temporal compression, the ink carrier has its original frequency of e.g. Maintains 4.43 MHz at PAL.
• This also simplifies the overall circuit, since previously used PLL circuits as well as mixing stages and oscillators for frequency conversion can be dispensed with.
• no decoders and encoders are required.
• the signal FBAS2 arrives in the memory SP1 for a display with picture in picture via the low-pass filter TP with a cut-off frequency of 1 MHz and the A / D converter AD1.
• the signal is read out from the memory SP1 in a time-compressed manner in a correspondingly shorter time and passes via the D / A converter DA1 to the adder stage ADD, the output of which is connected to the input b of the changeover switch U.
• the ink carrier CH is evaluated frequency-selectively with the bandpass filter BP and fed to a scanning device represented by the changeover switch SI.
• the changeover switch SI is actuated at three times the color carrier frequency 3 fsc and, according to FIG. 2, scans the color carrier three times during a color carrier period P.
• the sampled values are fed to a CCD memory SP3.
• the color carrier CH is not evaluated or the corresponding signal samples are not read into SP.3.
• three scans 4, 5, 6 take place, during P5 and P6 no evaluation of the color carrier and during P7 again scans No. 7, 8, 9.
• the signals of the periods P1, P4, P7 then again result in a continuous signal without frequency change according to FIG. 8a.
• the color carrier of a line is temporally compressed to a third of the line without changing the frequency.
• the ink carrier thus compressed in time thus reaches the adder ADD via the A / D converter AD2, the memory SP2 and the D / A converter DA2 to form the signal FB2.
• the changeover switch U is actuated by the changeover pulse UP from the line L1 and supplies the combined signal FBAS 1,2 for a display with a picture in a picture.
• the memory SP2 serves to establish the necessary time position from FB2 to FBAS1.
• the changeover switch SI, the stages AD1, SP1, DA1, AD2, SP2 and DA2 are controlled by the clock generator T in the manner shown.
• the clock generator T is controlled by the synchronous signals H, V of the signals FBAS1 and FBAS2.
• the changeover switch SI is bridged by the switch S2, which is closed by the pulse pulse BG during the duration of the color synchronization signal. It is thereby achieved that the suppression of periods, which is carried out in the modulated color carrier, does not take place for the color synchronizing signal. This is important so that the color synchronization signal with about 10 to 12 color carrier periods is not treated like the color carrier and the number of its periods is reduced for a perfect synchronization.
• the color carriers In the signals FBAS1 and FB2 at the inputs a, b of the changeover switch U, the color carriers must match in the basic phase, because the output c of the changeover switch U switches between inputs a and b in the picture during the picture during the picture is and the signal on the same color decoder ge ge.
• the signal FBAS 1,2 from the output c and the color carrier supplied to the adding stage ADD are applied to a phase and amplitude comparison stage VS, which is only effectively controlled by the pulse pulse BG during the duration of the color synchronization signal .
• the stage VS supplies a control voltage Ur, which regulates the frequency of the oscillator OS.
• the oscillator OS controls the memory SP2 and the D / A converter DA2.
• the frequency and phase of the color carrier on line L2 are readjusted so that the color synchronization signals in FB2 and FBAS1 match in frequency, phase and amplitude.
• the oscillator OS controlled in the manner described can additionally be used for controlling the changeover switch SI and the CCD circuit SP3, as is indicated by the dashed lines C3.
• This has the advantage that the circuit complexity is reduced by using a common control oscillator for SI, SP3, SP2 and DA2.
• the read-out frequency for the ink carrier corresponds to the read-in frequency of C3 with an accuracy of about 1 kHz.
• the clock C3 can therefore be used both for reading in and for reading out the color carrier in the manner described.
• the maximum phase deviation that is, the phase jump when the paused signal is combined speak the samples according to FIG. 8c assuming a constant frequency is only a few degrees.
• the switch S3 can also be inserted between the output of the changeover switch SI and the input of the memory SP3.
• the switch S3 is supplied by the switch voltage 3fsc via the frequency divider FF in the form of a flip-flop with the divider factor 2 as the switch voltage to the switch S3.
• the switching voltage thus has the frequency 3/2 "fsc and is shown in FIG. 8d.
• the switch S3 is only closed by the positive half-wave of the switching voltage according to FIG. 8d.
• FIG. 8c only the sample values number 2, 4, 6, 8, etc. and fed to the memory SP3, as shown in Fig.
• alternating color carrier periods are sampled with one sample value and / or two sample values 8c shows that when the evaluated periods are strung together in time, the sampled values No. 2, 4, 6, 8, etc., shown in broken lines, have the same time interval Aliasing products can occur due to the reduction to the sample values marked with dashed lines in FIG. 8c corresponding to the frequency 3/2 fsc there are useful channels and therefore do not interfere with the useful channel.
• the sampling frequency per se should be at least twice the maximum transmission frequency. In the case of the ink carrier limited in bandwidth, however, undersampling can also be carried out, for example with 3 / 2'fsc.
• FIG. 9 shows a circuit with which this phase jump can be avoided.
• the stage St supplies the color carrier CH, the luminance signal Y and the switching pulse UP for the switch U.
• the color carrier F of the signal FBAS1 and the color carrier CH fed to the phase comparison stage WS via the controllable phase rotator PHD.
• the stage WS is activated immediately before the switch U is switched by the pulse TI.
• a control voltage Urp is obtained as a function of the phase deviation.
• Urp controls the phase rotation of the stage PHD in such a way that a phase difference of the color carriers which is dependent on the modulation is compensated for.
• the ink carriers at the inputs of the stage WS and thus also the ink carriers at the inputs a and b of the changeover switch U then have the same phase at the changeover time of the changeover switch U. As a result, phase jumps in the ink carrier at the terminal c are corrected.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Processing Of Color Television Signals (AREA)
• Color Television Systems (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=25875381

Family Applications (1)

Country Status (9)

Families Citing this family (1)

Family Cites Families (7)

• 1989
  • 1989-10-24 DE DE3935330A patent/DE3935330A1/de not_active Withdrawn
  • 1989-12-16 AU AU48206/90A patent/AU4820690A/en not_active Abandoned
  • 1989-12-16 KR KR1019900701823A patent/KR910700591A/ko not_active Application Discontinuation
  • 1989-12-16 JP JP90501466A patent/JPH04502390A/ja active Pending
  • 1989-12-16 WO PCT/EP1989/001554 patent/WO1990007248A2/de not_active Application Discontinuation
  • 1989-12-16 HU HU90922A patent/HUT61862A/hu unknown
  • 1989-12-16 EP EP90900846A patent/EP0449916A1/de not_active Ceased
• 1991
  • 1991-05-07 DK DK91850A patent/DK85091D0/da not_active Application Discontinuation
  • 1991-06-17 FI FI912916A patent/FI912916A0/fi unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events