JPH0828895B2 - Color television signal transmission method and receiver therefor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color television signal transmission method,
In particular, it relates to the improvement of image quality.

(Prior Art) A conventional color television signal transmission method for frequency-multiplexing and transmitting a luminance signal and a carrier color signal is known NTSC.
There is a standard method and a PAF method that is an improved version of the standard method.

FIG. 3 (a) shows a frequency spectrum diagram in the vertical spatial frequency domain of a color television signal according to the conventional NTSC standard system. As is well known, this is an interlace ratio 2: 1, field frequency f _v , frame frequency f. _v / 2 = f
The luminance signal component Y at _p and the line frequency f _{h is shown} by a solid line, and the carrier color signal component C is shown by a dotted line. That is, for both the luminance signal Y and the carrier chrominance signal component C, sidebands in the vertical spatial frequency domain are arranged on both sides of the harmonic of the line frequency f _h at intervals of the field frequency f _v. Half-frequency, that is, the color subcarrier of the frequency offset by 1 / 2f _{h is} phase-division-multiplexed and modulated by two color signals I and Q.
Further, the frequency-multiplexed carrier color signal component C is arranged at a frequency position separated from the luminance signal component Y by 1/2 of the frame frequency, that is, 1 / 2f _p . As is apparent from the spectrum diagram of FIG. 3 (a), there is a relatively wide frequency interval between the sets of spectrums of the luminance signal Y and the carrier color signal C separated by 1 / 2f _p . This does not mean that the given frequency band is fully utilized.

The present applicant has previously proposed a color television signal transmission system that eliminates the above-mentioned drawbacks, uses the frequency band efficiently, and does not cause crosstalk between two color signals due to the influence of the characteristics of the transmission path. This transmission method proposed in Japanese Patent Publication No. 58-7112 is a PAF (Phase Alternation Feature).
ld) system, the frequency spectrum of the color television signal in the vertical spatial frequency domain is as shown in the spectrum diagram of FIG. 3 (b), and the frequency gap portion in the spectrum of FIG. 3 (a) is used. Two color signals
C ₁ and C ₂ are frequency division multiplexed in separate spatial frequency regions.

(Problems to be Solved by the Invention) In the conventional NTSC standard system, since two color signals C ₁ and C ₂ are multiplexed and transmitted by the carrier color signal component shown by the dotted line in FIG. 3 (a), If the characteristics of the transmission line have asymmetry about the color subcarrier frequency f _sc , crosstalk is likely to occur between the color signals, and as is well known, one of the two color signals C ₁ and C ₂ is It has a drawback that it must be a wideband I signal for residual waveband transmission and another one is a narrowband Q signal for double-sideband transmission.

On the other hand, in the transmission system described in the above Japanese Patent Publication No. 58-7112, the carrier color signal component C _I by one of the two color signals C ₁ and C ₂ is indicated by a dotted line as shown in FIG. 3 (b). As shown in the figure, the carrier color signal component C _II due to the other one color signal is transmitted in a separate spectral arrangement as shown by the alternate long and short dash line. Therefore, crosstalk occurs between the color signals C ₁ and C _2. It is possible to make both bands of both color signals wide without generating, but because one color signal uses a color subcarrier frequency of a frequency different from the NTSC standard system, the receiver of the NTSC standard system uses the above-mentioned PAF. It has a drawback that it cannot demodulate the signal of the system and loses the compatibility of the receiver.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and to provide a color television signal transmission method that improves the image quality of the current system by broadening the bandwidth of the _two color signals C ₁ and C ₂ while maintaining compatibility with the NTSC standard system. A receiver for that purpose is provided.

(Means for Solving the Problems) In order to achieve this object, the color television signal transmitting method of the present invention is a color television transmitting a high frequency component of a Q signal which is not transmitted by the standard NTSC color television signal transmitting system. a signal transmission method, high-frequency components of the Q _H signal of the not transmitted Q signal, whereas when the low-frequency component of the Q signal transmitted by the transmission method was Q _L signal, the transmission side, the Q _H signal by adding the Q _HS signal polarity inversion every field to the Q _L signal or I signal, a color signal in the transmission method of the Q signal or the I signal color subcarrier, respectively, in the transmission method by the addition signal The _QHS signal is added after being modulated according to the modulation method, and on the reception side, from the transmitted modulated color carrier wave according to the color signal demodulation method in the transmission method. It said Q _L
The signal or the I signal is demodulated, the Q _HS signal is extracted from the demodulated signal, and the extracted signal is polarity-inverted field by field in synchronization with the polarity inversion on the transmitting side, and the Q _H signal is generated. Is restored, and the restored Q _H signal is added to the demodulated Q _L signal.

Further, when the high frequency component of the Q signal which is not transmitted by the NTSC standard color television system is the Q _H signal and the low frequency component of the Q signal transmitted by the transmission system is the Q _L signal, the transmitting side, the Q _H signal by adding the Q _HS signal polarity inversion every field to the Q _L signal or I signal, Q signal or the I signal for the color subcarrier, respectively, in the transmission method by the addition signal a receiver for restoring the Q _L signal and Q _H signal from the transmitted signal after having modulated according to the modulation method of the color signal in the transmission system, the apparatus comprising, Q of the transmission system
A signal demodulator or an I signal demodulator, and means for extracting the Q _HS signal from the signal demodulated by the demodulator,
Output means for outputting the Q _H signal by switching the Q _HS signal extracted by the extracting means and a signal obtained by reversing the polarity of the signal for each field in synchronization with the transmitting side, and output by the output means An adder for adding the generated Q _H signal to the Q _L signal demodulated by the Q signal demodulator, and arranged between the extracting means and the output means, or of the output means and the adder. It is characterized in that it is configured to include at least a space-time filter arranged therebetween.

Further, in a preferred embodiment of the receiving apparatus of the present invention, the means for extracting the Q _HS signal is a band pass filter to which the output Q _L + Q _HS + I _{H of the} Q signal demodulator is supplied. It is a thing.

In a preferred embodiment of the receiving apparatus of the present invention, the means for extracting the _QHS signal is a bandpass filter to which the output I + _QHS of the I signal demodulator is supplied.

(Embodiment) The method of the present invention and a receiver therefor will be described in detail with reference to the accompanying drawings.

FIG. 1 (a) shows a transmission signal and a spectrum diagram according to the method of the present invention. On the transmitting side, first of all, from the two color signals C ₁ and C ₂ of the color television signal, a wideband I signal and a Q signal (Q _L signal) band-limited to a narrow band are used, which is similar to the NTSC standard system. The carrier color signal component C _III is formed by the method,
Next, the carrier color signal component C _III and the carrier color signal component that are interleaved with a frequency separated by the frame frequency f _p from the high frequency component (Q _H signal) of the color signal C ₂ lost due to the band limitation. C _IV is formed, and these two carrier color signal components C _III and C _IV are multiplexed with the luminance signal Y and transmitted.

On the receiving side, the broadband C ₂ signal is restored by adding the Q _H signal demodulated from the carrier color signal component C _IV to the Q _L signal demodulated from the carrier color signal component C _III . Therefore, according to the transmission method of the present invention, the wide band I signal and the narrow band Q signal can be demodulated even by the receiver of the current NTSC standard system, and the compatibility of the receiver is maintained. As means for forming the carrier color signal component C _IV ,
For example, an NTSC color subcarrier whose phase is inverted for each field may be amplitude-modulated with a Q _H signal.

Next, FIGS. 1 (b) and 1 (c) show configuration block diagrams of the transmission side circuit and the reception side circuit of the first embodiment of the present invention, respectively.

On the transmitting side, the signal I is band-limited by 1.5 MHz LPF1, and then the color subcarrier frequency f _sc is modulated by the modulator 8 and this modulated signal is guided to the adder 11. On the other hand, the signal Q is 0.5M
Signal Q _L next is band-limited by HzLPF3, also for example 0.5M
The high frequency component is extracted by BPF2 having a pass band from Hz to 1.5 MHz and becomes a signal Q _H. The polarity of the signal Q _H is inverted for each field by the minus 1 coefficient unit 4 and the changeover switch 5. With this signal Q _HS , the color subcarrier frequency f
Modulating _sc has the same result as modulating the color carrier frequency f _sc, which is phase-inverted field-by-field with signal Q _H. The signal Q _HS is added to the signal Q _L in the adder 7 via the α coefficient unit 6, and further, in the modulator 9, the color subcarrier frequency f _sc whose phase is shifted by π / 2 is modulated. The output of the modulator 9 contains a signal Q _L which is a modulated color subcarrier frequency f _sc and a modulated signal Q _HS which is in an interleaved relationship with the signal Q _L separated by 30 Hz. The outputs of modulator 8 and modulator 9 are added by adder 11 to form a C signal.

Here, when the image has a motion component, the α coefficient unit 6 has a width in the line spectrum of the interleaved signal Y and signal C, so that the signal Y, signal I, and signal
Considering that separation between Q _L and signal Q _H becomes difficult, this is for stopping or limiting the multiplexing of signal Q _HS in advance when there are many image motion components. The value of the coefficient α of the α coefficient unit 6 changes according to a motion signal indicating the presence or absence of a motion component of an image detected by a known motion detection technique. When the image has no motion component, the value is 1, and the motion component is large. When it is zero, it changes gradually or continuously. By performing this processing, it is possible to eliminate the image quality deterioration due to incomplete separation between the signal Q _HS and the signal I or the signal Q _L in the moving screen, and at the same time reduce the cross luminance in the moving image for the current NTSC receiver. . Also in the case of still images, if the vertical resolution of signal I and signal Q is high, signal Q _HS
And because it can result in cross-talk between signals I or signal Q _L, it is necessary to remove the vertical high frequency component of the signal I, a signal Q by the vertical filter 12 and 13. These filters
Since the construction methods of 12 and 13 are known, they are omitted here.

Next, in the receiving side circuit shown in FIG. 1 (c), the signal C is demodulated by the demodulators 21 and 22 to generate an I-axis signal and a Q-axis signal, respectively. When the I-axis signal is band-limited by the 1.5 MHz LPF24, the signal I and the signal Q _HS remain in the output. The signal Q _HS has vertical and temporal high-frequency components due to polarity inversion for each field on the transmitting side, so this is removed by the space-time filter 29, and the signal I is output from this portion using the switch 28. Space-time filter 2 including space-time filter described later
The construction methods of 9,30 are well known and will not be described. When the signal passes through the spatiotemporal filter, blurring occurs in the moving image. Therefore, in the case of the moving image, considering that the multiplicity of the signal Q _HS is zero or limited as much as possible, the switch 31 depending on the motion signal.
To switch. That is, the switch 31 is set to the upper side for a still image and the lower side for a moving image. On the other hand, the Q-axis signal which is the output of the demodulator 22 and the BPF 25 which is the same as the BPF 2 extract the signal Q _HS , and the minus coefficient unit 27 and the switch 28 demodulate the signal Q _H. At this time, the switch 28 is synchronized with the switch 5 of the transmission side circuit. At this time, since the high frequency component signal I _{H of the} signal I is mixed in the output of the BPF 25, the component signal I _HS generated by the signal I _{H is} generated in addition to the signal Q _{H in} the output of the switch 28. Since this signal I _HS is a high-frequency component of vertical and time like the signal Q _HS , the signal I _Hs
Is removed. Further, when the image has a motion component, the separation of the signal Q _H and the signal I _HS becomes incomplete, so when the image motion component is large according to the motion signal, the addition amount of the signal Q _H is set to the α coefficient unit 32. Use to reduce or reduce to zero. The signal Q _H and the signal Q _L are wideband signals added by the adder 33. It should be noted that neither the α coefficient unit 6 on the transmitting side nor the α coefficient unit 32 on the receiving side is necessary either, and either one may be used.

Further, in FIGS. 1 (b) and (c), the signal Q _HS
Modulated and demodulated with the subcarrier frequency f _sc of the same phase as _L
Since Q _HS is a signal I and signal Q _L is the interleave spaced relation 30 Hz, may be the modem at the subcarrier frequency f _sc of the same phase as the signal I. In this case, the adder 7 shown in FIG. 1 (b) should be inserted between the LPF 1 and the modulator 8, and the input side of the BPF 25 shown in FIG. 1 (c) should be LPF.
It should be disconnected from the 26 input side and connected in parallel with this at the LPF 24 input side.

FIG. 2A shows a block diagram of the configuration of another embodiment of the receiving side circuit. The operation from the demodulator 41 to the LPF 46 shown is exactly the same as the operation from the demodulator 21 to the LPF 26 shown in FIG. 1 (c). The output signal of the BPF 45 includes the signal Q _HS and the signal I _H , of which the signal I _H is the space-time filter 47.
Attenuate by. The spatiotemporal filter 47 can be realized by a circuit as shown in FIG. 2B, for example, but since it is a known technique, its explanation is omitted. In the figure, the delay device 61 has a delay of 262H,
The delay device 62 has a delay of 1H. This allows the spatiotemporal filter
Only the signal Q _HS is taken as the output of 47. This signal is demodulated into a signal Q _H by the minus 1 coefficient unit 48 and the changeover switch 49, corrected by the α coefficient unit 50 according to the motion signal, and added.
It is added to the signal Q _L 51. The operation from the minus one coefficient unit 48 to the adder 51 is the same as the corresponding portion shown in FIG. 1 (c). On the other hand, the output of the coefficient unit 48 is the signal −Q _HS . Therefore, after passing through the same α coefficient unit 52 as the coefficient unit 50, this is added to the signal I + Q _HS which is the output of the LPF 44 in the adder 53 to obtain the signal I + Q _HS. Is obtained. This embodiment is shown in FIG. 1 (c).
There is an advantage that only one spatiotemporal filter having a circuit size slightly larger than that shown in the figure is required.

(Effects of the Invention) As described above, by using the color television signal transmission method of the present invention and the receiver therefor, two color signal I signals can be obtained while maintaining compatibility between the current NTSC system and the receiver. Both the Q signal and the Q signal can have a wide band, and the image quality of the current color television system can be improved.

[Brief description of drawings]

FIG. 1 shows a transmission frequency spectrum diagram (a) of a transmission method relating to the method of the present invention, and a block diagram showing a configuration of an embodiment of a transmission side circuit (b) and a reception side circuit (c), and FIG. A block diagram (a) of another embodiment of the side circuit and a detailed block diagram (b) of the spatiotemporal filter used in the same figure (a) are shown. FIG. 3 shows the conventional NTSC standard system (a). ) And a PAF system (b) transmission frequency spectrum diagram. 1,3,24,26,44,46 …… Low pass filter (LPF) 2,25,45 …… Band pass filter (BPF) 4,27,48 …… Minus 1 coefficient unit 5,28,49… … Changeover switch 6,32,50,52 …… α coefficient unit 7,11,33,51,53,63 …… Adder 8,91 …… Modulator, 10,23,43 …… π / 2 phase shifter Unit 12,13 ...... Vertical filter 21,22, 41, 42 …… Demodulator 29, 30, 47 …… Spatio-temporal filter 61, 62 …… Delay unit, 64 …… 1/2 coefficient unit 65 …… Subtractor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sumio Yano 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Institute of Broadcasting Technology, Japan Broadcasting Corporation (56) Reference JP-A-61-285894 (JP, A)

Claims (4)

[Claims] 1. A color television signal transmission method for transmitting a high-frequency component of a Q signal which is not transmitted by a standard NTSC color television signal transmission system, wherein the high-frequency component of the non-transmitted Q signal is a Q _H signal. When the low frequency component of the Q signal transmitted by the transmission method is taken as the Q _L signal, on the transmission side, the Q _HS signal in which the polarity of the Q _H signal is inverted for each field is added to the Q _L signal or the I signal. Then, the added signals are used to modulate the Q signal or I signal color subcarriers in the transmission method in accordance with the color signal modulation method in the transmission method, and then transmit, and the receiving side demodulates the color signal in the transmission method. Demodulating the Q _L signal or the I signal to which the Q _HS signal is added from the transmitted modulated color carrier according to the method, and extracting the Q _HS signal from the demodulated signal, The extracted signal is polarity-inverted for each field in synchronization with the polarity inversion on the transmission side to restore the Q _H signal, and the restored Q _H signal is added to the demodulated Q _L signal. A color television signal transmission method characterized by the above. 2. When the high frequency component of the Q signal which is not transmitted by the NTSC standard color television system is the Q _H signal and the low frequency component of the Q signal which is transmitted by the transmission system is the Q _L signal, the transmitting side the Q the _H signal is the Q _HS signal polarity inversion every field Q _L signal or added to the I signal, the transmission method of the color subcarrier for the Q signal or the I signal, respectively, in the transmission method by the addition signal A receiver for recovering the Q _L signal and the Q _H signal from a signal transmitted after being modulated according to the method for modulating a color signal in, wherein the device is a Q signal demodulator or an I signal of the transmission system. transmitting a demodulator, means for extracting the Q _HS signal from the signal demodulated by them demodulator, said Q _HS signal extracted by means of the extracted and the polarity inverted signal of the signal-side And output means for outputting a Q _H signal in the switched every field in synchronism, output by the output means
An adder for adding a Q _H signal to the Q _L signal demodulated by the Q signal demodulator, and arranged between the extracting means and the output means, or between the output means and the adder A receiving device, characterized in that it is configured to include at least a spatiotemporal filter to be arranged. 3. The receiving device according to claim 2, wherein the means for extracting the Q _HS signal is a band pass filter to which the output Q _L + Q _HS + I _{H of the} Q signal demodulator is supplied. A receiving device characterized by the above. 4. The receiving device according to claim 2, wherein the means for extracting the Q _HS signal is a band pass filter to which the output I + Q _HS of the I signal demodulator is supplied. Receiving device.