JPH0856368A - Digital television signal processor - Google Patents

Abstract

PURPOSE:To obtain excellent picture quality for both a standard and a nonstandard signal by detecting whether an input signal is the standard signal or nonstandard signal, and switching a luminance and chromaticity separating circuit, which performs motion adaptive type space processing when the signal is the nonstandard signal to processing in a space. CONSTITUTION:Respective circuits 127 to 133 such as a phase comparing circuit, an LPF, and a VCO generate pulses A from the synchronizing signal separated from a TV signal by a synchronous separating circuit 127. Further, phase comparing, LPF, and VCO frequency dividers 122 to 125 generate pulses B from the color burst signal extracted by a burst extracting circuit 121 from the TV signal. Respective circuits such as frequency dividers 126 and 135, a comparator 136, an integrator 137, a disturbance detecting circuit 142, and an OR circuit 143 detect whether the TV signal is the standard signal or nonstandard signal by using the pulses A and B. Consequently, motion adaptive Y and C separating circuits 109 and 110 switch the time space processing to the processing in the space when the signal is the nonstandard signal. Consequently, excellent picture quality is obtained for both the standard and nonstandard signal.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital television receiver, and more particularly to an NTSC system produced by a VTR or the like.
The present invention relates to a signal processing device necessary for optimally processing a nonstandard signal that does not satisfy the specifications of the system. 2. Description of the Related Art In a conventional television receiver, cross color and dot crawl caused by frequency multiplexing of a chrominance signal with a luminance signal, line flicker caused by interlaced scanning, and scanning lines are performed. It is known that image quality degradation such as interference occurs. In order to eliminate such image quality deterioration factors and achieve high image quality, a semiconductor memory and a digital signal processing technique are used, and a frame comb filter that utilizes the correlation in the time direction of the image (frame correlation, field correlation) is used. / C separation (luminance / chromaticity separation), double scanning line density by inter-field interpolation, and progressive scanning conversion are considered to be introduced (Japanese Patent Laid-Open No. 58-115995). 58-
No. 79379). However, as is well known, these means for improving the image quality exert an effect only on a still image having a strong frame correlation and a strong field correlation, but rather cause a disturbance on a moving image. Therefore, the motion of the image is detected by taking the difference between the frames, and when the image is determined to be a still image, processing on the time axis such as a frame comb filter and inter-field interpolation is performed. Is known to introduce a so-called motion-adaptive process for switching to spatial processing in a field and aim at practical use (Japanese Patent Laid-Open No. 59-45770). [0003] The above-mentioned techniques are based on a color subcarrier frequency f _SC , a horizontal scanning frequency f _H , and a vertical scanning frequency f _V.
But accurately manage television signal in a predetermined frequency relationship (hereinafter, standard signal hereinafter) but its effect on can be expected, f _SC as household VTR or personal computers, f _H, f _V However, there is a problem that the effect cannot be obtained with respect to a television signal (hereinafter, referred to as a non-standard signal) which does not have a predetermined frequency relationship. For example, in the case of the NTSC system, f _SC and f _H have the following relationship: f _SC = (455/2) f _H Also, between f _H and f _V the, [0006] [number 2] _{f H = (525/2) · f} V = (262 + 1/2) · f V the relationship is defined. [Equation 2] indicates that the scanning lines are interlaced. Considering the pixels on the two adjacent scanning lines of the current field, the pixel of the scanning line of the previous field corresponds to the middle thereof. . On the other hand, from [Equation 1] and [Equation 2], [Equation 3] f _SC = (119437 + 1/2) · f _V / 2 is obtained, which means that the phase of the color subcarrier is one frame period (frequency f _V / 2) It indicates that the signals are out of phase with each other. As described above, since the above relationship is established in the standard signal, frame comb processing and inter-field interpolation can be performed. However, in the case of a non-standard signal whose frequencies f _SC , f _H , and f _V do not satisfy the above formulas (1) and (2), the correspondence of pixels between fields and the inversion of the color subcarrier between frames are not considered. Since the relationship is no longer established, it becomes impossible to accurately separate the luminance signal and the chrominance signal by the inter-field scanning line interpolation and the frame comb. Therefore, when it is determined that the image is a still image, the image quality is significantly deteriorated by the above processing.
As described above, in the related art, the characteristics of standard / nonstandard signals are not taken into consideration, and it is difficult to perform appropriate processing on nonstandard signals. An object of the present invention is to provide a digital television signal processing apparatus which performs a signal processing circuit capable of obtaining a good image quality even for a non-standard signal. To achieve the above object, the present invention separates a sync signal from an input television signal and generates a first pulse based on the separated sync signal. A means for generating a second pulse synchronized with a color burst signal included in an input television signal, and first and second frequency dividers for frequency-dividing the first and second pulses by a predetermined number, respectively. And a comparing means for comparing the outputs of the first and second frequency dividers to detect whether the input television signal is a standard signal or a non-standard signal, and input television signal based on the detection result. The optimal processing corresponding to is performed. Further, in order to ensure the detection operation, the disturbance of the burst reproduction control voltage at the time of color demodulation is detected for a non-standard signal which is extremely close to the standard signal such as the still mode of the optical video disc player. Disturbance detection means is provided so that the standard signal or non-standard signal can be determined. The above object is achieved by the above means. The first frequency divider frequency-divides the sync separation output f _H by m (m = 1, 2, ...), while the second frequency divider controls the color burst signal f _SC. Is divided by 455 m / 2, and the comparing means compares the output cycles of both. If the input television signal is a standard signal, [Equation 1] is satisfied, so that the comparison means outputs a coincidence output and determines that it is a standard signal. On the other hand, if the input television signal is a non-standard signal, [Equation 1]
Is not established, the comparing means outputs a non-coincidence output and determines that the signal is a non-standard signal. Next, in the still mode of the optical video disc player, the phases of the color subcarriers of the output video signal are the same between frames. For this reason, a frame comb filter using an inverse phase relationship cannot be used, and becomes a non-standard signal. In this case, the color subcarrier is one in one frame.
At this point, the control voltage for color burst reproduction is disturbed. Therefore, the control voltage disturbance detecting means sets a predetermined threshold value, and when the threshold value is exceeded, determines that the signal is a non-standard signal. Based on the above detection result, the signal processing circuit switches the motion adaptive spatiotemporal luminance / chromaticity separation circuit to in-space processing for the reason described later. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a signal and synchronization processing circuit by a television signal processing apparatus according to the present invention will be described below with reference to FIG.
Will be described. Also, all the descriptions below are based on NTSC
The method will be described as an example. In FIG. 1, 101 is a video signal input terminal, 105 is a band pass filter (BPF), 106 is a color demodulation circuit, 107 and 108 are A / D converters for luminance signals and chrominance signals respectively, and 109 is. Motion adaptive luminance (Y) separation circuit (frame comb filter and line comb filter), 110 is a motion adaptive color (C) separation circuit (same as above), 1
17, 118 are D / A for luminance signal and D / A for color signal, respectively.
Converter, 119 is an RGB conversion circuit, 120 is a CRT, 121 is a burst signal extraction circuit, 122 is a phase comparator, 123 is a low-pass filter (LPF), 124 is a voltage controlled oscillator, 125 and 126 are frequency dividers, 127 is a sync separation circuit, 128 is a phase comparator, 129 is an LPF, 13
0 is a voltage controlled oscillator, 131 is a frequency divider, 132 is a horizontal excitation / output circuit, 133 is a flyback transformer, 135
Is a frequency divider, 136 is a period comparator, 137 is an integrator, 14
0 is a pre-processing unit, 141 is a horizontal synchronous reproduction unit, 142 is a control voltage disturbance detection circuit, and 143 is an OR circuit. First, an outline of the operation of the signal processing system will be described. When the standard signal is input, the input signal is input to the luminance signal A / D converter 107 as it is. On the other hand, for the color signal, only the color signal band is extracted by the BPF 105 and the color difference signal is obtained by the color demodulation circuit 106. The color signal A / D converter 108 receives the signal and converts it into a digital signal. For the luminance signal below,
The motion-adaptive spatiotemporal luminance separation circuit 109 obtains a luminance signal without crosstalk from the color signal, and the D / A converter 1
At 17, an analog luminance signal is obtained. As for the color signal, a color signal without crosstalk from the luminance signal is obtained by the motion-adaptive color separation circuit 110, and the D / A converter 118 outputs an analog color signal. The luminance signal / color difference signal outputs of the D / A converters 117 and 118 are converted into RGB signals by an RGB conversion circuit 119,
Drive 0. Next, the operation when a non-standard signal is input will be described. When a non-standard signal is input, the Y separation and C separation circuits 109 and 110 in the figure perform processing in the space, and the D / A converters 117 and 118 and the RGB conversion circuit 1
The cathode ray tube 120 is driven via 19. Next, a method of generating a clock used for signal processing will be described. In this embodiment, a clock signal generated based on a color burst signal included in an input signal and a clock signal generated based on a horizontal synchronization signal included in the input signal, that is, a burst lock clock and a line lock clock are used. A burst signal extracting circuit 121 extracts a color burst signal (frequency f _SC ) from the input video signal. Voltage controlled oscillator 1
24 oscillates at a frequency of 4 f _SC , and the frequency divider 125
, And the phase is compared with the color burst signal by the phase comparator 122, and the error voltage is supplied.
On the other hand, the sync separation circuit 127 extracts a sync signal from the input video signal and inputs the sync signal to the phase comparator 128. The voltage controlled oscillator 130 still oscillates at a frequency of 4f _SC , and the frequency divider 131 divides the frequency by 910 to compare the phase with the synchronous separation output, and receives the error voltage supply. The outputs of the voltage controlled oscillators 124 and 130 become a burst lock clock and a line lock clock, respectively. The burst lock clock is directly D / A converter 117, 118, A / D
The converters 107 and 108 are driven. The reason why the signal processing system is switched between the standard signal and the non-standard signal will be described below. Figure 2
Shows (a) a color burst signal, (b) a horizontal synchronization signal, (c) a burst lock clock, and (d) a line lock clock for the standard signal and the non-standard signal. First, regarding the standard signal, since the color burst signal f _SC exists in 455/2 cycles in one horizontal synchronization period ((a) in FIG. 4), the burst lock clock and line lock clock of 4 f _SC have one horizontal cycle period. To 9
There are 10 cycles (Figs. (C) and (d)). The comb filter separates a luminance signal and a chrominance signal by performing an operation between signals separated by a predetermined period such as one frame period or one line period. In this figure, no matter which clock is used, the color burst phase of the signal separated by 910 clocks is inverted, while the luminance signal is in phase, so if the sum of the signals separated by the predetermined interval is taken, the difference is taken. A color signal can be obtained. Next, a case where a non-standard signal is input will be described. The non-standard signal is 1 color burst signal as shown.
There are no 455/2 cycles in the horizontal synchronization period ((a)
Figure). Now, it is assumed that 455/2 cycles or more exist in one horizontal synchronization period. Therefore, in this case, the burst lock clock exists for 910 cycles or more in one horizontal synchronization period (FIG. 10C), while the line lock clock exists for exactly 910 cycles (FIG. 10D). However,
Considering a signal that is 910 cycles away from the burst lock clock, the phase of the color burst signal is inverted.
Therefore, if the high-frequency component of the luminance is small, the color signal can be extracted by taking the difference between the signals separated by the predetermined period, and the luminance signal can be obtained by subtracting this signal from the input video signal. it can. When the luminance signal has a high-frequency component, an operation is performed at a point where the pixel of the luminance signal is different according to the above sum, so this component is missing and leaks into the color signal, but when viewed between the scanning lines, Since the pixel difference is small, the influence is small. However, when a frame comb filter is adopted, the pixel difference between frames is the accumulation of the difference between scanning lines, so that the error is large and the separation performance of the comb filter is greatly deteriorated. Therefore, a frame comb filter cannot be used. As described above, the clock used may be either the burst lock clock or the line lock clock for the standard signal, and the burst lock clock is good for the non-standard signal. However,
Comparing the burst lock clock with the line lock clock, the former is often configured using a crystal oscillator, and the latter is often configured using an oscillator using an LC filter.
When comparing (clock jitter, etc.), the former is superior. Therefore, it is possible to obtain better characteristics by using the burst lock clock for the standard signal. Next, a method of detecting a standard signal or a non-standard signal will be described. As a first means for this detection, the pulses related to the burst lock clock and line lock clock generated by the above-mentioned method are used. First, the output of the frequency divider 125 is used as a pulse related to the burst lock clock as shown in FIG. Although the frequency of this output is f _SC , if this frequency is divided by the frequency divider 126, for example, 455 · 525/4, a pulse corresponding to the vertical frequency can be obtained by [Equation 1] and [Equation 2]. For the frequency division of (455.525 / 4),
The clock signal of 4f _SC may be obtained by dividing the clock signal by 455/525.) On the other hand, the output of the frequency divider 131 is used as a pulse related to the line lock clock. Since the frequency of this output is f _H , if this is frequency-divided by, for example, 525/2 by the frequency divider 135, a pulse corresponding to the vertical frequency can also be obtained. For these two pulses,
As shown in FIG. 1, for example, when the frequency divider 126 is reset by the output of the frequency divider 135, the output of each frequency divider becomes as shown in FIG. That is, in FIG. 3, the frequency divider 135 generates a reset output as shown in FIG. 3A and an output having a predetermined width which rises before this reset pulse and falls later as shown in FIG. I do. The former reset pulse operates as a reset pulse for the frequency divider 126, and the frequency divider 126 starts frequency division based on the reset pulse. It occurs at different timings depending on whether the signal is a standard signal or a non-standard signal as described below. That is, if the input signal is a standard signal,
Since [Equation 1] and [Equation 2] are established, the timings of the output of the frequency divider 126 and the reset output of the frequency divider 135 are substantially the same, as shown in FIG. Therefore, the frequency divider 1
The 26 outputs are included in the output of the frequency divider 135. The comparator 136 confirms the coincidence by, for example, taking a logical product of the two, and determines that the signal is a standard signal. However, if the input signal is a non-standard signal, [Equation 1] and [Equation 2] do not hold.
As shown in FIG. 6D, the output of the frequency divider 126 is not included in the output of the frequency divider 135. The comparator 136 detects this mismatch and determines that the input signal is a non-standard signal. The pulse width of the output from the frequency divider 135 determines the standard and non-standard detection sensitivities. That is, if the pulse width is wide, the nonstandard signal can be easily detected as the standard signal, and if the pulse width is narrow, the standard signal is determined to be the nonstandard signal. Further, it is assumed that the comparator 136 operates every vertical period, and the frequency divider 126 sets f _SC to 455 · 525/4.
The frequency division and the frequency divider 135 have been described as frequency division by 525/2, but the determination cycle is not limited to 1 vertical cycle, and
The scanning cycle or one frame cycle may be used, and an arbitrary value can be selected. When determining whether the signal is a standard signal or a non-standard signal in this way, if the impulse noise is mixed in, the malfunction of the sync separation circuit 127 frequently occurs. Therefore, the output of the frequency divider 134 cannot be obtained at normal timing, and the output of the frequency divider 135 also malfunctions.
In this case, even if the input signal is a standard signal, it is determined to be a non-standard signal.
7 is added. FIG. 4 is a block diagram showing the details. In the figure, 401 is an up / down counter, 402 is an OR circuit, and 403 is an RS flip-flop. The match output of the comparator 136 is input to the up count terminal of the up / down counter 401, and the mismatch output is input to the down count terminal. Now, let us say that the initial value of the up / down counter 401 is N, and the carry output and the borrow output are obtained when the count values are 2N and 0, respectively. Further, the OR circuit 402 creates a load pulse for the counter 401 in response to the generation of these pulses, and the initial value N is set by this. In this case, since either a match or a mismatch input can be obtained every vertical cycle, the up / down counter 401
Performs up-counting or down-counting, but a carry output or a borrow output is generated only when one input is more than N times more than the other input, and determines whether to set or reset the RS flip-flop. Therefore, even if the sync separation circuit 127 malfunctions, the standard / non-standard determination is not affected. Next, a description will be given of a method of detecting disturbance of the control voltage used for color burst reproduction for color demodulation, which is the second means for detecting a non-standard signal. In FIG. 1, the frequency divider 125
Is a color burst reproduction output having a frequency of f _SC . If this output is applied to the color demodulation circuit 106, color demodulation can be performed. By the way, in a home optical video disk player, a signal reproduced by special reproduction such as still mode, quick play, or slow mode is accompanied by a track jump of the disc.
Since the signal phase of the color burst is discontinuous, it can be said that it is a kind of non-standard signal. At this discontinuity of the burst signal phase, the burst phase input to the phase comparator 122 suddenly changes, so the output of the phase comparator 122 is disturbed, and as a result, the voltage controlled oscillator 124 of the voltage controlled oscillator 124 is disturbed until the phase is synchronized again. The output clock frequency is also disturbed. Therefore, even if the clock is counted a predetermined number and delayed by one frame, an error corresponding to the disturbance of the clock occurs, and the pixels do not correspond between the frames. Instead, the image quality is degraded. That is, such signals are non-standard signals. In this case, since [Equation 3] does not hold, the detection can be performed by the first detection means. However, since the error is extremely small, it is necessary to take measures to increase the detection sensitivity or perform long-time counting. . Each of these methods has a problem of erroneous determination and a long detection time, and is not practical. Therefore, in the present embodiment, at the discontinuity point of the color burst signal, the control voltage of the voltage controlled oscillator 124 is used to be disturbed. , And the OR of the output of the integration circuit 137 is obtained by the OR circuit 143, thereby making a comprehensive judgment. FIG. 5 shows the configuration of the disturbance detection circuit 142.
In the figure, 151 is an amplifier circuit, 152 is an absolute value circuit, 153 is a comparator, and 154 is an RS flip-flop. The amplifier 151 includes the LPF shown in FIG.
The output of 123 is input. The amplifier 151 amplifies this and sends it to the absolute value conversion circuit 152. Absolute value conversion circuit 152
Rectifies this only in the positive direction and sends it to the comparator 153, as shown in FIG. The comparator 153 has a predetermined threshold and generates an output as shown in FIG.
4 is set as shown in FIG. Thereby, it can be determined as a non-standard signal. When the RS flip-flop 154 is reset with a pulse of one vertical cycle from the frequency divider 135, for example, a signal can be determined on a field basis. Next, reproduction of horizontal synchronization will be described.
As described above, the voltage controlled oscillator 130 oscillating at the frequency of 4f _SC in FIG.
It is divided by 0 to generate a horizontal deflection pulse having a frequency f _H. This output is passed through a horizontal excitation / horizontal output circuit 132 and a deflection yoke and flyback transformer 1 not shown.
Drive 33. The deflection yoke performs horizontal scanning of the cathode ray tube, and the flyback transformer 133 generates various high-voltage power supplies for driving the television receiver. The output pulse of the flyback transformer 133 is supplied to the phase comparator 128. As described above, the horizontal synchronizing signal can be reproduced by one PLL circuit with reference to the output of the sync separation circuit 127. Further, as is already clear, in this embodiment, the line lock clock and the detection pulse of the standard / non-standard signal are generated by using this PLL, so that the hardware is efficiently used. ing. FIG. 7 shows a second example of the horizontal synchronous reproduction section 141 of FIG.
FIG. In FIG. 7, 601 is a phase comparator, 602 is an LPF, 603 is a voltage controlled oscillator, and 604 is a frequency divider, and the same parts as those described above are designated by the same reference numerals. In this embodiment, a PL for generating a pulse related to a line lock clock for detecting a standard signal or a non-standard signal is output to the output of the sync separation circuit 127.
L and the horizontal synchronous reproduction unit are configured by separate PLL circuits. In many cases, there is no problem if the configuration shown in FIG. 1 is used, but the following problem may occur depending on the television receiver. That is, the flyback transformer 133 receives the pulse of the horizontal excitation / horizontal output circuit 132 on the primary side and generates a high voltage on the secondary side. The high voltage is used as the anode voltage of the cathode ray tube 120. If the video signal reproduces a relatively bright screen, a large beam current flows from the anode to the cathode of the cathode ray tube 120, and as a result, the high voltage fluctuates. Appear on the next side. Therefore, the pulse width and peak value of the input pulse to the frequency divider 134 (the output pulse of the flyback transformer 133) change. This means the following: That is, even if the input video signal is a regular NTSC signal and has no horizontal frequency shift or jitter, depending on the brightness of the video signal,
An error voltage is generated at the output of the phase comparator 128 with respect to the voltage controlled oscillator 130. Therefore, even if the input signal is a regular standard signal, it may be determined as a non-standard signal depending on the magnitude of the error voltage. However, if the configuration as shown in FIG. 7 is adopted, the standard / non-standard detection circuit is composed of the PLL system which does not include the flyback transformer 133, so that stable detection which does not depend on the contents of the video signal is performed. It becomes possible to perform an operation. In FIG. 8, the voltage controlled oscillator 603
The oscillation frequency is not necessary to select the 4f _SC, for example 2
Set it to a low frequency of f _{H and use the} frequency divider 135 to set 525.
By dividing the frequency, a comparison pulse having one vertical cycle can be obtained. As described above, according to the present invention, whether the input signal is a normal standard signal or a non-standard signal is automatically detected, and the signal processing system is switched based on the detected result. Therefore, good image quality can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a waveform diagram showing a standard signal and a non-standard signal. FIG. 3 is a block diagram showing the operation of a standard / non-standard signal detection circuit. FIG. 4 is a block diagram showing details of an integrating circuit. FIG. 5 is a block diagram showing a control voltage disturbance detection circuit. FIG. 6 is an operation waveform diagram thereof. FIG. 7 is a block diagram showing a modified embodiment of FIG. 1; [Explanation of Codes] 109 ... Motion adaptive Y separation, 121 ... Burst extraction, 127 ... Synchronous separation, 128 ... Phase comparator, 130 ... Voltage controlled oscillator, 133 ... Flyback transformer, 142 ... Disturbance detection circuit, 401 ... Up-down Counter, 402 ... OR circuit, 403 ... RS flip-flop, 601 ... Phase comparator, 602 ... LPF, 604 ... Divider.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuo Nakagawa             Stock, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Home Appliance Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] 1. Digitally processes the television input signal,
In a television signal processing device for reproducing video, a spatiotemporal signal processing circuit including a luminance / chromaticity separation circuit that performs motion-adaptive temporal processing and spatial processing, and detection for detecting whether the input signal is a standard signal or a nonstandard signal And a switching means for switching the luminance / chromaticity separation circuit to processing in space when the non-standard signal is detected, and the video signal processed by the switching means is reproduced. A digital television signal processing device characterized by the above. 2. The detection means for detecting whether the input signal is a standard signal or a non-standard signal is at least two types of clocks,
A first clock having a relatively good oscillation S / N characteristic, a clock generating means having a second clock having a relatively good tracking characteristic, and an output of the clock generating means are inputted. The digital television signal processing device according to claim 1, further comprising a comparator. 3. The digital television according to claim 1, wherein the detecting means for detecting whether the input signal is a standard signal or a non-standard signal includes a detecting means for detecting discontinuity of the color burst signal. Signal processing device. 4. The detecting means for detecting whether the input signal is a standard signal or a non-standard signal has a first clock having a relatively good oscillation S / N characteristic and a second clock having a relatively good tracking characteristic. 2. A clock generating means having the clock of claim 1, a comparator for inputting the output of the clock generating means, and a detecting means for detecting discontinuity of the color burst signal. The described digital television signal processing device.