JP2871715B2 - Key signal generation circuit for color supermarket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a case where superimposed characters or the like are added to a video signal, particularly when superimposed characters or the like are colored. And a key signal generation circuit for color superimposition for coloring characters and shadows in an arbitrary color.

[Prior Art] Conventionally, when superimposing characters and the like on a television screen, a method of using white characters and adding a black shadow to the characters has been often used. Recently, color characters have been used, and the method shown in FIGS. 4 and 5 has been proposed in which both characters and shadows are colored in an arbitrary color. In this method, the color signal to be superimposed is supplied to terminal 1
And insert it into the insert signal by the separation circuit 15.
S _in and a keying signal S _k ′.

FIG. 5 shows a separating circuit 15, in which the keying signal S _k 'is obtained through a phase shifter 19, the envelope waveform of the chrominance signal is obtained by a detector 20, the delay by the detector 20 is adjusted by a delay 21, and the band eliminator 22 The envelope waveform of the luminance signal is obtained by eliminating the color signal, and is added to the non-additive mixing (NAM) circuit 23 together with the envelope waveform of the color signal, and the larger one is selected and obtained. The insert signal S _in is obtained by aligning the color super signal from the phase shifter 19 by the delay 25 and gating by the gate 26.

From S _k ′, 2 is provided by delay 5.6 and NAM circuit 7.
Spread the height up and down only pieces of Dere content, by Dere 8.9 and NAM circuit 10 makes the gate signals S _k which widened to the left and right by two Dere minute. On the other hand, the insert signal S
_in matches the phase with the above S _k by the delays 16 and 17, selects the color of the insert signal by the switch 18, either the original color or the color of the super color signal generator 13, and selects the color of the shadow color signal generator 14. Output and a shadowed supercolor signal S _s in addition to the mixer 12 along with the keying signal aligned with the S _k by the delays 5 and 11.
Occurs. Additional S _k · S _s and the video signal input from the terminal 3 (hereinafter referred to as "base signal".) Was added to the mixer 4, and to obtain an output signal super super signal with the required shadow.

[Problems to be Solved by the Invention] The problem in the above method is that when a color signal is selected, the detected key signal has a phase change described later, and the image quality is significantly reduced depending on the input color super signal. It is to be.

In the composite signal, the interleaving in which the phase of the color burst signal is different by 180 degrees between adjacent scanning lines in the same field and every different frame causes problems such as cross color and cross luminance. As shown, the color signal of the super signal of the adjacent scanning line and the half cycle (about 0.14 μm)
s) When the positions of the same phase are shifted, the rising point of the color signal of the color super signal is shifted for each scanning line, so that there is a phenomenon that the line of the color change in the vertical direction is jagged. This is called "color dot crawling", and NT
It comes from the essence of the SC method. Therefore, the rising point of the key signal detected from the color signal also has a different phase change for each scanning line. When the color signal is gated by the key signal whose phase changes in this way, the rising point of the luminance signal changes for each scanning line similarly to the key signal, and the quality further deteriorates. Therefore, when a color signal is used as a key signal in the key signal detection circuit, it is desirable to provide the above-described key signal phase change prevention circuit. Even if this prevention processing is performed, jitters occur due to the setting of the color phase and the clip point, and the quality is reduced to such an extent that the line of the color change in the vertical direction becomes slightly thicker.

As shown in FIG. 7A, in the case of the Q signal of the NTSC system formed by a gate pulse or the like as shown in FIG. 7 (A), a slope of about 0.84 μs is given at the maximum. The output signal from an NTSC encoder such as a color camera
(B) As shown in the figure, a waveform is obtained by synthesizing a luminance signal and a color signal shaped so that the phase of the 50% value of the rising portion of the luminance signal coincides with the phase of the 50% value of the slope of the color signal. Furthermore,
Each signal can be gated by a luminance signal and added to the luminance signal, or a signal generated by a computer or the like can obtain a waveform without a slope as shown in FIG. 7 (C). At this time, as shown in FIG. 7 (D), the rising of the luminance signal coincides with the 0 phase of the chrominance signal (hereinafter referred to as “zero cross”), and the chrominance subcarrier is apparently twice the normal chrominance subcarrier. If the frequency is set to 3.58 MHz × 2 (hereinafter referred to as “double frequency”) in the case of the NTSC system, no phase change of the key signal occurs even if the color signal is used as the key signal, but the condition of the double frequency is If the zero-cross condition is not satisfied even if it is satisfied, the level in FIG. 7D becomes lower than the level, so that the detection becomes unstable depending on the slice level, and a phase change of the key signal occurs. . Although a waveform created by a computer can satisfy both of these conditions, a waveform created by a gate cannot always satisfy the condition of zero crossing, so that a phase change of a key signal occurs. Next, in the case of an NTSC signal having a slope as shown in FIGS. 7 (A) and 7 (B), if the above conditions of the double frequency and the zero crossing are not satisfied, a phase change of the key signal occurs, and the The color of the left and right edges of the signal and the shadow signal becomes lighter and the line becomes thinner, and the super signal and the shadow signal and the base signal and the shadow signal are mixed with each other. This phenomenon will be described with reference to a color super signal waveform shown in FIG. 7A formed by a gate pulse or the like.

FIG. 8 (A) is a color super signal having a sloping portion as in FIG. 7 (A). Having the inclined portion means that the saturation changes along the inclined portion, and the degree of coloring is deeper at the center and lighter at the left and right. For this reason, generally, both ends of a superimposed color character appear thin and thin, and if a color signal is used as a key signal, the character itself may not be clearly seen.
(B) shows the envelope waveform of the luminance signal, and (C) shows the envelope waveform of the chrominance signal. Therefore, the waveform (D) in which the envelope waveforms of the luminance signal and the chrominance signal are passed through the NAM circuit is a waveform in which a part of the step waveform is inclined. The insert signal S _in is (A)
The waveform shown in FIG. 5D is linearly gated by the gate 26 shown in FIG. 5 so that the gain at the end is reduced. As shown by the solid line, the thinning is emphasized as shown in FIG. Waveform. Next, S _in is phase-shifted by the delays 16 and 17 to the center of the gate signal S _k (waveform expanded vertically and horizontally by the delays 5 and 6 and 9 and NAMs 7 and 10). select the color of the super signal, and outputs it as S _s after having added a shadow signal. At this time, since the shadow signal is gated by -S _k 'in FIG. (I), the shadow signal remains due to the slope of the gate waveform end as shown in FIG. When the original super color signal is selected, the waveform of (E) is keyed by the waveform of (H), so as shown in FIG. (J), the amplitude at the end further decreases due to the further decrease in gain, and thinning is promoted. Waveform. When mixing the super signal and the shadow signal, the remaining portion of the shadow signal is mixed into the super signal. In the mixer 4, the _Sk signal shown in FIG.
The S _s signal is keyed, the base signal is gated by -S _{k in the} diagram (G), and the former is inserted into the latter. At this time, as shown in the diagram (K), the shadow signal is thinned and the shadow signal is reduced. The base signal is mixed in the signal. As described above, the obtained output signal not only causes the thinning, but also causes a complicated mixing phenomenon, and significantly degrades the quality.

When a color signal waveform having an inclined portion is used as a key signal as described above, thinning and mixing by the inclined portion can be avoided by slicing the key signal waveform at a level higher than the level of noise or the like. NTSC created by encoder
In the case of the waveform shown in FIG. 7B, if the slice is performed at a level of 50% or more, an inclined portion remains, and the phenomenon of thinning and mixing is inevitable.

[Means for Solving the Problems] The present invention provides a separating means for separating a luminance signal and a carrier chrominance signal from a composite color super signal, and adding a positive characteristic signal and an inverse characteristic signal of the separated carrier chrominance signal. Envelope detection means for detecting an envelope of the signal obtained by the above, an output means for outputting a signal obtained by slicing a signal from the envelope detection means at a predetermined level, and a level of a luminance signal from the separation means. A detecting means for detecting, and a signal of an envelope waveform of the luminance signal when the detection result of the detecting means is higher than the predetermined level, and an output signal of the output means as a key signal when the detection result is lower than the predetermined level. And means for performing the operation.

[Operation] Since the envelope waveform of the luminance signal is close to a rectangular system, if this level is sufficiently larger than, for example, noise, grain or shading level, by using this as a gate signal, there is no defect due to a phase change of the key signal. It is possible to output a high-quality super signal without thinning and mixing. When the luminance signal is lower than the above level,
If a square wave produced by slicing a double-frequency envelope waveform of a color signal at an appropriate point such as the level is used as a gate signal, the presence of a phase change of a key signal device and the presence or absence of a slope portion of a color signal of a super signal Irrespective of this, a high-quality color super signal with color shadow without thinning and mixing phenomenon can be output.

[Example] The luminance signal of the television signal has a frequency band of 4 MHz,
The envelope waveform is also substantially rectangular over the entire range of the signal. If this luminance signal is separated by, for example, a comb filter, the envelope waveform of the original signal can be reproduced as it is without dulling the edges, so if this is used as the key signal of the color super signal, the circuit is simple. In addition, a high quality color shadow super signal can be generated without any fluctuation of a luminance signal for each scanning line resulting from the use of a key signal which has undergone a phase change due to thinning, mixing phenomenon, and color signal interleaving. Therefore, if the quality or level of the luminance signal is equal to or higher than the allowable value, it is preferable to use the envelope waveform of the luminance signal as the key signal. If the amplitude of the color signal is large when the quality or level of the luminance signal falls below the allowable value, it is advisable to use the envelope waveform of the color signal. At that time, instead of using the envelope waveform of the original color signal as it is, it is made a double frequency, sliced the envelope waveform at a fixed rate from the bottom, amplified and made a rectangular wave, and used this as a key signal It is the gist of the present invention that the present invention can be used to create a high quality color shadow super signal regardless of the presence or absence of the inclined portion of the color super signal.

Color characters to be superimposed are often created by computer-based character generators, in which case it is possible to provide a sufficient luminance signal for any color. In addition, since the colors of characters and shadows can be colored in any colors, if the colors are colored electronically, sufficient brightness can be given even when handwritten characters are input using a telop card. on the other hand,
When entering characters etc. written in any color on the telop card, when entering characters etc. described in other samples such as catalogs, when entering characters with only color signals excluding luminance signals, etc. In some cases, the luminance may fall below the allowable value. However, in such a case, the key signal generated from the luminance signal can be used in most cases.

FIG. 1 is a system diagram of a key signal generation circuit according to the present invention. The color super signal input from the terminal 31 performs a color phase adjustment in the phase shifter 32, and finally corrects a color change by a phase change generated by a subsequent circuit. Next, the luminance signal Y and the chrominance signal C are separated by the Y / C separator 33. For this, a comb filter having a good separation characteristic is used as described above. The separated luminance signal Y is an amplifier
At 34, the signal is amplified at a constant rate to obtain a waveform Y 'proportional to the envelope waveform of the luminance signal.

The separated color signal C is added to an adder 39 by a signal amplified to a positive characteristic by an amplifier 37 and amplified to a reverse characteristic by an inverter 38. As described above, since the phase of the color signal is different by 180 degrees between the adjacent scanning lines, the frequency becomes twice as shown in FIG. 2, and as a result, the phase change of the key signal is prevented. By doing so, there is an effect that the envelope detection by the envelope detector (LPF) 40 at the next stage becomes easy. When the color signal has a slope, the envelope waveform C 'has a slope as shown in FIG. 3 (A). 45 is a peak detector which detects the peak value of the envelope waveform from the envelope detector 40 and sets it as a DC voltage _Cmax , adds this to one terminal of the DC amplifier 46, and feeds it back to the other terminal through the variable resistor 47. And generates a voltage proportional to the input voltage. This voltage is used as the control voltage of the slicer 41 set to saturate the output, and the variable resistors 43 and 47 are adjusted to adjust the level of 10 to 15% of the input waveform as shown in FIG. Slice.
The rise of the output waveform is set at an appropriate time by the resistor 42. Therefore, the output waveform C "(FIG. 3 (B)) is a waveform having a certain level and a width slightly smaller than the bottom of the envelope waveform C 'of the color signal C and having an arbitrary rise time. Is added to the level controller 44. A control voltage is applied to this level controller by a DC amplifier 48, and the output level C "(third
The variable resistor 49 is adjusted so that ((C) FIG.) Becomes equal to _Cmax . The level controller 44 can also be configured by using a comparator and applying an input voltage to one terminal and a control voltage to another terminal.

The Y 'and C obtained as described above are added to the switch 35 controlled by the comparator 54. When Y' is higher than a predetermined level, Y 'is output to the output terminal 36. C ". In order to perform such control, Y 'is added to one terminal of a comparator 54 via a resistor 51, and the other terminal is connected to a predetermined terminal by a resistor 52 and a variable resistor 53. A positive voltage equal to the level may be applied and the output voltage may be used to control the switch 35. The predetermined level may be equal to or higher than the level of noise, grain, shading, streaking, sag, etc. included in Y '. Usually, 100 mv is sufficient, and the comparator 54 is provided with an appropriate hysteresis characteristic by applying feedback or the like to prevent chattering when the switch 35 is switched.

Y 'or C produced in this manner is a waveform whose amplitude is proportional to the peak value of the luminance signal or the chrominance signal and has an appropriate slope, and the super signal or the shadow signal shown in FIGS. Can be used as a linear key signal. As described above, C ″ has a constant level and the same width and rise time as C ″, and may be used for processing that produces an effect different from that of the linear key in the processing of the super signal or the shadow signal. At this time, C ″ is added to the switch 35 instead of C,
What is necessary is just to output from the terminal 36. In the case of the input shown in FIG. 7B, the slice level of the slicer 41 may be set to a point which is approximately 50% of the input waveform.

The functions of the circuits described above can be easily realized by other modified known circuits, and are not limited to the circuits of the embodiments.

Although the above embodiment is based on the NTSC system, it is clear that the present invention can be applied to the PAL system.

[Effect of the Invention] As described above, in the present invention, the color super signal of most characters and symbols has a luminance signal larger than the level of noise, grain or shading.
Keying by a luminance signal becomes possible, and there is a great benefit in giving priority to a luminance signal which has a waveform close to a rectangular wave and has no defects such as thinning and mixing.

Even when the color signal is switched to the color signal, even if the phase change of the key signal and the scanning of the luminance signal caused by the double frequency effect do not fluctuate for each scanning line, and the color super signal has a slope, the envelope waveform By slicing at the bottom or at an appropriate point, there is no thinning, mixing phenomenon,
As for the key signal, the same effect as that obtained by the luminance signal can be obtained, and the total effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram of a key signal detection circuit according to the present invention, FIG. 2 is a waveform diagram showing the waveforms of the positive and reverse characteristics of the color signal, FIG. 3 is a waveform diagram of each part of the color signal detection circuit, FIG. FIG. 5 is a circuit diagram of a color super signal and shadow signal generation circuit according to the prior art, FIG. 5 is a circuit diagram of a key signal and insert signal generation circuit according to the prior art, and FIG. FIG. 7 is an explanatory diagram of an envelope waveform at the rising edge, FIG. 7 is a diagram showing various waveforms of the color super signal, and FIG. 8 is a signal waveform diagram of the circuits in FIGS. 1 ... input terminal, 2 ... color super signal and shadow signal generator, 3 ... video signal input terminal, 4 ... mixer, 5, 6, 8, 9, 11, 16, 17 ... delay, 7. 10 ... NAM circuit, 12 ... Mixer, 13 ... Super color signal generator, 14 ... Shadow color signal generator, 15 ... Separation circuit, 18 ... Switch, 19 ... Phase shifter, 20 ... Detector, 21/25 ... Delay, 22 ... Band eliminator, 23 ... NAM circuit, 24 ... Blanking gate, 26 ... Gate, 32 ... Phase shifter, 33 ... Y / C separation circuit, 35… Switch, 37 …… Amplifier, 38 …… Inverter, 39 …… Adder, 40 …… Detector, 41 …… Slicer, 43 ・ 47 …… Slice level adjustment variable resistor, 44 …… Level controller 45, Level detector 46, 48 DC amplifier for control, 49 Variable resistor for C "level adjustment , 53 appropriate level settings for the variable amplifier for ...... noise, 54 ...... comparator.

Claims (1)

(57) [Claims] 1. A separating means for separating a luminance signal and a carrier chrominance signal from a composite color super signal, and an envelope of a signal obtained by adding a positive characteristic signal and an inverse characteristic signal of the separated carrier chrominance signal. Envelope detection means for detecting the signal; output means for outputting a signal obtained by slicing the signal from the envelope detection means at a predetermined level; detection means for detecting the level of the luminance signal from the separation means; Means for selecting the signal of the envelope waveform of the luminance signal when the detection result of the means is higher than the predetermined level, and selecting the output signal of the output means as a key signal when the detection result is lower than the predetermined level. Characteristic key signal generation circuit for color supermarket.