JPS58138193A - Color frame detecting device - Google Patents

Abstract

PURPOSE:To realize an inexpensive color frame detecting device which requires no adjuster and to be handled easily, by obtaining the 1st and 2nd signals by saturating and amplifying divided values of the positive and negative peak voltages of color bursts, and latching the burst flag pulse then obtaining the positive negative leading edge position signals of color bursts. CONSTITUTION:Signals having only luminance component and only chromaticity component are obtained through an LPF1 and BPF2, respectively. The luminance component is supplied to a pulse generating circuit 4 and a burst flag pulse 23 and frame pulse 24 are produced. A color burst 25 is fetched by the pulse 23. Among the color burst 25, those which detect a crest value and invert the polarity are divided, and the positive and negative divided values 26 and 27 of the crest value of the color burst 25 are obtained. When the color burst 25 is saturated and amplified at the divided values 26 and 27 and pulse signals 28 and 29 are obtained and the pulse 23 is latched by latch circuitsI12 and latch circuit II 13, signals 30 and 31 representing the positive and negative leading edge position of the color burst are obtained. When one of the signals is latched by latch circuit III 14 at the other side, a signal 32 which inverts at every one horizontal synchronizing cycle is obtained. When the signal 32 is latched by the pulse 24 at latch circuit IV 15, a frame pulse 33 is obtained.

Description

[Detailed description of the invention] The present invention relates to a color frame detection device.

Generally, color television video signals transmit color information by amplitude and phase modulation of color subcarriers. In order to provide the reference phase of this color subcarrier, several cycles of the color subcarrier of the reference phase are cut out in a burst shape and transmitted in the back porch portion of each horizontal synchronization signal signal. This is called a color burst. Now, in the case of the NTSC system, the frequency of the reference subcarrier (hereinafter referred to as SC) specified by this color burst is selected to be 455/2 times the horizontal synchronization frequency. Since this multiple is an integer multiple of 2, the color burst waveform created by cutting SCf at a fixed relative position with respect to the horizontal synchronization signal has a phase difference with respect to the horizontal synchronization signal for every horizontal opening signal. Invert. Also, NTSC color television (one screen (one frame) of No. 24 is 525
The number of horizontal scanning lines of a book is odd, so the phase of the color burst shifts by 180° between the corresponding horizontal scanning lines of one frame and the next frame, and the polarity of the waveform changes. Invert. Therefore, when switching between two color television video signals from one to the other (for example, when editing a videotape)
Even if both video signals are perfectly synchronized to the frame, if this is done randomly, there is a 50% probability that the phase will be out of alignment with the repetition period of the color burst described above. . When this happens,
The polarity of the SC specified by the color burst will be reversed at the switching point and the continuity of the SC will be lost.
When a video signal that has lost its continuity is processed using a synchronous digital device, the synchronous digital device generally
Since Ci is extracted and horizontal synchronization and other time axis signals are created using this as a reference, a discontinuity equivalent to half a cycle of SC occurs in this time axis. Therefore, when observing this on a television monitor, when switching between similar screens, you will notice that the screen shakes horizontally at the time of switching. In order to completely eliminate this unnatural lateral wobbling, it is necessary to switch the video signals by considering not only the frame continuity but also the SC continuity. Therefore, a signal obtained by dividing the frame signal into 1/2 according to the phase of SC (this is called a full color frame)
It is necessary to detect this from the video signal and match the phases completely before switching. A color frame detection device performs this detection.

Conventionally, this color frame detection device uses the following method. In other words, the color TV Shiron video signal is passed through a low-frequency filter (a low-frequency filter that sufficiently passes the horizontal synchronization component and sufficiently attenuates the color signal component) on the one hand, and a high-frequency filter (horizontal filter) on the other. The signal is passed through a high-frequency p-wave filter that sufficiently attenuates the synchronization component and passes the color signal component. A horizontal synchronization signal and a normal frame pulse are extracted from the signal obtained by the former method by synchronization separation.

A color signal component including a color burst portion is extracted from the signal obtained in the latter step, and is further amplified at full saturation to be shaped into a pulse-like waveform (with a data rate of about 50%). On the other hand, by passing the horizontal synchronizing signal extracted as described above through a delay circuit with a certain delay time, its leading edge is delayed to the color burst position, and the waveform of this rising portion is used as described above. latches the pulsed waveform created from the color burst. Since the phase of this latched signal is shifted by 180 degrees every horizontal opening cycle as described above, the signal becomes a signal whose high and low levels are alternately inverted every horizontal opening cycle. If the signal obtained in this way is further latched again with the previous frame pulse extracted from the sync separation circuit (i.e., the color burst for the horizontal sync signal at a certain position at the beginning of each frame is It is latched at a certain relative position from the synchronization signal.However, the color burst has a rectangular wave shape due to saturation amplification), and the high and low regills are reversed every frame, making it a single color frame gold period. A color frame signal is obtained. The above is the color frame detection method used in the conventional apparatus.

However, the conventional method has the following drawbacks. First, the high-frequency SC waveform obtained through a high-frequency ν-wave device is latched using a pulse obtained through a separate low-frequency P-wave device, so changes in temperature and humidity The difference in absolute delay time between the two caused by this directly appears as a change in the phase of the latch point. In order to prevent this, it is necessary to use parts that are highly stable against changes in temperature and humidity, or to take special measures to compensate for all of these, which is expensive. Also, as mentioned above, since the horizontal synchronization signal is delayed and the color burst converted into a rectangular wave is simply latched, I wonder if the latching is actually performed near the center of the rectangular wave?
Or, it is not clear whether latching is performed at a point near the edge of the square wave. If it is performed near the edge, it will become unstable due to the jitter generated in the detection device and the jitter of the synchronization signal of the color television signal itself and the color burst phase, and the above-mentioned high and low fluctuations will occur every 6-1 horizontal opening period. It is possible that a pulse with an inverted level may be generated inadvertently, and therefore an incorrect color frame may be detected. Some devices have added a time 7 and a time w5 to display the latch phase of the color burst, but this is very troublesome as it has to be adjusted every time a different video signal arrives.

An object of the present invention is to provide a complete color frame detection device that does not use highly stable parts and does not require complicated adjustments.

The apparatus of the present invention includes means for extracting color burst flag pulses, frame pulses, and color bursts from a color television video signal, means for obtaining partial pressure values of positive and negative peak voltages of the color burst, and means for extracting color burst flag pulses, frame pulses, and color bursts from a color television video signal; means for obtaining first and second electrical signals by saturating and amplifying the color burst at a partial voltage value of a peak voltage of Latch with signal and 3rd
and means for obtaining an electrical signal M4, means for obtaining a fifth electrical signal by latching a fourth electrical signal with the third electrical signal, and latching the fifth electrical signal with the frame pulse to produce a color frame. and means for detecting.

Next, the present invention will be explained in detail with reference to all the drawings.

FIG. 1 is a block diagram for explaining one embodiment of the present invention, and FIG. 2 is a waveform diagram of the main part of FIG. 1. In the figure, a color television video signal 22 inputted from an input terminal 21 is supplied to a low-pass P-wave device 1 (cutoff frequency IMHz) and a band-pass P-wave device (center frequency 3.58 MHz) 2.
A luminance component-only signal and a chromaticity component-only signal are provided, respectively. Of these, the luminance component that has passed through the low-pass F wave generator 1 is supplied to the synchronization separation circuit 3. The signal passing through the synchronization separation circuit 3 is supplied to a pulse generation circuit 4, where a burst flag pulse 23 (a signal having a pulse width corresponding to the period in which a color burst exists) and a frame pulse 24 are generated.

When the chromaticity component that has passed through the bandpass p-wave device 2 is gated in the p-burst gate circuit 5 using the burst flag pulse 23, a color burst 25 is extracted. This color burst 25 is detected by the peak detection circuit 6 (color burst 4
The voltage value is passed through a circuit that detects the peak value every cycle and holds the voltage value for about 20 horizontal synchronization cycles. The resulting voltage is passed through the voltage dividing circuits 8 and 9 and divided by an appropriate partial pressure value (for example, TFL/2), and the positive value is 26.27 for each of the positive and negative values of the color burst 250 wave peak value.
(shown by a dashed line in FIG. 2) is obtained.

At these partial pressure values 26 and 27, the color burst 25 is saturated and amplified by the saturation amplifier (comparator) 10.11 to obtain a color burst pulse signal 28.29, which is used by the latch circuit 112. When the burst flag pulse 23 is latched in the latch circuit 1113, signals 30 and 31 are obtained which indicate the positions of the positive and negative leading edges of the color burst, respectively. (However, the latch circuits 112 and 113 are reset by the burst flag pulse 23 during periods other than color bursts.) A signal 30 indicating the positive and negative leading edges of this color burst
．． 31 with the other in the latch circuit [114, a signal 32 is obtained which, except during the color burst blanking period, inverts approximately every horizontal opening period corresponding to the information of the leading edge of the color burst. When this signal is latched by the frame pulse 24 in the latch circuit 15, a color frame pulse 33 is obtained.

The present invention uses a low-pass P-wave filter and a band-pass filter, but since the horizontal synchronization signal is not delayed and the color burst is latched, both P-wave filters may be inexpensive and simple. In addition, problems such as jitter do not become a problem unless there are particularly large fluctuations that change the etch of the color burst, and since no adjustment device is required, it is easier to handle than conventional color frame detection devices. Easy and cheap 0

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, 10 - Fig. 2 is a waveform diagram explaining the operation of the embodiment 0 In Figs. Vessel, 2...
...Bandpass Fv device, 3...Synchronization separation circuit, 4
... Pulse generation circuit, 5 ... Burst gate circuit, 6 ... Peak detection circuit, 7 ...
Inverting amplifier, 8, 9... Voltage divider circuit, 10.11
・・Saturation amplifier, 12...Latch circuit I, 13
...Latch circuit■, 14...Latch circuit■,
15... - Latch circuit ■, 21... Input terminal,
22...Color television video signal, 23...
Burst frachals, 24... Frame pulse, 25... Color burst, 26...... Partial pressure value of the positive peak value of the color burst, 27...... The negative peak value of the color burst. Partial pressure value of peak value, 28...
Color burst pulsed signal 1129... Color burst pulsed signal TI, 30... Indicating the positive front of the color burst, 31... Negative front of the color burst Signal indicating the edge, 32...
A signal that contrasts with the information on the leading edge of the color burst and is inverted every horizontal opening period, 33...Color frame pulse. Agent Patent Attorney Susumu Uchihara 11-

Claims (1)

[Claims] Means for extracting each of a burst flag pulse, a frame pulse, and a color burster from a color video signal; and a peak voltage detection means for detecting positive and negative peak voltages of the extracted color burst, dividing the voltage at a predetermined ratio, and outputting the divided voltages. , means for receiving the extracted color burst and the positive and negative outputs from the peak voltage detection means and converting the color burst into two first and second square waves; a first latch means for obtaining third and fourth signals by respectively latching the burst flag pulses using a rectangular wave; and a second latch means for latching the third signal at the timing of the fourth signal. 1. A color frame detection device, comprising a latch means, and detects a color frame based on the output of the second latch means.