JPS5841713B2 - Color television signal synchronous coupling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for synchronously combining color television signals.

In order to mix (mix and wipe) multiple color television signals, superimpose (superimpose), or switch them without disrupting synchronization, it is necessary to synchronously combine the respective color television signals.

Conventionally, for this type of synchronous coupling, a method is known in which each signal generation source is synchronized in frequency with a master synchronization signal, and phase synchronization is achieved by adjusting the delay difference between the signals. The disadvantage is that the sources are limited.

Removing this limitation on signal sources,
Frame synchronizers are known, but in conventional frame synchronizers, the sampling frequency is limited to an integral multiple of the subcarrier frequency, which imposes unnecessary restrictions on the device.

It is an object of the present invention to provide a synchronous coupling device with few limitations on signal sources and sampling frequencies.

That is, the present invention includes means for sampling and encoding a composite color television signal, means for generating local subcarriers as a digital code string from sampling pulses, and means for performing product detection of a burst signal using the local subcarriers. , a means for automatically controlling the relative phase of the burst signal and the sampling pulse by changing the relative phase of the burst signal and the sampling pulse using the detection output so that the phase of the burst signal and the local subcarrier are in a predetermined relationship. A color television signal comprising means for synchronously sampling each signal and temporarily storing them in a buffer memory, and means for reading out the stored sample values so that the phases of the respective burst signals and the synchronization signal match. This is a synchronous coupling device.

According to the present invention, by synchronous sampling, sample values that are phase-synchronized with the burst signal of each color television signal can be obtained, and since local subcarriers are generated internally, these sample values can be easily numbered. Since it can be attached, a stable synchronous coupling device can be realized without any adjustment.

Further, as will be described later, the sampling frequency may be (m/n) times the subcarrier frequency, so there is no practical limitation on the sampling frequency.

The present invention will be described below with reference to the drawings, taking an NTSC signal as an example, but the present invention can also be applied to other television signals such as PAL and SECAM.

FIG. 1 is a block diagram showing the configuration of a synchronous sampling device used in the present invention, and FIG. 2 is a block diagram showing the synchronous coupling device of the present invention.

First, the synchronous sampling device shown in FIG. 1 will be explained.

The NTSC signal 1 is sampled and encoded by an A/D converter 2.

The A/D converter output is guided to a band pass filter (BPF) 3, where components near the subcarrier frequency are extracted, and a detector 4 performs product detection using the local subcarrier generated by a local subcarrier generator 5. be done.

The sampling frequency f8 of the A/D converter is the subcarrier side frequency f
SCpm, n (m>n) is selected as an integer.

Since the frequency fH is 4 times fsc, the relationship in (1) is determined by 2/55 of the horizontal synchronization of the NTSC signal, giving a wide degree of freedom in selecting the sampling frequency within a practically possible range. It will be done.

In the figure, 6 is a synchronization separation circuit, and 7 is a voltage controlled oscillator, which is used to generate a frequency-related sampling pulse as shown in equation (2) based on the horizontal synchronization signal that is synchronized and separated from the NTSC signal 1. It is a circuit.

Further, 8 is a variable phase shifter for changing the phase of the sampling pulse.

The local subcarrier generator 5 consists of an address generator 12 and a read-only memory IJ (ROM) 13.

Continuous local subcarrier becomes.

Therefore, if m sine function values from k=o to =m-1 are stored in the ROM 13, and the storage address of the ROM is periodically scanned and these values are read out, the local subcarrier can be determined. can get.

If the burst signal is a continuous system, the multiplicative detection output by the local subcarrier is eO8θ
Since it is proportional to , in order to make the phase difference θ zero, it is sufficient to maximize the detection output.

In order to realize such control, the detection output is first extracted only during the burst period by the gate 9, integrated by the integrator 10, and the result is led to the judgment circuit 11 to judge the magnitude and direction of the phase shift. , the determination result may be fed back to the variable phase shifter 8 and the address generator 12, and automatic control may be performed so that the deviation becomes zero.

In the figure, when a large phase shift of one cycle or more of the sampling pulse is detected, rough phase control is performed by controlling the address generator 12 and shifting the address by one address, and a small phase shift is detected. In this case, the variable phase shifter 8 performs minute phase control.

In this way, the synchronous sampling device performs synchronous sampling on the NT
A local subcarrier 104 whose phase is synchronized with the SC signal 101 and the burst signal, and an address 102 for generating the local subcarrier are generated.

FIG. 2 is a block diagram showing the synchronous coupling device of the present invention, in which different NTSC signals are input to 1a and 1b, and the synchronous sampling device 100a described above, respectively.

The data is synchronously sampled at 100b.

There are various possible cases in which the signals input to 1a and 1b may be from multiple color cameras, one may be a studio camera and the other is a relay signal from a distant place, or other cases. The phase or exact frequency of each burst signal, and in some cases, the vertical and horizontal synchronizing signal phases do not necessarily match.

NTSC with such burst and synchronization phase mismatch
The synchronous coupling device of the present invention divides the signal phase into two numbers.

When synchronous sampling is performed by the synchronous sampling devices 100a and 100b, the respective sampling pulse phases and local subcarrier phases are generally different, but the relative phases of the local subcarrier and the burst signal are the same.

Therefore, the synchronously sampled PCM code 101a is numbered by the address 102a for local subcarrier generation, and the PCM code 101b is numbered by the address 102b.

The PCM code 101a is written in the buffer memory 50a in correspondence with the address 102a, and the PCM code 101
b corresponds to address 102b and buffer memory 5
0b, and if the contents of the same address are simultaneously read by the read address generator 510 command, the buffer memory output 52a.

52b, a PCM code with two matching burst signal phases is obtained.

If the relative phase difference or delay difference of the input signals is smaller than the period m of the address for local subcarrier generation, synchronous coupling is possible by the above address specification, but the relative phase difference of the input signals is larger than the period m. In this case, the address for local subcarrier generation alone is insufficient, so in addition to this, the number from the beginning of the horizontal synchronization signal may be used as the address.

It is clear that when the relative phase difference of the input signals is even larger, the burst signal phase and the synchronization signal phase can be made to match if the scanning line number is also used for addressing.

In FIG. 2, the synchronously coupled NT SC signal 52a
t52b is switched, superimposed, or mixed by the multiplexer 25, and then the D/A
The converter 33 converts it into an analog signal.

Although the above explanation is based on the case where there are two input signals, the case where there are three or more input signals can be realized with the same configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a synchronous sampling device used in the present invention, in which 2 is an A/D converter, 3 is a bandpass filter, 4 is a detector, 5 is a local subcarrier generator, and 6 is a synchronization Separation circuit, 7 is a voltage controlled oscillator, 8 is a variable phase shifter, 9 is a gate, 10 is an integrator, 11 is a determination circuit, 12 is an address generator, and 13 is a read-only memory. FIG. 2 is a block diagram showing the synchronous coupling device of the present invention.
00a and 1oob are synchronous sampling devices, 50at50b is a buffer memory, 51 is an address generator, 25 is a multiplexing device, and 33 is a D/A converter.

Claims (1)

[Claims] 1. means for sampling and encoding a composite color television signal, means for generating a local subcarrier from a sampling pulse as a digital code string, means for multiply detecting a burst signal using the local subcarrier, and the detection output. A plurality of color television signals are each synchronized by a synchronization sampling device comprising means for automatically controlling the relative phase of the burst signal and the sampling payas so that the phase of the burst signal and the local subcarrier have a predetermined relationship. A synchronous coupling device for color television signals, comprising means for sampling and temporarily storing it in a buffer memory, and means for reading out the stored sampled values so that the phases of the respective burst signals and synchronization signals match. .