JPH01132286A - Picture communication equipment - Google Patents

Abstract

PURPOSE:To transmit much picture information through a simple circuit by providing an encoded signal with high efficiency by a sampling clock phase- synchronizing with a video signal, and outputs the encoded signal to a transmission line by the speed of a transmission line clock, and synchronizing the phase of the sampling clock with that of the transmission line clock. CONSTITUTION:The transmission line clock (a) is inputted to a first frequency divider 31, and is 779-th frequency divided, and is outputted to a phase comparator 32 as the clock signal of 6.176/779MHz. On the other hand, the clock signal outputted from a voltage controlled oscillator 34 is inputted to a second frequency divider 35, and is 1806-th frequency divided, and is outputted to the phase comparator 32. The phases of two clock signals are compared by the phase comparator 32, and a phase difference is outputted to a low pass filter 33, and after a high frequency component is removed, it is supplied to the voltage controlled oscillator 34, and its oscillation frequency is controlled so as io come to (6.176/779)X1806MHz, and is outputted to the second frequency divider 35 and a black burst signal generator 36. A black burst signal (b) synchronizing with the transmission line clock (a) is generated and outputted by the black burst signal generator 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image communication device having an encoding section that encodes a video signal with high efficiency.

High-efficiency coding is also called band compression coding, and is typically predictive coding.

[Conventional technology]

Conventionally, this type of image communication device has an encoding unit that encodes a video signal with high efficiency and sends data to a transmission path at a transmission rate required by the transmission path. The video signal is output by an input device K (for example a video camera or a frame synchronizer). Since the output signal of this input device is output regardless of the transmission line clock from the transmission line, the transmission line clock from the transmission line and the output of the input device are generally not synchronized. In the encoding section, encoding is performed using a sampling clock that is synchronized with the output of the input device in order to improve the image quality.

The sampling clock was asynchronous with the transmission line clock from the transmission line.

[Problem that the invention seeks to solve]

As described above, in the conventional method, the transmission line clock and the sampling clock from the transmission line are asynchronous. For this reason 1
In the image communication device, the encoding section serving as a transmitting section has a function of sending frequency information of a sampling clock for digitizing a video signal to a decoding section serving as a receiving section, and the decoding section serving as the receiving section. The part must have a function for regenerating the sampling clock based on the frequency information received from the transmission line. Therefore, one circuit configuration becomes complicated.

An object of the present invention is to provide an image communication device with a simple circuit configuration.

[Means for solving problems]

According to the present invention, there is provided a black burst signal generation circuit that generates a black burst signal phase-synchronized with a transmission line clock from a transmission line, and a means for outputting a video signal on which a video signal is superimposed in synchronization with the black burst signal. and high-efficiency encoding using a sampling clock phase-synchronized with the video signal.

an encoding unit that outputs an encoded signal to the transmission line at a speed of the transmission line clock, and the sampling clock is phase-synchronized with the transmission line clock. can get.

〔Example〕

Next, two aspects of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. A transmission line clock a from an input terminal 1 is input to an encoding section 2 and a black burst signal generation circuit 3. The black burst signal generation circuit 3 outputs a black burst signal BL synchronized with the transmission line clock a to the television camera 4, and the television camera 4 encodes the video signal C on which a video signal is superimposed in synchronization with the input black burst signal. conversion part 2
Output to. The encoding unit 2 performs high-efficiency encoding on the video signal cf, and sends it to the output terminal 5 at the speed of the transmission line clock a.

FIG. 2 shows a transmission path clock, a black burst signal, and a video signal, respectively.

FIG. 3 shows the configuration of the encoding section 2. The video signal is input to a C-fit converter 21 and a sync separator 22.

The synchronization separator 22 separates the synchronization signal d from the video signal C and outputs it to the sampling clock generator 23.

The sampling clock generator 23 generates a sampling clock e (basic frequency is 14.31
8 MHz) and outputs it to the converter 21. The converter 21 samples the video signal C using the sampling clock e, converts it into a digital signal, and outputs it to the encoder 24. The encoder 24 performs high-efficiency encoding, temporarily stores it in the buffer memory 25, reads it out from the sofa memory 25 at the speed of the transmission line clock a, and sends it to the output terminal 5.

The configuration of the black burst signal generation circuit 3 will be explained in FIG. In this embodiment, the transmission line clock aO value 'fr: 6
．． The test was carried out at a speed of 176 M) Iz.

The transmission line clock a is input to the first frequency divider 31.

The frequency is divided by 779 and output to the phase comparator 32 as a 6.176/779 MHz black signal. on the other hand.

The clock signal (same frequency as the sampling clock e in FIG. 3) output from the voltage controlled oscillator 34 is sent to the second branch 35.
The frequency is divided by 1806 and output to the phase comparator 32. The phase comparator 32 compares the phases of the two clock signals, outputs the phase difference to the low-pass filter 33, removes the high frequency component, and then applies it to the voltage-controlled oscillator 34 so that the oscillation frequency is (6,176/779 )X1806■h, and is output to the second frequency divider 35 and black burst signal generator 36. A black burst signal generator 36 generates and outputs a black burst signal bl synchronized with the transmission line clock a.

In a decoding section (not shown) serving as a receiving section, a 6.176 MHz clock signal extracted from the transmission path is input to a circuit having the same configuration as the black burst signal generation circuit 3 shown in FIG. A sampling clock synchronized with the transmission line clock is generated using the strike signal.

9 According to this embodiment, the black burst signal generation circuit 3
Although the sampling clock frequency generated by this method has a frequency error of 0.56 ppm with respect to the fundamental frequency, this is not a problem considering the frequency tolerance range of each constituent device.

In addition, in this embodiment, the sampling clock e synchronized with the video signal is generated by a voltage controlled oscillator (
This occurs when a VCO) is installed.

By incorporating the black burst signal generation circuit 3 into the sampling clock generator 23, the voltage controlled oscillator can be omitted.
Moreover, the pull-in time by the voltage controlled oscillator can also be reduced to zero.

〔Effect of the invention〕

As explained above, the present invention is necessary for the encoding unit as a transmitting unit because encoding is performed using a sampling clock synchronized with the transmission line clock from the transmission line. The function of sending the frequency information of the sampling clock to the decoding section serving as a receiving section and the decoding section serving as the receiving section were necessary. Since the function of regenerating the sampling clock based on the frequency information received from the transmission path is no longer necessary, the scale of the hardware circuit is reduced. Furthermore, image data can be allocated to the time slots allocated for transmitting frequency information of the sampling clock, which has the effect of transmitting a large amount of information for one image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image communication device according to an embodiment of the present invention, FIG. 2 is a diagram showing waveforms of various parts of the image communication device of FIG. 1, and FIGS. 3 and 4 are diagrams of the image communication device of FIG. 2 is a block diagram of the configuration of an encoding section 2 and a black burst signal generation circuit 3. FIG. 1 is an input terminal, 2 is an encoding section, 3 is a black burst signal generation circuit, 4 is a television camera, 5 is an output terminal, 21 is a fitted converter, and 22 is a sync separator. 23 is a sampling clock generator, and 24 is an encoder. 25 is a clock buffer memory, and 31 is a first frequency divider. 32 is a phase comparator, 33 is a low-pass filter, 34 is a voltage controlled oscillator, 35 is a second frequency divider, 36 is a black burst signal generator, and a is a transmission line clock. b is a black burst signal, and C is a video and video signal. d is a synchronization signal, and e is a sampling clock. Figure 1 Figure 3

Claims (1)

[Claims] 1. A black burst signal generation circuit that generates a black burst signal synchronized with a transmission line clock from a transmission line, means for outputting a video signal on which a video signal is superimposed in synchronization with the black burst signal, and the video signal an encoding unit that performs high-efficiency encoding using a sampling clock synchronized with the transmission line clock and outputs the encoded signal to the transmission line at a speed of the transmission line clock, the sampling clock being synchronized with the transmission line clock. An image communication device characterized by: