JPH0494283A - Picture memory device - Google Patents

Abstract

PURPOSE:To eliminate the need for an A/D converter and a D/A converter by quantizing a video signal in frequency-modulated state in 1-bit and recording the result. CONSTITUTION:A bias voltage is given to a frequency-modulated video signal (a) by a capacitor 1 and resistors 2,3 and the result is digitized by an inverter 4. In the case of decoding the digitized signal, a data string in 1-bit read from a frame memory is outputted via an inverter 6. In this case, a high frequency component added in the digital processing is eliminated by a low pass filter 7 to obtain an output waveform (d) similar to an original waveform (a), and since frequency information of an FM wave is preserved in the signal (d), the FM wave is returned to a modulation demodulation circuit from which the FM wave is obtained to apply FM demodulation, then the stored video signal is obtained, Thus, exclusive components for A/D conversion and D/A conversion are not required.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an image memory device used for storing, processing, and delaying video signals, in which FM modulation used for recording and transmitting video signals is applied. The video signal of the state is 1
By quantizing and recording data using BLT), the structure eliminates the need for analog/digital and digital/analog converters, which are normally required by image memory devices.

2. Description of the Related Art In order to record a video signal, which is an analog signal, as a digital signal, a conventional image memory device uses an analog/digital converter to digitize the video signal and then write it into a memory. Furthermore, when outputting a video signal, a numerical value is read from the memory, and a digital/analog converter is used to convert the video signal back to the original analog signal.

An example of a conventional circuit will be described below.

FIG. 3 is a block diagram of a conventional image memory device.
9 is a clamp circuit, which is used to clamp the input video signal to an appropriate DC voltage during analog/digital conversion, and 9 is an analog/digital converter, which converts the analog signal into digital data. Convert to This data is written to ten frame memories. 10 frame memories store data for one frame of video,
Data can be read at any time. 11 is digital/
This is an analog converter, and the data read from memory is returned to an analog signal, but the high frequency components added by sampling are removed by 12 LPFs (low pass filters). , the configuration is such that a signal similar to the original signal is output.

Problems to be Solved by the Invention In order to digitize and record a video signal, a sampling rate on a fixed plate and a number of quantization bits are required. Usually, the sampling rate is 10 to 141 sPs and the number of quantization bits is 6 to 6. Digitize with 8 bits. This digitization requires a high-speed, high-precision analog/digital converter, and when converting the signal back to analog, a digital/analog converter with the same speed and precision is required, which adds to the high cost. It takes. In order to make image memory devices cheaper, analog/digital and digital/analog conversion is required.
It is necessary to configure it so that it can be done at low cost.

Means for Solving the Problems In order to achieve this object, the image memory device of the present invention has the following features:
1 bit of video signal in FM modulated state? By quantizing and recording, image memory devices usually require analog/digital.

It is characterized by eliminating the need for a digital/analog converter.

In order to provide resistance to distortion and attenuation, active video signals are normally subjected to FM modulation during recording or transmission, and since devices such as video tape recorders are equipped with an FM modulation/demodulation mechanism, There is no direct cost increase due to transmitting and receiving video signals between the image memory device and the outside in an FM modulated state.

FM modulation is a conversion that replaces a signal with a frequency,
Since the amplitude has no information, in order to sample the FM signal, it is sufficient to input the FM signal with a constant DC bias into the inverter and obtain 1-bit serial data. To restore the signal, the data can be output from the inverter and passed through a high-pass filter.

In this way, analog/digital and digital/analog conversion can be easily realized by processing the video signal in an FM modulated state.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of main circuits in an embodiment of the present invention.

In Figure 1, capacitor 1 makes the DC potential of the FM signal independent of the input, and resistors 2 and 3 are
It gives a DC potential of 2.6v to the FM signal, and
The inverter determines whether the input potential is above or below the threshold value of 2.6V and outputs the result as binary data, and the memory 5 stores the binarized data in a predetermined manner. The data is sampled sequentially according to the clock cycle and stored for one frame. The inverter 6 receives the data read from the memory and outputs it to the analog circuit, and the filter 7 removes harmonic components caused by binarization. .

FIG. 1 shows the image memory device configured as described above.
Its operation will be explained using FIG. The waveform in FIG. 2a is an FM-modulated video signal extracted from the modulation/demodulation circuit section of video equipment to which the image memory device of the present invention is connected; in this state, video information is converted into a frequency. There is. A bias voltage of 2.6V is applied to this FM wave by the capacitor and resistor shown in Figure 1, 1.2.3, and the first
The waveform digitized by the inverter 1 in FIG.
As shown in FIG. 2, frequency information is stored in the frame memory of FIG. 1 as the interval between HI and LO inversions. To restore the digitized signal, output the 1-bit data string that has been read out from the frame memory through the inverter shown in Figure 1, 6, and it will look like Figure 2 C. By removing the added high frequency components with the low-pass filter shown in Fig. 1,
An output waveform d similar to the original waveform a in FIG. 2 is obtained.

Since the frequency information of the original FM wave is stored in the signal d, the stored video signal can be obtained by returning the FM wave to the modulation/demodulation circuit from which it was extracted and performing FM demodulation.

In this way, by processing the video signal in an FM modulated state, it is possible to realize the functions of an image memory device without using dedicated elements for analog/digital conversion and analog/digital/analog conversion. can.

Effects of the Invention As is clear from the above description, according to the image memory device of the present invention, the image memory device can be configured for analog/digital conversion and digital/analog conversion without using dedicated elements. things are possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts in an embodiment of the image memory device of the present invention, FIG. 2 is a characteristic diagram showing examples of signal waveforms in each part of FIG. 1, and FIG. 3 is a conventional image memory device. FIG. 2 is a block diagram showing the main parts of. 1... Capacitor, 2... Resistor, 3...
・Resistor, 4... Inverter, 6... Frame memory, 6--... Inverter, 7 ・Low-pass filter, 8... Bias circuit, 9... Analog/digital conversion device, 1o...frame memory,
11.Digital/anahuac converter, 12.Low pass filter Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
Figure 1 Figure 3

Claims (1)

[Claims] An image memory characterized by converting an FM-modulated video signal into a 1-bit quantized signal indicating whether the signal is greater than a predetermined value and storing the signal in a semiconductor memory device. Device.