JPS6145673Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a still image transmission device for transmitting television signals via a narrowband transmission path.

A conventional device of this type was constructed as shown in FIG. First, the encoder 11 is for converting the video signal input from the terminal 10 into a digital code, and the compressor 12 is for converting the video signal input from the terminal 10 into a digital code, and the compressor 12 is for converting the video signal inputted from the terminal 10 into a digital code, and the compressor 12 is for converting the video signal inputted from the terminal 10 into a digital code. This is a method for reducing the number of bits per pixel by utilizing the statistical properties of , and differential predictive coding is generally known. Memory 13, 23
is for storing compressed image information, and has a capacity for one frame or one field. The transmission controller 14 performs parallel-to-serial conversion and modulation so that it can be transmitted from the memory 13 via a transmission line. The transmission controller 22 demodulates image information received via the transmission line and performs serial-to-parallel conversion. and write it into the memory 23. The pixel information stored in the memory 23 is stored at the TV scan rate (60 fields/
After being read out in seconds) and converted into the original image information before being compressed by the decompressor 24, the decoder 25 converts it into the original analog signal and outputs the reproduced video signal to the television monitor connected to the terminal 26. .

As described above, in the conventional still image transmission device, the compressor 12 is located before the memory 13 and the decompressor 24 is located after the memory 23 as shown in FIG. ~16M
The drawback was that it had to operate at Hz, which required the use of expensive high-speed integrated circuits (such as ECL). In addition, when it is desired to perform image processing by connecting a computer or the like to the terminal 16, the image information obtained from the memory 13 is a code compressed by the compressor 12, so extraneous information is required to decode the code. This requires a program and the process is very complicated. Similarly, on the receiving side, terminal 21
Since the decompressor 24 is located after the memory 23, the decompressor 24 is located after the memory 23, so that image information that has been subjected to image processing by a computer is input to the memory 23 and the result is displayed on the television monitor connected to the terminal 26. A normal image cannot be obtained unless the same compression process as that performed by the device 12 is performed and input to the terminal 21, and the processing is complicated.

In order to solve these drawbacks, the present invention encodes the video signal at a high speed of 8MHz to 10.7MHz on the transmitting side, stores it in memory, and then reads it out at a low speed and compresses it. On the receiving side, the image information decompressed at low speed is stored in memory, and then read out from memory at high speed and decoded to reproduce the original video signal.

In this way, according to the present invention, the compressor and expander are
It is no longer necessary to operate at a high speed of 8MHz to 10.7MHz, and it is sufficient to operate at a low speed of about 3KHz, and inexpensive circuit elements such as TTL (transistor/transistor logic element) can be used.

Examples will be described below.

FIG. 2 is a block diagram showing the first embodiment of the present invention, in which 11 is an encoder, 13' and 23' are memories, 12' is a compressor, 14 and 22 are transmission controllers,
24' is an expander, 25 is a decoder, 10 is a video signal input terminal, 15 is a transmission code output terminal, 16' is an output terminal for image processing, 20 is a transmission code input terminal, 2
1' is an input terminal for image processing, and 26 is a reproduced video signal output terminal.

The video signal input from the terminal 10 is sent to the encoder 11.
The analog signal is linearly encoded into a digital signal with 8 bits per sample. The sampling frequency of linear encoding is 8MHz to 10.7MHz. The encoded image information is stored in the memory 13'.
The data is accumulated for one frame or one field. Thereafter, the accumulated image information is read out slowly at a speed that corresponds to the bandwidth of the transmission path. This speed varies depending on the bandwidth of the transmission path used, but for example, assuming transmission at 2400 bits/second using one telephone line, it will be 2400 Hz. The image information thus read out from the memory 13' at a low speed is compressed by the compressor 12' into a differential prediction code of 4 bits per pixel. The compressed image information is subjected to parallel-to-serial conversion by the transmission controller 14, modulated into a signal that can be passed through the transmission line, and outputted to the transmission line via the terminal 15. The above is the operation on the sending side.

Next, the operation on the receiving side will be explained.

Image information sent from the transmitting side via the transmission path is input to the transmission controller 22 through the terminal 20. After being demodulated here, it undergoes serial-parallel conversion and is added to the decompressor 24' as image information of 4 bits per pixel. The decompressor 24' performs the opposite operation to that of the transmitter compressor 12', thereby decompressing the signal into a digital signal of 8 bits per pixel before being compressed. The operating speed at this time is 2400 Hz, the same as the compressor 24'. The decompressed image information is slowly stored in the memory 23' at the same speed. The accumulated image information for one frame or one field, which is digitally encoded at 8 bits per pixel, is transferred from the memory 23' at a rate of 60 fields per second so that it can be displayed on a television monitor connected to the terminal 26. The decoder 25 reads out the signal and reproduces it into the original analog signal, which is then output to the television monitor through the terminal 26.

In this way, in the present invention, the compressor 12' and the expander 24' only need to operate at a low speed of about 2400 Hz, so they can be constructed with inexpensive circuit elements (such as TTL).
When image processing is performed by connecting a computer or the like to 6' and 21', the image information output from the memory 13' is an uncompressed 8-bit linear encoded signal per pixel, and Since the image information to be input to 23' only needs to be a similar signal, it is not necessary to perform expansion and compression processing each time in order to perform image processing, which also has the effect of making it very simple.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional still image transmission device, and FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, 11...encoder, 12, 1
2'... Compressor, 13, 13', 23, 23'...
Memory, 14, 22...Transmission controller, 24, 2
4'...decompressor, 25...decoder.

Claims (1)

[Scope of utility model registration request] In a system that performs band conversion using a memory and transmits a television signal via a narrowband transmission line, an encoding means for encoding the video signal and a system that stores image information from the encoding means in the memory at high speed and transmits it at a low speed. a first reading means for reading the image information from the memory, a compression means for compressing the image information read from the memory by predictive encoding, a transmission means for transmitting the image information from the compression means to a transmission path, and a first reading means for reading the image information from the transmission path. a receiving means for receiving the transmitted image information; a decompressing means for decompressing the compressed image information received by the receiving means; and a second part for accumulating the image information decompressed by the decompressing means at a low speed and reading it at a high speed. 1. A still image transmission device comprising: reading means; and decoding means for decoding the image information read out at high speed by the second reading means.