JPS63105588A - Encoding and decoding device for television signal - Google Patents

Abstract

PURPOSE:To miniaturize a device by realizing two codec functions with one TV codec, by transmitting all picture planes when a quasi-still picture is transmitted, and transmitting a part of the picture plane when a quasi-moving image is transmitted. CONSTITUTION:When a quasi-still picture selection signal is supplied to an external terminal 35, the control of a control circuit 32 is stopped, and the picture elements of all of the picture planes are transmitted to a decoder. Almost the same operation is performed at the decoder, and a control circuit 37 controls switches 38 and 39 according to the number of the picture element displayed by an address generation circuit 36, and receives only a desired picture element, and restores it to an original signal. And an identification signal of a quasi-still picture/quasi-moving image mode is transmitted from a Coder, and is decoded at a decoding circuit 22. The control circuit 37 of a Decoder is operated or stopped based on the above result. Thus, only by adding a means to prohibit the transmission of the signal based on several switches and the position of the picture element in the picture plane, it is possible to transmit the quasi-moving image and the quasi-still picture by one TV codec.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-efficiency encoding device for transmitting television signals over a low-speed digital transmission line.

[Conventional technology]

As is well known, the television signal is 4M T-1z 8
It has a wide band of degrees. For example, 64 kb/
Research is underway to transmit data using digital transmission lines with speeds as low as 500 ms. In this case, since the transmission speed is low compared to the television signal band, it is difficult to faithfully transmit the original television signal, so it is difficult to (1) reduce the number of frames transmitted while maintaining high spatial resolution; , or (2) reduce the spatial resolution to maintain the number of frames. The former is selected when transmitting a still image such as a calligraphy image, and the latter is selected when transmitting a moving image such as a human figure. Here, the high-efficiency encoding devices corresponding to these are respectively referred to as a quasi-still picture television picture codec and a quasi-moving picture television codec.

Now, these television codecs may be used alone, but for example, as described in the 1981 Denshitsu (i! Society National Conference 1419), semi-still image television codecs and semi-video television codecs are used. Prepare a codec and transmit both signals.

They are often displayed in combination.

[Problem that the invention seeks to solve]

In the above case, two television codecs and their combination circuits are required, resulting in an increase in the scale of the entire device.

An object of the present invention is to realize these two codec functions with one television codec, thereby eliminating the need for the above-mentioned combining circuit and significantly reducing the size of the device.

[Means for solving problems]

The above purpose is when transmitting semi-still images (semi-still image mode)
This is achieved by transmitting the entire screen when transmitting, and transmitting only a part of the screen when transmitting semi-video (S video mode).

[Effect]

In the quasi-still image mode, since the entire screen is transmitted, the number of pixels in one screen is large, and an image with high spatial resolution can be transmitted.

In addition, in the quasi-video mode, the number of pixels in one screen is reduced, so the time to transmit one screen is shortened, and movement can be faithfully transmitted. Generally, it is known that when the number of pixels is halved, the number of frames that can be transmitted per second increases by about 2 to 4 times.

As described above, a desired image can be transmitted in both the semi-still image mode and the semi-moving image mode.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is an overall block configuration diagram for digitally transmitting television (hereinafter abbreviated as TV) signals.
Camera 1. Coder 2. Transmission line 3. Codec 4. It consists of an image receptor 5.

In the figure, only the range surrounded by dotted lines and the switches are related to the present invention, and the rest are well-known parts.

A signal read from the TV camera 1 is converted into a digital signal by an analog/digital converter 11, and subtracted by a subtraction circuit 13 from a prediction signal generated by a prediction circuit 12. The subtraction result is quantized by the quantization circuit 14 and added to the above-mentioned prediction signal by the addition circuit 15. The addition result is
The prediction circuit 12 is delayed by the necessary time by the frame memory 16 that can store one screen or more signals.
is input to generate the next prediction signal.

At the same time, the above quantized signal is converted into a code word by the encoding circuit 17, smoothed through the buffer memory 18, and sent to the transmission line 3 at a constant speed.

In the decoder 4, the signal input from the transmission path is restored to the original quantized signal through the buffer memory 21 and the code word decoding circuit 22, and is added to the predicted signal generated by the prediction circuit 23 having the same function as the prediction circuit 12 described above. They are added by circuit 24. The addition result is delayed through the frame memory 25 and input to the prediction circuit 23 to generate the next prediction signal.

At the same time, the above addition result is restored to the original analog signal by the digital/analog converter 26 and displayed on the receiver 5.

Next, main parts of the present invention will be explained in detail.

The address generation circuit 31 of the coder 2 displays the number of pixels currently being predictively encoded starting from the top left of the screen. The control circuit 32 issues a control signal only when the number is within a predetermined range and switches the switch 33.3.
4 to permit writing to the frame memory 16 and buffer memory 18. As a result, the signal of this pixel is transmitted to the decoder. If it is outside the above range, switch 3
3.34 and prohibits transmission.

When the quasi-stationary side selection signal is applied to the external terminal 35, the above control of the control circuit 32 is stopped, and the pixels of the entire screen are transmitted to the decoder.

The operation of the decoder is almost the same, and the control circuit 37 controls the switches 38 and 39 according to the pixel number displayed by the address generation circuit 36 to receive only desired pixels and restore the original signal.

The identification signal of the quasi-still plane/quasi-moving image mode is transmitted from the Coder and decoded by the decoding circuit 22. As a result, D
The ecoder control circuit 37 is activated or deactivated.

Note that the following modifications are also included in the present invention.

(1) For TV signals, in addition to direct predictive coding of analog/digital converted signals as in this embodiment, orthogonal transformation,
Luminance/color signal separation conversion or the like may be performed.

(2) When transmitting the entire screen, all or part of the vertical synchronization signal and horizontal synchronization signal may be removed.

(3) Instead of using an external terminal to switch between quasi-video/quasi-still mode, count the characteristics of the signal, such as the difference between frames,
The result can also be used for switching.

(4) When switching the above modes, the prediction method, quantization method, and encoding method may also be switched.

(5) The area for partial transmission may be anywhere within the screen,
Further, the position may be controlled from the outside. Furthermore, the transmission area may be selected depending on the characteristics of the signal (for example, the difference between frames).

〔Effect of the invention〕

According to the present invention, semi-moving images and semi-still images can be transmitted by one TV cocoon by simply adding a means for prohibiting the transmission of the signal depending on some switches and the position of pixels within the screen. can. Therefore, the scale of the apparatus can be significantly reduced compared to the conventional apparatus which required two TV cookers, one for moving images and one for quasi-still images.

[Brief explanation of the drawing]

FIG. 1 is an overall block diagram of one embodiment of the present invention for digitally transmitting a TV signal. 1...T
V camera, 2... Korg, 3... Transmission line, 4...
Decoder, 5... Receiver, 11... Analog/digital converter, 12.23... Prediction circuit, 13...
Subtraction circuit, 14... Quantization circuit, 15.24... Addition circuit, 16.25... Frame memory, 17. Re-encoding circuit, 18.21... Buffer memory, 22...
・Decoding circuit, 26... digital/analog converter,
31.36... Address generation circuit, 32.37...
Control circuit, 33, 34, 38. 39... switch. 35...External terminal.

Claims (1)

[Claims] 1. A memory for storing image signals of at least one screen, a prediction circuit for predicting the next input signal using the output of the memory, a means for counting and displaying predicted pixels in the screen, and an output of the above means is determined in advance. 1. An encoding/decoding device for a television signal, comprising means for transmitting or receiving only within a certain range.