JPS59178886A - Coding system - Google Patents

Abstract

PURPOSE:To prevent picture quality of a received reproducing picture from being deteriorated by inputting an input digital picture signal to a coding circuit via a low pass filter in performing sub-sampling or a sub-line coding in the coding system performing high compression coding to reduce a reflecting component. CONSTITUTION:When the sub-sample coding or the sub-line coding is performed in the coding circuit 2, an output of the low pass filter 10 is selected by a selector 11 and inputted to the coding circuit 2, and when the sub-sample coding or the sub-line coding is not attained, the digital picture signal applied to the input terminal 1 by the selector 11 is inputted directly to the coding circuit 2. The digital picture signal narrowered for the band via the low pass filter 10 is inputted to the coding circuit 2, then the reflecting component produced by the difference value between frames is reduced after the elapse of time decided by the response of the coding circuit 2 thereby reducing the reflecting component due to the sub-sample coding or the sub-line coding. The distortion is reduced by the elimination of the reflecting component.

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention is directed to a high-efficiency coding and transmission device for image signals in which image quality does not deteriorate when sub-sampling or supline coding is performed to achieve high compression. This relates to an encoding method that encodes data as follows.

Prior Art and Problems In high-compression coding of image signals, a high-efficiency coding and transmission device that performs composite differential predictive coding and the like is used. 1st
The figure is a block diagram of the main parts of a conventional high-efficiency coding transmission device.
Yes, 1 is the input terminal for the digitized image signal, 2
3 is an encoding circuit, 3 is a frame memory, 4 is a pre-prediction circuit, 5 is a quantization circuit, 6 is a code conversion circuit for converting into a transmission path code such as a variable length code, 7 is a buffer memory, and 8 is a sending circuit. be. The image signal is converted into, for example, an 8-pin digital image signal and applied to the input terminal 1.

In the case of a color image signal, for example, a luminance signal and a chromaticity signal are separated, time-division multiplexed, and applied to the input terminal 1. The digital image signal applied from the input terminal 1 to the encoding circuit 2 is differenced from the output of the frame memory 3 to obtain an inter-frame difference value, and is applied to the pre-prediction circuit 4. The pre-prediction circuit 4 has a configuration that further calculates a difference with respect to the inter-frame difference value, and may perform, for example, sub-sample encoding in which every other pixel is encoded, or sub-line encoding in which encoding is performed every other scanning line, for example. It is something that can be done. The buffer memory 7 determines whether to perform subsample encoding or supline encoding.
It is controlled by control signal a from . The output of this pre-prediction circuit 4 is applied to a quantization circuit 5, where it is quantized by a predetermined quantization step, and is applied to a code conversion circuit 6.

The code conversion circuit 6 performs coding such as block coding and variable length coding to obtain a transmission path code, adds the transmission path code to a buffer memory 7, and sequentially reads out the transmission path code from the buffer memory 7 in accordance with the transmission speed. The transmitted transmission path code is sent out from the sending circuit 8 to the transmission path.

The buffer memory 7 has a function of detecting the amount of stored information, and when it reaches a predetermined amount of stored information before overflowing, that is, the amount of information read out corresponding to the transmission speed is input from the code conversion circuit 6. When the input information amount reaches a predetermined M product information amount before the input information amount exceeds the storage capacity due to the large amount of input information, a control signal a is applied to the code conversion circuit 6 and the encoding circuit 2, and the input information is sent to the buffer memory 7. In order to reduce the input information amount of This control is used to change the coding step or to shorten the code length in variable length coding in the code conversion circuit 6.

When high compression encoding is performed by the control signal a mentioned above,
This information is sent to the receiving side, and if subsample encoding or supline encoding is performed on the transmitting side,
Based on this information, the receiving side performs one-sum coding using subsample decoding or subline decoding, and converts the decoded digital image signal into an analog image signal and displays it on a cathode ray tube display device, etc. It is something to do.

As mentioned above, if high compression is achieved by performing composite difference using subsample encoding or supline encoding, aliasing components will occur as a frequency characteristic of the transmitted signal, and the image quality of the received and reproduced image will deteriorate. It will deteriorate.

OBJECTS OF THE INVENTION It is an object of the present invention to reduce aliasing components when sub-sampling or supline encoding is performed, thereby preventing deterioration in the image quality of received and reproduced images. Examples will be described in detail below.

Embodiment of the Invention FIG. 2 is a block diagram of an embodiment of the invention.
The same reference numerals as in the figure indicate the same -gl (minute), 9 is a filter circuit, 10 is a low-pass filter, and 11 is a selector. Selector II directly inputs the digital image signal applied to input terminal I to encoding circuit 2 The selector 11 is controlled by the control signal a when the &[ information amount of the buffer anomaly 7 exceeds a predetermined value, and the low-pass The output of the filter IO is selected and input to the encoding circuit 2.In the encoding circuit 2, when 9-buckample encoding or subline encoding is performed,
When the output of the low-pass filter IO is selected by the selector 11 and inputted to the encoding circuit 2, and subsample encoding or supline encoding is not performed, the selector 11
The digital image signal applied to the input terminal 1 is directly input to the encoding circuit 2.

When the movement of images is rapid, the amount of information added to the buffer memory 7 increases due to the difference between frames, and in this case, as described above, the amount of information added to the buffer memory 7 through the low-pass filter 10 is reduced. After the lapse of time, it is possible to reduce the aliasing components that occur with respect to the interframe difference value, and to reduce the aliasing components caused by subsample encoding or supline encoding. In this case, the image signal will have a narrow band, which will cause blurring in the received and reproduced image, but distortion will be reduced by removing the aliasing component. Furthermore, when the image changes from a rapidly moving image to a dull image, the image quickly returns to its normal state, so that the overall image quality can be improved.

FIG. 3 is a block diagram of an example of the low-pass filter 10, in which 21 to 23 are delay circuits having a delay time of z-1 corresponding to one sampling time, 24 is a summation circuit, and 25 is a division circuit to 1/2. The circuit 11 is the aforementioned selector. The division circuit 25 has a simple structure that shifts the output of the summation circuit 24 by one bit, and the delay circuit 23 is for ensuring that all outputs selected by the selector 11 have the same delay time. Note that it is also possible to employ low-pass filters with other configurations.

FIG. 4 is a block diagram of main parts of another embodiment of the present invention,
The same reference numerals as in FIGS. 1 and 2 indicate the same parts, 12 is a low-pass filter, and 3 is a selector. As described above, the selector 11 of the filter circuit 9 selects the output of the low-pass filter 10 and adds it to the encoding circuit 2, as described above, by the control signal a generated when the M product information amount of the buffer memory 7 reaches a predetermined value. In the encoding circuit 2, the selector 13 selects the output of the low-pass filter 12 and sends it to the pre-prediction circuit 4.
In addition, the pre-prediction circuit 4 will perform sub-sample encoding or supline encoding, and its encoded output will be added to the quantization circuit 5, and the quantized output will be added to the next code conversion circuit 6. Become.

By inserting the low-pass filter 10 of the filter circuit 9 and the low-pass filter 12 in the encoding circuit 2 according to the control signal a from the buffer memory 7, a smooth transition to subsample encoding or supline encoding is achieved. be able to. That is, the band for the inter-frame difference value can be narrowed by the low-pass filter 12 at the same time as transitioning to subsample encoding or supline encoding, and aliasing components generated due to high compression can be suppressed at the same time as switching the encoding means. It can be carried out.

On the receiving side, by receiving control information indicating that the code is a highly compressed code that has undergone subsample encoding or supline encoding, the filter corresponding to the low-pass filter 12 is converted into an interframe difference decoding circuit. This is to perform decoding compatible with high compression encoding on the transmitting side, thereby improving the quality of received and reproduced images.

As described in detail, the present invention involves inputting an input digital image signal to the encoding circuit 2 through the low-pass filter 10 when performing high-compression encoding using sub-sampling or supline encoding. , it is possible to suppress the aliasing components due to high compression encoding, and the received and reproduced image will be distorted due to band limitation, but since the distortion caused by the aliasing components can be removed, it is possible to shift to high compression encoding. It is possible to prevent deterioration of image quality in the case of

Furthermore, since the image quality is rapidly changed when the image changes statically, the overall image quality can be improved.Also, the frame difference value of the encoding circuit 2 can be improved. When the low-pass filter 12 is inserted during compression encoding, the transition to high compression encoding is performed smoothly.
Furthermore, deterioration of image quality can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional encoding system, Fig. 2 is a block diagram of main parts of an embodiment of the present invention, Fig. 3 is a block diagram of an example of a low-pass filter, and Fig. 4 is a block diagram of another embodiment of the present invention. FIG. 2 is a block diagram of main parts of an embodiment. 1 is an input terminal for a digital image signal, 2 is an encoding circuit,
3 is a frame memory, 4 is a pre-prediction circuit, 5 is a quantization circuit, 6 is a code conversion circuit, 7 is a ) \ rough memory, 8 is a sending circuit, 9 is a filter circuit, 10 is a low-pass filter,
, 11 is a selector, 12 is a low-pass filter, and 13 is a selector. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Gobe Tamamushi and 3 others Procedural Amendment September 19, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1 Indication of Case Patent Application No. 54271, 1988 2
Title of the invention Encoding method 3 Relationship with the case of the person making the amendment 1 patent person Address 1015 Kamiodanaka, Nakahara-ku, Yozaki City, Kanagawa Prefecture Name (522) Fujitsu Limited Representative Takashi Yamamoto 4 Agent residence Address: 20-7 Toranomon-chome, Minato-ku, Tokyo (1) Page 7, lines 4 to 7 of the specification [This is for a simple structure... j [has a simple configuration. ] Corrected as follows. (2) Page 9, line 8 of the same book: “Because it can be removed,”
Correct it as [because it can be removed]. (3) Figure 3 of the drawing shall be corrected as shown in the attached Figure 3.

Claims (1)

[Claims] An input digital image signal is compressed and encoded by an encoding circuit, and the encoding circuit performs high compression encoding using sub-sampling or supline encoding according to a control signal outputted in accordance with the amount of information stored in the buffer memory. An encoding method characterized in that the input digital image signal is input to the encoding circuit through a low-pass filter when performing the sub-sample or supine encoding.