JPS63142786A - Picture signal encoding device - Google Patents

Abstract

PURPOSE:To clearly transmit a fine picture by switching automatically encoding of an encoding device to the encoding mode with high space resolution and of a high amplitude resolution, when a camera is switched to the camera to photograph a picture, and a writing such as a graph or a drawing, for instance. CONSTITUTION:An encoding mode switching means 21 is automatically switched to the predetermined most suitable combination of three parameters; time resolution, amplitude resolution and space resolution, being connected with the switching operation of a picture output from the cameras 1A, 1B. When the camera is switched to the camera 1B for the picture and the writing to photograph the graph or the writing, the encode mode switching means 21 switches automatically the encode mode of an encode circuit 20 to the encode mode of the high space resolution and the high amplitude resolution, and the output signal of the camera 1B for the picture and writing, is encoded by the said encoding mode with high space resolution and the high amplitude resolution, further, is outputted as the code of a constant bit rate. Thus, the reproduced picture of the outputted encode output of the still picture of the graph and the drawing comes to be a clear and fine picture.

Description

[Detailed Description of the Invention] [Summary] In an encoding device such as a video conference system that switches and inputs the output of a plurality of cameras and encodes it into a low bit rate transmission signal and transmits it, the camera outputs, for example, a graph or a drawing. When switching to a camera that captures calligraphy and drawings, the encoding device automatically switches to an encoding mode with high spatial resolution and amplitude resolution, making it possible to transmit fine images clearly.

[Industrial application field]

The present invention relates to an encoding device for an image signal encoding and transmission system used in a video conference system or the like in which image signals from two or more cameras are switched while being switched, and particularly to a low bit rate encoding device.

In an image signal encoding device, encoding is performed by controlling three parameters of the image signal: amplitude resolution, spatial resolution, and temporal resolution, so as to keep the transmission bit rate within a certain level.

However, these three encoding parameters have a mutually contradictory relationship, and if one is improved, the other two will naturally become worse.

Therefore, as a low bit rate encoding device for an image signal, it is necessary to effectively control these three encoding parameters and perform efficient encoding depending on the nature of the subject of the camera.

[Conventional technology]

As shown in the block diagram of FIG. 4, the encoding control of image signals in a conventional low bit rate encoding device is such that all the image signals output from the cameras 1^ and 1B are divided into two types, for example, ■time resolution, ■amplitude resolution. , ■ Encoding is performed by determining the encoding parameters based on the priority order of spatial resolution.

That is, it is encoded in the following order: (1) smoothness of image movement, (2) neatness of image, and (0) fineness of image, and the weighting of these parameters is determined by the camera IA.

The determination was made by the encoding circuit 20 in the encoding device, regardless of IB switching.

[Problem that the invention seeks to solve]

As mentioned above, the encoding operation of the conventional low bit rate encoding device for image signals is based on the priorities of ■temporal resolution, ■amplitude resolution, and ■spatial resolution for all image signals output from cameras 1A and 1B. Since the parameters are determined and encoded in the above-described manner, the image signal output from the camera IB when the subject is a stationary document or image such as a graph or drawing is also encoded in the above priority order.

Therefore, the encoding operation of the output of the document and image camera IB does not necessarily result in a control mode with high spatial resolution and high amplitude resolution required for still image signals.

In general, still images such as calligraphy and drawings do not require temporal resolution, but spatial resolution and amplitude resolution that define the transmission of thin and clear images are important.

Therefore, there is a problem in that the encoding method of the conventional image signal encoding apparatus does not satisfy this point.

[Means for solving problems]

The above problem is solved by switching and inputting the image signal output from two or more cameras LA and IB, as shown in Figure 1.
Automatically switches to one of the predetermined combinations of the three encoding parameters of the temporal resolution, amplitude resolution, and spatial resolution in conjunction with the switching operation of the image signal output of the temporal resolution, amplitude resolution, and spatial resolution. Encoding mode switching means 21
This problem is solved by the configuration of the present invention that adds the following.

[Effect]

The encoding mode switching means 21 of the present invention is a camera IA.

In conjunction with the switching operation of the image output from the IB, the camera automatically switches to the predetermined optimal combination of the three parameters of temporal resolution, amplitude resolution, and spatial resolution, so that the camera can be used as a normal portrait camera IA. At this time, the encoding mode switching means 21 selects the combination of the three parameters of temporal resolution, amplitude resolution, and spatial resolution in this order, but when the camera switches to the document camera IB for copying graphs and drawings, the encoding The encoding mode switching means 21 automatically switches the encoding circuit 2
0 is automatically switched to a coding mode with high spatial resolution and amplitude resolution, and the output signal of document camera IB is encoded in the coding mode with high spatial resolution and high amplitude resolution, and , is output as a code with a constant bit rate.

Therefore, the reproduced image of the encoded output of the output still image of the graph or drawing becomes a beautiful and thin image, and an effective encoded transmission system can be realized.

〔Example〕

FIG. 2 is a block diagram showing the configuration of an image signal encoding device according to an embodiment of the present invention.

The image signal outputs from the two cameras, the portrait camera IA and the document camera IB, are switched by the automatic switch 5W-2 according to the settings of the manual switch S-1, and are input to the encoding device 2.

For example, when the manual switch 5W-1 is turned to the contact H side of the camera for large objects, the automatic switch 5W-2 selects the output of the portrait camera IA, and the manual switch SW-1 selects the contact of the document camera. When the camera is tilted to the opposite side, the output of the document camera IB is selected by the automatic switch hand 2 and is input to the encoding circuit 20 of the encoding device 2.

The camera output image signal input to the encoding circuit 20 is
The character encoding mode 21A and the calligraphy encoding mode 21B are selected and encoded by the changeover switch 21 of the encoding mode switching means 21 of the encoding device 2, and output as an encoded signal at a constant bit rate. be done.

As an example of the encoding circuit 20, a detailed block using encoding of inter-frame difference values is shown in FIG.

The difference value between the image signal being input as the camera output and the image signal of one frame before stored in the field memories 204A and 204B is input to the quantizer (Q) 201 and quantized. The conversion data can be changed using the switch (
SWI) 205 and is input to, for example, an entropy encoder 202 that performs variable length encoding. The encoded output of the entropy encoder 202 is stored in the buffer memory 2
03, and after being buffered at a constant bit rate, it is output to the transmission path and transmitted to the receiving side. When the buffer memory 203 overflows beyond a certain bit rate, a switch (SWI) 205 cuts off input of quantized data from the quantizer (Q') 201 to the entropy encoder 202.

The amplitude resolution of this encoding circuit is controlled by the quantizer 201
This can be done by changing the number of quantization steps and step size. If a coarse quantization step is used, the amount of transmitted information will be reduced, the amplitude resolution will be reduced, and the image quality will deteriorate.

One of the ways to control the spatial resolution is to control the resolution in the horizontal direction, for example, by performing so-called subsampling in which the quantization value of pixels that are not encoded is set to zero in the quantizer 201 so that they are not transmitted, thereby reducing the amount of information to be transmitted. Transmit images with degraded horizontal resolution. During this subsampling,
On the receiving side, the pixel portions that were not sent are interpolated using an interpolation filter.

Another vertical resolution control of the spatial resolution of encoding is
For example, only the odd fields of the input image are encoded and the even fields are not encoded. This reduces the amount of transmitted information to 1/2.

The even field data that is not sent is replaced with the data of the previous odd field memory 204B and transmitted, for example, by switching the contact from a to b under the control of the switch 206 (SW2). At this time, the encoding circuit will transmit an image with degraded vertical resolution.

Therefore, if the quantization step of the quantizer 201 is made finer and both odd and even fields are encoded without subsampling, the quality of the transmitted image will improve, but the amount of transmitted information will increase, and the number of bits will remain constant at a low level. In bit rate transmission, the number of images that can be transmitted per second decreases, the temporal resolution deteriorates, and in the case of moving images, flickering increases.

Conversely, the quantization step of the quantizer 201 is coarsened, and
By subsampling and encoding only one field, either odd or odd, the amount of information to be transmitted will be reduced, the number of screens that can be transmitted per second will be increased, the temporal resolution will be improved, and moving images can be transmitted with less flickering. , the image quality of each image will be poor.

The encoding mode switching means 21 between the encoding mode for people and the encoding mode for documents and drawings shown in FIG. .206 contact points are selected so that the temporal resolution, amplitude resolution, and spatial resolution are each optimized.

When the output signal of the person camera IA is selected, the quantization step of the quantizer 201 of the encoding circuit 20 shown in FIG. Perform coarse encoding of only
Although amplitude resolution and spatial resolution are degraded, encoding is performed with good temporal resolution.

Furthermore, when the output signal of the document camera IB is selected, the quantization step of the quantizer 201 of the encoding circuit 20 becomes finer, and the switch 206 selects the contact point a to encode both odd and even fields to achieve amplitude resolution. , the spatial resolution increases. As a result, the buffer memory 203 often overflows,
The time resolution of the switch 205 becomes smaller as it changes from contact point a to contact point a.

That is, the encoding device 2 of this embodiment improves the temporal resolution in the case of a portrait camera notification, and automatically and reliably improves the amplitude resolution and spatial resolution when switched to the document camera 1B. The encoding of the image will be effectively performed within a constant bit rate.

〔Effect of the invention〕

As explained above, according to the present invention, the optimal combination of the three encoding parameters of temporal resolution, amplitude resolution, and spatial resolution is automatically selected and encoded depending on the characteristics of the subject of the camera. An effect can be obtained in which the image output of the camera can be effectively encoded within a constant bit rate range.

[Brief explanation of the drawing]

FIG. 1 is a principle block diagram showing the configuration of an image signal encoding device according to the present invention. FIG. 2 is a block diagram showing the configuration of an image signal encoding device according to an embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of an image signal encoding device according to an embodiment of the present invention. FIG. 4 is a block diagram of a conventional image signal encoding device. 1 and 2, 1 is a camera, IA is a person camera, 1B is a document camera, 2 is an encoding device, 20 is an encoding circuit, and 21 is an encoding mode switching means. , Ho 5 To H 珂 O 凰 I Gin Rakugo Go 0 spear Tehikihi 4 辷y crossbars,
ε also 10,000 yori ``o shift 4 pine 1 song button 7 shouting broom 2 N no I Mera IB Sekiho' 4-times

Claims (1)

[Claims] An encoding circuit that switches and inputs image signal outputs from two or more cameras (1A, 1B), controls temporal resolution, amplitude resolution, and spatial resolution and encodes at a constant transmission bit rate. To (20), an encoding mode switching means (21) for selecting a different combination of the temporal resolution, amplitude resolution, and spatial resolution is added, and encoding is performed in conjunction with switching of the image signal output of the cameras (1A, 1B). 1. An image signal encoding device characterized by operating an encoding mode switching means (21).