JPH025691A - Picture transmission equipment - Google Patents

Abstract

PURPOSE:To efficiently perform the encoding processing to improve the motion following-up capacity by preliminarily limiting the number of data to be encoded in accordance with the number of communication destinations and performing the encoding processing of these data. CONSTITUTION:A circuit 11 to detect the number of stations to ground decides the number of stations to ground, which are connected at present, by information of hook to ground from transmission control parts 7. This circuit 11 supplies the indication of a sampling method, which is preliminarily determined in accordance with the number of stations to ground, to a picture and audio encoding circuit 6. Only required sampled data is subjected to the encoding processing in this circuit 6. Therefore, the encoding processing like inter-frame encoding is very efficiently performed, and the motion following-up capacity or the like is considerably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image transmission device used for a video conference in which multiple points participate, and particularly to improvement of transmission signal processing thereof.

[Background Art] In recent years, in order to make effective use of time, there has been increasing interest in video conferences held by a plurality of participants in remote locations. This video conference connects conference rooms located at different locations with communication lines, and uses various communication media.
It uses devices, etc., to exchange images and sounds, and hold conferences.

In such a video conference, three or more locations may participate. In such a case, it is necessary to display images of multiple points on the display that displays images of the other party.

Conventionally, when communicating between multiple points, the communication data sent and received between each point was not changed, and each image was combined by processing on the receiving side. That is, the received image data is thinned out and compressed at a predetermined ratio to obtain a reduced image, or only necessary portions of the received image data are cut out and combined.

Furthermore, in point-to-point communication, combining images from a plurality of points using a split screen method is disclosed in, for example, Japanese Patent Laid-Open No. 108688/1988.

[Problems to be Solved by the Invention] In such conventional point-to-point communication, images are compressed and combined or cut out and combined on the receiving side. Therefore, the image transmission apparatus at each point encodes the obtained image as it is and transmits it. Therefore, even data that is not actually needed is encoded and transmitted. For this reason, there have been problems such as a reduction in the amount of necessary image data to be transmitted and a deterioration in image motion followability.

Furthermore, as shown in Japanese Patent Application Laid-open No. 108688/1983, video signals at each point are captured as originally small images using a split screen method. However, this method requires equipment such as a special television camera, and also has the problem that it is not possible to transmit predetermined image data depending on the number of destinations, making the entire device complicated.

This invention was made with the aim of solving the above-mentioned problems, and it automatically limits the data to be encoded according to the number of transmission destinations, and reduces the number of pixels of the encoded image. An object of the present invention is to provide an image transmission device that can perform image transmission with good motion followability by reducing the amount of motion.

[Means for Solving the Problems] An image transmission device according to the present invention is used for a video conference in which multiple points participate, and an image signal obtained by a camera is converted into a digital signal in an A/D conversion section. , this digital signal is sampled at a predetermined number of pixels in the horizontal direction and number of lines in the vertical direction in the sub-sampling circuit, this sampled digital signal is encoded in the encoding processing section, and this encoded signal is The signal is transmitted from the image transmission unit to the plurality of parties, and the signals from the plurality of parties are received by the image transmission unit, and the number of parties currently transmitting and receiving is detected based on the signal from the image transmission unit, The present invention is characterized in that sampling in the sub-sampling circuit is controlled in accordance with the number of parties, and the amount of data to be encoded is changed in accordance with the number of parties to which images are transmitted and received.

[Operation] The image signal obtained by the camera is input to the A/D conversion section, where it is converted from an analog signal to a digital signal. Then, this digital signal is sampled by a predetermined number of horizontal pixels and a predetermined number of vertical lines in a sub-sampling circuit. The signal that has been thinned out in a predetermined manner in this way is input to the encoding processing section and is encoded there. This encoded signal is then transmitted from the transmission control unit to a plurality of parties.

On the other hand, signals from 1 (number of parties) are received by the transmission control unit.Then, the number of parties currently transmitting and receiving is detected based on the signal from this transmission control unit, and the number of parties is The sampling in the sample circuit, that is, the amount of data thinning is set to 121.

As described above, according to the present invention, sampling is controlled according to the number of communication partners, and therefore encoding processing is also controlled according to the number of communication partners. Therefore, the efficiency of encoding processing can be improved, and image data with good motion tracking performance can be transmitted and received.

[Embodiment] Next, an image transmission device according to an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the overall configuration of this embodiment.

(1) is a video phone device, (2) is a handset for voice communication, (3) is a TV camera, (4) is a display, and (5) is a video phone device for making calls from (1) and receiving calls from the other party. (6) is an image/audio encoding circuit that encodes the input image data and audio data; (7) is a telephone repeater that controls communications, etc., and (7) transmits the image data and audio data to the other party, and (8) is an image/audio decoding circuit that decodes a plurality of signals supplied from the transmission control unit; (9) is an image integration circuit that synthesizes image data; 10) is a speech synthesis circuit for synthesizing speech, and (11) is a ground station number detection circuit.

In such an image transmission device, a television camera (3)
The image obtained by the image/audio encoding circuit (6)
is input. The image/audio encoding circuit (6) first converts the input analog signal into a digital signal. The encoding process in the image/audio encoding circuit (6) includes both intraframe encoding and interframe encoding, and compresses the data to be transmitted by quantizing the image data. The image data encoded in this manner is then manually input to the transmission control section (7).

Here, local station hook information is supplied from the telephone repeater (5) to each of the plurality of transmission control units (7). Then, a signal is transmitted to a specific destination from the transmission control section (7) instructed by this own station hook information.

Note that the audio signal is inputted from the handset (2) to each transmission control section (7) via the image/audio encoding circuit (6), and is transmitted to the other party along with the image data according to the local station hook information.

Here, in this embodiment, the transmission control unit (7) issues ground hook information to notify that the line with the transmission device at another point, which is the communication partner, has entered the communication state, and this ground hook information is transmitted to the ground hook information. It is manually input to the station number detection circuit (11). The number of ground stations detecting circuit (11) then determines the number of currently connected ground stations based on the ground hook information from the transmission control section (7).

The number of ground stations detection circuit (11) supplies an instruction for a predetermined sampling method according to the number of ground stations to the image/audio encoding circuit (6).

Here, the image/audio encoding circuit (6
) is an analog-to-digital conversion circuit (1) as shown in Figure 2.
2) , sub-sampling circuit (13), encoding circuit (14)
), a variable length encoding circuit (15).

Then, the sampling in the sub-sampling circuit (13) is changed by the signal from the ground station number detection circuit (11). That is, the sub-sampling circuit (13) samples the digital signal supplied from the analog-to-digital conversion circuit (12) at a predetermined number of pixels in the horizontal direction and number of lines in the vertical direction. It is changed by a command from the ground station number detection circuit (11).

When the number of ground stations is one, normal sampling is performed so that normal image display can be performed as shown in FIG. 3A. When the number of points is 2, sampling is performed so that image data can be displayed on half of the screen as shown in FIG. 3B. In such sampling, where the number of pixels is reduced to 1/2, the number of pixels in the horizontal direction may be set to 1/2 of every other pixel, and the number of lines in the vertical direction may also be set to 1/2 of every other line, or the number of pixels in the horizontal direction may be set to 1/2 of every other line. The parts corresponding to both ends of the pixel image may be thinned out by 1/4, and only the image data in the central part may be sampled. Note that one type of sampling may be predetermined, or one may be selected.

The case where the number of ground points is 3 is shown in Figure 3C, and the case where the number of ground points is 4 is shown in Figure 3.

The image data that has undergone predetermined sampling by the sub-sampling circuit (13) in this way is sent to the encoding circuit (14).
However, depending on the sampling format in the sub-sampling circuit (13), the way in which one frame is taken for the encoding process changes. Therefore, the detection signal from the number of ground stations detection circuit is also input to this encoding circuit (14), and encoding processing such as intra-frame encoding and inter-frame encoding is performed accordingly.

The signal that has undergone such processing is then input to the variable length encoding circuit (15), where it is re-encoded and the transmitted data is compressed. Note that the audio data is converted into a digital signal by the analog-to-digital conversion circuit (16), and then
It is encoded in the audio encoding circuit (17) and supplied to the transmission control section (7).

On the other hand, the image data sent from the ground station is supplied to the image/audio decoding circuit (8) via the transmission control section (7), where it undergoes decoding processing.

This image/audio decoding circuit (8) includes a variable length decoding circuit (18) and a decoding circuit (19) as shown in FIG. The image data from the image/audio decoding circuit (8) is then manually input to the image integration circuit (9). This image integration circuit (9) includes multiple image/audio decoding circuits (8)
This is to integrate the digital signals of images supplied from the computer and synthesize them into one screen. Then, the digital-to-analog conversion circuit (12) converts this digital signal into an analog signal for display on the display (4). Therefore, the signal output from this digital-to-analog converter (20) is displayed on the display (4) of the videophone device (1).
In Figure 3A.

Displays such as B, C, and D are made according to the number of ground stations. Note that the audio signal in the received signal output from the transmission control unit (7) is supplied to the audio synthesis circuit (9) via the image/audio decoding circuit (8), where multiple voices are synthesized and sent to the video phone ( 1) is output from the handset.

As described above, according to the image transmission device of this embodiment, the number of destinations currently communicating is recognized based on the ground hook information supplied from the transmission control unit (7), and based on this, the sampling of image data for transmission is performed. change. Therefore, the encoding process in the image/audio encoding circuit (6) is performed only on the necessary sampled data. Therefore, encoding processing such as interframe encoding can be performed very efficiently, and it is possible to significantly improve motion tracking performance.

[Effects of the Invention] As described above, according to the image transmission device according to the present invention,
Since the number of data to be encoded is limited in advance according to the number of communication partners and the encoding process is performed on this data, the encoding process can be performed efficiently and motion tracking performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the image transmission device according to the present invention, FIG. 2 is a block diagram showing details of the image/audio encoding circuit (6) in the embodiment, and FIG. 3 is the same implementation. FIG. 3 is an explanatory diagram showing a mode of image display in an example. In the figure, (5) is a telephone repeater, (6) is an image/audio encoding circuit, (7) is a transmission control unit, (11) is a ground station number detection circuit, (13) is a sub-sampling circuit, (14) is an encoding circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] An image transmission device used for a video conference in which multiple points participate, comprising: an A/D converter that converts an image signal obtained by a television camera from analog to digital; and an image signal output from the A/D converter. a sub-sampling circuit that samples a digital signal with a predetermined number of horizontal pixels and a predetermined number of vertical lines; an encoding processing unit that performs encoding processing on the output from this sub-sampling circuit; and this encoding processing A transmission control unit that transmits signals from the image transmission unit to transmission destinations at multiple other locations and receives signals from multiple other locations, and the number of other locations that are currently transmitting and receiving signals from this image transmission unit. and a sampling control unit for controlling sampling in the sub-sampling circuit according to the number of other points, and changing the amount of data to be encoded according to the number of transmitting and receiving parties to which images are transmitted and received. An image transmission device characterized by: