JPH11239331A - Multi-point communications system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display an image sent from pluralities of terminals that make simultaneous communication of the same screen with an inexpensive and simple display method. SOLUTION: In this multi-point communications system where 4 terminals make simultaneous communication, a QCIF image sent from an opposite party is decoded up to a stage of inverse quantization, the decoded image is quantized by a new quantization width and coded and sent as a CIF again. A screen of one terminal is divided into four and on which each image is displayed, then pluralities of images are viewed at the same time by a system less expensive than a conventional system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system in which communication is performed between a plurality of communication terminals using image data, and more particularly, to one terminal screen when a video conference at another point is performed between three or more communication terminals. And a multipoint communication system capable of simultaneously displaying image data from a plurality of communication terminals.

[0002]

2. Description of the Related Art In a conventional multipoint communication system,
There is an application filed by the present applicant in Japanese Patent Application No. 8-135736. According to this application, among a plurality of communication terminals performing simultaneous communication, at least one terminal has a channel control function, that is, a function like an MCU,
The display screen of the communication terminal can be divided into four, and images relating to up to four of the communication terminals among the plurality of communication terminals simultaneously communicating can be simultaneously displayed on one terminal screen.

[0003]

In such a conventional multipoint communication system, image data from a plurality of communication terminals simultaneously communicating on one terminal screen is simultaneously used without using an expensive MCU. It is described that it can be displayed. Unfortunately, Japanese Patent Application No. 8-135736 does not disclose how to display image data from a plurality of communication terminals simultaneously communicating on one terminal screen. Therefore, the applicant of the present invention makes further studies based on this Japanese Patent Application No. 8-135736, and a terminal for synthesizing a screen provides a system which is less expensive than the conventional one by synthesizing the screen with a simple configuration.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and one display screen is divided among a plurality of communication terminals and four of the plurality of communication terminals which are simultaneously communicating.
In a multipoint communication system capable of displaying image data from up to two communication terminals, the communication terminal encodes the image data and transfers the encoded data to a partner terminal, while the partner terminal received from the communication terminal transmits the encoded data. Is stored in a buffer and the encoded data is further entropy-decoded and then inversely quantized, quantized with a new quantization width in accordance with the accumulation amount of the buffer, and further entropy-encoded after encoding this quantized data. To provide a multipoint communication system for transmitting to other terminals.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a multipoint communication system of the present invention, FIG. 2 is a diagram illustrating an image transmission format used in the multipoint communication system of the present invention, and FIG. FIG. 4 is a diagram illustrating a format of an image used, FIG. 4 is a diagram illustrating a display example in a multipoint communication system of the present invention, and FIG. 5 is a diagram illustrating display timing of an image in a multipoint communication system of the present invention. FIG. 6 is an example, and FIG. 6 is a block diagram of a terminal used in the multipoint communication system of the present invention, and FIG. 7 is a diagram illustrating quantization width determination means of the multipoint communication system of the present invention.

In FIG. 1, a terminal T0 is simultaneously communicating with three terminals T1 to T3 via a network 1. In the figure, 2 _{1 to} 2 _n are line interfaces (hereinafter line I /
F), 3 _{1 to} 3 _n are demultiplexed, 4 is a PSC detector, 5 _{1 to} 5
_n is a buffer, 6 is a control unit, 7 is a switch, 8 is an entropy decoding unit, 9 is an inverse quantizer, 10 is a quantizer, 11 is a quantization width determination unit, 12 is an entropy encoding unit, 13 Is a two-dimensional inverse discrete cosine transform (inverse DCT) unit, 14 is a two-dimensional discrete cosine transform (DCT) unit, 15 is a screen reconstruction unit, 16 is a block division unit, 17 is an image display monitor, 18 is a television camera, 19 Is a multiplex synthesis circuit.

The operation will be described with reference to FIGS. First, an image transmitted from the terminals T1 to T3 to the terminal T0 will be described. In the communication system of the present invention, ITU-T H.26
1 Image transmission is performed according to the recommendation, resulting in the configuration shown in FIG. In FIG. 2, 20 is a PSC (Picture Start Code), and 21 is
TR (Temporal Reference), 22 is PTYPE (Type informatio
n), 23 is PEI (Extra insertion information), 24 is PSP
ARE (Spare information), 25 is GOB (Group Of Block) l
ayer.

The configuration of the GOB layer will be described with reference to FIG. 26 is GBSC (Group of Blocks Start Code)
, 27 is GN (Group Number), 28 is GQUANT (Quantizer inf
ormation), 29 is GEI (Extra insertion information), 3
0 is GSPARE (Spare information), 31 is Macroblock laye
r.

[0009] Here, in the format called CIF recommended by H.261, one image is divided into 12 GOBs as shown in FIG. 3, and in QCIF which is half the resolution both vertically and horizontally, it is divided into three GOBs. Therefore, GOB layer for each image
Contains 12 and 3 GOBs, respectively.

In the multipoint communication system according to the present invention, a terminal
The images transmitted from T1 to T3 are encoded and transmitted by QCIF having three GOBs. Next, the operation on the receiving side of T0 will be described. In FIG. 1, the data transmitted is the line I / O of T0.
Via the F 2 ₁ to 2 ₃ is stored in the buffer 3 ₁ to 3 _3. At this time, the PSC in the data is detected by the PSC detection unit 4,
A break position for each screen in the data stream is specified. The control unit 6 on each screen unit a switch 7 based on the information from the PSC detector 4 Te switched from the buffer 5 ₁ to 5 _4, performs control retrieval of data.

Next, the image data output from the switch 7 is subjected to entropy decoding in an entropy decoding unit 8 and inversely quantized in an inverse quantizer 9. The result is inversely transformed by a two-dimensional inverse discrete cosine transform unit 13, reconstructed into an original screen by a screen reconstruction unit 15, and displayed on an image display monitor 17.

The image decoded here is QCIF. If the image has the same resolution as CIF, the image can be handled as an image having half the vertical and horizontal sizes, so that at the time of display, the screen is divided into four parts. One part can display images from one point. Figure 5 about the display method at this time
This will be described with reference to FIG.

In FIG. 5, T1 indicates image data transmitted from the partner terminal T1. Similarly, T2 is the partner terminal
Indicates the image data transmitted from T2, T3 is the partner terminal
This shows the image data transmitted from T3. Although each data is stored in the buffer 5 ₁ to 5 _3, PSC is detected by the PSC detector 4 at this time.

As a result, as shown in FIG. 5, the data is A1, A2, A3,... For terminal T1, and B is for terminal T2.
1, B2, B3, ..., for terminal T3, C1, C2, C3, ...
, The separation position for each image is recognized.

Next, based on this information, the control unit 6 controls the switching unit 7 to switch data every time a screen break position is found. These data are decoded as described above, and are sequentially displayed as a half-sized image. At this time, if the display position is controlled such as An in the upper left of the screen, Bn in the upper right of the screen, Cn in the lower left of the screen as shown in the lower diagram of Fig. 5, unless the image at each position is overwritten with a new image,
If the same image is displayed, and if the image from the television camera 18 is further inserted at the lower right of the screen, the screen is divided into four as shown in FIG. 4 and the images of the terminals T0 to T3 are displayed.

On the other hand, the output from the inverse quantizer 9 is also input to the quantizer 10. The image input from the television camera 18 is also divided into blocks by the block dividing unit 16, converted by the two-dimensional discrete cosine transform unit 14, and also input to the quantizer 10. The data input to the quantizer 10 is quantized here and then entropy-encoded by the entropy encoder 12.

The coded data is stored in the buffer 54. At this time, the quantization width when quantized by the quantizer 10 is determined by the quantization width determining means 11 according to the storage amount of the buffer. You. The quantization width determining means determines the quantization width by a method according to the graph of FIG. 7, for example. That is, when the buffer storage amount increases, the quantization width is increased so as not to overflow the buffer, and conversely, when the buffer storage amount decreases, the quantization width is reduced so that underflow does not occur. To increase the code amount output from.

Thus, the amount of image data transmitted from the line I / Fs 21 to 23 can be reduced, and image data can be transmitted at the same transmission rate as the reception rate. That is, the line
If image data is transmitted at a transmission rate of P (bps) from each of the I / Fs 21 to 23, a total transmission rate of 3 × P (bps) is required, and it is possible to transmit to the terminals T1 to T3 as it is. Although it disappears, it is possible to reduce the entire code amount by requantizing with a new quantization width after inverse quantization at terminal T0, and it is possible to transmit at P (bps) including the image of own terminal T0 Become.

In the entropy encoder 12, FIG.
When configuring the image transmission format of (a), it is encoded as a CIF image. In other words, 3 originally included in the QCIF image
One GOB for each terminal T0 to T3
, 10, 12 positions, 1, 3, 5 positions, 2, 4, 6 positions, 7, 9, 11 positions. As a result, the data received by the terminals T1 to T3 are also displayed as a 4-split screen, like the data displayed by the terminal T0 shown in FIG.

[0020]

As described above, according to the present invention, in a multipoint communication system in which simultaneous communication is performed between four terminals, a QCIF image transmitted from a partner is decoded to the inverse quantization stage, and a new quantization is performed. By quantizing with a width and encoding and transmitting again as CIF, one terminal screen can be divided into four parts and images can be displayed, so that a plurality of images can be viewed simultaneously with a system less expensive than before.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multipoint communication system according to the present invention.

FIG. 2 is a diagram illustrating an image transmission format used in the multipoint communication system of the present invention.

FIG. 3 is a diagram illustrating an image format used in the multipoint communication system of the present invention.

FIG. 4 is a diagram illustrating a display example in the multipoint communication system of the present invention.

FIG. 5 is a diagram illustrating display timing of image data in the multipoint communication system of the present invention.

FIG. 6 is a diagram illustrating an image format transmitted and received in the multipoint communication system of the present invention.

FIG. 7 is a diagram illustrating a quantization width determination unit of the multipoint communication system according to the present invention.

[Explanation of symbols]

 1 ISDN network 2 Line interface 3 Demultiplexer 4 PSC detector 5 Buffer 6 Controller 7 Switch 8 Entropy decoder 9 Dequantizer 10 Quantizer 11 Quantization width determination means 12 Entropy encoder 13 2D Discrete cosine transform unit 14 Two-dimensional inverse discrete cosine transform unit 15 Screen reconstruction unit 16 Block division unit 17 Image display monitor 18 TV camera 19 Multiplexing circuit

Claims (1)

[Claims] 1. A multipoint communication system in which one display screen is divided among a plurality of communication terminals so that image data from four or less of the plurality of communication terminals simultaneously communicating can be displayed. The communication terminal encodes the image data and transfers the encoded data to a counterpart terminal, while the counterpart terminal received from the communication terminal stores the encoded data in a buffer and further dequantizes the encoded data after entropy decoding the encoded data. A multipoint communication system, wherein quantization is performed with a new quantization width in accordance with the accumulation amount of the buffer, the quantized data is encoded, entropy encoded, and transmitted to another terminal.