JP3655363B2 - Information communication system and center station - Google Patents

Description

とすることで、ＦをＲＥＣに近似させることができる。
【００５８】
このような考え方で、図４に示したビットストリーム変換部４１の形態と、図５に示した画像合成部５２の形態とを合わせて新たなセンター局を実現した場合、ビットストリーム変換器４１と画像合成部５２の間に可変長復号器（ＶＬＤ）と可変長符号化器（ＶＬＣ）とが重複することになる。
【００５９】
そこで、ビットストリーム変換部４１と画像合成部５２とからＶＬＤとＶＬＣとを一つづつ省略した形で新たなセンター局６０を構成することができる。
【００６０】
図９に示すように、このセンター局６０は、可変長復号器６０１、６０２、６０３、６０４と、符号化方式変換部６１１、６１２、６１３、６１４と、配置変換部６０５と、可変長符号化器（ＶＬＣ）６０６とから構成される。
【００６１】
この場合、センター局６０に入力された各Ｈ．２６１ビットストリームは、それぞれのＨ．２６１の可変長復号器６０１、６０２、６０３、６０４で可変長復号され、ビットストリームの持つ情報が抽出される。抽出された情報は、各符号化方式変換部６１１、６１２、６１３、６１４でＭＰＥＧ２情報に変換され、さらに配置変換部６０５で新しく配置される位置に合わせて位置情報の変換および並べかえなどが行われる。この情報はＭＰＥＧ２の可変長符号化器（ＶＬＣ）６０６で可変長符号化され、ＭＰＥＧ２ビットストリームが出力される。
【００６２】
この実施形態のＴＶ会議システムによれば、ビットストリーム変換部１１と画像合成部１２とからＶＬＤとＶＬＣとを一つづつ省略した形でセンター局１０を構成し、上記同様の符号化方式の変換処理を行うことができる。
【００６３】
なお、本発明は上述した実施形態のみに限定されるものではない。
【００６４】
上述した実施形態では、上り回線にＨ．２６１、下り回線にＭＰＥＧ２の各方式を適用したが、これ以外に最適な符号化方式があれば、それを適用してもよい。
【００６５】
また上述した実施形態では、上り回線の符号化方式はすべて同一としていたが、上り回線の符号化方式は複数あっても構わない。この場合、センター局には、各上り回線毎に適応した復号器または可変長復号器を用意すればよい。
【００６６】
さらに上述した実施形態では、下り回線の各端末にすべて同一のビットストリームを出力しているが、各端末毎に異なるビットストリームを出力してもよい。この場合、出力するビットストリームの数だけ画面配置変換のための出力機能部を用意し、可変長符号化すればよい。これにより、端末毎に異なる映像を受信することができる。また可変長符号化器の前段に符号化方式変換器を挿入することで、端末毎に異なる符号化方式のビットストリームを伝送することもできる。
【００６７】
【発明の効果】
以上説明したように本発明によれば、センター局では、上り回線および下り回線それぞれに効率のよい最適な符号化方式で情報の変換が行われるので、各端末局間の通信を効率よく行うことができる。
【００６８】
またセンター局では、複数の画像情報を一画面に合成して下り回線に一斉に伝送するので、上り回線側と情報の到着時間差が少なくなるので、各端末局間でＴＶ会議などを行う上では、画像の動きに遅延がなくなり、より自然な形で会話することができる。
【図面の簡単な説明】
【図１】本発明に係る一つの実施の形態であるＴＶ会議システムの構成を示すブロック図である。
【図２】図１のＴＶ会議システムのビットストリーム変換部を示すブロック図である。
【図３】図１のＴＶ会議システムの画像合成部を示すブロック図である。
【図４】図２のビットストリーム変換部の他の実施の形態を示すブロック図である。
【図５】図３の画像合成部の他の実施の形態を示すブロック図である。
【図６】Ｈ．２６１におけるループ内フィルタの係数を示す図である。
【図７】（ａ）〜（ｄ）は、ＭＰＥＧ２方式の半画素予測による動きベクトルの値を示す図である。
【図８】Ｈ．２６１方式におけるループ内フィルタに近似させたＭＰＥＧ２方式の半画素予測による係数を示す図である。
【図９】図４に示したビットストリーム変換部の形態と、図５に示した画像合成部の形態とを合わせて新たなセンター局を実現した場合の図である。
【図１０】従来の２地点間のＴＶ会議システムの構成を示すブロック図である。
【図１１】従来の３地点間のＴＶ会議システムの構成を示すブロック図である。
【符号の説明】
１…通信回線、１０、６０…センター局、１１、４１…ビットストリーム変換部、１２、５２…画像合成部、１０１、１０２、１０３、１０４…端末、１１１、１２１、１３１、１４１… H.261符号化器、１２１、１２２、１２３、１２４… MPEG2復号器、１３１、１３２、１３３、１３４…カメラ、１４１、１４２、１４３、１４４…モニタ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information communication system and a center station used when, for example, a plurality of terminal stations are provided at different points to perform a TV conference or the like.
[0002]
[Prior art]
In recent years, with the advancement of communication technology, a remote conference system (hereinafter referred to as a TV conference system) capable of performing a conference while being at a distant place has been spreading.
[0003]
In such a TV conference system, for example, when moving image communication is performed between two points, as shown in FIG. 10, a terminal 701 at a certain point and a terminal 702 at another point far from the point 701 are uplinked. The video communication between the two points is performed by so-called symmetric communication control in which the same encoding method is used for transmission at the same transmission speed. It is common.
[0004]
In this case, both the communication from the terminal 701 to the terminal 702 and the communication from the terminal 702 to the terminal 701 use the same encoding method A and the same transmission rate (B bps).
[0005]
As shown in FIG. 11, when a multipoint conference is performed by connecting three or more points, the terminals 705, 706, and 707 and the center station 704 arranged at three different points are connected to the communication lines 708, 709, At 710, the center station 704 is configured to relay image information from the terminals 705, 706, and 707.
[0006]
In this case, in the image communication between the center station 704 and the terminal stations 705, 706, and 707, there is a possibility that a slight difference in the transmission speed between the uplink and the downlink of the communication lines 708, 709, and 710 may occur. However, it is common to communicate using the same encoding method.
[0007]
By the way, in this case, each terminal 705, 706, and 707 may transmit screen information for one terminal using the uplink, whereas the center station 704 uses a plurality of downlinks. It is necessary to generate screen information for the terminal and transmit it to each communication line.
[0008]
For this reason, the transmission rate of the uplink (B bps) may be faster than the transmission rate of the downlink (C bps). In this case, in a TV conference or the like, since the images and sounds are transmitted to the terminals 705, 706, and 707 at the respective points, the conversation may become unnatural.
[0009]
In general, as an international standard of an image encoding system for a TV conference system, H.264 Although there is a system called H.261 (ITU-T Rec. H.261), since there was no other standard system until now, it was hardly necessary to consider connection with different encoding systems.
[0010]
However, in recent years, with the spread of digital CATV networks, MPEG2 (ISO / IEC 13818-2 | ITU-) is a new international standard for encoding high-quality images in downlink CATV. T Rec. H.262) has been used.
[0011]
When a CATV subscriber performs a TV conference using each terminal, it is most natural to use the MPEG2 system because the downlink has a decoder for MPEG2. If another method is adopted, a decoder of that method needs to be newly installed.
[0012]
On the other hand, it is natural for the uplink to transmit image information by the same encoding method as that of the downlink, that is, the MPEG2 method.
[0013]
However, the encoder for MPEG2 is very expensive, and the transmission speed of the uplink is generally much slower than that of the downlink, and MPEG2 is not efficient.
[0014]
In such a case, if MPEG2 adapted to the downlink is adopted as the uplink encoding method, an expensive and inefficient MPEG2 encoder is installed on the uplink, and the uplink is also provided. H. When the H.261 system is adopted, H.264 is newly added. A decoder for H.261 is required, which is a double investment with a decoder for MPEG2. In any case, an inefficient encoder or decoder is required, and the efficiency of capital investment and information transmission is reduced.
[0015]
[Problems to be solved by the invention]
As described above, in the conventional information communication system described above, when the same method is adopted for the uplink and the downlink, the time for arrival of information differs depending on the load amount of information transmitted to each line, When conducting a TV conference or the like, there is a problem that the conversation becomes unnatural.
[0016]
Also, even when different encoding methods are used for the uplink and the downlink, it is necessary to use an inefficient encoding method for either the uplink or the downlink, and the information transmission efficiency is poor. There was a problem.
[0017]
The present invention has been made to solve such problems, and it is an object of the present invention to provide an information communication system and a center station that can improve information transmission efficiency and perform information communication in a more natural manner. It is said.
[0018]
[Means for Solving the Problems]
In order to achieve the above-described object, the invention according to claim 1 is an information communication system in which at least one center station and a plurality of terminal stations are connected on a transmission line having uplink and downlink lines. station, the encoded with the first encoding method by the terminal stations, and an image decoding means for receiving and decoding the image information transmitted via the uplink, each decoded by the image decoding unit an image synthesizing means for synthesizing the image information into one image, and the image encoding means for encoding the images information synthesized by said image synthesizing means in the second encoding method, the second by the image encoding means Information transmission means for transmitting image information encoded by the encoding method 2 to each terminal station using the downlink, and each terminal station obtains image information transmitted from the own station. Do An image acquisition unit; an image encoding unit that encodes the image information acquired by the image acquisition unit by the first encoding method; and image information encoded by the image encoding unit via the uplink. Information transmission means for transmitting to the center station, image decoding means for receiving and decoding image information encoded by the center station using the second encoding method and transmitted via the downlink, and the image Display means for displaying the image information decoded by the decoding means.
[0020]
Further, the information communication system according to claim 2 is the information communication system according to claim 1, wherein the information transmission means of the center station simultaneously transmits image information to the plurality of terminal stations. It is characterized by comprising.
[0021]
An information communication system according to a third aspect of the present invention is the information communication system according to the first aspect, wherein the image encoding means of the center station is encoded by the first encoding method used in the uplink. The feature quantity of the data is extracted by variable-length decoding, converted to the feature quantity of the second encoding method used in the downlink, and the transmission data is variable-length encoded by this second encoding scheme. It is characterized by generating.
The information communication system according to claim 4 is the information communication system according to claim 3 , wherein the image encoding means of the center station performs quantization when the quantization characteristic value is an even number in the first encoding method. When the decoded value is corrected to an odd number, a quantization characteristic value is given such that the quantized decoded value becomes an odd number in the second coding scheme, and the quantized decoded value is quantized decoding in the first coding scheme. The quantization value in the second encoding method is determined to be equal to the value.
[0022]
An information communication system according to a fifth aspect of the present invention is the information communication system according to the third aspect , wherein the image encoding means of the center station is a macro to which an in-loop filter is applied in the first encoding method. For the block, the value of the motion vector is changed to a value shifted by a half pixel by the second encoding method.
Further, an information communication system according to a sixth aspect of the present invention is the information communication system according to the fifth aspect , wherein the image encoding means of the center station shifts the value of the motion vector by half a pixel or a field unit or field. It is characterized by changing in order of upper left, lower right, lower left, and upper right in units.
The center station according to claim 7, wherein the center station is connected to a plurality of terminal stations via a transmission line having uplink and downlink lines, and is encoded by each terminal station using a first encoding method, Image decoding means for receiving and decoding each image information transmitted through the uplink, image composition means for synthesizing each image information decoded by the image decoding means into one image, and composition by the image composition means Image encoding means for encoding the image information obtained by the second encoding method; and image information encoded by the image encoding means by the second encoding method using the downlink And an information transmission means for transmitting to each terminal station.
[0023]
In the above invention, an optimum encoding method is adopted for each uplink and downlink, and the center station that relays image information from a plurality of terminal stations converts the encoding method of image information from each terminal station, The image information combined on one screen is transmitted by broadcast communication.
[0024]
Therefore, the difference in arrival time is reduced in the image information delivered to each terminal station via the upstream and downstream lines, and a TV conference or the like can be performed in a good natural form.
[0025]
That is, by adopting optimum encoding methods for the uplink and downlink, respectively, it is possible to perform information communication efficiently in conformity with the network.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 is a schematic diagram of a video conference system which is an embodiment of an information communication system according to the present invention.
[0028]
As shown in FIG. 1, this video conference system is configured by connecting a plurality of terminals 101, 102, 103, 104 and a center station 10 via a communication line 1 as a transmission path. The communication line 1 has an uplink line (uplink) and a downlink line (downlink). Video data is transmitted from the center station 10 to the terminals 101, 102, 103, and 104 through the downlink by the MPEG2 system that is the second encoding system, while the terminals 101, 102, 103, and 104 are connected to the center. To the station 10, the first encoding method H.264 is used. The moving image data is transmitted through the uplink by the H.261 system or the like.
[0029]
The center station 10 receives the H.264 received from the communication line 1. The bit stream converting unit 11 converts a 261 bit stream into an MPEG2 bit stream, and an image combining unit 12 combines the converted MPEG2 bit streams so as to be integrated into one screen.
[0030]
The terminal 101 includes a camera 131 that captures the conference participants of the local station, and image data of the conference participants captured by the camera 131 as H.264. An encoder (ENC) 111 that encodes a 261 bit stream and sends it to the communication line 1; a decoder (DEC) 121 that decodes the MPEG2 bit stream received from the communication line 1; and an image decoded by the decoder 121. It is comprised from the monitor 141 which displays. Since the terminals 102, 103, and 104 other than the terminal 101 are configured in the same manner as the terminal 101, description of each configuration is omitted.
[0031]
As shown in FIG. 2, the bit stream converter 11 receives the H.264 received by the center station 10 through the communication line 1. H.261 decoding a bitstream into moving image data A 261 decoder 201 and an MPEG2 encoder 202 that encodes the decoded moving image data into an MPEG2 bit stream.
[0032]
As shown in FIG. 3, the image composition unit 12 includes a plurality of decoders 301, 301, 302, 303, 304 for decoding each MPEG2 bit stream into moving image data, and these decoders 301, 301, 302, 303. , 304 is a screen rearrangement unit 305 for rearranging the screen of the moving image data on one screen, and the one-screen data rearranged by the screen rearrangement unit 305 is encoded into an MPEG2 bit stream for communication. The encoder 306 is sent to the line 1.
Next, the operation of this video conference system will be described.
[0033]
First, in this TV conference system, a case where the center station 10 relays information from a plurality of terminals 101, 102, 103, and 104 and transmits the information to each terminal 101, 102, 103, and 104 will be described.
[0034]
In this case, video captured by the cameras 131, 132, 133, and 134 connected to the terminals 101, 102, 103, and 104 is converted into H.264 by the encoders 111, 112, 113, and 114 in each terminal. It is encoded into a 261 bit stream. The encoded data is transmitted to the center station 10 through the communication line 1.
[0035]
Each H.C. sent to the center station 10. The data of the H. 261 bit stream is stored in the H.264 in the bit stream converter 11. After being decoded by the H.261 decoder 201, the MPEG2 encoder 202 encodes the MPEG2 bit stream and outputs it to the image composition unit 12.
[0036]
In the image synthesizing unit 12, the MPEG2 bit stream is decoded into moving image data by the respective decoders 301, 301, 302, 303, and 304, and each moving image data is converted into moving image data of one screen by the screen rearranging unit 305. Are rearranged (synthesized) as The rearranged moving picture data of one screen is encoded into an MPEG2 bit stream by the encoder 306, and transmitted again to the terminals 101, 102, 103, and 104 through the communication line 1 (downlink).
[0037]
The data sent to each of the terminals 101, 102, 103, 104 via the communication line 1 is decoded from the MPEG2 bit stream into moving image data by the respective internal decoders 121, 122, 123, 124, and the respective monitors 141, One screen is displayed as a moving image divided into four on the display screens 142, 143, and 144. Thus, according to the TV conference system of this embodiment, the H. Data transmission is performed using the H.261 system and the MPEG2 system on the downlink. As a result, data communication can be performed with an encoding method suitable for the image data of each line. For example, H. By providing the bit stream converting unit 11 of 261 → MPEG2, the screen synthesizing unit 12, and the like, the converted data can be smoothly transmitted to the upstream and downstream lines without time difference, and the data transmission time is delayed. Therefore, each encoding method is adapted to the network, the transmission efficiency of moving image data is improved, and a TV conference can be held in a more natural form.
[0038]
Hereinafter, other embodiments of the TV conference system will be described.
[0039]
The configuration example of the bit stream conversion unit 11 shown in FIG. 2 is very simple, but information may be lost because it is encoded again after decoding, which causes deterioration in image quality. In addition, since a lot of time is spent on decoding and encoding processing, information transmission tends to be delayed.
[0040]
Therefore, as shown in FIG. By using the bit stream conversion unit 41 including a variable length decoder VLD 401 of H.261, a data reconstruction unit 402, and a variable length encoder VLC 403 of MPEG2, only variable length decoding is performed so that loss of information does not occur as much as possible. It is also possible to convert the image information in a state where the operation is performed.
[0041]
In this case, the input H.P. The 261 bit stream is H.264. The variable length decoding is performed by the H.261 VLD 401, and information held in the bit stream is extracted. H. Although the basic scheme is the same although the encoding schemes of H. 261 and MPEG2 differ in detail, the data reconstruction unit 402 performs H.264 encoding. Information of the H.261 encoding system is analyzed and converted to information of the MPEG2 encoding system. The information reconstructed (converted) by the data restructuring unit 402 is header information such as a start code, motion vector information, DCT coefficient component information, and the like. The start code and macro block position designation are converted into MPEG2 codes. The value of the motion vector information is doubled because MPEG2 is half pixel compatible. The DCT coefficient component is converted according to the quantization characteristic value. The converted information is variable length encoded by the MPEG2 variable length encoder VLC 403, and an MPEG2 bit stream is output.
[0042]
As described above, according to the video conference system of this embodiment, data conversion is performed in a state where only variable length decoding (VLD) is performed without performing inverse DCT processing or motion compensation processing. The video conference can be held in a more natural way with less time.
[0043]
In addition, the configuration example of the image composition unit 12 shown in FIG. 3 is very simple, but since it is encoded again after decoding, image quality degradation and delay time occur.
[0044]
Therefore, the image synthesis unit 12 includes variable length decoders (VLD) 501, 502, 503, and 504, a variable data conversion unit 505, and a variable length encoder (VLC) 506, as shown in FIG. By using the image composition unit 52, it is possible to reconstruct (convert) image information in a state where only variable-length decoding is performed.
[0045]
In this case, each bit stream input to the image composition unit 52 is variable-length decoded by variable-length decoders (VLD) 501, 502, 503, and 504, and information held in the bit stream is extracted. The extracted information is converted by the variable data conversion unit 505 according to the position where the image data is newly arranged, and the data is rearranged in the order of encoding (bit stream reconstruction).
[0046]
This information is variable length encoded by a variable length encoder (VLC) 506 and an MPEG2 bit stream is output.
[0047]
Thus, according to the video conference system of this embodiment, image information conversion (bit stream reconstruction) is performed in a state where only variable-length decoding is performed without performing inverse DCT processing or motion compensation processing. Loss is small and delay time can be reduced.
[0048]
H. Complete data conversion cannot be performed between the H.261 system and the MPEG2 system.
[0049]
As a technique for performing data conversion, there are an in-loop filter and an inverse quantization process.
[0050]
H. In the H.261 system, there is a mode in which a filter having coefficient characteristics as shown in FIG. 6 is applied in order to reduce the block distortion rate due to motion compensation, but in the MPEG2 system, a filter cannot be applied. Since this filter is in the loop of the encoding process, the disturbance of the decoded image due to this error increases with time.
[0051]
As a method of reducing this error, MPEG2 half-pixel prediction is used.
[0052]
For example, by moving the value of the motion vector in the MPEG2 system by half a pixel to the upper left as shown by the “x” mark in FIG. 7A, the same effect can be obtained by applying the filter characteristics as shown in FIG. be able to.
[0053]
Further, by shifting the value of the motion vector in order as shown in FIGS. 7B to 7D, the filter coefficients shown in FIG. 6 can be approximated on average.
[0054]
H. In the case of the inverse quantization process in the H.261 system, the inverse quantization value (REC) is given by the following equation from the quantization characteristic value (QUANT) and the quantization representative value (LEVEL).
[0055]
If QUANT is odd,
REC = QUANT × (2 × LEVEL + 1); LEVEL> 0
REC = QUANT × (2 × LEVEL-1); LEVEL <0
If QUANT is an even number,
REC = QUANT × (2 × LEVEL + 1) −1; LEVEL> 0
REC = QUANT × (2 × LEVEL-1) +1; LEVEL <0
On the other hand, in the case of the MPEG2 system, the inverse quantization value (F) is given by the following expression as the quantization representative value (QF), the quantization characteristic value (QS), and the value (W) based on the quantization matrix.
[0056]
F = ((2 × QF + 1) × W × QS / 32); QF> 0
F = ((2 × QF−1) × W × QS / 32); QF <0
Therefore, if QUANT is an odd number,
QF = LEVEL, QS = QUANT × 32 / W
By doing so, REC and F can be matched, but when QUANT is an even number, they cannot simply be matched.
[0057]
Therefore, in this case, using MPEG2 system escape encoding, etc.

By doing so, F can be approximated to REC.
[0058]
With this concept, when the form of the bit stream converter 41 shown in FIG. 4 and the form of the image composition unit 52 shown in FIG. 5 are combined to realize a new center station, the bit stream converter 41 and The variable length decoder (VLD) and the variable length encoder (VLC) overlap between the image synthesis units 52.
[0059]
Therefore, a new center station 60 can be configured by omitting VLD and VLC one by one from the bit stream conversion unit 41 and the image composition unit 52.
[0060]
As shown in FIG. 9, the center station 60 includes variable length decoders 601, 602, 603, and 604, encoding scheme conversion units 611, 612, 613, and 614, an arrangement conversion unit 605, and variable length encoding. Unit (VLC) 606.
[0061]
In this case, each H.P. Each H.261 bit stream is an H.264 bit stream. The variable length decoders 601, 602, 603, and 604 perform variable length decoding, and information included in the bit stream is extracted. The extracted information is converted into MPEG2 information by each of the encoding method conversion units 611, 612, 613, and 614, and further, the location information is converted and rearranged in accordance with the newly arranged position by the arrangement conversion unit 605. . This information is variable length encoded by an MPEG2 variable length encoder (VLC) 606, and an MPEG2 bit stream is output.
[0062]
According to the video conference system of this embodiment, the center station 10 is configured by omitting one VLD and one VLC from the bit stream converting unit 11 and the image synthesizing unit 12, and converting the same encoding method as described above. Processing can be performed.
[0063]
In addition, this invention is not limited only to embodiment mentioned above.
[0064]
In the embodiment described above, H. 261, each scheme of MPEG2 is applied to the downlink, but if there is an optimal encoding scheme other than this, it may be applied.
[0065]
In the above-described embodiment, the uplink coding scheme is the same, but there may be a plurality of uplink coding schemes. In this case, the center station may be provided with a decoder or variable length decoder adapted for each uplink.
[0066]
Furthermore, in the above-described embodiment, the same bit stream is output to each terminal on the downlink, but a different bit stream may be output for each terminal. In this case, as many output function units for screen layout conversion as the number of bit streams to be output may be prepared, and variable length encoding may be performed. Thereby, a different video can be received for each terminal. Also, by inserting an encoding method converter before the variable length encoder, it is possible to transmit bit streams of different encoding methods for each terminal.
[0067]
【The invention's effect】
As described above, according to the present invention, in the center station, information is converted by an efficient and optimal coding scheme for each of the uplink and downlink, so that communication between the terminal stations can be performed efficiently. Can do.
[0068]
In addition, since the center station combines a plurality of pieces of image information on a single screen and transmits them simultaneously to the downlink, the difference in arrival time between the information on the uplink and the information is reduced. , There is no delay in the movement of the image, you can talk more naturally.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a video conference system according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a bit stream conversion unit of the TV conference system of FIG. 1;
3 is a block diagram showing an image composition unit of the TV conference system of FIG. 1. FIG.
FIG. 4 is a block diagram showing another embodiment of the bit stream conversion unit of FIG. 2;
FIG. 5 is a block diagram showing another embodiment of the image composition unit in FIG. 3;
FIG. FIG. 26 is a diagram illustrating coefficients of an in-loop filter in H.261.
FIGS. 7A to 7D are diagrams illustrating motion vector values based on MPEG2 half-pixel prediction.
FIG. It is a figure which shows the coefficient by the half pixel prediction of the MPEG2 system approximated to the filter in the loop in a H.261 system.
9 is a diagram in the case where a new center station is realized by combining the form of the bit stream conversion unit shown in FIG. 4 and the form of the image composition unit shown in FIG.
FIG. 10 is a block diagram showing a configuration of a conventional video conference system between two points.
FIG. 11 is a block diagram illustrating a configuration of a conventional video conference system between three points.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Communication line 10, 60 ... Center station, 11, 41 ... Bit stream conversion part, 12, 52 ... Image composition part, 101, 102, 103, 104 ... Terminal, 111, 121, 131, 141 ... H.261 Encoder 121, 122, 123, 124 ... MPEG2 decoder, 131, 132, 133, 134 ... Camera, 141, 142, 143, 144 ... Monitor.

Claims (7)

In an information communication system in which at least one center station and a plurality of terminal stations are connected on a transmission line having uplink and downlink lines,
The center station
Image decoding means for receiving and decoding each piece of image information encoded by each terminal station using the first encoding method and transmitted through the uplink;
Image combining means for combining each image information decoded by the image decoding means into one image;
And image encoding means for encoding images information synthesized by said image synthesizing means in the second encoding method,
Information transmission means for transmitting the image information encoded by the image encoding means by the second encoding method to each terminal station using the downlink,
Each terminal station is
Image acquisition means for acquiring image information transmitted from the own station;
Image encoding means for encoding the image information acquired by the image acquisition means by the first encoding method;
Information transmission means for transmitting the image information encoded by the image encoding means to the center station via the uplink;
Image decoding means for receiving and decoding image information encoded by the center station using the second encoding method and transmitted via the downlink;
An information communication system comprising display means for displaying the image information decoded by the image decoding means. The information communication system according to claim 1,
An information communication system , wherein the information transmission means of the center station comprises broadcast communication means for simultaneously sending image information to the plurality of terminal stations . The information communication system according to claim 1,
The image encoding means of the center station extracts the feature amount of the data encoded by the first encoding method used in the uplink by variable length decoding, and uses it in the downlink. 2. An information communication system, wherein the transmission data is generated by converting into feature quantities of the second encoding scheme and variable-length encoding using the second encoding scheme . The information communication system according to claim 3 ,
The image encoding means of the center station is
When the quantized decoded value is modified to an odd number when the quantized characteristic value is an even number in the first encoding method, the quantized characteristic value is an odd number in the second encoding method. And determining a quantized value in the second encoding method so that the quantized decoded value becomes equal to the quantized decoded value in the first encoding method . The information communication system according to claim 3 ,
The image encoding means of the center station is
For a macroblock to which an in-loop filter is applied in the first encoding method, the value of a motion vector is changed to a value shifted by half a pixel in the second encoding method. Information communication system. The information communication system according to claim 4 , wherein
The image encoding means of the center station is
An information communication system, wherein when the value of the motion vector is shifted by a half pixel, the motion vector is changed in order of upper left, lower right, lower left, and upper right in frame units or field units . In a center station connected to a plurality of terminal stations via a transmission path having upstream and downstream lines,
Image decoding means for receiving and decoding each image information encoded by each terminal station using the first encoding method and transmitted through the uplink;
Image synthesizing means for synthesizing each image information decoded by the image decoding means into one image; ,
Image encoding means for encoding the image information combined by the image combining means by a second encoding method;
Information transmission means for transmitting the image information encoded by the image encoding means by the second encoding method to each of the terminal stations using the downlink;
A center station characterized by comprising:

Images