JPH04310084A - Refresh system in inter-multi-point communication system - Google Patents

Abstract

PURPOSE:To realize the refresh system validating only required demand refresh in the inter-multi-point communication having one transmission section and reception sections of a subscriber number at one point. CONSTITUTION:When a fault of a transmission line between points A and B is detected at the point A, fault information 10 is sent to a transmission line 1 and a demand refresh signal 11 is sent to a subscriber reception section by the information. A reception section 6 at the point B uses the demand refresh signal 11 to recognize the occurrence of the fault between the points A and B, a transmission section 2 sends a refresh request signal 12 and the transmission section 2 sends an in-frame coding signal 14. The reception section 6 at a point C recognized it that no transmission fault is in existence between the points A and C and does not request the transmission of the in-frame coding signal to a transmission section 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint communication system in which three or more points communicate with each other.

0002

2. Description of the Related Art FIG. 3 is a block diagram showing conventional multipoint communication. Here, an example of three locations is shown. Here, 1 to 3 are transmitters at points A, B, and C, and 4 to 9 are transmitters at points A, B, and
, is the receiving section at point C. Conventional refresh methods include: 1. Demand refresh that performs refresh when an error is detected; 2. Two types of methods have been used: periodic refresh, which performs refresh periodically regardless of the presence or absence of errors.

Next, the operation 1 will be explained with reference to FIG. Here, an example is given in which a transmission path error occurs between A and B. In FIG. 4, 10 is error information regarding a transmission path error between A and B, 11 is a demand refresh signal from point A, 12 and 13 are refresh request signals from the receiving section to the transmitting section at points B and C, 14, 15 is B, C
This is an intraframe encoded signal from a point. Other parts 1 to 9 are the same as those in FIG. When a transmission path error is detected at the receiving section at point A, error information 10 regarding the transmission path error between A and B is transmitted to the transmitting section 1 at point A. The transmitter 1 at point A transmits the demand refresh signal 11 to the receivers 6 and 9 at points B and C, regardless of whether the error occurs in the transmission path between A and B or between A and C. . Receiving units 6 and 9 at points B and C, which have received this demand refresh signal 11, transmit the transmitter 2 at their own point.
, 3, the refresh request signals 12, 13 are transmitted. Transmitting units 2 and 3 at each point transmit intraframe encoded signals 14 and 1
5 and rewrites the frame memories of the receiving units 4 and 5 to eliminate the influence of transmission path errors. The above process is the conventional demand refresh method.

Next, the operation 2 will be explained with reference to FIG. Here, we will focus on point A. Symbols 1 to 9 and 14 to 15 in the figure are the same as those in FIGS. 3 and 4. In periodic refresh, regardless of the presence or absence of a transmission path error, the transmitting units 2 and 3 at points B and C, which are the destinations of point A, transmit intra-frame encoded signals 14 and 15 at fixed intervals, and the receiving unit at point A By rewriting frame memories 4 and 5, even if a transmission path error occurs, the influence of the transmission path error is eliminated within a certain period of time. The above process is the conventional periodic refresh method.

[0005]

[Problems to be Solved by the Invention] In the conventional demand refresh method, even if a transmission path error occurs between A and B in FIG. An intra-frame encoded signal is transmitted from the transmitting unit of the frame. Therefore a. If the network charges for the amount of information, the amount of information generated increases due to wasteful intra-frame coding, which is uneconomical. b. If the network is at a fixed speed (for example, 1.5 Mbps), the amount of information temporarily increases, resulting in dropped frames, and the quantizer is increased in size to suppress the amount of information, resulting in a deterioration in image quality. Resulting in. There was a problem. Another problem with conventional periodic refresh is that the sending side does not recognize that a transmission path error has occurred, so in the worst case, the screen remains distorted for one period. there were.

The present invention was made in order to solve the above-mentioned problems, and its object is to provide a refresh method that effectively applies only the necessary demand refresh in multipoint communication.

[0007]

[Means for Solving the Problems] The refresh method according to the present invention is such that refresh is performed only from the destination where a transmission path error has occurred using a demand refresh signal.

[0008] Furthermore, the address of the destination where the transmission path error occurred is added to the demand refresh signal.

[0009]

[Operation] In the refresh method described above, the destination where a transmission path error has occurred receives a demand refresh signal, and refresh is performed from a necessary point only when necessary.

Furthermore, by adding the address of the destination where the transmission path error has occurred to the demand refresh signal, refresh is performed from the necessary point and only when necessary.

[0011]

[Example] Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention, and 1 to 12 and 14 in the figure are the same as those shown in FIG. 4. When a transmission path error is detected at the receiving section at point A, error information 10 regarding the transmission path error between A and B is transmitted to the transmitting section 1 at point A. The transmitter 1 at point A adds the fact that a transmission path error has occurred between A and B to the demand refresh signal 11, and sends the message B,
It is transmitted to the receiving sections 6 and 9 at point C. The receiving unit 6 at point B, which received this demand refresh signal 11, reads from the demand refresh signal 11 that a transmission path error has occurred between A and B, and sends it to the transmitting unit 2 at its own point.
A refresh request signal 12 is transmitted. The transmitter 2 transmits the intraframe encoded signal 14, rewrites the frame memory of the receiver 4, and eliminates the influence of transmission path errors. Further, the receiving section 9 at point C receives the demand refresh signal 11, but the receiving section 9 reads that no transmission path error has occurred between A and C, and does not transmit the refresh request signal to the transmitting section 3. With the above operation, the intraframe encoded signal is transmitted only from point B, and the influence of transmission path errors between A and B is eliminated.

Example 2. FIG. 2 shows an example of a method for adding information that a transmission path error has occurred between A and B to a demand refresh signal. During normal communication, it is divided into a header part and a data part. Only information as to whether the signal is a current demand refresh signal or not is given in the header part. By adding a unique address to each point in this part, it becomes possible to limit the section where a transmission path error has occurred and perform refresh only on the necessary section.

[0013]

[Effects of the Invention] As explained above, the present invention is a refresh method in multi-point communication, in which an intra-frame encoded signal can be obtained from a necessary point when necessary using a demand refresh signal to which an address is added. This has the effect of suppressing the amount of wasteful information generated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a method for adding an address according to a second embodiment of the present invention.

FIG. 3 is a block diagram representing conventional multipoint communication.

FIG. 4 is a diagram illustrating an example of conventional demand refresh operation.

FIG. 5 is a diagram illustrating an example of conventional periodic refresh operation.

[Explanation of symbols]

1 to 3 Transmitting units 4 to 9 at each point Receiving unit 10 at each point Error information 11 for transmission path errors
Demand refresh signal 12 Refresh request signal from receiving section to transmitting section 14 Intra-frame encoded signal

Claims (2)

[Claims] Claim 1. In an image transmission device using an interframe coding method, in a multipoint communication method having one transmitting section and receiving sections as many as the number of destinations, when a transmission path error is detected in the receiving section, A refresh method in a multipoint communication system characterized by transmitting a demand refresh signal to multiple destinations, but transmitting an intraframe-encoded signal only from a transmitter at a specific destination. Claim 2: In the above multipoint communication system, when a transmission path error is detected in the receiving section, when performing a demand refresh, the address of the destination where the transmission path error occurred is added to the demand refresh signal from the transmitting section. A refresh method in a multipoint communication system characterized by the addition of