Video conference system and video conference method

A video conference method used in a video conference system including an application server and a plurality of devices that are connected to the application server through a communication network and receive a Web application from the application server, the method comprising:

• determining, by the application server, a screen layout according to the number of participants in a video conference and a media transmission and reception flow going through all devices used by the participants, and transmitting the screen layout and the media transmission and reception flow to each of the plurality of devices, and
• transmitting, by at least one device of the plurality of devices, a screen image where an image generated by the at least one device is superimposed in an upper layer of a base layer, the base layer being an image received from a device located previous to the at least one device in the media transmission and reception flow, according to the screen layout received from the application server by using the Web application, to a device located subsequent to the at least one device in the media transmission and reception flow, when a change occurs in communication state, acquiring communication quality information concerning transmission and reception of the at least one device, and transmitting the communication quality information to the application server,
• receiving, by the application server, the communication quality information, analyzing the communication quality information, and updating quality of an image displayed by the at least one device,
• when the application server receives the communication quality information indicating degradation of communication quality from the at least one device, making, by the application server, a modification to the media transmission and reception flow so that only the image generated by the at least one device is transmitted from the at least one device to the device located subsequent to the at least one device, and an image serving as the base layer is transmitted from the device located previous to the at least one device to the device located subsequent to the at least one device and from the device located subsequent to the at least one device to the at least one device, and transmitting the modified media transmission and reception flow to each of the plurality of devices,
• receiving, by the device subsequent to the at least one device, the image serving as the base layer from the device previous to the at least one device, and
• transmitting, by the at least one device, only the image generated by the at least one device to the device located subsequent to the at least one device, and receiving the image serving as the base layer from the device subsequent to the at least one device.