Transmission system and relay device

Abstract

Provided is a system for supplying a power from a sink device to a source device. Not only the source device but also a cable or a repeater device to be connected thereto has compatibility in power supply. A physical address obtained from information of an EDID memory forms a base of CEC message exchange, but a physical address of the cable or repeater device is overlapped with the source device or unknown. The cable or a repeater device uses changes the type of a message while using the same physical address as the source device or use such a message having the physical address information of the source device is described in a parameter of the message using the unknown physical address. The message having a supply or reception current for each device described therein is exchanged with the sink device or the source device to adjust current reception.

The invention claimed is:  
     
       1. A relay device adapted to be positioned in a transmission system for transmitting a video signal from a source device to a sink device, the relay device comprising:
 a video signal receiving unit that receives the video signal from the source device; 
 a video signal transmitting unit that transmits the video signal to the sink device; 
 a first communication unit that receives a first message regarding a power supply capability of the sink device; 
 a second communication unit that transmits a second message regarding a power supply capability of the relay device to the source device; 
 a first power circuit that receives power supplied by the sink device; and 
 a second power circuit that supplies power to the source device; 
 wherein an amount of sum of the power supply capability of the relay device and power consumed at the relay device does not exceed an amount of power supply capability of the sink device, and 
 wherein an amount of power to be supplied from the second power circuit to the source device is arranged to be difference between an amount having been supplied from the sink device to the first power circuit and another amount consumed at the relay device. 
 
     
     
       2. The relay device according to  claim 1 , wherein the amount of power having been consumed at the relay device comprises amounts of power consumed at both the video signal receiving unit and the video signal transmitting unit; and
 wherein the first power circuit is arranged to transmit, to the source device, information on power supply capability of the relay device having been changed in response to other information on change of power supply capability of the sink device. 
 
     
     
       3. A method for transmitting a video signal from a source device to a sink device using a relay device, the method comprising:
 receiving, at the relay device, the video signal from the source device; 
 transmitting, by the relay device, the video signal to the sink device; 
 receiving, at the relay device, a first message regarding a power supply capability of the sink device; 
 transmitting, by the relay device, a second message regarding a power supply capability of the relay device to the source device; 
 receiving, at the relay device, power supplied by the sink device; and 
 transmitting, by the relay device, power to the source device; 
 wherein an amount of sum of the power supply capability of the relay device and power consumed at the relay device does not exceed an amount of power supply capability of the sink device, and 
 wherein an amount of power to be supplied from the second power circuit to the source device is arranged to be difference between an amount having been supplied from the sink device to the first power circuit and another amount consumed at the relay device. 
 
     
     
       4. The method according to  claim 3 , wherein the amount of power having been consumed at the relay device comprises amounts of power consumed at both the video signal receiving unit and the video signal transmitting unit; and
 wherein the first power circuit is arranged to transmit, to the source device, information on power supply capability of the relay device having been changed in response to other information on change of power supply capability of the sink device.