Abstract:
A communication device includes multiple output terminals configured to output, through an interface including at least a signaling channel through which a baseband signal is transmitted in one direction and a bidirectional control channel used for control, the baseband signal, one or more input terminals configured to be input with the baseband signal through the interface, and a control unit, the multiple output terminals including a primary output terminal through which the control is preferentially performed with another device connected to the one or more input terminals and one or more further secondary output terminals, and the control unit configured to perform a control of notifying another device connected to the secondary output terminal of a function of another device connected to the one or more input terminals as a function of the communication device via the control channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. JP 2010-038227 filed in the Japanese Patent Office on Feb. 24, 2010, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a communication device, a communication control method, and a program, and particularly relates to a communication device, a communication control method, and a program that can improve user-friendliness of devices connected to multiple output terminals. 
     2. Description of the Related Art 
     In recent years, the HDMI® has become widespread as a communication interface for high-speed transmission of a baseband (uncompressed) image (video) signal and an audio signal associated with an image thereof. 
     The HDMI® specification is an interface specification for digital consumer electronics (home appliances). The specification is arranged for audio-visual (AV) electronics based on the Digital Visual Interface (DVI), which is a standard specification for connecting a personal computer (PC) and a display device. 
     There are three types of devices (referred to below as HDMI® devices) which are to be connected via HDMI®, namely, an HDMI® source, an HDMI® sink, and an HDMI® repeater. 
     The HDMI® source includes an output terminal from which an image or audio signal is output via HDMI®, and the HDMI® sink includes an input terminal to which the image or audio signal is input via HDMI®. The HDMI® repeater includes one or more input terminals and one or more output terminals to act as both the HDMI® source and the HDMI® sink. 
     The HDMI® includes a transition minimized differential signaling (TMDS) channel, a consumer electronics control (CEC) line, and other channels. The TMDS channel is a signaling channel through which a baseband image or audio signal is transmitted in one direction from the HDMI® source to the HDMI® sink via the appropriate HDMI® repeater. The CEC line is a bidirectional control channel used in controlling the HDMI® source, the appropriate HDMI® repeater, and the HDMI® sink. 
     That is, the HDMI® uses the TMDS channel for the physical layer and uses the CEC line for connection of an overall control system for devices connected with HDMI®. 
     Also, the HDMI® uses the High-bandwidth Digital Content Protection (HDCP) to encrypt a signal for fulfilling a copyright protection function. 
     Further, the HDMI® uses the Extended Display Identification Data (EDID) for device identification. 
     That is, the HDMI® uses a DDC/EDID method of the Video Electronics Standard Association (VESA) for device identification. 
     The Display Data Channel (DDC) is used by the HDMI® source to read the EDID (or Enhanced Extended Display Identification Data (E-EDID)) from the HDMI® sink and the HDMI® repeater. 
     That is, the HDMI® sink and the HDMI® repeater include an EDID read only memory (EDID ROM) storing the EDID which is information regarding one&#39;s configuration or capability. The HDMI® source reads the EDID stored in each EDID ROM of the HDMI® sink and the HDMI® repeater via the DDC to recognize the configuration or the capability of the HDMI® sink and the HDMI® repeater based on the EDID. The EDID includes, for example, brand (manufacturer) of the HDMI® sink, model number, and format (e.g., image resolution) of signal supported by the HDMI® sink. 
       FIG. 1  shows an example of a connection of HDMI® devices via the HDMI® repeater including two output terminals. 
     An AV system in  FIG. 1  includes a Blu-ray Disc® (BD) player  11 , an AV amplifier  12 , a TV (television receiver)  13 , and a projector  14 . Note that a system in this specification refers to a logical collection of multiple devices, regardless of whether devices of respective configurations are in a single case. 
     The BD player  11  is the HDMI® source, the AV amplifier  12  is the HDMI® repeater, and the BD player  11  and the AV amplifier  12  are connected by an HDMI® cable  15 . The TV  13  and the projector  14  are both the HDMI® sink, the AV amplifier  12  and the TV  13  are connected by an HDMI® cable  16 , and the AV amplifier  12  and the projector  14  are connected by an HDMI® cable  17 . 
     The BD player  11  outputs an image and audio signal (also referred to below as AV signal) read from a BD as an HDMI® data stream. The AV amplifier  12  outputs the input HDMI® data stream to the TV  13  and the projector  14  simultaneously. 
     Two HDMI® outputs of the AV amplifier  12  are set as a primary output and a secondary output in advance. In the HDMI® specification, CEC control can be executed with only one HDMI® output. Thus, the CEC control is performed with the primary HDMI® output. In the AV system in  FIG. 1 , the TV  13  is connected to the primary HDMI® output of the AV amplifier  12 , for example. 
     In this case, addressing for CEC in relation to the BD player  11  is performed only for the TV  13  connected to the primary HDMI® output to enable control with CEC. Meanwhile, addressing is performed for the projector  14  connected to the secondary HDMI® output only in relation to the AV amplifier  12  as the HDMI® repeater. In other words, the projector  14  does not exchange information with the BD player  11  connected to an HDMI® input of the AV amplifier  12 . 
     By connecting the TV  13  and the projector  14  to the two HDMI® outputs of the AV amplifier  12 , a user is expected to enjoy two display devices separately depending on contents or situation. 
     However, while a remote control of the TV  13  connected to the primary HDMI® output is capable of operations such as fast-forwarding of the BD player  11  and volume adjustment of the AV amplifier  12  with the CEC control of HDMI®, such operations are not performed with a remote control of the projector  14  connected to the secondary HDMI® output. Therefore, viewing with the projector  14  is extremely inconvenient. 
     One example solution to this problem is to enable CEC control of multiple HDMI® sinks by holding a physical address of an HDMI® source virtually (for example, see Japanese Unexamined Patent Application Publication No. 2008-153974). 
     SUMMARY OF THE INVENTION 
     However, a method of Japanese Unexamined Patent Application Publication No. 2008-153974 involves a cumbersome reconnection operation due to resetting of HPD or operation of DDC. 
     It is desirable to improve user-friendliness of devices connected to multiple output terminals. 
     A communication device according to an embodiment of the present invention includes multiple output terminals configured to output, through an interface including at least a signaling channel through which a baseband signal is transmitted in one direction and a bidirectional control channel used for control, the baseband signal, one or more input terminals configured to be input with the baseband signal through the interface, and a control means, the multiple output terminals including a primary output terminal through which the control is preferentially performed with another device connected to the one or more input terminals and one or more further secondary output terminals, and the control means for performing a control of notifying another device connected to the secondary output terminal of a function of another device connected to the one or more input terminals as a function of the communication device via the control channel. 
     In a communication control method according to another embodiment of the present invention, a communication device including multiple output terminals configured to output, through an interface including at least a signaling channel through which a baseband signal is transmitted in one direction and a bidirectional control channel used for control, the baseband signal and one or more input terminals configured to be input with the baseband signal through the interface, the multiple output terminals including a primary output terminal through which the control is preferentially performed with another device connected to the one or more input terminals and one or more further secondary output terminals, performs a control of notifying another device connected to the secondary output terminal of a function of another device connected to the one or more input terminals as a function of the communication device via the control channel. 
     A program according to still another embodiment of the present invention causes a computer of a communication device including multiple output terminals configured to output, through an interface including at least a signaling channel through which a baseband signal is transmitted in one direction and a bidirectional control channel used for control, the baseband signal and one or more input terminals configured to be input with the baseband signal through the interface, the multiple output terminals including a primary output terminal through which the control is preferentially performed with another device connected to the one or more input terminals and one or more further secondary output terminals, to execute a process of notifying another device connected to the secondary output terminal of a function of another device connected to the one or more input terminals as a function of the communication device via the control channel. 
     According to the embodiments of the present invention, the process of notifying another device connected to the secondary output terminal of a function of another device connected to the one or more input terminals as a function of the communication device via the control channel is executed. 
     Note that the program can be provided through transmission via a transmission medium or recording on a recording medium. 
     The communication device may be an individual device or may be an internal block forming one apparatus. 
     According to the embodiments of the present invention, user-friendliness of devices connected to multiple output terminals can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a connection of HDMI® devices via the HDMI® repeater including two output terminals; 
         FIG. 2  is a block diagram showing a configuration example of an AV system according to an embodiment of the present invention; 
         FIG. 3  illustrates a physical address and a logical address of each HDMI® device in the AV system in  FIG. 2 ; 
         FIG. 4  is a block diagram showing a configuration example of an AV amplifier; 
         FIG. 5  is a flowchart illustrating an address acquisition process within a primary cluster; 
         FIG. 6  is a flowchart illustrating an address acquisition process within a secondary cluster; 
         FIG. 7  illustrates a logical address set in the secondary cluster; and 
         FIG. 8  is a flowchart illustrating a process when reproduction of contents is performed from a projector. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [Configuration Example of an AV System] 
       FIG. 2  shows a configuration example of an AV system according to an embodiment of the present invention. 
     The AV system in  FIG. 2  includes a game console  21 , a recording/reproducing device  22 , a reproducing device  23 , a set-top box (STB)  24 , an AV amplifier  25 , a TV  26 , and a projector (multimedia projector)  27 . 
     Each device forming the AV system is an HDMI® device. More specifically, the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24  are HDMI® sources, the AV amplifier  25  is an HDMI® repeater, and the TV  26  and the projector  27  are HDMI® sinks. 
     Categorized under “playback device” in terms of device type among HDMI® devices, the game console  21  outputs an AV signal read from a predetermined recording medium as an HDMI® data stream. The game console  21  is connected to an HDMI® input terminal IN1 of the AV amplifier  25  with an HDMI® cable  31 . 
     The recording/reproducing device  22  corresponds to what is generally called a personal video recorder (PVR) or a digital video recorder (DVR). The recording/reproducing device  22  includes, for example, a built-in hard disk to record contents on the built-in hard disk, reproduce the contents on the hard disk, and output a reproduced AV signal as an HDMI® data stream. The recording/reproducing device  22  is categorized under “recording device” in terms of device type among HDMI® devices. The recording/reproducing device  22  is connected to an HDMI® input terminal IN2 of the AV amplifier  25  with an HDMI® cable  32 . 
     The reproducing device  23  is, for example, a Blu-ray Disc® (BD) player or a digital versatile disc (DVD) player which outputs an AV signal read from an optical disc recording medium, such as a BD or a DVD, as an HDMI® data stream. The reproducing device  23  is categorized under “playback device” in terms of device type among HDMI® devices. The reproducing device  23  is connected to an HDMI® input terminal IN3 of the AV amplifier  25  with an HDMI® cable  33 . 
     Categorized under “tuner” in terms of device type among HDMI® devices, the STB  24  receives a television signal with a built-in tuner and outputs the television signal as an HDMI® data stream. The STB  24  is connected to an HDMI® input terminal IN4 of the AV amplifier  25  with an HDMI® cable  34 . 
     The AV amplifier  25  includes the four HDMI® input terminals IN1 to IN4 and two HDMI® output terminals OUT1 and OUT2 to output the HDMI® data stream input from the HDMI® input terminals IN1 to IN4 to the TV  26  and the projector  27 . Of the two HDMI® output terminals OUT1 and OUT2, the HDMI® output terminal OUT1 is a primary HDMI® output terminal. The HDMI® output terminal OUT1 is connected with the TV  26  with an HDMI® cable  35 , and the HDMI® output terminal OUT2 is connected with the projector  27  with an HDMI® cable  36 . The AV amplifier  25  is categorized under “audio system” in terms of device type among HDMI® devices. 
     Categorized under “TV” in terms of device type among HDMI® devices, the TV  26  outputs an image and audio based on the HDMI® data stream input from the AV amplifier  25  via the HDMI® cable  35 . The TV  26  comes with a remote control  26 R. 
     Categorized under “TV” in terms of device type among HDMI® devices, the projector  27  outputs an image based on the HDMI® data stream input from the AV amplifier  25  via the HDMI® cable  36 . The projector  27  comes with a remote control  27 R. 
     In the AV system configured in a manner described above, a user can cause the TV  26  and the projector  27  to display an image output from the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , or the STB  24  as the HDMI® source via the AV amplifier  25  to view the image. 
     [Physical Address and Logical Address of an HDMI® Device] 
       FIG. 3  shows a physical address and a logical address of each HDMI® device in the AV system in  FIG. 2  which are set based on the HDMI® specification. 
     According to the HDMI® specification, addressing for CEC is performed to assign the physical address (PA) and the logical address (LA) of the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , the STB  24 , the AV amplifier  25 , and the TV  26  connected to the primary HDMI® output terminal OUT1. In other words, the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , the STB  24 , the AV amplifier  25 , and the TV  26  form a cluster (primary cluster) which is controllable with CEC. 
     Within the primary cluster, the physical address of the game console  21  is (1.1.0.0) and the logical address is “4”, for example. The physical address of the recording/reproducing device  22  is (1.2.0.0) and the logical address is “1”. The physical address of the reproducing device  23  is (1.3.0.0) and the logical address is “8”. The physical address of the STB  24  is (1.4.0.0) and the logical address is “3”. The physical address of the AV amplifier  25  is (1.0.0.0) and the logical address is “5”. The physical address of the TV  26  is (0.0.0.0) and the logical address is “0”. 
     Also, addressing for CEC is performed to assign the physical address (PA) and the logical address (LA) of the AV amplifier  25  and the projector  27  connected to the secondary HDMI® output terminal OUT2. In other words, the AV amplifier and the projector  27  form a cluster (secondary cluster) which is controllable with CEC. 
     Within the secondary cluster, the physical address of the AV amplifier  25  is (1.0.0.0) and the logical address is “5”, for example. The physical address of the projector  27  is (0.0.0.0) and the logical address is “0”. 
     The clusters described above are formed according to the HDMI® specification, and the projector  27  connected to the secondary HDMI® output terminal OUT2 does not recognize the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24 . Therefore, for example, an operation of causing the reproducing device  23  to reproduce contents in a menu displayed in the projector  27  is not available. 
     Thus, the AV amplifier  25  as a communication device according to the embodiment of the present invention causes the logical address of the HDMI® source belonging to the primary cluster to be held virtually within the secondary cluster, so that the projector  27  can recognize the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24 . 
     [Configuration Example of the AV Amplifier  25 ] 
       FIG. 4  is a block diagram showing a configuration example of the AV amplifier  25 . 
     The AV amplifier  25  includes a CPU  51 , a RAM  52 , a ROM  53 , an HDMI® transmission unit  54 , an HDMI® control unit  55 , a U/I control unit  56 , an audio input unit  57 , an image input unit  58 , an image processing unit  59 , an audio processing unit  60 , an audio drive unit  61 , an HDMI® control unit  62 , and an HDMI® reception unit  64 . The CPU  51 , the RAM  52 , the ROM  53 , the HDMI® control unit  55 , the U/I control unit  56 , the audio input unit  57 , the image input unit  58 , the image processing unit  59 , the audio processing unit  60 , the audio drive unit  61 , and the HDMI® control unit  62  are interconnected by a bus. 
     Note that, in  FIG. 4 , an external speaker  63  not shown in  FIG. 2  is connected to the AV amplifier  25 . 
     The central processing unit (CPU)  51  performs an overall control of the entire AV amplifier  25  by executing a program stored in the read only memory (ROM)  53 . 
     Into the random access memory (RAM)  52 , the program to be executed by the CPU  51  is loaded. The RAM  52  also functions as a work area for the CPU  51 . That is, the RAM  52  stores data for operation of the CPU  51 . 
     The ROM  53  stores a program which is to be executed by the CPU  51  for a process (control) described later. 
     According to a control by the HDMI® control unit  55 , the HDMI® transmission unit  54  transmits an AV signal to the TV  26  and the projector  27  via the cables  35  and  36  (see  FIG. 2 ) and causes a control signal to be exchanged (relayed) between the TV  26  and the projector  27 . 
     According to the control by the CPU  51 , the HDMI® control unit  55  controls transmission of the AV signal, exchange of the control signal, and the like by the HDMI® transmission unit  54 . 
     The user interface (U/I) control unit  56  receives an operation signal corresponding to an operation by the user from a remote control (not shown) which remotely controls the AV amplifier  25 . Also, the U/I control unit  56  receives an operation signal input by the user through operation of an operation button or the like provided to an operation panel (not shown) of the AV amplifier  25 . Then, the U/I control unit  56  supplies the received operation signal to the CPU  51 . 
     The audio input unit  57  includes an interface (for example, RCA interface or optical digital interface) for inputting an audio signal in a format different from the HDMI® format and outputs the input audio signal to the bus. 
     The image input unit  58  includes an interface (for example, RCA interface or analog component interface) for inputting an image signal in a format different from the HDMI® format and outputs the input image signal to the bus. 
     The image processing unit  59  performs predetermined image processing on the image signal output to the bus from the image input unit  58  or the image signal of an AV signal output to the bus by the HDMI® control unit  62 , and outputs the image signal to the bus. 
     The audio processing unit  60  performs encoding, decoding, a sampling process, or other processing on the audio signal output to the bus from the audio input unit  57  or the audio signal of the AV signal output to the bus by the HDMI® control unit  62 , and outputs the audio signal to the bus. 
     The audio drive unit  61  drives the speaker  63  in response to the audio signal on the bus. 
     According to the control by the CPU  51 , the HDMI® control unit  62  controls reception of an AV signal, exchange of a control signal, and the like by the HDMI® reception unit  64 . 
     The speaker  63  is driven by the audio drive unit  61  to output audio. Note that although the speaker  63  is provided outside the AV amplifier  25  in  FIG. 4 , the speaker  63  may be built in the AV amplifier  25 . 
     According to a control by the HDMI® control unit  62 , the HDMI® reception unit  64  receives the AV signal transmitted from the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , or the STB  24  via the cables  31  to (see  FIG. 2 ) and causes the control signal to be exchanged (relayed) among the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24 . 
     With the AV amplifier  25  configured in a manner described above, the HDMI® source connected to the HDMI® input terminals IN1 to IN4 is recognized within the primary cluster through communication according to the HDMI® specification. For example, the reproducing device  23  connected to the HDMI® input terminal IN3 is recognized within the primary cluster. 
     Then, the CPU  51  performs a control of notifying the HDMI® sink within the secondary cluster of a function of the HDMI® source recognized within the primary cluster as a function (device) belonging to the CPU  51 . For example, the CPU  51  performs a control of notifying the projector  27  within the secondary cluster as if a reproducing function of the reproducing device  23  belongs to the CPU  51 . As a result, the HDMI® sink within the secondary cluster can recognize the HDMI® source as a device (function) belonging to the HDMI® repeater. 
     Accordingly, for example, the projector  27  within the secondary cluster can output an operation command for the reproducing function of the device (function) apparently belonging to the AV amplifier  25 . When a command with respect to the reproducing function within the secondary cluster is supplied, the CPU  51  of the AV amplifier  25  performs a conversion and outputs a command with respect to the reproducing device  23  within the primary cluster which corresponds to the reproducing function. It appears to the user as if the projector  27  is recognizing the reproducing device  23 , and the operation of the reproducing device  23  can be controlled from the projector  27 . 
     [Address Acquisition Process within the Primary Cluster when the Reproducing Device  23  is Connected] 
     A process of acquiring an address within the primary cluster when the reproducing device  23  is connected to the HDMI® input terminal IN3 of the AV amplifier  25  with the cable  33  is described with reference to a flowchart in  FIG. 5 . Note that the game console  21 , the recording/reproducing device  22 , and the TV  26  are connected to the AV amplifier  25  respectively with the cables  31 ,  32 , and  35  before the process in  FIG. 5  is started. 
     An HDMI® cable includes multiple signal lines. Signal lines relating to acquisition of an address are +5V power line, hot plug detect (HPD) line, and DDC line. When the reproducing device  23  is connected to HDMI® input terminal IN3 of the AV amplifier  25  with the cable  33 , the reproducing device  23  supplies a power supply of +5 V from the +5V power line to the AV amplifier  25  via the cable  33  in step S 11 . 
     In step S 12 , the AV amplifier  25  recognizes the connection of the HDMI® device (herein, the reproducing device  23 ) to the HDMI® input terminal IN3 by detecting that the power supply of +5 V has been supplied to a +5V power terminal of the HDMI® input terminal IN3. 
     In step S 13 , the AV amplifier  25  prepares to provide EDID of the AV amplifier  25  to the reproducing device  23  and, once preparation is completed, causes a signal of an HPD line to shift from low (L) level to high (H) level. 
     In step S 14 , the reproducing device  23  detects that the signal of the HPD line has shifted to high (H) level and acquires the EDID of the AV amplifier  25  via the DDC line. 
     In step S 15 , the reproducing device  23  acquires the physical address (1.3.0.0) of the reproducing device  23  from a source physical address field of the acquired EDID and also recognizes the physical address (1.0.0.0) of the AV amplifier  25  as a destination. 
     In step S 16 , the reproducing device  23  transmits a &lt;Polling Message&gt; command for the logical address “8” intended for acquisition and waits a predetermined period of time for a reply (Ack) with respect to the command. If another HDMI® device has already acquired the logical address “8”, there is a reply (Ack) with respect to the &lt;Polling Message&gt; command for the logical address “8”. 
     After the predetermined period of time has passed from transmission of the &lt;Polling Message&gt; for the logical address “8” in a state without a reply, the reproducing device  23  acquires the logical address “8” in step S 17 . Then, in step S 18 , the reproducing device  23  broadcasts (transmits) a &lt;Report Physical Address&gt; message. 
     In step S 19 , the AV amplifier  25  acquires the physical address (1.3.0.0) and the logical address “8” of the connected reproducing device  23 . Since the transmission is made through broadcasting, all of the HDMI® devices other than the AV amplifier  25  within the primary cluster also acquire the physical address (1.3.0.0) and the logical address “8” of the reproducing device  23 . 
     In a manner described above, the physical address and the logical address are acquired when the reproducing device  23  is connected to the AV amplifier  25 , and all of the HDMI® devices within the primary cluster also recognize the acquisition. 
     Note that transmission of a &lt;Polling Message&gt; command for the logical address “4” and reception of a reply thereto by the reproducing device  23  are omitted in a sequence in  FIG. 5 . That is, the reproducing device  23  first transmits the &lt;Polling Message&gt; command for the logical address “4” as a logical address intended for acquisition and receives a reply from the game console  21  belonging to the same device type of “playback device”. Accordingly, it is determined that the logical address “4” is already in use, and the &lt;Polling Message&gt; command for the next logical address “8” is transmitted. However, in  FIG. 5 , the transmission of the &lt;Polling Message&gt; command for the logical address “4” and the reception of the reply thereto are omitted. 
     [Address Acquisition Process within the Secondary Cluster when the Reproducing Device  23  is Connected] 
     Next, a process of acquiring within the secondary cluster an address corresponding to an HDMI® device upstream of the AV amplifier  25  when the reproducing device  23  is connected to the HDMI® input terminal IN3 of the AV amplifier with the cable  33  is described with reference to a flowchart in  FIG. 6 . 
     First, in step S 21 , the AV amplifier  25  recognizes the reproducing device  23  within the primary cluster. A process in step S 21  is specifically the process in  FIG. 5  in which the AV amplifier  25  recognizes that the reproducing device  23  with the physical address (1.3.0.0) and the logical address “8” exists within the primary cluster. 
     In step S 22 , the AV amplifier  25  transmits the function of the reproducing device  23  within the primary cluster as the function of the AV amplifier  25  to the projector  27  within the secondary cluster. That is, in a similar manner to a process in step S 16  in  FIG. 5  which is performed by the reproducing device  23  within the primary cluster, the AV amplifier  25  transmits the &lt;Polling Message&gt; command for the logical address “8” within the secondary cluster and waits a predetermined period of time for a reply with respect to the command. 
     After the predetermined period of time has passed from transmission of the &lt;Polling Message&gt; for the logical address “8”, the AV amplifier  25  acquires the logical address “8” within the secondary cluster in step S 23  and broadcasts the &lt;Report Physical Address&gt; message in step S 24 . 
     In step S 25 , the projector  27  recognizes “8” additionally as the logical address of the AV amplifier  25 . 
     Through the process described above, the AV amplifier  25  acquires the original logical address “5” of the AV amplifier  25  and the logical address “8” within the secondary cluster. Since the process similar to that in  FIG. 6  is performed for each of the game console  21 , the recording/reproducing device  22 , and the STB  24 , the AV amplifier  25  also acquires the logical addresses “4”, “1”, and “3” within the secondary cluster. 
     [Logical Address within the Secondary Cluster] 
       FIG. 7  shows the logical address set in the secondary cluster through the process described with reference to  FIG. 6 . 
     The projector  27  within the secondary cluster does not recognize the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24  within the primary cluster. Instead, it appears to the projector  27  as if the AV amplifier  25  has functions of the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24 . That is, the projector  27  recognizes the AV amplifier  25  as a device having all functions corresponding to the logical addresses “5” (audio system), “4” (playback device 1), “1” (recording device), “8” (playback device 2), and “3” (tuner). A function of the HDMI® source upstream of the AV amplifier  25  within the primary cluster which actually does not belong to the AV amplifier  25  is called a virtual device, and the logical address of the virtual device is referred to as a virtual logical address in this specification. 
     [Process when the Projector  27  Gives a Command for Reproduction to the Reproducing Device  23 ] 
     The projector  27  can recognize the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24  within the primary cluster, which are not recognized with the standard HDMI® specification, as virtual devices. By performing the CEC control with respect to the virtual devices with the projector  27 , the CEC control with respect to the game console  21 , the recording/reproducing device  22 , the reproducing device  23 , and the STB  24  from the projector  27  is made possible. 
     A process when the reproducing device  23  is caused to reproduce contents through a user interface of the projector  27  is described with reference to a flowchart in  FIG. 8 . 
     The user makes an instruction for reproduction by the reproducing device  23  as the virtual device through the user interface of the projector  27 . For example, “play with the reproducing device  23 ” is selected in a screen on the projector  27  through operation of an operation button of the remote control  27 R of the projector  27 . 
     When reproduction by the reproducing device  23  as the virtual device is instructed by the user, the projector  27  accepts a reproducing operation for the reproducing device  23  as the virtual device in step S 31 . Then, in step S 32 , the projector  27  transmits a command for reproduction to the AV amplifier  25 . Specifically, a &lt;Play&gt; [“Forward”] command with respect to the virtual logical address “8” of the AV amplifier is transmitted from the projector  27  to the AV amplifier  25 . 
     In step S 33 , the AV amplifier  25  converts the virtual logical address “8” of the received &lt;Play&gt;[“Forward”] command to the physical address and the logical address of the corresponding HDMI® device within the primary cluster. That is, the AV amplifier  25  converts the virtual logical address “8” within the secondary cluster to the physical address (1.3.0.0) and the logical address “8” of the reproducing device  23 . 
     In step S 34 , the AV amplifier  25  determines whether an active source within the primary cluster is the reproducing device  23 . When it is determined that the active source is the reproducing device  23  in step S 34 , the process proceeds to step S 37  described later. 
     On the other hand, when it is determined that the active source is not the reproducing device  23  in step S 34 , the process proceeds to step S 35  in which the AV amplifier  25  designates the physical address (1.3.0.0) of the reproducing device  23  and broadcasts a &lt;Set Stream Path&gt; command. 
     In step S 36 , the reproducing device  23  designates the physical address (1.3.0.0) of the reproducing device  23  and broadcasts an &lt;Active Source&gt; command to show that the reproducing device  23  has become the active source. 
     Confirming that the reproducing device  23  has become the active source, the AV amplifier  25  transmits the &lt;Play&gt; [“Forward”] command to the reproducing device  23  in step S 37 . 
     In step S 38 , the reproducing device  23  returns a &lt;Deck Status&gt; [“Play”] message to the AV amplifier  25  to notify the AV amplifier  25  that reproduction has started. 
     In step S 39 , the AV amplifier  25  receives the &lt;Deck Status&gt; [“Play”] message and converts the physical address (1.3.0.0) and the logical address “8” of the reproducing device  23  to the virtual logical address “8” within the secondary cluster. 
     Then, in step S 40 , the AV amplifier  25  returns to the projector  27  the &lt;Deck Status&gt; [“Play”] message showing that the virtual device with the virtual logical address “8” of the AV amplifier  25  has started reproduction. 
     In  FIG. 8 , steps S 32  and S 40  show communication (CEC control) within the secondary cluster, and steps S 35  and S 38  show communication (CEC control) within the primary cluster. 
     In the AV amplifier  25 , the CPU  51  executes an address conversion between the primary cluster and the secondary cluster, selection of a transmission command, or the like, and the HDMI® transmission unit  54  and the HDMI® control unit  55  directly transmits or receives a command or message. 
     In a manner described above, the AV amplifier  25  which is the HDMI® repeater performs a conversion to obtain the address within the primary cluster and transmits the command from the projector  27  within the secondary cluster to the corresponding HDMI® device. Also, the AV amplifier  25  performs a conversion to obtain the virtual logical address within the secondary cluster and transmits to the projector  27  a response command with respect to the command transmitted to the corresponding HDMI® device within the primary cluster. In this manner, the AV amplifier  25  shows the HDMI® source within the primary cluster as the virtual device to the projector  27  (HDMI® sink) within the secondary cluster to enable control with respect to the HDMI® source within the primary cluster from the projector  27 . 
     In the example described above, the process of causing the reproducing device  23  to perform the reproducing operation from the user interface of the projector  27  has been described. However, a process other than the reproducing operation can be controlled in a similar manner, as long as an operation (command) of the process is started by the HDMI® sink within the secondary cluster. Note that a process of which an operation (command) is started by the HDMI® source, such as an operation generally called “One Touch Play” or “One Touch Record”, may be within a range of application. 
     As described with reference to  FIG. 6 , exchange of a command by the AV amplifier  25  using the CEC line within the secondary cluster suffices to enable control with respect to the HDMI® source within the primary cluster from the projector  27 . In other words, the HPD line and the DDC line are not used, and resetting or the like is not performed. Also, the EDID stored in the AV amplifier  25  is not changed. Since only 2 bytes are used for the logical address, resource can be saved. 
     Thus, when the HDMI® repeater includes two HDMI® outputs, the HDMI® sink not belonging to the primary cluster can control the HDMI® source within the primary cluster more easily than with a method of Japanese Unexamined Patent Application Publication No. 2008-153974 which involves resetting of HPD or operation of DDC. Accordingly, user-friendliness of the TV  26  and the projector  27  connected to the multiple HDMI® output terminals OUT1 and OUT2 can be improved. 
     The embodiment in which the HDMI® repeater includes the two HDMI® output terminals OUT1 and OUT2 has been described above. However, when the HDMI® repeater includes three or more HDMI® output terminals, three or more HDMI® sinks connected thereto can also be made to perform the CEC control in a similar manner. 
     Note that, in this specification, the steps described in the flowchart may be executed in parallel or at an appropriate timing, such as upon a call, to be processed chronologically in the stated order or otherwise. 
     Embodiments of the present invention are not limited to the embodiment described above, and various modifications are possible within the scope of the present invention.