Patent Publication Number: US-8982760-B2

Title: Sink device and wireless transmission system

Description:
TECHNICAL FIELD 
     The present invention relates to a sink device that receives and reproduces AV (audio visual) data transmitted through multicast wireless transmission from a source device, and a wireless transmission system made up of a plurality of the sink devices and the source device. 
     BACKGROUND ART 
     A wireless network represented by a wireless LAN (local area network) is conventionally used for data transmission between devices such as personal computers (PC). Such a wireless network can be constructed such that data is transmitted through multicast transmission from an access point to devices. 
     Patent Document 1 discloses a wireless transmission apparatus that wirelessly communicates with other communication stations within a wireless network. This wireless transmission apparatus includes a wireless processing means that transmits and receives a wireless signal, and a control means that sets a predetermined frame cycle received by the wireless processing means based on management information from surrounding communication stations, that defines a predetermined position within the prescribed frame cycle as a management information transmission area, that prescribes a plurality of slots in the management information transmission area to allow communication stations to transmit management information through one of the slots, that prescribes a portion of the slots as a new entry slot in advance, and that executes processing for involving a transmission source of a specific signal in a wireless network, when the specific signal is recognized at a predetermined new entry slot position. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Publication No. 4192328 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     A multicast transmission by radio is characterized by a transmission path configuration formed in a star shape centered on a transmitter and, therefore, even if an individual receiver is disconnected due to fluctuations of wireless environment, other receivers are not disconnected and are capable of communication. As a result, a multicast wireless transmission system may go into a situation with some receivers being disconnected and other receivers being capable of communication. 
     However, such a situation is problematic in the following utilization environment. In other words, if AV data such as video and audio are wirelessly multicast-transmitted from a source device (transmitter) such as a tuner device, the following problem occurs in such a utilization environment that combines functions of a plurality of receivers for AV viewing, such as displaying and reproducing video data in reception data by a receiver (sink device) having a video display function and outputting audio from audio data in the reception data by a receiver having an audio reproduction function. In the case of such a utilization environment, if some receivers are disconnected due to fluctuations of wireless environment, other receivers are not disconnected and are capable of communication and, as a result, a viewing environment unsatisfactory for a viewer is provided such that only audio or video is continuously reproduced because communications of some receivers are disconnected. 
     It is not desirable for a viewer that the receiver having the video display function continues display reproduction while audio output is stopped because the receiver having the audio reproduction function becomes unable to communicate. A similar situation may occur in a viewing environment including a receiver having a left audio reproduction function and a receiver having a right audio reproduction function when only one of the receivers is disconnected and audio output is stopped, for example. Since sound volume and sound balance are disrupted in this viewing environment, it is not desirable for a viewer to continue reproduction in such an unsatisfactory viewing environment. Although this unsatisfactory viewing environment can obviously be eliminated if a user performs a user operation such as powering off or adjusting output of all the receivers generally disposed at remote positions because wireless communication is performed, this is a very time-consuming effort. 
     To automatically correct such an unsatisfactory viewing environment with receivers (sink devices) without relying on the user operation, it is desired that a sink device comprehends wireless connection status of other sink devices. However, neither idea nor technique currently exists for giving a sink device the comprehension of the wireless connection status of other sink devices in the utilization environment described above. Neither idea nor technique exists for automatically correcting such an unsatisfactory viewing environment on the sink device side without relying on the user operation. 
     The technique described in Patent Document 1 is a technique for newly involving a communication station (receiver) in an existing wireless network and is not a technique capable of solving such problems. 
     The present invention was conceived in view of the situations and it is therefore an object of the present invention to provide a sink device capable of determining a wireless connection status of other sink devices that reproduce AV data from a source device when reproducing the AV data transmitted through the multicast wireless transmission from the same source device, and a wireless transmission system including the sink devices and the source device. 
     It is another object of the present invention to provide a sink device capable of performing reproduction in accordance with wireless connection status of other sink devices that reproduce AV data from a source device when reproducing the AV data transmitted through the multicast wireless transmission from the same source device, and a wireless transmission system including the sink devices and the source device. 
     Means for Solving the Problems 
     In order to solve the above problems, a first technical means of the present invention is a sink device comprising an AV receiving portion that receives AV data including video and/or audio output through multicast wireless transmission from a source device, the sink device further comprising a reproducing portion that extracts and reproduces AV data transmitted to the sink device from the AV data received by the AV receiving portion; and a device information receiving portion that wirelessly receives a portion or whole of sink device information managed in the source device, the sink device information being information correlating identification information for identifying a plurality of sink devices including the sink device with state information indicative of wireless connection status of the sink devices. 
     A second technical means is the sink device of the first technical means wherein the reproducing portion performs reproduction control in accordance with the state information about other sink devices received by the device information receiving portion. 
     A third technical means is the sink device of the second technical means wherein the reproducing portion adds AV data extracted as a reproduction object to perform reproduction in accordance with the state information about other sink devices received by the device information receiving portion. 
     A fourth technical means is the sink device of the second technical means wherein the reproducing portion adjusts a reproducing method of AV data of a reproduction object in accordance with the state information about other sink devices received by the device information receiving portion. 
     A fifth technical means is the sink device of the second technical means wherein the reproducing portion terminates reproduction in accordance with the state information about other sink devices received by the device information receiving portion. 
     A sixth technical means is the sink device of the second technical means wherein the sink device information is formed by further correlating type information indicative of types of sink devices with the identification information, and wherein the reproducing portion performs reproduction control depending on the state information and the type information about other sink devices received by the device information receiving portion as the reproduction control. 
     A seventh technical means is the sink device of the second technical means wherein the AV data includes at least multichannel audio data, wherein the sink device is an audio output device that performs audio output of audio data of a predetermined channel with the reproducing portion, wherein the sink device information is formed by further correlating type information indicative of types of sink devices with the identification information, wherein the type information includes channel information indicative of a channel of the audio output in case that the sink device is an audio output device, and wherein the reproducing portion performs reproduction control depending on the state information and the channel information about other audio output devices received by the device information receiving portion as the reproduction control. 
     An eighth technical means is the sink device of the first technical means wherein the sink device information is formed by further correlating control-command transmitted from other sink devices with the identification information. 
     A ninth technical means is the sink device of the second technical means further comprising a control-command transmitting portion that generates and wirelessly transmits to the source device control-command related to reproduction control to be performed by other sink devices concurrently with the reproduction control depending on the state information performed by the reproducing portion, wherein the sink device information is formed by further correlating the control-command for the other sink devices with the identification information. 
     A tenth technical means is the sink device of the second technical means wherein the sink device information is formed by further correlating control-command transmitted from other sink devices with the identification information, and wherein the reproducing portion performs reproduction in accordance with the control-command received by the device information receiving portion. 
     An eleventh technical means is the sink device of the tenth technical means wherein the reproducing portion performs reproduction in accordance with the control-command in preference to the reproduction control depending on the state information. 
     A twelfth technical means is the sink device of the first technical means wherein the sink device information has group identification information for identifying a group to which each sink device belongs correlated with the identification information. 
     A thirteenth technical means is the sink device of the second technical means wherein the sink device information is formed by further correlating group identification information for identifying a group to which each sink device belongs with the identification information, and the reproducing portion performs reproduction control in accordance with the state information of other sink devices belonging to the same group received by the device information receiving portion. 
     A fourteenth technical means is the sink device of the sixth or the seventh technical means wherein the sink device information is formed by further correlating group identification information for identifying a group to which each sink device belongs with the identification information, and the reproducing portion performs reproduction control in accordance with the state information and the type information of other sink devices belonging to the same group received by the device information receiving portion as the reproduction control. 
     A fifteenth technical means is a wireless transmission system comprising a plurality of sink devices of the first technical means, the wireless transmission system further comprising the source device. 
     Effect of the Invention 
     The present invention enables a sink device to determine wireless connection status of other sink devices that reproduce AV data from a source device when reproducing the AV data transmitted through the multicast wireless transmission from the same source device. 
     The present invention enables the sink device to perform reproduction in accordance with wireless connection status of other sink devices that reproduce AV data from a source device when reproducing the AV data transmitted through the multicast wireless transmission from the same source device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic of an exemplary configuration of a wireless transmission system according to one embodiment of the present invention. 
         FIG. 2  is a functional block diagram of one exemplary configuration of a source device in the wireless transmission system of  FIG. 1 . 
         FIG. 3  is a diagram of an example of a sink list managed in the source device of  FIG. 2 . 
         FIG. 4  is a diagram of an example of a format of a frame that is multicast-transmitted from the source device of  FIG. 2  to a sink device. 
         FIG. 5  is a diagram of an example of a format of a frame that is unicast-transmitted between the source device of  FIG. 2  and a sink device. 
         FIG. 6  is a functional block diagram of one exemplary configuration of a sink device in the wireless transmission system of  FIG. 1 . 
         FIG. 7  is a diagram of an example of an operation table set in the sink device of  FIG. 6 . 
         FIG. 8  is a diagram of an exemplary construction of the wireless transmission system of  FIG. 1 . 
         FIG. 9  is a flowchart for explaining an operational example of a front left speaker in the wireless transmission system of  FIG. 8 . 
         FIG. 10  is a diagram of another exemplary construction of the wireless transmission system of  FIG. 1 . 
         FIG. 11  is a flowchart for explaining an operational example of a TV in the wireless transmission system of  FIG. 10 . 
         FIG. 12  is a diagram of another exemplary construction of the wireless transmission system of  FIG. 1 . 
         FIG. 13  is a diagram of an example of a sink list managed by a source device in the wireless transmission system of  FIG. 12 . 
         FIG. 14  is a diagram of an example of a format of a frame that is multicast-transmitted to a sink device belonging to a certain group from a source device in the wireless transmission system of  FIG. 12 . 
         FIG. 15  is a flowchart for explaining an operational example of a front left speaker disposed in a bed room in the wireless transmission system of  FIG. 12 . 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
       FIG. 1  is a schematic of an exemplary configuration of a wireless transmission system according to one embodiment of the present invention. The wireless transmission system (hereinafter, this system) according to this embodiment is made up of a source device  1  and a plurality of sink devices  2   a ,  2   b , . . . (hereinafter, each described as “sink device  2 ”). 
     The source device  1  is a device that outputs AV data including video and/or audio through the multicast wireless transmission. The sink device  2  is configured to be capable of receiving the AV data from the source device  1 . Therefore, the sink device  2  includes an AV receiving portion that receives AV data transmitted through the multicast wireless transmission from the source device  1 . The sink device  2  also includes a reproducing portion that extracts and reproduces AV data transmitted to the sink device  2  out of AV data received by the AV receiving portion. 
     The AV receiving portion receives AV data transmitted through the multicast wireless transmission and extracts data to be reproduced by the reproducing portion of the sink device  2  (data corresponding to functions of the sink device  2 , for example, an audio output function and/or a video display function). The reproducing portion may be responsible for a portion of this extraction. Multichannel audio data is generally distributed (transmitted) as an audio stream for all the channels, and an audio output device extracts a distributed audio stream from AV data (e.g., including a video stream) regardless of where the audio output device is intended to be used and further extracts and reproduces audio data of a channel to be reproduced from the audio stream in many cases. Describing the simplest case of two left and right channels, the right speaker also acquires the audio data for the left speaker and subsequently extracts and reproduces only the right audio data. 
     The sink device  2  includes a device information receiving portion. The device information receiving portion wirelessly receives portion or whole of sink device information managed in the source device  1 . Receiving only a portion means that only the information necessary for the sink device  2  is received and, if the whole information is received, the necessary information may be extracted after the reception. With regard to a receiving method, for example, the source device  1  may be configured to wirelessly transmit the sink device information in multicast or unicast periodically or at the timing when any piece of the sink device information is changed, and the sink device  2  may be configured to wirelessly receive the sink device information. Alternatively, the sink device  2  and the source device  1  may be configured such that the sink device information is received in accordance with wireless data communication to the source device  1  (i.e., by periodically making a request through wireless communication to the source device  1  from the sink device  2 ). The device information receiving portion may be configured to share a portion of functions with the AV receiving portion. 
     The sink device information is information correlating identification information for identifying a plurality of the sink devices  2  including the sink device  2  of its own, type information indicative of types of the sink devices  2 , and state information indicative of the wireless connection status (wireless connection statuses) of the sink devices. 
     This system may use any processing methods for the addition and acquisition of the identification information, the type information, and the state information in the source device  1 . For example, if the device configuration of this system is preliminarily defined, the identification information and the type information may be registered in advance. Alternatively, in view of the versatility, the type information may be acquired from the sink devices  2  through wireless communication at the time of wireless connection, and sequence numbers may be allocated as the identification information in the order of acquisition of the type information. For the state information, the source device  1  may regularly perform wireless data communication with the sink devices  2  and a sink device  2  not returning a response may be determined as not being connected (being interrupted) out of all the sink devices  2 . Alternatively, the sink devices  2  may detect (determine) a reception status (reception level) of the multicast-transmitted AV data and wirelessly send the result to the source device  1 , and the source device  1  may determine that a sink device  2  is not connected when the reception level detection result thereof cannot be received. To anticipate and deal with occurrence of a reproduction failure in advance, the state information may be implemented as a reception status such as a reception level of data, an error rate of data, and SNR of a signal of reception data, or a state of a power-saving mode in a sink device, and, in the case of a mobile device, a device operation state causing a reproduction failure not related to wireless transmission such as remaining power of a battery and a load factor of an audio separating/combining portion  27 . 
     This sink device information may be stored as a sink list formed by listing correlated pieces of the information. The information may be stored in any form such as including the type information in the identification information or adding identification information that enables interpretation of type information, for example. Although the type information is included as a portion of the sink device information in this example, the type information itself may not be managed in the source device  1  in some employable forms depending on the type and the number of the sink devices  2  included in this system. 
     As described above, in this system, the source device  1  manages the information (sink list) that lists the information including the wireless connection status of a plurality of the sink devices  2  to which the multicast transmission is performed. Since the device information receiving portion can actively read or passively acquire a portion or whole of the sink list, the device information receiving portion may be considered as a means for comprehending (determining) status of other sink devices  2  linked to the source device  1 . 
     Therefore, when reproducing AV data transmitted through the multicast wireless transmission from the source device  1 , the sink device  2  of the present invention can determine and comprehend the wireless connection status of other sink devices that reproduce the AV data from the same source device  1 . 
     The wireless connection status of other sink devices comprehended in this way can be used for avoiding or restoring (correcting) an unsatisfactory viewing environment such as those generated when a portion of the sink devices is disconnected. 
     For such avoidance and correction, the reproducing portion performs the reproduction control depending on the state information of other sink devices received by the device information receiving portion. The reproducing portion performs the reproduction control such that the functions of the disconnected sink device  2  is compensated depending on the individual characteristics (functions) of all the connected sink devices  2  and the characteristics (functions) of the disconnected sink device  2  among them. For example, when the device information receiving portion receives the state information of other sink devices, if the state information of any other sink device  2  indicates the wireless disconnection sate, the current reproduction control is changed to complement the termination of output of the sink device in the wireless connection status or to coordinate with the termination of the output so as to avoid or correct an unsatisfactory viewing environment. On the other hand, if the state information of all the other sink devices indicates being in wireless communication (favorable sensitivity), the current reproduction control is continued without change. 
     Describing the simplest example, in a system made up of a music player (source device) and left and right speakers (sink devices), if the right speaker detects that the communication with the left speaker is disconnected based on a sink list in the music player, the right speaker reproduces not only the normal right-speaker audio data but also the left-speaker audio data in a combined manner or reproduces the right-speaker audio data with an increased sound volume. 
     As described above, by performing the reproduction control depending on the state information in the sink device  2  (e.g., sink device  2   a ), when AV data transmitted from the source device  1  through the multicast wireless transmission is reproduced, the reproduction can be performed in accordance with the wireless connection status of other sink devices  2  (e.g., sink devices other than the sink device  2   a ) that reproduce the AV data from the same source device  1 . 
     In this system, the source device  1  does not have the control right of the reproduction control. If the control right is given to the source device  1 , the control of the source device  1  is complicated since all the functions of a plurality of the sink devices  2  must be comprehended and the functions of the sink devices  2  added later must also be implemented in advance in the source device  1 , which makes mounting on an actual product difficult. It also becomes necessary for a company selling the source device  1  to publish the sink list of the sink devices  2  belonging to the source device  1  to the outside for other companies that develop the sink devices  2 . Such problems do not occur in this system. However, implementation of a source device including functions of sink devices is conceivable, such as a television having a video reproduction device for Blu-ray discs etc., or a source device having a function of directly receiving a control signal from a remote controller. 
     Various examples will hereinafter be described for the reproduction control performed by the reproducing portion in accordance with the state information with reference to one specific exemplary configuration related to the source device  1  and the sink device  2 . 
       FIG. 2  is a functional block diagram of one exemplary configuration of a source device in the wireless transmission system of  FIG. 1 .  FIG. 3  is a diagram of an example of a sink list managed in the source device of  FIG. 2 ;  FIG. 4  is a diagram of an example of a format of a frame that is multicast-transmitted from the source device of  FIG. 2  to a sink device; and  FIG. 5  is a diagram of an example of a format of a frame that is unicast-transmitted between the source device of  FIG. 2  and a sink device. 
     The source device exemplarily illustrated in  FIG. 2  includes a sink list managing portion  11 , a video audio generating portion  12 , a wireless communication control portion  13 , a transmission data combining portion  14 , a reception signal data demodulating portion  15 , a transmission data signal modulating portion  16 , an analogue signal processing portion  17 , and an antenna  18 . 
     The video audio generating portion  12  generates video/audio data. If the source device  1  is STB (set top box), a recorder, etc., having a tuner portion connected to a broadcast reception antenna or a broadcast reception cable, the video audio generating portion  12  may be configured to perform demodulation, decoding, etc., of received broadcast signals. If the source device  1  is a recorder, a player, etc., the video audio generating portion  12  may be configured to read video/audio data from a recording location, for example, and to perform decoding etc., as needed. 
     The video audio generating portion  12  receives control data (such as a control-command for reproduction, pause, etc.) from the sink device  2  via the wireless communication control portion  13  and performs operations corresponding to the control data. If the sink device  2  is TV etc., the control-command may be a command transmitted from TV based on a CEC (Consumer Electronics Control) command in the HDMI (High-Definition Multimedia Interface) standard. 
     The wireless communication control portion  13  controls wireless communication. The wireless communication control portion  13  performs generation/transmission and reception/determination of communication management data related to the wireless communication and performs processing/control for establishing the network configuration and the wireless communication. The wireless communication control portion  13  also performs transmission management of control data that must certainly be transferred (such as management of retransmission processing). 
     The sink list managing portion  11  stores and manages the sink list, which is a list of the sink devices  2 . For example, the sink list managing portion  11  acquires information indicative of the communication status of the sink devices  2  from the wireless communication control portion  13  and retains the wireless connection status of the sink devices  2  as the sink list. The sink list managing portion  11  provides the wireless communication control portion  13  with a portion or whole of the sink list distributed to the sink devices  2 . 
     A sink list  11   a  exemplarily illustrated in  FIG. 3  retains sink device identification IDs, sink device types (such as television, monitor, audio amplifier, Lch speaker, and Rch speaker), and wireless connection status (favorable/disconnected) as respective data item examples of the identification information, the type information, and the state information. 
     The transmission data combining portion  14  combines the video/audio data with the control data and the communication management data received from the wireless communication control portion  13  and gives the data to the transmission data signal modulating portion  16 . The transmission data signal modulating portion  16  gives modulation processing to the transmission data, generates a transmission digital waveform signal to give it to the analogue signal processing portion  17 . The analogue signal processing portion  17  performs mutual conversion between a digital waveform signal and an analog waveform signal. The antenna  18  transmits/receives electric waves to/from the sink devices  2 . The reception signal data demodulating portion  15  demodulates the control data and the communication management data from the reception digital waveform signal subjected to the A/D conversion by the analogue signal processing portion  17  and gives the data to the wireless communication control portion  13 . 
     A transmission frame  40  exemplarily illustrated in  FIG. 4  is a frame that is multicast-transmitted from the antenna  18  (frame of multicast data packet) for video/audio transmission. The transmission frame  40  is made up of fields such as frame identification information  41 , stream identification information  42 , a transmission source address  43 , sequence number information  44 , and transmission data  45 . The transmission data  45  includes sink list controls  1  to n, an error detection code, and video/audio data. 
     The frame identification information  41  is information specifying a type of data. Since only three types of data exist in the examples described herein ( FIG. 4  and  FIGS. 5 and 14  described later), it is sufficient if the frame identification information  41  can distinguish three types; however, the identification information is generally distinguished in accordance with a purpose of control (such as data communication, management, band reservation, and acknowledgement) in wireless LAN, for example. 
     The stream identification information  42  is identification information for identifying video/audio data. The stream identification information  42  is useful when one source device  1  sends a plurality of streams. The transmission source address  43  indicates the address of the source device  1  that is the transmission source. Although the sequence number information  44  can be used for determining duplication in the case of communication including retransmission processing or used by a receiver (the sink device  2 ) for detecting that a number is skipped in the case of communication not including retransmission processing, it is no problem that the sequence number information  44  is not included in the frame format. 
     The sink list controls  1  to n include the sink device types and the wireless communication states corresponding to the sink device identification IDs (1 to n) of the sink list, and a control-command for concurrently controlling the sink devices  2 . Each of the sink devices  2  may extract the state information (wireless connection state) of the sink devices  2  changed in the reproduction control depending on the wireless connection status of other sink devices  2  (the sink devices of the types changed the reproduction control). This control-command and processing example using the control-command will be described later. 
     The error detection code is data for determining whether transmission data has an error, such as CRC (cyclic redundancy check). The video/audio data includes data of video and data of audio. Each of the sink devices  2  may extract data necessary for reproduction, for example, audio data from the video/audio data. 
     A transmission frame  50  exemplarily illustrated in  FIG. 5  is a frame unicast-transmitted from the source device  1  or the sink device  2  (frame of unicast data packet) for transmission of control data and communication control data. The transmission frame  50  is made up of fields such as frame identification information  51 , a reception destination address  52 , a transmission source address  53 , sequence number information  54 , control/state-information/communication control data  55 , and an error detection code  56 . 
     The frame identification information  51 , the transmission source address  53 , the sequence number information  54 , and the error detection code  56  are as described with the transmission frame  40  of  FIG. 4 . Since the transmission frame  50  is a frame for the unicast transmission and is available for retransmission, the sequence number information  54  is necessary. The reception destination address  52  indicates an address of a terminal on the reception side (the sink device  2  when the source device  1  is on the transmission side or the source device  1  when the sink device  2  is on the transmission side). The control/state-information/communication control data  55  includes control data, information of the wireless connection status of the sink device  2  supplied to the source device  1  (when the sink device  2  is on the transmission side), and communication control data (communication control data is necessary if management of network formation etc., are performed). 
       FIG. 6  is a functional block diagram of one exemplary configuration of a sink device in the wireless transmission system of  FIG. 1  and  FIG. 7  is a diagram of an example of an operation table set in the sink device of  FIG. 6 . 
     The sink device  2  exemplarily illustrated in  FIG. 6  includes an antenna  21 , an analogue signal processing portion  22 , a reception signal data demodulating portion  23 , a transmission data signal modulating portion  24 , a reception data separating portion  25 , a wireless communication control portion  26 , an audio separating/combining portion  27 , a sink operation control portion  28 , a setup information storage portion  29 , an audio output portion  30 , and an operation input portion  31 . The AV receiving portion can exemplarily be illustrated by the elements  21 ,  22 ,  23 ,  24 ,  27 ,  28 , etc.; the device information receiving portion can exemplarily be illustrated by the elements  21  to  23 ,  25 ,  26 ,  28 , etc.; and the reproducing portion can exemplarily be illustrated by the elements  27  to  30 , etc. 
     The antenna  21  transmits/receives electric waves to/from the source device  1 . The analogue signal processing portion  22  performs mutual conversion between a digital waveform signal and an analog waveform signal. The reception signal data demodulating portion  23  demodulates reception data from the reception digital waveform signal subjected to the A/D conversion by the analogue signal processing portion  22  and gives the reception data to the reception data separating portion  25 . The reception data separating portion  25  separates the video/audio data as well as the control data and the communication management data from the reception data and gives the video/audio data to the audio separating/combining portion  27  and the control data and the communication management data to the wireless communication control portion  26 . 
     The wireless communication control portion  26  controls wireless communication. The wireless communication control portion  26  performs generation/transmission and reception/determination of communication management data related to the wireless communication and performs processing/control for establishing the network configuration and the wireless communication. The wireless communication control portion  26  also performs transmission management of control data that must certainly be transferred (such as management of retransmission processing). In the case of the configuration of sending the state information to the source device  1 , the wireless communication control portion  26  generates and wirelessly transmits information of the communication state of the sink device  2  to be registered in the sink list in the source device  1 . 
     The audio separating/combining portion  27  takes out data corresponding to its own role (such as L/R and rear/front of speakers) from the audio/video data and gives the data to the audio output portion  30 . The audio separating/combining portion  27  performs the audio combining, the sound volume adjustment, etc., in accordance with instructions from the sink operation control portion  28  described later. 
     The audio output portion  30  outputs audio. Although an audio reproducing device is described as the sink device  2  in this example, the sink device  2  includes a video output portion (video displaying portion) instead of the audio output portion  30  in the case of a video reproducing device such as a monitor and includes a video output portion (video displaying portion) together with the audio output portion  30  in the case of a video audio reproducing device such as a TV. 
     The operation input portion  31  receives control data (such as control-command for reproduction, pause, etc.) from a user, etc. The control-command may be a command transmitted from the source device  1  based on a CEC (Consumer Electronics Control) command in the HDMI (High-Definition Multimedia Interface) standard. 
     The transmission data signal modulating portion  24  gives modulation processing to the control data and the communication management data and generates a transmission digital waveform signal and gives it to the analogue signal processing portion  22  and transmits electric waves through the antenna  21 . 
     The sink operation control portion  28  instructs an operation of the sink device  2  of its own in accordance with a sink device type and the wireless connection status received as a portion or whole of the sink list from the source device  1 , the setup information set as operations corresponding thereto in advance, and the control data (received as an intra-sink-list control-command described later) from the operation input portion  31 . The setup information storage portion  29  stores the role of the sink device  2  of its own, the corresponding operations, and the conditions of performing the corresponding operations. 
     The operations may be stored as an operation table  29   a  exemplarily illustrated in  FIG. 7 , for example. The operation table  29   a  is an example of the operation table when this system is a wireless home theater system equipped with a tuner device as the source device  1 , a monitor or TV, a right speaker device, a left speaker device, and an audio amplifier as the sink devices  2  and the operation table is stored in the setup information storage portion  29  of the left speaker device. The audio amplifier is disposed stand-alone as a front speaker or disposed along with another speaker device wired to the audio amplifier. The sink devices other than the left speaker device may normally retain operation tables different from the operation table  29   a  corresponding to the operations of the sink devices in the setup information storage portions  29  thereof. It is also conceivable to configure the operation table such that a common operation table having descriptions encompassing the operations of all the sink devices is set for all the sink devices without setting different operation tables to determine the corresponding operations in accordance with information on the roles of the sink devices in the setup information storage portions. 
     The sink operation control portion  28  of the left speaker device determines a type of sink device (sink device other than the left speaker device) entailing a change in its own operation at the time of disconnection from the operation table  29   a , acquires the wireless connection status of the type from the sink list, and controls the portions to perform the operation defined in the operation table  29   a  depending on the disconnected sink device. The priority order may be added to the operation table  29   a  or the operation table  29   a  may be described in the order of priority to perform the determination/reproduction control based on the priority order. 
     In this example, if the monitor or TV (monitor+center speaker) is disconnected, audio output is controlled to stop only when the other monitors are also disconnected. When the monitor/TV is not disconnected, it is determined whether the right speaker device is disconnected and, if disconnected, the audio for the right speaker is combined and output with the audio for the left speaker, which is normally reproduced by the left speaker device. In this case, since one speaker cannot cover the same sound volume level, a sound volume level may be increased. Similarly, when the monitor/TV is not disconnected, it is determined whether the audio amplifier is disconnected and, if disconnected, the reproduction is performed with an increased sound volume level (in this case, the right speaker device also increase a sound volume level through the same control). In the case of the disconnection of the audio amplifier, the operation may also be set such that the audio for the audio amplifier is combined and output with the audio for the left speaker, which is normally reproduced by the left speaker device. 
     As exemplarily illustrated by the reproduction control in the left speaker device at the time of disconnection of the right speaker device, the reproducing portion preferably performs the reproduction control depending on the type information and the state information by adding and reproducing the AV data extracted as a reproduction object, in accordance with the type information and the state information of other sink devices received by the device information receiving portion. 
     As exemplarily illustrated by the reproduction control in the left speaker device at the time of disconnection of the right speaker device, the reproducing portion performs the reproduction control depending on the type information and the state information by adjusting a reproducing method of the AV data to be reproduced, in accordance with the type information and the state information of other sink devices  2  received by the device information receiving portion. The reproducing method represents a reproduction level (output level, which is a sound volume level in this example) and a reproduction balance disrupted due to disconnection of other sink devices  2 . To adjust the reproduction balance, preferably, AV data extracted as a reproduction object is added as described above. 
     As exemplarily illustrated by the reproduction control in the left speaker device at the time of disconnection of the monitor/TV, the reproducing portion performs the reproduction control depending on the type information and the state information by terminating the reproduction, in accordance with the type information and the state information of other sink devices  2  received by the device information receiving portion. Although this termination can be performed along with the adjustment of the reproducing method and the addition of AV data extracted as a reproduction object as described above, the termination may not be performed if the disconnected source device  2  is a device of the same type (determinable from the type information) and the termination may be prioritized if all the devices of a different type are disconnected, depending on the type (video type/audio type) of the sink device  2 . 
     If a portion of the sink devices  2  is in the wireless connection status and all the sink devices  2  do not perform reproduction due to the action of the termination, the source device  1  may also terminate the multicast wireless transmission of AV data and resume the transmission after a predetermined time period. 
     Although the example described above and other examples described later are basically described on the basis that the reproducing portion performs the reproduction control depending on the type information and the state information, the type information may not be referenced or used. For example, since all the sink devices are limited to speaker devices and amplifier devices in the case of a music player etc., and since the availability of its own communication can be comprehended from the fact that the sink list can be received and disconnection of another sink device can be comprehended if disconnection exists in the sink list, the reproduction control depending on the state information (e.g., simply increasing a sound volume level) can be performed without problems. 
       FIG. 8  is a diagram of an exemplary construction of the wireless transmission system of  FIG. 1  and  FIG. 9  is a flowchart for explaining an operational example of a front left speaker in the wireless transmission system of  FIG. 8 . The system of  FIG. 8  is constructed of a tuner  71  and a sink device group consisting of a monitor  72  (ID:  0001 ), a front left speaker device  73  (ID:  0002 ), a front right speaker device  74  (ID:  0003 ), a rear left speaker device  75  (ID:  0004 ), a rear right speaker device  76  (ID:  0005 ), and an audio amplifier  78  (ID:  0006 ). If all the sink devices favorably communicate, a surround system can be made up of the speaker devices  73  to  76  and the audio amplifier  78 . The IDs represent correlation with sink device identification IDs in a sink list. 
     If wireless transmission is disconnected between one of the surround speakers, for example, the front right speaker device  74  and the tuner  71  due to radio disturbance in this system, other surround speaker devices  73 ,  75 ,  76 , and  78  comprehend the wireless disconnection status of the front right speaker device  74  from the sink list of the source device  1  and automatically adjust a sound balance and a sound volume level to compensate the absence of the front right speaker device  74 . 
     Although an operation example of the front left speaker device  73  (for audio reproduction of the front left channel) will be mainly described, other sink devices also perform operations tailored to the functions of the devices in the same way. The following control is mainly performed by the sink operation control portion  28  of  FIG. 6  with reference to the setup information storage portion  29  in the speaker device  73 . 
     First, the front left speaker device  73  acquires the state information of sink devices of types having prescriptions of operations at the time of disconnection from an operation table like the operation table  29   a  of  FIG. 7  from the source device  1  (step S 1 ). In the case of this system, the operation table in the front left speaker device  73  is assumed to prescribe the operations related to the monitor and the audio amplifier in the operation table  29   a , the operation of increasing a sound volume level in combination with audio of a channel for a front right speaker device (the device  74 , which, however, is not particularly necessary to be recorded in the device  73  and can be determined from the type information of the sink list; the same applies to the following description) at the time of disconnection of the front right speaker device, and the operation of increasing a sound volume level in combination with audio of a channel for a rear left speaker device (corresponding to the device  75 ) at the time of disconnection of the rear left speaker device. It is assumed that the operation at the time of disconnection of a rear right speaker device (corresponding to the device  76 ) is not prescribed. 
     Following step S 1 , the speaker device  73  determines whether the monitor  72  is disconnected (step S 2 ), stops the audio output if YES (step S 3 ), and goes to step S 6  if NO. Following step S 3 , the speaker device  73  waits for the timing of the sink list acquisition and determines whether the connection of the monitor  72  recovers (restitutes) (step S 4 ), and resumes the audio output after waiting the recovery (step S 5 ). The processing of steps S 2  to S 5  can prevent an unsatisfactory viewing environment such as continuously outputting only audio while video is terminated due to radio disturbance. 
     Following step S 5 , the speaker device  73  determines whether the front right speaker device  74  is disconnected (step S 6 ) and, only in the case of YES, the speaker device  73  combines the audio of the front right channel for the speaker device  74  with the original audio of the front left channel and performs reproduction with an increased sound volume level (step S 7 ). The same operation is subsequently performed for the rear left speaker device  75  (steps S 8  and S 9 ). The speaker device  73  then determines whether the audio amplifier  78  is disconnected (step S 10 ) and, only in the case of YES, the speaker device  73  reproduces the original audio of the front left channel with an increased sound volume level (step S 11 ). 
     As described above, if a system uses AV data including multichannel audio data and includes sink devices that are audio output devices (speaker devices or amplifier devices or speaker devices attached to a monitor) performing the audio output of audio data of predetermined channels with the reproducing portions, the reproducing portions preferably perform the reproduction control depending on the state information and the channel information of the sink devices, which are other audio output devices, received by the device information receiving portions. In this case, it is assumed that the type information includes channel information indicative of channels of audio output for sink devices that are audio output devices among the sink devices. The processing of steps S 6  to S 11  can prevent the sound balance and the sound volume level from being extremely disrupted due to radio disturbance. The processing of steps S 6  to S 11  may basically be executed each time the sink list is acquired. The determination and the processing related to the recovery of the speaker devices  74  and  75  from disconnection will not be described. 
       FIG. 10  is a diagram of another exemplary construction of the wireless transmission system of  FIG. 1  and  FIG. 11  is a flowchart for explaining an operational example of a TV in the wireless transmission system of  FIG. 10 . In the system of  FIG. 10 , a TV  77  (ID:  0001 ) is disposed instead of the monitor  72  in the system of  FIG. 8 . The TV  77  has a monitor  77   a  and a center speaker  77   b . It is assumed that the center speaker  77   b  is set to be disabled. If all the sink devices favorably communicate, a surround system can be made up of the speaker devices  73  to  76  and the audio amplifier  78 . 
     If wireless transmission is disconnected between the audio amplifier  78  and the tuner  71  due to radio disturbance in this system, other surround speaker devices  73  to  76  comprehend the wireless disconnection status of the audio amplifier  78  from the sink list of the source device  1  and may automatically adjust a sound balance and a sound volume level to compensate the absence thereof. Such a control is as described in  FIGS. 8 and 9 . A control example of compensating the absence of the audio amplifier  78  only with the center speaker  77   b  will be described. The following control is mainly performed by the sink operation control portion  28  of  FIG. 6  with reference to the setup information storage portion  29  in the TV  77 . 
     First, the TV  77  acquires the state information of sink devices of types having prescriptions of operations at the time of disconnection from an operation table like the operation table  29   a  of  FIG. 7  from the source device  1  (step S 21 ). In the case of this system, the operation table in the TV  77  is assumed to prescribe the operation related to an audio amplifier (corresponding to the amplifier  78 ) and the respective operations for front left, front right, rear left, and rear right speaker devices. The former operation is an operation of outputting main audio from the center speaker  77   b  when the audio amplifier is disconnected. The latter operations are assumed to be operations of outputting audio from the center speaker  77   b  in combination with an audio channel of a disconnected speaker device if disconnected while the audio amplifier is disconnected. 
     Following step S 21 , the TV  77  determines whether the audio amplifier  78  is disconnected (step S 22 ), turns on the center speaker  77   b  to reproduce the main audio if YES (step S 23 ), and terminates the process if NO. As a result of the processing at steps S 21  to S 23 , if the wireless transmission is connected between the audio amplifier  78  and the tuner  71  due to radio disturbance, the TV  77  comprehends the wireless transmission status of the audio amplifier from the sink list of the tuner  71 , automatically enables a built-in speaker (the center speaker  77   b ), and performs audio output from the built-in speaker. This can prevent an unsatisfactory viewing environment such as the termination of the main audio due to radio disturbance. 
     Following step S 23 , the TV  77  determines whether any one of the front left, front right, rear left, and rear right speaker devices  73  to  76  is disconnected (step S 24 ), and combines and outputs the main audio with the audio of the audio channel of the disconnected speaker device from the center speaker  77   b  (step S 25 ). 
     Following step S 25 , the TV  77  waits for the timing of the sink list acquisition and determines whether the connection of the audio amplifier  78  recovers (restitutes) (step S 26 ). If the connection recovers, the TV  77  turns off the center speaker  77   b  (step S 27 ) and, if the connection does not recover, the TV  77  goes back to step S 24 . As described above, the processing of steps S 24  and S 25  is the processing executed only in the absence of the audio amplifier  78 . The processing of steps S 21  to S 27  may basically be executed each time the sink list is acquired. The determination and the process related to the recovery of the speaker devices  73  to  76  from disconnection will not be described. 
       FIG. 12  is a diagram of another exemplary construction of the wireless transmission system of  FIG. 1 .  FIG. 13  is a diagram of an example of a sink list managed by a source device in the wireless transmission system of  FIG. 12  and  FIG. 14  is a diagram of an example of a format of a frame that is multicast-transmitted to a sink device belonging to a certain group from a source device in the wireless transmission system of  FIG. 12 . 
     In this example, a system providing a plurality of sets of viewing environment from one source device will be described. A system exemplarily illustrated in  FIG. 12  is made up of the tuner  71  that is the source device and the sink devices  73  to  77  disposed in a living room  8   a , and sink devices  82  to  86  disposed in a bed room  8   b . The sink devices  73  to  77  of the living room  8   a  are the devices described in  FIG. 8  or  10  and the sink devices  82  to  86  of the bed room  8   b  are devices respectively corresponding to  72  to  76  of  FIG. 8 . 
     In the case of the system providing a plurality of sets of viewing environment from one source device  1  as described above, the sink device information preferably has the identification information and the state information (and the type information) correlated with group identification information. In other words, the sink device information is preferably managed for a plurality of groups each consisting of a plurality of sink devices such that a sink device can determine the wireless connection status of other sink devices. The group identification information is information for identifying a group to which each of the sink devices  2  belongs. As is the case with the separation into the living room  8   a  and the bed room  8   b  in  FIG. 12 , a plurality of sink devices fulfilling one function such as a plurality of surround speakers (a front left channel, a center channel, etc.) may be treated as one group, for example. 
     The sink list  11   b  exemplarily illustrated in  FIG. 13  is managed by the sink list managing portion  11  as is the case with the sink list  11   a  of  FIG. 3  and retains sink device identification IDs, sink device types, wireless connection status, and group identification IDs as respective data item examples of the identification information, the type information, the state information, and the group identification information. A group ID of  FIG. 12  indicates a group of devices corresponding to the group identification ID in the sink list  11   b  of  FIG. 13 . 
     Although the sink list  11   b  including the group identification IDs as described above may be transmitted through the transmission frame  40  of  FIG. 4 , the sink list  11   b  is preferably transmitted through a frame for a certain group as exemplarily illustrated by a transmission frame  90  of  FIG. 14 . The transmission frame  90  is a frame that is multicast-transmitted for control/list notification to a certain group. The transmission frame  90  is made up of fields such as frame identification information  91 , reception group identification information  92 , a transmission source address  93 , sequence number information  94 , control/sink-list/communication control data  95 , and an error detection code  96 . 
     The frame identification information  91 , the transmission source address  93 , the sequence number information  94 , and the error detection code  96  are as described with respect to the transmission frame  40  of  FIG. 4 . The reception group identification information  92  is information specifying a receiving group. A sink device receives the subsequent fields of the transmission frame  90  based on this information if identical to its own group. The control/sink-list/communication control data  95  includes control data, a sink list (including the state information), and communication control data (communication control data is necessary if management of network formation etc., are performed). This sink list is a sink list for the sink devices  2  belonging to the certain group. 
     In such a system, the reproducing portion also performs the reproduction control depending on the state information (and the type information and the channel information). However, for example, the living room  8   a  and the bed room  8   b  respectively form separate viewing environments in such a grouped system and, therefore, the reproducing portion preferably performs the reproduction control in accordance with the state information (and the type information and the channel information) of other sink devices belonging to the same group received by the device information receiving portion. When the sink devices operate in an interlocking manner in each viewing environment of a plurality of different viewing environments, a failure of one viewing environment can be prevented from affecting the other viewing environment. 
       FIG. 15  is a flowchart for explaining an operational example of the front left speaker disposed in the bed room in the wireless transmission system of  FIG. 12 . Although an operation example of the front left speaker device  83  of the group identification ID  0002  (in the bed room  8   b ) will be mainly described with reference to  FIG. 15 , other sink devices belonging to the same group also perform operations tailored to the functions of the devices in the same way. Other sink devices belonging to another group (in the living room  8   a ) operate independently of the sink devices of this group (in the bed room  8   b ). The following control is mainly performed by the sink operation control portion  28  of  FIG. 6  with reference to the setup information storage portion  29  in the speaker device  83 . 
     First, the front left speaker device  83  acquires the state information of sink devices having the group identification ID same as the front left speaker device  83  among other sink devices of types having prescriptions of operations at the time of disconnection from an operation table like the operation table  29   a  of  FIG. 7  from the source device  1  (step S 31 ). In the case of this system, the operation table in the front left speaker device  83  is assumed to prescribe the operation related to the monitor in the operation table  29   a , the operation of increasing a sound volume level in combination with audio of a channel for a front right speaker device (corresponding to the device  84 ) at the time of disconnection of the front right speaker device, and the operation of increasing a sound volume level in combination with audio of a channel for a rear left speaker device (corresponding to the device  75 ) at the time of disconnection of the rear left speaker device. Although the operations at the time of disconnection are obviously not prescribed for the sink devices  73  to  77  of the different group, it is also assumed that the operation at the time of disconnection of a rear right speaker device (corresponding to the device  86 ) is not prescribed in the following description. 
     The front left speaker device  83  executes the similar processing to that of steps S 2  to S 9  of  FIG. 9  (steps S 32  to  39 ). However, the determination of disconnection at steps S 32 , S 34 , S 36 , and S 38  is made based on the state information for the group identification ID ( 0002 ) that is the same ID as that for the front left speaker device  83 . 
     An embodiment employing the control-command described in  FIG. 4  will be described with reference to  FIGS. 2 ,  3 ,  6 ,  7 , etc., as needed. This control-command may not be employed as can be seen from the examples described above, if employed, a plurality of sink devices can be controlled by one sink device (one sink device for each group if separated into groups). 
     The primary (master) sink device  2  in this form includes a control-command transmitting portion that generates control-command related to the reproduction control to be executed by other sink devices  2  (i.e., secondary sink devices  2 ) concurrently with the reproduction control depending on the state information etc., performed by the reproducing portion and that wirelessly transmits the control-command to the source device  1 . The control-commands corresponding to the sink device types may be stored in the setup information storage portion  29  in a correlated manner with the reproduction control depending on the state information, etc., (e.g., operations in the operation table  29   a  of  FIG. 7 ) and may be read out to generate the control-command. For example, the control-commands may be written next to the operations in the operation table  29   a . The control-commands are commands indicative of the contents to be actually executed by the secondary (slave) sink devices  2 , such as “reproducing with increased sound volume level”, “shifting to standby state”, or “returning from standby state”, for example. The control-command transmitting portion can exemplarily be illustrated by the elements  21 ,  22 ,  24 ,  26 ,  28 , and  29  of  FIG. 6 . 
     The source device  1  in this form includes a receiving portion that receives the control-command transmitted by the control-command transmitting portion of the master sink device  2 . This receiving portion can exemplarily be illustrated by the elements  18 ,  17 ,  15 ,  13 , etc., of  FIG. 2 . The source device  1  also includes a command registering portion that registers the control-commands for the sink devices received by the receiving portion as a portion of the sink device information (sink list) in a correlated manner with the identification information. The command registering portion can exemplarily be illustrated by the sink list managing portion  11  of  FIG. 2 . This enables the sink list managing portion  11  to manage a sink list including the control-commands for the slave sink devices  2 . 
     In a configuration where the control-commands of the master sink device are transmitted through direct wireless transfer to the slave sink devices, the control-commands may be implemented so as not to be included in the sink list if all the wireless connection status are favorable in the system. However, in general, although the communication status is good between a source device and a sink device in a star network, the communication status may not be good in the communication between sinks depending on arrangement and, therefore, the control-commands are more certainly transferred to the slave sink devices by the multicast transmission via the source device than by the transmission between sinks as in this system. Since the control-commands are included and registered in the sink list that is multicast-transmitted by the source device in this system, a sink device can acquire the control-commands at arbitrary timing by receiving the sink list and, therefore, if the multicast transmission including the control-commands is failed to be received once, the commands can be executed by subsequently acquiring the sink list. This is effective in the control-command specifying a state such as “standby/activation state”, “sound volume level”, etc. If the wireless connection state of the mater sink device  2  turns to disconnection, the command registering portion may exceptionally register a reproduction termination command as the control-command. The control of the slave sink devices  2  based on this reproduction termination command may simply be performed by terminating reproduction as described at step S 3  of  FIG. 9 . This enables the response to the disconnection of the master sink device  2 . 
     The reproducing portions of the slave sink devices  2  in this form may perform reproduction in accordance with the control-commands received by the device information receiving portions. For example, if the control-command is a command for increasing a sound volume level, the audio output devices among the slave sink devices  2  may increase a sound volume level in accordance with the control-command. It is particularly preferred that the reproducing portion performs the reproduction in accordance with the control-command in preference to the reproduction control depending on the state information etc. 
     The form related to the control-command is applicable regardless of whether the sink devices  2  are grouped. Particularly, if grouped, the control-commands can be stored for each group and, therefore, the control can be performed for each group. 
     If the wireless transmission system is constructed of the (basically one) master sink device, the (one or more) slave sink devices, and the source device retaining the control-commands in the sink list in this way, the master sink device can control the slave sink device. The slave sink devices can achieve the same more balanced control in view of the whole system by performing the reproduction control in accordance with the control-commands without directly performing the reproduction control depending on the state information etc., as described above. 
     Although the examples are described by reference to sink devices having disposition locations specified in advance such as a speaker device specified as a right speaker device, a type of each sink device may be registerable in the source device at the time of setup of the wireless communication (unicast wireless transmission) etc. 
     Although the operation from the state in which the operation table is already set is described, the operation table may be configured to be acquired through wireless transmission from the source device and the other sink devices at the activation of the sink device. 
     EXPLANATIONS OF REFERENCE NUMERALS 
       1  . . . source device;  2   a ,  2   b ,  2  . . . sink device;  11  . . . sink list managing portion;  11   a ,  11   b  . . . sink list;  12  . . . video audio generating portion;  13  . . . wireless communication control portion;  14  . . . transmission data combining portion;  15 ,  23  . . . reception signal data demodulating portion;  16 ,  24  . . . transmission data signal modulating portion;  17 ,  22  . . . analogue signal processing portion;  18 ,  21  . . . antenna;  25  . . . reception data separating portion;  26  . . . wireless communication control portion;  27  . . . audio separating/combining portion;  28  . . . sink operation control portion;  29  . . . setup information storage portion;  29   a  . . . operation table;  30  . . . audio output portion; and  31  . . . operation input portion.