Abstract:
A signal processing apparatus includes: a connecting means for use in connecting to a different device; a signal control means for changing a control signal to be outputted to the different device through the connecting means for a predetermined period; a changing means for changing the predetermined period; a determining means for determining for each of the predetermined periods changed by the changing means whether the different device stably makes a response to a change in the control signal caused by the signal control means; and a deciding means for deciding a shortest predetermined period from the predetermined periods determined by the determining means that the different device stably makes a response, as a standby time for the different device connected through the connecting means.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority from Japanese Patent Application No. JP 2008-192095 filed in the Japanese Patent Office on Jul. 25, 2008, the entire content of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a signal processing apparatus, a signal processing method, and a program, and particularly to a signal processing apparatus, which can control a different device in the optimum standby time, a signal processing method, and a program. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, as the interface standards used for connecting so-called digital electric home appliances to each other such as digital television sets, digital video cameras, digital video recorders, digital players, digital tuners, and home-use game machines, the HDMI (High-Definition Multimedia Interface) standard is widely used, and HDMI devices provided with a terminal in conformity with the HDMI standard are increasing. 
         [0006]    Hereinafter, among HDMI devices provided with a terminal in conformity with the HDMI standard, an HDMI device that supplies a content formed of video and sounds is called a source device such as a DVD (Digital Versatile Disc) player. In addition, an HDMI device that outputs a content fed from a source device is called a sink device such as a television set (the device that displays video and outputs sounds). 
         [0007]    In addition, between the source device and the sink device, control signals are sent and received for device authentication and various settings. For example, by a hot plug signal, the sink device notifies the source device that it is possible to read EDID (Extended Display Identification Data) including information such as the maximum resolution or color characteristics of a display, or that it is compliant with an HDCP (high-bandwidth Digital Content Protection) authentication process, which is one of copyright protection techniques. 
         [0008]    In the past, generally, when a plurality of source devices is connected to a sink device through HDMI terminals, a source device is selected (specified) so as to supply a content to the sink device, and turned into the selected state, whereas a source device, which is not selected to do so, is turned into the unselected state. Then, in the sink device, such control is conducted in which the hot plug signal of the HDMI terminal connected to the source device in the selected state is turned to high level, and the hot plug signal of the HDMI terminal connected to the source device in the unselected state is turned to low level. 
         [0009]    Some sink devices are mounted with a CEC (Consumer Electronics Control) function that is the function of controlling devices each other. For such sink devices, it is necessary to always keep all the hot plug signals of the HDMI terminals high in order to read EDID of the source device in the unselected state all the time. Then, in response to a user manipulation, for example, when the selection of the source device is switched, the sink device conducts such control (toggling) that the sink device turns the hot plug signal of the HDMI terminal to low level, waits for a predetermined period, and again turns the HDMI terminal to high level, the HDMI terminal being connected to the source device to be newly turned into the selected state. 
         [0010]    When the sink device conducts the toggling of the hot plug signal in this manner, in response to the toggling, the source device again conducts the HDCP authentication process to perform a process of recovering from the HDCP error state (reset). 
         [0011]    For example, in the HDMI standard, it is defined that when the hot plug signal continues the low state for a period of 100 milliseconds or longer, that is, when the low period (the period in which the sink device turns the hot plug signal to low level and waits) of the hot plug signal is 100 milliseconds or longer, the source device detects that the hot plug signal is turned to low level and responds to the detection. However, among source devices already available on the market, some of source devices can respond to the event that the hot plug signal is turned to low level after a much longer low period of the hot plug signal than a period of 100 milliseconds, that is, some source devices have a long response time. 
         [0012]    In order to keep compatibility with such source devices having a long response time, it is necessary to set the low period of the hot plug signal to a period of 100 milliseconds or longer as matched with the source device having a long response time. However, because all the source devices connected to the sink device do not always have a long response time, when the low period of the hot plug signal is set longer, the low period becomes unnecessarily longer depending on source devices. Therefore, a user has to wait for a longer time until a sink device outputs a content after the selection of a source device is switched. 
         [0013]    For example, Patent Document 1 describes a technique that uses a hot plug signal to detect the connection between HDMI devices. (See JP-A-2008-35060.) 
       SUMMARY OF THE INVENTION 
       [0014]    As described above, an unnecessarily long low period is sometimes set to sink devices before, and a user feels a poor response to manipulations at times. From this point, such a sink device is demanded that the sink device controls a source device in the optimum low period and has an excellent response to manipulations. 
         [0015]    Thus, it is desirable to allow control over a different device in the optimum standby time. 
         [0016]    According to an embodiment of the invention, there is provided a signal processing apparatus including: a connecting means for use in connecting to a different device; a signal control means for changing a control signal to be outputted to the different device through the connecting means for a predetermined period; a changing means for changing the predetermined period; a determining means for determining for each of the predetermined periods changed by the changing means whether the different device stably makes a response to a change in the control signal caused by the signal control means; and a deciding means for deciding a shortest predetermined period from the predetermined periods determined by the determining means that the different device stably makes a response, as a standby time for the different device connected through the connecting means. 
         [0017]    According to another embodiment of the invention, there is provided a signal processing method of a signal processing apparatus for processing a signal, including the steps of: by the signal processing apparatus, changing a control signal to be outputted to a different device through a connecting means for use in connecting to the different device for a predetermined period; changing the predetermined period; determining for each of the changed predetermined period whether the different device stably makes a response to a change in the control signal; and deciding a shortest predetermined period from the predetermined periods determined that the different device stably makes a response, as a standby time for the different device connected through the connecting means. 
         [0018]    According to still another embodiment of the invention, there is provided a program which allows a computer to function as a signal processing apparatus for processing a signal, including the functions of: a signal control means for changing a control signal to be outputted to the different device through a connecting means for use in connecting to a different device for a predetermined period; a changing means for changing the predetermined period; a determining means for determining for each of the predetermined periods changed by the changing means whether the different device stably makes a response to a change in the control signal caused by the signal control means; and a deciding means for deciding a shortest predetermined period from the predetermined periods determined by the determining means that the different device stably makes a response, as a standby time for the different device connected through the connecting means. 
         [0019]    According to the embodiments of the invention, a control signal is changed for a predetermined period, the control signal being outputted to a different device through a connecting means for use in connecting to the different device. Then, the predetermined period is changed, it is determined for each of the changed predetermined periods whether the different device stably makes a response to a change in the control signal, and the shortest predetermined period is decided from the predetermined periods determined that a different device stably makes a response, as a standby time for a different device connected through the connecting means. 
         [0020]    According to the embodiments of the invention, control is allowed over a different device in the optimum standby time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a block diagram depicting an exemplary configuration of an embodiment of a sink device to which the invention is adapted; 
           [0022]      FIG. 2  is a diagram depicting changes in hot plug signals; 
           [0023]      FIG. 3  is a flowchart illustrative of a low period optimization process; and 
           [0024]      FIG. 4  is a flowchart illustrative of an input switching process. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Hereinafter, a specific embodiment to which the invention is adapted will be described in detail with reference to the drawings. 
         [0026]      FIG. 1  is a block diagram depicting an exemplary configuration of an embodiment of a sink device to which the invention is adapted. 
         [0027]    In  FIG. 1 , a sink device  11  is configured of three HDMI terminals  12 ( 1 ) to  12 ( 3 ), a signal processing unit  13 , a memory  14 , and a control unit  15 . 
         [0028]    The HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ) are connecting means in conformity with the HDMI standard, each of which connects a source device, not shown, to the sink device  11  through an HDMI cable, not shown. 
         [0029]    The signal processing unit  13  processes signals sent and received from source devices individually connected to the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ) under control performed by the control unit  15 . For example, when a TMDS (Transition Minimized Differential Signaling) signal, which is a signal for transmitting content data, is sent from the source device, the signal processing unit  13  receives and supplies the TMDS signal to a circuit in the later stage, not shown (for example, a decryption circuit or a display circuit). In addition, the signal processing unit  13  controls switching between high and low levels of a control signal to be outputted to the source device through the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ). 
         [0030]    In addition, the signal processing unit  13  has a switching function of switching inputs such that a given source device among a plurality of the source devices connected through the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ) supplies a content to the sink device  11 . More specifically, the signal processing unit  13  has the switching function, whereby the sink device  11  can be mounted with a plurality of HDMI terminals. 
         [0031]    The memory  14  is formed of a non-volatile flash memory (for example, EEPROM (Electronically Erasable and Programmable Read Only Memory)) that can be controlled to read and write data by the control unit  15 . The memory  14  stores a program performed by the control unit  15  and data necessary to conduct a process performed by the control unit  15 . 
         [0032]    For example, the memory  14  stores information for each of the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ), the information indicating a standby time for which a hot plug signal is turned to low level for waiting in an input switching process (a process shown in  FIG. 4 , described later) in which the source device that inputs a content to the sink device  11  is switched. (Hereinafter, the information is properly referred to as a low period T_LOW of the hot plug signal). In other words, the memory  14  stores a low period T_LOW ( 1 ) to a low period T_LOW ( 3 ) of the hot plug signals as they are associated with the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ), respectively. 
         [0033]    In addition, the memory  14  stores an initial value t(init) of the low period T_LOW of the hot plug signal, the initial value being used in the initial state before a low period optimization process is performed in which the low period T_LOW of the hot plug signal is optimized for each of the HDMI terminals (a process shown in  FIG. 3 , described later). As the initial value t(init), a sufficiently long time (for example, 1000 milliseconds) is set. 
         [0034]    The control unit  15  incorporates therein a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In the control unit  15 , the CPU performs a program stored in the ROM, or a program read out of the memory  14  and loaded to the RAM, whereby a process is performed to control each component of the sink device  11 . 
         [0035]    For example, in the input switching process of switching the source device that inputs a content to the sink device  11 , the control unit  15  controls the signal processing unit  13  to switch the outputs (high/low level) of the hot plug signal of the HDMI terminal. 
         [0036]    More specifically, suppose that a user manipulates a manipulating unit, not shown, to select one of the HDMI terminals such that the source device connected to the HDMI terminal  12 ( 2 ), for example, supplies a content to the sink device  11 . At this time, the control unit  15  controls the signal processing unit  13  such that the output of the hot plug signal of the HDMI terminal  12 ( 2 ) is turned to low level for the low period T_LOW ( 2 ) milliseconds of the hot plug signal, which is associated with the HDMI terminal  12 ( 2 ) and stored in the memory  14 . 
         [0037]      FIG. 2  is a diagram depicting a change in hot plug signals when the HDMI terminal  12 ( 2 ) is selected in the input switching process. 
         [0038]      FIG. 2  shows a hot plug signal Hotplug ( 1 ) to a hot plug signal Hotplug ( 3 ), which are outputted from the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ), respectively. In order to always read EDID of the source devices individually connected to the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ), the control unit  15  sets the hot plug signals of all the HDMI terminals to high level all the time. 
         [0039]    Then, when the user makes a manipulation to select the HDMI terminal  12 ( 2 ) to receive a content, in response to the manipulation, the control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug ( 2 ) of the HDMI terminal  12 ( 2 ) from high to low level. Then, the control unit  15  reads the low period T_LOW ( 2 ), which is associated with the HDMI terminal  12 ( 2 ) and stored in the memory  14 , turns the hot plug signal Hotplug ( 2 ) of the HDMI terminal  12 ( 2 ) to low level, and then holds the process until the low period T_LOW ( 2 ) passes. After that, at the timing at which the low period T_LOW ( 2 ) has elapsed, the control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug ( 2 ) of the HDMI terminal  12 ( 2 ) from low to high level. 
         [0040]    Thus, the hot plug signal Hotplug ( 2 ) of the HDMI terminal  12 ( 2 ) is low for the low period T_LOW ( 2 ) milliseconds. In other words, the signal processing unit  13  changes the hot plug signal Hotplug ( 2 ) to be outputted to the source device connected through the HDMI terminal  12 ( 2 ) from high to low level for the low period T_LOW ( 2 ) milliseconds. 
         [0041]    Here, when the response time (a time period in which the source device detects that the hot plug signal is turned to low level and responds to it) of the source device connected to the HDMI terminal  12 ( 2 ) is longer than the low period T_LOW ( 2 ) milliseconds, authentication is reset in the source device. Then, to the sink device  11 , the source device sends a response including the result of authentication reset and data to send to the sink device  11 . 
         [0042]    In addition, as described above, the length of the response time of the source device is varied depending on devices. Therefore, the sink device  11  performs the low period optimization process of optimizing the low period of the hot plug signal to each of the source devices connected to the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ). Then, in the memory  14 , the low period determined in the low period optimization process is stored as associated with each of the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ). 
         [0043]    For example, the low period optimization process is registered as one item of menu screens displayed on a display (not shown) that displays video outputted from the sink device  11  in conducting various settings of the sink device  11 . The user can manipulate the manipulating unit and make an instruction to display a menu screen on the display for performing the low period optimization process. 
         [0044]    Next,  FIG. 3  is a flowchart illustrative of the low period optimization process of optimizing the low period of the hot plug signal. 
         [0045]    When the user makes an instruction to perform the low period optimization process, the process is started. In Step S 11 , the control unit  15  sets a set value n for identifying the HDMI terminal  12  to one as the initial value, and the process goes to Step S 12 . 
         [0046]    In Step S 12 , the control unit  15  initializes a trial low period t, which is the low period of the hot plug signal temporarily used in the low period optimization process, and a final result res, which is the low period finally determined as the result in the low period optimization process. In other words, the control unit  15  reads the initial value t(init) of the low period of the hot plug signal (for example, it is a sufficiently long time such as 1000 milliseconds) out of the memory  14 , sets the initial value t(init) to the trial low period t, and sets the trial low period t to the final result res. 
         [0047]    After the process of Step S 12 , the process goes to Step S 13 . The control unit  15  sets a parameter m, which is used in the low period optimization process, to zero, for example, as the initial value, and the process goes to Step S 14 . 
         [0048]    In Step S 14 , the control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug (n) of an nth HDMI terminal  12 ( n ) from high to low level, and the process goes to Step S 15 . 
         [0049]    In Step S 15 , the control unit  15  holds the process for the trial low period t, which is initialized in Step S 12 , or the trial low period t, which is updated in Step S 20 , described later. Then, when the trial low period t passes after the hot plug signal Hotplug (n) is switched to low level in Step S 14 , the process goes to Step S 16 . 
         [0050]    In Step S 16 , the control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) from low to high level. In other words, in the processes of Steps S 14  to S 16 , the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) is turned to low level for the trial low period t. 
         [0051]    After the process of Step S 16 , the process goes to Step S 17 . The control unit  15  determines whether authentication is reset in the source device connected to the HDMI terminal  12 ( n ) because the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) is turned to low level for the trial low period t in Steps S 14  to S 16 . For example, when the trial low period t is longer than the response time of the source device, the source device detects that the hot plug signal is turned to low level, and resets authentication as well as sends the response to the sink device  11 . Therefore, the sink device  11  determines whether the source device sends a response. 
         [0052]    In Step S 17 , if the control unit  15  determines that authentication is not reset, the process goes to Step S 22 , whereas if the control unit  15  determines that authentication is reset, the process goes to Step S 18 . 
         [0053]    In Step S 18 , the control unit  15  increments the parameter m by one, and the process goes to Step S 19 . 
         [0054]    In Step S 19 , the control unit  15  determines whether the parameter m incremented in Step S 18  is below a number m(max) preset as the number of times to confirm the occurrence of authentication reset. 
         [0055]    In Step S 19 , if the control unit  15  determines that the parameter m is below the number m(max), the process returns to Step S 14 , and the similar processes are repeated. In other words, the control unit  15  repeats the process of confirming the occurrence of authentication reset until the control unit  15  confirms the occurrence of authentication reset for the number m(max), or determines that authentication is not reset in Step S 17 . As described above, the occurrence of authentication reset is confirmed for the number m(max), whereby it can be determined whether the source device stably makes a response. 
         [0056]    On the other hand, in Step S 19 , if the control unit  15  determines that the parameter m is not below the number m(max) (the parameter m is greater than the number m(max)), the process goes to Step S 20 . 
         [0057]    In Step S 20 , the control unit  15  sets the final result res to the current trial low period t (that is, the trial low period t for which the process is held in Step S 14 ) as well as sets the value obtained by subtracting 100 milliseconds from the current trial low period t to a new trial low period t. In other words, because the source device connected to the HDMI terminal  12 ( n ) is allowed to stably (reliably) reset authentication in the current trial low period t, the control unit  15  updates the trial low period t to a shorter period in order to determine the shortest low period for which the source device connected to the HDMI terminal  12 ( n ) can stably make a response. For example, when the current trial low period t is 500 milliseconds, the control unit  15  sets the final result res to 500 milliseconds as well as sets the new trial low period t to 400 milliseconds. 
         [0058]    After the process of Step S 20 , the process goes to Step S 21 . The control unit  15  determines whether the trial low period t updated in the previous Step S 20  is longer than a minimum value t(min), which is defined as the minimum value for the low period of the hot plug signal. For example, in the HDMI standard, the minimum value t(min) is defined to be 100 milliseconds. 
         [0059]    In Step S 21 , if the control unit  15  determines that the trial low period t is longer the minimum value t(min), the process returns to Step S 13 , and the similar processes are repeated. In other words, the processes are repeated until it is determined that the source device connected to the HDMI terminal  12 ( n ) reliably makes a response even at the minimum value t(min), or it is determined that authentication is not reset in Step S 17 . 
         [0060]    On the other hand, in Step S 21 , if the control unit  15  determines that the new low period t does not exceed the minimum value t(min) (that is, the new low period t is equal to or below the minimum value t(min)), the process goes to Step S 22 . In other words, in this case, the source device connected to the HDMI terminal  12 ( n ) reliably makes a response even at the minimum value t(min). 
         [0061]    In Step S 22 , the control unit  15  associates the final result res with the HDMI terminal  12 ( n ) as the low period T_LOW (n) of the hot plug signal Hotplug (n) optimized to the source device connected to the HDMI terminal  12 ( n ), and stores it in the memory  14 . 
         [0062]    For example, in Step S 21 , suppose that it is determined that the trial low period t updated in Step S 20  does not exceed the minimum value t(min) and the process goes to Step S 22 . In this case, the minimum value t(min) that is the final result res at this time is the shortest low period in which the source device connected to the HDMI terminal  12 ( n ) is allowed to stably reset authentication. In other words, in this case, the minimum value t(min) is the optimized low period. 
         [0063]    On the other hand, for example, suppose that it is determined that authentication is not reset in Step S 17  and the process goes to Step S 22 . In this case, it is confirmed that the trial low period t in Step S 15  does not allow the source device connected to the HDMI terminal  12 ( n ) to reset authentication. Therefore, in this case, the current final result res (that is, the trial low period t finally determined that the source device stably resets authentication) is the shortest low period, for which the source device connected to the HDMI terminal  12 ( n ) is allowed to stably reset authentication. In other words, in this case, the current final result res is the optimized low period. 
         [0064]    After the process of Step S 22 , the process goes to Step S 23 . The control unit  15  determines whether the set value n for identifying the HDMI terminal  12  is equal to or greater than a number N of the HDMI terminals mounted on the sink device  11  (N=3 in the example shown in  FIG. 1 ). In other words, the control unit  15  determines whether all the HDMI terminals mounted on the sink device  11  have been processed, that is, in the example shown in  FIG. 1 , whether the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ) have been processed. 
         [0065]    In Step S 23 , if the control unit  15  determines that the set value n is still below the number N, there is an HDMI terminal that has not been processed. The process goes to Step S 24 , and the control unit  15  increments the set value n by one. Then, a subsequent HDMI terminal is set to a target for processing, the process returns to Step S 12 , and the similar processes are repeated. 
         [0066]    On the other hand, in Step S 23 , if the control unit  15  determines that the set value n is equal to or greater the number N, all the HDMI terminals mounted on the sink device  11  have been processed, and the low period optimization process is ended. 
         [0067]    As described above, in the low period optimization process, the sink device  11  can determine the low period in which the source device connected to the HDMI terminal can stably make a response, for each of the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ). In other words, the shortest low period can be optimized for each of the source devices. 
         [0068]    Therefore, in the input switching process of switching the source device that inputs a content to the sink device  11 , processing can be conducted by using the low period optimized for each of the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ). 
         [0069]    Next,  FIG. 4  is a flowchart illustrative of the input switching process of switching the source device that inputs a content to the sink device  11 . 
         [0070]    For example, when the user specifies (selects) the nth HDMI terminal  12 ( n ) and manipulates the manipulating unit, not shown, such that the source device connected to the HDMI terminal  12 ( n ) inputs a content to the sink device  11 , the process is started. In Step S 31 , based on the signal supplied from the manipulating unit in response to the user manipulation, the control unit  15  controls the signal processing unit  13  such that the content fed through the user specified HDMI terminal  12 ( n ) is outputted. Under control performed by the control unit  15 , the signal processing unit  13  switches connection so as to connect the HDMI terminal  12 ( n ) to the circuit in the later stage, not shown. 
         [0071]    After the process of Step S 31 , the process goes to Step S 32 . The control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) from high to low level, and the process goes to Step S 33 . 
         [0072]    In Step S 33 , the control unit  15  reads the low period T_LOW (n) stored as associated with the HDMI terminal  12 ( n ), that is, the low period T_LOW (n) optimized to the source device connected to the HDMI terminal  12 ( n ) out of the memory  14 . The control unit  15  holds the process until the low period T_LOW (n) passes after the hot plug signal Hotplug (n) is turned to low level in Step S 32 . Then, after the low period T_LOW (n) passes, the process goes to Step S 34 . 
         [0073]    In Step S 34 , the control unit  15  controls the signal processing unit  13  to switch the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) from low to high level. In other words, in the processes of Step S 32  to S 34 , the hot plug signal Hotplug (n) of the HDMI terminal  12 ( n ) is turned to low level for the low period T_LOW (n), and the source device connected to the HDMI terminal  12 ( n ) is requested to reset authentication. 
         [0074]    After the process of Step S 34 , the process goes to Step S 35 . The signal processing unit  13  receives a response to the request from the sink device  11  sent from the source device that authentication is reset, and supplies the response to the control unit  15 . 
         [0075]    In addition to the response of authentication reset, the source device having reset authentication sends data signals including resolution information, color space information, and sound information, for example, at predetermined intervals, and the control unit  15  receives the data signals through the signal processing unit  13 . Then, the control unit  15  holds the process until the data signals sent from the source device become stable, and after the data signals are stable (for example, after the data signals having the same descriptions are sent for a predetermined number of times), the control unit  15  makes the settings of the display and a speaker (both are not shown) provided in the sink device  11  based on the resolution information, color space information, and sound information included in the data signals. Thus, the sink device  11  can normally output the content supplied from the source device. 
         [0076]    After the process of Step S 35 , the process goes to Step S 36 . The signal processing unit  13  outputs the content data supplied from the source device to the circuit in the later stage, and the control unit  15  cancels the mute of the display and the amplifier, and starts to output the content. In other words, the control unit  15  allows the display to display video, and allows the speaker to output sounds. After the process of Step S 36 , the input switching process is ended. 
         [0077]    As described above, in the sink device  11 , in the input switching process, because the hot plug signal is turned to low level and processing is held for the low period determined in the low period optimization process, the sink device  11  does not need to hold processing for an unnecessarily long time. Therefore, a time period in which a manipulation is made to switch the selection of the source device and the content is outputted can be made shorter than before. 
         [0078]    In other words, in the sink device before, because the low period is set as matched with the source device having a long response time, for a source device having a short response time, processing is held for an unnecessarily long time, and it takes a long time to output a content. 
         [0079]    In contrast to this, because the sink device  11  optimizes a low period to a source device and uses the low period determined for each source device, it does not unnecessarily take a long time to hold processing for the source device having a short response time. Therefore, a content can be outputted for a proper standby time depending on the response time of the source device. Therefore, a time period for a user has to wait can be shortened, and an excellent response can be made to a manipulation. In other words, the usability of the sink device  11  can be improved. 
         [0080]    In addition, because a low period in which a source device can stably make a response can be determined in the low period optimization process even though a source device having a long response time is connected, the sink device  11  can reliably control the source device in connections to any source devices. 
         [0081]    In addition, the control unit  15  can perform not only a program preinstalled in the memory  14  but also a program downloaded and installed (updated) in the memory  14  through a communication apparatus, not shown, for example. Therefore, the low period optimization process and the input switching process can be implemented by updating a program performed by means of the control unit  15 , and no special hardware is required. 
         [0082]    In addition, in the sink device  11 , the control unit  15  controls the signals outputted from the HDMI terminal  12 ( 1 ) to the HDMI terminal  12 ( 3 ) through the signal processing unit  13 , and the control unit  15  can also directly control these signals. 
         [0083]    In addition, it is unnecessary to always perform the processes described with reference to the flowcharts in a time series in the described order, and the processes may be performed in parallel or separately (for example, parallel processing or object processing). In addition, a single CPU may process the program, or a plurality of CPUs may process the program in a distributed manner. 
         [0084]    In addition, the embodiment of the invention is not limited to the embodiment described above, which can be variously modified within the scope of the teachings of the invention. 
         [0085]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.