Abstract:
An audio/video transmission apparatus includes a hot plug detecting section for detecting a hot plug signal output from a reception apparatus connected thereto via an High Definition Multimedia Interface (HDMI), an EDID reading/determining section for determining Extended Display Identification Data (EDID) information of the reception apparatus, a type determining section for determining a type of the reception apparatus based on a result of the determination of the EDID information, a TMDS switching section for designating an output scheme corresponding to the type of the reception apparatus of a plurality of Transition Minimized Differential Signaling (TMDS) signal output schemes; and a TMDS output section for outputting a TMDS signal in accordance with the designated output scheme.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an audio/video transmission apparatus and an audio/video transmission method including a high-speed interface for transmitting audio and video information. 
         [0003]    2. Description of the Related Art 
         [0004]    A serial transmission interface called a High Definition Multimedia Interface (HDMI) for transmitting audio/video information is well known. 
         [0005]      FIG. 6  is a diagram showing a configuration of a conventional audio/video transmission apparatus and a conventional audio/video reception apparatus.  FIG. 6  shows the audio/video transmission apparatus  600  and the audio/video reception apparatus  630 , which are connected to each other via an HDMI cable  680 . The audio/video transmission apparatus  600  is any of a DVD player, an HD recorder and the like. The audio/video reception apparatus  630  is any of a television set, a projector, an AV amplifier and the like. 
         [0006]    In  FIG. 6 ,  640  indicates a storage element (memory) for storing Extended Display Identification Data (EDID) information,  651  indicates a Transition Minimized Differential Signaling (TMDS) input section for receiving a TMDS signal from the external audio/video transmission apparatus  600  connected thereto,  652  indicates a hot plug output section for outputting a hot plug signal to the external audio/video transmission apparatus  600  connected thereto,  650  indicates an HDMI processing section including the TMDS input section  651  and the hot plug output section  652 ,  660  indicates an audio/video processing section for performing various audio/video processes, and  670  indicates an audio/video output section for outputting audio and video that have been processed by the audio/video processing section  660 . The audio/video reception apparatus  630  has an input section (not shown) for receiving a desired control item, as well as the storage element  640 , the HDMI processing section  650 , the audio/video processing section  660 , and the audio/video output section  670 . 
         [0007]    On the other hand,  611  indicates an EDID reading/determining section for reading out EDID information from the storage element  640  and determining a content of the EDID information,  612  indicates a hot plug detecting section for detecting a hot plug signal from the hot plug output section  652 ,  613  indicates a TMDS output section for outputting a TMDS signal to the TMDS input section  651 ,  610  indicates an HDMI processing section including the EDID reading/determining section  611 , the hot plug detecting section  612 , and the TMDS output section  613 , and  620  indicates an audio/video processing section for performing various audio/video processes. The audio/video transmission apparatus  600  has an input section (not shown) for receiving a desired control item, a tuner (not shown), and an audio/video recording/reproducing section (not shown) for recording audio and video received via the tuner or reproducing recorded audio and video, as well as the HDMI processing section  610  and the audio/video processing section  620 . Note that signal lines of the HDMI cable  680  that are not herein described are not shown. 
         [0008]      FIG. 7  shows a TMDS signal output scheme of the TMDS output section  613 . The audio/video transmission apparatus  600  and the audio/video reception apparatus  630  are connected to each other via the HDMI cable  680 . When both the apparatuses  600  and  630  are powered ON, the hot plug output section  652  causes a hot plug signal to go from Low to High. The hot plug detecting section  612 , when detecting the transition of the hot plug signal from Low to High, determines that the audio/video transmission apparatus  600  is physically connected to the audio/video reception apparatus  630 , and EDID information can be read out, and instructs the EDID reading/determining section  611  to read out EDID information from the storage element  640 . 
         [0009]    The EDID reading/determining section  611  reads out EDID information from the storage element  640 , and based on a content of the EDID information, determines whether the audio/video reception apparatus  630  is an HDMI apparatus, a Digital Visual Interface (DVI) apparatus, or other unknown apparatuses. When determining that the audio/video reception apparatus  630  is an HDMI apparatus, the EDID reading/determining section  611  instructs the TMDS output section  613  to output a TMDS signal. 
         [0010]    As shown in  FIG. 7 , the TMDS output section  613  outputs the TMDS signal in the following procedure. The TMDS signal is output for a period of t 1 , then stopped for a period of t 2 , and then continuously output. An InfoFrame packet is output at a timing “P 1 ” that is a time after a period of t 3  has elapsed since the start of the continuous output. An authentication process is started at a timing “P 2 ”. Output of audio/video information is started at a timing “P 3 ” at which the authentication process is ended. The audio/video information is either one that has been received by the tuner or one that has been reproduced by the audio/video recording/reproducing section. The input section selects either one of the pieces of audio/video information, and also selects the type of audio, the resolution of output video and the like. The audio/video processing section  620  processes the audio/video information into a desired audio type and video resolution and outputs the resultant data to the TMDS output section  613 . 
         [0011]    Note that the time periods t 1 , t 2  and t 3  each have a fixed value, so that only a single TMDS signal output scheme is available irrespective of the type, manufacturer, model and the like of the connected audio/video reception apparatus  630 . 
         [0012]    The audio/video reception apparatus  630  processes the received audio/video information into audio and video that can be listened and viewed using the audio/video processing section  660 , and outputs the resultant data to the audio/video output section  670 . Stages following the audio/video output section  670  vary depending on whether the audio/video reception apparatus  630  is a television set, a projector, or an AV amplifier, and will not be described. Also, a case where it is determined that the audio/video reception apparatus  630  is a DVI apparatus or other unknown apparatuses, will not be described. 
         [0013]    Incidentally, in the configuration described above, the TMDS signal output scheme and the InfoFrame packet output timing are fixed. Therefore, a mismatch in process timing may occur between the sender and the receiver, depending on the connected audio/video reception apparatus, so that a defective phenomenon may occur, e.g., the authentication process may fail, audio may not be output or a discomfort sound may be generated, video may not be output or may be disturbed, or the like. 
         [0014]    To avoid this, an audio/video transmission apparatus according to a conventional technique determines the type of a reception apparatus connected thereto based on EDID information including product information, manufacturer information, and video format information, and switches a control program only for a specific type. Thereby, even if the reception apparatus causes a hot plug signal to go from High to Low without holding the hot plug signal (without fixing the hot plug signal to High) while an authentication process is being performed, the transition is ignored and the authentication process is continued, so that a defective phenomenon is prevented (see Japanese Unexamined Patent Application Publication No. 2006-203725). 
       SUMMARY OF THE INVENTION 
       [0015]    The defective phenomena described above may often be reduced by adjusting the TMDS signal output scheme and the InfoFrame packet output timings (t 1 , t 2  and t 3  of  FIG. 7 ) in the audio/video transmission apparatus. However, the adjustment of the timings t 1 , t 2  and t 3  has a side effect that a similar defective phenomenon occurs in an audio/video reception apparatus that would otherwise be conventionally free of such a problem. 
         [0016]    Also, in order to secure the quality of a conventional apparatus every time the timings t 1 , t 2  and t 3  are adjusted, connection to the audio/video reception apparatus that would otherwise be conventionally free of the problem needs to be verified again so as to confirm that there is not the side effect. This process requires a vast time that is proportional to the number of apparatuses to be verified and the number of items to be evaluated. 
         [0017]    In view of the problems described above, the present invention has been achieved. An object of the present invention is to provide an audio/video transmission apparatus having a plurality of output schemes in which the type of a reception apparatus is determined based on EDID information read out from an audio/video reception apparatus connected thereto, and a TMDS signal and an InfoFrame packet corresponding to the type can be output. 
         [0018]    To achieve the object, the present invention provides an audio/video transmission apparatus connectable to an audio/video reception apparatus via a serial transmission interface, including a section for determining a type of the audio/video reception apparatus based on apparatus information about the connected audio/video reception apparatus, and a section for selecting an information transmission signal output scheme corresponding to the type of the connected audio/video reception apparatus from a plurality of output schemes for an information transmission signal, and outputting the information transmission signal. 
         [0019]    More specifically, the present invention provides an audio/video transmission apparatus connectable to an audio/video reception apparatus via an HDMI interface, including a hot plug detecting section for detecting a hot plug signal output from the connected audio/video reception apparatus, an EDID reading/determining section for reading EDID information of the connected audio/video reception apparatus, and determining a content of the EDID information, a type determining section for determining a type of the connected audio/video reception apparatus based on a result of the determination of the EDID information, a TMDS switching section for designating an output scheme corresponding to the type of the connected audio/video reception apparatus of a plurality of TMDS signal output schemes, and a TMDS output section for outputting a TMDS signal in accordance with the output scheme designated by the TMDS switching section. 
         [0020]    According to the present invention, as compared to the conventional single-output scheme, a mismatch in process timing between the sender and the receiver can be reduced, thereby making it possible to reduce a phenomenon due to the mismatch, such as a failure in authentication, the absence or disturbance of audio or video output, or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]      FIG. 1  is a block diagram showing a configuration of an audio/video transmission apparatus according to the present invention and an audio/video reception apparatus. 
           [0022]      FIGS. 2A to 2D  are diagrams showing various TMDS signal output schemes and various InfoFrame packet output timings in the audio/video transmission apparatus of  FIG. 1 . 
           [0023]      FIG. 3  is a flowchart of a process of determining the type of the reception apparatus in the audio/video transmission apparatus of  FIG. 1 . 
           [0024]      FIG. 4  is a diagram showing a structure of an extension block of EDID information held by a storage element of  FIG. 1 . 
           [0025]      FIG. 5  is a block diagram showing a detailed configuration of a TMDS switching section of  FIG. 1 . 
           [0026]      FIG. 6  is a block diagram showing a configuration of a conventional audio/video transmission apparatus and a conventional audio/video reception apparatus. 
           [0027]      FIG. 7  is a diagram showing a TMDS signal output scheme and an InfoFrame packet output timing in the audio/video transmission apparatus of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]      FIG. 1  is a diagram showing a configuration of an audio/video transmission apparatus according to the present invention and an audio/video reception apparatus.  FIG. 1  shows the audio/video transmission apparatus  100  and the audio/video reception apparatus  130 , which are connected to each other via an HDMI cable  180 . The audio/video transmission apparatus  100  is any of a DVD player, an HD recorder and the like. The audio/video reception apparatus  130  is any of a television set, a projector, an AV amplifier and the like. Note that the present invention may be implemented by hardware or software, or in combination of hardware and software. 
         [0029]    In  FIG. 1 ,  140  indicates a storage element (memory) for storing EDID information,  151  indicates a TMDS input section for receiving a TMDS signal from the external audio/video transmission apparatus  100  connected thereto,  152  indicates a hot plug output section for outputting a hot plug signal to the external audio/video transmission apparatus  100  connected thereto,  150  indicates an HDMI processing section including the TMDS input section  151  and the hot plug output section  152 ,  160  indicates an audio/video processing section for performing various audio/video processes, and  170  indicates an audio/video output section for outputting audio and video processed by the audio/video processing section  160 . The audio/video reception apparatus  130  has an input section (not shown) for receiving a desired control item, as well as the storage element  140 , the HDMI processing section  150 , the audio/video processing section  160 , and the audio/video output section  170 . 
         [0030]    On the other hand,  111  indicates an EDID reading/determining section for reading out EDID information form the storage element  140  and determines a content of the EDID information,  112  indicates a hot plug detecting section for determining a hot plug signal from the hot plug output section  152 ,  113  indicates a TMDS output section for outputting a TMDS signal to the TMDS input section  151 ,  114  indicates a type determining section for determining the type of the audio/video reception apparatus  130 ,  115  indicates a TMDS switching section that includes a plurality of output schemes and a plurality of InfoFrame packet output timings for the TMDS signal output from the TMDS output section  113 , and switches the output schemes and the InfoFrame packet output timings,  110  indicates an HDMI processing section including the EDID reading/determining section  111 , the hot plug detecting section  112 , the TMDS output section  113 , the type determining section  114 , and the TMDS switching section  115 ,  120  indicates an audio/video processing section for performing various audio/video processes,  121  indicates an input section for providing a desired setting,  122  indicates a tuner,  123  indicates an audio/video recording/reproducing section including a hard disk drive (hereinafter referred to as an HDD), a CD/DVD drive or the like that records audio and video received by the tuner  122  or reproduces recorded audio and video, and  124  indicates a rewrite section for rewriting the TMDS signal output schemes and the InfoFrame packet output timings possessed by the TMDS switching section  115 . The audio/video transmission apparatus  100  includes the HDMI processing section  110 , the audio/video processing section  120 , the input section  121 , the tuner  122 , the audio/video recording/reproducing section  123 , and the rewrite section  124 .  190  indicates a communications network, such as the Internet or the like. Note that signal lines of the HDMI cable  180  that are not herein described are not shown. 
         [0031]      FIGS. 2A to 2D  show output schemes of a TMDS signal that is output by the TMDS switching section  115  to the TMDS output section  113  for instruction. The output schemes are provided, corresponding to respective types of the audio/video reception apparatus  130  (i.e., a television set, a projector, an AV amplifier, and others). 
         [0032]      FIG. 3  is a flowchart of a process of determining the type of the audio/video reception apparatus  130  using the EDID reading/determining section  111  and the type determining section  114 . 
         [0033]      FIG. 4  is a diagram showing a structure of an extension block of the EDID information. In  FIG. 4 , information about a video resolution (480i, 720p, 1080i, etc.) and a color space (YCbCr4:4:4, RGB, etc.) that can be displayed by the audio/video reception apparatus  130  is written in a video tag. Information about an audio format (I 2 S, etc.) and audio frequency (48 kHz, 192 kHz, etc.) that can be reproduced by the audio/video reception apparatus  130  is written in an audio tag. Information about the number of audio channels that can be reproduced by the audio/video reception apparatus  130  is written in a speaker tag. Vender information is written in a vender tag. 
         [0034]    When the audio/video transmission apparatus  100  and the audio/video reception apparatus  130  are connected to each other via the HDMI cable  180  and both the apparatuses  100  and  130  are powered ON, the hot plug output section  152  causes a hot plug signal to go from Low to High. The hot plug detecting section  112 , when detecting the transition of the hot plug signal from Low to High, determines that the audio/video transmission apparatus  100  and the audio/video reception apparatus  130  are physically connected to each other, so that EDID information can be read out, and then instructs the EDID reading/determining section  111  to read out EDID information from the storage element  140 . 
         [0035]    It will be described how the EDID reading/determining section  111  and the type determining section  114  determine the type of the audio/video reception apparatus  130 , with reference to  FIG. 3 . 
         [0036]    The EDID reading/determining section  111 , after reading out EDID information from the storage element  140 , determines whether or not the structure of the EDID information includes an extension block (step  1 ). If an extension block is included, the EDID reading/determining section  111  determines that the audio/video reception apparatus  130  is an HDMI apparatus, and the process goes to step  2 . If an extension block is not included, the EDID reading/determining section  111  determines that the audio/video reception apparatus  130  is a DVI apparatus, and the process goes to step  4 - 5 . 
         [0037]    In step  2 , audio information belonging to the audio tag and the speaker tag included in the extension block is read out. 
         [0038]    In step  3 , the type of the audio/video reception apparatus  130  is determined based on the information read out in step  2 . If the number of audio channels is two and the supported audio frequency is 48 kHz, the type of the audio/video reception apparatus  130  is determined to be a television set, and the process goes to step  4 - 1 . If audio input is not permitted (not required), the type of the audio/video reception apparatus  130  is determined to be a projector, and the process goes to step  4 - 2 . If the number of audio channels is up to eight and the supported audio frequency is up to 192 kHz, the type of the audio/video reception apparatus  130  is determined to be an AV amplifier, and the process goes to step  4 - 3 . If the type of the audio/video reception apparatus  130  is determined to correspond to none of these types (i.e., determined to be unknown), the process goes to step  4 - 4 . 
         [0039]    In step  4 -i (i= 1  to  5 ), information for transmitting the type of the audio/video reception apparatus  130  determined in step  3  to the TMDS switching section  115  is set. 
         [0040]    In step  5 , the information set in step  4 -i (i= 1  to  5 ) is transmitted to the TMDS switching section  115 . 
         [0041]    The TMDS switching section  115  selects a TMDS signal output scheme and an InfoFrame packet output timing suitable for the audio/video reception apparatus  130  based on the information transmitted from the type determining section  114 . For example, if the information indicates “television set”, a scheme A in  FIG. 2A  is selected. If the information indicates “projector”, a scheme B in  FIG. 2B  is selected. If the information indicates “AV amplifier”, a scheme C in  FIG. 2C  is selected. If the information indicates “unknown” or “DVI apparatus”, a scheme D in  FIG. 2D  is selected. After the scheme selection, an instruction to perform TMDS signal output and InfoFrame packet output using the scheme selected by the TMDS output section  113  is issued. 
         [0042]    The TMDS output section  113  outputs a TMDS signal in accordance with the instruction from the TMDS switching section  115  in the following procedure. As in schemes of  FIGS. 2A to 2D , the TMDS signal is output for a period of TA 1  (or TB 1 , TC 1  or TD 1 ), then stopped for a period of TA 2  (or TB 2 , TC 2  or TD 2 ), and then continuously output. An InfoFrame packet is output at a timing “P 1 ” that is a time after a period of TA 3  (or TB 3 , TC 3  or TD 3 ) has elapsed since the start of the continuous output. An authentication process is started at a timing “P 2 ”. Output of audio/video information is started at a timing “P 3 ” at which the authentication process is ended. 
         [0043]    The output audio/video information is either one that has been received by the tuner  122  or one that has been reproduced by the audio/video recording/reproducing section  123 . The input section  121  selects either one of the pieces of audio/video information, and also selects the type of audio, the resolution of output video and the like. The audio/video processing section  120  processes the audio/video information into a desired audio type and video resolution and outputs the resultant data to the TMDS output section  113 . 
         [0044]    The audio/video reception apparatus  130  processes the received audio/video information into audio and video that can be listened and viewed using the audio/video processing section  160 , and outputs the resultant data to the audio/video output section  170 . Stages following the audio/video output section  170  vary depending on whether the audio/video reception apparatus  130  is a television set, a projector, or an AV amplifier, and will not be described. 
         [0045]    If the audio/video reception apparatus  130  is, for example, newly designed or slightly changed, then when the TMDS signal output scheme and the InfoFrame packet output timing of  FIGS. 2A to 2D  are used, a defective phenomenon may occur, e.g., an authentication process may fail, audio may not be output or a discomfort sound may be generated, video may not be output or may be disturbed, or the like. In this case, such a defective phenomenon may be reduced by adjusting TA 1  (or TB 1 , TC 1  or TD 1 ), TA 2  (or TB 2 , TC 2  or TD 2 ), or TA 3  (or TB 3 , TC 3  or TD 3 ). Each time period can be adjusted by adjusting only a scheme corresponding to the type of the audio/video reception apparatus  130 , i.e., it is not necessary to adjust the other schemes. 
         [0046]    For example, if a newly designed television set is connected to the audio/video transmission apparatus  100 , the TMDS signal output scheme and the InfoFrame packet output timing for the scheme A are selected. In this case, it is assumed that the process flow, process time or the like of the television set is changed, and therefore, a mismatch in process timing occurs between the television set and the audio/video transmission apparatus  100 , so that neither audio nor video is output. It is also assumed that, as a result of adjustment, an improvement is achieved by elongating the time period TA 3  by ΔT from the current state and delaying the InfoFrame packet output timing (hereinafter referred to as a “scheme A′” (not shown)). Although the scheme A′ is effective for the newly designed television set, it is not known at this time whether or not the scheme A′ is effective for a television set that conventionally does not have a problem. Therefore, the scheme A′ is used to verify connectivity with respect to the conventional television set, and if a problem does not arise, the scheme A′ is formally adopted and set as the scheme A. If a problem arises, additional measures, such as time adjustment or the like, are taken so as to find out a scheme suitable for both the television set that conventionally does not have a problem and the newly designed television set. This time adjustment is only for television sets, so that none of the scheme B for a projector, the scheme C for an AV amplifier, and the scheme D for others or a DVI apparatus is affected. Also, reverification of connectivity may be performed only with respect to the television set, i.e., reverification of connectivity is not required for the other types of apparatuses that have not been adjusted. 
         [0047]    As described above, with the configuration of  FIG. 1 , a plurality of TMDS signal output schemes and a plurality of InfoFrame packet output timings corresponding to the types of audio/video reception apparatuses to be connected are provided, and the schemes are switched and output, depending on the type of a connected audio/video reception apparatus. Therefore, as compared to the conventional single-output scheme, a mismatch in process timing between the sender and the receiver can be reduced, thereby making it possible to reduce the phenomenon, such as a failure in authentication, the absence or disturbance of audio or video output, or the like. 
         [0048]    Further, a TMDS signal output scheme and an InfoFrame packet output timing are set and adjusted only for a scheme corresponding to the type of the audio/video reception apparatus, and none of the other schemes (other types) is affected. 
         [0049]    Further, connectivity reverification may be performed only for a scheme that has been set and adjusted, so that a verification time can be significantly reduced as compared to that in the conventional art, leading to a reduction in development cost. 
         [0050]    Note that the TMDS signal output schemes and InfoFrame packet output timings selected by the TMDS switching section  115  are not limited to those shown in  FIG. 2A  to  FIG. 2D . 
         [0051]    Also, the method for determining the type of an audio/video reception apparatus that is performed by the type determining section  114  is not limited to that shown in  FIG. 3 . 
         [0052]      FIG. 5  is a diagram showing a configuration of the TMDS switching section  115 . In  FIG. 5 ,  501  to  504  indicate scheme storing devices  1  to  4  for storing information about TMDS signal output schemes and InfoFrame packet output timings,  505  and  506  indicate spare scheme storing devices  5  and  6  having the same function as that of the scheme storing devices  1  to  4 , and  510  indicates a scheme selecting device for selecting one to be used from the scheme storing devices  1  to  6 . 
         [0053]    The TMDS switching section  115 , when receiving information about the type of the audio/video reception apparatus  130  from the type determining section  114 , selects a TMDS signal output scheme and an InfoFrame packet output timing suitable for the audio/video reception apparatus  130 . For example, if the information indicates “television set”, the scheme storing device  1  of  FIG. 2A  storing the scheme A is selected. If the information indicates “projector”, the scheme storing device  2  of  FIG. 2B  storing the scheme B is selected. If the information indicates “AV amplifier”, the scheme storing device  3  of  FIG. 2C  storing the scheme C is selected. If the information indicates “unknown” or “DVI apparatus”, the scheme storing device  4  of  FIG. 2D  storing the scheme D is selected. After the scheme selection, the TMDS switching section  115  instructs the TMDS output section  113  to output a TMDS signal and an InfoFrame packet in accordance with the selected output scheme. 
         [0054]    The scheme storing devices  5  and  6  prepared as spares store output schemes suitable for types other than a television set, a projector, an AV amplifier and others (including a DVI apparatus) stored in the scheme storing devices  1  to  4 . Alternatively, the scheme storing devices  5  and  6  store output schemes for a peculiar television set, projector, AV amplifier and others (including a DVI apparatus) that cannot be supported by the output schemes stored in the scheme storing devices  1  to  4 . 
         [0055]    For example, there are assumed to be television sets manufactured by companies X, Y and Z. It is also here assumed that the television sets of the company X and Y can be supported by the scheme A stored in the scheme storing device  1 , and the television set of the company Z is supported by none of the schemes. In this case, information about a TMDS signal output scheme and an InfoFrame packet output timing dedicated to the television set of the company Z is stored in the scheme storing device  5 . In addition, the type determining section  114  is provided with an additional process of determining whether the type of the audio/video reception apparatus  130  is the television set of the company Z. 
         [0056]    Instead of time adjustment of the scheme A for the type “television set”, the information about the TMDS signal output scheme and the InfoFrame packet output timing dedicated to the television set of the company Z is additionally provided, so that reverification is not required for television sets that conventionally do not have a problem. 
         [0057]    As described above, a spare scheme storing device for storing a TMDS signal output scheme and an InfoFrame packet output timing is additionally provided, so that a peculiar apparatus, type or the like can be flexibly supported, thereby making it possible to improve the quality of connectivity of the audio/video transmission apparatus. 
         [0058]    Further, connectivity reverification may be performed only with respect to an additional scheme, so that a time required for connectivity verification does not significantly increases and therefore development cost is reduced. 
         [0059]    Note that the number of scheme storing devices is not limited to that of  FIG. 5 , and may be appropriately prepared, depending on the specifications of the audio/video transmission apparatus. 
         [0060]    Incidentally, as shown in  FIG. 1  with a dot-dashed line, each output scheme stored in the TMDS switching section  115  can be rewritten by the rewrite section  124 . The input section  121  is used to input information about how rewriting is to be performed, information about which of the scheme storing devices  1  to  6  included in the TMDS switching section  115  is to be rewritten, or the like. As the rewrite section  124 , a method of obtaining update information from the communications network  190  and performing rewriting, and a method of performing rewriting using a CD or DVD medium on which update information is written, are prepared. 
         [0061]    When the communications network  190  is used, the audio/video transmission apparatus  100  needs to be previously connected to the communications network  190 . The input section  121  instructs the rewrite section  124  to access a designated web site, download latest information about a TMDS signal output scheme and an InfoFrame packet output timing, and write the information to a designated scheme storing device i (i= 1  to  6 ). The rewrite section  124  operates in accordance with the instruction. 
         [0062]    When a CD or DVD medium is used, the input section  121  instructs the audio/video recording/reproducing section  123  to read update information written on the CD or DVD medium and transmit the information to the rewrite section  124 , and instructs the rewrite section  124  to write update information from the audio/video recording/reproducing section  123  to a designated scheme storing device i (i= 1  to  6 ). The rewrite section  124  operates in accordance with the instruction. 
         [0063]    As described above, with the configuration of  FIG. 1 , a TMDS signal output scheme and an InfoFrame packet output timing can be easily rewritten by various means, so that the maintainability of the apparatus can be improved. 
         [0064]    Note that when the audio/video transmission apparatus  100  supports reading and writing of a compact storage medium, such as an SD card or the like, the audio/video transmission apparatus  100  can cause the rewrite section  124  to perform a rewrite operation using information stored in the compact storage medium, as is similar to the case of a CD or DVD medium. 
         [0065]    Further, a remote controller or the like accompanying the audio/video transmission apparatus  100  may be used to adjust a TMDS signal output scheme and an InfoFrame packet output timing. Thus, the rewrite section  124  is not limited to that described above. 
         [0066]    As described above, the audio/video transmission apparatus of the present invention is useful for home-use audio/video apparatuses, such as a DVD player, a DVD recorder, a hard disk recording/reproducing apparatus, an AV amplifier, and the like.