Abstract:
A signal output apparatus automatically determines which of a plurality of signals output from an apparatus is effective, and outputs the effective signal. For this purpose, the signal output apparatus comprises an output signal inquiring section configured to inquire an apparatus which outputs a plurality of kinds of signals about a kind of a signal output therefrom, an effective input signal determining section configured to determine which of a plurality of signals output from the apparatus is an effective input signal based on a result of inquiry by the output signal inquiring section, and a data outputting section configured to output data corresponding to the effective input signal based on a result of determination by the effective input signal determining section.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-224277, filed Jul. 25, 2000, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a signal output apparatus and a signal output method applied to an apparatus that deals with a plurality of kinds of signals. More particularly, the present invention relates to a signal output apparatus and a signal output method in an apparatus on a network utilizing an IEEE 1394 interface.  
           [0003]    The IEEE 1394 interface has engaged the public attention as a digital interface for constituting a network in a home. The IEEE 1394 is a high-speed serial bus interface, which has an asynchronous transfer mode and an isochronous transfer mode. In the isochronous transfer mode, a constant transfer rate is ensured. Therefore, the IEEE 1394 serial bus is suitable for transfer of a digital video signal or the like, which requires real-time processes.  
           [0004]    The conventional art of the network system having the IEEE 1394 interface includes, for example, a media-contents management AV system disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-120666.  
           [0005]    An analog video signal line is also widely used to transfer video signals in real time. Therefore, digital equipment having the IEEE 1394 interface, for example, a digital video recorder, generally enables not only IEEE 1394 digital output but also analog video output.  
           [0006]    It is assumed that a set-top box (STB) including the IEEE 1394 interface and a digital video recorder (DVHS or the like) are connected by both an IEEE 1394 serial bus cable and an analog video cable.  
           [0007]    In this case, when the digital video recorder (output device) playing back material recorded in a videotape reproduces a digital record program, a reproduction output signal on the digital interface side is effective. When the output device reproduces an analog record program, a reproduction output signal on the analog interface side is effective. For this reason, the STB, which receives both digital and analog reproduction outputs, is required to suitably select an effective signal and output the selected effective signal as display data on a display device (e.g., a digital TV).  
           [0008]    In the structure described above, the STB may generally output a signal input on the digital interface side as display data, and if a signal input on the analog interface side is effective, the STB may display on the screen of the display device a message, such as “Under analog reproduction. Switch to an analog input”. With this message, the user is prompted to perform an input switching operation, if an analog signal is effective.  
           [0009]    The reason for performing the above operation is that if the STB has a plurality of analog video input terminals, it is difficult to automatically switch from a digital input to a specific analog input, since only the user who connected the cables knows which terminal receives a desired analog signal.  
           [0010]    It is assumed that an apparatus (DVHS or the like) can record/reproduce data in/from both an analog source and digital source and output both analog and digital signals, that outputs from the apparatus are input to, for example, the STB, and that any one of the inputs is output from the STB as display data. In this case, when input is switched from the digital side to the analog side, if there is a plurality of analog input terminals, it is difficult to automatically specify to what input terminal a desired analog signal is input. Therefore, there is no other choice but to make the user to manually switch the input signals.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    The present invention was made in consideration of the above situation. A first object of the present invention is to provide a signal output apparatus for automatically determining which of a plurality of signals output from an apparatus is effective and outputting the effective signal.  
           [0012]    A second object of the present invention is to provide a signal output method for automatically determining which of a plurality of signals output from an apparatus is effective and outputting the effective signal.  
           [0013]    To achieve the first object, a signal processing apparatus of the present invention comprises: an output signal inquiring section configured to inquire an apparatus which outputs a plurality of kinds of signals about a kind of a signal output therefrom; an effective input signal determining section configured to determine which of a plurality of signals output from the apparatus is an effective input signal based on a result of inquiry by the output signal inquiring section; and a data outputting section configured to output data corresponding to the effective input signal based on a result of determination by the effective input signal determining section.  
           [0014]    The signal processing apparatus may further comprise an input setting storing section configured to set a specified input in advance and store input information of the set specified input. In this case, the effective input signal determining section may be configured to determine which of the plurality of signals is effective based on the input information stored in the input setting storing section; and the data outputting section may be configured to output data corresponding to the input information stored in the input setting storing section.  
           [0015]    To achieve the second object, a signal processing method of the present invention comprises the steps of: inquiring an apparatus which outputs a plurality of kinds of signals (digital/analog) about a kind of the signal output therefrom; determining which of a plurality of signals (digital/analog) output from the apparatus is an effective input signal based on a result of the inquiring step; and outputting data corresponding to the effective input signal based on a result of the determining step.  
           [0016]    The signal processing method may further comprise the step of setting a specified input in advance and storing input information of the set specified input. In this case, the determining step is configured to determine which of the plurality of signals is effective based on the input information stored in the setting and storing step; and the outputting step is configured to output an input signal corresponding to the input information stored in the setting and storing step.  
           [0017]    Further, a signal processing method of the present invention comprises the steps of: setting a specified analog input in advance and storing input information of the set specified analog input; inquiring an apparatus which outputs a plurality of kinds of signals, which can be digital and analog, about a kind of the signal output from the apparatus; determining which of the plurality of signals (digital/analog) output from the apparatus is an effective input signal based on a result of the inquiring step; and outputting data corresponding to the effective input signal based on a result of the determining step. In this method, even if the effective input signal is a digital signal (a DV signal or the like), if an apparatus which receives the data output by the outputting step is not adapted for the digital signal (the DV signal or the like) but adapted for an analog signal, a signal corresponding to the analog input set in advance in the setting and storing step is output by the outputting step.  
           [0018]    If the effective input signal is a digital signal (an MPEG2 transport stream or the like) and the apparatus which receives the data output by the outputting step is adapted for the digital signal (the MPEG2 transport stream or the like), data corresponding to the digital signal determined to be effective by the determining step is output by the outputting step.  
           [0019]    According to the apparatus or method as described above, it is possible to automatically determine which of a plurality of signals output from the apparatus is effective and also to output the automatically selected signal as display data. Thus, the complexity (troublesomeness) of an input signal switching operation by the user can be decreased and the operability for the user can be improved.  
           [0020]    Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0021]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
         [0022]    [0022]FIG. 1 is a block diagram for explaining an outline of a signal output apparatus according to an embodiment of the present invention;  
         [0023]    [0023]FIG. 2 is a block diagram for explaining functions of an STB used in the apparatus shown in FIG. 1 with reference to an internal structure of the STB;  
         [0024]    [0024]FIG. 3 is a flowchart for explaining an example of a process for determining an effective signal in the system of the embodiment; and  
         [0025]    [0025]FIG. 4 is a flowchart for explaining another example of a process for determining an effective signal in the system of the embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    A signal output apparatus and a signal output method according to an embodiment of the present invention will be described with reference to the accompanying drawings.  
         [0027]    [0027]FIG. 1 is a block diagram for explaining an outline of a signal output apparatus according to an embodiment of the present invention. In this embodiment, a set-top box (STB)  10  comprises a TV tuner section  10 A ready for digital and analog broadcasts, a switcher section  10 B, a control-oriented microcomputer (MPU/ROM/RAM)  10 C, etc.  
         [0028]    The STB  10  incorporates an IEEE 1394 interface (IEEE 1394 I/F)  110  in which processing functions of the IEEE 1394 are integrated, and the microcomputer  10 C, which includes the ROM storing a control program (firmware) for performing various apparatus controls. The firmware can be executed by the MPU in the microcomputer  10 C.  
         [0029]    The IEEE 1394 I/F  110  in the STB  10  is networked to at least one IEEE 1394-compliant apparatus (another apparatus equipped with an IEEE 1394 I/F) through an IEEE 1394 serial bus. In the drawing, a digital recording apparatus (a DVHS, a digital video (DV), a DVD-RAM recorder, a DVD streamer or the like)  20  is illustrated as an example of the IEEE 1394-compliant apparatus networked to the STB  10 . The digital recording apparatus  20  can record and reproduce stream data (an MPEG  2  transport stream) of a digital broadcast without converting it. The digital recording apparatus  20  is constructed to not only digital-output a recorded TV program as an MPEG  2  transport stream but also convert the recorded stream by means of DAC into an analog video signal and output the converted analog signal.  
         [0030]    The switcher section  10 B is connected to the IEEE  1394  I/F  110  serving as an interface for establishing network connection with another apparatus, and analog video input terminals  111  to  113 . The switcher section  10 B is constructed to select either a digital signal from the IEEE 1394 I/F  110  or an analog signal from the analog video input terminal  111 ,  112  or  113  by an operation of the user or under the control of the MPU, and output (supply) the selected signal to an external display apparatus (a digital TV, a monitor display, etc. with digital and analog input terminals)  30 .  
         [0031]    The display apparatus  30  has at least one of, for example, D 1  to D 5  terminals, as a digital video input terminal. It also has a composite video terminal and an S terminal as analog video terminals. A digital output from the switcher section  10 B is supplied to the digital video input terminal of the display apparatus  30 . An analog output from the switcher section  10 B is supplied to the analog video input terminal of the display apparatus  30 .  
         [0032]    The ROM in the control-oriented microcomputer  10 C stores programs corresponding to the processes shown in FIG. 3 or  4  (to be described later) as firmware (adapted to the functional blocks shown in FIG. 2). The MPU in the microcomputer  10 C executes the firmware in the ROM using the internal RAM as a work memory, thereby controlling the switching operation of the switcher section  10 B.  
         [0033]    In the embodiment shown in FIG. 1, the digital recording apparatus (a DVHS, a digital video (DV), a DVD-RAM recorder, a DVD streamer or the like)  20  is used as an example of another apparatus connected to the STB  10 . The recording apparatus  20  incorporates an IEEE 1394 I/F (not shown), which is connected to the IEEE 1394 I/F of the STB  10  through an IEEE 1394 serial bus cable. An analog video output from the recording apparatus  20  is connected to, for example, the video input terminal  112  of the STB  10  through an analog video cable.  
         [0034]    An IEEE 1394-compliant digital apparatus (a DVD streamer, a video editor, a digital TV or the like), which is not shown, can also be networked to the IEEE  1394  I/F  110  of the STB  10 . Further, another analog video apparatus (a video output of an analog VCR, an analog video output of a DVD video player, etc.), which is not shown, can be connected to the video input terminals  111  and  113  of the STB  10 .  
         [0035]    The user&#39;s operation with respect to the STB  10  (turning on/off of the power source, designating or channel-selection switching of a reception channel of the tuner section  10 A, switching of internal connection of the apparatus by the switcher section  10 B or switching of an external input terminal) is executed by an operation panel (not shown) of the main body of the STB  10  or an instruction apparatus such as a remote control unit ( 12  in FIG. 2).  
         [0036]    Assuming that the digital recording apparatus  20  is a digital video tape recorder (DVHS), a tape on which both digital and analog recording programs are recorded is replayed as follows.  
         [0037]    First, the user sets an analog video input terminal  112  (video input  2 ), to which the DVHS  20  is analog-connected, by means of a user interface of the STB  10 .  
         [0038]    After the replay of the tape is started, the STB  10  periodically issues an output signal inquiry command (one of AV/C commands), which can be transmitted through the IEEE 1394 serial bus, in order to monitor whether an analog or digital program is currently replayed. Based on the monitoring, the STB  10  determines which of the IEEE 1394 I/F or the video input  2  receives an effective signal (a signal to be transmitted to the display apparatus). In accordance with the determination result, the STB  10  can always output an effective signal to the display apparatus (digital TV or the like)  30  as display data.  
         [0039]    The IEEE 1394 I/F  110  allows the networked apparatus to confirm what kind of machine is connected to the other end of the line.  
         [0040]    For example, the apparatus (DVHS)  20  can obtain the following information on the other apparatus (STB)  10  through the IEEE 1394 serial bus:  
         [0041]    The STB  10  has an ID: XXX . . . XXX, a vendor name: T Corporation, and a model name: ABC; and  
         [0042]    It has a tuner-sub unit.  
         [0043]    Likewise, the apparatus (STB)  10  can obtain the following information on the other apparatus (DVHS)  20 :  
         [0044]    The apparatus (DVHS)  20  has an ID: YYY . . . YYY, the vendor name: V Corporation, and a model name: XYZ; and  
         [0045]    It has a tuner sub-unit and a tape recorder/player sub-unit.  
         [0046]    The STB  10 , which has obtained the above information, can exchange data with the DVHS  20  using a predetermined channel number by means of isochronous transfer (or asynchronous transfer).  
         [0047]    In the IEEE 1394 I/F, the following items are determined after the interface is reset before it is ready for normal packet transfer:  
         [0048]    (1) Nodes connected to the IEEE 1394 bus (the parentage of the nodes is determined);  
         [0049]    (2) A root node (in this case, the STB  10  is a root node);  
         [0050]    (3) Self-identification (in this case, the node IDS of the STB and the DVHS are determined);  
         [0051]    (4) An isochronous resource manager;  
         [0052]    (5) A cycle master; and  
         [0053]    (6) A bus manager.  
         [0054]    When the nodes (of the STB and the DVHS) connected to the IEEE 1394 bus are determined, normal packet transfer (isochronous transfer or asynchronous transfer) is started.  
         [0055]    The isochronous transfer is a system for transferring and receiving data in a constant cycle (125 μs). According to the format of a packet subjected to isochronous transfer, a channel number is given but an ID of a forwarding address is not. The asynchronous transfer is a system for transmitting and receiving data at any given time. An AV/C command can be transferred by utilizing the asynchronous transfer. An AV data body (an MPEG  2  transport stream, etc.) can be transferred by utilizing the isochronous transfer.  
         [0056]    The IEEE 1394 communication controllers (IEEE 1394 I/Fs  110 ) included in the respective apparatuses are provided with hardware and software necessary for the processes (determination of the above items, etc.) of the IEEE 1394 I/Fs.  
         [0057]    [0057]FIG. 2 is a block diagram for explaining functions of an STB used in the apparatus shown in FIG. 1 with reference to an internal structure of the STB. Referring to the drawing, a digital output from the digital recording apparatus (a DVHS, a digital video (DV), a DVD-RAM recorder, a DVD streamer or the like)  20  is connected to the IEEE 1394 I/F  110  through the IEEE 1394 serial bus cable. An analog output from the apparatus  20  is connected to the video input terminal  112  of the video input  2  through the analog video cable.  
         [0058]    The user determines to use, for example, the video input  2  for analog signal input by operating the instruction apparatus (remote control unit or the like)  12 , while observing a menu (not shown) displayed on the screen of the display apparatus (digital TV or the like)  30 . This determining operation is executed by an instruction input detecting section (remote control receiver)  102  and an analog input terminal setting section  104 . The setting information of the determined video input  2  is stored in a setting information storing section  106  provided in the work RAM (or an EEPROM not shown) of the microcomputer  10 C shown in FIG. 1.  
         [0059]    An output signal inquiring section  108  transmits an AV/C command for inquiring an output signal mode to the digital recording apparatus  20  via the IEEE 1394 I/F  110 . Based on a response to the inquiry command from the apparatus  20 , the IEEE 1394 I/F  110  obtains currently output signal information from the apparatus  20  (whether the signal is digital or analog). The currently output signal information is supplied to an effective input signal determining section  120  along with the video input setting information stored in the setting information storing section  106 .  
         [0060]    The effective input signal determining section  120  determines whether an analog signal or a digital signal is an effective signal based on the currently output signal information supplied from the IEEE 1394 I/F.  
         [0061]    When the effective input&#39;signal determining section  120  determines that a digital signal is an effective signal, the digital signal input to the IEEE  1394  I/F  110  is determined to be an effective signal, and an output switch instruction for outputting the digital signal to the display apparatus  30  is supplied to a display data outputting section  122 . Then, the display data outputting section  122  supplies the digital signal (for example, an MPEG  2  transport stream) from the IEEE 1394 I/F  110  to a digital terminal of the display apparatus (digital TV)  30  as display data.  
         [0062]    On the other hand, when the effective input signal determining section  120  determines that an analog signal is an effective signal, the analog video signal input to the video input terminal  112  of the video input  2  is determined to be an effective signal based on the video input setting information stored in the setting information storing section  106 . Then, an output switch instruction, for outputting the analog video signal from the video input  2  to an analog terminal of the display apparatus  30 , is given to the display data outputting section  122 .  
         [0063]    [0063]FIG. 3 is a flowchart for explaining an example of a process for determining an effective signal in the system of this embodiment. The process illustrated in the flowchart can be executed by the microcomputer  10 C shown in FIG. 1.  
         [0064]    First, the user sets the video input terminal (the video input  2  in FIGS. 1 and 2) as a terminal for receiving an analog output from the output apparatus (digital recording apparatus such as a DVHS)  20  (step ST 10 ). The setting process corresponds to the function of the analog input terminal setting section  104  shown in FIG. 2.  
         [0065]    Then, the output signal inquiring section  108  shown in FIG. 2 issues an inquiry command (AV/C command “MEDIUM INFO”) and supplies it to the output apparatus  20  via the IEEE 1394 I/F  110 . As a result, it is checked whether the apparatus  20  is loaded with a tape (video cassette) (step ST 12 ).  
         [0066]    When the tape is loaded in a tape transport of the apparatus  20  (step ST 14 , YES), the transport state (a replay, fast-forward, fast-reverse or a pause) is examined (step ST 16 ). This examination can be performed by issuance of an inquiry command (AV/C command “TRANSPORT STATE”) by the output signal inquiring section  108  and supply of the command to the output apparatus  20  via the IEEE 1394 I/F  110 .  
         [0067]    If the transport of the apparatus  20  is performing a reply operation (step ST 18 , YES), the output signal inquiring section  108  issues an inquiry command (AV/C command “OUTPUT SIGNAL MODE”) and supplies it to the output apparatus  20  via the IEEE 1394 I/F  110 . As a result, it is determined whether the content recorded on the tape replayed by the apparatus  20  is a digital record or an analog record (step ST 20 ).  
         [0068]    In the step ST 20 , at the same time, a digital signal format (an MPEG transport stream or a digital video bit stream) may be checked by an AV/C command “OUTPUT PLUG SIGNAL FORMAT” for setting and inquiring the signal format of an output plug. Alternatively, in the step ST  20 , at the same time, the content of a packet header of the digital stream input to the IEEE  1394  I/F  110  may be checked, so that the signal format can be examined.  
         [0069]    If the content of the record replayed by the apparatus  20  is an analog record (or even if a digital record is replayed, if an ADC and a DAC are arranged at the input and the output and a record signal is input and output in analog form), the apparatus  20  does not output a digital signal but outputs an analog signal (step ST 22 , “ANALOG”). In this case, it is determined that the analog signal in the video input  2  set in the step ST 10  is an effective signal (step ST 24 ). The analog signal determined to be effective is output to the display apparatus (digital TV or the like)  30  from the display data outputting section  122  shown in FIG. 2 (step ST 28 ).  
         [0070]    On the contrary, if the content of the record replayed by the apparatus  20  is a digital record (if a digital bit stream is recorded and a record signal is input and output in digital form), the apparatus  20  outputs an analog signal and a digital signal (step ST 22 , “DIGITAL”). In this case, even if an analog signal of the same content is output from the apparatus  20 , it is determined that the digital signal input to the IEEE 1394 I/F  110  is an effective signal (step ST 26 ). The digital signal determined to be effective is output to the display apparatus (digital TV or the like)  30  from the display data outputting section  122  (step ST 28 ).  
         [0071]    According to the process illustrated in FIG. 3, which of the analog inputs is used as an effective signal is stored in advance (step ST 10 ). Therefore, if it is determined that an analog&#39;signal is an effective signal, the analog signal intended by the user can be automatically selected and output.  
         [0072]    [0072]FIG. 4 is a flowchart for explaining another example of a process for determining an effective signal in the system of the embodiment. Steps ST 10  to ST 22  and ST  28  illustrated in FIG. 4 are the same as the steps ST 10  to ST 22  and ST  28  illustrated in FIG. 3. Therefore, in the following, steps ST 24  to ST 26 , which are different from the process shown in FIG. 3, will be described mainly.  
         [0073]    In the case where the output apparatus  20  can output digital signals of various formats (a MPEG  2  transport stream, a bit stream of a digital video DV, a bit stream of a DVD streamer, etc.), if the display apparatus (data receiving apparatus)  30  is not adapted for the output digital signal format (step ST 25 , NO), for example, if the display apparatus  30  has only analog inputs or it is adapted for a MPEG  2  transport stream but not a DV bit stream, then, even if a digital signal (a DV bit stream) is input to the IEEE 1394 I/F  110 , the analog signal is determined to be an effective signal (step ST 24 ). In this case, the analog signal at the analog video input terminal (video input  2 ) set in the step ST 10  is output to the display apparatus  30  from the display data outputting section  122  shown in FIG. 2 (step ST 28 ). Alternatively, the digital signal (DV bit stream), which cannot be dealt with by the display apparatus  30 , is converted to an analog signal by a DAC (not shown) and the converted analog signal is output to the display apparatus  30  from the display data outputting section  122  (step ST 28 ).  
         [0074]    In the case where a digital signal is output from the output apparatus  20 , if the display apparatus  30  is adapted for the digital signal (step ST 25 , YES), it is determined that the digital signal is an effective signal (step ST 26 ). The digital signal determined to be effective is output to the display apparatus (digital TV or the like)  30  from the display data outputting section  122  (step ST 28 ).  
         [0075]    In the step ST 22 , if a digital signal and an analog signal are simultaneously output from the same apparatus (DVHS or the like)  20 , the digital signal is given a higher priority by default; therefore, the digital signal is determined to be effective. However, it is possible that the user selects a digital or analog signal from the menu screen (not shown) of the STB  10 , so that the selected one is given a higher priority and determined to be effective by default. In a certain case, after a digital stream is D/A converted to an analog signal, OSD data or the like is superposed on this analog signal. In this case, if the digital signal is selected as effective, the OSD data cannot be displayed. Therefore, it is meaningful that the user can select an analog priority mode.  
         [0076]    According to the process illustrated in FIG. 4, which of the analog inputs is used as an effective signal is stored in advance (step ST 10 ). Therefore, if it is determined that an analog signal is effective, the analog signal intended by the user can be automatically selected and output. In addition, in the case where a digital signal is determined to be effective, if the receiver side for receiving the digital signal is not adapted for the format of the digital signal, an analog signal corresponding to the digital signal can be automatically output.  
         [0077]    The present invention is not limited to the above embodiment, but variations and modifications can be made within the scope of the gist of the invention, when the invention is implemented. Further, variations and modifications may be suitably combined so far as possible. In this case, an advantage can be obtained by the combination.  
         [0078]    Further, the above embodiment includes various stages of the invention. Therefore, various inventions can be extracted by a suitable combination of the features disclosed by this application. For example, even if one or more features are deleted from all the features of the embodiment, if the advantage of the present invention is obtained, the structure with the remaining features may be extracted as an invention.  
         [0079]    As has been described above, according to the signal output apparatus or the signal output method of the present invention, it is possible to automatically select one of the signals output from the apparatus ( 20 ) as an effective signal, and also to output the automatically selected signal as display data. Thus, the complexity (troublesomeness) of an input signal switching operation by the user can be decreased and the operability for the user can be improved.  
         [0080]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.