Abstract:
There are provided first channel searching means for sequentially tuning in to broadcasting channels using an analog broadcasting receiving unit, judging whether or not analog broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to analog broadcasting in a channel map with respect to the broadcasting channel on which analog broadcasting is judged to be receivable, and second channel searching means for sequentially tuning in to the broadcasting channels excluding the broadcasting channel on which analog broadcasting is judged to be receivable by the first channel searching means using a digital broadcasting receiving unit, judging whether or not digital broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to digital broadcasting in the channel map with respect to the broadcasting channel on which digital broadcasting is judged to be receivable.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a broadcasting receiver comprising the function of receiving an analog television broadcasting signal and a ground wave digital television broadcasting signal and a channel searching method in the broadcasting receiver.  
           [0003]    2. Description of the Prior Art  
           [0004]    In recent years, ground wave digital television broadcasting has been developed. The transition from current analog broadcasting to digital broadcasting is being made. A period of the transition may include a time period during which both analog broadcasting and digital broadcasting are mixed. A television receiver requires a function capable of receiving both analog broadcasting and digital broadcasting. Therefore, a television receiver carrying both a tuner for receiving digital broadcasting and a tuner for receiving analog broadcasting has been developed.  
           [0005]    In the period of the transition from analog broadcasting to digital broadcasting, it has been expected that a channel map is frequently changed as an analog station is abolished and a digital station is newly opened. Therefore, a receiver is required to make an efficient channel search.  
           [0006]    On the other hand, in both analog broadcasting and digital broadcasting, smooth channel selection can be carried out by previously recognizing on which channel (frequency) broadcasting is being performed in the case of receiving, that is, on which channel broadcasting is receivable. Channels on which broadcasting is being performed differ for each area. Therefore, a channel map is produced by making a search (channel search) over all channels to determine on which channel and with which system (analog or digital broadcasting system) broadcasting is being performed when a receiver is installed.  
           [0007]    The channel search is made by sequentially tuning in to channels with respect to each of a tuner for analog broadcasting and a tuner for digital broadcasting and judging whether or not broadcasting is being performed on the channel based on whether or not a normal signal to be received can be obtained from the tuner.  
           [0008]    Description is now made of the conventional channel searching operation of a broadcasting receiver comprising the function of receiving both digital broadcasting and analog broadcasting using FIG. 1.  
           [0009]    [0009]FIG. 1 illustrates the configuration of a broadcasting receiver comprising the function of receiving both digital broadcasting and analog broadcasting.  
           [0010]    A microcomputer  300  receives, through a remote control signal receiver  301  for receiving an operation signal transmitted by radio from a remote control  401  or a main body operation key  302 , the operation signal. The microcomputer  300  starts a channel searching operation by receiving an operation signal representing a channel search command.  
           [0011]    The microcomputer  300  outputs to a digital tuner  101  a channel selection instruction for tuning in to a channel having the lowest frequency on which broadcasting may be performed when it receives the operation signal representing the channel search command. Out of signals inputted to the digital tuner  101  from a ground wave broadcasting antenna  100 , the signal selected by the digital tuner  101  is inputted to a digital demodulator  102 , and is subjected to demodulation processing conforming to a modulation system. Generally, a digital TV broadcasting signal is subjected to OFDM (Orthogonal Frequency Demodulation Multiplexing) modulation, for example, and is subjected to OFDM demodulation by the digital demodulator  102 .  
           [0012]    If a normal signal is broadcast, it is outputted as an MPEG (Motion Picture Expert Group) transport stream after being previously subjected to processing for error correction. The demodulated MPEG transport stream is subjected to decoding processing by a TS decoder  103 , and is outputted as elementary streams such as a video, an audio, etc., so that a video signal and an audio signal are restored by a video/audio decoder  104 .  
           [0013]    The microcomputer  300  judges whether or not a normal digital signal is received on the channel which the digital tuner  101  is instructed to tune in to on the basis of the state of the digital demodulator  102 . Specifically, it is judged whether or not the normal signal is broadcast depending on whether or not the digital demodulator  102  can establish synchronization of the received digital signal. However, a method of judging whether or not the normal digital signal is received is not necessarily limited to the same.  
           [0014]    Information such as a broadcasting station name sent from a broadcasting station is acquired on the basis of data obtained by the TS decoder  103 . The presence or absence of broadcasting may be judged depending on whether or not the broadcasting station name can be specified. When it is judged that the normal digital signal is received, the microcomputer  300  stores in a memory  303  information for channel selection (receivable channel information) such as a frequency, a broadcasting station name, and a channel number.  
           [0015]    The microcomputer  300  then outputs an instruction to tune in to a channel on the high frequency side adjacent to the current channel, for example. The microcomputer  300  judges whether or not the normal digital signal is received on the channel tuned in to in the same manner as described above, and stores in the memory  303  information for channel selection (receivable channel information) such as a frequency, a broadcasting station name, and a channel number when it is judged that the normal digital signal is received. Such an operation is repeated over all channels, to store in the memory  303  receivable channel information indicating on which channel broadcasting is being performed.  
           [0016]    A channel search for analog broadcasting is similarly made. That is, an instruction to tune in to a channel having the lowest frequency on which broadcasting may be performed from the microcomputer  300  to an analog tuner  201 . Out of signals inputted to the analog tuner  201  from the ground wave broadcasting antenna  100 , the signal selected by the analog tuner  201  is inputted to an analog demodulator  202 , and is subjected to demodulation processing. The demodulated signal is outputted as a composite video signal or audio signal.  
           [0017]    The demodulated analog composite video signal is inputted to a detector  203 . The detector  203  outputs to the microcomputer  300  a judgment signal indicating whether or not a synchronizing signal can be detected from the video signal demodulated by the analog demodulator  202 . The microcomputer  300  judges whether or not a normal video signal is demodulated on the basis of the judgment signal. The microcomputer  300  may judge whether or not the normal video signal is demodulated depending on whether or not a PLL (Phase Locked Loop) synchronizing circuit is locked (the tuner is locked). However, a method of judging whether or not the normal video signal is demodulated is not necessarily limited to the same.  
           [0018]    The microcomputer  300  stores, when it judges that the normal video signal is demodulated, information for channel selection (receivable channel information) such as a channel frequency and a channel number in the memory  303 , and outputs a channel selection instruction using the adjacent channel on the high frequency side as the subsequent channel. The same operation is repeated over all the channels, to store in the memory  303  receivable channel information indicating on which channel broadcasting is being performed.  
           [0019]    At the time of a normal operation, the microcomputer  300  receives a channel selection instruction from a user through the remote control signal receiver  301  or the main body operation key  302 , and refers to data in the memory  303 , thereby outputting a channel selection instruction corresponding to the channel desired by the user to the digital tuner  101  or the analog tuner  201 .  
           [0020]    As described in the foregoing, in the channel search for digital broadcasting, it is judged whether or not a normal signal can be received, and it is necessary to confirm the contents of digital data in order to extract a broadcasting station name or the like. Therefore, it generally takes much time to judge whether or not broadcasting is being performed on the channel. Further, in Japanese ground wave digital broadcasting, there are a plurality of types of broadcasting modes, and all combinations of the modes must be tried. Therefore, it takes more time to make the judgment.  
           [0021]    Thus, the channel search for digital broadcasting requires more time than the channel search for analog broadcasting. When a channel search must be frequently made as in a period of transition to digital broadcasting, a viewer is forced to feel inconvenience.  
         SUMMARY OF THE INVENTION  
         [0022]    An object of the present invention is to solve the above-mentioned problem and to provide a broadcasting receiver capable of efficiently making a channel search and a channel searching method in the broadcasting receiver.  
           [0023]    In a broadcasting receiver comprising an analog broadcasting receiving unit for receiving an analog television broadcasting signal, a digital broadcasting receiving unit for receiving a digital television broadcasting signal, and a memory for storing a channel map storing receivable channel information such as the type of broadcasting for each of broadcasting channels, a broadcasting receiver according to the present invention is characterized by comprising first channel searching means for sequentially tuning in to the broadcasting channels using the analog broadcasting receiving unit, judging whether or not analog broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to analog broadcasting in the channel map with respect to the broadcasting channel on which analog broadcasting is judged to be receivable; and second channel searching means for sequentially tuning in to the broadcasting channels excluding the broadcasting channel on which analog broadcasting is judged to be receivable by the first channel searching means using the digital broadcasting receiving unit, judging whether or not digital broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to digital broadcasting in the channel map with respect to the broadcasting channel on which digital broadcasting is judged to be receivable.  
           [0024]    Each of the first channel searching means and the second channel searching means obtains the results of judgment whether or not broadcasting is receivable for each of the broadcasting channels tuned in to, and records the receivable channel information in the channel map every time the results of the judgment for one of the broadcasting channels are obtained.  
           [0025]    The second channel searching means refers to the channel map when a search for the given broadcasting channel is started, and omits, when the receivable channel information indicating that analog broadcasting is being performed on the broadcasting channel is stored in the channel map, the search for the broadcasting channel, to search for the subsequent broadcasting channel.  
           [0026]    The broadcasting channels are searched for in the same order when the respective channel searches by the first channel searching means and the second channel searching means are simultaneously started, and the channel map is not referred to on the broadcasting channel which starts to be first searched for by the second channel searching means.  
           [0027]    Each of the first channel searching means and the second channel searching means searches for the receivable broadcasting channels in ascending order of their frequencies, for example.  
           [0028]    Each of the first channel searching means and the second channel searching means searches for the receivable broadcasting channels in descending order of their frequencies, for example.  
           [0029]    The analog broadcasting receiving unit comprises an analog tuner for tuning in to a channel to be received and an analog demodulator for demodulating a signal on the channel tuned in to, and the first channel searching means Judges whether or not analog broadcasting is receivable depending on whether or not a horizontal synchronizing signal can be detected from a video signal demodulated by the analog demodulator, for example.  
           [0030]    The digital broadcasting receiving unit comprises a digital tuner for tuning in to a channel to be received and a digital demodulator for demodulating a signal on the channel tuned in to, and the second channel searching means judges whether or not digital broadcasting is receivable depending on whether or not the digital demodulator can establish synchronization of a received signal, for example.  
           [0031]    The digital broadcasting receiving unit comprises a digital tuner for tuning in to a channel to be received, a digital demodulator for demodulating a signal on the channel tuned in to, and a TS decoder for subjecting TS data obtained by the digital demodulator to separation processing, and the second channel searching means judges whether or not digital broadcasting is receivable depending on whether or not the broadcasting station can be recognized -from received data which has been subjected to decoding processing by the TS decoder, for example.  
           [0032]    In a case where broadcasting is received for viewing or recording using one of the analog broadcasting receiving unit and the digital broadcasting receiving unit, the broadcasting receiving unit which is not used for viewing or recording may be operated for a channel search, to search for channels by the first channel searching means or the second channel searching means corresponding to the operated broadcasting receiving unit.  
           [0033]    In a channel searching method in a broadcasting receiver comprising an analog broadcasting receiving unit for receiving an analog television broadcasting signal, a digital broadcasting receiving unit for receiving a digital television broadcasting signal, and a memory for storing a channel map storing receivable channel information such as the type of broadcasting for each of broadcasting channels, a channel searching method in a broadcasting receiver according to the present invention is characterized by comprising a first channel searching step for sequentially tuning in to the broadcasting channels using the analog broadcasting receiving unit, judging whether or not analog broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to analog broadcasting in the channel map with respect to the broadcasting channel on which analog broadcasting is judged to be receivable; and a second channel searching step for sequentially tuning in to the broadcasting channels excluding the broadcasting channel on which analog broadcasting is judged to be receivable in the first channel searching step using the digital broadcasting receiving unit, judging whether or not digital broadcasting is receivable for each of the broadcasting channels, and storing receivable channel information related to digital broadcasting in the channel map with respect to the broadcasting channel on which digital broadcasting is judged to be receivable.  
           [0034]    Each of the first channel searching step and the second channel searching step comprises the step of obtaining the results of judgment whether or not broadcasting is receivable for each of the broadcasting channels tuned in to, and recording the receivable channel information in the channel map every time the results of the judgment for one of the broadcasting channels are obtained.  
           [0035]    The second channel searching step comprises the step of referring to the channel map when a search for the given broadcasting channel is started, and omitting, when the receivable channel information indicating that analog broadcasting is being performed on the broadcasting channel is stored in the channel map, the search for the broadcasting channel, to search for the subsequent broadcasting channel.  
           [0036]    The broadcasting channels are searched for in the same order when the respective channel searches in the first channel searching step and the second channel searching step are simultaneously started, and the channel map is not referred to on the broadcasting channel which starts to be first searched for in the second channel searching step.  
           [0037]    Each of the first channel searching step and the second channel searching step comprises the step of searching for the receivable broadcasting channels in ascending order of their frequencies, for example.  
           [0038]    Each of the first channel searching step and the second channel searching step comprises the step of searching for the receivable broadcasting channels in descending order of their frequencies, for example.  
           [0039]    The analog broadcasting receiving unit comprises an analog tuner for tuning in to a channel to be received and an analog demodulator for demodulating a signal on the channel tuned in to, and the first channel searching step comprises the step of judging whether or not analog broadcasting is receivable depending on whether or not a horizontal synchronizing signal can be detected from a video signal demodulated by the analog demodulator, for example.  
           [0040]    The digital broadcasting receiving unit comprises a digital tuner for tuning in to a channel to be received and a digital demodulator for demodulating a signal on the channel tuned in to, and the second channel searching step comprises the step of judging whether or not digital broadcasting is receivable depending on whether or not the digital demodulator can establish synchronization of a received signal.  
           [0041]    The digital broadcasting receiving unit comprises a digital tuner for tuning in to a channel to be received, a digital demodulator for demodulating a signal on the channel tuned in to, and a TS decoder for subjecting TS data obtained by the digital demodulator to separation processing, and the second channel searching step comprises the step of judging whether or not digital broadcasting is receivable depending on whether or not the broadcasting station can be recognized from received data which has been subjected to decoding processing by the TS decoder.  
           [0042]    In a case where broadcasting is received for viewing or recording using one of the analog broadcasting receiving unit and the digital broadcasting receiving unit, the broadcasting receiving unit which is not used for viewing or recording may be operated for a channel search, to search for channels in the first channel searching step or the second channel searching step corresponding to the operated broadcasting receiving unit.  
           [0043]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]    [0044]FIG. 1 is a block diagram showing the configuration of a broadcasting receiver comprising the function of receiving both digital broadcasting and analog broadcasting;  
         [0045]    [0045]FIG. 2 is a flow chart showing the procedure for channel searching processing for analog broadcasting;  
         [0046]    [0046]FIG. 3 is a flow chart showing the procedure for channel searching processing for digital broadcasting;  
         [0047]    [0047]FIG. 4 a  is a timing chart showing the timing of a conventional channel search; and  
         [0048]    [0048]FIGS. 4 b  and  4   c  are timing charts showing the timing of a channel search according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0049]    Referring now to the drawings, an embodiment of the present invention will be described.  
         [0050]    In the present embodiment, the configuration of a broadcasting receiver (a hardware configuration) is also the same as the configuration of the conventional broadcasting receiver shown in FIG. 1.  
         [0051]    [0051]FIGS. 2 and 3 show the procedure for channel searching processing.  
         [0052]    [0052]FIG. 2 shows the procedure for channel searching processing for analog broadcasting.  
         [0053]    When a channel search is started (step S 101 ), a microcomputer  300  gives an instruction to tune in to a receivable channel having the lowest frequency to an analog tuner  201  (step S 102 ).  
         [0054]    The analog tuner  201  selects a broadcasting signal corresponding to the channel which it is instructed to tune in to (step S 103 ). The selected broadcasting signal is demodulated by an analog demodulator  202 . At this time, it is judged whether or not there is broadcasting depending on whether or not a synchronizing signal can be detected from the demodulated broadcasting signal (step S 104 ).  
         [0055]    When there is broadcasting (when a synchronizing signal can be detected by a detector  203 ), the microcomputer  300  stores in a channel map inside a memory  303  receivable channel information indicating that a channel currently tuned in to is a channel on which analog broadcasting is receivable (step S 105 ). The procedure proceeds to the step S 106 .  
         [0056]    When it is judged in the foregoing step S 104  that there is no broadcasting (no synchronizing signal is detected by the detector  203 ), the microcomputer  300  judges whether or not receivable channel information indicating whether or not the channel currently tuned in to in the channel map inside the memory  303  is a channel on which digital broadcasting is receivable is stored (step S 107 ).  
         [0057]    When the receivable channel information indicating that a channel currently tuned in to is a channel on which digital broadcasting is receivable is stored in the channel map, the microcomputer  300  does not rewrite data in the channel map, after which the procedure proceeds to the step S 106 . When the receivable channel information indicating that a channel currently tuned in to is a channel on which digital broadcasting is receivable is not stored in the channel map, the microcomputer  300  resets (erases) data related to the channel currently tuned in to in the channel map (step S 108 ), after which the procedure proceeds to the step S 106 .  
         [0058]    In the step S 106 , the microcomputer  300  judges whether or not a channel currently tuned in to is a receivable channel having the highest frequency. When the channel currently tuned in to is not a receivable channel having the highest frequency, the microcomputer  300  gives to the analog tuner  201  an instruction to tune in to a channel on the high frequency side adjacent to the channel currently tuned in to (step S 109 ).  
         [0059]    In the same manner as described above, a channel which the analog tuner  201  is newly instructed to tune in to is searched for (step S 103 ), to judge whether or not there is broadcasting (step S 104 ).  
         [0060]    When all receivable channels are searched for in such a way, and a search for the receivable channel having the highest frequency is terminated, the answer is in the affirmative in the step S 106 , to terminate the channel search for analog broadcasting (step S 110 ).  
         [0061]    [0061]FIG. 3 shows the procedure for channel searching processing for digital broadcasting.  
         [0062]    When a channel search is started (step S 210 ), the microcomputer  300  gives an instruction to tune in to a receivable channel having the lowest frequency to the digital tuner  101  (step S 202 ).  
         [0063]    The digital tuner  101  selects a broadcasting signal corresponding to the channel which it is instructed to tune in to (step S 203 ). The selected broadcasting signal is demodulated by the digital demodulator  102 , and is subjected to data separation processing by a TS (Transport Stream) decoder  103 . At this time, it is judged whether or not there is broadcasting depending on whether or not synchronization can be ensured and whether or not a broadcasting station can be recognized from output data from the TS decoder  103  by the status of the demodulator  102  (step S 204 ).  
         [0064]    When it is judged in the foregoing step S 204  that there is broadcasting (synchronization can be ensured and a broadcasting station can be recognized), receivable channel information indicating that the current channel is one on which digital broadcasting is performed, which broadcasting station is performing broadcasting, and what modulation system is used, for example, is stored in the channel map inside the memory  303  (step S 205 ). The procedure then proceeds to the step S 206 .  
         [0065]    When it is judged in the foregoing step S 204  that there is no broadcasting (no synchronization can be ensured or no broadcasting station can be recognized), it is judged whether or not receivable channel information indicating that a channel currently tuned in to is a channel on which analog broadcasting is receivable is stored in the channel map inside the memory  303  (step S 207 ).  
         [0066]    When the receivable channel information indicting that a channel currently tuned in to is a channel on which analog broadcasting is receivable is stored in the channel map, the microcomputer  300  does not rewrite data an the channel map, after which the procedure proceeds to the step S 206 . When the receivable channel information indicting that a channel currently tuned in to is a channel on which analog broadcasting is receivable is not stored in the channel map, the microcomputer  300  resets (erases) data related to the channel currently tuned in to in the channel map (step S 208 ), after which the procedure proceeds to the step S 206 .  
         [0067]    In the step S 206 , the microcomputer  300  judges whether or not a channel currently tuned in to is a receivable channel having the highest frequency. When the channel currently tuned in to is not a receivable channel having the highest frequency, the microcomputer  300  gives to the digital tuner  101  an instruction to tune in to a channel on the high frequency side adjacent to the channel currently tuned in to (step S 209 )  
         [0068]    It is judged whether or not receivable channel information indicating that a channel which the digital tuner  101  is newly instructed to tune in to is a channel on which analog broadcasting is receivable is stored in the channel map (step S 210 ).  
         [0069]    When the receivable channel information indicating that a channel which the digital tuner  101  is newly instructed to tune in to is a channel on which analog broadcasting is receivable is stored in the channel map, it is found that the channel has already been recognized as a channel on which analog broadcasting is receivable. Therefore, the microcomputer  300  does not search for the channel but gives to the digital tuner  101  an instruction to tune in to a channel on the high frequency side adjacent to the channel currently tuned in to (step S 209 ).  
         [0070]    When in the foregoing step S 210 , the receivable channel information indicating that a channel which the digital tuner  101  is newly instructed to tune in to is a channel on which analog broadcasting is receivable is not stored in the channel map, the channel is searched for in the same manner as described above (step S 203 ), to confirm the presence or absence of broadcasting (step S 204 ).  
         [0071]    When all receivable channels are searched for in such a way, and a search for the receivable channel having the highest frequency is terminated, the answer is in the affirmative in the step S 206 , to terminate the channel search for analog broadcasting (step S 110 ).  
         [0072]    Furthermore, channel searching processing will be specifically described using FIGS. 4a, 4b, and  4 c. For simplicity, description is made using an example in which a search is made between Channel  1  and Channel  12 . It is herein assumed that analog broadcasting and digital broadcasting are mixed, analog broadcasting is performed on each of Channels  1 ,  3 ,  4 ,  6 ,  8 , and  10 , and digital broadcasting is performed on each of Channels  2 ,  5 ,  7 , and  12 . Further, in this example, it is assumed that a channel search for analog broadcasting and a channel search for digital broadcasting are simultaneously started.  
         [0073]    Description is now made of an initial channel search for resetting a channel map and producing channel map data from the beginning. When a user designates a channel search, the initial channel search is made.  
         [0074]    The horizontal axis in FIGS. 4 a ,  4   b , and  4   c  represents time, and indicates how a search for each of channels proceeds. It is herein assumed that the judgment of the presence or absence of analog broadcasting requires one unit time period (e.g., one second) per channel, and the judgment of the presence or absence of digital broadcasting requires two unit time periods per channel.  
         [0075]    [0075]FIG. 4 a  illustrates a case where a channel search is made by the conventional method. FIG. 4 a  illustrates a channel search for analog broadcasting by the analog tuner  201  and a channel search for digital broadcasting by the digital tuner  101 . A numeral in a square represents the number of a channel which is being searched for. An underlined number indicates that the broadcasting is being performed on the channel. In the conventional example, even if the channel search for analog broadcasting and the channel search for digital broadcasting are simultaneously made, the searches are individually made. It takes longer to make a judgment in the channel search for digital broadcasting. Accordingly, it takes 24 unit time periods from time “0” to time “24” to search for Channels  1  to  12 .  
         [0076]    On the other hand, FIG. 4 b  illustrates a channel search according to the present invention. FIG. 4 b  also illustrates a channel search for analog broadcasting by the analog tuner  201  and a channel search for digital broadcasting by the digital tuner  101 . As in FIG. 4 a , a numeral in a square represents the number of a channel which is being searched for.  
         [0077]    [0077]FIG. 4 c  illustrates situations where the acquisition of channel map data proceeds at each time, where “A” indicates that analog broadcasting is being performed, and “D” indicates that digital broadcasting is being performed. A blank column indicates that a search is unfinished, and “-” indicates that neither analog broadcasting nor digital broadcasting is being performed.  
         [0078]    Description is now made of the procedure for channel searching processing using FIGS. 4 b  and  4   c.    
         [0079]    First, a search for analog broadcasting (hereinafter referred to as an analog search) and a search for digital broadcasting (hereinafter referred to as a digital search) are simultaneously started on Channel  1  at time “0”.  
         [0080]    At time “1”, it is judged that analog broadcasting is being performed on Channel  1  by the analog search, and “A” indicating that analog broadcasting is being performed is recorded in a column of Channel  1  in the channel map.  
         [0081]    In the analog search, the transition to a search for the subsequent Channel  2  occurs. In the digital search, the search for Channel  1  is being continued.  
         [0082]    At time “2”, it is judged that analog broadcasting is not being performed on Channel  2  by the analog search. Since the results of judgment on a digital search for Channel  2  have not been obtained yet, however, a column of Channel  2  in the channel map remains blank.  
         [0083]    In the analog search, the transition to a search for the subsequent Channel  3  occurs. Judgment on Channel  1  by the digital search is terminated, so that it is judged that digital broadcasting is not being performed on Channel  1 . Since “A” has already been recorded in the column of Channel  1  in the channel map, the column of Channel  1  in the channel map remains unchanged.  
         [0084]    In the case of the transition to a digital search for the subsequent Channel  2 , the column of Channel  2  in the channel map is confirmed. Since the column of Channel  2  in the channel map is a blank column, the digital search for Channel  2  is started.  
         [0085]    At time “3”, it is judged that analog broadcasting is being performed on Channel  3  by the analog search, and “An is recorded in a column of Channel  3  in the channel map. In the analog search, the transition to a search for the subsequent Channel  4  occurs. In the digital search, the search for Channel  2  is being continued.  
         [0086]    At time “4”, it is judged that analog broadcasting is being performed on Channel  4  by the analog search, and “A” is recorded in a column of Channel  4  in the channel map. In the analog search, the transition to a search for the subsequent Channel  5  occurs. Judgment on Channel  2  by the digital search is terminated, so that it is judged that digital broadcasting is being performed. Consequently, “D” meaning that digital broadcasting is being performed is recorded in the column of Channel  2  in the channel map and at the same time, channel information such as a broadcasting station name is also stored.  
         [0087]    In the case of the transition to a digital search for the subsequent Channel  3 , the column of Channel  3  in the channel map is confirmed. Since “A” is recorded in the column of Channel  3  in the channel map, the digital search for Channel  3  is not made, to confirm the column of Channel  4  in the channel map. Since “A” is also recorded in the column of Channel  4  in the channel map, a digital search for Channel  4  is not made, to confirm a column of Channel  5  in the channel map. Since the column of Channel  5  in the channel map is a blank column, a digital search for Channel  5  is started.  
         [0088]    At time “5”, it is judged that analog broadcasting is not being performed on Channel  5  by the analog search. Consequently, the column of Channel  5  in the channel map remains blank. In the analog search, the transition to a search for the subsequent Channel  6  occurs. In the digital search, the search for Channel  5  is being continued.  
         [0089]    At time “6”, it is judged that analog broadcasting is being performed on Channel  6  by the analog search, and “A” is recorded in a column of Channel  6  in the channel map. In the analog search, the transition to a search for the subsequent Channel  7  occurs. In the digital search, judgment on Channel  5  is terminated, so that it is judged that digital broadcasting is being performed. Consequently, “D” is recorded in the column of Channel  5  in the channel map and at the same time, channel information such as a broadcasting station name is recorded. In the case of the transition to a digital search for the subsequent channel, the next column in the channel map is confirmed. Since “A” has already been recorded in the column of Channel  6 , a digital search for Channel  6  is not made, to start a digital search for the subsequent Channel  7 .  
         [0090]    At time “7”, it is judged that analog broadcasting is not being performed on Channel  7  by the analog search. Consequently, a column of Channel  7  in the channel map remains blank. In the analog search, the transition to a search for the subsequent Channel  8  occurs. In the digital search, the search for Channel  7  is being continued.  
         [0091]    At time “8”, it is judged that analog broadcasting is being performed on Channel  8  by the analog search, and “A” is recorded in a column of Channel  8  in the channel map. In the analog search, the transition to a search for the subsequent Channel  9  occurs. In the digital search, the search for Channel  7  is terminated, so that it is judged that digital broadcasting is being performed on Channel  7 . Consequently, “D” is recorded in the column of Channel  7  in the channel map, and channel information such as a broadcasting station name is recorded. In the case of the transition to a digital search for the subsequent channel, the next column in the channel map is confirmed. Since “A” has already been recorded in the column of Channel  8 , a digital search for Channel  8  is not made, to start a digital search for the subsequent Channel  9 .  
         [0092]    At time “9”, it is judged that analog broadcasting is not being performed on Channel  9  by the analog search. Consequently, a column of Channel  9  in the channel map remains blank. In the analog search, the transition to a search for the subsequent Channel  10  occurs. In the digital search, the search for Channel  9  is being continued.  
         [0093]    At time “10”, it is judged that analog broadcasting is being performed on Channel  10  by the analog search, and “A” is recorded in a column of Channel  10  in the channel map. In the analog search, the transition to a search for the subsequent Channel  11  occurs. In the digital search, the search for Channel  9  is terminated, so that it is judged that digital broadcasting is not being performed on Channel  9 . Since the column of Channel  9  in the channel map is a blank column, “-” meaning that there is no station is recorded in the column. In the case of the transition to a digital search for the subsequent channel, the next column in the channel map is confirmed. Since “A” has already been recorded in the column of Channel  10 , a digital search for Channel  10  is not made, to start a digital search for the subsequent Channel  11 .  
         [0094]    At time “11”, it is judged that analog broadcasting is not being performed on Channel  11  by the analog search. Consequently, a column of Channel  11  in the channel map remains blank.  
         [0095]    In the analog search, the transition to a search for the subsequent Channel  12  occurs. In the digital search, the search for Channel  11  is being continued.  
         [0096]    At time “12”, it is judged that analog broadcasting is not being performed on Channel  12  by the analog search. Consequently, a column of Channel  12  in the channel map remains blank. Consequently, the analog search is terminated.  
         [0097]    The digital search for Channel  11  is terminated, so that it is judged that digital broadcasting is not being performed on Channel  11 . Since the column of Channel  11  in the channel map is a blank column, “-” meaning that there is no station is recorded in the column. In the case of the transition to digital judgment on the subsequent channel, the next column in the channel map is confirmed. Since the column of Channel  12  in the channel map is a blank column, a digital search for Channel  12  is started.  
         [0098]    At time “13”, the analog search has been terminated. In the digital search, the search for Channel  12  is being continued.  
         [0099]    At time “14”, the digital search for Channel  12  is terminated, so that it is judged that digital broadcasting is being performed on Channel  12 . Consequently, “D” is recorded in the column of Channel  12  in the channel map, and channel information such as a broadcasting station name is recorded therein. Consequently, the digital search is terminated.  
         [0100]    In this stage, the final channel map is completed. The completion of the channel map requires 14 unit time periods, which are made shorter than 24 unit time periods in the conventional method. Although description was herein made, assuming that the ratio of a time period required to judge the presence or absence of analog broadcasting to a time period required to judge the presence or absence of digital broadcasting is 1:2, an overall shortening effect is further increased in a case where it takes longer to judge digital broadcasting than analog broadcasting.  
         [0101]    When only a digital search for digital broadcasting is made in order to newly add digital broadcasting, a search time period can be similarly shortened by referring to a channel map which is already completed, to attempt to search for only channels other than a channel on which analog broadcasting is being performed.  
         [0102]    When either of the types of broadcasting is being viewed, a channel search is made using a tuner for the other type of broadcasting, thereby making it possible to also update the channel map. Specifically, while digital broadcasting is being received, an analog search is made, to update data related to an analog channel. When a channel on which it is judged that there is no analog broadcasting, as judged in the step S 107  shown in FIG. 2, has already been stored as one on which digital broadcasting is performed on the channel map, data related to the channel is not updated.  
         [0103]    On the other hand, while analog broadcasting is being viewed, a digital search is made, thereby making it possible to also update data related to a digital channel. The results of an analog search are given priority to, as judged in the steps S 207  and S 209  shown in FIG. 3, to neither make a digital search nor update data with respect to a channel which has been stored as one on which analog broadcasting is performed on the channel map.  
         [0104]    As described in the foregoing, the digital search requires more time than the analog search. In both cases where both the digital search and the analog search are simultaneously and separately made, therefore, the results of the analog search are given priority to and reflected on digital searching processing to omit the digital search for a channel on which it is found that analog broadcasting is performed, thereby making it possible to shorten a time period required to make the whole channel search. Although in the above-mentioned embodiment, an example in which channels are searched for in ascending order of their frequencies, the present invention is not limited to the same. For example, the channels may be searched for in descending order of their frequencies.  
         [0105]    Furthermore, the order of channels to be searched for is not limited to those in the above-mentioned examples. Consequently, the channel search may not be started on the highest-numbered channel or the lowest-numbered channel but may be started on the channels therebetween. For example, the order is Channels  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  1 ,  2 ,  3 ,  4 , and  5 . Further, the order of channels to be searched for may not be the order of channel numbers. That is, if the respective orders of channels to be searched for in analog broadcasting and digital broadcasting are the same, the orders may be in any form.  
         [0106]    According to the above-mentioned embodiment, the channel search for digital broadcasting is not made with respect to the channel on which it is judged that analog broadcasting exists. Therefore, a channel search time period can be shortened.  
         [0107]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.