JP2007295236A - Receiver, channel preset method, and program of digital broadcasting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver in which the channel of digital broadcasting can be preset quickly. <P>SOLUTION: The television receiver 1 comprises a means 10 for receiving the broadcasting signal of digital broadcasting which is broadcast using at least a strong layer and a weak layer requiring a CN ratio higher than that of the strong layer, an OFDM demodulation means 15 for demodulating the digital signal of the strong layer from the received broadcasting signal, a CN ratio acquisition means 32 for acquiring a characteristic value concerning the quality of a demodulated digital signal of the strong layer, and a means 34 for judging superiority or inferiority in the quality of digital signal of the strong layer by comparing an acquired characteristic value with a reference value indicative of a fixed quality wherein the OFDM demodulation means 15 further demodulates the digital signal of the weak layer from a received broadcasting signal when the judgment means 34 judges that the digital signal of the strong layer has a quality beyond the reference value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a receiving apparatus corresponding to hierarchically transmitted digital broadcasting such as terrestrial digital television broadcasting, a channel preset method for digital broadcasting, and a channel preset program for digital broadcasting.

In recent years, terrestrial digital television broadcasting has been started, and various televisions and information terminals corresponding to this broadcasting have been released. In such terrestrial digital television broadcasting, one channel is divided into a plurality of segments (regions), and consists of a strong hierarchy composed of one segment and a plurality of segments, and a required CN ratio (Carrier Noise) than the strong hierarchy. (ratio) is divided into at least two with a weak hierarchy and a TV program is supplied for each hierarchy. Here, the required CN ratio indicates a CN ratio that achieves 2 × 10 ⁻⁴ after the convolutional code, which is one of the encoding methods, is decoded.

  In these two hierarchies, the image quality of the displayed image does not deteriorate until the CN ratio falls below the specified value, so that the image is displayed well even when moving. Mobile digital broadcasting receivers suitable for reception and excellent in portability are becoming popular. However, since such a mobile type digital broadcast receiving apparatus needs to preset a receivable channel each time when moving, like the digital broadcast receiving apparatus described in Patent Document 1 below, In addition to searching for channels that can be received from TV radio waves, the reception status is detected and stored, and the receivable channels and the reception status of the channels are displayed on the display screen of the monitor.

JP 2003-274310 A

  In the proposal disclosed in the above-mentioned publication, it takes a lot of time to scan all channels for each layer in order to search for a receivable channel without distinguishing between a strong layer and a weak layer.

  In order to solve the above-described problem, the receiving apparatus of the present invention receives a broadcast signal of a digital broadcast that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy. Demodulating means for demodulating the strong layer digital signal from the received broadcast signal, acquiring means for acquiring a characteristic value relating to the quality of the demodulated strong layer digital signal, and the acquired characteristic value Determining means for determining the superiority or inferiority of the quality of the strong layer digital signal by comparing with a reference value indicating a certain quality, and the demodulating means in which the strong layer digital signal is The digital signal of the weak layer is further demodulated from the received broadcast signal in response to being determined to have a quality equal to or higher than a reference value.

  According to the present invention, after receiving a broadcast signal of a digital broadcast broadcast using a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy, the digital signal of the strong hierarchy of the received broadcast signal is received. Demodulate, acquire characteristic values related to the quality of the demodulated strong layer digital signal, determine the superiority or inferiority of the quality of the strong layer digital signal from the comparison between this characteristic value and a reference value indicating a certain quality. When it is determined that the digital signal in the hierarchy is higher than the reference value, the digital signal in the weak hierarchy of the received broadcast signal is demodulated. Therefore, the strong layer and the weak layer included in the received broadcast signal are not demodulated all but only if the characteristic value related to the quality of the demodulated strong layer digital signal is higher than the reference value. Since a weak layer having a higher required CN ratio is demodulated, the demodulation process becomes more efficient, and the time required to search for a receivable channel can be shortened.

  The receiving apparatus of the present invention preferably further comprises storage means for storing at least one of the strong layer digital signal and the weak layer digital signal as a selectable channel.

  According to the present invention, the strong layer digital signal and the weak layer digital signal demodulated by the demodulation unit are stored in the storage unit as selectable channels. Can be read.

  The receiving apparatus of the present invention preferably further includes display means for selectively displaying the stored channels.

  According to the present invention, since the channels stored in the storage means are displayed so as to be selectable, a desired channel can be easily selected.

  In the receiving apparatus of the present invention, the display means may display information of the selectable strong layer digital signal and the weak layer digital signal, respectively, with distinguishable icons.

  In the receiving device of the present invention, the display means demodulates the icon corresponding to the strong layer digital signal demodulated from each broadcast signal and the icon corresponding to the weak layer digital signal. It is preferable that the broadcast signal and the two layers are displayed side by side in the vertical direction or the horizontal direction.

  According to the present invention, the icon indicating the information of the strong hierarchy digital signal and the icon indicating the information of the weak hierarchy digital signal are displayed side by side in the vertical direction or the horizontal direction for each demodulated broadcast signal and every two levels. Therefore, the reception state of one broadcast signal can be more visually displayed in one direction of the icon.

  In the receiving device of the present invention, the quality-related characteristic value may be an error rate indicating a rate at which erroneous data appears in data of the digital signal demodulated from the broadcast signal, and the digital signal A CN ratio value indicating a ratio of noise included in the broadcast signal demodulating the signal may be indicated.

  In order to solve the above-described problems, a digital broadcast channel preset method according to the present invention provides a digital broadcast signal that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy. Receiving, demodulating the strong layer digital signal from the received broadcast signal, obtaining a characteristic value related to the quality of the demodulated strong layer digital signal, and the acquired characteristic value And a standard value indicating a certain quality to determine superiority or inferiority of the quality of the strong layer digital signal, and the strong layer digital signal is determined to have a quality equal to or higher than the reference value. And a step of demodulating the digital signal of the weak hierarchy from the received broadcast signal, and storing a selectable channel.

  According to the present invention, after receiving a broadcast signal of a digital broadcast broadcast using a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy, the digital signal of the strong hierarchy of the received broadcast signal is received. Demodulate, acquire characteristic values related to the quality of the demodulated strong layer digital signal, determine the superiority or inferiority of the quality of the strong layer digital signal from the comparison between this characteristic value and a reference value indicating a certain quality. When it is determined that the digital signal in the hierarchy is higher than the reference value, the digital signal in the weak hierarchy of the received broadcast signal is demodulated. Therefore, the strong layer and the weak layer included in the received broadcast signal are not demodulated all but only if the characteristic value related to the quality of the demodulated strong layer digital signal is higher than the reference value. Since a weak layer having a higher required CN ratio is demodulated, the demodulation process becomes more efficient, and the time required to search for a receivable channel can be shortened.

  In order to solve the above-described problems, a digital broadcast channel preset program according to the present invention generates a broadcast signal of a digital broadcast that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy. A procedure for receiving, a procedure for demodulating the strong layer digital signal from the received broadcast signal, a procedure for obtaining a characteristic value relating to the quality of the demodulated strong layer digital signal, and the acquired characteristic value. And a standard value indicating a certain quality to determine the superiority or inferiority of the quality of the strong layer digital signal, and the strong layer digital signal is determined to have a quality equal to or higher than the reference value. And storing a selectable channel by causing a computer to execute a procedure for demodulating the weak-layer digital signal from the received broadcast signal. I am characterized in.

  According to the present invention, after receiving a broadcast signal of a digital broadcast broadcast using a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy, the digital signal of the strong hierarchy of the received broadcast signal is received. Demodulate, acquire characteristic values related to the quality of the demodulated strong layer digital signal, determine the superiority or inferiority of the quality of the strong layer digital signal from the comparison between this characteristic value and a reference value indicating a certain quality. When it is determined that the digital signal in the hierarchy is higher than the reference value, the digital signal in the weak hierarchy of the received broadcast signal is demodulated. Therefore, the strong layer and the weak layer included in the received broadcast signal are not demodulated all but only if the characteristic value related to the quality of the demodulated strong layer digital signal is higher than the reference value. Since a weak layer having a higher required CN ratio is demodulated, the demodulation process becomes more efficient, and the time required to search for a receivable channel can be shortened.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)

  FIG. 1 is a block diagram showing a functional configuration of a television receiver 1 to which a receiver for receiving a digital broadcast according to the present invention is applied. The television receiver 1 is assumed to be a television receiver that can receive a digital terrestrial television broadcast in which a program is distributed for each of the strong hierarchy and the weak hierarchy, and is portable across a plurality of broadcast areas. To do.

  This television receiver 1 includes a receiving means 10, an OFDM (Orthogonal Frequency Division Multiplexing) demodulating means 15, an error correcting means 20, an MPEG (Moving Picture Experts Group) demodulating means 25, a control means 30, and an operating means. 40, a storage unit 45, a display unit 50, an audio output unit 55, and a receiving antenna (antenna) 60. The control unit 30 includes a CN ratio acquisition unit 32 and a determination unit 34.

  The receiving means 10 has a tuner function for receiving a broadcast signal input via the receiving antenna 60 for each channel. This broadcast signal is a broadcast signal of a digital television broadcast distributed using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy. More specifically, in the case of terrestrial digital television broadcasting in Japan, a plurality of UHF (Ultra High Frequency) bands are used, and the 6 MHz bandwidth constituting one channel is divided into 14 parts. 13 are used as segments. These segments are separated into two layers, a strong layer composed of one segment and a weak layer composed of 12 segments, and are transmitted in a hierarchical manner. That is, a low-resolution television broadcast is distributed using a strong hierarchy composed of one segment, and a high-resolution television broadcast such as a high-definition television is distributed using a weak hierarchy composed of 12 segments. The receiving means 10 operates in accordance with an instruction from the control means 30 and the broadcast signal received by the receiving means 10 is sent to the OFDM demodulating means 15. The receiving means 10 can receive a broadcast signal of a channel designated by the operation means 40 from each channel of a preset frequency band, and each of the preset start channel to preset end channel. It is also possible to automatically switch the channel sequentially and receive.

  The OFDM demodulator 15 demodulates the broadcast signal sent from the receiver 10 into a digital signal composed of “0” and “1”. Further, the OFDM demodulating unit 15 can selectively demodulate at least one of the strong layer and the weak layer according to an instruction from the control unit 30. The digital signal demodulated by the OFDM demodulating means 15 is sent to the error correcting means 20. Further, the OFDM demodulating unit 15 calculates the CN ratio of the broadcast signal of the higher hierarchy in response to the instruction from the CN ratio acquiring unit 32.

  In response to an instruction from the control unit 30, the error correction unit 20 performs error correction processing on the digital signal transmitted from the OFDM demodulation unit 15 by a known procedure. Specifically, when a TS packet transmitted from a broadcasting station is transmitted after being subjected to Reed-Solomon encoding and convolutional encoding, the error correction means 20 performs Viterbi decoding and Reed-Solomon decoding to restore the TS packet. To do. The digital signal that has been subjected to error correction processing in this way is sent to the MPEG demodulation means 25.

  The MPEG demodulation means 25 demodulates the digital signal such as a TS packet sent from the error correction means 20 by separating it into a video signal and an audio signal. The demodulated video signal is sent to and displayed on a display means 50 having a display medium such as a liquid crystal panel, and the demodulated audio signal is sent to an audio output means 55 having a speaker or the like and outputted as audio. .

  The CN ratio acquisition unit 32 acquires a characteristic value relating to the quality of the digital signal of the strong layer demodulated by the OFDM demodulation unit 15. Here, in the first embodiment, the characteristic value related to the quality of the digital signal employs a CN ratio indicating a ratio of the magnitude of the carrier power and noise power included in the broadcast signal. Specifically, the CN ratio obtaining unit 32 instructs the OFDM demodulating unit 15 that demodulates the strong layer from the broadcast signal to calculate the CN ratio of the strong layer, and the calculated CN ratio from the OFDM demodulating unit 15. get. The CN ratio acquired here is sent to the determination means 34.

  The determination unit 34 determines the superiority or inferiority of the quality of the digital signal of the strong hierarchy by comparing the CN ratio value of the strong hierarchy sent from the CN ratio acquisition unit 32 with a preset CN ratio reference value. Specifically, when the CN ratio value of the strong layer is a value equal to or higher than the CN ratio reference value, the control unit 30 determines that the digital signal of the strong layer has a quality higher than a predetermined reference, and the OFDM demodulating unit 15 is instructed to demodulate the weak layer. Here, the CN ratio reference value is set by adding a margin value of, for example, 12.6 dB or more to the CN ratio value necessary for receiving a broadcast distributed in a strong hierarchy. Specifically, when a high-layer broadcast using one segment is subjected to quadrature phase modulation (QPSK), assuming that the coding rate is 75%, the CN ratio value required for receiving the broadcast is 7. 5 dB. On the other hand, it is known that weak binary broadcasting using 12 segments such as HDTV is subjected to 64-value quadrature amplitude modulation (64QAM). In such a case, assuming that the coding rate is 75%, The CN ratio value necessary for receiving the signal is 20.1 dB. Therefore, in order to receive a broadcast of a weak layer using 12 segments, it is a condition that a CN ratio value of 12.6 dB or more is obtained from the CN ratio value of a strong layer using 1 segment. Thus, the CN ratio reference value is set.

  The operation unit 40 is operated by a user to select a channel, set voice, etc., and the instruction content operated here is sent to the control unit 30, and the control unit 30 is configured to control each functional unit. ing.

  The storage means 45 stores at least one of the demodulated strong layer digital signal and weak layer digital signal as channel selectable channel information. The channel information stored in the storage unit 45 is referred to by the control unit 30 as preset information of receivable channels, and is selected as a display medium for displaying a video signal or another display medium different from the display medium. Displayed as possible. For example, FIG. 2 shows a channel information image 52 displayed on the display means 50. As shown in the channel information image 52, the information on the selectable strong layer digital signal and the weak layer digital signal is displayed with distinguishable icons, and each icon indicates a demodulated broadcast signal. And for each layer, they are displayed side by side in the vertical or horizontal direction. In the first embodiment, the strong hierarchy broadcast channel group 56 using one segment is displayed side by side in the lower part of the channel information image 52, and the weak hierarchy broadcast channel group 54 using 12 segments is The channel information image 52 is displayed side by side in the horizontal direction in association with the broadcast channel of the strong hierarchy. Further, the strong broadcast channel group 56 and the weak broadcast channel group 54 may be displayed in different colors.

  Although not shown, the television receiver 1 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory), a RAM (Random Access Memory), a memory such as a flash memory, an LSI ( An integrated circuit such as Large Scale Integration) is provided as hardware. These hardware are connected so that each signal can be transmitted and received via a bus, and can process information like a computer based on a program stored in a memory. The function of each functional unit described above is as follows. These hardware and software are realized by organic cooperation.

  FIG. 3 is a flowchart for explaining the flow of processing for presetting channels that can be received by the television receiver 1.

  When this process is started, first, the receiving means 10 sets a reception target channel to a predetermined preset start channel (step S100). Subsequently, the receiving means 10 starts receiving a broadcast signal on the set channel (step S102).

  Next, it is determined whether or not a broadcast signal can be received on the set channel (step S104). If a broadcast signal can be received on the set channel (Yes in step S104), a process of storing receivable channels (step S104). After step S106) is executed, the process proceeds to the next step (step S108). Details of the process of storing receivable channels (step S106) will be described later. On the other hand, when the broadcast signal cannot be received on the set channel (No in step S104), it is determined whether or not the set channel has reached the preset end channel (step S108).

  If the set channel does not reach the preset end channel (No in step S108), the receiving unit 10 sets the channel to be received as the next channel (step S110), and the receiving unit 10 sets the channel. The process returns to the step of receiving a broadcast signal on the channel (step S102).

  On the other hand, when the set channel reaches the preset end channel (Yes in step S108), the stored information about the receivable channel is displayed on the display means 50 so as to be selectable (step S112), and a series of processing is performed. finish.

  Next, details of the step of storing receivable channels (step S106) will be described with reference to FIG.

  When this step (step S106) is executed, first, the OFDM demodulator 15 demodulates a strong layer digital signal from the broadcast signal (step S120). Subsequently, it is determined whether or not the strong layer digital signal has been demodulated normally (step S122). Here, if the strong layer digital signal is not demodulated normally for some reason (No in step S122), the series of processes is terminated, and the process returns to the step of FIG. 3 (step S108).

  On the other hand, when the strong layer digital signal is normally demodulated (Yes in step S122), the channel information set in the receiving unit 10 is stored in the storage unit 45 as a receivable strong layer channel. (Step S124).

  Next, the CN ratio acquisition unit 32 acquires the CN ratio of the strong layer digital signal demodulated by the OFDM demodulation unit 15 (step S126).

  Subsequently, the determination unit 34 compares the acquired CN ratio value of the strong hierarchy with a preset CN ratio reference value (step S128), and determines whether the CN ratio value is greater than or equal to the CN ratio reference value. Determination is made (step S130). Here, when the CN ratio value does not exceed the CN ratio reference value necessary for weak layer reception (No in step S130), it is determined that the viewable quality cannot be obtained even if the weak layer digital signal is demodulated. Then, the series of processes is terminated, and the process returns to the step of FIG. 3 (Step S108).

  On the other hand, if the CN ratio value is equal to or greater than the CN ratio reference value (Yes in step S130), the channel information set in the receiving means 10 is stored in the storage means 45 as a weak hierarchical channel that can be received ( Step S136), the process returns to the step of FIG. 3 (Step S108).

According to this embodiment described above, the following effects are obtained.
(1) Channel search that can be received by digital broadcasting is performed by separating a strong layer digital signal and a weak layer digital signal, and first demodulating the strong layer digital signal, the quality of the digital signal is sufficient. In such a case, it is determined that a channel in a weak layer having a required CN ratio higher than that in a strong layer can be received, and the channel can be preset at a high speed. As a result, channel selection can be performed quickly and comfortably even when moving across a wide range of broadcasting areas.
(Embodiment 2)

  Next, Embodiment 2 of the present invention will be described with reference to FIG. In the following description, the same parts as those already described are denoted by the same reference numerals and description thereof is omitted.

FIG. 5 is a block diagram illustrating a functional configuration of the television receiver 1 according to the second embodiment.
In the television receiver 1 according to the first embodiment, the OFDM demodulator 15 is instructed to demodulate the weak layer based on the CN ratio value acquired by the CN ratio acquirer 32. Based on the error rate acquired by the rate acquiring unit 36, the OFDM demodulating unit 15 is instructed to demodulate the weak layer. Specifically, the control unit 30 includes an error rate acquisition unit 36, and the error correction unit 20 calculates an error rate of data in a strong hierarchical digital signal in response to an instruction from the control unit 30. It is configured. The error rate acquisition unit 36 acquires an error rate in this process when the error correction unit 20 performs an error correction process on the digital signal of the higher layer, and the acquired error rate information is sent to the determination unit 34. Sent. The judging means 34 judges the superiority or inferiority of the quality of the digital signal of the strong layer from the magnitude relationship between this error rate and a preset error rate reference value, and the error rate of the strong layer is below the error rate reference value. In this case, the control unit 30 determines that the digital signal of the strong layer has a quality higher than a predetermined standard, and instructs the OFDM demodulation unit 15 to perform the demodulation of the weak layer.

  According to this embodiment, the same effect as described in the first embodiment can be obtained.

As mentioned above, although this invention was demonstrated based on embodiment shown in figure, this invention is not limited to this embodiment, The modification as described below can also be assumed.
(1) Each embodiment described above is assumed to be applied to a portable television receiver 1 that receives terrestrial digital television broadcasts. However, the receiver of the present invention is not limited to this, and digital The present invention can also be applied to a receiving apparatus that receives radio broadcasts, digital data broadcasts, and the like. Furthermore, the receiving device of the present invention may be integrated in a semiconductor circuit or the like and applied to various information devices. The standard of terrestrial digital television broadcasting to which the present invention can be applied is not limited to the ISDB-T (Integrated Services Digital Broadcasting Terrestrial) system adopted in Japan, for example, DVB-T (Digital Video). It can also be applied to other standards such as the Broadcasting Terrestrial) method.
(2) In each of the above embodiments, segment separation is not limited to two layers, a strong layer and a weak layer, and can also be applied to a case where the segment is separated into three layers including an intermediate layer. Whether the intermediate layer can be demodulated may be determined based on the quality of the digital signal.

1 is a block diagram showing a functional configuration of a digital broadcast receiving apparatus according to Embodiment 1 of the present invention. The channel information image which shows the channel information displayed on the display means. The flowchart explaining the flow of the process which presets the channel which can be received. The flowchart explaining the flow of the process which memorize | stores the channel which can be received. The block diagram which shows the function structure of the digital broadcast receiver which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Television receiver, 10 ... Reception means, 15 ... OFDM demodulation means, 20 ... Error correction means, 25 ... MPEG demodulation means, 30 ... Control means, 32 ... CN ratio acquisition means, 34 ... Determination means, 36 ... Error Rate acquisition means, 40 ... operation means, 45 ... storage means, 50 ... display means, 52 ... channel information image, 54 ... weak broadcast channel group, 55 ... audio output means, 56 ... strong broadcast channel group, 60 ... Receiving antenna.

Claims (9)

Receiving means for receiving a broadcast signal of a digital broadcast that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy;
Demodulation means for demodulating the strong layer digital signal from the received broadcast signal;
Obtaining means for obtaining characteristic values relating to the quality of the demodulated strong layer digital signal;
A determination means for determining the superiority or inferiority of the digital signal of the strong hierarchy by comparing the acquired characteristic value with a reference value indicating a certain quality,
The demodulating means includes
In response to determining that the strong layer digital signal has a quality equal to or higher than the reference value by the determining unit, the weak layer digital signal is further demodulated from the received broadcast signal. Receiver device. The receiving device according to claim 1,
The receiving apparatus further comprising a storage unit that stores at least one of the strong layer digital signal and the weak layer digital signal as a selectable channel. The receiving device according to claim 2,
The receiving apparatus further comprising display means for selectively displaying the stored channels. The receiving apparatus according to claim 3,
The display device displays the information of the digital signal of the strong layer and the digital signal of the weak layer that can be selected by icons that can be distinguished from each other. The receiving device according to claim 4,
The display means displays an icon corresponding to the strong layer digital signal demodulated from each broadcast signal and an icon corresponding to the weak layer digital signal for each of the demodulated broadcast signal and the two layers. A receiving apparatus characterized by being displayed side by side in the vertical direction or the horizontal direction. The receiving apparatus according to any one of claims 1 to 5,
The receiving apparatus according to claim 1, wherein the characteristic value relating to the quality is an error rate indicating a rate at which erroneous data appears in the data of the digital signal demodulated from the broadcast signal. The receiving apparatus according to any one of claims 1 to 5,
The receiving apparatus according to claim 1, wherein the quality-related characteristic value indicates a CN ratio value indicating a ratio of noise included in the broadcast signal demodulating the digital signal. Receiving a broadcast signal of a digital broadcast that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy;
Demodulating the strong layer digital signal from the received broadcast signal;
Obtaining a characteristic value relating to the quality of the demodulated strong layer digital signal;
Determining the superiority or inferiority of the digital signal of the strong hierarchy by comparing the acquired characteristic value with a reference value indicating a certain quality;
Demodulating the weak layer digital signal from the received broadcast signal, if the strong layer digital signal is determined to have a quality equal to or higher than the reference value;
A channel presetting method for digital broadcasting, characterized in that a channel that can be selected is stored. A procedure for receiving a broadcast signal of a digital broadcast that is broadcast using at least a strong hierarchy and a weak hierarchy having a higher required CN ratio than the strong hierarchy;
Demodulating the strong layer digital signal from the received broadcast signal;
Obtaining a characteristic value relating to the quality of the demodulated strong layer digital signal;
A procedure for determining the superiority or inferiority of the digital signal of the strong hierarchy by comparing the acquired characteristic value with a reference value indicating a certain quality;
A step of demodulating the weak layer digital signal from the received broadcast signal, if the strong layer digital signal is determined to have a quality equal to or higher than the reference value;
A channel preset program for digital broadcasting, characterized in that a selectable channel is stored by causing a computer to execute the program.

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