JP2004336190A - Receiving apparatus and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make avoidable a broadcast reception interruption even when a receiving state is deteriorated, by selecting and outputting a proper program from among a plurality of received programs in response to the reception state of broadcasting. <P>SOLUTION: When a demodulation section 13 receives a broadcasting signal including a plurality of programs with different qualities, a Viterbi decoding section 32 and an RS decoding section 37 correct an error of the received broadcasting signal. In this case, a comparison discrimination section 38 compares an output of the Viterbi decoding section 32 with an output of the RS decoding section 37 to discriminate the reception state. A control section 14 receives the reception state from the comparison discrimination section 38, decides which quality of the program is to be used for an output object among a plurality of the programs on the basis of the reception state and instructs a switching section 15 to output the decided program. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiving apparatus and a receiving method for receiving a broadcast including a plurality of programs, and more particularly to a receiving apparatus and a receiving method for selecting a predetermined program from among the plurality of programs as an output target according to a receiving state of the broadcast. .
[0002]
[Prior art]
With conventional receivers that receive terrestrial analog broadcasts, when receiving a multi-audio broadcast such as stereo or audio multiplex, if the reception condition of the radio wave is not good, the reception mode is automatically switched to receive more. By receiving monaural audio with high sensitivity, the stability of quality when receiving television broadcasts is apparently secured.
[0003]
As for television broadcasting, video compression using the MPEG (Moving Picture Experts Group) system and digitization using digital modulation / demodulation techniques have been progressing, and CS (Communication Satellite) digital broadcasting using satellites and BS (Broadcasting). (Satellite) Digital broadcasting has already begun. In addition, terrestrial digital broadcasting using terrestrial waves is scheduled to start in 2003.
[0004]
In the analog broadcasting, when the received broadcast is reproduced, the quality of the output video and audio gradually deteriorates as the receiving condition deteriorates. However, in digital broadcasting, it is known that the quality rapidly deteriorates at a certain reception level, which is what is called a cliff effect.
[0005]
Therefore, in order to deal with such a problem, for terrestrial digital broadcasting, a plurality of compressed bit streams multiplexed by the hierarchical transmission method are received, and which bit stream is reproduced according to their reception levels. The following Patent Document 1 discloses a signal coded receiving device in which the user designates the above.
[0006]
When the reception level is not good, the idea is to maintain the continuity of the broadcast by gradually lowering the quality of the broadcast to be provided, thereby avoiding the worst case in which the broadcast is suddenly interrupted. Such an approach is called “graceful degradation” and is widely known in the field of digital broadcast reception.
[0007]
[Patent Document 1]
JP 2001-223665 A
[0008]
[Problems to be solved by the invention]
However, the signal encoding receiver and the like of Patent Document 1 have a problem that the user has to give an instruction to switch the program, which places a heavy burden on the user.
[0009]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a receiving apparatus and a receiving method for automatically switching an output target program according to a broadcast receiving condition.
[0010]
[Means for Solving the Problems]
The present invention is a receiving apparatus that receives a broadcast signal of a broadcast to which a plurality of programs having different qualities are transmitted, and outputs a predetermined program among the plurality of programs, and a reception state determination that determines a reception state of the broadcast signal Means, and switching means for automatically switching the output program based on the determined reception status.
[0011]
The present invention is a receiving method for receiving a broadcast signal of a broadcast in which a plurality of programs having different qualities are transmitted, and outputting a predetermined program among the plurality of programs, and determining a reception state of the broadcast signal; Automatically switching the program to be output based on the determined reception status.
[0012]
According to the present invention, the program to be output is automatically switched to a program of another quality according to the broadcast reception status determined by the reception status determination means.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a receiving apparatus and a receiving method of the present invention will be described by taking a receiving apparatus and a receiving method for receiving terrestrial digital broadcasting as an example. In addition, a service in a broadcasting form called ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) is provided, which is one of the objectives of realizing high-presence broadcasting that provides a resolution and information amount higher than HDTV (High Definition Television). The description will be made on the assumption that this is the case.
[0014]
Further, the embodiments are configured in accordance with the terrestrial digital broadcast transmission system studied in Japan. More specifically, OFDM (Orthogonal Frequency Division Multiplexing) for modulating a multicarrier (multi-carrier) is adopted as a modulation scheme, and each program in one channel includes a QPSK (Quadrature Phase Shifting, Quadrature Phase Shifting). DQPSK (Differential Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), 64QAM (64 Quadrature Amplitude Modulation), and the like.
[0015]
Further, OFDM has the greatest feature in that it is strong against a transmission path having a delay wave, and is an effective transmission system of high-quality digital audio broadcasting (DAB) for mobiles.
[0016]
The error correction method uses Viterbi decoding as an inner code, and uses a Reed-Solomon code which is a block code as an outer code.
[0017]
Also, in order to hierarchize a plurality of programs on one channel, a method called BST (Band Segmented Transmission) is used. In BST, a 6-MHz band (effective area is 5.6 MHz), which is one channel band, is divided into 13 segments, these are classified into two or three groups, and transmitted as layers in a robust group order.
[0018]
Here, if one layer is transmitted in 9 or 10 segments or more, a broadcast of high quality (HD quality) equivalent to HDTV can be transmitted substantially. In addition, if there is one layer including three or more segments, it is considered that a broadcast of standard quality (SD quality) equivalent to SDTV (Standard Definition Television), which is comparable to the image quality of conventional analog NTSC broadcast, can be transmitted. The SD quality is relatively lower than the HD quality.
[0019]
HDTV is a high-definition, wide-screen system with 1125 scanning lines and an aspect ratio of 16: 9 according to the Japanese standard. The transmission bit rate of the original signal is 1.188 Gbit / s in the case of 8-bit quantization. It is. On the other hand, in the case of NTSC, which is a type of SDTV, the number of scanning lines is 525, the aspect ratio is 4: 3, and the transmission bit rate of the original signal is 216 Mbit / s in the case of 8-bit quantization.
[0020]
Furthermore, by using a more efficient image / data compression system such as MPEG4, it is considered that even in a hierarchy composed of one or two segments, SD quality broadcast can be distributed on a screen of a medium size or smaller.
[0021]
An embodiment of the present invention is a receiving apparatus that is intended to receive and output HD-quality broadcasts for broadcast channels of a multi-layer system, and to respond to electric field strength and a multipath environment. As in analog FM audio reception, an HD quality program in the weakest hierarchy and an SD quality program in the strong hierarchy are automatically selected in accordance with the broadcast reception status.
[0022]
In particular, if the channel data transmission side provides programs of the same content even if there is a difference in the quality of HD quality or SD quality in each layer, a broadcast transmission / reception system that can provide a kind of countermeasures against poor viewing is configured. Can.
[0023]
FIG. 1 is a schematic diagram illustrating an example of hierarchization of one channel. In FIG. 1A, the band of one channel (5.6 MHz) is divided into 13 segments, and one segment S7 is used for transmitting one program. As described above, the program is modulated by a modulation method such as QPSK or DQPSK, and is further modulated by OFDM. As described above, when one segment is used for transmission of one program, normally, an SD quality program can be provided on a screen of a medium size or smaller. Also, the one-segment band here is suitable for use in one mobile communication and one mobile phone.
[0024]
FIG. 1B shows three segments S6, S7, and S8, which are used for transmitting one program, in the thirteen segments divided similarly to FIG. 1A. This program is modulated in the same manner as in FIG. 1A, and can normally provide an SD quality program on a standard size screen.
[0025]
FIG. 1C shows that in the 13 segments divided as in FIG. 1A, three segments S5, S6 and S8 are used for the transmission of the first program, and one segment S7 is used for the transmission of the second program. It is used. These two programs can be modulated by different modulation schemes, and the whole can be modulated and multiplexed by OFDM. On the receiving device side, the first program can be broadcast in SD quality on a screen of a normal size, and the second program can be broadcast in SD quality on a screen of a medium size or smaller.
[0026]
Next, the configuration and operation of the receiving apparatus 10 according to the embodiment of the present invention will be described with reference to FIGS. 2 and 3, the whole of the receiving system 10 is illustrated. Accordingly, the data transmitted from the bit deinterleave 29a of FIG. 2 is received at the depunctured 30a of FIG. 3, and likewise from the bit deinterleave 29b and the bit deinterleave 29c of FIG. Data is transmitted to each of 30b and depunctured 30c.
[0027]
In the present invention, the reception status determination means has a function of determining the reception status of the broadcast signal, and the comparison determination unit 39 corresponds to this in the present embodiment, as described later. Further, the switching means has a function of selecting a program suitable for the situation based on the determined reception situation and automatically switching the program. The unit 15 corresponds to this.
[0028]
The receiving apparatus 10 includes an antenna 11, a tuner 20 connected to the antenna 11, a demodulation unit 13 that receives an IF signal from the tuner 20, a control unit (CPU) 14 that receives a predetermined signal from the demodulation unit 13, and control by a control unit 14. It includes a switching unit 15 that receives a signal and a TS (transport stream) from the demodulation unit 13, an AV signal processing unit 16 that receives a TS from the switching unit 15 and performs AV processing, and a display unit 17.
[0029]
The demodulation unit 13 further includes an FFT unit 21, a synchronous reproduction unit 22, a frame extraction unit 23, a carrier demodulation unit 24, a frequency deinterleave unit 25, a time deinterleave unit 26, a demapping unit 27, and a first hierarchical division unit 28 , Bit deinterleaving units 29a to 29c, depuncturing units 30a to 30c, layer combining unit 31, Viterbi decoding unit 32, second layer dividing unit 33, byte deinterleaving units 34a to 34c, and energy despreading units 35a to 35c. , A TS playback unit 36, an RS decoding unit 37, and a comparison determination unit 38.
[0030]
A display unit 17 such as a liquid crystal screen or a CRT monitor is connected to the AV signal processing unit 16, and an HD quality program or an SD quality program is displayed on the display unit 17 from the AV signal processing unit 16. Similarly, an audio output device such as a speaker is also connected to the AV signal processing unit 16, but the display is omitted here. From the AV signal processing unit 16, sounds of various sound quality levels are output to the sound output device.
[0031]
A tuner 20 for UHF (Ultra High Frequency) and VHF (Very High Frequency) receives an ISDB-T OFDM signal as an RF (Radio Frequency) signal via an antenna 11 and performs amplification, frequency conversion, filtering, and the like. After that, the signal is output to the demodulation unit 13 as an IF (Intermediate Frequency) signal.
[0032]
The FFT unit 21 receives the IF signal and performs an FFT (Fast Fourier Transform) operation. At this time, the frame is synchronized with respect to the input signal by the synchronous reproduction unit 22 and the frame extraction unit 23.
[0033]
Next, the carrier demodulation unit 24 digitally demodulates the signal output from the FFT unit 21 by a predetermined method.
[0034]
After that, the frequency deinterleave unit 25 and the time deinterleave unit 26 perform a deinterleave process on these signals. Interleaving is a technique for randomizing an error sequence when a transmission error occurs in a burst. In OFDM, frequency interleaving in which interleaving is performed in the direction of the frequency axis and time interleaving in which interleaving is performed in the direction of the time axis are possible. These interleaving processes are performed on the transmission side, and the processing for canceling this is performed on the reception side, And deinterleave processing. In the demodulation unit 13, a frequency deinterleave unit 25 and a time deinterleave unit 26 correspond to this. This makes it possible to disperse burst errors in the transmission path.
[0035]
Thereafter, the encoded data is sent from the time deinterleaving section 26 to the demapping section 27. Here, the mapping process performed on the transmission side is canceled. In the mapping process, as in the case of interleaving, the cause of error occurrence in the transmission path such as noise or fading is dispersed. The mapping process to each symbol is performed according to a modulation method such as QPSK or 16QAM.
[0036]
Next, the data is sent to the first hierarchy division unit 28, where it is divided into each hierarchy. When a program using one segment and a program using three segments as illustrated in FIG. 1C are transmitted, data corresponding to each of these layers is individually extracted.
[0037]
Each of the divided data is transmitted to the corresponding bit deinterleave units 29a to 29c, where bit deinterleave processing is performed. The transmitting side can set bit interleaving on a bit-by-bit basis in order to avoid a burst-like error during the mapping processing to the symbols. If the interleaving has been performed, the bit deinterleaving process is performed to cancel the interleaving.
[0038]
Next, each of the divided data is subjected to a depuncturing process in each of the depuncturing units 30a to 30c. On the transmission side, coded data (punctured code) having a higher coding rate can be created by deleting some symbols from the original convolutionally coded data. Therefore, if the processing is performed on the transmission side, the depuncturing processing is performed.
[0039]
The layer combining unit 31 receives data from the depuncturing units 30a to 30c and performs layer combining. The hierarchically synthesized data is sent to the Viterbi decoding unit 32. The Viterbi decoding unit 32 then performs inner code decoding by error correction using convolutional coding performed on the transmission side. For such inner coding, Viterbi decoding and convolutional code are generally used in combination. The data on which the error correction has been performed by the Viterbi decoding is transmitted to the second hierarchical division unit 33, where the data is again hierarchically divided.
[0040]
Next, the data divided into the respective layers is deinterleaved by the byte deinterleaving units 34a to 34c, respectively. Byte interleaving, like bit interleaving, is a process performed to enhance error resilience, and can be set in byte units between an inner code and an outer code. Each of the byte deinterleaving units 34a to 34c performs deinterleaving when the input data is error-correction-coded by Reed-Solomon code.
[0041]
When the data output from the byte deinterleaving units 34a to 34c is subjected to the energy spreading process on the transmission side, the energy despreading units 35a to 35c perform the processes opposite to the processes. The energy spreading process is a process performed during transmission to prevent energy from being concentrated on a specific frequency.
[0042]
The data is transmitted from the energy despreading units 35a to 35c to the TS reproducing unit 36. Here, the TS reproducing unit 36 accumulates the data received for each layer, rearranges the data in units of TSs (transport streams), and sends the TSs to the RS decoding unit 37 in the order multiplexed on the transmission side. I do.
[0043]
The RS decoder 37 receives the TS transmitted from the TS reproducer 36 and performs RS decoding. For example, the RS (204, 188) is subjected to RS decoding in units of an RS block consisting of 204 bytes (symbols) to correct error bytes existing in the RS block and output a transport stream packet (TSP). More specifically, a Reed-Solomon encoding process in which a 16-byte parity is added to a 188-byte TSP is performed. The error correction capability of the RS (204, 188) is 8 bytes. If an error of 9 bytes or more exists in one RS block (204 bytes), the block cannot be corrected.
[0044]
The RS decoding section 37 can output an error flag for the corrected byte when correction has been performed, and can output an uncorrectable flag when the block cannot be corrected.
[0045]
When the RS decoding ends, the TS is output from the RS decoding unit 37 to the switching unit 15. In the case where a plurality of programs are hierarchized in one channel as shown in FIG. 1C, the TS of each program is provided to the switching unit 15 in a mixed form.
[0046]
On the other hand, the output of the RS decoding unit 37 and the output of the Viterbi decoding unit 32 are both transmitted to the comparison determination unit 38, where both data are compared. By this comparison processing, the data before and after the RS decoding is compared, and it is determined how many bytes of the whole bytes (symbols) have been corrected. This means, in other words, how many bytes of the total bytes have been erroneously received, which is essentially information such as BER (Bit Error Rate) or MER (Modulation Error Ratio). Is obtained. Further, although the comparison / decision unit 38 is indicated by the symbol of one comparator in FIG. 3, this is merely a notation for facilitating understanding, and in fact, in addition to the comparison processing, the RS decoding unit 37 The calculation for obtaining the value of BER or the like is also performed using the output or the like.
[0047]
Therefore, the information such as the BER and the MER can be considered to indicate the reception status of the signal received via the tuner 20. This information also has the same meaning as the received C / N (Carrier to Noise Ratio). Further, as described above, since the RS decoding unit 37 can output the error flag and the uncorrectable flag, it is also possible to grasp the reception status to some extent using these.
[0048]
Further, in the present embodiment, in order to measure BER and the like, data after Viterbi decoding is used as a comparison target (so-called Post-Viterbi). , Which are generally employed in relatively erroneous reception. However, the receiving device of the present invention is not limited to acquiring comparison target data at this point.
[0049]
The point at which the data to be compared is obtained may vary depending on the receiving method and the receiving path. For example, when relatively high-quality reception such as cable broadcasting or satellite broadcasting is possible, data before Viterbi decoding is generally used as a comparison target (so-called Pre-Viterbi).
[0050]
Furthermore, in the present embodiment, the error correction of the broadcast signal is performed using a convolutional code (inner code) and Reed-Solomon code (outer code) combined with Viterbi decoding. It should not be understood that the error correction of the receiving apparatus is performed only by such a combination, and it is possible to use one or more other known error correction schemes.
[0051]
Information (reception status data) such as BER indicating the reception status is transmitted from the comparison determination unit 38 of the demodulation unit 13 to the control unit 14. The comparison process by the comparison determination unit 38 and the transmission process to the control unit 14 can be performed, for example, at each timing when one TS is processed by the RS decoding unit 37 or at another predetermined timing.
[0052]
When receiving the reception status data, the control unit 14 compares the reception status data with a predetermined threshold value, and if the BER value is larger (that is, if the reception C / N is reduced), the reception status is changed. When it is determined to be defective, a control signal is automatically sent to the switching unit 15 so as to select a TS corresponding to a program with a smaller data amount and a more robust SD quality (first quality).
[0053]
On the other hand, if the value of the BER is smaller than the threshold value (that is, if the reception C / N is large), it is determined that the reception status is good, and the HD quality with a large amount of data (second The control signal is transmitted to the switching unit 15 so as to select the TS corresponding to the (quality) program.
[0054]
The switching unit 15 receives the TSs corresponding to the plurality of programs from the RS decoding unit 37, selects only the TSs of a predetermined layer of the program according to the control signal received from the control unit 14, and sends the selected TS to the AV signal processing unit 16. Send out.
[0055]
Of course, in order to switch between such an HD quality program and an SD quality program, it is necessary to actually receive a broadcast signal in which programs corresponding to both qualities are hierarchized.
[0056]
The control unit 14 not only alternates between the two quality programs as described above, but also selects an output target program from among three or more different quality programs according to the level of the reception status. Thus, stepwise switching can be performed. For example, if the reception status level is good, a high-quality program corresponding to this level is output, and if the reception status level is medium, a normal-quality program corresponding to the level is output. If the level of the reception status is poor, it is possible to control so that a low-quality program corresponding to the level is output.
[0057]
By such switching control, the AV signal processing unit 16 is provided with a TS of an HD quality program having a large data amount when the reception status is poor, and is provided with an SD quality program having a small data amount when the reception status is good. A program TS is provided.
[0058]
In the present embodiment, an example has been described in which the program of the HD quality and the program of the SD quality are switched, that is, the programs of different image qualities are automatically switched depending on the difference in the reception status. Thus, it can be set so as to provide a difference in the quality of speech included in the program and the degree of other information related to the program.
[0059]
Upon receiving the TS, the AV signal processing unit 16 determines the type of data in the TS, and transmits the data to the corresponding decoder. For example, when the TS includes image data such as MPEG-2 (Moving Picture Experts Group-2) data, the image data is transmitted to the MPEG decoder, and audio data such as AC-3 is included. In this case, the signal is transmitted to an AC-3 (Audio Coding-3) decoder. Each decoder outputs input data to a corresponding output device. For example, the MPEG decoder receives the MPEG-2 data and outputs it to the display unit 17, and the AC-3 decoder decodes the AC-3 data and outputs it to an audio output device such as a speaker.
[0060]
Next, the operation of the switching control process in the control unit 14 will be described with reference to FIG. The processing software is assumed to be resident when the receiving device 10 is operating, and information (reception status data) regarding the reception status is transmitted from the comparison determination unit 38 at fixed time intervals. Monitor if you are. Further, in the control unit 14, other processes and other resident software also operate in parallel, but here, only the operation of this process will be described.
[0061]
The switching control process is started when the user ends a series of channel selection operations in the receiving device 10.
[0062]
In step S11, it is checked at regular intervals whether reception status data has been transmitted from the comparison determination unit 38 of the demodulation unit 13, and if it has been transmitted, it is acquired. Here, the reception status data is data representing a reception status of a broadcast such as a BER, for example. At this point, it is assumed that the receiving device 10 outputs the HDTV program of the specific channel to the display unit 17 or the like according to the user's channel selection.
[0063]
In step S12, if the value of the obtained reception status data indicates a status better than a predetermined value “QEF (Quasi Error Free: pseudo error free)”, the reception status is good and the current hierarchy program is drawn. It is determined that there is no problem, and the operation is continued as it is without performing any special control on the switching unit 15. Accordingly, the HD quality program is subsequently displayed on the display unit 17. At this time, the control unit 14 may check the switching unit 15 so as to continue taking in the TS of the current layer (step S15).
[0064]
Here, the QEF indicates the level of the reception status that, for example, when the TS is provided to the MPEG decoder, the number of uncorrectable errors is less than one per hour, and the reception status level is a predetermined value of the BER. Corresponds to the level represented by.
[0065]
When the switching unit 15 has selected a TS of an SD quality layer based on a past control signal from the control unit 14, the control unit 14 switches the TS to be output to a TS of an HD quality layer. 15 need to be controlled.
[0066]
In step S12, when the value of the obtained reception status data indicates a state worse than the threshold value provided near the QEF, the reception status may be degraded, and noise may be generated in the output image or audio.
[0067]
Therefore, in this case, the control unit 14 controls the switching unit 15 to select a TS of a more robust SD quality layer in step S13, and switches the display to the SD quality program in step S14.
[0068]
When the switching unit 15 has selected a TS of the SD quality layer based on a past control signal from the control unit 14, the control unit 14 controls the switching unit 15 to maintain the output target TS without switching. You need to control.
[0069]
Also, if an SD image quality program is output as it is to a large screen monitor for HD, mosquito noise tends to be noticeable as block noise accompanying image encoding other than reception errors due to noise. In such a case, control may be performed so that the image is displayed in an underscanning manner on the screen, that is, 100% from the corners of the video signal to make the noise less noticeable.
[0070]
Although the receiving apparatus and the receiving method of the present invention have been described above by taking the receiving apparatus of terrestrial digital broadcasting based on the ISDB-T system as an example, the present invention is not limited to this embodiment. Can be applied to various receiving devices. For example, for a broadcast in which a plurality of programs are transmitted according to another standard, the receiving apparatus and the receiving method of the present invention can be applied as long as the reception status of the broadcast can be detected by any method.
[0071]
【The invention's effect】
According to the present invention, the program to be output is automatically switched to another quality program according to the broadcast reception status without receiving a user instruction or the like.
[0072]
Further, according to the present invention, when the broadcast reception condition is not good, switching is performed so as to output a low-quality program with less transmission data. On the other hand, when the broadcast reception condition is good, more transmission data is required It is possible to switch to output a high-quality program, and to avoid interruption of broadcasting even if the reception condition deteriorates.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of hierarchization of one channel in BST.
FIG. 2 is a block diagram illustrating an example of a receiving device according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating an example of a receiving device according to an embodiment of the present invention.
FIG. 4 is a flowchart of an example of a process for controlling switching of a TS according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Receiving apparatus, 11 ... Antenna, 13 ... Demodulation part, 14 ... Control part (CPU), 15 ... Switching part, 16 ... AV signal processing part, 17 ... Display unit, 20 ... Tuner

Claims (12)

In a receiving device that receives a broadcast signal of a broadcast in which a plurality of programs having different qualities are transmitted and outputs a predetermined program among the plurality of programs,
Reception status determination means for determining the reception status of the broadcast signal,
Switching means for automatically switching the output program based on the determined reception status. The receiving device according to claim 1,
The receiving apparatus according to claim 1, wherein the reception status determination unit determines the reception status by comparing data of the received broadcast signal before error correction with data after error correction. The receiving device according to claim 2,
The receiving device, wherein the switching means selects a program of a quality corresponding to the determined reception status level from the plurality of programs, and switches an output target to the program of the quality. The receiving device according to claim 2,
When the reception status is lower than a predetermined reception level, the switching means selects a first quality program from the plurality of programs, switches an output target to the first quality program, and However, when the reception level is higher than the predetermined reception level, a program of a second quality higher than the first quality is selected from the plurality of programs, and an output target is switched to the program of the second quality. Receiving device. The receiving device according to claim 1,
A receiving device, wherein the plurality of programs are broadcast in a hierarchical manner. The receiving device according to claim 5,
A receiver according to claim 1, wherein said broadcast is terrestrial digital broadcast, and OFDM is used as a modulation method. In a receiving method of receiving a broadcast signal of a broadcast in which a plurality of programs having different qualities are transmitted and outputting a predetermined program among the plurality of programs,
Determining the reception status of the broadcast signal;
Automatically switching the output program based on the determined reception status. The receiving method according to claim 7,
The receiving method according to claim 1, wherein the receiving status determining step determines the receiving status by comparing data of the received broadcast signal before error correction with data after error correction. The receiving method according to claim 8,
The switching method, wherein the switching step selects a program of a quality corresponding to the determined reception status level from the plurality of programs, and switches an output target to the program of the quality. The receiving method according to claim 8,
In the switching step, when the reception status is lower than a predetermined reception level, a first quality program is selected from the plurality of programs, and an output target is switched to the first quality program. However, when the reception level is higher than the predetermined reception level, a program of a second quality higher than the first quality is selected from the plurality of programs, and an output target is switched to the program of the second quality. How to receive. The receiving method according to claim 7,
A receiving method, wherein the plurality of programs are broadcast in a hierarchical manner. The receiving method according to claim 11,
A receiving method, wherein the broadcast is terrestrial digital broadcast, and OFDM is used as a modulation method.

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