JP2006005461A - In-vehicle terrestrial digital broadcast receiving system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an "in-vehicle terrestrial digital broadcast receiving system" capable of reducing a cost, receiving a terrestrial digital broadcast wave transmitted in any modulation system and displaying contents thereof, and contributing to the improvement of a user merit. <P>SOLUTION: In the in-vehicle terrestrial digital broadcast receiving system 50 when a portable terminal 30 is connected to an in-vehicle terminal 10, broadcast waves of 13 Seg/12 Seg/1 Seg are received through the front end of the in-vehicle terminal 10, the broadcast waves of 13 Seg/12 Seg are demodulated through the back end (after a demodulating unit 18) of the in-vehicle terminal 10, and the broadcast wave of 1 Seg is demodulated through the back end (after a demodulating unit 38) of a portable terminal 30, and information included in broadcast waves of demodulated 13 Seg/12 Seg or 1 Seg is outputted via an in-vehicle display 1 and a speaker 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving system for enjoying a terrestrial digital broadcasting service, and more particularly to an in-vehicle terrestrial digital broadcasting receiving system.

  Digitalization of terrestrial television (TV) broadcasting has been promoted in Japan. Broadcasting has already started in the Tokyo, Osaka, and Nagoya areas since December 2003, and in 2011, the whole country was digitized and analog waves. Is scheduled to stop. In terrestrial digital TV broadcasting, as shown in FIG. 1, the frequency band of one channel is divided into 13 segments (1 segment: 429 kHz) and broadcast, and a different modulation method is adopted for each segment. Broadcast services for mobile / mobile reception can be provided simultaneously.

  Referring to “Example of segment / broadcast service combination” in FIG. 1B, since the specifications for mobile terminals have not been finalized at the beginning of the service, for example No. 1 after the specifications for mobile terminals have been established. There is a high possibility that it will be operated with 3 configurations (12 segments for HDTV and 1 segment for mobile terminals). The reason for this is that broadcasters want to improve HDTV image quality, but mobile services cannot be ignored. As a result of experiments conducted by domestic automobile manufacturers, mobile units (in-vehicle terminals) have been adopted by adopting the diversity method. However, there is a possibility that HDTV can be received. In addition, the content broadcast for mobile terminals in one segment will be the same as the content broadcast for HDTV, and the video encoding method (standard) is H.264. H.264 is currently being studied, and if it is adopted, there is a possibility that even a vehicle-mounted monitor can be seen sufficiently.

  In addition, the broadcast content (content) protection system differs between 13-segment / 12-segment broadcast and 1-segment broadcast. 13-segment / 12-segment content protection has already been operated in the B-CAS system using a B-CAS card intended for copyright protection as in the case of a fixed receiver. Regarding protection, the operation in the LSI embedded type is under consideration without using a physical medium such as a B-CAS card.

  As shown in “Example of combination of segment and broadcast service” in FIG. 1B, the receiver assumed for 13-segment / 12-segment broadcast is a type for fixed reception. However, the current situation is that 13-segment / 12-segment broadcasting services have already started, broadcasting for mobiles is not performed, and image quality is good. Receiving segment / 12 segment broadcasts has become the mainstream. Therefore, when a one-segment broadcasting service is started, it is fully expected that a receiver that receives 13-segment / 12-segment / 1-segment broadcasting will be a standard model for in-vehicle use. In addition, a one-segment broadcasting service is scheduled to be provided for mobile terminals (receivers) from around 2005. KDDI, NTT, etc. are developing prototypes jointly with terminal manufacturers, PDA integrated type has already been announced.

  Hereinafter, a vehicle-mounted terrestrial digital TV broadcast receiver and a portable terrestrial digital TV broadcast receiver according to the related art will be described with reference to FIGS. 2 and 3, respectively.

  As shown in FIG. 2, the in-vehicle digital terrestrial TV broadcast receiver 10a of the state of the art includes two systems of antennas 13a and 13b, tuner units 14a and 14b, OFDM (orthogonal frequency division multiplexing) demodulation units 15a and 15b, and thereafter A diversity combining unit 16, an error correcting unit 17, an MPEG2-TS (Transport Stream) demodulating unit 18, an audio decoder 19 and a video decoder 20 connected in stages are provided. In this configuration, the terrestrial digital TV broadcast waves received by the antennas 13a and 13b are selected through the corresponding tuner units 14a and 14b, and then passed through the corresponding OFDM demodulation units 15a and 15b. It is converted into digital data TS in the MPEG2-TS format, and diversity combined through the diversity combining unit 16. Further, the diversity-combined TS format digital data TS is subjected to predetermined error detection and correction processing through the error correction unit 17 and then to the audio signal AS through the MPEG2-TS demodulation unit (TS demodulation LSI) 18. The video signal VS is separated. The separated audio signal AS and video signal VS are decoded by the audio decoder 19 and the video decoder 20, respectively, and output to the outside. The audio signal AS is digital / analog (D / A) converted and then output as sound from a speaker (not shown), and the video signal VS is supplied to a display (not shown) and a video is displayed on the screen. Is displayed.

  The reason why the two systems are used in the configuration of FIG. 2 is to improve the reception performance and to allow the in-vehicle receiver to watch 13 segment / 12 segment broadcast (HDTV). One-segment broadcasting (simple moving picture) can be received with a single system configuration (antenna, tuner unit and OFDM demodulation unit) and without performing diversity combining processing.

  On the other hand, as shown in FIG. 3, the portable terrestrial digital TV broadcast receiver 30a according to the state of the art includes an antenna 33, a tuner unit 34, an OFDM demodulation unit 35, and an error correction unit 36 connected to the subsequent stage. An MPEG2-TS demodulator 38, an audio decoder 39, and a video decoder 40 are provided. In this configuration, the terrestrial digital TV broadcast wave received by the antenna 33 is selected as a desired broadcast wave through the tuner unit 34, converted into MPEG2-TS format digital data TS through the OFDM demodulator 35, and an error correction unit. After a predetermined error detection and correction process is performed through 36, it is separated into an audio signal AS and a video signal VS through an MPEG2-TS demodulator (TS demodulation LSI) 38, and further decoded by an audio decoder 39 and a video decoder 40. And output to the outside.

As a technique related to the above-described conventional technique, for example, as described in Patent Document 1, in a portable wireless communication device used in a portable / automobile telephone system or the like, a portable wireless device body is mounted on an in-vehicle adapter. Sometimes, the reception is switched from the antenna of the portable wireless device main body to the antenna of the in-vehicle adapter.
JP-A-6-224809

  The reception area of 1-segment broadcast is narrower than the reception area of 13-segment / 12-segment broadcast. For this reason, in-vehicle terminals having a function of receiving terrestrial digital TV broadcasts can also receive 1-segment broadcasts in addition to 13-segment / 12-segment broadcasts in terms of area. Therefore, when a 13-segment / 12-segment broadcast cannot be received for some reason, a configuration that can receive a one-segment broadcast is ideal. For this purpose, a special in-vehicle LSI is used as described below. Is required, leading to high costs.

  First, regarding the audio format, both 13-segment / 12-segment broadcasting and 1-segment broadcasting are both MPEG2 Audio AAC (Advanced Audio Coding), but the 13-segment / 12-segment video format is MPEG2 Video, and one-segment video. H.264 is currently being considered for the format. In other words, since the video encoding methods are different from each other, it is necessary to mount an LSI corresponding to both types on the in-vehicle terminal. This leads to higher costs.

  In addition, middleware for software development is attached to LSI, but the table to be referenced differs between 13 segment / 12 segment broadcast and 1 segment broadcast, so LSI manufacturers have 13 segment / 12 segment for fixed reception. Middleware for mobile phones and middleware for 1 segment for mobile reception. When 13-segment / 12-segment broadcast and 1-segment broadcast are received by one LSI, it is necessary to have the LSI manufacturer newly develop middleware corresponding to both (high cost). At present, most manufacturers specialize in either fixed reception or portable reception, and few manufacturers are developing both.

  Furthermore, since the content protection system differs between 13-segment / 12-segment broadcasting and 1-segment broadcasting, in order to receive both, an LSI manufacturer will develop a new LSI that supports both systems. Necessary (high cost).

  On the other hand, for mobile terminals equipped with a function for receiving terrestrial digital TV broadcasts, a 1-segment broadcast is easier to receive than a 13-segment / 12-segment broadcast, but a mobile terminal (mobile phone / PDA) is used as a vehicle. When mounted and used, it is difficult for the mobile terminal antenna and tuner of the state of the art to stably receive during movement of the vehicle. Moreover, since the display screen of a portable terminal is generally small, there is a disadvantage that the display content is difficult to see.

  The present invention was created in view of the problems in the prior art, and can reduce costs and receive and display the contents of terrestrial digital broadcast waves transmitted by any modulation method. An object is to provide an in-vehicle terrestrial digital broadcast receiving system that can contribute to improvement of user merit.

  In order to solve the above-described problems of the prior art, according to the present invention, all segments or a specific number of segments among a plurality of segments obtained by dividing a frequency band of one channel are transmitted with the same modulation scheme. A first front wave capable of receiving a first broadcast wave coming in and a second broadcast wave included in one of the plurality of segments and transmitted in a modulation scheme different from the first broadcast wave An in-vehicle terminal having an end and a first back end capable of demodulating the first broadcast wave; a second front end capable of receiving the second broadcast wave; and demodulating the second broadcast wave A portable terminal having a second back end capable of being connected to the in-vehicle terminal, and information output means for outputting video information and audio information in a visible mode and an audible mode, respectively. When connected to the terminal, the first and second broadcast waves are received through the first front end, the first broadcast wave is demodulated through the first back end, and the second In-vehicle characterized in that a broadcast wave is demodulated through the second back end and information included in the demodulated first broadcast wave or second broadcast wave is output via the information output means. A terrestrial digital broadcast receiving system is provided.

  According to the configuration of the in-vehicle terrestrial digital broadcast receiving system according to the present invention, the second broadcast wave received on the in-vehicle terminal side is used by using the second back end (dedicated TS demodulation LSI) on the portable terminal side. Since demodulation is performed, it is not necessary to newly develop backends (special LSIs) corresponding to the first and second broadcast waves for in-vehicle use, and the cost can be reduced.

  In addition, since the second broadcast wave is received on the in-vehicle terminal side, it can be stably received even while the vehicle is moving, and the contents of the broadcast wave can be displayed on a relatively large-screen on-vehicle display. Since it can be displayed on (information output means), the display content is easy to see. This greatly contributes to improvement of user merit.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 4 is a block diagram showing the configuration of an in-vehicle digital terrestrial broadcast receiving system according to an embodiment of the present invention.

  The in-vehicle terrestrial digital broadcast receiving system 50 according to the present embodiment includes an in-vehicle terminal (terrestrial digital TV broadcast receiver) 10, a portable terminal (terrestrial digital TV broadcast receiver) 30 that can be connected to the in-vehicle terminal 10, A display 1, an amplifier unit 2, and a speaker 3 are operatively connected to the terminal 10.

  The in-vehicle terminal 10 includes, as will be described later, a control unit 11 constituted by a microcomputer for controlling processing related to reception and switching of terrestrial digital TV broadcast waves, and information set or selected by the user. Operation unit (remote control, touch panel, etc.) 12, two antennas 13a and 13b, tuner units 14a and 14b and OFDM demodulation units 15a and 15b, a diversity combining unit 16 connected in the subsequent stage, and an error A correction unit 17, an MPEG2-TS demodulation unit 18, an audio decoder 19, a video decoder 20, and an A / V selector 21 are provided. On the other hand, the mobile terminal 30 is connected to a control unit 31 that cooperates with the control unit 11 of the in-vehicle terminal 10, an operation unit 32, a single-system antenna 33, a tuner unit 34, and an OFDM demodulation unit 35, and the subsequent stage. An error correction unit 36, a TS switching unit 37, an MPEG2-TS demodulation unit 38, an audio decoder 39, a video decoder 40, a speaker 41, and a display 42 are provided.

  In this embodiment, the in-vehicle terminal 10 is basically adapted to receive a 13-segment / 12-segment broadcast wave (first broadcast wave) and a 1-segment broadcast wave (second broadcast wave). On the other hand, the mobile terminal 30 is adapted to receive a one-segment broadcast wave (second broadcast wave). The MPEG2-TS interface between the in-vehicle terminal 10 and the portable terminal 30 is an IEEE 1394 or USB 2.0 interface standard, and uses a right protection function conforming to DTCP (Digital Transmission Content Protection).

  In the in-vehicle digital terrestrial broadcast receiving system 50 configured as described above, the in-vehicle display 1 and the speaker 3 are used as “information output unit”, the A / V selector 21 is used as “output information switching unit”, and the TS switching unit. Reference numeral 37 corresponds to “reception broadcast switching means”. In the in-vehicle terminal 10, the antennas 13 a and 13 b, the tuner units 14 a and 14 b, and the OFDM demodulation units 15 a and 15 b constitute a “front end”, and a portion on the rear stage after the MPEG2-TS demodulation unit 18 is a “back end”. Configure. Similarly, also in the portable terminal 30, the antenna 33, the tuner unit 34, and the OFDM demodulator 35 constitute a “front end”, and the subsequent part after the MPEG2-TS demodulator 38 constitutes a “back end”.

  In the in-vehicle digital terrestrial broadcast receiving system 50 according to the present embodiment, when the in-vehicle terminal 10 operates stand-alone (independently), a 13-segment / 12-segment broadcast wave is transmitted through its own front end as in the prior art. It receives and demodulates this broadcast wave through its own backend. The demodulated 13 segment / 12 segment broadcast wave is output to the in-vehicle display 1 and the speaker 3 via the A / V selector 21. When the mobile terminal 30 operates in a stand-alone manner, as in the prior art, it receives a one-segment broadcast wave through its own front end, demodulates this broadcast wave through its own back end, and then uses its own speaker. 41 and the display 42. In this case, the TS switching unit 37 is switched and connected to the output terminal of the error correction unit 36 on the mobile terminal 30 side.

  Next, the processing related to the reception and switching of the broadcast service performed in the in-vehicle digital terrestrial broadcast receiving system 50 according to the present embodiment will be described with reference to FIG. 5 showing an example of the processing flow.

  In the first step S1, when the mobile terminal 30 is connected to the in-vehicle terminal 10, the control unit 11 of the in-vehicle terminal 10 detects the connection and notifies the control unit 31 of the mobile terminal 30 to that effect.

  In the next step S <b> 2, the connection of the TS switching unit 37 is switched by the control unit 31 in the mobile terminal 30 so that a one-segment broadcast wave received on the in-vehicle terminal 10 side can be received. Thus, the one-segment broadcast wave supplied from the in-vehicle terminal 10 side is connected to the back end of the portable terminal 30, and the one-segment broadcast wave received through the front end of the portable terminal 30 is Detached from.

  In the next step S <b> 3, the in-vehicle terminal 10 receives a 13 Seg / 12 Seg / 1 Seg (Seg is a segment) broadcast wave through the front end based on the control from the control unit 11. At this time, the control unit 11 monitors the reception state of the 13-segment / 12-segment broadcast wave, that is, the reception level (quality), through communication performed with the OFDM demodulation units 15a and 15b. The broadcast wave received through the front end, that is, each digital data TS output from the OFDM demodulator 15a, 15b is diversity-combined through the diversity combiner 16, and further subjected to predetermined error detection and correction through the error corrector 17. After the processing is performed, the signal is output to the MPEG2-TS demodulation unit 18 of the in-vehicle terminal 10 and the TS switching unit 37 in the mobile terminal 30.

  In the next step S4, in the control unit 11 of the in-vehicle terminal 10, whether or not the reception level of the 13-segment / 12-segment broadcast wave is maintained at a predetermined level or higher based on the monitoring result (YES). Determine whether. If the determination result is YES, the process proceeds to step S5, and if the determination result is NO, the process proceeds to step S11.

  In step S5 (when the reception level of the 13 segments / 12 segments is maintained at or above a prescribed level), the control unit 11 of the in-vehicle terminal 10 uses the 13 segment / segment based on the user selection information input from the operation unit 12. It is determined which of the 12 segment broadcast wave and the 1 segment broadcast wave is selected. If a 13-segment / 12-segment broadcast wave is selected, the process proceeds to step S6. If a 1-segment broadcast wave is selected, the process proceeds to step S7.

  In step S6, the 13-segment / 12-segment broadcast wave (audio signal AS, video signal VS) demodulated by the control unit 11 in the in-vehicle terminal 10 through the back end of the in-vehicle terminal 10 (MPEG2-TS demodulation unit 18 and later). The connection of the A / V selector 21 is switched so that it can be output. As a result, the 13-segment / 12-segment broadcast wave is connected to the in-vehicle display 1 and the speaker 3, and the 1-segment broadcast wave demodulated through the back end (after the MPEG2-TS demodulator 38) of the mobile terminal 30 is , Separated from the in-vehicle display 1 and the speaker 3. Thereafter, the process proceeds to step S8.

  On the other hand, in step S7, the control unit 11 in the in-vehicle terminal 10 allows the A / V selector 21 to output a one-segment broadcast wave (audio signal AS, video signal VS) demodulated through the back end of the portable terminal 30. Switch connection. Thus, the one-segment broadcast wave is connected to the in-vehicle display 1 and the speaker 3, and the 13-segment / 12-segment broadcast wave demodulated through the back end of the in-vehicle terminal 10 is converted into the in-vehicle display 1 and the speaker 3. Detached from. Thereafter, the process proceeds to step S8.

  In the next step S8, the selected broadcast wave (13-segment / 12-segment broadcast wave or 1-segment broadcast wave) is sent to the in-vehicle display 1 and the speaker 3 (amplifier unit 2) via the A / V selector 21. Connecting. As a result, the information included in the broadcast wave is displayed as a video on the screen of the display 1, amplified through the amplifier unit 2, and then output as sound from the speaker 3. Then, this processing flow is “end”.

  On the other hand, in step S11 (when the reception level of 13 segments / 12 segments falls below a prescribed level), the in-vehicle terminal 10 outputs a broadcast wave of one segment demodulated through the back end of the mobile terminal 30 by the control unit 11. The connection of the A / V selector 21 is switched so that it can be performed. Thus, the one-segment broadcast wave is connected to the in-vehicle display 1 and the speaker 3, and the 13-segment / 12-segment broadcast wave demodulated through the back end of the in-vehicle terminal 10 is converted into the in-vehicle display 1 and the speaker 3. Detached from. That is, switching from the 13 segment / 12 segment broadcast service to the 1 segment broadcast service is performed. While the broadcast service is being switched, the control unit 11 monitors the reception state of the 13-segment / 12-segment broadcast wave.

  In the next step S12, the control unit 11 of the in-vehicle terminal 10 determines whether or not the 13-segment / 12-segment broadcast wave reception level has recovered to a predetermined level or more (YES) based on the monitoring result (NO). judge. If the determination result is YES, the process proceeds to step S13, and if the determination result is NO, the determination process is repeated until the level is recovered to a predetermined reception level or higher.

  In the next step S13, the connection of the A / V selector 21 is switched by the control unit 11 in the in-vehicle terminal 10 so that the 13-segment / 12-segment broadcast wave demodulated through the back end of the in-vehicle terminal 10 can be output. Accordingly, the 13-segment / 12-segment broadcast wave is connected to the in-vehicle display 1 and the speaker 3, and the one-segment broadcast wave demodulated through the back end of the mobile terminal 30 is converted into the in-vehicle display 1 and the speaker 3. Detached from. That is, switching from the 1-segment broadcasting service to the 13-segment / 12-segment broadcasting service is performed. Similarly, while the broadcast service is being switched, the control unit 11 monitors the reception state of the 13-segment / 12-segment broadcast wave. Then, it returns to step S4 and repeats said process.

  In the above processing flow, switching from the 13 segment / 12 segment to the 1 segment broadcasting service is performed according to the reception level of the broadcast wave of the 13 segment / 12 segment, or vice versa. However, it goes without saying that the mode of switching of the broadcast service is not limited to this. For example, a 13-segment / 12-segment broadcast or a 1-segment broadcast may be fixed based on a setting operation by the user. In this case, steps S4 and S11 to S13 are not necessary in the above processing flow.

  As described above, according to the configuration of the in-vehicle terrestrial digital broadcast receiving system 50 according to the present embodiment, various advantages can be obtained as described below.

  First, in the prior art, when a 13-segment / 12-segment broadcast cannot be received, a special on-vehicle LSI is required in order to receive a one-segment broadcast, and an increase in cost is inevitable. . On the other hand, in the present invention (embodiment), a 1-segment broadcast wave received on the in-vehicle terminal 10 side is used by using a 1-segment dedicated TS demodulation LSI (MPEG2-TS demodulator 38) provided in the mobile terminal 30. Since demodulation is performed, there is no need to newly develop a backend (special LSI) corresponding to 13 segments / 12 segments / 1 segment for in-vehicle use, and the cost can be greatly reduced.

  In reality, in order for LSI manufacturers to develop a new 13-segment / 12-segment / 1-segment backend for in-vehicle use, it is necessary to expand the in-vehicle market to the extent that profits are available to LSI manufacturers. It takes time. On the other hand, according to the present invention (embodiment), it is possible to receive 13 segment / 12 segment / 1 segment broadcasts at an early stage. This greatly contributes to improvement of user merit.

  Moreover, with the current technology, even a mobile terminal dedicated to one segment is difficult to receive stably during the movement of the vehicle due to the performance of its front end, and the display screen is generally small. Therefore, there is a problem that it is difficult to see the display contents. On the other hand, in the present invention (embodiment), since the in-vehicle terminal 10 receives a one-segment broadcast wave, it can be stably received even while the vehicle is moving, and the broadcast wave (1 Since the content of the segment) is displayed on the vehicle-mounted display 1 having a relatively large screen, the display content is easy to see. This also contributes to improvement of user merit.

  Furthermore, in the future, most mobile phones will have a built-in 1-segment receiver, so there are few people who do not have an in-vehicle digital terrestrial TV broadcast receiver but do not have a mobile phone. . Therefore, according to the present invention (embodiment), the in-vehicle device can draw in a mobile phone user who is a larger market.

It is a figure for demonstrating a terrestrial digital TV broadcast system. It is a block diagram which shows roughly the structure of the vehicle-mounted digital terrestrial TV broadcast receiver based on a prior art. It is a block diagram which shows roughly the structure of the portable terrestrial digital TV broadcast receiver which concerns on a prior art. It is a block diagram which shows the structure of the vehicle-mounted digital terrestrial broadcast receiving system which concerns on one Embodiment of this invention. It is a flowchart which shows the process which concerns on reception of the broadcast service performed in the system of FIG. 1, and its switching.

Explanation of symbols

1 ... In-vehicle display (information output means),
3. Car-mounted speaker (information output means),
10: In-vehicle terminal (terrestrial digital TV broadcast receiver),
11, 31 ... control unit (microcomputer),
12, 32 ... operation unit,
13a, 13b, 33 ... antenna,
14a, 14b, 34 ... tuner section,
15a, 15b, 35 ... OFDM demodulator,
18, 38 ... MPEG2-TS demodulator,
19, 39 ... audio decoder,
20, 40 ... Video decoder,
21 ... A / V selector (output information switching means),
37 ... TS switching section (received broadcast switching means),
41 ... Speaker (for mobile terminal),
42 ... display (on mobile device),
50. In-vehicle terrestrial digital broadcast receiving system,
TS: MPEG2-TS format digital data,
AS ... Audio signal,
VS: Video signal.

Claims (5)

A first broadcast wave included in all segments or a specific number of segments among a plurality of segments obtained by dividing the frequency band of one channel and transmitted by the same modulation method, and one of the plurality of segments A first front end capable of receiving a second broadcast wave included in a segment and transmitted by a modulation scheme different from the first broadcast wave; and a first back capable of demodulating the first broadcast wave An in-vehicle terminal with an end, and
A mobile terminal comprising a second front end capable of receiving the second broadcast wave, and a second back end capable of demodulating the second broadcast wave;
An information output means connected to the in-vehicle terminal and outputting video information and audio information in a visible mode and an audible mode, respectively;
When the portable terminal is connected to the in-vehicle terminal, the first and second broadcast waves are received through the first front end, and the first broadcast wave is demodulated through the first back end. In addition, the second broadcast wave is demodulated through the second back end, and the information included in the demodulated first broadcast wave or the second broadcast wave is output via the information output means. An in-vehicle digital terrestrial broadcast receiving system.   The portable terminal receives the second broadcast wave received through the second front end or the second broadcast wave received through the first front end selectively connected to the second back end. The in-vehicle digital terrestrial broadcast receiving system according to claim 1, further comprising broadcast switching means.   The in-vehicle terminal selectively outputs the first broadcast wave demodulated through the first back end or the second broadcast wave demodulated through the second back end to the information output means. The in-vehicle terrestrial digital broadcast receiving system according to claim 1, further comprising: means.   In the in-vehicle terminal, the reception state of the first broadcast wave received through the first front end is monitored, and when the reception level of the broadcast wave is lower than a predetermined level, the output information switching means 4. The in-vehicle terrestrial digital broadcast receiving system according to claim 3, wherein output switching from the first broadcast wave to the second broadcast wave is controlled.   In the in-vehicle terminal, when the reception level of the broadcast wave is recovered to a predetermined level or more based on the monitoring result of the reception state of the first broadcast wave, the second broadcast is sent to the output information switching unit. 5. The in-vehicle terrestrial digital broadcast receiving system according to claim 4, wherein output switching from the wave to the first broadcast wave is controlled.

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