JP2007082051A - Vehicle-mounted digital tv receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize installation without excessive external wiring and avoid diffuse of driver's attention, by recognizing that a vehicle, on which a vehicle mounted digital TV receiver is mounted, is in running state through the vehicle-mounted digital TV itself without depending on a measured valued fed from the exterior, an operating position (its representative signal) of parking brake or the like, and restricting receive of operation on the self operation unit based on this recognition. <P>SOLUTION: As to measured values in real time C/N, a mean rate for every one-second time section is calculated and both mean rates (modulus) for every adjoining time section are compared. Based on the compared result, a variation width of both sections is over a constant value (for example, 2dB), it is determined as in running state without depending on the detected signal from the exterior or the like. Then, the receive of operation on an operation unit is restricted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an in-vehicle digital television receiver having a function of restricting external operations when a vehicle is traveling, and particularly recognizes that the vehicle is in a traveling state from the outside. The present invention relates to an on-vehicle digital television receiver that can be supplied within the device without giving up signals.

  In recent years, in-vehicle television receivers are becoming popular. Digital TV receivers are increasingly being used for in-vehicle use, but, as in general equipment used for in-vehicle use, at least for functions that may distract the driver's attention, When the vehicle is in a running state, it is necessary to give priority to ensuring safety by automatically applying a certain restriction.

There are many technologies for in-vehicle television receivers that restrict various functions so that safe driving is not hindered when the vehicle is running.
In an in-vehicle device such as a car navigation system, in general, a vehicle speed detection signal from a vehicle speed detector provided in a vehicle or a parking brake signal from a parking brake state detection mechanism is supplied to the device, and the A configuration is adopted such that the operation of the operation switches becomes ineffective depending on the state.

Specific proposals have also been made. For example, the information indicating the parking brake setting of the car, the accessory input information of the car, the information indicating the time-up of the timer circuit is supplied to the microcomputer, and the microcomputer performs a logical product of the information indicating the parking brake setting and the accessory input information, or Obtain the logical product of the accessory input information and the timer circuit time-up information, and supply an image display switching signal for normal image display on the display surface only when one of the logical product outputs is obtained. Thus, a technique has been proposed in which the driver's attention is concentrated on the image on the display surface during driving so as not to obscure safe driving (see, for example, Patent Document 1).
JP-A-6-165080 (paragraphs 0018 to 0025, FIG. 1)

  Any of the products described above and the proposed in-vehicle television receivers require wiring for supplying a detection signal from a parking brake state detection mechanism or the like provided on the vehicle side to the television receiver. The installation work on the vehicle becomes very complicated. On the other hand, there is also a concern that such external wiring may be disconnected or grounded by the user's willingness to effectively perform a desired operation at any time without any restriction on the function of the television receiver. Not at all.

  The present invention has been made in view of the circumstances as described above, and recognizes that the vehicle is in a running state in the own aircraft without hesitating the supply of a separate signal from the outside, and detects the running state. Therefore, it is possible to simplify the installation work and eliminate the possibility of modification by not having the wiring itself that is the target of modification such as cutting or grounding. An object of the present invention is to provide an in-vehicle digital television receiver.

In order to solve the above-described problems, the present application proposes the following techniques.
(1) A tuner unit that performs channel selection processing related to a received signal supplied from an antenna, an OFDM demodulation processing unit that receives and outputs a transport stream in response to the output of the tuner unit, and an output of the OFDM demodulation processing unit An in-vehicle digital device having a video processing unit that forms and outputs a signal suitable for display based on the display, a display that displays video based on the output of the video processing unit, and an operation unit that receives an operation by a user A television receiver for detecting C / N (carrier power to noise power ratio) from the OFDM demodulation processing unit, and monitoring a change in detection output of the C / N detection unit; When it is recognized that a specific change having a correlation with the traveling of the vehicle equipped with the in-vehicle digital television receiver is detected, the acceptance of the operation to the operation unit is limited. Automotive digital television receiver characterized by comprising a control unit for emitting a limit command.

  According to the in-vehicle digital television receiver of (1) above, the C / N is detected from the OFDM demodulation processing unit by the C / N detection unit owned by the self, and the on-vehicle digital television receiver is based on the change appearing in the detection output. Since it is determined whether or not a vehicle equipped with a digital television receiver is in a running state, and the control unit issues a restriction command for limiting the acceptance of operations to the operation unit based on the determination, the vehicle travels. Recognizing that the vehicle is in a state can be performed within the aircraft without hesitating to supply a separate signal from the outside. Accordingly, the wiring for external signal supply for detecting the running state is not required, so that the mounting work can be simplified, and the wiring itself that is the target of modification such as cutting or grounding is not modified from the beginning. There is no fear.

(2) The in-vehicle digital television according to (1), wherein the display unit is configured to receive a restriction command from the control unit, and does not display the video when receiving the restriction command. Receiver.
According to the in-vehicle digital television receiver of (2) above, in particular, in the operation by the in-vehicle digital television receiver of (1), a restriction command issued when the vehicle is substantially in a running state is received. In such a case, the display unit does not display an image, so that the risk of distracting the driver's attention is further reduced.

(3) The video processing unit is configured to receive a restriction command from the control unit, and when receiving the restriction command, stops supplying a signal for displaying a video to the display unit. The on-vehicle digital television receiver of (1), which is characterized.
According to the in-vehicle digital television receiver of (3) above, in particular, in the operation of the in-vehicle digital television receiver of (1), a restriction command issued when the vehicle is substantially in a running state is received. In such a case, the video processing unit stops supplying the signal for displaying the video to the display unit. As a result, the video is not displayed on the display unit, and the possibility that the driver's attention is distracted is further reduced.

(4) A tuner unit that performs channel selection processing on a received signal supplied from an antenna, an OFDM demodulation processing unit that receives and outputs a transport stream in response to the output of the tuner unit, and an output of the OFDM demodulation processing unit An in-vehicle digital device having a video processing unit that forms and outputs a signal suitable for display based on the display, a display that displays video based on the output of the video processing unit, and an operation unit that receives an operation by a user A television receiver that detects BER from the OFDM demodulation processor; a C / N detector that detects C / N (carrier power to noise power ratio) from the OFDM demodulation processor; A fading frequency is estimated based on the detection output of the BER detection unit, and when the estimated fading frequency exceeds a predetermined value, and the estimated fading frequency When it is recognized that a specific change situation having a correlation with the running of the vehicle equipped with the in-vehicle digital television receiver appears in the detection output of the C / N detection unit without the ging frequency exceeding a predetermined value A vehicle-mounted digital television receiver comprising: a control unit that issues a restriction command for restricting acceptance of operations to the operation unit at any time.

  According to the on-vehicle digital television receiver of (4) above, whether the fading frequency is estimated based on the detection output of the BER detection unit owned by the self and the estimated fading frequency is within a predetermined range. Depending on whether or not it is estimated that the vehicle on which the in-vehicle digital television receiver is mounted is in a running state, the vehicle is estimated to be stopped as long as it depends on the fading frequency. The C / N is detected from the OFDM demodulation processing unit by the / N detection unit, and the accuracy of the determination is increased by determining whether or not the vehicle is in the running state based on the change appearing in the detection output. Relying on the high determination, the control unit issues a restriction command that restricts the acceptance of operations to the operation unit, so that the recognition that the vehicle is in a running state is supplied from the outside. Can reliably complete the apparatus itself without was 俟. Accordingly, the wiring for external signal supply for detecting the running state is not required, so that the mounting work can be simplified, and the wiring itself that is the target of modification such as cutting or grounding is not modified from the beginning. There is no fear.

(5) The in-vehicle digital television according to (4), wherein the display unit is configured to receive a restriction command from the control unit, and does not display the video when receiving the restriction command. Receiver.
According to the in-vehicle digital television receiver of (5) above, in particular, in the operation of the in-vehicle digital television receiver of (4), a restriction command issued when the vehicle is substantially in a running state is received. In such a case, the display unit does not display an image, so that the risk of distracting the driver's attention is further reduced.

(6) The video processing unit is configured to receive a restriction command from the control unit, and when receiving the restriction command, stops supplying a signal for displaying a video to the display unit. (4) The on-vehicle digital television receiver characterized by the above.
According to the in-vehicle digital television receiver of (6) above, in particular, in the operation by the in-vehicle digital television receiver of (4), a restriction command issued when the vehicle is substantially in a running state is received. In such a case, the video processing unit stops supplying the signal for displaying the video to the display unit. As a result, the video is not displayed on the display unit, and the possibility that the driver's attention is distracted is further reduced.

(7) A tuner unit that performs channel selection processing related to a received signal supplied from an antenna, an OFDM demodulation processing unit that receives and outputs a transport stream in response to the output of the tuner unit, and an output of the OFDM demodulation processing unit An in-vehicle digital device having a video processing unit that forms and outputs a signal suitable for display based on the display, a display that displays video based on the output of the video processing unit, and an operation unit that receives an operation by a user A change in state quantity having a specific correlation with a moving state of a vehicle on which the in-vehicle digital television receiver is mounted based on data generated in the process of the OFDM demodulation processing unit. A control unit that recognizes and issues a restriction command that restricts acceptance of an operation to the operation unit based on the recognition. Digital television receiver.

  According to the on-vehicle digital television receiver of (7) above, the movement status of the vehicle on which the on-vehicle digital television receiver is mounted based on the data generated in the process of the OFDM demodulation processing unit owned by itself. And a change in the state quantity having a specific correlation is determined, and whether or not the vehicle is in a running state is determined based on the recognition, and the control unit accepts an operation to the operation unit based on the determination. In order to issue a restriction command for restriction, it is possible to recognize that the vehicle is in a running state within the own aircraft without hesitating supply of a separate signal from the outside. Accordingly, the wiring for external signal supply for detecting the running state is not required, so that the mounting work can be simplified, and the wiring itself that is the target of modification such as cutting or grounding is not modified from the beginning. There is no fear.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings to be referred to below, for the sake of convenience, the main part that is the subject of the description is exaggerated as appropriate, and other than the main part is appropriately simplified or omitted.
FIG. 1 is a block diagram showing the configuration of an in-vehicle digital television receiver as an embodiment of the present invention. In FIG. 1, in an in-vehicle digital television receiver 100 as one embodiment of the present invention, an antenna 101 for reception is connected to a tuner unit 102, and an output in which a predetermined channel selection is performed by the tuner unit 102. The signal (IF output) is subjected to OFDM demodulation processing by an OFDM demodulation processing unit 120 shown by a one-dot chain line, and a transport stream (TS) as a demodulation output is generated and output.

The video processing unit 130 supplied with the transport stream (TS) forms and outputs a signal suitable for display based on the supplied transport stream (TS). A video is displayed on the display 140 based on the output of the video processing unit 130.
The above-described OFDM demodulation processing unit 120 includes an OFDM demodulation unit 121 that performs an OFDM demodulation process for generating a transport stream (TS) based on the output signal (IF output) of the tuner unit 102 supplied to the OFDM demodulation processing unit 120. A reception level detection unit 122 that detects a reception level based on processing data in the demodulation unit 121, a BER detection unit 123 that detects a BER based on processing data in the OFDM demodulation unit 121, and an OFDM A C / N detector 124 that detects C / N based on the data of the process in the demodulator 121 is provided.

  An operation unit 150 having an operation switch for receiving various operations by a user is provided, and an output of the operation unit 150 is supplied to a system controller 160 mainly composed of a microprocessor. The system controller 160 issues a command to the tuner unit 102 in response to an operation such as channel selection on the operation unit 150 to perform a channel selection operation. Also, the system controller 160 receives the reception level detection unit 122, the BER detection unit 123, and the C / N detection unit 124 exchanges signals to form a recognition related to the reception status, and based on the recognition, issues a restriction command to the operation unit 150 or further to the display unit 140 to the video processing unit 130 to operate The reception of operations to the unit 150 is limited, or further, the display unit 140 to the video processing unit 130 are shifted to an inoperative state. The operation of the system controller 160 will be described later.

  FIG. 2 is a block diagram showing a configuration of the in-vehicle digital television receiver of FIG. 1 as viewed from the viewpoint of a process for obtaining a transport stream (TS) from radio waves detected by the antenna 101. In FIG. 2, corresponding parts to those in FIG. 1 are partially indicated by the same reference numerals, but the functional units corresponding to the components in the OFDM demodulation processing unit 120 in FIG. Because of the concept of function, another reference number is assigned.

  Since the configuration itself shown in FIG. 2 is a general one, each function will be briefly described. That is, the receiving antenna 101 is connected to the tuner unit 102, and the gain control is performed by the AGC circuit 103 in the next stage with respect to the signal output selected by the tuner unit 102. The output signal of the AGC circuit 103 is supplied to a known Viterbi decoding error correction circuit 104, where the signal is examined over a certain length, and the most probable code is selected from the sequence of the code strings and decoded. The

  The output signal of the Viterbi decoding error correction circuit 104 is further supplied to the Reed-Solomon (RS) decoding error correction circuit 105 in the next stage, and the error remaining after Viterbi decoding is corrected by RS code by spreading the error by byte-by-byte interleaving. Is given. That is, double error correction of the RS code and the convolutional code is performed on the output signal of the AGC circuit 103 described above. A so-called interleaving is a method of rearranging the order of sending data so that the characteristics of these error correction codes can be sufficiently obtained.

  The output of the RS decoding error correction circuit 105 is a TS (transport stream) that is a video output of the digital television receiver 100, and is supplied to a display such as a liquid crystal, plasma, or cathode ray tube. On the other hand, the input signal and output signal of the Viterbi decoding error correction circuit 104 and the input signal and output signal of the RS decoding error correction circuit 105 are supplied to the BER detection unit 106, respectively. The BER value is calculated by comparing the input signal and output signal of the Viterbi decoding error correction circuit 104, and similarly, the BER value is also calculated by comparing the input signal and output signal of the RS decoding error correction circuit 105. Yes.

  In this example, the BER detection unit 106 calculates a BER value based on an input / output comparison process of the Viterbi decoding error correction circuit 104 (if a code is necessary) or detects an RS decoding error correction. The BER value can be appropriately obtained by selecting whether to calculate the BER value based on the input / output comparison processing of the circuit 105 (if the code is necessary) according to various conditions assumed at that time. Therefore, it can respond flexibly and appropriately to various situations.

Also, a reception level detection unit 107 that detects the reception level based on the output from the AGC circuit 103 is attached, and based on the output of the reception level detection unit 107, the reception level (the electric field strength of the radio wave) at the antenna 101 at the current time point is added. ) Can be recognized.
FIG. 3 is a characteristic diagram showing the relationship between the input level to C / N and the C / N (static characteristics when the vehicle is stopped) in the in-vehicle digital television receiver of FIGS. 1 and 2. This characteristic is based on ISB-T (Integrated Services Digital Broadcasting-Terrestrial Transmission) which is a modulation method in terrestrial broadcasting in Japan. As shown in the figure, in the region where the input level is a certain value or more, the C / N maintains a certain level or more while gradually decreasing as the input level gradually decreases. If it falls below, C / N tends to decrease rapidly.

FIG. 4 is a characteristic diagram showing the relationship between the traveling speed of the vehicle and C / N (when the input level is −30 dB). As shown in the figure, it can be seen that when the vehicle starts traveling, the C / N ratio is already greatly reduced at the beginning.
FIG. 5 is a characteristic diagram showing the relationship between the traveling speed of the vehicle and C / N (when the input level is −60 dB). As shown in the figure, even if the input level is different from the case in FIG. 5, when the vehicle starts running, the C / N is already greatly reduced at the beginning, and the same tendency as in FIG. 5 is exhibited. I understand.

4 and 5 are simulation results using standard test signals under a certain multipath.
3, 4, and 5, the tendency of the C / N change is that if the input level to the tuner unit 102 is equal to or higher than a certain value, the C / N maintains a level that is substantially constant or higher as its static characteristics. At the same time, when such an input is secured, it can be seen that the vehicle changes greatly with the start of traveling of the vehicle equipped with the in-vehicle digital television receiver.

  In the case shown in the figure, the vehicle tends to agree with the case where the input level to the tuner unit 102 departs from a certain value or more. However, depending on the stop position, the vehicle is initially blocked by the building and the input level. Is not sufficient, and after starting the movement, there may be a case where the vehicle goes out to a place where the input level can be obtained above a certain value. Even in the latter case, C / N There is no change in the point that changes.

  Therefore, in the present invention, it is recognized that a specific change correlated with the running of the vehicle on which the in-vehicle digital television receiver is mounted by monitoring the change state of the detection output of the C / N detection unit 124. For example, for each time interval of 1 second, the average value of the measured values in C / N real time is obtained, and the average value (absolute value) of both is compared for each adjacent time interval. As a result, when it is recognized that the width of change in both sections exceeds a certain value (for example, 2 dB), it does not depend on other measured values from outside or the position of parking brake operation (signal indicating it), etc. In addition, the vehicle is determined to be in a running state, and the acceptance of operations to the operation unit of the in-vehicle digital television receiver is restricted.

  FIG. 6 is a flowchart showing the operation of the system controller 160 in FIG. First, the C / N detection value detected by the C / N detection unit 124 is read (step S601), and then the average value of C / N in each interval is calculated for each time interval of 1 second, for example (step S601). Step S602). Further, regarding the calculated average value of C / N in each section, the absolute value of the difference value in each adjacent section, that is, the change width of the average value of C / N in both sections is a constant value (this value) In the example, it is determined whether or not 2 dB) is exceeded (step S603).

  In the drawing notation, | C / N (1) | represents an average value of relatively preceding time sections of the adjacent time sections, and | C / N (2) | The average value of the time section which follows relatively among time sections is represented. If it is determined in step S603 that the difference between the C / N average values in the adjacent time sections is less than 2 dB (S603: Yes), the operation on the operation unit 150 (FIG. 1) is not limited (key). The operation is set to an unrestricted state) and is controlled so as to accept a desired operation by the user. In this case, as a matter of course, the video processing unit 130 and the display device 140 that displays the video output therefrom function effectively.

  On the other hand, when it is determined in step S603 that the difference between the average values of C / N in the adjacent time sections is 2 dB or more (S603: No), the operation unit 150 (FIG. 1) is accepted for operation. A restriction command (SR) to be restricted is issued to restrict the acceptance of the operation from the user (driver) (to the key operation restricted state), and the driver (driver) does not accept the desired operation, and the driver Control so that your attention is not distracted. In this case, if the video processing unit 130 and the display 140 that displays the video output from the video processing unit 130 are also disabled, the video display is prohibited (see FIG. 1). The flow is abbreviated with a broken line), which is more thorough from the viewpoint of ensuring driving safety. When such a configuration is adopted, the display 140 has a configuration that does not display a video when receiving a restriction command (SR) from the system controller 160 as a control unit. Similarly, the video processing unit Of course, 130 is configured to stop supplying a signal for displaying an image to the display 140 when receiving a restriction command (SR) from the system controller 160 as a control unit.

  FIG. 7 is a flowchart showing the operation of the system controller 160 in the modification of the embodiment of FIG. In FIG. 7, steps S701 to S703 are the same as steps S601 to S603 in FIG. In the example of FIG. 7, when it is determined in step S703 corresponding to step S603 of FIG. 6 that the difference in the average value of C / N in the adjacent time section is less than 2 dB (S703: Yes). Next, it is determined whether or not the C / N value at that time exceeds a predetermined value (20 dB in this example) (step S704).

If it is determined in step S704 that the value of C / N is higher than the predetermined value, the operation on the operation unit 150 (FIG. 1) is not restricted (the key operation is not restricted), and the user can select a desired value. Control to a state that can accept the street operation. In this case, as a matter of course, the video processing unit 130 and the display device 140 that displays the video output therefrom function effectively.
On the other hand, when it is determined in step S703 that the difference between the C / N average values in the adjacent time sections is 2 dB or more (S703: No), and in step S704, the value of C / N is the predetermined value. When it is determined that it is less than (S704: No), a restriction command (SR) for restricting the acceptance of the operation is issued to the operation unit 150 (FIG. 1), and the operation from the user (driver) is accepted. The control is performed so that the driver (driver) does not accept the desired operation and the driver's attention is not distracted.

  In this case, if the video processing unit 130 and the display 140 that displays the video output from the video processing unit 130 are also disabled, the video display is prohibited (see FIG. 1). The flow is abbreviated with a broken line), and from the viewpoint of ensuring driving safety, it is the same as the embodiment of FIG. In the example of FIG. 7, in addition to the embodiment of FIG. 6, in order to determine whether or not to restrict the key operation depending on the value of C / N in step S <b> 704, more accurate control is performed. Can be broken.

In each of the above examples, it has been configured to discriminate whether or not the vehicle is in a running state based on C / N. However, such discrimination is not performed without hesitating supply of information from the outside. This can be done depending on the fading frequency or using the fading frequency as a guide. Such an embodiment will be described below.
FIG. 8 is a characteristic diagram showing how the input level (the level of the input signal supplied from the antenna 101 to the tuner unit 102) changes with respect to the position of the in-vehicle digital television receiver 100 in a fading environment. In FIG. 8, the horizontal axis represents the travel time of a vehicle or the like equipped with a digital television receiver (and therefore a value corresponding to the distance or position), and the vertical axis represents the input level.

  As shown in the figure, the input level fluctuates greatly depending on the moving position (location), but the horizontal width of the middle level part of this fluctuation valley (curve that protrudes downward) is the burst interval, The interval between the middle level portions of the inclined portions on the same side of the adjacent peaks of a plurality of convex curves that are convex toward each other is the fading frequency. The BER value is 0 (reception condition is good) at the peak of each chevron curve or in the vicinity thereof, and the lower part of each chevron curve is a degraded part of BER.

  FIG. 9 is a characteristic diagram showing a correlation between a fading frequency and an average value in a unit time interval of C / N. In FIG. 9A, the horizontal axis represents the elapsed time, and the vertical axis represents the average value in the unit time interval of C / N. In FIG. 9B, the horizontal axis represents the elapsed time on the same scale as FIG. 9A, and the vertical axis represents the fading frequency. As shown in the figure, the fading frequency takes a constant value at a low level when the vehicle is stopped.

  After that, the engine is started and accelerated, and increases approximately in proportion to this acceleration until a certain first steady speed is reached. The time during which the first steady speed is reached and the speed is maintained is constant (relatively high level), and when the vehicle is subsequently decelerated, the fading frequency also decreases according to the deceleration. The time that the speed is maintained after reaching the steady speed is constant (at a relatively low level), decreases as the vehicle is decelerated again, and reaches a steady state at a lower level after stopping. The tendency is shown.

  In another embodiment of the present invention, focusing on the tendency as shown in FIG. 9, the discrimination of the running state at a steady speed, which may cause an erroneous determination in discrimination based on only C / N, is performed without error. I am doing so. That is, in an environment where there is little fading in traveling at a steady speed, it is determined that the vehicle is traveling if the fading frequency is equal to or higher than a certain value, and operation acceptance to the operation unit of the in-vehicle digital television receiver is restricted. I am doing so.

FIG. 10 is a flowchart showing the operation of the system controller in another embodiment. In this embodiment as well, the configuration on the block diagram is the same as that in FIG. 1, and therefore, when referring to the block diagram together, it is expressed using the reference numerals in FIG.
In FIG. 10, first, the BER value detected by the BER detection unit 106 is read (step S1001). Next, a fading frequency is calculated based on the BER value read in step S1001 (step S1002). Note that the calculation of the fading frequency referred to here is more strictly the calculation of the estimated value of the fading frequency. It is determined whether or not the fading frequency calculated in step S1002 is 1 Hz or more (step S1003). As a result, when it is determined that the fading frequency is less than 1 Hz (step S1003: No), the next step S1004 is performed. Migrate to Subsequent to step S1004, substantially the same processing as that of the above-described embodiment of FIG. 6 is executed.

  That is, in step S1004, the C / N detection value detected by the C / N detection unit 124 is read (step S1004). Next, for example, for each time interval of 1 second, the average value of C / N in each section is calculated (step S1005), and the calculated average value of C / N in each section is calculated for each adjacent section. It is determined whether or not the absolute value of the difference value at, that is, the range of change of the average value of C / N in both sections exceeds a certain value (2 dB in this example) (step S1006).

  In addition, | C / N (1) | in the notation of the figure represents an average value of relatively preceding time intervals among the adjacent time intervals, and | C / N (2) | The point representing the average value of relatively subsequent time intervals in the time interval is the same as in the case of FIG. If it is determined in step S1006 that the difference between the average values of C / N in the adjacent time sections is less than 2 dB (S1006: Yes), the operation on the operation unit 150 (FIG. 1) is not limited (key The operation is set to an unrestricted state) and is controlled so as to accept a desired operation by the user. In this case, as a matter of course, the video processing unit 130 and the display device 140 that displays the video output therefrom function effectively.

  On the other hand, when it is determined in step S1003 that the fading frequency exceeds 1 Hz (step S1003: Yes), and in step S1006, there is a difference in C / N average value of the adjacent time interval of 2 dB or more. (S1006: No) in any case, a restriction command (SR) for restricting the acceptance of the operation is issued to the operation unit 150 (FIG. 1), and an operation from the user (driver) is performed. Is limited (key operation restricted state), and control is performed so that the driver's attention is not distracted. In this case, if the video processing unit 130 and the display 140 that displays the video output from the video processing unit 130 are also inactivated, and the video is also prohibited from being displayed, from the viewpoint of ensuring driving safety. It will be more thorough.

  When such a configuration is adopted, the display 140 has a configuration that does not display a video when receiving a restriction command (SR) from the system controller 160 as a control unit. Similarly, the video processing unit FIG. 6 shows that 130 has a configuration for stopping the supply of a signal for displaying an image to display 140 when receiving a restriction command (SR) from system controller 160 as a control unit. This is exactly the same as described above.

In the embodiment of FIG. 10 as a modification, after determining in step S1006 whether or not the difference between the average values of C / N in the adjacent time sections is equal to or greater than a predetermined value (2 dB), FIG. As in the example of FIG. 7, it may be further determined whether or not the C / N value at that time is equal to or greater than a predetermined value (20 dB).
As described above, as is understood from the description of each embodiment, the control unit, which is a key component of the present invention, is based on the data generated in the process in the OFDM demodulation processing unit 120. It is considered that a restriction command SR for recognizing a change in a state quantity having a specific correlation with a moving state of a vehicle on which the John receiver 100 is mounted and issuing a restriction command SR for restricting acceptance of an operation to the operation unit 150 based on the recognition. it can.

It is a block diagram showing the structure of the vehicle-mounted digital television receiver as embodiment of this invention. FIG. 2 is a block diagram illustrating a configuration of the in-vehicle digital television receiver of FIG. 1 viewed from a viewpoint of a process for obtaining a transport stream (TS) from radio waves detected by an antenna. FIG. 3 is a characteristic diagram illustrating a relationship between input level to C / N (static characteristics when the vehicle is stopped) in the tuner unit in the in-vehicle digital television receiver of FIGS. 1 and 2. It is a characteristic view showing the relationship (when an input level is -30 dB) of the traveling speed of a vehicle versus C / N. It is a characteristic view showing the relationship (when an input level is -60 dB) of traveling speed versus C / N of a vehicle. It is a flowchart showing operation | movement of the system controller in FIG. It is a flowchart showing operation | movement of the system controller in the modification of embodiment of FIG. It is a characteristic view showing the mode of change of the input level (the level of the input signal supplied from the antenna to the tuner unit) with respect to the position of the in-vehicle digital television receiver in a fading environment. It is a characteristic view showing the correlation with a fading frequency and the average value in the unit time section of C / N. It is a flowchart showing operation | movement of the system controller in other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Car-mounted digital television receiver 101 ... Antenna 102 ... Tuner part 103 ... AGC circuit 104 ... Viterbi decoding error correction circuit 105 ... Reed-Solomon (RS) decoding error correction circuit 106 ... BER detection part 107 ... Reception level detection part 120 ... OFDM demodulation processing unit 121 ... OFDM demodulation unit 122 ... Reception level detection unit 123 ... BER detection unit 124 ... C / N detection unit 130 ... Video processing unit 140 ... Display device 150 ... Operation unit 160 ... System controller

Claims (7)

  Based on the tuner that performs channel selection processing related to the received signal supplied from the antenna, the OFDM demodulation processing unit that receives and outputs the output of the tuner unit, and the output of the OFDM demodulation processing unit An in-vehicle digital television receiver having a video processing unit that forms and outputs a signal suitable for display, a display that displays video based on the output of the video processing unit, and an operation unit that accepts an operation by a user A C / N detection unit for detecting C / N (carrier power to noise power ratio) from the OFDM demodulation processing unit, and monitoring the change status of the detection output of the C / N detection unit Restriction that restricts the acceptance of operations to the operation unit when it is recognized that a specific change correlated with the running of a vehicle equipped with a digital television receiver Automotive digital television receiver characterized by comprising a control unit that emits decree.   The in-vehicle digital television receiver according to claim 1, wherein the display is configured to receive a restriction command from the control unit, and does not display the video when receiving the restriction command. Machine.   The video processing unit is configured to receive a restriction command from the control unit, and when receiving the restriction command, stops supplying a signal for displaying a video to the display unit. The in-vehicle digital television receiver according to claim 1.   Based on the tuner that performs channel selection processing related to the received signal supplied from the antenna, the OFDM demodulation processing unit that receives and outputs the output of the tuner unit, and the output of the OFDM demodulation processing unit An in-vehicle digital television receiver having a video processing unit that forms and outputs a signal suitable for display, a display that displays video based on the output of the video processing unit, and an operation unit that accepts an operation by a user A BER detection unit for detecting BER from the OFDM demodulation processing unit, a C / N detection unit for detecting C / N (carrier power to noise power ratio) from the OFDM demodulation processing unit, and the BER detection A fading frequency is estimated based on the detected output of the unit, and when the estimated fading frequency exceeds a predetermined value, and the estimated fading When it is recognized that a specific change situation having a correlation with the traveling of the vehicle equipped with the in-vehicle digital television receiver appears in the detection output of the C / N detection unit without the frequency exceeding a predetermined value, A vehicle-mounted digital television receiver comprising: a control unit that issues a restriction command that restricts the acceptance of operations to the operation unit at any time.   5. The on-vehicle digital television receiver according to claim 4, wherein the display unit is configured to receive a restriction command from the control unit, and does not display the video when receiving the restriction command. Machine.   The video processing unit is configured to receive a restriction command from the control unit, and when receiving the restriction command, stops supplying a signal for displaying a video to the display unit. The in-vehicle digital television receiver according to claim 4.   Based on the tuner that performs channel selection processing related to the received signal supplied from the antenna, the OFDM demodulation processing unit that receives and outputs the output of the tuner unit, and the output of the OFDM demodulation processing unit An in-vehicle digital television receiver having a video processing unit that forms and outputs a signal suitable for display, a display that displays video based on the output of the video processing unit, and an operation unit that accepts an operation by a user Recognizing a change in a state quantity having a specific correlation with a movement state of a vehicle equipped with the in-vehicle digital television receiver based on data generated in the process in the OFDM demodulation processing unit, A vehicle-mounted digital apparatus comprising: a control unit that issues a restriction command for restricting acceptance of an operation to the operation unit based on the recognition. Television receiver.

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