JP2014138230A - Broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcast receiver in which generation of block noise due to decrease in transmission efficiency of data can be suppressed, even when the signal level of a broadcast signal decreases.SOLUTION: A BD recorder (broadcast receiver) 10 includes a tuner 12 for receiving a broadcast signal containing broadcast data and error correction information, a demodulation circuit 13 for demodulating a broadcast signal received by the tuner 12, and a control unit 16 for, in accordance with the signal level of the broadcast signal received by the tuner 12, adjusting the ratio of broadcast data in the broadcast signal outputted from the tuner 12 to the demodulation circuit 13, and adjusting the width of guard interval being added to the broadcast signal in order to suppress interference of the broadcast signal.

Description

  The present invention relates to a broadcast receiving apparatus, and more particularly, to a broadcast receiving apparatus provided with a control unit that adjusts the proportion of broadcast data in a broadcast signal in accordance with the signal level of the broadcast signal.

  2. Description of the Related Art Conventionally, there has been known a broadcast receiving device including a control unit that adjusts the ratio of broadcast data in a broadcast signal according to the signal level of the broadcast signal (see, for example, Patent Document 1).

  In Patent Document 1, a converter (demodulation unit) that demodulates a convolutionally encoded signal (a signal including received data and error correction information) received from an artificial satellite via an antenna, and output from the converter A satellite communication device including a soft-decision Viterbi decoding circuit that decodes a received signal and a control processing unit is disclosed. The control processing unit of this satellite communication device improves the transmission efficiency of received data according to the error correction occurrence rate at the time of decoding the received signal from the artificial satellite and the power level (signal level) of the received signal. In addition, the coding rate of the signal output from the converter to the soft-decision Viterbi decoding circuit (the ratio of received data in the convolutionally coded received signal) is adjusted. In this satellite communication device, a guard interval when signals are transmitted from the converter to the soft-decision Viterbi decoding circuit (in order to suppress interference between signals when a plurality of signals are continuously transmitted). The width of the redundant portion added to the signal is considered to be kept constant.

JP 2004-356665 A

  However, in Patent Document 1, it is considered that the width of the guard interval when the signal is transmitted from the converter to the soft-decision Viterbi decoding circuit is kept constant, so that the signal level of the received signal is reduced. Even if the coding rate of the signal output from the converter to the soft decision Viterbi decoding circuit is adjusted so that the transmission efficiency of the received data is improved, the guard interval width is set larger than necessary. Is considered to have the disadvantage that the amount of data contained in a signal transmitted per predetermined time is reduced. In this case, block noise (when the received signal is displayed as an image, a partial area (block) of the image due to a decrease in data transmission efficiency when the signal level of the received signal decreases. It is considered that there is a problem that noise that causes a phenomenon that is displayed in a mosaic pattern is likely to occur.

  The present invention has been made in order to solve the above-described problems, and one object of the present invention is to provide a block resulting from a decrease in data transmission efficiency even when the signal level of a broadcast signal is decreased. It is an object of the present invention to provide a broadcast receiving apparatus capable of suppressing the occurrence of noise.

  In order to achieve the above object, a broadcast receiving apparatus according to one aspect of the present invention includes a receiving unit that receives a broadcast signal including broadcast data and error correction information, and a demodulation that demodulates the broadcast signal received by the receiving unit. And adjusting the ratio of broadcast data in the broadcast signal output from the receiver to the demodulator according to the signal level of the broadcast signal received by the receiver and the receiver, and suppressing the interference of the broadcast signal And a control unit that adjusts the width of the guard interval added to the broadcast signal.

  In the broadcast receiving device according to one aspect of the present invention, when the signal level of the broadcast signal is lowered by the configuration as described above, if the width of the guard interval is larger than necessary, the width of the guard interval is increased. Since it can be adjusted to be small, it is possible to suppress a decrease in the data amount of the broadcast signal transmitted per predetermined time. As a result, even when the signal level of the broadcast signal is lowered, it is possible to suppress a decrease in data transmission efficiency, and thus it is possible to suppress occurrence of block noise due to a decrease in data transmission efficiency. Can do.

  In the broadcast receiving apparatus according to the above aspect, the control unit is preferably configured to change the width of the guard interval so that a decrease in the signal level of the broadcast signal is suppressed. If comprised in this way, even if the width | variety of a guard interval is changed, since the fall of the signal level of a broadcast signal is suppressed, suppressing the fall of the signal level of the broadcast signal resulting from the change of the width | variety of a guard interval It is possible to suppress a decrease in the data amount of the broadcast signal transmitted per predetermined time.

  In this case, preferably, the control unit suppresses a decrease in the reception level of the broadcast signal based on guard interval information that is measured in advance and relates to a change in the signal level of the broadcast signal when the width of the guard interval changes. Thus, the width of the guard interval is changed. If comprised in this way, based on the guard interval information regarding the change in the signal level of the broadcast signal when the width of the guard interval changes, the width of the guard interval that can easily suppress the decrease in the reception level of the broadcast signal is easily set. You can choose.

  In the broadcast receiving apparatus including a control unit that changes the width of the guard interval based on the guard interval information, preferably, the broadcast receiving device further includes a storage unit that stores the guard interval information, and the control unit is configured for a channel that receives the broadcast signal. When scanning is performed, guard interval information is measured, and the measured guard interval information is stored in a storage unit. With this configuration, since guard interval information is acquired in advance and stored in the storage unit when scanning a channel that receives a broadcast signal, the guard interval stored in the storage unit is changed when the width of the guard interval is changed. By referring to the information, it is possible to quickly select the width of the guard interval in which a decrease in the reception level of the broadcast signal is suppressed.

  In the broadcast receiving apparatus according to the above aspect, the control unit preferably receives the broadcast signal according to a carrier-to-noise ratio (CN ratio) of the broadcast signal, an error correction occurrence rate for the broadcast signal, or a reception level of the broadcast signal. The ratio of the broadcast data in the broadcast signal output from the unit to the demodulator is adjusted in stages, and the width of the guard interval added to the broadcast signal is adjusted. With this configuration, unlike the case of continuously changing the ratio of broadcast data in the broadcast signal output from the receiver to the demodulator, the control burden of the controller when adjusting the ratio of broadcast data Can be reduced.

  According to the present invention, as described above, even when the signal level of a broadcast signal is reduced, it is possible to suppress the occurrence of block noise due to a reduction in data transmission efficiency.

It is the block diagram which showed the whole structure of the BD recorder by 1st Embodiment of this invention. FIG. 2 is an image diagram showing a broadcast signal output from a tuner shown in FIG. 1 to a demodulation circuit. It is the flowchart which showed the processing flow performed when guard interval information is acquired by the control part of the BD recorder by 1st Embodiment of this invention. It is the flowchart which showed the processing flow performed when a code rate and a guard ratio are adjusted by the control part of the BD recorder by 1st Embodiment of this invention. It is the flowchart which showed the processing flow performed when a code rate and a guard ratio are adjusted by the control part of the BD recorder by 2nd Embodiment of this invention.

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

(First embodiment)
First, the configuration of a BD (Blu-Ray (registered trademark) Disc) recorder 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The BD recorder 10 is an example of the “broadcast receiving device” in the present invention. The BD recorder 10 can output video / audio data recorded on a disc-type recording medium (optical disc) such as a DVD (Digital Versatile Disc) or BD to an external device (for example, the display device 20), and from the external device. A recording / reproducing apparatus configured to record input video / audio data on an optical disc.

  As shown in FIG. 1, the BD recorder 10 includes a disk drive 11, a tuner 12, a demodulation circuit 13, a decoder 14, an output I / F (interface) 15, a control unit 16, and a memory 17. . The tuner 12, the demodulation circuit 13, and the memory 17 are examples of the “reception unit”, “demodulation unit”, and “storage unit” of the present invention, respectively.

  The disk drive 11 is provided to drive an optical disk such as a DVD or a BD. The tuner 12 is connected to an antenna 30 and is configured to receive a broadcast signal (for example, a terrestrial digital television broadcast signal) via the antenna 30. The tuner 12 is configured to output the received broadcast signal to the demodulation circuit 13.

  Here, as shown in FIG. 2, the broadcast signal output from the tuner 12 to the demodulation circuit 13 is converted into a convolutional code, and includes broadcast data, error correction information, and a guard interval. Note that the error correction information is a redundant part added to the broadcast signal in order to suppress the occurrence of an error when the convolutionally encoded broadcast signal is demodulated. The guard interval is a redundant portion added to the broadcast signal in order to suppress interference between the broadcast signals when a plurality of broadcast signals are continuously transmitted. Further, L1, L2, and L3 in FIG. 2 are broadcast data, error correction information, and data length (width) of the guard interval, respectively.

  As shown in FIG. 1, the demodulation circuit 13 is configured to demodulate the broadcast signal output from the tuner 12 and output it to the decoder 14. The decoder 14 is configured to decode (decode) the broadcast signal demodulated by the demodulation circuit 13 and output it to the output I / F 15. The output I / F 15 is connected to the display device 20 and is configured to output broadcast data of the broadcast signal received from the decoder 14 to the display device 20.

  The control unit 16 is provided to control each unit of the BD recorder 10. The memory 17 is provided to store various programs executed by the control unit 16 and various data such as guard interval information 17a described later.

  Here, in the first embodiment, the control unit 16 adjusts the ratio of broadcast data in the broadcast signal output from the tuner 12 to the demodulation circuit 13 according to the signal level of the broadcast signal received by the tuner 12. In addition, control is performed to adjust the width of the guard interval added to the broadcast signal in order to suppress interference of the broadcast signal. Specifically, the control unit 16 is configured to perform control to adjust the coding rate and guard ratio of the broadcast signal in accordance with the CN ratio (carrier-to-noise ratio) of the broadcast signal received by the tuner 12. ing. The coding rate is the ratio of broadcast data to convolutionally encoded broadcast data and error correction information, and is a numerical value represented by L1 / (L1 + L2) in FIG. Further, the guard ratio is a ratio of the guard interval to a portion including effective information (portion including broadcast data and error correction information) in the broadcast signal, and is a numerical value represented by L3 / (L1 + L2) in FIG. It is.

  The control unit 16 is configured to select from a plurality of preset coding rates and guard ratios when adjusting the coding rate and the guard ratio as described above. For example, in the case of a Japanese terrestrial digital television broadcast signal, 1/2, 2/3, 3/4, 5/6, and 7/8 can be selected as coding rates, and the guard ratio can be selected. 1/4, 1/8, 1/16 and 1/32 are selectable.

  Further, the control unit 16 is configured to monitor whether or not the CN ratio of the broadcast signal is equal to or greater than a predetermined reference value, and to reduce the encoding rate of the broadcast signal stepwise according to the monitoring result. Yes. For example, the control unit 16 is configured to set the coding rate from an initial value (7/8) to a value one step smaller (5/6) when the CN ratio is 8.5 or less. Further, the control unit 16 is configured to set the coding rate from 5/6 to 3/4, which is smaller by one step, when the CN ratio is lower than 8. Further, the control unit 16 is configured to set the coding rate from 3/4 to 2/3, which is smaller by one step, when the CN ratio falls below 7.5. Further, the control unit 16 is configured to set the coding rate from 2/3 to 1/2, which is one step lower, when the CN ratio is less than 7.

  Further, when the coding rate is set to a value one step smaller (5/6) from the initial value (7/8) as described above, the control unit 16 sets the guard ratio of the broadcast signal to the CN ratio. It is configured to change to an optimum value at which the decrease can be most suppressed. Specifically, first, the control unit 16 changes the guard ratio of the broadcast signal in the channel scan (scanning of a channel capable of receiving a television broadcast) performed by the tuner 12 when the BD recorder 10 is initially set. By changing to the above, it is configured to measure how much the CN ratio deteriorates when the guard ratio of the broadcast signal is variously changed. And the control part 16 memorize | stores the information measured in this way (information regarding the change of CN ratio of a broadcast signal when the guard ratio of a broadcast signal is changed variously) in the memory 17 as guard interval information 17a. It is configured. Based on the guard interval information 17a stored in the memory 17, the control unit 16 guards the deterioration of the CN ratio due to the change in the guard ratio and suppresses the width of the guard interval to the smallest. It is configured to change the ratio.

  Next, a processing flow executed when the guard interval information 17a is acquired by the control unit 16 of the BD recorder 10 according to the first embodiment of the present invention will be described with reference to FIG. This processing flow is started when the BD recorder 10 is initially set.

  In this processing flow, first, as shown in FIG. 3, in step S1, a process of performing scanning (channel scanning) of a channel capable of receiving a television broadcast is executed via the tuner 12. Then, the process proceeds to step S2.

  Next, in step S2, a process for obtaining guard interval information 17a is executed. Here, the guard interval information 17a is information relating to a change in the CN ratio (carrier-to-noise ratio) of the broadcast signal when the guard interval of the broadcast signal changes. That is, in this step S2, it is measured how much the CN ratio deteriorates when the guard ratio of the broadcast signal is variously changed, and the measurement result is acquired as the guard interval information 17a. Then, the process proceeds to step S3.

  Next, in step S3, a process of storing the guard interval information 17a acquired in step S2 in the memory 17 is executed. Then, the process ends.

  The guard interval information 17a is acquired as described above.

  Next, a processing flow executed when the coding rate and the guard ratio are adjusted by the control unit 16 of the BD recorder 10 according to the first embodiment of the present invention will be described with reference to FIG.

  In this processing flow, first, as shown in FIG. 4, in step S11, the coding rate of the broadcast signal output from the tuner 12 to the demodulation circuit 13 (numerical value indicated by L1 / (L1 + L2) in FIG. 2) and Processing for setting the guard ratio (a numerical value represented by L3 / (L1 + L2) in FIG. 2) to an initial value is performed. Specifically, processing for setting the coding rate to 7/8 and setting the guard ratio to 1/8 is performed. Then, the process proceeds to step S12.

  Next, in step S12, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 8.5 or less is executed. The process of step S12 is repeatedly executed until it is determined that the CN ratio is 8.5 or less. And when it is judged that CN ratio is 8.5 or less, it progresses to Step S13.

  Next, in step S13, a process of reducing the encoding rate of the broadcast signal by one step from the initial value set in step S11 is executed. Specifically, processing for setting the coding rate from 7/8 to 5/6 is executed. Then, the process proceeds to step S14.

  Next, in step S14, based on the guard interval information 17a stored in the memory 17 by the process of step S3 in FIG. 3, a process for setting the guard ratio of the broadcast signal to an optimum guard ratio is executed. Here, the optimal guard ratio is a guard ratio in which the deterioration of the CN ratio due to the change in the guard ratio is most suppressed and the width of the guard interval is the smallest. Then, the process proceeds to step S15.

  Next, in step S15, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 8 or less is executed. If it is determined in step S15 that the CN ratio exceeds 8, the process returns to step S12. On the other hand, if it is determined in step S15 that the CN ratio is 8 or less, the process proceeds to step S16.

  Next, in step S16, a process of reducing the encoding rate of the broadcast signal by one step from the value set in step S13 is executed. Specifically, processing for setting the coding rate from 5/6 to 3/4 is executed. Then, the process proceeds to step S17.

  Next, in step S17, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 7.5 or less is executed. If it is determined in step S17 that the CN ratio exceeds 7.5, the process returns to step S12. On the other hand, if it is determined in step S17 that the CN ratio is 7.5 or less, the process proceeds to step S18.

  Next, in step S18, processing for reducing the encoding rate of the broadcast signal by one step from the value set in step S16 is executed. Specifically, processing for setting the coding rate from 3/4 to 2/3 is executed. Then, the process proceeds to step S19.

  Next, in step S19, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 7 or less is executed. If it is determined in step S19 that the CN ratio exceeds 7, the process returns to step S12. On the other hand, if it is determined in step S19 that the CN ratio is 7 or less, the process proceeds to step S20.

  Next, in step S20, processing for reducing the encoding rate of the broadcast signal by one step from the value set in step S18 is executed. Specifically, processing for setting the coding rate from 2/3 to 1/2 is executed. Then, the process returns to step S12.

  As described above, the coding rate and guard ratio of the broadcast signal are adjusted.

  In the first embodiment, as described above, the control unit 16 causes the broadcast data to be included in the broadcast signal output from the tuner 12 to the demodulation circuit 13 according to the CN ratio of the broadcast signal received by the tuner 12. While adjusting (coding rate), in order to suppress the interference of a broadcast signal, it is comprised so that the width | variety (guard ratio) of the guard interval added to a broadcast signal may be adjusted. As a result, when the CN ratio of the broadcast signal decreases, when the guard interval width is larger than necessary, the guard interval width can be adjusted to be small, so that transmission is performed per predetermined time. It can suppress that the data amount of a broadcast signal reduces. As a result, even when the CN ratio of the broadcast signal is reduced, it is possible to prevent the data transmission efficiency from being reduced. Therefore, block noise (broadcast signal is transmitted to the display device 20 due to the reduction in data transmission efficiency). It is possible to suppress the occurrence of noise that causes a phenomenon in which a partial area (block) of an image is displayed in a mosaic shape when displayed as an image.

  In the first embodiment, as described above, the control unit 16 is configured to change the width of the guard interval (guard ratio) so that the decrease in the CN ratio of the broadcast signal is most suppressed. Thereby, even if the width of the guard interval is changed, the decrease in the CN ratio of the broadcast signal is suppressed. Therefore, while the decrease in the CN ratio of the broadcast signal due to the change in the width of the guard interval is suppressed, It is possible to suppress a decrease in the data amount of the broadcast signal transmitted to the network.

  Moreover, in 1st Embodiment, as mentioned above, the control part 16 is based on the guard interval information 17a regarding the change of CN ratio of the broadcast signal when the width | variety of the guard interval changed previously measured. The width of the guard interval is changed so that the decrease in the reception level is most suppressed. Thereby, based on the guard interval information 17a regarding the change in the CN ratio of the broadcast signal when the width of the guard interval changes, the width of the guard interval (guard ratio) that can most easily suppress the decrease in the reception level of the broadcast signal. ) Can be selected.

  In the first embodiment, as described above, the control unit 16 measures the guard interval information 17a when scanning a channel that receives a broadcast signal, and stores the measured guard interval information 17a in the memory 17. Is configured to be stored in As a result, since the guard interval information 17a is stored in the memory 17 in advance when scanning a channel that receives a broadcast signal, the guard interval information 17a stored in the memory 17 is referred to when the width of the guard interval is changed. Thus, it is possible to quickly select a guard interval width (guard ratio) in which a decrease in the reception level of the broadcast signal is most suppressed.

  In the first embodiment, as described above, the control unit 16 controls the ratio of broadcast data (coding rate) in the broadcast signal output from the tuner 12 to the demodulation circuit 13 according to the CN ratio of the broadcast signal. ) In steps, and the width of the guard interval (guard ratio) added to the broadcast signal is adjusted. This reduces the control burden on the control unit 16 when adjusting the ratio of broadcast data, unlike the case where the ratio of broadcast data in the broadcast signal output from the tuner 12 to the demodulation circuit 13 is continuously changed. can do.

(Second Embodiment)
Next, the configuration of a BD (Blu-Ray Disc) recorder 10a according to the second embodiment of the present invention will be described with reference to FIG. 1 and FIG. In the second embodiment, unlike the first embodiment in which the guard interval information 17a is acquired only during channel scanning, an example in which the guard interval information 17a is acquired every time the encoding rate of the broadcast signal is adjusted will be described. To do. The BD recorder 10a is an example of the “broadcast receiving device” in the present invention.

  Also in the second embodiment, as in the first embodiment, the control unit 16a (see FIG. 1) of the BD recorder 10a demodulates from the tuner 12 according to the CN ratio of the broadcast signal received by the tuner 12. Control is performed to adjust the coding rate and guard ratio of the broadcast signal output to the circuit 13. Further, the control unit 16a is configured to monitor whether or not the CN ratio of the broadcast signal is equal to or higher than a predetermined reference value, and to reduce the encoding rate of the broadcast signal stepwise according to the monitoring result. Yes.

  Here, in the second embodiment, the control unit 16a guards a change in the CN ratio when the guard ratio of the broadcast signal is variously changed every time the coding rate is adjusted according to the CN ratio of the broadcast signal. The interval information 17a is acquired, and the guard ratio of the broadcast signal is optimized based on the acquired guard interval information 17a (deterioration of the CN ratio due to the change of the guard ratio is most suppressed, and the width of the guard interval The guard ratio is adjusted so as to be minimized).

  In addition, the other structure of 2nd Embodiment is the same as that of the said 1st Embodiment.

  Next, with reference to FIG. 5, the processing flow executed when the coding rate and the guard ratio are adjusted by the control unit 16a of the BD recorder 10a according to the second embodiment of the present invention will be described.

  In this processing flow, first, as shown in FIG. 5, in step S21, the encoding rate and guard ratio of the broadcast signal output from the tuner 12 to the demodulation circuit 13 are set to initial values (7/8 and 1/8, respectively). ) Is set. Then, the process proceeds to step S22.

  Next, in step S22, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 8.5 or less is executed. The process of step S22 is repeatedly executed until it is determined that the CN ratio is 8.5 or less. If it is determined that the CN ratio is 8.5 or less, the process proceeds to step S23.

  Next, in step S23, processing for reducing the encoding rate of the broadcast signal by one step from the initial value set in step S21 is executed. Specifically, processing for setting the coding rate from 7/8 to 5/6 is executed. Then, the process proceeds to step S24.

  Next, in step S24, it is measured how much the CN ratio deteriorates when the guard ratio of the broadcast signal is variously changed, and a process of acquiring the measurement result as guard interval information 17a is executed. Then, the process proceeds to step S25.

  Next, in step S25, a process of setting the guard ratio of the broadcast signal to an optimum guard ratio is executed based on the guard interval information 17a acquired by the process of step S24. Here, the optimal guard ratio is a guard ratio in which the deterioration of the CN ratio due to the change in the guard ratio is most suppressed and the width of the guard interval is the smallest. Then, the process proceeds to step S26.

  Next, in step S26, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 8 or less is executed. If it is determined in step S26 that the CN ratio exceeds 8, the process returns to step S22. On the other hand, if it is determined in step S26 that the CN ratio is 8 or less, the process proceeds to step S27.

  Next, in step S27, processing for reducing the encoding rate of the broadcast signal by one step from the value set in step S23 is executed. Specifically, processing for setting the coding rate from 5/6 to 3/4 is executed. Then, the process proceeds to step S28.

  Next, in step S28, the process of acquiring the guard interval information 17a (the same process as in step S24) is executed again, and the process proceeds to step S29. In step S29, a process for setting the guard ratio of the broadcast signal to an optimum guard ratio based on the guard interval information 17a acquired by the process in step S28 (the same process as in step S25) is executed. . Then, the process proceeds to step S30.

  Next, in step S30, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 7.5 or less is executed. If it is determined in step S30 that the CN ratio exceeds 7.5, the process returns to step S22. On the other hand, if it is determined in step S30 that the CN ratio is 7.5 or less, the process proceeds to step S31.

  Next, in step S31, processing for reducing the encoding rate of the broadcast signal by one step from the value set in step S27 is executed. Specifically, processing for setting the coding rate from 3/4 to 2/3 is executed. Then, the process proceeds to step S32.

  Next, in step S32, the process of acquiring the guard interval information 17a (the same process as in steps S24 and S28) is executed again, and the process proceeds to step S33. In step S33, a process of setting the guard ratio of the broadcast signal to an optimum guard ratio based on the guard interval information 17a acquired in the process of step S32 (the same process as in steps S25 and S29) is executed. Is done. Then, the process proceeds to step S34.

  Next, in step S34, processing for determining whether or not the CN ratio of the broadcast signal demodulated by the demodulation circuit 13 is 7 or less is executed. If it is determined in step S34 that the CN ratio exceeds 7, the process returns to step S22. On the other hand, if it is determined in step S34 that the CN ratio is 7 or less, the process proceeds to step S35.

  Next, in step S35, processing for reducing the encoding rate of the broadcast signal by one step from the value set in step S31 is executed. Specifically, processing for setting the coding rate from 2/3 to 1/2 is executed. Then, the process proceeds to step S36.

  Next, in step S36, the process for obtaining the guard interval information 17a (the same process as in steps S24, S28, and S32) is executed again, and the process proceeds to step S37. In step S37, a process for setting the guard ratio of the broadcast signal to an optimum guard ratio based on the guard interval information 17a acquired by the process in step S36 (the same process as in steps S25, S29, and S33). Is executed. Then, the process returns to step S22.

  In the second embodiment, as described above, the control unit 16a changes the CN ratio when the guard ratio of the broadcast signal is variously changed every time the coding rate is adjusted according to the CN ratio of the broadcast signal. The guard interval information 17a is acquired, and the guard ratio of the broadcast signal is optimized based on the acquired guard interval information 17a (the deterioration of the CN ratio due to the change of the guard ratio is most suppressed, The guard ratio is adjusted so as to be the smallest). Thereby, since the latest guard interval information 17a is acquired every time the coding rate is adjusted according to the CN ratio of the broadcast signal, the guard ratio of the broadcast signal is appropriately set based on the latest guard interval information 17a. Can be adjusted. This second embodiment is the latest guard interval information corresponding to the change in the reception environment when the reception environment changes with the movement of the broadcast reception apparatus, such as a portable BD recorder (broadcast reception apparatus). This is effective in that the guard ratio of the broadcast signal can be appropriately adjusted using 17a.

  The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first and second embodiments, the example in which the BD recorder is used as the broadcast receiving apparatus of the present invention has been shown, but the present invention is not limited to this. The present invention can be applied to other broadcast receiving apparatuses (for example, a television apparatus and a set top box (STB)) other than the BD recorder as long as the receiving apparatus includes a receiving unit that receives a broadcast signal. is there.

  Moreover, although the example which adjusts the encoding rate and guard ratio of a broadcast signal according to CN ratio of a broadcast signal was shown in the said 1st and 2nd embodiment, this invention is not limited to this. In the present invention, the coding rate and the guard ratio of the broadcast signal may be adjusted according to a signal level other than the CN ratio of the broadcast signal. For example, the encoding rate and guard ratio of the broadcast signal may be adjusted according to the error correction occurrence rate (BER: bit error rate) for the broadcast signal, or broadcast according to the reception level (reception strength) of the broadcast signal. The signal coding rate and the guard ratio may be adjusted.

  Moreover, although the example which adjusts the encoding rate of a broadcast signal in steps according to CN ratio was shown in the said 1st and 2nd embodiment, this invention is not limited to this. In the present invention, the coding rate of the broadcast signal may be continuously adjusted according to the CN ratio.

  In the second embodiment, every time the encoding rate of the broadcast signal decreases stepwise, the guard ratio of the broadcast signal is set to an optimum value (deterioration of the CN ratio due to the change of the guard ratio is most suppressed, In addition, an example in which the guard ratio is adjusted so that the width of the guard interval becomes the smallest is shown, but the present invention is not limited to this. In the present invention, the guard ratio of the broadcast signal may be decreased stepwise each time the encoding rate of the broadcast signal decreases stepwise.

10, 10a BD recorder (broadcast receiving device)
12 Tuner (receiver)
13 Demodulator circuit (demodulator)
16, 16a Control unit 17 Memory (storage unit)
17a Guard interval information

Claims (5)

A receiving unit for receiving a broadcast signal including broadcast data and error correction information;
A demodulator that demodulates the broadcast signal received by the receiver;
According to the signal level of the broadcast signal received by the receiver, the ratio of the broadcast data in the broadcast signal output from the receiver to the demodulator is adjusted, and interference of the broadcast signal is reduced. A broadcast receiving apparatus, comprising: a control unit that adjusts a width of a guard interval added to the broadcast signal for suppression.   The broadcast receiving apparatus according to claim 1, wherein the control unit is configured to change a width of the guard interval so that a decrease in signal level of the broadcast signal is suppressed.   The control unit is configured to suppress a decrease in the reception level of the broadcast signal based on guard interval information that is measured in advance and is related to a change in the signal level of the broadcast signal when the width of the guard interval changes. The broadcast receiving apparatus according to claim 2, wherein the broadcast receiving apparatus is configured to change a width of the guard interval. A storage unit for storing the guard interval information;
The control unit is configured to measure the guard interval information and store the measured guard interval information in the storage unit when scanning of a channel that receives the broadcast signal is performed. Item 4. The broadcast receiving device according to Item 3.   The control unit is configured to output the broadcast signal output from the reception unit to the demodulation unit in accordance with a carrier-to-noise ratio of the broadcast signal, an error correction occurrence rate with respect to the broadcast signal, or a reception level of the broadcast signal. 5. The structure according to claim 1, wherein the ratio of the broadcast data is adjusted stepwise and the width of the guard interval added to the broadcast signal is adjusted. Broadcast receiving device.

Images