JP2008011019A - Television broadcast receiver and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a television broadcast receiver and a television broadcast receiving method capable of reducing a sense of incongruity and a sense of displeasure caused when a terrestrial digital TV broadcast is switched into a terrestrial analog TV broadcast. <P>SOLUTION: The television broadcast receiver includes: a selective output means for selectively outputting a received signal of either form of the digital television broadcast or the analog television broadcast; and a filtering processing means for applying prescribed filtering processing to an audio signal included in the broadcast signal when the digital television broadcast signal is selected by the selective output means to bring its frequency response characteristic closer to the frequency response characteristic of an audio signal of the analog television broadcast. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a TV broadcast receiver and a TV broadcast receiving method for receiving simultaneous digital television (hereinafter, “TV” is referred to as “TV”) broadcast and analog TV broadcast.

  In recent years, it has become common to process / manage audio and video in a digital format in a recording medium, equipment, or the like. The trend of digital encoding of audio and video in such recording media and devices has spread to the broadcasting related industry. In the broadcasting-related industry, the transition from terrestrial analog TV broadcasting to terrestrial digital TV broadcasting is currently in progress.

  This terrestrial digital TV broadcast is spreading. However, in order to shift TV broadcasting from terrestrial analog TV broadcasting to terrestrial digital TV broadcasting, large-scale capital investment, enormous time, labor, cost, etc. are required. Currently, the transition is gradually in progress, and there are situations where nationwide terrestrial digital TV broadcasting is available / not available. In addition, in order to view digital terrestrial TV broadcasting, a device corresponding to it is necessary. Viewers must purchase new equipment in order to view terrestrial digital TV broadcasts. Therefore, if the TV broadcast is integrated into the terrestrial digital TV broadcast at this stage, many viewers cannot view the TV broadcast. In view of these circumstances, simultaneous broadcasting of terrestrial digital TV broadcasting and terrestrial analog TV broadcasting (that is, a method of broadcasting a program having the same content at the same time in both digital and analog formats) is being implemented. .

For example, in a TV broadcast receiver mounted on a moving body represented by a vehicle, terrestrial digital TV broadcasts and terrestrial analog TV broadcasts are considered in consideration of scattered areas where terrestrial digital TV broadcasts are viewable / unavailable It is designed to receive both broadcasts. For example, Patent Literature 1 below discloses a TV broadcast receiver that supports simultaneous broadcasting. The TV broadcast receiver described in Patent Document 1 below monitors whether or not an error rate of a reception signal (hereinafter referred to as “digital reception signal”) of a terrestrial digital TV broadcast exceeds a reference value. When the error rate is equal to or lower than the reference value, it is determined that the reception state of the terrestrial digital TV broadcast is good, and the digital reception signal is output to the video / audio output device. On the other hand, when the error rate exceeds the reference value, it is assumed that the reception state of the terrestrial digital TV broadcast has deteriorated. ). That is, according to Patent Document 1 below, a TV broadcast receiver that outputs a digital reception signal preferentially and outputs an analog reception signal only when the reception state of the terrestrial digital TV broadcast deteriorates is provided.
Japanese Patent No. 3583963

  When the error rate continues to fluctuate across the reference value in the TV broadcast receiver described in Patent Document 1, the reception signal output to the video / audio output device is either a digital reception signal or an analog reception signal. It is assumed that it switches frequently.

  Here, the bandwidth of the audio signal differs between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast. Specifically, the bandwidth of terrestrial digital TV broadcasting exceeds 20 kHz, whereas the bandwidth of terrestrial analog TV broadcasting is less than 15 kHz. That is, terrestrial digital TV broadcasting has a wider dynamic range than terrestrial analog TV broadcasting, and can reproduce high-frequency audio components. Therefore, the viewer can perceive that the sound is wider than the terrestrial analog TV broadcast when viewing the terrestrial digital TV broadcast.

  For example, high frequency audio components are relatively weak in news programs. This means that the audio signal of a news program does not contain much high frequency audio components that can be attenuated by terrestrial analog TV broadcasting. For this reason, it is difficult for a difference in sound reproduced between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast. Therefore, when viewing such a program, it is considered that the viewer does not feel much the difference in sound between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast (difference in sound spread and volume).

  On the other hand, for example, a high frequency sound component may appear strongly in a music program. This means that audio signals such as music programs contain many high frequency audio components that can be attenuated by terrestrial analog TV broadcasting. For this reason, the sound of digital terrestrial TV broadcasting includes a lot of high frequency sound that cannot be reproduced by terrestrial analog TV broadcasting. Therefore, when viewing such a program, it is considered that the viewer can clearly feel the difference in sound between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast.

  When the audio output to the video / audio output device is frequently switched to either terrestrial digital TV broadcast or terrestrial analog TV broadcast, the viewer may suddenly lose the program's sound range due to the difference in sound in each broadcast. Sometimes it feels like it has spread, or the sound of the program suddenly becomes muffled. If such a change in sound quality occurs frequently in a short period of time, the viewer may feel uncomfortable or uncomfortable.

  Therefore, in view of the above circumstances, the present invention provides a TV broadcast receiver and a TV that can reduce discomfort and discomfort that a viewer can remember when terrestrial digital TV broadcasting and terrestrial analog TV broadcasting are switched. It is an object to provide a broadcast receiving method.

  A TV broadcast receiver according to an aspect of the present invention that solves the above-described problems relates to a receiver that receives simultaneous digital TV broadcast and analog TV broadcast. The TV broadcast receiver includes a selective output means for selectively outputting the received digital TV broadcast or analog TV broadcast signal to a playback device, and a digital TV broadcast signal by the selective output means. And a filtering processing means for applying a predetermined filtering process to the audio signal included in the signal to bring the frequency response characteristic close to the frequency response characteristic of the audio signal of the analog TV broadcast. Is.

  According to the TV broadcast receiver configured as described above, the frequency response characteristic of the audio signal of the digital TV broadcast is brought close to the frequency response characteristic of the audio signal of the analog TV broadcast. Thereby, even if the format to be reproduced is switched, the change in sound quality is reduced, so that discomfort and discomfort that can be given to the viewer can be reduced.

  In the TV broadcast receiver, the filtering processing means may convert the frequency response characteristic of the audio signal of the digital TV broadcast so that the attenuation rate increases as the frequency component increases.

  The TV broadcast receiver may further include, for example, reception state determination means for determining the reception state of digital TV broadcast. In this case, the selective output means outputs a digital TV broadcast signal to the playback device when it is determined that the reception state of the digital TV broadcast is good, and analog when it is determined that the reception state is not good. It operates to output a TV broadcast signal to the playback device.

  In addition, a TV broadcast receiver according to another aspect of the present invention that solves the above-described problems relates to a receiver that receives simultaneous digital TV broadcast and analog TV broadcast. This TV broadcast receiver is a reception state determination means for determining a reception state of a digital TV broadcast, and a selection for selectively outputting a received signal of either digital TV broadcast or analog TV broadcast to a playback device. Output means for determining whether the signal in the format output from the selective output means is either a signal according to the determination result of the reception state determination means or a signal that does not depend on the determination result. When a digital TV broadcast signal is selected by the selective output means and is determined according to the determination result, the audio signal included in the signal is subjected to a predetermined filtering process and its frequency response characteristic is analogized. The frequency response characteristic of the audio signal of TV broadcast is approached, it is determined that it does not depend on the determination result, and the digital TV broadcast signal is determined by the selective output means. When it is-option is that characterized by not subjected to the filtering processing on the audio signal contained in the signal.

  Here, for example, the TV broadcast receiver may be a mobile body.

  A TV broadcast receiving method according to an aspect of the present invention that solves the above-described problem relates to a method for receiving a simulcast digital TV broadcast and an analog TV broadcast. This TV broadcast receiving method includes a selective output step of selectively outputting a received signal of either digital TV broadcast or analog TV broadcast to a playback device, and a digital TV broadcast signal by the selective output step. A filtering process step of applying a predetermined filtering process to the audio signal included in the signal to bring the frequency response characteristic close to the frequency response characteristic of the audio signal of the analog TV broadcast.

  According to such a TV broadcast receiving method, the frequency response characteristic of an audio signal of a digital TV broadcast is brought close to the frequency response characteristic of an audio signal of an analog TV broadcast. Thereby, even if the reproduction | regeneration format switches, since the change of sound quality is reduced, the discomfort and discomfort which can be given to a viewer can be reduced.

  In the filtering processing step, the frequency response characteristic of the audio signal of the digital TV broadcast may be converted so that the attenuation rate increases as the frequency component increases.

  The TV broadcast receiving method may further include, for example, a reception state determination step for determining a reception state of a digital TV broadcast. In this case, in the selective output step, when it is determined that the reception state of the digital TV broadcast is good, a signal of the digital TV broadcast is output to the playback device, and when it is determined that the reception state is not good, the analog TV broadcast signal is output. Broadcast signals can be output to the playback device.

  In addition, a TV broadcast receiving method according to another aspect of the present invention that solves the above-described problems relates to a method for receiving simultaneous digital TV broadcast and analog TV broadcast. This TV broadcast reception method includes a reception state determination step for determining a reception state of a digital TV broadcast, and a selection to selectively output a received signal of either digital TV broadcast or analog TV broadcast to a playback device. An output determination step for determining whether the signal in the format output in the selective output step is one according to the determination result in the reception state determination step or one not depending on the determination result; When a digital TV broadcast signal is selected in the selective output step as determined according to the determination result, a predetermined filtering process is performed on the audio signal included in the signal, and the frequency response characteristic is converted to analog TV broadcast. And a selective output step that is determined to be close to the frequency response characteristics of the audio signal or to be independent of the determination result When the signal of the digital TV broadcast is selected, the method comprising the selective filtering process steps to the audio signal included in the signal not subjected to the filtering process.

  According to the TV broadcast receiver and the TV broadcast reception method of the present invention, the terrestrial digital signal is filtered by performing the filtering process so that the frequency response characteristic of the audio signal of the digital TV broadcast approaches the frequency response characteristic of the audio signal of the analog TV broadcast. It is possible to reduce discomfort and discomfort that a viewer can remember when switching between TV broadcasting and terrestrial analog TV broadcasting.

  Hereinafter, the configuration and operation of the TV broadcast receiver according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a video / audio output device 100 including a TV broadcast receiver according to an embodiment of the present invention. The video / audio output device 100 is mounted on, for example, a vehicle that is a moving body. The video / audio output device 100 is compatible with simultaneous broadcasting, and is designed to receive and process both terrestrial digital TV broadcasts and terrestrial analog TV broadcasts.

  The video / audio output device 100 includes a control unit 10, a digital TV antenna 11, a digital TV tuner 12, an OFDM (Orthogonal Frequency Division Multiplexing) demodulator 13, an MPEG (Moving Picture Experts Group) decoder 14, a video. Driver 15, D terminal connection unit 16, audio D / A converter 21, de-emphasis filter 22, audio selector switch 23, audio amplifier 24, analog TV antenna 31, analog TV tuner 32, digital video format A conversion unit 33, a sound multiplex demodulation unit 34, a memory 40, a display 50, speakers 60R and 60L, and a light receiving unit 70 are provided.

  The remote controller (hereinafter referred to as “remote controller”) 80 is provided with operation keys for operating the video / audio output device 100. When the user operates the remote controller 80, a control pulse corresponding to the operation is output from the remote controller 80. This control pulse is, for example, a signal conforming to the IrDA standard. When the light receiving unit 70 receives this control pulse, it passes it to the control unit 10. When the remote controller 80 is being operated, for example, the display on the display 50 may be switched to the operation screen, or character information relating to the operation may be superimposed on the image being displayed on the display 50. .

  The control unit 10 performs overall control of the entire video / audio output apparatus 100. The control unit 10 operates to control each component based on, for example, various programs installed therein and control pulses from the light receiving unit 70.

  Here, a series of signal processing in the video / audio output apparatus 100 will be described.

  First, signal processing of a digital reception signal will be described. The digital TV antenna 11 has a function of receiving an RF (Radio Frequency) signal of each channel of terrestrial digital TV broadcasting. Each RF signal received by the digital TV antenna 11 is input to the digital TV tuner 12.

  The digital TV tuner 12 performs frequency conversion by selecting an RF signal of a channel designated by the control unit 10 (hereinafter referred to as “designated channel”) from among the input RF signals. Specifically, the signal is converted into an intermediate frequency (IF) signal that improves stable operation and selection characteristics. The IF signal after frequency conversion is input to the OFDM demodulator 13 after unnecessary frequency components are removed by a BPF (Band Pass Filter) (not shown).

  The channel selected by the digital TV tuner 12 is determined according to the channel selection by the user operation. Specifically, when the user operates the remote controller 80 to select a channel, a control pulse corresponding to the operation is output from the remote controller 80. When the light receiving unit 70 receives this control pulse and passes it to the control unit 10, the control unit 10 issues a command to the digital TV tuner 12 to select the RF signal of the designated channel. The digital TV tuner 12 executes tuning processing according to this command.

  The control unit 10 issues a command to the digital TV tuner 12 and writes the information of the designated channel in the memory 40. Therefore, the memory 40 always holds information on the channel selected last by the user (hereinafter referred to as “last channel”). When the channel selection operation by the user is not performed (for example, immediately after the power is turned on), the control unit 10 refers to the memory 40 and issues a command to the digital TV tuner 12 to select the RF signal corresponding to the last channel. .

  The OFDM demodulator 13 performs A / D conversion on the input IF signal to convert it into a digital signal. Next, the converted digital signal is divided into, for example, several thousand carriers, and after being subjected to synthesis (for example, a known maximum ratio synthesis) by matching the phase for each carrier, demodulation is performed. Thereby, an MPEG-2 transport stream signal (hereinafter referred to as “TS signal”) is obtained. This TS signal is output to the MPEG decoder 14. The OFDM demodulator 13 passes a BER (Bit Error Rate) indicating the quality of the digital received signal to the controller 10.

  The MPEG decoder 14 is provided with two input ports. One input port (hereinafter referred to as “first MPEG port”) is connected to the OFDM demodulator 13. The other input port (hereinafter referred to as “second MPEG port”) is connected to the digital video format conversion unit 33. The MPEG decoder 14 executes processing on a signal input to one of the input ports in accordance with an instruction from the control unit 10. Here, it is assumed that the MPEG decoder 14 has received an instruction to apply processing to the TS signal input to the first MPEG port. In this case, the MPEG decoder 14 decodes the TS signal input to the first MPEG port. As a result, the TS signal is decoded into a digital TV broadcast video signal and a digital format audio signal. This video signal is composed of, for example, a luminance signal (Y) and color difference signals (Pb, Pr). The decoded video signal is output to the video driver 15. The audio signal is output to the audio D / A converter 21.

  The video signal of the digital TV broadcast is amplified and output by the video driver 15 and transmitted through a cable having an impedance of 75Ω. The video signal output from the video driver 15 is input to the display 50 via the D terminal connection unit 16. Thereby, a terrestrial digital TV broadcast program is displayed on the screen of the display 50.

  The audio D / A converter 21 D / A converts the audio signal from the MPEG decoder 14 and outputs it to the audio switch 23. The audio D / A converter 21 has a de-emphasis filter 22 built therein. The function of the de-emphasis filter 22 is turned on / off according to a command from the control unit 10. When the function of the de-emphasis filter 22 is on, the D / A converted audio signal is subjected to a predetermined filtering process and output to the audio changeover switch 23. When the function of the de-emphasis filter 22 is turned off, the D / A converted audio signal is output to the audio selector switch 23 without being subjected to the filtering process. This filtering process will be described in detail later.

  The voice selector switch 23 has two input ports. One input port is connected to the audio D / A converter 21. The other input port is connected to the sound multiplex demodulator 34. The voice changeover switch 23 performs a switching operation according to a command from the control unit 10 and outputs a voice signal input to one of the input ports to the audio amplifier 24. Here, it is assumed that the audio selector switch 23 is switching-controlled so as to connect the audio D / A converter 21 and the audio amplifier 24.

  The audio amplifier 24 amplifies the audio signal from the audio switch 23 and outputs it to the speakers 60R and 60L. Thereby, the sound of the terrestrial digital TV broadcast program is reproduced by the speakers 60R and 60L.

  Next, signal processing of the analog reception signal will be described. The analog TV antenna 31 has a function of receiving an RF signal of each channel of terrestrial analog TV broadcasting. Each RF signal received by the analog TV antenna 31 is input to the analog TV tuner 32.

  Here, a channel map is stored in the memory 40. This channel map is a frequency map corresponding to simulcast, and shows the correspondence between terrestrial digital TV broadcast channels and terrestrial analog TV broadcast channels that broadcast the same program at the same time as that channel. It is data.

  When the controller 10 issues a command to the digital TV tuner 12 to select the designated channel or the last channel, the controller 10 issues a similar command to the analog TV tuner 32. More specifically, the control unit 10 reads the channel map of the memory 40 and acquires channel information of the terrestrial analog TV broadcast corresponding to the designated channel or the last channel. A command is issued to the analog TV tuner 32 to select the acquired channel of the terrestrial analog TV broadcast.

  The analog TV tuner 32 selects the RF signal of the channel designated by the control unit 10 from the input RF signals and converts it to an IF signal. Next, the IF signal after frequency conversion is separated into a video signal and an audio signal. The analog TV tuner 32 demodulates the separated video signal into a composite video signal and outputs the composite video signal to the digital video format conversion unit 33. Also, the separated audio signal is demodulated into a multiplexed audio signal and output to the audio multiplex demodulator 34.

  The digital video format conversion unit 33 converts an analog composite video signal into a digital video format signal (a signal composed of a luminance signal (Y) and color difference signals (Cb, Cr)) and outputs the signal to the MPEG decoder 14.

  Here, it is assumed that the MPEG decoder 14 has received a command from the control unit 10 to perform processing on the digital video format signal input to the second MPEG port. In this case, the MPEG decoder 14 decodes the digital video format signal input to the second MPEG port. Thus, the digital video format signal is decoded into an analog TV broadcast video signal (a signal composed of a luminance signal (Y) and color difference signals (Pb, Pr)). The decoded video signal is output to the video driver 15.

  The video signal of the analog TV broadcast is amplified and output by the video driver 15 and transmitted through a cable having an impedance of 75Ω. Then, the data is input to the display 50 through the D terminal connection unit 16. Thereby, a terrestrial analog TV broadcast program is displayed on the screen of the display 50.

  The audio multiplex demodulator 34 demodulates the audio signal from the analog TV tuner 32 and outputs it to the audio switch 23. Here, it is assumed that the audio selector switch 23 is switching-controlled so as to connect the audio multiplex demodulator 34 and the audio amplifier 24. Therefore, the audio signal from the audio multiplex demodulator 34 is delivered to the audio amplifier 24 via the audio changeover switch 23. When this audio signal is amplified by the audio amplifier 24 and output to the speakers 60R and 60L, the audio of the terrestrial analog TV broadcast program is reproduced by the speakers 60R and 60L.

  Here, in the audio / video output apparatus 100, the hybrid function can be turned on / off by a user operation using the remote controller 80. According to the reception state of the terrestrial digital TV broadcast, this hybrid function converts the video signal to be output to the display 50 (and the audio signal to be output to the speakers 60R and 60L) to the terrestrial digital TV broadcast or terrestrial analog TV broadcast. This is a function for switching to either one.

  When the hybrid function is turned on and the reception state of the terrestrial digital TV broadcast is good, a program based on the terrestrial digital TV broadcast is output from the display 50 and each speaker. When the reception state of the terrestrial digital TV broadcast deteriorates, a program based on the terrestrial analog TV broadcast is reproduced on the display 50 and each speaker.

  On the other hand, when the hybrid function is turned off, an image based on terrestrial digital TV broadcast (or terrestrial analog TV broadcast) is displayed on the display 50 regardless of the reception state of the terrestrial digital TV broadcast, and the sound is output from the speaker 60R and Played at 60L.

  When the control unit 10 receives a hybrid function setting control pulse from the light receiving unit 70, the control unit 10 writes in the memory 40 that the function is set to ON or OFF. Accordingly, the memory 40 always holds the latest information (hereinafter referred to as “last function setting”) indicating whether the user has set the function to ON or OFF.

  Next, TV broadcast program playback processing in the video / audio output apparatus 100 of this embodiment will be described. FIG. 2 shows a flowchart of TV broadcast program playback processing in the video / audio output apparatus 100.

  The process of the flowchart in FIG. 2 starts when, for example, a power supply (not shown) of the video / audio output apparatus 100 is turned on, and ends when the power supply is turned off. This process is executed at every predetermined timing.

  When the power of the video / audio output device 100 is turned on, the control unit 10 controls the digital TV tuner 12 and the analog TV tuner 32 based on the last channel and the channel map stored in the memory 40, for example. Next, it is determined whether or not the hybrid function is turned on with reference to the last function setting stored in the memory 40 (step 1, hereinafter, step is abbreviated as “S” in the specification and drawings).

  When it is determined that the hybrid function is off (S1: NO), the control unit 10 should play back the program in either terrestrial digital TV broadcast or terrestrial analog TV broadcast using the display 50 and each speaker. It is determined whether or not (S2). In which format the program should be reproduced can be arbitrarily set by a user operation, for example.

  When it is determined in step S2 that a terrestrial digital TV broadcast program should be reproduced (S2: digital), the control unit 10 controls the de-emphasis filter 22 to turn off its filtering function (S3). Further, the audio switch 23 is controlled to connect the audio D / A converter 21 and the audio amplifier 24 (S4).

  Following the process of S4, the control unit 10 executes a process on the digital received signal (S5). Specifically, the control unit 10 controls the digital TV tuner 12, the OFDM demodulation unit 13, the MPEG decoder 14, and the like to execute the above-described series of signal processing. Next, a series of signal-processed video signals are reproduced on the display 50 via the video driver 15 and the D terminal connection unit 16. A series of signal processed audio signals is input to the audio D / A converter 21. Here, since the filtering function of the de-emphasis filter 22 is turned off, the audio signal is D / A converted and output to the audio changeover switch 23 without being subjected to filtering processing. Since the audio selector switch 23 connects the audio D / A converter 21 and the audio amplifier 24 in the process of S4, the audio signal from the audio D / A converter 21 is input to the audio amplifier 24. Next, through the amplification process in the audio amplifier 24, the sound of the terrestrial digital TV broadcast program is reproduced by the speakers 60R and 60L. The control unit 10 returns to the process of S1 after a predetermined timing.

  When it is determined in step S2 that a terrestrial analog TV broadcast program should be reproduced (S2: analog), the control unit 10 controls the audio changeover switch 23 to connect the audio multiplex demodulation unit 34 and the audio amplifier 24. (S6).

  Following the process of S6, the control unit 10 executes a process for the analog received signal (S7). Specifically, the control unit 10 controls the analog TV tuner 32 to obtain a composite video signal. Next, the digital video format conversion unit 33, the MPEG decoder 14 and the like are controlled to execute the above-described series of signal processing. Finally, the signal-processed video signal is reproduced on the display 50 via the video driver 15 and the D terminal connection unit 16. The control unit 10 controls the analog TV tuner 32 and the audio multiplex demodulation unit 34 to perform signal processing. Next, the signal-processed audio signal is input to the audio switch 23. Since the audio switch 23 connects the audio multiplex demodulator 34 and the audio amplifier 24 in the process of S 6, the audio signal from the audio multiplex demodulator 34 is input to the audio amplifier 24. Next, through the amplification process in the audio amplifier 24, the sound of the terrestrial analog TV broadcast program is reproduced by the speakers 60R and 60L. The control unit 10 returns to the process of S1 after a predetermined timing.

  Further, when it is determined in the process of S1 that the hybrid function is turned on (S1: YES), the control unit 10 determines whether or not the BER delivered from the OFDM demodulation unit 13 is higher than a predetermined threshold ( S8). The predetermined threshold here corresponds to, for example, a BER at a reception limit (a state in which the reception intensity of terrestrial digital TV broadcasting is reduced and sound and video of the broadcast cannot be normally output).

  When it is determined in the process of S8 that the BER is higher than the predetermined threshold (S8: YES), the control unit 10 has a bad reception status of the terrestrial digital TV broadcast, and the terrestrial digital TV broadcast program is displayed on the display 50. It is determined that it cannot be displayed, and the process proceeds to S6. That is, the program reproduced on the display 50 and each speaker is switched from terrestrial digital TV broadcast to terrestrial analog TV broadcast.

  When it is determined in the process of S8 that the BER is equal to or less than the predetermined threshold (S8: NO), the control unit 10 determines that the reception state of the terrestrial digital TV broadcast is good and proceeds to the process of S9. The timing at which the OFDM demodulator 13 delivers the BER to the controller 10 may be regular, or may be when the process of S8 is executed.

  In the process of S9, the control unit 10 controls the de-emphasis filter 22 to turn on its filtering function. Next, the processes of S4 and S5 are executed to reproduce the terrestrial digital TV broadcast program on the display 50 and each speaker, and the process returns to S1 after a predetermined timing.

  That is, according to the processing of the flowchart of FIG. 2, when the hybrid function is turned off, the program is played back in either terrestrial digital TV broadcast or terrestrial analog TV broadcast depending on the user's arbitrary setting. When the hybrid function is turned on, if the reception state of the terrestrial digital TV broadcast is good, the program is reproduced in this format. On the other hand, if the reception state of the terrestrial digital TV broadcast is deteriorated, the program is reproduced in the form of the terrestrial analog TV broadcast.

Here, FIG. 3 shows frequency response characteristics of each type of sound. Curve D ₁ of the FIG. 3 is a frequency response characteristic of the audio digital terrestrial TV broadcasting at the time of the hybrid function off. Curve D ₂ is a frequency response characteristic of the audio digital terrestrial TV broadcasting in the ON state hybrid function. Curve A is the frequency response characteristic of the sound of terrestrial analog TV broadcasting. The vertical axis in FIG. 3 indicates the level of audio output at the speakers 60R and 60L. The horizontal axis indicates the frequency. Here, it is assumed that the viewer's ear cannot hear the sound whose output level is less than about −20 dB. In this case, the bandwidth _{W A} terrestrial analog TV broadcast becomes 15kHz approximately as shown in Figure 3. On the other hand the band width _{W D} of the terrestrial digital TV broadcast is greater than 20kHz.

  When the hybrid function is on, the program played on the display 50 and each speaker is converted into either a terrestrial digital TV broadcast or a terrestrial analog TV broadcast depending on the reception state of the terrestrial digital TV broadcast as described above. Switch automatically. As shown in FIG. 3, there is no significant difference in frequency response characteristics between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast on the low frequency side among the audio components reproduced by the speakers 60R and 60L. However, on the high frequency side, the attenuation rate of terrestrial analog TV broadcasting is significantly higher than that of terrestrial digital TV broadcasting. In addition, as the frequency becomes higher, there is a marked difference in both frequency response characteristics.

  When the playback format is switched when the hybrid function is on, the bandwidth played back by the speakers 60R and 60L changes depending on the difference in frequency response characteristics. Therefore, each time the playback format is switched, the viewer may feel that the program's sound range has suddenly expanded or that the program's sound has suddenly become muffled. In the present embodiment, the frequency component on the high frequency side in terrestrial digital TV broadcasting is attenuated to reduce the difference between the frequency response characteristics of both formats when the hybrid function is on. Specifically, the control unit 10 turns on the filtering function of the de-emphasis filter 22 in the process of S9 shown in FIG.

When filtering the de-emphasis filter 22 is turned off, the frequency response characteristics of the terrestrial digital TV broadcasting is substantially constant over the entire band (see curve D _1). On the other hand, the frequency response characteristic of terrestrial analog TV broadcasting gradually attenuates as it becomes higher, and falls below −20 dB around 15 kHz (see curve A). That is, in this case, the difference in frequency response characteristics between the two formats is significant.

When the filtering function of the de-emphasis filter 22 is turned on, the audio signal of the terrestrial digital TV broadcast decoded by the MPEG decoder 14 is subjected to a filtering process so that it gradually attenuates as its frequency response characteristic becomes higher. that (see curve _{D 2).} That is, the frequency response characteristic of the terrestrial digital TV broadcast is brought close to the frequency response characteristic of the terrestrial analog TV broadcast by the filtering process. Therefore, in this case, the difference in frequency response characteristics between the terrestrial digital TV broadcast and the terrestrial analog TV broadcast is reduced. As a result, the viewer is less likely to feel that the program's sound range suddenly expands or the program's sound suddenly becomes muffled even when the playback format is switched. For example, even if the playback format is switched in a program containing a lot of high-frequency audio components (for example, a music program), the viewer is less likely to feel uncomfortable or uncomfortable with the audio, and the effect is remarkable. .

  In the present embodiment, as described above, the playback format switching process is not executed when the hybrid function is off. For example, when the playback function is set to terrestrial digital TV broadcasting when the hybrid function is off, the control unit 10 turns off the filtering function of the de-emphasis filter 22. As a result, the frequency response characteristics of terrestrial digital TV broadcasting are substantially constant over the entire band, and high-frequency audio components (for example, 15 kHz or more) included in the program are also reproduced by the speakers 60R and 60L. That is, the sound reproduced by the speakers 60R and 60L has a broadness (realism).

  That is, in the present embodiment, no filtering process is applied to the audio signal of the terrestrial digital TV broadcast in a situation in which a sense of discomfort or discomfort depending on the switching of the playback format cannot occur. Therefore, in this case, the viewer can enjoy the program while enjoying the original sound quality of terrestrial digital TV broadcasting.

  The above is the embodiment of the present invention. The present invention is not limited to these embodiments and can be modified in various ranges.

  The video / audio output apparatus including the TV broadcast receiver according to the present embodiment is mounted on a vehicle, but may be a device that is carried by a person in another embodiment.

  Further, as an alternative to the process of S2 in FIG. 2, the output format may be determined based on the BER as in the process of S8.

It is the block diagram which showed the structure of the video / audio output device which equipped with the TV broadcast receiver of embodiment of this invention. It is the flowchart which showed the TV broadcast program reproduction | regeneration processing in the video / audio output device of embodiment of this invention. The frequency response characteristics of each type of speech are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control part 11 Digital TV antenna 12 Digital TV tuner 13 OFDM demodulation part 14 MPEG decoder 15 Video driver 16 D terminal connection part 21 Audio D / A converter 22 De-emphasis filter 23 Audio changeover switch 24 Audio amplifier 31 Analog TV antenna 32 Analog TV tuner 33 Digital video format converter 34 Audio multiplex demodulator 40 Memory 50 Display 60R, 60L Speaker 70 Light receiver 80 Remote control 100 Video / audio output device

Claims (9)

In a television broadcast receiver that receives simultaneous digital television broadcasting and analog television broadcasting,
Selective output means for selectively outputting a received signal of either digital television broadcast or analog television broadcast to a playback device;
When a digital television broadcast signal is selected by the selective output means, the audio signal included in the signal is subjected to a predetermined filtering process, and the frequency response characteristic is changed to the frequency response characteristic of the analog television broadcast audio signal. A television broadcast receiver characterized by comprising filtering processing means for approaching.   2. The television broadcast reception according to claim 1, wherein the filtering processing means converts the frequency response characteristic of the audio signal of the digital television broadcast so that the attenuation rate becomes higher as the frequency component becomes higher. Machine. It further comprises reception state determination means for determining the reception state of the digital television broadcast,
The selective output means outputs a digital television broadcast signal to the playback device when it is determined that the reception state of the digital television broadcast is good, and when it is determined that the reception state of the digital television broadcast is not good, The television broadcast receiver according to claim 1, wherein a television broadcast signal is output to the playback device. In a television broadcast receiver that receives simultaneous digital television broadcasting and analog television broadcasting,
Receiving state determining means for determining a receiving state of digital television broadcast;
Selective output means for selectively outputting the received signal of either digital television broadcast or analog television broadcast to a playback device;
An output determining means for determining a signal in a format output from the selective output means according to a determination result of the reception state determination means or one not depending on the determination result;
When a digital television broadcast signal is selected by the selective output means as determined according to the determination result, the audio signal included in the signal is subjected to a predetermined filtering process and its frequency response characteristic is analogized. It approaches the frequency response characteristics of television broadcast audio signals,
A television set characterized in that when it is determined not to depend on the determination result and a digital television broadcast signal is selected by the selective output means, the filtering process is not performed on an audio signal included in the signal. John broadcast receiver.   The television broadcast receiver according to claim 1, wherein the television broadcast receiver is provided in a moving body. In a television broadcast receiving method for receiving simultaneous digital television broadcasting and analog television broadcasting,
A selective output step of selectively outputting a received signal of either digital television broadcast or analog television broadcast to a playback device;
When a digital television broadcast signal is selected in the selective output step, a predetermined filtering process is performed on the audio signal included in the signal, and the frequency response characteristic is changed to the frequency response characteristic of the analog television broadcast audio signal. A television broadcast receiving method comprising: a filtering process step to be approached.   7. The television broadcast reception according to claim 6, wherein in the filtering processing step, the frequency response characteristic of the audio signal of the digital television broadcast is converted so that the attenuation rate increases as the frequency component increases. Method. A reception state determination step of determining a reception state of the digital television broadcast;
In the selective output step, when it is determined that the reception state of the digital television broadcast is good, the digital television broadcast signal is output to the playback device, and when it is determined that the reception state is not good, the analog television broadcast 3. The television broadcast receiving method according to claim 1, wherein a John broadcast signal is output to the playback device. In a television broadcast receiving method for receiving simultaneous digital television broadcasting and analog television broadcasting,
A reception state determination step for determining a reception state of the digital television broadcast;
A selective output step of selectively outputting a received signal of either digital television broadcast or analog television broadcast to a playback device;
An output determination step for determining a signal in a format output in the selective output step, according to a determination result in the reception state determination step, or a signal that does not depend on the determination result;
When a digital television broadcast signal is selected in the selective output step as determined according to the determination result, a predetermined filtering process is performed on the audio signal included in the signal, and the frequency response characteristic is analogized. When it is determined that the frequency response characteristic of the audio signal of the television broadcast is approached or does not depend on the determination result and the digital television broadcast signal is selected in the selective output step, the audio included in the signal is included. And a selective filtering process step of not performing the filtering process on the signal.

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