JP2009130745A - Broadcast receiver, and broadcast receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent noise output during decoding of digital radio broadcasting, and reproduce the digital radio broadcasting immediately after completion of decoding. <P>SOLUTION: A broadcast receiver has a signal format detection means detecting a signal format of a broadcasting signal to be received, and a mute control means muting only an output of an analog broadcasting signal when the detected signal format is an all-digital format. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a broadcast receiver and a broadcast reception method, and more particularly to an IBOC broadcast receiver and a broadcast reception method for receiving an IBOC (In Band On Channel) radio broadcast.

  In recent years, it has become common to process and manage audio and video in digital format in audio equipment and video equipment. The trend of digital encoding of audio and video in such audio equipment has spread to the field of radio broadcasting. For example, in the United States, a digital radio broadcasting system called IBOC has been proposed by iBiquity and put into practical use.

  By the way, the conventional analog radio broadcast is broadcast by a carrier wave (hereinafter referred to as “analog carrier”) having a frequency distribution within a frequency band (hereinafter referred to as “channel”) assigned to each broadcasting station. Actually, in order to avoid interference between analog carriers of adjacent channels, only the central portion of the allocated frequency band is used for analog carrier transmission, and the other portions are not used.

  The IBOC system is a system that performs digital radio broadcasting using a frequency band assigned to conventional analog radio broadcasting. The IBOC system defines multiple signal formats, such as a hybrid format in which a digital radio broadcast signal is superimposed on an existing analog radio broadcast signal and an all-digital format consisting only of digital signals. It is designed so that it can gradually shift from broadcasting to multi-function, high-quality all-digital format broadcasting.

  In the IBOC system, a signal format called a hybrid format is used in a transition period from analog broadcasting to all-digital broadcasting. In the hybrid format, digital broadcast subcarriers are arranged in a frequency band (hereinafter referred to as “sideband”) that has not been used conventionally, adjacent to the center of the band in which analog carriers are arranged. That is, according to the IBOC hybrid format, the analog radio broadcast and the digital radio broadcast are transmitted simultaneously using the same channel by effectively utilizing the frequency band assigned to the existing analog radio broadcast.

  For example, Patent Document 1 discloses an HD (High Definition) radio configured to be able to receive such IBOC radio broadcasts. The HD radio described in Patent Document 1 reproduces a high-quality digital radio broadcast when the radio wave reception state is good, and is the same when the radio wave reception state deteriorates and it becomes difficult to decode the digital radio broadcast signal. It is configured to play an analog radio broadcast on the channel.

  By the way, when changing the channel selection, the HD radio first mutes the output of the broadcast signal for a certain period of time and tunes during the mute to determine which signal format the changed channel is broadcast. Detect. If the channel format after the change is a hybrid format, it takes time to decode the digital radio broadcast signal. Therefore, HD radio plays analog radio broadcast prior to digital radio broadcast along with unmute. When the decoding is complete, switch to digital radio broadcast playback.

However, when the changed channel selection is all-digital format broadcasting, since the subcarrier is arranged instead of the analog carrier wave at the center of the frequency band of the channel, the HD radio corresponds to the analog carrier wave. Even if a frequency-domain signal is demodulated, an effective analog broadcast signal cannot be obtained. In this case, when the mute is canceled after a certain period of time, noise (subcarrier as an analog carrier wave) is output from the speaker through the analog radio broadcast signal line until the decoding process is completed and the digital radio broadcast is reproduced. The electrical signal obtained as a result of processing is converted into speech as it is), which is disadvantageous. In order to avoid this problem, conventional HD radios further mute the broadcast signal output for a predetermined time (the time that is expected to be required for decoding) until the digital radio broadcast is played back. It is configured to prevent noise from being output from the broadcast signal line.
JP 2004-135219 A

  However, when the output of the broadcast signal is further muted for a predetermined time as described above, the following inconvenience may occur. In other words, if the radio wave reception is good and the decoding of the digital radio broadcast is completed earlier than expected (under the predetermined time), the HD radio will mute even though the digital radio broadcast can be played back. The digital radio broadcast cannot be played until is canceled. Also, if the radio wave reception is poor and it takes longer time than expected to decode the digital radio broadcast (exceeding the predetermined time), the mute is canceled before the decoding of the digital radio broadcast is completed. Accordingly, noise is output from the speaker through the analog radio broadcast signal line after the mute is released and until the decoding is completed and the digital radio broadcast is reproduced. In other words, HD radio cannot promptly provide digital radio broadcast sound to the user in the former case, and the user can hear an unpleasant noise sound in the latter case.

  The present invention has been made in view of the above circumstances, and its object is to prevent digital noise from being output during decoding of a digital radio broadcast, and promptly execute digital radio after the decoding is completed. It is an object of the present invention to provide a broadcast receiver and a broadcast receiving method that can reproduce a broadcast.

  A broadcast receiver according to an embodiment of the present invention that solves the above problems is suitable for receiving a broadcast signal transmitted in an IBOC signal format, and detects a signal format of the received broadcast signal. And a mute control means for muting only the output of the analog broadcast signal when the detected signal format is the all-digital format.

  According to the broadcast receiver configured as described above, when the detected signal format is the all-digital format, only the output of the analog broadcast signal is muted, so that the signal of the analog broadcast signal is completed before the decoding of the digital broadcast signal is completed. Noise is not output from the line, and a digital broadcast signal is output upon completion of the decoding.

  Here, the broadcast receiver may be configured to further include channel changing means for changing the reception channel. In this case, the mute control means mutes the output of all broadcast signals for a predetermined time when the reception channel is changed. The predetermined time here is, for example, the time required until the signal format of the broadcast signal is detected.

  The broadcast receiver may further include a decoding unit that decodes the digital broadcast signal. In this case, the predetermined time is longer than the time required for the detection processing by the signal format detection means and shorter than the time required for the decoding processing by the decoding means.

  Moreover, the broadcast receiver is attached to a moving body, for example.

  In addition, a broadcast receiving method according to an embodiment of the present invention that solves the above-described problem is a method suitable for receiving a broadcast signal transmitted in an IBOC format signal format. A signal format detecting step for detecting, and a mute control step for muting only the output of the analog broadcast signal when the detected signal format is an all-digital format.

  According to such a broadcast receiving method, when the detected signal format is an all-digital format, only the output of the analog broadcast signal is muted, and therefore noise from the signal line of the analog broadcast signal is completed before the decoding of the digital broadcast signal is completed. Is output, and a digital broadcast signal is output upon completion of the decoding.

  Here, the broadcast receiving method may further include a channel changing step of changing the receiving channel. In this case, in the mute control step, when the reception channel is changed, all broadcast signal outputs are muted for a predetermined time. The predetermined time is, for example, a time required until the detection step is completed.

  The broadcast receiving method may further include a decoding step of decoding the digital broadcast signal. In this case, for example, the predetermined time is longer than the time required for the detection processing in the signal format detection step, and shorter than the time required for the decoding processing in the decoding step.

  According to the broadcast receiver and the broadcast reception method according to the present invention, when the detected signal format is the all-digital format, only the output of the analog broadcast signal is muted. Thus, noise obtained as a result of processing the subcarrier of digital broadcast as an analog carrier is not output from the signal line, and a digital broadcast signal is output upon completion of the decoding.

  Hereinafter, an HD radio according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of HD radio 100 according to the embodiment of the present invention. The HD radio 100 is attached to, for example, a vehicle that is a moving body. The HD radio 100 is designed to be compatible with IBOC radio broadcasting, and is configured to receive and process broadcast signals in the signal format of the system.

  The HD radio 100 includes an antenna 1, a tuner 2, an IF (Intermediate Frequency) amplifier 6, a separator SEP, an IF filter 7, an A / D converter 8, a DSP (Digital Signal Processor) 9, an audio signal processing unit 10, and a D / A converter. 11, power amplifier 12, speaker 13, PLL (Phase Locked Loop) circuit 14, microcomputer 15, IDM (IBOC Digital Module) 16, light receiving unit 17, remote controller (hereinafter referred to as “remote controller”) 18, display control circuit 19 and a display 20.

  The remote controller 18 is provided with operation keys for operating the HD radio 100. When the user operates the remote controller 18, a control pulse corresponding to the operation is output from the remote controller 18. The control pulse output at this time is, for example, a signal conforming to the IrDA standard. When the light receiving unit 17 receives this control pulse output from the remote controller 18, it passes it to the microcomputer 15.

  The microcomputer 15 controls the overall HD radio 100. Various control programs are installed in the microcomputer 15, and the control programs are executed based on the control pulses received from the light receiving unit 17 to control each element in the HD radio 100.

  The HD radio 100 reproduces a radio broadcast as follows. That is, when the antenna 1 receives a radio wave and outputs it to the tuner 2, the tuner 2 extracts an RF (Radio Frequency) signal of the selected channel from the received radio wave by control via the PLL circuit 14 by the microcomputer 15. Thus, frequency conversion to an intermediate frequency suitable for signal processing such as filtering is performed. The IF signal obtained by the frequency conversion of the RF signal is then input to the IF amplifier 6.

  Note that the above channel selection channel is determined according to the channel selection operation by the user using the remote controller 18 or the like. Information on the channel selected last (hereinafter referred to as “last channel”) is stored in an internal memory of the microcomputer 15 or a flash ROM (not shown). Immediately after the HD radio 100 is powered on, the microcomputer 15 controls the tuner 2 so that the last channel stored in the internal memory or the like is tuned.

  The IF amplifier 6 amplifies the input IF signal and outputs it to the separator SEP. Note that the amplification factor of the IF amplifier 6 is adjusted by feedback control so that the output signal from the IF amplifier 6 has a set intensity regardless of the intensity of the input signal to the IF amplifier 6. The separator SEP separates the input IF signal into two signal components. One of the signal components to be separated is a signal component obtained by converting an analog carrier wave to an IF signal, and the other is a signal component obtained by converting a sideband subcarrier to an IF signal. is there. For convenience of explanation, the former signal component is referred to as an “analog IF signal”, and the latter signal component is referred to as a “digital IF signal”. The separator SEP outputs the analog IF signal to the IF filter 7 and the digital IF signal to the A / D converter 8.

  The above description is based on the premise that the channel selection channel is a channel in a hybrid format. Of course, when only analog radio broadcast (or digital radio broadcast) is broadcast on the selected channel, the digital IF signal (or analog IF signal) separated by the separator SEP does not contain a valid signal component and is just noise. Absent.

  The IF filter 7 filters the input analog IF signal to remove unnecessary frequency components, and outputs the analog IF signal to the A / D converter 8. The A / D converter 8 includes separate A / D conversion processing circuits for analog IF signals and digital IF signals. Then, the input analog IF signal and digital IF signal are A / D converted by the corresponding A / D conversion processing circuit and output to the DSP 9.

  The DSP 9 includes a detection circuit 9a, a noise canceller 9b, and a weak electric field processing circuit 9c. The analog IF signal input to the DSP 9 is output to the detection circuit 9a, and the digital IF signal is output to the IDM 16.

  The analog IF signal is demodulated into an audio signal by the detection circuit 9a, and then noise is removed by the noise canceller 9b. Then, the signal after noise removal is subjected to processing (mute, high cut, separation control, etc.) according to the reception state of the selected channel by the weak electric field processing circuit 9c and output to the audio signal processing unit 10 as an analog audio signal. Is done.

  The IDM 16 is a module designed exclusively for IBOC digital radio broadcast signal processing. The IDM 16 demodulates the digital IF signal input from the DSP 9, decodes the demodulated signal, performs predetermined error correction processing, and obtains the resulting data as program audio data and accompanying data (PSD ( Program Service Data), SIS (Station Information Service), etc. The separated program audio data, that is, the digital radio broadcast audio signal (hereinafter, “digital audio signal”) is output to the audio signal processing unit 10. The accompanying data is output to the microcomputer 15.

  Further, the IDM 16 acquires primary service mode information by demodulating the digital IF signal. The information of the primary service mode is information indicating whether the selected channel is broadcast in a hybrid format or an all-digital format. The IDM 16 outputs the acquired primary service mode information to the microcomputer 15 as status information indicating the status of the digital radio broadcast. The microcomputer 15 uses the input primary service mode information in a mute control process to be described later.

  The IDM 16 measures the quality of the received signal (digital radio broadcast) based on the CN ratio and SN ratio of the signal obtained by the demodulation process, the error bit rate of the data obtained by the decoding process, and the like, and based on the quality. Generate a blend signal. The generated blend signal is output to the audio signal processing unit 10.

  The audio signal processing unit 10 includes a blend circuit 10a and an audio processing circuit 10b. The blend circuit 10a performs blend processing on the analog audio signal from the DSP 9 and the digital audio signal from the IDM 16 based on the input blend signal.

  By the way, in hybrid format broadcasting, digital radio broadcasting is of higher quality than analog radio broadcasting. Therefore, when the quality level of the received signal is equal to or higher than the predetermined level, the blend circuit 10a attenuates the analog audio signal based on the blend signal so that substantially only the digital audio signal is output. In addition, when the quality level of the received signal is less than the predetermined level, or when the user is set to reproduce only the analog radio broadcast, substantially only the analog audio signal is output based on the blend signal. So that the digital audio signal is attenuated. Further, when the quality level of the received signal changes over a predetermined level, the blend circuit 10a performs correction in consideration of the delay amount, quality difference, etc. between the analog audio signal and the digital audio signal based on the blend signal. While mixing the signals, the audio signals to be output are switched so that the voices before and after the switching are smoothly connected. The audio signal output from the blend circuit 10a is input to the audio processing circuit 10b, subjected to predetermined processing by the audio processing circuit 10b, and then output to the D / A converter 11.

  The audio signal input to the D / A converter 11 is D / A converted and then input to the power amplifier 12. The audio signal input to the power amplifier 12 is amplified according to the user's volume operation and output from the speaker 13. Through the above signal processing, the radio broadcast of the selected channel is reproduced.

  Further, the microcomputer 15 interprets the accompanying data (data described by the ID3 tag) from the IDM 16 and outputs the interpretation result to the display control circuit 19. The display control circuit 19 performs a predetermined process on the input interpretation result and outputs the result to the display 20. Thereby, information corresponding to the accompanying data is displayed on the display 20.

  The microcomputer 15 starts executing the mute control process shown in FIG. 2 when a user operation for changing the channel selection channel is accepted or when the HD radio 100 is turned on. The following mute control process will be described on the assumption that the received signal is of high quality.

  According to FIG. 2, the microcomputer 15 first mutes the output of the audio signal processing unit 10 (that is, outputs of both digital and analog audio signals) (step 1, step S in the following specification and drawings). Abbreviated). Next, a predetermined time is waited until the mute in the processing of S1 becomes effective (S2), and the tuner 2 extracts the PLL signal so that the RF signal of the newly selected channel (hereinafter referred to as “desired channel”) is extracted. The circuit 14 is controlled (S3). Then, the microcomputer 15 sets a time (hereinafter referred to as “mute release time”) until the mute of the audio signal processing unit 10 is released (S4). The mute release time is set to the time necessary and sufficient to determine whether the desired channel is stationed and to determine which signal format is being broadcast when the desired channel is stationed. Is done.

  After the mute release time set, the microcomputer 15 determines whether or not the desired channel is a channel for performing digital radio broadcasting in the IBOC format signal format based on the presence / absence of signal input from the IDM 16 (S5). Specifically, if no status information signal is input from the IDM 16 (S5: NO), the microcomputer 15 determines that the desired channel is not an IBOC format channel, and the audio signal processing is performed at the same time as the mute release time is over. The mute of the unit 10 is released (S8: YES, S9), and the mute control process is terminated.

  In this case, since the IDM 16 has no decodable signal and cannot generate a blend signal, the signal input to the blend circuit 10a is only an analog audio signal. Therefore, the analog audio signal is output to the audio processing circuit 10b as it is without being blended by the blending circuit 10a, and is processed by the audio processing circuit 10b, the D / A converter 11, and the power amplifier 12. Output from the speaker 13. That is, in this case, the analog radio broadcast of the desired channel is reproduced.

  If there is a status information signal input from the IDM 16 in the process of S5 (S5: YES), the microcomputer 15 determines that the desired channel is an IBOC format channel. Then, the microcomputer 15 refers to the information of the primary service mode included in the status information, and further determines whether or not the desired channel is a channel that is being broadcast with the all-digital format signal (S6).

  When the desired channel is a channel corresponding to the broadcast of the hybrid format signal in the process of S6 (S6: NO), the microcomputer 15 cancels the mute of the audio signal processing unit 10 at the same time as the mute release time is over. (S8: YES, S9), the mute control process is terminated.

  In this case, when the mute control process is completed, decoding by the IDM 16 is not completed, and the signal input to the blend circuit 10a is only an analog audio signal. Therefore, the analog radio broadcast of the desired channel is reproduced. However, as described above, the RD radio 100 is designed so as to preferentially reproduce high-quality digital radio broadcasting. Therefore, when the decoding by the IDM 16 is completed and the blend signal and the digital audio signal are input to the blend circuit 10a, the blend circuit 10a switches the signal output by the blend process from the analog audio signal to the digital audio signal. That is, in this case, when the decoding by the IDM 16 is completed, the broadcast signal output from the speaker 13 is switched from the analog radio broadcast signal to the digital radio broadcast signal.

  Note that the mute release time is 500 ms in the example of the present embodiment, which is slightly longer than the total time required for the processing of S5 and S6, and is sufficiently shorter than the time required for the decoding processing in the IDM 16. For this reason, the audio signal processing unit 10 releases the mute as soon as the determination process of S6 ends. Therefore, the analog radio broadcast is reproduced quickly after the signal format determination processing in S6.

  When the desired channel is a channel corresponding to the all-digital format signal broadcast in the process of S6 (S6: YES), the microcomputer 15 does not input any audio signal from the DSP 9 to the audio signal processing unit 10. The output of the DSP 9 is muted (S7). When the mute release time becomes over, the mute of the audio signal processing unit 10 is released (S8: YES, S9), and the mute control process is terminated.

  In this case, when the mute control process is completed, the decoding by the IDM 16 is not completed, and the output of the DSP 9 is also muted. For this reason, no audio signal is input to the circuit subsequent to the blend circuit 10 a including the blend circuit 10 a, and no sound is output from the speaker 13. Therefore, for example, noise through an analog radio broadcast signal line (a line connecting the DSP 9 and the audio signal processing unit 10) is not output from the speaker 13 via the D / A converter 11 or the like. When the decoding by the IDM 16 is completed, the digital audio signal obtained by the decoding is output from the speaker 13 through the processing of the audio signal processing unit 10, the D / A converter 11, and the power amplifier 12. That is, when the decoding by the IDM 16 is completed, the digital radio broadcast is reproduced from the speaker 13 that has been silent until then.

  That is, the HD radio 100 of this embodiment mutes the DSP 9 and cancels the mute of the audio signal processing unit 10 when the desired channel is all-digital format broadcasting. This eliminates the harmful effect that the noise obtained as a result of processing the subcarrier of the digital broadcast as an analog carrier is output from the speaker 13 before the reproduction of the digital radio broadcast signal, and the digital radio broadcast immediately after the decoding by the IDM 16 is completed. It is supposed to be played. The HD radio 100 can play back the digital radio broadcast upon completion of decoding without letting the user hear unpleasant noise before playing back the digital radio broadcast.

  The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and various modifications are possible within the scope of the technical idea of the present invention. For example, the power amplifier 12 may be muted instead of the audio signal processing unit 10 in the mute control process of FIG.

It is a block diagram which shows the structure of HD radio of embodiment of this invention. It is a flowchart which shows the mute control process performed in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuner 6 IF amplifier 7 IF filter 8 A / D converter 9 Analog signal processing circuit 10 Audio signal processing part 11 D / A converter 12 Power amplifier 13 Speaker 14 PLL circuit 15 Microcomputer 16 IDM
17 Photosensitive unit 18 Remote control 19 Display control circuit 20 Display 100 HD radio SEP Separator

Claims (9)

In a broadcast receiver suitable for receiving a broadcast signal transmitted in an IBOC (In Band On Channel) signal format,
Signal format detection means for detecting the signal format of the received broadcast signal;
And a mute control means for muting only the output of the analog broadcast signal when the detected signal format is an all-digital format. It further comprises channel changing means for changing the receiving channel,
The broadcast receiver according to claim 1, wherein the mute control means mutes the output of all broadcast signals for a predetermined time when the reception channel is changed.   The broadcast receiver according to claim 2, wherein the predetermined time is a time required until a signal format of the broadcast signal is detected. A decoding means for decoding the digital broadcast signal;
4. The broadcast receiver according to claim 3, wherein the predetermined time is longer than a time required for the detection processing by the signal format detection means and shorter than a time required for the decoding processing by the decoding means.   The broadcast receiver according to claim 1, wherein the broadcast receiver is attached to a moving body. In a broadcast receiving method suitable for receiving a broadcast signal transmitted in an IBOC format signal format,
A signal format detection step for detecting a signal format of a broadcast signal to be received;
And a mute control step of muting only the output of the analog broadcast signal when the detected signal format is an all-digital format. A channel changing step for changing the receiving channel;
7. The broadcast receiving method according to claim 6, wherein, in the mute control step, when a reception channel is changed, all broadcast signal outputs are muted for a predetermined time.   The broadcast receiver according to claim 7, wherein the predetermined time is a time required until the detection step is completed. A decoding step for decoding the digital broadcast signal;
9. The broadcast receiving method according to claim 8, wherein the predetermined time is longer than the time required for the detection processing in the signal format detection step and shorter than the time required for the decoding processing in the decoding step.

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