JPH11346165A - Digital broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To not surprise a sugar with erroneous volume correction. SOLUTION: When a user performs selection operation of another program in a state in which a DAB broadcasting is received by a DAB broadcast receiver a program is selected and audited, a system controller 15A makes the gain of a digital gain variable amplifier circuit 18 minimum, mutes the sound, performs program selection control to a channel decoder 14 on the basis of information of FIC inputted from the channel decoder 14, decodes DAB audio frame data of a user's desired program and has them outputted to an audio decoder 17, and has volume correction data outputted to the controller 15A. When the audio decoder 17 starts outputting the audio signal of a new program, the controller 15A gradually increases the gain of a gain variable amplifier circuit 18. After the gain reaches without ±4 dB of the gain in accordance with the volume correction data, the gain of the gain variable amplifier circuit 18 is varied in accordance with the volume correction data of the new program.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiver, and more particularly to a digital broadcast receiver for receiving a digital broadcast to which volume correction information for adjusting a dynamic range for a fixed time unit is added for each program, and for receiving a program desired by a user. The present invention relates to a digital broadcast receiver in which a gain of an audio signal is changed using volume correction information extracted from digital broadcast.

[0002]

2. Description of the Related Art In Europe, DAB (Digital Audio Broadcasting) is used.
dcasting) has been put to practical use. In this DAB, OFDM (Orthogonal Frequency Division Multiplexing Modulation;
A modulation method called thogonal frequency division multiplexing is used, and the transmission symbol is composed of a guard interval and an effective symbol, thereby enabling reception that is resistant to multipath interference. Each carrier of DAB is D
QPSK modulated.

In DAB, band II (87 to 108 MHz band), band III (175 to 250 MHz band), L band (1.452 to 1.49)
Band 2), and band II and band 2
In III, transmission mode 1 (strong in multipath, SFN; suitable for single frequency network) with a transmission frame period of 96 ms and a carrier interval of 1 kHz is used. D in the upper part of FIG.
3 shows a format of a transmission frame signal in transmission mode 1 of AB. First, a NULL symbol of 1.297 ms and 1.
246ms Phase Reference Symbol
There is a synchronization signal consisting of
75 DM symbols are included. The symbols other than the NULL symbol are transmission symbols. The first 0.246 ms is a guard interval, and the remaining 1 ms is a valid symbol.

[0004] The S = second to fourth transmission symbols are FIC (Fast Information Channel) for transmitting various control information necessary for the receiver to select a desired program.
el), S = 5 to 76th transmission symbols are multiplexed and transmitted for subchannels (Sub Channels) of voice and data.
SC (Main Service Channel). Usually, one sub-channel corresponds to one program, and the sub-channel is MSC.
Structure information indicating how multiplexing is performed in F
It is included in the IC, and it is possible to extract the sub-channel relating to the program desired by the user with reference to the FIC.

FIG. 6 is a block diagram of a DAB broadcast receiver for a vehicle. In the in-vehicle DAB broadcast receiver, a DAB broadcast signal having a frequency desired by the user is received by a front end 12 connected to an antenna 11, converted into a predetermined intermediate frequency signal, and output. The I / Q demodulation and FFT are performed on the intermediate frequency signal by the demodulation circuit 13, and complex number data indicating the phase, amplitude, and the like for each carrier are output in symbol units. The complex data for each carrier is input to the channel decoder 14, and is subjected to DQPS symbol demapping, FIC / MS
After C separation is performed, the three effective symbols of the FIC are divided into four equal parts, and then subjected to error detection / correction (Viterbi decoding) and descrambling processing to obtain 12 FIBs (fast information blocks; Fast Information Blocks). ) And F
The data is output to the system controller 15 of the microcomputer in the form of data called IG (Fast Information Group).

On the other hand, the effective symbol of the MSC is divided into 18 symbols and four CIFs (Common Interleav
ed Frame). Each CIF includes a plurality of sub-channels (Sub Channel), and one sub-channel usually corresponds to one program. When the user uses the program selection key of the operation panel 16 to select a desired program in the currently received DAB broadcast, the system controller 1
Reference numeral 5 designates a predetermined program selection control, outputs designation information of a sub-channel corresponding to a desired program by referring to information of the FIC, and a channel decoder 14 selects a sub-channel designated by the system controller 15 from among the four CIFs. , Time deinterleaving, error detection / correction (Viterbi decoding), descrambling and
DAB decoded by decoding B audio frame data
Audio frame data is converted to an audio decoder (MP
EG decoder) 17. DAB audio frame data has a period of 24 ms.

The audio decoder 17 decodes DAB audio frame data and outputs digital audio signals for two channels. This audio signal passes through a digital gain variable amplifying circuit 18 and is supplied to a D / A
The data is D / A converted by the converter 19 and output as an analog audio signal. The audio signal is volume-adjusted by the audio amplifier 20 in accordance with the volume up / down operation by the user, power-amplified, and output to the speaker 21. When the user performs a selection operation of a desired DAB broadcast by using a channel selection key on the operation panel 16, the system controller 15 performs tuning control on the front end 2 to tune to a desired frequency of the DAB broadcast.

By the way, in music having a wide dynamic range such as classical music, a quiet performance portion may not be heard due to the noise of the vehicle. For this reason, the DAB is provided with a volume correction function called DRC (Dynamic Range Control). The station transmits volume correction data (DRC data) in units of a fixed time for each program, and the receiver side transmits the data. The level of a quiet performance portion is automatically raised by using the volume correction data of a user-desired program that is currently being received, so that the user can reliably listen to the program without any volume adjustment operation under noise. .

More specifically, as shown in FIG. 7, volume correction data (DRC data) is added to a part of each DAB audio frame data decoded by the channel decoder 14. The volume correction data DRC _n added to the DAB audio frame data AF _n , AF _{n + 1} , AF _{n + 2} ,... Output from the channel decoder 14 at times n, (n + 1), (n + 2),. DRC _{n + 1} , DRC
_{n + 2} ,... respectively represent the next time (n + 1), (n +
2), (n + 3),... For the DAB audio frame data AF _{n + 1} , AF _{n + 2} , AF _{n + 3} . The volume correction data ranges from 0 dB to +15.
The value takes a step of 0.25 dB in a range up to 75 dB.
The channel decoder 14 adds a new D
Every time decoding the AB audio frame data, and outputs the new volume correcting data DRC _i contained therein to the system controller 15.

When the system controller 15 receives the volume correction data DRC _i added to the DAB audio frame data AF _i at time i from the channel decoder 14, the audio decoder 17 decodes the DAB audio frame data AF _{i + 1} at time i. and while outputting digital audio signal, and set the gain corresponding to the sound volume correcting data DRC _i into a digital variable gain amplifier circuit 18, causing lifting the gain by the amount of DRC _i. This raises the level of the audio signal by up to +15.75 dB.

[0011]

However, the volume correction data added to each DAB audio frame data is not provided with an error detection / correction code, so that an error is likely to occur. In particular, immediately after the user selects another desired program in the currently received digital broadcast or immediately after selecting another digital broadcast and selecting the desired program in the newly selected digital broadcast. In such cases, the reception operation of the DAB broadcast receiver becomes temporarily unstable, so that when the channel decoder 15 resumes decoding the DAB audio frame data of the new desired program, an error may have occurred in the volume correction data. There is a nature. Further, even when the desired program is continuously received, the reception state may temporarily deteriorate due to mobile reception, and an error may occur in the volume correction data.

When an error has occurred in the volume correction data, if a gain corresponding to the volume correction data is directly set in the digital gain variable amplifier circuit 18, the gain can be increased by approximately +1.
5 dB also performs volume correction contrary to the intention of the station, and the user may be surprised at the loud volume. The present invention has been made in view of the above-described problems of the related art, and it is an object of the present invention to provide a digital broadcast receiver that does not surprise the user with incorrect volume correction.

[0013]

In the digital broadcast receiver according to the first aspect of the present invention, each broadcast includes a plurality of pieces of program information, and a digital broadcast to which volume correction information is added for each program in a fixed time unit. Operation means (16) for selecting a digital broadcast and selecting a program within the same broadcast
Digital broadcast receiving means for receiving a digital broadcast of a user desired frequency in accordance with the operation of the operating means, extracting program information desired by the user, restoring an audio signal, and extracting volume correction information of the user desired program (11,
12, 13, 14, 15 A, 17) and a variable gain amplifying means (1
8) and a variable gain control means (15A) for varying the gain of the variable gain amplifying means according to the volume correction information. When a new program of a broadcast or a new program of another broadcast is selected, the variable gain control means (15A) controls the variable gain amplifying means (1).
8) The gain of the variable gain amplifying means (18) is successively compared with the volume correction information of a new desired program extracted by the digital broadcast receiving means while gradually decreasing and then gradually increasing the gain, and the difference between the two. Is smaller than or equal to a certain value, the gain is changed to a gain corresponding to the volume correction information of a new desired program extracted by the digital broadcast receiving means.

[0014] Thereby, since the user has just selected a new program in the same broadcast or a new program in another broadcast, the receiving operation becomes temporarily unstable, and the new desired program information cannot be obtained. While there is a possibility that an error has temporarily occurred in the extracted volume correction information, the gain of the variable gain amplifier is temporarily reduced, and then gradually increased to gradually reduce the audio signal level from a small state. Therefore, a loud sound volume due to an incorrect sound volume correction does not occur. In addition, while the level of the audio signal is gradually increased, the receiving operation for a new program is stabilized and correct volume correction information can be obtained. After the difference with the volume correction information of the new desired program becomes equal to or less than a certain value, the gain of the variable gain amplifier is changed in accordance with the new volume correction information of the new desired program, so that the original The volume can be corrected so that the sound can be reliably heard even under noise.

In the digital broadcast receiver according to the second aspect of the present invention, each broadcast includes a plurality of pieces of program information, and a digital broadcast to which volume correction information is added for each program in a fixed time unit. Operating means (16) for selecting a program in the same broadcast as the channel selection; receiving a digital broadcast of a user-desired frequency in accordance with the operation of the operating means; extracting user-desired program information; restoring an audio signal; Digital broadcast receiving means (11, 12, 13, 1) for extracting volume correction information of a user desired program
4, 15A, 17), a variable gain amplifying means (18) for increasing and decreasing the level by inputting an audio signal, and a variable gain controlling means (15A) for varying the gain of the variable gain amplifying means according to the volume correction information. When the user selects a new program of a broadcast currently being received or a new program of another broadcast using the operation means (16), the gain variable control means ( 1
5A) is to decrease the gain of the variable gain amplifying means (18) once and then gradually increase the gain while changing the gain of the variable gain amplifying means and the digital broadcast receiving means (11, 12, 1).
3, 14, 15A, and 17) are sequentially compared with the volume correction information of the new desired program, and after the difference between the two becomes less than or equal to a certain value, a new desired program extracted by the digital broadcast receiving means is obtained. Only when the volume correction information is within a predetermined range with respect to the current gain of the variable gain amplifier, the gain is changed to a gain corresponding to the volume correction information.

Since the user has just selected a new program in the same broadcast or a new program in another broadcast, the receiving operation becomes temporarily unstable, and the new desired program information is extracted from the desired program information. While there is a possibility that an error has temporarily occurred in the volume correction information, the gain of the variable gain amplifying means is temporarily reduced, and then gradually increased to gradually increase the level of the audio signal from a small state. Therefore, a large volume due to incorrect volume correction does not occur. While the level of the audio signal is gradually increased, the reception operation for a new program is stabilized and correct volume correction information can be obtained. However, the gain of the variable gain amplifier is extracted by the digital broadcast receiver. After the difference from the volume correction information of the new desired program has become equal to or less than a certain value, the volume correction information of the new desired program extracted by the digital broadcast receiving unit becomes a predetermined value with respect to the current gain of the variable gain amplifier. Only when it is within a certain range, the gain is varied according to the volume correction information.

Here, in the volume correction information generated on the station side, the difference between before and after is usually suppressed to a certain level or less. During the continuous reception of the desired program, if the reception state is good and no error occurs in the volume correction information, the gain of the variable gain amplifier is adjusted based on the previous error-free volume correction information extracted by the digital broadcast receiving unit. When variable, the next volume correction information extracted by the digital broadcast receiving means falls within a predetermined range with respect to the current gain of the variable gain amplifying means if there is no error. Since the gain is variable, a desired program is not missed even under noise. On the other hand, even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in the volume correction information, if the volume correction information is out of a predetermined fixed range with respect to the current gain of the variable gain amplifier. Since the volume is not corrected, there is no danger of being surprised by the loud volume.

In the digital broadcast receiver according to a third aspect of the present invention, each broadcast includes a plurality of pieces of program information, and the digital broadcast to which the volume correction information is added for each program in a fixed time unit is used. Operating means (16) for selecting a program in the same broadcast as the channel selection; receiving a digital broadcast of a user-desired frequency in accordance with the operation of the operating means; extracting user-desired program information; restoring an audio signal; Digital broadcast receiving means (11, 12, 13, 1) for extracting volume correction information of a user desired program
4, 15A, 17), a variable gain amplifying means (18) for increasing and decreasing the level by inputting an audio signal, and a variable gain controlling means (15A) for varying the gain of the variable gain amplifying means according to the volume correction information. When the user selects a new program of a broadcast currently being received or a new program of another broadcast using the operation means (16), the gain variable control means ( 1
5A) shows that the gain of the variable gain amplifying means and the digital broadcast receiving means (11, 12, 13, 1) are gradually reduced and then gradually increased.
4, 15A, and 17) are successively compared with the volume correction information of the new desired program, and after the difference between the two becomes less than or equal to a certain value, the volume of the new desired program extracted by the digital broadcast receiving means. The present invention is characterized in that the correction information is changed to a gain corresponding to the volume correction information after limiting the current gain of the variable gain amplifier to a predetermined fixed range.

Since the user has just selected a new program in the same broadcast or a new program in another broadcast, the receiving operation is temporarily unstable, and the new desired program information is extracted. While there is a possibility that an error has temporarily occurred in the volume correction information, the gain of the variable gain amplifying means is temporarily reduced, and then gradually increased to gradually increase the level of the audio signal from a small state. Therefore, a large volume due to incorrect volume correction does not occur. While the level of the audio signal is gradually increased, the reception operation for a new program is stabilized and correct volume correction information can be obtained. However, the gain of the variable gain amplifier is extracted by the digital broadcast receiver. After the difference from the volume correction information of the new desired program becomes equal to or less than a certain value, the volume correction information of the new desired program extracted by the digital broadcast receiving unit is converted to a predetermined gain with respect to the current gain of the variable gain amplifier. The gain is varied according to the volume correction information limited to a certain range.

During continuous reception of the desired program, if the reception state is good and no error occurs in the volume correction information, the gain variable amplification means is based on the previous error-free volume correction information extracted by the digital broadcast receiving means. When the gain is varied, the next volume correction information extracted by the digital broadcast receiving means falls within a predetermined fixed range with respect to the current gain of the variable gain amplifying means if there is no error. , And the desired program is not missed even under noise. on the other hand,
Even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in the volume correction information, a certain range is provided if the volume correction information is out of a predetermined range with respect to the current gain of the variable gain amplifier. Since the volume is corrected by limiting the volume, there is no danger of being surprised by the loud volume.

In the digital broadcast receiver according to a fourth aspect of the present invention, a digital broadcast including a plurality of program information, to which volume correction information is added in fixed time units for each program, is received, and program information desired by the user is received. Digital broadcast receiving means (11, 12, 13, 1) for restoring the extracted audio signal and extracting the volume correction information of the program desired by the user.
4, 15A, 17), a variable gain amplifying means (18) for increasing and decreasing the level by inputting an audio signal, and a variable gain controlling means (15A) for varying the gain of the variable gain amplifying means according to the volume correction information. , The variable gain control means (15A) comprises digital broadcast receiving means (11, 12, 13, 14, 15).
(A, 17) Only when the volume correction information extracted in the gain variable amplification means (18) is within a predetermined fixed range with respect to the current gain, the gain is changed to a gain corresponding to the volume correction information. That is, it is characterized.

Accordingly, if the volume correction information extracted by the digital broadcast receiving means is out of a predetermined range with respect to the current gain of the variable gain amplifying means, the volume is not corrected, so that the volume can be increased in any receiving situation. No more surprises. In addition, in the sound volume correction information generated on the station side, the difference between the front and the back is usually suppressed to a certain value or less. During the continuous reception of the desired program, if the reception state is good and no error occurs in the volume correction information, the gain of the variable gain amplifier is adjusted based on the previous error-free volume correction information extracted by the digital broadcast receiving unit. When variable, the next volume correction information extracted by the digital broadcast receiving means falls within a predetermined range with respect to the current gain of the variable gain amplifying means if there is no error. Since the gain is variable, a desired program is not missed even under noise. On the other hand, even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in the volume correction information, if the volume correction information is out of a predetermined fixed range with respect to the current gain of the variable gain amplifier. Since the volume is not corrected, there is no danger of being surprised by the loud volume.

In the digital broadcast receiver according to the fifth aspect of the present invention, a digital broadcast including a plurality of pieces of program information, to which volume correction information is added in fixed time units for each program, is received, and program information desired by the user is received. Digital broadcast receiving means (11, 12, 13, 1) for restoring the extracted audio signal and extracting the volume correction information of the program desired by the user.
4, 15A, 17), a variable gain amplifying means (18) for increasing and decreasing the level by inputting an audio signal, and a variable gain controlling means (15A) for varying the gain of the variable gain amplifying means according to the volume correction information. , The variable gain control means (15A) comprises digital broadcast receiving means (11, 12, 13, 14, 15).
A, 17) the volume correction information extracted in step 17 is changed to a gain corresponding to the volume correction information after limiting the current gain of the variable gain amplifier 18 to a predetermined fixed range. It is characterized by.

The volume correction information generated on the station side is usually
The difference between before and after is kept below a certain level. During the continuous reception of the desired program, if the reception state is good and no error occurs in the volume correction information, the gain of the variable gain amplifier is adjusted based on the previous error-free volume correction information extracted by the digital broadcast receiving unit. When variable, the next volume correction information extracted by the digital broadcast receiving means falls within a predetermined range with respect to the current gain of the variable gain amplifying means if there is no error. Since the gain is variable, a desired program is not missed even under noise. On the other hand, even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in the volume correction information, if the volume correction information is out of a predetermined fixed range with respect to the current gain of the variable gain amplifier. Since the volume is corrected within a certain range, there is no fear of being surprised by a large volume.

[0025]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an in-vehicle DAB broadcast receiver according to the present invention, and the same components as those in FIG. 6 are denoted by the same reference numerals. The digital gain variable amplification circuit 18 can set the gain to an arbitrary value of 0.25 dB in the range from the minimum of -80 dB to the maximum of +15.75 dB by the variable gain control by the system controller 15A.

When the user selects a new program being broadcast on the operation panel 16 while the DAB broadcast receiver is receiving a DAB broadcast of a certain frequency, the system controller 15A issues a channel decoder. 14 to control the program selection to output the sound of a new user-desired program. Before performing the program selection control, the gain of the digital gain variable amplifier circuit 18 is once reduced to the minimum-.
Set to 80 dB and apply audio mute. After the program selection control, the system controller 15A starts when the audio decoder 17 starts outputting the audio signal of the new user-desired program (when the audio decoder 17 finishes decoding the first DAB audio frame data of the new program). And the gain of the digital gain variable amplifier circuit 18 is increased by, for example, 0.25 dB.

While the gain is being increased, the volume correction data extracted from the DAB audio frame data of the new user-desired program periodically input from the channel decoder 14 and the gain set by the digital gain variable amplification circuit 18 are used. When the difference between the two is within ± 4 dB, the gain of the digital gain variable amplification circuit 18 is variably set in accordance with the volume correction data extracted from the DAB audio frame data of the new program desired by the user.

Further, when the user performs a tuning operation of a DAB broadcast of another frequency on the operation panel 16, the system controller 15A performs tuning control on the front end 12 to set a new frequency of the DAB broadcast desired by the user. Synchronize. At first, the channel decoder 14 treats the program last listened to the same DAB broadcast last time as a user-desired program, controls the selection of the program, and outputs sound. The gain of the variable gain amplifier circuit 18 is temporarily set to the minimum value of -80 dB, and the audio mute is applied.

After the program selection control, the digital gain variable amplifying circuit 1 starts when the audio decoder 17 starts outputting an audio signal of a new user-desired program.
For example, the gain of 8 is increased by 0.25 dB. While increasing the gain, the channel decoder 1
4 for a new user-desired program periodically input from DA
The volume correction data extracted from the B audio frame data and the gain set in the digital gain variable amplifier circuit 18 are sequentially compared, and when the difference between the two becomes within ± 4 dB, the DAB audio frame data of a new user desired program is obtained. The gain of the digital gain variable amplification circuit 18 is variably set in accordance with the volume correction data extracted from. Other components of the in-vehicle DAB broadcast receiver are configured exactly the same as in FIG.

Next, the operation of the above embodiment will be described with reference to FIG. FIG. 2 shows the system controller 15A.
Is a flowchart showing a reception control process according to the first embodiment. When the power supply of the on-vehicle DAB broadcast receiver is turned on, the system controller 15A sets the gain of the digital gain variable amplifying circuit 18 to a minimum of -80 dB, applies audio mute (step S10 in FIG. 2), and performs tuning control on the front end 12. The DAB that I listened to just before the power off last time
Synchronize with the broadcast frequency (step S11). The intermediate frequency signal of the DAB broadcast output from the front end 12 is subjected to I / Q demodulation and FFT processing in a demodulation circuit 13, and complex number data indicating the phase and amplitude of each carrier in symbol units is output to a channel decoder 14. In the channel decoder 14, the complex number data for each carrier is
After performing QPS symbol demapping and FIC / MSC separation, the three effective symbols of the FIC are divided into four equal parts, and then subjected to error detection / correction (Viterbi decoding) and descrambling processing to obtain 12 FIBs. (High-speed information block) and output to the system controller 15A in the form of data called FIG (high-speed information group).

On the other hand, the MSC effective symbol is divided into 18 symbols and reconstructed into four CIFs. Each CIF includes a plurality of sub-channels, and one sub-channel usually corresponds to one program. When the FIC is input from the channel decoder 14 after performing the tuning control, the system controller 15A treats, as the user-desired program, the program that was previously listened to immediately before the power was turned off, of the DAB broadcast being received. Is selected, and the sub-channel designation information corresponding to the program is output with reference to the FIC information (step S11). The channel decoder 14 outputs DAB audio frame data AF _i (i is 2) of the program designated by the system controller 15A.
Indicates the time that elapses in units of 4 ms,..., (N−1),
n, (n + 1), takes a value of ...) decodes the DAB audio frame data AF _i decoded output to the audio decoder 17, also the volume correction data DRC _i the system controller 15A of the DAB audio frame data AF _i Output to

The audio decoder 17 decodes the DAB audio frame data AF _i input from the channel decoder 14, and outputs the digital audio signals of two channels. When the audio decoder 17 starts outputting the audio signal of the user-desired program, the operations of the front end 12, the demodulation circuit 13, the channel decoder 14, and the like are not yet stable, and the volume does not have the error detection / correction code. There is a possibility that an error has occurred in the correction data DRC _i (note that the volume correction data DR
Even if an error occurs in C _i , the value of DRC _i is 0 dB to +1.
5.25 dB).

The system controller 15A increases the gain of the digital gain variable amplifier circuit 18 by, for example, 0.25 dB from the time when the audio decoder 17 starts outputting the audio signal of the program desired by the user (YES in step S12). , S13), and gradually increases the level of the audio signal. The output of the digital gain variable amplification circuit 18 is the D / A converter 1
At 9, it is converted into an analog audio signal. And
After the volume is adjusted and the power is amplified by the audio amplifier 20, it is output to the speaker 21.

While the gain is being increased, the D of the user-desired program periodically input from the channel decoder 14 is
Volume extracted from AB audio frame data AF _i correction data DRC _i and digital variable gain amplifier circuit 1
8 are sequentially compared with the current set gain G (step S
14, S15). Then, after the difference between them becomes within ± 4dB variably set the gain of the digital variable gain amplifier circuit 18 in accordance with the volume correction data DRC _i extracted from DAB audio frame data AF _i user desired program (step YES at S15, S16, S1
7, S16).

For example, the digital gain variable amplification circuit 1
The gain G of 8 is increased by 0.25 dB from -80 dB.
At time n when G = + 5 dB, the channel
Volume correction data DRC input from decoder 14_n= +
When the difference is within ± 4 dB for the first time,
The system controller 15A has an audio decoder 17
DAB audio frame data AF_{n + 1}Decode
Digital audio output
The gain of the in-variable amplification circuit 18 is set to DRC_n= + 1dB
Set. Then DRC_{n + 1}= + 1.5dB, DRC
_{n + 2}= + 2.0 dB, the audio decoder 17
Is DAB audio frame data AF _{n + 2}Decode
At the beginning of the audio signal output
The gain of the variable gain amplifier 18 is set to DRC_{n + 1}= + 1.
5 dB, DAB audio frame data AF
_{n + 3}At which audio signal output is started after decoding
To set the gain of the digital gain variable amplifier circuit 18 to DR.
C_{n + 2}= + 2.0 dB is set. The same process is repeated hereafter.
Return.

System controller 1 based on power-on
In response to tuning control and program selection control by 5A,
Immediately after the AB broadcast receiver newly receives the DAB broadcast of the user desired frequency and starts outputting the audio signal of the user desired program, the reception operation is still unstable, so the volume correction data DRC extracted from the desired program information _An error may have occurred in _i . However, here, the gain of the digital gain variable amplifying circuit 18 is gradually increased after being minimized, and the level of the audio signal is gradually increased from the minimum state. Never. In addition, after the level of the audio signal gradually increases, the receiving operation is finally stabilized, and the gain is taken over by the gain according to the volume correction data with no error. Therefore, the volume is naturally increased, and the user does not feel uncomfortable.

Further, while the level of the audio signal is gradually increased, the receiving operation for the desired program is stabilized, and correct volume correction data DRC _i can be obtained.
Digital variable gain after the difference between the volume correction data DRC _i became constant following new desired program is periodically extracted set gain G and the channel decoder 14 of the amplifier circuit 18, the volume of the new desired program Correction data DRC
By setting the gain according to _i , it is possible to perform the original sound volume correction and to be able to surely hear even under noise.

Thereafter, when the user operates the operation panel 16 to select another program in the currently received DAB broadcast, the system controller 15A firstly sets the gain to the digital gain variable amplification circuit 18 in the same manner as described above. -8
After the audio mute has been applied (YES in step S18, S19), the channel decoder 1
4, the sub-channel designation information corresponding to the new user-desired program is output to the channel decoder 14 with reference to the FIC information input in advance from step 4 (step S2).
0). Channel decoder 14 outputs the DAB audio frame data AF _i of the program designated by the system controller 15A to the audio decoder 17, and outputs a sound volume correcting data DRCi the DAB audio frame data AF _i to the system controller 15A.

The audio decoder 17 decodes the DAB audio frame data AF _i input from the channel decoder 14, and outputs the digital audio signals of two channels. At the time when the audio decoder 17 starts outputting the audio signal of the new user-desired program, the operation of the channel decoder 14 and the like is not yet stable, and the volume correction data DRC _i having no error detection / correction code has an error. May be happening.

The system controller 15A increases the gain of the digital gain variable amplifier circuit 18 from the time when the audio decoder 17 starts outputting the audio signal of the program desired by the user (YE in step S12).
S, S13). While increasing the gain,
The volume correction data DRC _i extracted from the DAB audio frame data AF _{i of the} user-desired program periodically input from the channel decoder 14 is sequentially compared with the current set gain G of the digital gain variable amplifier circuit 18 (step S15). . Then, after the difference between them becomes within ± 4dB, volume correction data DRC extracted from DAB audio frame data AF _i user desired program
_The gain of the digital gain variable amplifying circuit 18 is variably set in accordance with _i (Steps S16 and S17 are repeated).

When switching to another program of the same broadcast while receiving a certain DAB broadcast, immediately after starting the output of the audio signal of the new program, the receiving operation is still unstable, so it is extracted from the desired program information. Volume correction data DRC
There may be an error in _i , but here too,
Since the gain of the digital gain variable amplifier circuit 18 is once increased to a minimum and then gradually increased, there is no occurrence of a large volume due to an incorrect volume correction. In addition, the reception operation is finally stabilized after the gain is gradually increased, and the gain is taken over by the gain according to the volume correction data with no error. Therefore, the volume is naturally increased, and the user does not feel uncomfortable.

Then, the digital gain variable amplifying circuit 1
After the difference between the set gain G of 8 and the volume correction data DRC _i of the new desired program periodically extracted by the channel decoder 14 becomes equal to or less than a certain value, the volume correction data DRC _i of the new desired program Since the corresponding gain is set, the original volume correction can be performed, and the sound can be reliably heard even under noise.

On the other hand, when the user operates the operation panel 16 to select a DAB broadcast of another frequency, the system controller 15A operates the digital gain variable amplification circuit 1
After the audio mute is applied with the gain of the minimum of -80 dB (YES in step S21, S22), tuning control is performed on the front end 12 to tune to the frequency of the DAB broadcast desired by the user (step S2).
3). After performing the tuning control, the system controller 15A sends a new DAB broadcast F
Waiting for the input of an IC, when the input is made, the program that was last listened to the newly tuned DAB broadcast is treated as the user's desired program, and the selection of the program is controlled (step S23). Channel decoder 14 system controller decodes the DAB audio frame data AF _i of the specified program by 15A, the audio decoder DAB audio frame data AF _i decoded 17
To the DAB audio frame data AF _i
Of the volume correction data DRC _i of the system controller 15
Output to A.

The audio decoder 17 decodes the DAB audio frame data AF _i which sequentially inputted from the channel decoder 14, and outputs the digital audio signal. When the audio decoder 17 starts outputting an audio signal of a new DAB broadcast user desired program, the front end 12, the demodulation circuit 13,
The operation of the channel decoder 14 is not stable,
Volume correction data DRC _i without error detection / correction code
Error may have occurred.

The system controller 15A increases the gain of the digital gain variable amplifying circuit 18 by 0.25 dB from the time when the audio decoder 17 starts outputting the audio signal of the program desired by the user, and slightly reduces the level of the audio signal. (YES in step S12, repetition of S13). While the gain is being increased, the volume correction data DRC _i extracted from the DAB audio frame data AF _{i of the} user-desired program periodically input from the channel decoder 14 and the current setting gain G of the digital gain variable amplifier circuit 18 Are sequentially compared (steps S14 and S15). And
After the difference between the two becomes within ± 4dB variably set the gain of the digital variable gain amplifier circuit 18 in accordance with the volume correction data DRC _i extracted from DAB audio frame data AF _i user desired program (step S1
6, repetition of S17).

Under the tuning control by the system controller 15A, the DAB broadcast receiver newly receives the DAB broadcast of the user's desired frequency, and immediately after starting to output the audio signal of a certain desired program, the receiving operation is still unstable. Therefore, the volume correction data DRC extracted from the desired program information
_An error may have occurred in _i . However, also in this case, the gain of the digital gain variable amplifier circuit 18 is gradually increased after being minimized, so that a large volume due to incorrect volume correction does not occur. In addition, the reception operation is finally stabilized after the gain is gradually increased, and the gain is taken over by the gain according to the volume correction data with no error. Therefore, the volume is naturally increased, and the user does not feel uncomfortable.

Then, the digital gain variable amplifier circuit 1
After the difference between the set gain G of 8 and the volume correction data DRC _i of the new desired program periodically extracted by the channel decoder 14 becomes equal to or less than a certain value, the volume correction data DRC _i of the new desired program By setting the appropriate gain, the original volume correction can be performed, and the sound can be reliably heard even under noise.

The reception control process of FIG. 2 performed by the system controller 15A may be modified as shown in FIG. The difference between FIG. 2 and FIG. 3 is that step S15 in FIG.
And that the process of step S24 is added between steps S17 and S16. The difference between FIG. 2 and FIG. 3 will be described. In FIG. 2, in response to a user's program selection operation or DAB broadcast channel selection operation, the system controller 15 </ b> A
Is once set to the minimum gain, and then gradually increases.
Gain G and volume correction data D extracted from a new program
After the difference from RC becomes within ± 4 dB, the gain indicated by the volume correction data DRC extracted from the new program is set in the digital gain variable amplifier circuit 18.

On the other hand, in FIG. 3, after the gain G of the digital gain variable amplifier circuit 18 is once set to the minimum gain, the gain G gradually increases. During the increase, the gain G and the volume correction data DRC extracted from a new program are used. After the difference becomes zero, the gain indicated by the volume correction data DRC extracted from the new program is set in the digital gain variable amplifier circuit 18. Also in this case, the user is unstable reception operation immediately after the program selection operation or DAB broadcasting station selecting operation, a possibility that an error occurs in a desired program are extracted from the information volume correction data DRC _i , The gain of the digital gain variable amplifying circuit 18 is gradually increased after being minimized, so that a large volume due to erroneous volume correction does not occur. In addition, the reception operation is finally stabilized after the gain is gradually increased, and the gain is taken over by the gain according to the volume correction data with no error. Therefore, the volume is naturally increased, and the user does not feel uncomfortable.

In FIG. 2, while the gain G of the digital gain variable amplifier circuit 18 is increasing, the difference between the gain G and the volume correction data DRC extracted from the new program information is ± 4.
After that, the gain indicated by the volume correction data DRC extracted from the new program information is set as it is in the digital gain variable amplifying circuit 18 as shown in FIG. Only when the difference between the gain G and the volume correction data DRC extracted from the new program information is within ± 4 dB, the gain indicated by the volume correction data is set, and the difference between the gain G and the volume correction data is ± When it exceeds 4 dB, the gain of the digital gain variable amplifier circuit 18 is not changed (step S24 in FIG. 3).

Thus, the volume correction data extracted from the new program information is stored in the digital gain variable amplifying circuit 18.
If the current gain G is out of a certain range, the volume is not corrected, so that there is no danger of being surprised by a large volume in any receiving situation. In particular, in the volume correction data DRC generated on the station side, the difference between before and after is usually suppressed to ± 4 dB or less. During the continuous reception of the desired program, if the reception state is good and no error occurs in the volume correction data DRC, the digital gain variable amplifier circuit is based on the error-free volume correction data DRC extracted from the new program information the previous time. When the gain is changed, the next volume correction data DRC extracted from the new program information falls within ± 4 dB with respect to the current gain of the digital gain variable amplifier circuit 18 if there is no error. The gain is changed in accordance with the volume correction data DRC of, so that the desired program is not missed even under noise. on the other hand,
Even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in a certain volume correction data DRC extracted from the new program information, the current gain G of the digital gain variable amplification circuit 18 is ± 4 dB. If it is out of the range, the volume is not corrected, so there is no danger of being surprised by the loud volume. Note that, of course, step S15 'in FIG. 3 may be changed to step S15 in FIG.

The reception control process of FIG. 2 performed by the system controller 15A is modified as shown in FIG.
Steps S24, S25, and S26 may be added after 17. The difference between FIG. 2 and FIG. 4 will be described. In FIG. 2, after the system controller 15A temporarily sets the gain G of the digital gain variable amplification circuit 18 to the minimum gain, the gain G gradually increases. The difference from the volume correction data DRC extracted from the program is ± 4
After that, the gain indicated by the volume correction data DRC extracted from the new program information is set as it is in the digital gain variable amplification circuit 18 (step S1).
7, S16).

On the other hand, in FIG. 4, the system controller 15A gradually increases the gain G of the digital gain variable amplifying circuit 18 after the system controller 15A temporarily sets the gain G to the minimum gain. The difference from the volume correction data DRC extracted from the program is ± 4
After that, when the difference between the gain G of the digital gain variable amplifier circuit 18 and the volume correction data DRC extracted from the new program information is within ± 4 dB, the gain indicated by the volume correction data DRC is set. (YES in step S24, S16).

However, the gain G and the volume correction data DRC
Is greater than ± 4 dB (step S24).
, NO), G + 4 dB (volume correction data DRC> G + 4
dB) or G-4 dB (volume correction data DR)
Volume correction data DR limited to C <G−4 dB)
C ′ is obtained, and the gain indicated by the volume correction data DRC ′ after the restriction is set (steps S25 and S26).

Specifically, while the current gain G of the digital gain variable amplifying circuit 18 is +5.00 dB, the volume correction data DR extracted from the new program information
If C is +6.00 dB (or +4.00 dB), since G falls within the range of ± 4 dB with respect to G, G is changed to +6.00 dB (or +4.00 dB).
While the current gain G is +5.00 dB, the volume correction data DRC extracted from the new program information is +1.
If it is 3.50 dB (or +0.00 dB), G
G does not fall within the range of ± 4 dB.
Only change to 9.00 dB (or +1.00 dB).

According to the modification of FIG. 4, during the continuous reception of the desired program, the reception state is good, and the volume correction data DR
If no error occurs in C, the gain was extracted from the new program information when the gain of the digital gain variable amplification circuit 18 was previously varied based on the error-free volume correction data DRC extracted from the new program information. If there is no error, the next volume correction data DRC falls within ± 4 dB with respect to the current gain of the digital gain variable amplification circuit 18, so that the gain is changed according to the next volume correction data DRC, and the noise is reduced. Never miss a desired program below. On the other hand, even if the reception condition deteriorates during the continuous reception of the desired program and an error occurs in a certain volume correction data DRC extracted from the new program information, the current gain G of the digital gain variable amplifier circuit 18 does not change. ± 4d
If it is out of the range of B, G + 4 dB or G-4d
Since the volume correction is limited to B, there is no danger of being surprised by the loud volume. It is needless to say that step S15 in FIG. 4 may be changed to step S15 ′ in FIG.

Step S1 in FIGS. 2, 3 and 4
2 may be omitted, and steps S10, S19, S23
May be set to -100 dB, -60 dB, or the like. Further, in step S13, while the gain of the digital gain variable amplifier circuit 18 is equal to or less than 0 dB, the gain may be increased in units other than 0.25 dB, such as 1 dB or 2 dB.

[0058]

According to the present invention, when the user selects a new program in the same broadcast or a new program in another broadcast, the level of the audio signal is gradually increased from a low level. Therefore, a large volume due to an incorrect volume correction does not occur. Then, when the difference between the gain of the variable gain amplifying means and the volume correction information extracted from the new desired program information becomes equal to or less than a certain value, the original volume correction is performed, so that it is possible to reliably listen even under noise.

[Brief description of the drawings]

FIG. 1 is an in-vehicle DAB according to one embodiment of the present invention.
It is a block diagram of a broadcast receiver.

FIG. 2 is a flowchart showing a reception control process performed by the system controller of FIG. 1;

FIG. 3 is a flowchart illustrating a reception control process performed by a system controller according to a modified example of FIG. 1;

FIG. 4 is a flowchart illustrating a reception control process performed by a system controller according to another modification of FIG. 1;

FIG. 5 is an explanatory diagram illustrating a configuration of a DAB transmission frame signal.

FIG. 6 is a block diagram of a conventional in-vehicle DAB broadcast receiver.

FIG. 7 is an explanatory diagram showing a relationship between DAB audio frame data and volume correction data.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Antenna 12 Front end 13 Demodulation circuit 14 Channel decoder 15A System controller 16 Operation panel 17 Audio decoder 18 Digital gain variable amplification circuit 19 D / A converter 20 Audio amplifier 21 Speaker

Claims (5)

[Claims] 1. Each broadcast includes a plurality of pieces of program information, and for digital broadcasts to which volume correction information is added in fixed time units for each program, digital broadcast selection and program selection within the same broadcast are performed. Operating means for performing, and digital broadcast receiving means for receiving a digital broadcast of a user-desired frequency in accordance with an operation of the operation means, extracting program information desired by the user, restoring an audio signal, and extracting volume correction information of the user-desired program. A digital broadcast receiver comprising: a gain variable amplifying means for receiving an audio signal to increase or decrease the level; and a variable gain control means for varying the gain of the variable gain amplifying means according to the volume correction information. By means, when a new program of the currently received broadcast is selected or when a new program of another broadcast is selected, the gain is changed. The control means sequentially reduces the gain of the variable gain amplifying means and then gradually increases the gain of the variable gain amplifying means and the volume correction information of a new desired program extracted by the digital broadcast receiving means, while gradually increasing the gain. A digital broadcast receiver characterized in that, after the difference between the two becomes equal to or less than a certain value, the gain is changed to a gain according to the volume correction information of a new desired program extracted by the digital broadcast receiving means. 2. A method for selecting a digital broadcast and selecting a program in the same broadcast for a digital broadcast in which each broadcast includes a plurality of pieces of program information and to which volume correction information is added in fixed time units for each program. Operating means for performing, and digital broadcast receiving means for receiving a digital broadcast of a user-desired frequency in accordance with an operation of the operation means, extracting program information desired by the user, restoring an audio signal, and extracting volume correction information of the user-desired program. A digital broadcast receiver comprising: a gain variable amplifying means for receiving an audio signal to increase or decrease the level; and a variable gain control means for varying the gain of the variable gain amplifying means according to the volume correction information. By means, when a new program of the currently received broadcast is selected or when a new program of another broadcast is selected, the gain is changed. The control means sequentially reduces the gain of the variable gain amplifying means and then gradually increases the gain of the variable gain amplifying means and the volume correction information of a new desired program extracted by the digital broadcast receiving means, while gradually increasing the gain. After the difference between the two becomes equal to or less than a certain value, the volume correction information of the new desired program extracted by the digital broadcast receiving means is within a predetermined fixed range with respect to the current gain of the variable gain amplifier. A digital broadcast receiver, wherein the gain is changed to a gain corresponding to the volume correction information. 3. Each broadcast includes a plurality of pieces of program information, and for digital broadcasts to which volume correction information is added in fixed time units for each program, the digital broadcast selection and the program selection within the same broadcast are performed. Operating means for performing, and digital broadcast receiving means for receiving a digital broadcast of a user-desired frequency in accordance with an operation of the operation means, extracting program information desired by the user, restoring an audio signal, and extracting volume correction information of the user-desired program. A digital broadcast receiver comprising: a gain variable amplifying means for receiving an audio signal to increase or decrease the level; and a variable gain control means for varying the gain of the variable gain amplifying means according to the volume correction information. By means, when a new program of the currently received broadcast is selected or when a new program of another broadcast is selected, the gain is changed. The control means sequentially reduces the gain of the variable gain amplifying means and then gradually increases the gain of the variable gain amplifying means and the volume correction information of a new desired program extracted by the digital broadcast receiving means, while gradually increasing the gain. After the difference between the two becomes less than a certain value, the volume correction information of the new desired program extracted by the digital broadcast receiving means is limited to a predetermined fixed range with respect to the current gain of the variable gain amplifying means. A digital broadcast receiver characterized in that the gain can be varied according to correction information. 4. Receiving a digital broadcast including a plurality of pieces of program information to which volume correction information has been added in fixed time units for each program, extracting program information desired by the user, restoring an audio signal, and Digital broadcast receiving means for extracting volume correction information, variable gain amplification means for inputting and reducing the level of an audio signal, and variable gain control means for varying the gain of the variable gain amplification means according to the volume correction information. In the digital broadcast receiver provided with, the variable gain control means determines that the volume correction information extracted by the digital broadcast receiving means is within a predetermined constant range with respect to the current gain of the variable gain amplifying means. A digital broadcast receiver characterized in that the gain can be varied according to volume correction information. 5. A digital broadcast including a plurality of pieces of program information, to which volume correction information is added in fixed time units for each program, receiving program information desired by the user, restoring an audio signal, and Digital broadcast receiving means for extracting volume correction information, variable gain amplification means for inputting and reducing the level of an audio signal, and variable gain control means for varying the gain of the variable gain amplification means according to the volume correction information. In the digital broadcast receiver, the variable gain control means is responsive to the volume correction information extracted by the digital broadcast receiving means after limiting the current gain of the variable gain amplifying means to a predetermined constant range. A digital broadcast receiver characterized in that the gain is variable.