JP2007043501A - Television receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a sense of discomfort of a user by adjusting output levels of a video and a sound in response to a reception state. <P>SOLUTION: A television receiver 10 is designed to output the video in response to a video signal and the sound in response to a sound signal after receiving a television broadcasting signal having the video signal and the sound signal providing a luminance signal and a color signal. The television receiver 10 comprises attenuators 24, 26 for each adjusting a level of the luminance signal, an attenuator 25 and a variable amplifier 27 for adjusting a level of a color signal, and an attenuator 33 and a variable amplifier 34 for adjusting a level of the sound signal. A control unit 15 is designed to adjust the levels of the luminance signal, the color signal, and the sound signal by controlling the variable amplifiers in response to the reception state of the television broadcasting signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a television receiver that receives a television (TV) broadcast signal, and in particular, an on-vehicle television receiver capable of adjusting the output level of a video signal and / or an audio signal according to the reception state of the television broadcast signal. It relates to the device.

  In general, when a television broadcast signal is received by a vehicle-mounted television receiver mounted on a moving body such as a vehicle, the reception state such as the received electric field strength fluctuates with the movement of the vehicle. A situation occurs in which reception is not good. That is, when the received electric field strength decreases, the signal-to-noise (S / N) characteristic in the television receiver deteriorates, and the noise level in the television broadcast signal, particularly the video signal, increases and is displayed on the monitor. The image may feel very difficult to see.

  For example, when receiving a terrestrial analog television broadcast signal, if the vehicle goes out of the reception area, the monitor screen is in a so-called snow noise state, and the sound may contain noise, and the user may feel uncomfortable. It was. On the other hand, in the case of a terrestrial digital television broadcast signal, if the vehicle is located within the reception area, the television can be viewed with high image quality / high sound quality. However, once the vehicle is out of the reception area, reception is suddenly interrupted.

  By the way, in-vehicle television receivers are provided with a mute circuit that automatically reduces the volume when the reception state deteriorates in order to prevent annoying noise when the reception state deteriorates. When the state returns to a good state, fade-in processing is performed in which the electronic volume is controlled to gradually recover the volume.

  Then, in order to perform appropriate mute control, it is determined whether or not the vehicle is in the peripheral area of the reception area based on the position data from the GPS device. If the fade-in control time is set longer and it is determined that the vehicle is located inside the reception area, the fade-in time is set shorter (see, for example, Patent Document 1).

  In addition, in order to prevent a sudden interruption in audio output, when detecting the reception state of the audio information and predicting that the reception state is blocked or returned, the volume for the audio information is gradually reduced or increased, There is one that prevents sudden interruption of audio output (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 2001-156656 (Pages 2 to 3, FIGS. 1 to 4) JP-A-10-154944 (pages 3 to 4, FIGS. 1 to 7)

  Since the conventional television receiver is configured as described above, that is, the time for fade-in control at the time of mute release is changed according to the position of the vehicle. Although there is no annoying discomfort to the user for the video, if the analog TV broadcast signal is being received for the video, the monitor screen may be in a snow state and the user may feel the discomfort.

  If a digital TV broadcast signal is being received, the reception is suddenly interrupted once it goes out of the reception area, and the image is suddenly interrupted even though the sound is appropriately muted for the user. As a result, the user sometimes felt uncomfortable.

  Even if the volume of the audio information is gradually decreased or increased when the reception state is predicted to be cut off or returned, the user does not take any action on the video. I felt uncomfortable.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to obtain a television receiver capable of reducing user discomfort by adjusting the output level of video and audio according to the reception state. Objective.

  The television receiver according to the present invention includes a first adjustment unit that controls the level of the luminance signal, a second adjustment unit that controls the level of the color signal, and a third adjustment unit that controls the level of the audio signal. Based on the detection means for detecting the reception state of the television broadcast signal, the table indicating the relationship between the control level and the reception state in the first adjustment means to the third adjustment means, the reception state and the table And control means for controlling the first to third adjusting means.

  According to the present invention, since it is configured to control the levels of the luminance signal, the color signal, and the audio signal according to the reception state of the television broadcast signal, it is possible to prevent a situation such as sudden interruption of the video, Discomfort can be reduced.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an example of a television receiver according to Embodiment 1 of the present invention. The illustrated television receiver 10 receives a terrestrial analog television broadcast signal. In FIG. 1, a television receiver 10 includes an antenna 11, a tuner (including a down converter) 12, a video detection amplification unit 13, an audio detection amplification unit 14, and a control unit (control means) 15, and video detection. The outputs of the amplifying unit 13 and the sound detection amplifying unit 14 are given to an RGB (Red (red), Green (green), Blue (blue)) demodulation circuit 16 and a sound demodulation circuit 17, respectively.

  As shown in the figure, the image detection amplifying unit 13 includes an image surface acoustic wave filter (image SAWFIL) 21, an image detector 22, a YC (luminance signal (Y signal), color signal (C signal)) separator 23, and an attenuator. (Attenuators) 24 and 25, and variable amplifiers 26 and 27, and the sound detection amplification unit 14 includes a sound SAWFIL 31, a sound detector 32, an attenuator 33, and a variable amplifier 34. The control unit 15 includes an arithmetic processing unit 41 and a storage unit 42. The storage unit 42 has a reception field strength-control voltage table 100 indicating a relationship between a reception field strength and a control voltage, which is one of reception states, in advance. (This control voltage will be described later).

  When the user selects a desired broadcast channel (Ch), the TV broadcast signal received by the tuner unit 12 via the antenna 11 is down-converted to the baseband band by the downconverter, and is used as a baseband signal. 13 and the voice detection amplification unit 14. The TV broadcast signal, that is, the baseband signal includes a composite video signal having a Y signal and a C signal and an audio signal, and the video detection amplification unit 13 passes only the band of the video signal by the video SAWFIL 21, The baseband signal is detected by the video detector 22 and a video signal is output.

  This video signal is separated into a Y signal and a C signal by a YC separator 23. The Y signal and the C signal are attenuated by attenuators 24 and 25, respectively, and then amplified by variable amplifiers 26 and 27, respectively. Are sent to the RGB demodulation circuit 16.

  On the other hand, in the voice detection amplification unit 14, only the voice signal band is passed by the voice SAWFIL 31, the baseband signal is detected by the voice detector 32, and the voice signal is output. The sound signal is attenuated by the attenuator 33, amplified by the variable amplifier 34, and sent to the sound demodulation circuit 17.

  The tuner unit 12 performs AGC (Automatic Gain Control) when receiving a TV broadcast signal, and an AGC voltage used for performing this AGC is given to an electric field strength detecting means (detecting means) 51 to detect electric field strength. The means 51 detects the received electric field intensity according to the AGC voltage (there is a correlation between the AGC voltage and the received electric field intensity, so that the received electric field intensity can be known from the AGC voltage). The arithmetic processing unit 41 obtains a control voltage by referring to the received electric field strength-control voltage table in accordance with the received electric field strength given from the electric field strength detecting means 51, and a variable amplifier as described later by using this control voltage. 26 and 27 and the amplification factor of the variable amplifier 34 are changed.

Next, the operation will be described.
Referring to FIGS. 1 and 2, when one channel (Ch) of terrestrial analog television broadcasting is received (step ST1), as described above, the electric field strength detecting means 51 receives the received electric field strength based on the AGC voltage. Is detected and given to the arithmetic processing unit 41 (step ST2). The arithmetic processing unit 41 compares the preset electric field strength threshold value with the received electric field strength, and determines whether or not mute (soft mute) is necessary based on the comparison result (step ST3).

  For example, if the received electric field strength is greater than or equal to the electric field strength threshold, the arithmetic processing unit 41 determines that soft mute is not necessary, and proceeds to the next processing. On the other hand, if the received electric field strength is smaller than the electric field strength threshold, the arithmetic processing unit 41 determines that soft mute is necessary, and executes soft mute as follows.

  As described above, the Y signal and the C signal are attenuated by the attenuators 24 and 25, respectively, but at this time, the Y signal and the C signal are leveled down until just before the no-signal state. Similarly, the audio signal is leveled down by the attenuator 33 until just before the no-signal state. The arithmetic processing unit 41 refers to the received electric field intensity-control voltage table stored in the storage means 42 to obtain a control voltage corresponding to the received electric field intensity given from the electric field intensity detecting means 51, and a variable amplifier based on this control voltage. 26 and 27 and the gain of the variable amplifier 34 are controlled.

  For example, as described later, the color level is controlled according to (in proportion to) the received electric field strength (step ST4), and then the luminance level is controlled according to the received electric field strength (step ST5). . Referring to FIG. 3, FIG. 3 is a diagram showing the relationship between the AGC voltage and the received electric field strength, and the AGC voltage is a constant value until the received electric field strength is the first level (fourth threshold) L1, When the received electric field intensity becomes stronger than the first level L1, the AGC voltage decreases. The arithmetic processing unit 41 reduces the gain by reducing the amplification factor of the variable amplifier 34 when the received electric field strength is the first level L1 (low sound). When the received electric field intensity reaches the second level (first threshold) L2, the amplification factor of the variable amplifier 34 is increased to increase the volume (sound volume: the second level L2 is equal to the above-described electric field intensity threshold value. Corresponding).

  That is, the arithmetic processing unit 41 controls the amplification factor of the variable amplifier 34 to change the volume of the received electric field intensity from the small level to the large level between the first level L1 and the second level L2, and thereby the received electric field intensity. Is less than the first level L1, the amplification factor of the variable amplifier 34 is set to zero and the sound is silenced (the arithmetic processing unit 41 changes the volume steplessly between the first level L1 and the second level L2). Will be.)

  In the example shown in FIG. 3, a third level (third threshold value) L3 and a fourth level (second threshold value) L4 are defined between the first level L1 and the second level L2. (L2> L4> L3> L1), the Y signal is level-controlled between the first level L1 and the fourth level L4, and the C signal is level-controlled between the third level L3 and the second level L2. Is done.

  The arithmetic processing unit 41 reduces the gain by reducing the amplification factor of the variable amplifier 26 when the received electric field intensity is the first level L1 (low brightness). When the received electric field strength reaches the fourth level L4, the amplification factor of the variable amplifier 26 is increased to increase the luminance (high luminance). That is, the arithmetic processing unit 41 controls the amplification factor of the variable amplifier 26 to change the luminance from small to large between the first level L1 and the fourth level L4 so that the received electric field strength changes. Is less than the first level L1, the gain of the variable amplifier 26 is set to zero and the luminance state is set to be zero (the arithmetic processing unit 41 changes the luminance steplessly between the first level L1 and the fourth level L4. Will be allowed).

  Similarly, the arithmetic processing unit 41 reduces the gain of the variable amplifier 27 when the received electric field intensity is the third level L3, and makes the color light (color light). When the received electric field strength reaches the second level L2, the gain of the variable amplifier 27 is increased to darken the color (color darkness). That is, the arithmetic processing unit 41 controls the amplification factor of the variable amplifier 27 to change the color of the received electric field intensity from the light level to the dark state between the third level L3 and the second level L2, and to receive the signal. When the electric field strength is less than the third level L3, the amplification factor of the variable amplifier 27 is set to zero and the state is muted (the processing unit 41 is stepless between the third level L3 and the second level L2). Will change the color automatically).

  Therefore, between the first level L1 and the third level L3, the monitor screen is in a colorless state, but the luminance is present, and the monitor screen is in a monochrome (monochrome) state. That is, as the received electric field strength decreases from the second level L2 to the first level L1, the volume gradually decreases, and the monitor screen gradually decreases in color (color), so that the fourth level. When the received electric field intensity is lower than L4, the monitor screen becomes gradually darker, and after the third level L3, the monitor screen becomes monochrome and gradually becomes darker. When the received electric field intensity is lower than the first level L1, the monitor screen becomes dark and becomes silent (muted).

  In this way, the monitor screen and sound are changed steplessly according to the received electric field strength, and the monitor screen is gradually made lighter in color while lowering the brightness to make it monochrome, and then the monitor screen is put into a dark state. Since the volume is changed in synchronization with the change in the screen, the monitor screen does not suddenly go into the snow noise state, and the user is informed that the reception state is getting worse, reducing the discomfort given to the user. There is an effect that can be done.

  In the above-described example, the analog television receiver that receives a terrestrial analog television broadcast signal has been described. However, the above-described soft mute can be similarly applied to a digital television receiver that receives a terrestrial digital television broadcast.

  4 is a block diagram illustrating an example of the digital television receiver 60. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 4, the digital television receiver 60 includes a digital signal processing unit 61, which is connected to the tuner unit 12 and also has a YC separator 23 and an attenuator 33 via a back-end unit 62. It is connected to the. Further, the control unit shown in FIG. 4 has a function different from that of the control unit 15 shown in FIG. 1, and therefore, the reference numeral 18 is given here, and the arithmetic processing unit and the storage means are indicated by reference numerals 18a and 18b, respectively.

  The digital signal processing unit 61 includes an analog-to-digital converter (ADC) 71, a quadrature detector 72, an FFT (Fast Fourier Transform) unit 73, a filter 74, an interleave unit 75, a demapping unit 76, a Viterbi decoding unit 77, and a TS (Transport) A stream) reproduction unit 78, and an RS (Reed Solomon) decoding unit 79. By the way, in digital terrestrial broadcasting, one digital broadcasting wave is transmitted from one broadcasting station (not shown), and this digital broadcasting wave is called a transport stream (TS).

  In digital terrestrial broadcasting, for example, an Orthogonal Frequency Division Multiplexing (OFDM) system is used.

  The analog signal (baseband signal) output from the tuner unit 12 is applied to the digital signal processing unit 61, first converted into a digital signal by the ADC 71 (discretized), and then subjected to quadrature detection by the quadrature detector 72. . The output of the quadrature detector 72 is supplied to the FFT circuit 73, where FFT is performed to convert the time domain signal into the frequency domain signal. This frequency domain signal is given to an interleaving unit 75 via a filter (for example, a band filter) 74, interleaved there, and then de-mapped by a demapping unit 76.

  The output from the demapping unit 76 is Viterbi-decoded by the Viterbi decoder 77 and then given to the TS reproducing unit 78, where the TS is reproduced. Then, an RS decoding process is performed in the RS decoder 79, and a TS output is transmitted. Then, after the TS output is digital-analog converted by the back end unit 62, the video signal and the audio signal are separated, the video signal is supplied to the YC separator 23, and the audio signal is supplied to the attenuator 33.

  By the way, when FFT processing is performed in the FFT unit 73, a C / N ratio (carrier-to-noise ratio) is obtained, and this C / N ratio is given to the arithmetic processing unit 18a. Further, when the Viterbi decoding unit 77 performs Viterbi decoding processing, error correction is performed, but the number of error corrections (bit error rate (BER)) corrected by the Viterbi decoding unit 77 is the arithmetic processing unit. 18a, the arithmetic processing unit 18a refers to the electric field strength-control voltage table stored in the storage means 18b based on the received electric field strength, the C / N ratio, and the BER as described later. The amplification factors of the variable amplifiers 26 and 27 and the variable amplifier 34 are controlled by the control voltage.

  The C / N ratio described above has a proportional relationship that increases as the received electric field strength increases and decreases as the received electric field strength decreases. On the other hand, the error bit rate (BER) suddenly decreases the number of error corrections when the received electric field strength increases and exceeds a predetermined level. That is, the C / N ratio and the BER are correlated with the received electric field strength.

  In the illustrated digital television receiver 60, the relationship between the BER and the received electric field strength is measured in advance and stored in the storage means 18b as a BER-received electric field strength table, and the C / N ratio and the received electric field strength are determined. Is stored in the storage unit 18b as a C / N ratio-reception field strength table.

  Referring to FIG. 4, when one channel (Ch) of terrestrial digital broadcasting is received, the received electric field strength detected according to the AGC voltage by electric field strength detecting means 51 is input to arithmetic processing unit 18a as described above. The C / N ratio is given from the FFT unit 73 to the arithmetic processing unit 18a. Furthermore, the BER is given from the Viterbi decoding unit 77 to the arithmetic processing unit 18a. In the arithmetic processing unit 18a, the storage means 18b is accessed based on the BER and the C / N ratio, and the BER and the C / N ratio are respectively referred to by referring to the BER-reception field strength table and the C / N ratio-reception field strength table. Read the corresponding field strength.

  In the following description, the received field strength given from the field strength detecting means 51 is the first field strength D1, and the field strengths corresponding to the BER and C / N ratio are the second and third field strengths D2 and D2, respectively. Call it D3.

  Subsequently, the arithmetic processing unit 18a multiplies the first to third electric field strengths D1, D2, and D3 by weighting factors k1 to k3 to obtain f (x) = k1 × D1 + k2 × D2 + k3 × D3. Electric field strength. The arithmetic processing unit 18a obtains a control voltage corresponding to the calculated electric field strength with reference to the received electric field strength-control voltage table described with reference to FIG. 1, and the variable amplifiers 26 and 27 and the variable amplifier 34 are controlled by this control voltage. Control the gain. Note that the monitor screen and volume control by soft mute performed here is the same as the soft mute described in FIG.

  In the above example, the BER and C / N ratio are also detected, and the received field strength detected by the field strength detecting means 51 according to the AGC voltage and the field strength corresponding to the BER and C / N ratio are represented by BER-received field. Obtained from the intensity table and the C / N ratio-received electric field intensity table, weighted, determined the calculated electric field intensity, and controlled the variable amplifiers 26 and 27 and the variable amplifier 34 with the control voltage corresponding to the calculated electric field intensity. However, the electric field intensity corresponding to the BER may be obtained from the BER-reception electric field intensity table using only the BER, and the control voltage may be obtained as the calculated electric field intensity.

  Also, the control voltage can be obtained by obtaining the electric field strength corresponding to the C / N ratio from the C / N ratio-reception electric field strength table using only the C / N ratio and calculating the electric field strength. The control voltage may be obtained using only the received electric field strength obtained from the electric field strength detecting means 51. However, depending on the received electric field strength obtained from the electric field strength detecting means 51, the BER, and the C / N ratio. If the calculated electric field strength is obtained and the control voltage is obtained, the variable amplifiers 26 and 27 and the variable amplifier 34 can be accurately controlled. Further, the first to third electric field strengths D1, D2, and D3 may be averaged without using the weighting factors k1 to k3, and the control voltage may be obtained using the result as the calculated electric field strength.

  As is clear from the above description, in FIGS. 1 and 4, the attenuator 24 and the variable amplifier 26 function as first adjusting means, and the attenuator 25 and the variable amplifier 27 function as second adjusting means. Further, the attenuator 33 and the variable amplifier 34 function as third adjusting means.

  As described above, according to the first embodiment, when a television broadcast signal having a video signal and an audio signal is received and audio corresponding to the video signal and the audio signal is output, the reception electric field strength is increased. Accordingly, the level of each of the luminance signal, color signal, and audio signal is reduced as the received electric field strength decreases, so it is possible to prevent a situation where the video is suddenly cut off and the video is blocked in advance by the user. It is possible to reduce discomfort given to the user in advance of the fact that it will be done.

  According to the first embodiment, when the received electric field intensity reaches the second level L2, the reduction of the color signal level is started, and the received electric field intensity becomes the fourth level smaller than the second level L2. The reduction of the level of the luminance signal is started, and when the received electric field strength becomes a third level smaller than the fourth level, the color signal is muted, and the first received electric field strength is smaller than the third level. The luminance signal is muted when the level reaches the level. At this time, when the received electric field strength reaches the second level, the reduction of the level of the audio signal is started, and when the received electric field strength reaches the first level, the audio signal is muted. Therefore, the monitor screen and the volume gradually change for the user according to the timing of the level control of the color signal, the luminance signal, and the audio signal, so that the video and the image can be displayed without causing discomfort. It is possible to perform the amount of the mute control.

  According to the first embodiment, when the television broadcast signal is a digital television broadcast signal, the reception state is determined in consideration of the BER and the C / N ratio in addition to the reception electric field strength. Accordingly, the mute control of the luminance signal, the color signal, and the audio signal is performed, so that the mute control can be performed with high accuracy.

It is a block diagram which shows the structure of the analog television receiver which is an example of the television receiver by Embodiment 1 of this invention. 3 is a flowchart for explaining soft mute control in the analog television receiver shown in FIG. 1. It is a figure which shows the luminance level control in the Funalog television receiver shown in FIG. 1, color level control, and sound level control in relation to an electric field strength. It is a block diagram which shows the structure of the digital television receiver which is another example of the television receiver by Embodiment 1 of this invention.

Explanation of symbols

10, 60 TV receiver, 11 antenna, 12 tuner unit, 13 video detection amplification unit, 14 audio detection amplification unit, 15, 18 control unit, 16 RGB demodulation circuit, 17 audio demodulation circuit, 18a, 41 arithmetic processing unit, 18b , 42 Storage means, 21 Surface acoustic wave filter for video (video SAWFIL), 22 Video detector, 23 YC separator, 24, 25, 33 Attenuator (attenuator), 26, 27, 34 Variable amplifier, 31 Audio SAWFIL, 32 audio detectors, 51 electric field intensity detection means, 61 digital signal processing unit, 62 back end unit, 71 analog-digital converter (ADC), 72 quadrature detector, 73 FFT (Fast Fourier Transform) unit, 74 filter, 75 interleave Part, 76 demapping part, 77 Viterbi decoding part, 78 T (Transport Stream) reproduction unit, 79 RS (Reed-Solomon) decoder.

Claims (8)

In a television receiver for receiving a video signal including a luminance signal and a color signal and a television broadcast signal having an audio signal and outputting a video corresponding to the video signal and an audio corresponding to the audio signal,
First adjusting means for controlling the level of the luminance signal;
Second adjusting means for controlling the level of the color signal;
Third adjusting means for controlling the level of the audio signal;
Detecting means for detecting a reception state of the television broadcast signal;
A table representing a relationship between a control level and the reception state in the first adjustment means to the third adjustment means;
A television receiver comprising: control means for controlling the first adjustment means to the third adjustment means on the basis of the reception state output from the detection means and the table.   2. The television receiver according to claim 1, wherein the control means controls the second adjustment means to reduce the level of the color signal when the reception state output from the detection means reaches a first threshold value defined in advance.   3. The television receiver according to claim 2, wherein the control means controls the first adjustment means to reduce the level of the luminance signal when the reception state output from the detection means becomes a second threshold value smaller than the first threshold value. apparatus.   4. The television receiver according to claim 3, wherein the control means controls the second adjustment means to mute the color signal when the reception state output from the detection means becomes a third threshold value smaller than the second threshold value.   5. The television receiver according to claim 4, wherein the control means controls the first adjustment means to mute the luminance signal when the reception state output from the detection means becomes a fourth threshold value smaller than the third threshold value.   The control means controls the third adjusting means to reduce the level of the audio signal when the reception state output from the detection means becomes the first threshold value, and mutes the audio signal when the reception state becomes the fourth threshold value. 6. The television receiver according to claim 5, which is configured as described above.   The television receiver according to any one of claims 1 to 6, wherein the detecting means detects the reception state of the television broadcast signal as the reception electric field strength of the television broadcast signal. The TV broadcast signal is a digital TV broadcast signal,
The detecting means detects the reception state of the television broadcast signal as the reception electric field strength of the television broadcast signal, and the control means is the received electric field strength, the bit error rate obtained when demodulating the digital broadcast signal, and the carrier wave of the digital broadcast signal The television receiver according to any one of claims 1 to 6, wherein a reception state is determined in accordance with at least one of the noise-to-noise ratios.

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