JP2005057371A - Television receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a television receiver capable of switching the signal to the signal of another medium when a digital television broadcast program cannot excellently be received during its reception and switching reception to the reception of the original digital television broadcast program when the reception state is restored to an excellent state. <P>SOLUTION: The television receiver for externally outputting a digital television broadcast signal subjected to reception processing is provided with a detection circuit for detecting the reception state of the digital television broadcast signal, switches an output signal from a source for outputting the signal of a different medium from the digital television broadcast signal in place of the broadcast signal, and provides an output when the detection circuit detects that the screen image of the digital television broadcast program is frozen because the reception state of the digital television broadcast signal is deteriorated while the television receiver outputs the broadcast signal. The detection circuit discriminates a reception state on the basis of the change amount of an output signal from an AGC circuit and the error amount of a demodulated demodulation signal or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a television receiver that receives a digital television broadcast signal, and more particularly, when an electric field strength deteriorates during reception of a digital television broadcast, the video freezes, or audio is interrupted. It is related with the method of switching to.
[0002]
[Prior art]
In a television receiver that receives a digital television broadcast wave, when the electric field strength is low based on the output of the AGC detector circuit so that the input to the A / D converter circuit is always constant even if the reception state changes. An AGC control signal is output and feedback is applied so as to increase the amplification gain of the intermediate frequency amplifier circuit and to decrease the amplification gain when the electric field strength is high. In addition, an error correction circuit is provided after the decoding circuit to detect and correct errors in received data. As a result, even if the electric field strength is somewhat deteriorated, good image quality and sound can be obtained without degradation of image quality as in analog television.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-261731 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-138874
[Problems to be solved by the invention]
However, in a mobile body, for example, a vehicle-mounted television receiver, the reception state of radio waves is large and rapidly changes, particularly in mountainous areas and tunnels, as the vehicle travels. If reception continues in such a state, even if an AGC circuit or an error correction circuit is provided, error correction of received data cannot be performed, and the image is frequently fixed and does not move (freeze). Or the sound is interrupted. As a result, the user is uncomfortable.
[0005]
The present invention has been made in view of the above points, and switches to another input source when reception becomes impossible during reception of digital television broadcasts, and when the reception state returns to a good state, the original digital television broadcasts are restored. It is an object to provide a television receiver that can be switched to reception.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a television receiver, which is mounted on a mobile body, includes receiving means for receiving and processing a digital television broadcast signal, and outputs the received broadcast signal to the outside. The reception state detection means for detecting the reception state of the broadcast signal, and the reception state detection means during the output of the broadcast signal has deteriorated the reception state of the digital TV broadcast signal, and the screen of the digital TV broadcast is in a freeze state And switching means for switching from the broadcast signal to an output signal from a source source that outputs a media signal different from that of the digital television broadcast when the signal is detected.
[0007]
The receiving means amplifies the digital television broadcast signal converted to an intermediate frequency, and an intermediate frequency amplifier circuit for maintaining a constant level of a signal output from the intermediate frequency amplifier circuit. An AGC detection circuit for outputting an AGC control signal, wherein the reception state detection means is configured to transmit the digital television broadcast based on a signal level change amount of an AGC control signal output from the AGC detection circuit to the intermediate frequency amplifier circuit. It is characterized by detecting the reception state of a signal.
[0008]
The reception means includes a synchronization detection circuit that detects a synchronization signal from the received digital television broadcast signal, and the reception state detection means detects a peak value of a synchronization pulse in the reception signal in the synchronization detection circuit. The reception state of the digital television broadcast signal is detected based on the amount.
[0009]
The receiving means includes a demodulating circuit for performing fast Fourier transform and demodulating the digital television broadcast signal, and an error correcting circuit for detecting and correcting an error of the signal demodulated in the demodulating circuit, and the receiving state detecting means Is characterized in that the reception state of the digital television broadcast signal is detected based on the error amount of the reception signal in the error detection circuit.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A television receiver according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a television receiver according to an embodiment of the present invention. FIG. 2 is a flowchart of the switching process performed by the control unit 2 of the television receiver according to the embodiment of the present invention.
[0011]
Reference numeral 1 denotes a digital television broadcast receiver that receives digital television broadcast waves. A tuner unit 11 selectively receives a high-frequency broadcast wave of the designated channel. An intermediate frequency amplifier circuit 12 amplifies the received signal converted to the intermediate frequency based on the output of the AGC detection circuit 13. Reference numeral 13 denotes an AGC (automatic gain amplifier) that converts the intermediate frequency signal into a digital signal by an A / D conversion circuit and applies feedback to the input signal (intermediate frequency amplification circuit 12) based on the detection signal in order to keep the reception level constant. Control) In the detection circuit, the lower the reception level, the higher the signal level of the AGC control signal is output. A synchronization detection circuit 14 detects a synchronization signal from received data. Reference numeral 15 denotes a demodulation circuit that performs fast Fourier transform on received data and demodulates the received data. An error correction circuit 16 detects and corrects an error in the demodulated signal. Reference numeral 17 denotes a signal processing unit that separates a video signal and an audio signal that have been compression-encoded according to the MPEG system, and decompresses and decodes the original video signal and audio signal to the switching circuit 20 respectively. . Reference numeral 18 denotes a liquid crystal display unit for displaying received television images. Reference numeral 19 denotes an audio output unit that amplifies the received television / radio audio signal or audio signal reproduced by a CD player and outputs the amplified signal to a speaker.
[0012]
Reference numeral 2 denotes a control unit constituted by a microcomputer that instructs the switching circuit 20 to switch based on the detection results of the detection circuits 21, 22, and 23 that detect (determine) the reception state. The control unit 2 has a memory for storing ON / OFF of switching setting and switching control data input from the operation unit 24, and the input is switched depending on the contents of this memory. Further, it detects the state of external input and outputs a message to the liquid crystal display unit 18 and the audio output unit 19. Reference numeral 20 denotes a switching circuit that switches between an output signal of the digital television receiver 1 and an input signal from another input source 3. A change amount detection circuit 21 detects a change amount (time change amount) of the signal level of the AGC control signal, which is an output from the AGC detection circuit 13, and detects a sudden change in the reception state. Reference numeral 22 denotes a peak amount detection circuit that detects the peak value of the synchronization pulse, which is the output of the synchronization detection circuit 14, and is related to image disturbance and screen stability. An error amount detection circuit 23 detects an error amount (rate) in the error correction circuit 16. An operation unit 24 is used by the user to select another input source 3 and to switch between a digital television signal and another input source 3.
[0013]
Reference numeral 3 denotes a source source (another input source) that outputs a signal of a media different from that of the digital television broadcast connected to the television receiver, an analog television receiver that receives an analog television broadcast wave, and an AM / FM broadcast wave A radio receiver, a CD player that reproduces music information recorded on a CD (compact disc), an MD player that reproduces music information recorded on an MD (mini disc), and the like. The outputs of these input sources 3 are connected to the liquid crystal display unit 18 and the audio output unit 19 via the switching circuit 20.
[0014]
Next, switching processing performed by the control unit 2 will be described. This process starts from the time when the television receiver is turned on.
[0015]
In step S11, a digital television broadcast is received, and the process proceeds to step S12. That is, the received video information is output to the liquid crystal display unit 18 and the audio information is output to the audio output unit 19.
[0016]
In step S12, it is determined whether or not the amount of change in the signal level of the AGC control signal is greater than or equal to the set value. If the amount of change is greater than or equal to the set value, the process proceeds to step S13. Continue receiving TV broadcasts. In a television receiver mounted on a vehicle, the reception state changes greatly with the traveling environment such as plains, mountainous areas, and tunnels. Therefore, an AGC control signal is output based on the output of the AGC detection circuit 13, and feedback is applied to increase the amplification gain of the intermediate frequency amplifier circuit 12, so that the input to the A / D conversion circuit is always constant. ing. The AGC control signal is output so as to be high when the reception state is deteriorated and low when the reception state is recovered. By using this, the amount of change in the AGC signal level in the AGC detection circuit 13 is detected by the amount of change detection circuit 21. If the amount of change in the signal level of the AGC control signal is equal to or greater than the set value, the reception state is abruptly deteriorated. I can judge. The set value is set to the amount of change in signal level immediately before the digital television broadcast screen freezes (fixes). Alternatively, it may be the signal level when it is frozen. In this example, the state immediately before the freeze is determined to be the freeze state. However, when the freeze is in progress, it may be determined that the freeze state is established and the medium may be switched to another medium.
[0017]
In step S13, it is determined whether or not the input source is set to be switched by the user. If the switching is set, the process proceeds to step S14. If the switching is not set, the process returns to step S11. This is determined based on the user's setting operation.
[0018]
In step S14, it is determined whether or not the input source 3 can be switched, and if it is switched, the process proceeds to step S15, and if not switched, the process waits. In other words, the analog TV receiver as another input source 3 can receive analog TV broadcast waves satisfactorily (for example, the reception level of the carrier wave is a predetermined value or more), or the radio receiver is AM / FM. It is determined from the reception status of each device and the playback preparation status whether the broadcast wave can be received satisfactorily or whether a disc is inserted into the CD player or MD player and playback is possible.
[0019]
In step S15, it switches to the other input source 3, and moves to step S16. That is, since the reception state of the digital television broadcast is not good, the input source 3 is switched to another input source 3 according to an alternative order (priority order) set in advance by the user. For example, if the reception state and the playback preparation state are prepared in the order of analog television, radio, CD player, and MD player, the input source is switched. When switching, a message (display) indicating that the reception state of the digital television is deteriorated and an input source (for example, an analog television) are displayed on the screen (liquid crystal display unit 18) in advance. May be. This display can eliminate the uncomfortable feeling caused by the user switching.
[0020]
In step S16, it is determined whether or not the amount of change in the signal level of the AGC control signal is greater than or equal to a set value. If the amount of change is greater than or equal to the set value, reception of another input source 3 or reproduction of another input source 3 is performed. If the change amount is not greater than the set value, the switching circuit 20 is instructed to return to step S11 and receive the digital television broadcast. In this determination, for example, a change amount of the signal level of the AGC control signal in the AGC detection circuit 13 is detected by the change amount detection circuit 21, and it is determined that the reception state has been improved unless the change amount of the AGC level is equal to or greater than a set value. If the reception state of the digital television receiver 1 is improved by this step, it is possible to immediately return to the reception of the digital television broadcast.
[0021]
In addition, even if the amount of change in the AGC signal level becomes less than the set value in a state in which the reception state deteriorates and switching from the reception of the digital television broadcast to the CD performance or the MD performance (even if the reception state is improved), Instead of switching to digital television broadcast reception immediately, switching may be performed when the performance of the currently reproduced song is finished. In this way, the user does not feel discomfort that suddenly switches in the middle of a song during playback of a CD or MD. In addition, when switching is performed so as to fade out, the uncomfortable feeling is further reduced.
[0022]
As described above, according to the television receiver of the present embodiment, the amount of change in the AGC signal level before the reception state of the digital television broadcast receiver 1 deteriorates and the image freezes or the sound is interrupted. When the amount of change becomes equal to or greater than the set value, switching to another input source 3 can reduce the sense of discomfort felt by the user. Further, when the reception state is improved, it is possible to return to receiving the original digital television broadcast immediately.
[0023]
In this example, it is determined that the amount of change in the AGC signal level is equal to or greater than the set value and it is determined that the reception state of the digital television broadcast wave has deteriorated. Instead of S16, it may be switched to another input source 3 by detecting that the reception state has deteriorated by another method.
[0024]
For example, when the detected amount of the peak value of the synchronization code in the received data is low, the video synchronization is disturbed and the display screen is not stable. Therefore, the peak value of the synchronization code in the synchronization detector 14 is detected by the peak amount detection circuit 22, and it is determined that the reception state of the digital television broadcast wave has deteriorated by detecting that the detection amount has decreased below the set value. Thus, it may be switched to another input source 3.
[0025]
Further, when the error amount (rate) of received data increases, a normal image cannot be displayed. Therefore, the error amount detection circuit 23 detects the error amount in the error detection / correction circuit 17, detects that the detection value exceeds the set value, and determines that the reception state of the digital television broadcast wave has deteriorated. You may make it switch to the other input source 3. FIG.
[0026]
In addition, the reception status of the digital television broadcast wave is judged based on two or a combination of the detection results of the change amount detection circuit 21, the peak amount detection circuit 22, and the error amount detection circuit 23, and other inputs. You may make it switch to the source | sauce 3. FIG.
[0027]
In addition, although the vehicle-mounted thing was applied as a mobile body, PDA (mobile body terminal) may be sufficient.
[0028]
【The invention's effect】
As described above, according to the present invention, when the reception is not good during the reception of the digital television broadcast, it is switched to another input source, and when the reception state returns to the good state, the reception is switched to the reception of the original digital television broadcast. Can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a television receiver according to an embodiment of the present invention.
FIG. 2 is a flowchart of switching processing performed by the control unit 2 of the television receiver according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Digital television broadcast receiving part 11 ... Tuner 12 ... Intermediate frequency amplifier circuit 13 ... AGC detection circuit 14 ... Synchronization detection circuit 15 ... Demodulation circuit 16 ... Error correction circuit 17 ... Signal processing unit 18 ... Liquid crystal display unit 19 ... Audio output unit 2 ... Control unit 20 ... Switch circuit 21 ... Change amount detection circuit 22 ... Peak amount detection circuit 23 ... Error amount detection circuit 24 ... Operation unit 3 ... Other input sources

Claims (4)

In a television receiver that is mounted on a mobile body and includes receiving means for receiving and processing a digital television broadcast signal, and outputting the received broadcast signal to the outside,
Receiving state detecting means for detecting a receiving state of the digital television broadcast signal;
When the reception state detecting means detects that the reception state of the digital television broadcast signal has deteriorated and the screen of the digital television broadcast is in a frozen state during the output of the broadcast signal, the digital television broadcast is detected from the broadcast signal. A television receiver comprising switching means for switching to an output signal from a source source that outputs a signal of a different media and outputting the signal to the outside. The receiving means amplifies the digital television broadcast signal converted to the intermediate frequency, and performs AGC control on the intermediate frequency amplifier circuit in order to keep the level of the signal output from the intermediate frequency amplifier circuit constant. An AGC detection circuit that outputs a signal,
The reception state detecting means includes
2. The television receiver according to claim 1, wherein a reception state of the digital television broadcast signal is detected based on a change amount of a signal level of an AGC control signal output from the AGC detection circuit to the intermediate frequency amplifier circuit. . The receiving means includes a synchronization detection circuit that detects a synchronization signal from the received digital television broadcast signal,
The reception state detecting means includes
2. The television receiver according to claim 1, wherein a reception state of the digital television broadcast signal is detected based on a detection amount of a peak value of a synchronization pulse in the reception signal in the synchronization detection circuit. The receiving means includes a demodulating circuit for performing a fast Fourier transform and demodulating a digital television broadcast signal, and an error correcting circuit for detecting and correcting an error of the signal demodulated in the demodulating circuit,
The reception state detecting means includes
2. The television receiver according to claim 1, wherein a reception state of the digital television broadcast signal is detected based on an error amount of the reception signal in the error detection circuit.

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