JP2792451B2 - Satellite broadcast receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiving apparatus.

[0002]

2. Description of the Related Art A satellite broadcast receiving apparatus has a function of 36,0 above the equator.
From a broadcasting satellite in a geostationary orbit of 00 km, the Ku band (12
This is a device that receives broadcast radio waves transmitted in the (GHz band) and reproduces audio signals and video signals from the broadcast radio waves, and is now generally widely used with the practical use of satellite broadcasts.

[0003] Broadcast radio waves used in satellite broadcasting are:
Due to the restrictions on the transmission power of broadcasting satellites in geosynchronous orbit and restrictions due to long-range radio wave propagation accompanying geostationary altitude, the reception power becomes very weak, so the receiving antenna and BS-
IF converter (generally, the receiving antenna and the BS-IF converter are integrated in order to eliminate the loss due to the antenna line and to reduce noise, and both are called a satellite broadcasting receiving antenna. ) Has low noise / high gain (eg, noise figure: NF = 0.7 dB,
Antenna gain: G _r = 55 dB) is used, but depending on various reception conditions including rainfall and atmospheric conditions, and problems caused by the directional characteristics of the receiving antenna, etc.
The reception state of the satellite broadcast receiving device is greatly affected.

[0004] In general, when the receiving condition is completely deteriorated or when the receiving condition is not satisfied, for example,
If the antenna line of the broadcasting satellite receiving antenna is disconnected, if there is no satellite broadcasting, or if the broadcast radio wave is interrupted by any obstacle such as a flying object, the reception level will be reduced completely. However, the level of both the audio signal and the video signal is completely suppressed by the asynchronous suppression processing, etc., so that there is no problem. However, the problem in lowering the reception level is that the normal reception state and the complete reception as described above This is a transition state of the reception level while the level is suppressed. The reception level transition state is caused by, for example, a change in rainfall conditions. In this case, the reception state deteriorates due to a continuous or intermittent transition of the reception level, and the audio signal and the video signal are changed. The signal quality is degraded, and consequently the generation of noise and significant changes in the noise level cause discomfort to the viewer.

[0005] As a method for solving such a problem, a conventional example of an apparatus (referred to as a first conventional example) disclosed in Japanese Patent Application Laid-Open No. 64-44691 (Japanese Patent Application No. 62-22085) is known. AGC in the satellite broadcasting receiver
Based on the output voltage of the circuit and the like, the reception level is compared with a reference level necessary for a normal audio signal and a video signal, and if the reception level is determined to be lower than the reference level, the audio signal and the video The output level of the signal is controlled so that the generation of noise does not cause discomfort to the viewer. Also, 'TV technology'
In another device example (referred to as a second conventional example) disclosed in the November 1990 issue, a reception output after FM demodulation is detected through a high-band amplifier (9 MHz BPF) to detect a high-frequency noise component included in the reception signal. , C when receiving broadcast waves
/ N ratio (abbreviation of signal-to-noise ratio: Carr-ier to Noise Ratio) is detected, and the level of the audio signal and the video signal is controlled based on the result.

Hereinafter, the first and second conventional examples will be described with reference to the drawings. FIG. 3 is a block diagram showing a configuration of a first conventional example.
No. 44691 (Japanese Patent Application No. 62-202085)
1 is an example of an apparatus related to the proposal of the present invention. This conventional example is shown in FIG.
, A BPF 31 connected to a broadcast satellite receiving antenna (not shown), a mixer 32, and a PLL
Detection circuit 33, AGC circuit 34, FM demodulation circuit 35
And a local oscillation circuit 36.

In FIG. 3, an intermediate frequency signal 101 transmitted from a broadcasting satellite receiving antenna is 1.0 to 1.3 G.
A local oscillator circuit which is input to a mixer 32 through a BPF 31 for extracting a signal of 1 Hz and is frequency-controlled by a detection output of a PLL detection circuit 33 provided so as to tune with a desired channel of BS-1 to 15 channels (channels). 3
6 is mixed with the oscillation output of
An intermediate frequency signal is extracted, and the second intermediate frequency signal is AG
The voltage is input to the C circuit 34, and the voltage level is maintained at a predetermined level and output. The second intermediate frequency signal having a stabilized voltage level output from the AGC circuit 34 is input to an FM demodulation circuit 35, FM-demodulated and output as a demodulated output signal, and a predetermined output suppressing circuit (shown in the figure). Is not performed), the output suppression control signal 104
Is sent as In this case, when the received signal is at a low level and the level of the second intermediate frequency signal output from the AGC circuit 34 is lower than a predetermined level, the output levels of the audio signal and the video signal are reduced to the output suppression level. In a circuit (not shown), suppression is controlled by an output suppression control signal 104.

FIG. 4 is a block diagram showing the configuration of another second conventional example.
This is another example of the device found in the "Monthly". This conventional example uses a BPF connected to a broadcast satellite receiving antenna (not shown).
41 and 49, a mixer 42, and a PLL detection circuit 43
AGC circuit 44, FM demodulation circuit 45, local oscillation circuit 46, level adjustment circuit 47, amplification circuit 48,
It comprises a C / N detection circuit 50 and a gain adjustment circuit 51. 3 in that a level adjustment circuit 47, an amplification circuit 48, a BPF 49, a C / N detection circuit 50 and a gain adjustment circuit 51 are newly added, and a BPF 41, a mixer 42, The operations of the PLL detection circuit 43, the AGC circuit 44, the FM demodulation circuit 45, and the local oscillation circuit 46 are the same as those in the above-described conventional example. In FIG. 4, the demodulation output of the FM demodulation circuit 45 has an appropriate demodulation output level via the level adjustment circuit 47 and the amplification circuit 48 in accordance with the reception environment such as the performance of the satellite reception antenna and the installation location of the reception device. Is adjusted to a suitable signal level. The output of the amplifying circuit 48 passes through a BPF 49 having a frequency bandwidth corresponding to a frequency region of about 9 MHz, that is, a frequency region not including an audio signal and a video signal. It is extracted and output. The extracted noise output is C /
The signal is input to the N detection circuit 50, the level is controlled by the gain control circuit 51, an appropriate noise level is set, and the signal is sent out as an output suppression control signal 104 to a predetermined output suppression circuit (not shown). The output suppression control signal 104 controls the signal output including the audio signal and the video signal when the noise signal level included in the received signal does not exceed a predetermined allowable amount in the output suppression circuit. Control signal.

In the above-mentioned conventional satellite broadcast receiving apparatus, the means for generating an output suppression control signal for suppressing and controlling the signal output including the audio signal and the video signal according to the reception environment is provided in the first conventional example. Detects the carrier wave level at the time of receiving the broadcast wave and generates the output suppression control signal,
In the second conventional example, an output suppression control signal is generated by detecting a noise level. Regarding these conventional examples, for example, as introduced in “Radio technology JULY'88”, in the case of satellite broadcasting, the S / N ratio of the video signal of the receiver is determined by the broadcast received by the parabolic antenna. The fact that it is determined by the C / N ratio of the radio wave is used. Above "Radio technology JULY'88 pp.124-126"
In the example described in (1), when the image quality is not less than “3” according to the five-level evaluation method, that is, when the C / N is around 7 dB, the interference due to the noise level is large. The audio signal and the video signal are suppressed by the result of detecting the C / N.

[0010]

In the above-mentioned conventional satellite broadcast receiving apparatus, the aforementioned "radio technology JULY'88, p.
p.124 ”, the reception C /
When the N ratio decreases, the S / N ratio of the video signal rapidly decreases nonlinearly from a certain level. Also, since the reception C / N ratio is affected by the type of antenna to be received (antenna gain and noise figure (NF), etc.) and the reception status (whether or not there is a failure in the radio wave propagation path and the reception location, etc.), the reception C / N ratio may vary Optimum receiving C / for suppressing signal and video signal
It is difficult to determine the N ratio. For this reason, there is a drawback that a situation occurs in which "the signal is suppressed even though it is still sufficiently visible" or "the noise is severe and cannot be seen" depending on the reception environment.

In addition, the S / N ratio for the deterioration of the reception C / N ratio
There is a problem due to the correlation between the ratio and the increase in the error rate in the voice PCM signal. That is, when the reception C / N ratio is deteriorated, an error is likely to occur in the audio PCM signal. However, unlike the video signal, the BCH (Bose-C
Haudhuri-Hocuenghem) code has a function to correct a single error by itself (IEICE A Vol.J
73-A NO.2 pp.196-202,203-208,1990.2).
However, when the level of the reception C / N ratio decreases and the double error increases, the error can be detected but the error cannot be corrected. However, if the error situation further worsens (continuous double error occurs), it becomes impossible to reproduce sound normally and noise occurs. The noise signal at this time is different from the noise of white noise system such as "shear" or "zar" in the terrestrial wave at low C / N ratio, and is generated randomly from the minimum value to the maximum value of the audio signal level. It sounds like a very unpleasant noise like "crisp".

Although the probability of occurrence of a double error in such a voice PCM signal is proportional to the reception C / N ratio, as shown in Japanese Patent Application No. 4-004385, it is analog and digital. Therefore, the above-mentioned proportional relationship between the S / N ratio of the video signal and the reception C / N ratio cannot be correlated. That is, in the first and second conventional examples described above, "the image output looks normal but the audio output is noisy and the audio output is suppressed at random." A situation has arisen in which "the image is disturbed by noise and cannot be seen, but the audio output is normally output although the noise is included." In particular, this situation occurs around reception C / N = 7 dB, and imbalance occurs in the image / audio reproduction capability of the receiver. This is more conspicuous than in the case of terrestrial broadcasting in which both the image and the sound are of the same analog type in the past, and even in the above-mentioned first and second conventional examples of the satellite broadcasting. Viterbi decoding with a low carrier level and a strong error correction capability at a low C / N ratio (see IEICE Journal Vol.J73-A NO.2 pp.218-224,1990.2) In the used communication / broadcasting, etc., there is a drawback that the above problem occurs more remarkably.

The present invention is directed to the first and second embodiments shown above.
It is an object of the present invention to provide a satellite broadcast receiving apparatus capable of effectively suppressing low C / N ratio noise by solving the problem in the conventional example.

[0014]

According to the present invention, there is provided a satellite broadcast receiving apparatus comprising: a receiving demodulation section for inputting an intermediate frequency signal output from an antenna for receiving a satellite broadcasting wave and performing FM demodulation; A video signal processing unit that inputs the FM demodulated signal to be extracted, extracts and outputs a video signal included in the FM demodulated signal, and an FM output from the reception demodulation unit.
A demodulated signal is input, a digital audio signal included in the FM demodulated signal is extracted, and the digital audio signal is QP
QPSK for SK demodulation to output first audio PCM signal
A demodulation unit, a reference timing generation unit that receives the first audio PCM signal, generates and outputs a frame reference timing signal of the first audio PCM signal, and receives the first audio PCM signal. , Through a signal processing on the first voice PCM signal, extracts and outputs a second voice PCM signal from which an error has been removed, and generates a double error signal associated with the first voice PCM signal. An audio signal processing unit for detecting and outputting a live signal ; and outputting the second audio PCM signal and the video signal based on the double error occurrence and the frame reference timing signal output from the audio signal processing unit. A suppression control unit that generates and outputs a signal suppression control signal for controlling the level, and inputs the second audio PCM signal and the video signal;
An output suppression circuit unit that suppresses the signal level of the second audio PCM signal and the video signal to a predetermined level and outputs the signal based on the frame reference timing signal and the signal suppression control signal.

[0015] Incidentally, the audio signal processing unit, a descramble circuit for descrambling the first audio PCM signal, to release the interleaving of the audio PCM signal output from the descramble circuit, a third speech PC
A deinterleave circuit for extracting and outputting an M signal, and a third audio PC output from the deinterleave circuit
Enter the M signal, the third and detects and outputs the dual error onset raw audio PCM signal, the error that generates and outputs the removed the dual error second audio PCM signal is configured to include a detection and correction circuit, said suppression system
A control circuit , based on the double error occurrence and the frame reference timing signal , a counter circuit that counts and outputs the number of error occurrences corresponding to the double error occurrence frequency,
When the count value of the number of error occurrences output from the counter circuit exceeds a predetermined count value,
A suppression timing control circuit that generates and outputs a pair of suppression control signals for suppressing and controlling the output levels of the second audio PCM signal and the video signal at predetermined time intervals, respectively; it may be <br/> so that is configured with a.

Further, the audio signal processing unit, a descramble circuit for descrambling the first audio PCM signal, to release the interleaving of the audio PCM signal output from the descrambling circuit, the third a deinterleaving circuit for extracting and outputting audio PCM signal, by inputting a third audio PCM signal output from the deinterleaving circuit detects double errors onset raw of the third audio PCM signal outputs, it is configured to include, and error detection and correction circuit that generates and outputs the removed the dual error second audio PCM signal, the suppression control unit, the dual error occurs and on the basis of the frame reference timing signal, a counter circuit configured to count the error occurrence count corresponding to the dual error occurrence frequency, said counter When the count value of the number of error occurrences output from the path exceeds a predetermined count value, the output level of the second audio PCM signal and the output level of the video signal are simultaneously suppressed. and suppression timing control circuit for generating and outputting a suppression control signal may be so that is configured to include a.

[0017]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. As shown in FIG. 1, the present embodiment is configured such that a BPF 1, a mixer 2, a PLL detection circuit 3, and a A are connected to a broadcast satellite reception antenna (not shown) to form a reception demodulation unit.
A GC circuit 4, an FM demodulation circuit 5, and a local oscillation circuit 6,
LPF 7 forming a video signal processing unit, deemphasis circuit 8, video amplification circuit 9, clamp circuit 10, video amplification circuit 11, BPF 12 forming a QPSK demodulation unit,
QPSK demodulation circuit 13 and differential conversion circuit 14, synchronous detection circuit 15 and timing circuit 16 forming a reference timing generation section, descrambling circuit 17, deinterleave circuit 18 forming an audio signal processing section, and error detection / correction The circuit 19 includes a circuit 19, a counter circuit 20 forming a suppression control section, a suppression timing control circuit 21, and an output suppression circuit 22 forming an output suppression circuit section. 2 (a), 2 (b) and 2 (c) show P
It is a figure showing the example of frame composition of a CM audio signal.

In FIG. 1, an intermediate frequency signal 101 transmitted from a broadcast satellite receiving antenna (not shown) is
The signal is input to the mixer 2 through a BPF 1 for extracting a signal of 1.0 to 1.3 GHz, and the frequency is controlled by a detection output of a PLL detection circuit 3 provided to tune with a desired channel in BS-1 to 15ch. The second intermediate frequency signal of 402.78 MHz is extracted and output by being mixed with the oscillation output of the local oscillation circuit 6, and is input to the AGC circuit 4 to maintain the voltage level of the second intermediate frequency signal at a predetermined level. It is output in the state where it was done. The second intermediate frequency signal output from the AGC circuit 4 and having a stabilized voltage level is input to an FM demodulation circuit 5 where it is FM-demodulated and output, and is divided and input to an LPF 7 and a BPF 12. The LPF 7 is an LPF having a frequency of 4.5 MHz.
The video signal included in the FM demodulated signal is extracted and output through the LPF 7 and input to the de-emphasis circuit 8. In the de-emphasis circuit 8, the emphasis applied when the broadcast signal is transmitted is released, and the output video signal is amplified by the video amplifier circuit 9 and input to the clamp circuit 10. Then, the video signal output from the clamp circuit 10 is input to the output suppression circuit 22.

On the other hand, the BPF 12 has a frequency of 5.7 MHz.
z BPF, and the BPF 12 extracts and outputs the QPSK audio signal included in the FM demodulated signal,
The signal is input to the QPSK demodulation circuit 13 and demodulated. QPS
The in-phase component I and quadrature component Q demodulated and output by the K demodulation circuit 13 are input to the differential conversion circuit 14 and converted into a 2.048 Mbit / S audio PCM signal, which is output. And descramble circuit 1
7 is input. The synchronization detection circuit 15 detects a frame synchronization signal of the audio PCM signal.
2A shows the frame structure of the 2.048 Mbit / S audio PCM signal. FIGS. 2A and 2B show the frame structure of frame 1 in the A mode and the B mode, respectively. , The synchronization detection circuit 15 detects the above-mentioned frame synchronization signal corresponding to each frame and inputs the same to the timing circuit 16. The timing circuit 16 receives the input of the frame synchronization signal, and generates and outputs a frame reference timing signal based on the timing of the frame synchronization signal. Is input to

On the other hand, the 2.048 Mbit / S audio PCM signal input to the descrambling circuit 17 is passed through the descrambling circuit 17 and the deinterleaving circuit 18 to the scramble and interleave added when the broadcast signal is transmitted. Is released and the output sound P
The CM signal is input to the error detection / correction circuit 19 and the output suppression circuit 22. The error detection / correction circuit 19 outputs the voice P
BCH (63,56) SEC used for CM signal
To detect double errors by utilizing the property of the (single error correction) · DED (double error detection) code, a circuit for outputting a double error flag to indicate <br/> the dual error onset raw Yes, the detected double error flag is input to the counter circuit 20. In the counter circuit 20, the number of times of occurrence of the error indicated by the double error flag is counted based on the frame reference timing signal sent from the above-mentioned timing circuit 16, and the count value is calculated by the suppression timing control circuit 2.
1 is input. When the count value exceeds a preset value, the suppression timing control circuit 21 outputs a suppression timing signal for suppressing the signal levels of the audio PCM signal and the video signal at predetermined time intervals, The signal is input to the output suppression circuit 22. In the output suppression circuit 22, the video signal output from the video amplification circuit 11, the frame reference timing signal output from the timing circuit 16, the audio PCM signal output from the deinterleave circuit 18, and the output from the suppression timing control circuit 21 The signal levels of the audio PCM signal and the video signal are individually suppressed at predetermined time intervals by the suppression timing signal according to the reception environment and the like, and the video The signal is output as a signal 102 and an audio signal 103.

In the above-described embodiment, the suppression control unit includes the counter circuit 20 and the suppression timing control circuit 2.
1, the suppression timing control circuit 21 outputs the suppression timing signal, and
A circuit is formed so as to suppress the signal levels of the signal and the video signal at predetermined time intervals. Another embodiment of the present invention is a suppression timing control circuit forming the suppression control unit. 21 is replaced with a suppression control circuit irrelevant to the timing control action, and the signal levels of the audio PCM signal and the video signal are simultaneously suppressed in the output suppression circuit 22 by the suppression control signal output from the suppression control circuit. It is also possible to form a circuit as described above and output the video signal 102 and the audio signal 103.

Generally, the S / N ratio of a video signal and the received C / N
There is a correlation between the ratio, the error occurrence frequency in the voice PCM signal, and the reception C / N ratio. However, at a low C / N ratio (= around 7 dB) when the reception situation starts to become unstable, both of them have a correlation. Is lost. For example, according to the aforementioned “Radio technology, JULY'88, pp.124”,
When C / N is 10 dB or more, 1 in C / N ratio
Although the S / N ratio of the video signal deteriorates by 1 dB with respect to the deterioration of dB, when the C / N ratio is 7 dB or less, C / N
The S / N ratio of the video signal is 10 with respect to the degradation of the ratio of 1 dB.
Degraded near dB. On the other hand, the frequency of error occurrence in a voice PCM signal depends on the error correction method. For example, it is known that the relationship between the C / N ratio and the frequency of error occurrence until frame synchronization is lost maintains a substantially constant relationship. Have been. As described above, if the processing result of two signals having no correlation is generally controlled by only one signal, it cannot be a completely optimal control method. However, when the C / N ratio is low, more stable characteristics are obtained. Is controlled by an audio PCM signal that holds the signal and the two signals are controlled in a fixed timing relationship, whereby more stable characteristics can be obtained compared to the conventional method. In the present invention,
In order to suppress the output of the video signal at a lower C / N ratio than before, it is necessary to take a countermeasure against the deterioration of the S / N ratio of the video signal. /Vol.37, p.57 "can be improved by adopting an adaptive video noise reduction circuit.

That is, according to the present invention, even when the output noise level of each of the audio signal and the video signal has no correlation, the C / N is about 7 dB in accordance with the reception environment.
Collectively output both the audio signal and the video signal
The effect that the control can be performed effectively and stably can be obtained.

[0025]

As described above, the present invention is applied to a broadcasting satellite receiving apparatus, and at the time of reception at a low C / N ratio, through a control action by an audio PCM signal that maintains stable characteristics. By controlling the two signal levels including the audio PCM signal and the video signal while maintaining a fixed timing relationship, there is an effect that the signal output of the audio signal and the video signal can be suppressed stably and in a well-balanced manner. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a frame configuration of an audio signal according to the embodiment.

FIG. 3 is a block diagram showing a first conventional example.

FIG. 4 is a block diagram showing a second conventional example.

[Explanation of symbols]

 1, 12, 31, 41, 49 BPF 2, 32, 42 Mixer 3, 33, 43 PLL detection circuit 4, 34, 44 AGC circuit 5, 35, 45 FM demodulation circuit 6, 36, 46 Local oscillation circuit 7 LPF 8 De-emphasis circuit 9, 11 Video amplification circuit 10 Clamp circuit 13 QPSK demodulation circuit 14 Differential conversion circuit 15 Synchronization detection circuit 16 Timing circuit 17 Descramble circuit 18 De-interleave circuit 19 Error detection / correction circuit 20 Counter circuit 21 Suppression timing control circuit Reference Signs List 22 output suppression circuit 47 level adjustment circuit 48 amplifier circuit 50 C / N detection circuit 51 gain adjustment circuit

Claims (3)

(57) [Claims] 1. A receiving demodulation unit for receiving an intermediate frequency signal output from an antenna for receiving a satellite broadcast wave and performing FM demodulation, and receiving an FM demodulation signal output from the receiving demodulation unit and performing FM demodulation A video signal processing unit for extracting and outputting a video signal included in the signal; an FM demodulated signal output from the reception demodulation unit being input to extract a digital audio signal included in the FM demodulated signal; A QPSK demodulator for QPSK demodulating the signal and outputting a first audio PCM signal; inputting the first audio PCM signal to generate and output a frame reference timing signal of the first audio PCM signal A reference timing generator, and the first audio PCM signal, and the first audio P
Through the signal processing for the CM signal, thereby extracting and outputting second audio PCM signal is removed error, double errors onset student has been associated with the first audio PCM signal <br/> and audio signal processing unit for detecting and outputting the dual error occurs it is output from the audio signal processing unit
And a suppression control unit that generates and outputs a signal suppression control signal for suppressing and controlling an output level of the second audio PCM signal and the video signal based on the frame reference timing signal; An output suppression circuit unit that receives an audio PCM signal and the video signal, suppresses the signal levels of the second audio PCM signal and the video signal to predetermined levels, and outputs the second PCM signal and the video signal according to the frame reference timing signal and the signal suppression control signal. And a satellite broadcast receiving apparatus. A second descrambling circuit for descrambling the first audio PCM signal; a third descrambling circuit for deinterleaving the audio PCM signal output from the descrambling circuit; A deinterleave circuit for extracting and outputting a PCM signal; and a third sound P output from the deinterleave circuit.
Enter the CM signal, the third and detects and outputs the dual error onset raw audio PCM signal, the error that generates and outputs the removed the dual error second audio PCM signal A suppression / correction circuit, wherein the suppression control unit counts and outputs the number of error occurrences corresponding to the double error occurrence frequency based on the double error occurrence and the frame reference timing signal. When the count value of the number of error occurrences output from the counter circuit exceeds a predetermined count value,
A suppression timing control circuit that generates and outputs a pair of suppression control signals for suppressing and controlling the output levels of the second audio PCM signal and the video signal at predetermined time intervals, respectively; The satellite broadcast receiving apparatus according to claim 1, further comprising: 3. The descrambling circuit for descrambling the first audio PCM signal, wherein the audio signal processing section deinterleaves the audio PCM signal output from the descrambling circuit. A deinterleave circuit for extracting and outputting a voice PCM signal; and a third voice P output from the deinterleave circuit.
Enter the CM signal, the third and detects and outputs the dual error onset raw audio PCM signal, the error that generates and outputs the removed the dual error second audio PCM signal And a detection / correction circuit, wherein the suppression control unit counts and outputs the number of error occurrences corresponding to the double error occurrence frequency based on the double error occurrence and the frame reference timing signal. When the count value of the number of error occurrences output from the counter circuit exceeds a predetermined count value,
A suppression timing control circuit for generating and outputting a suppression control signal for simultaneously suppressing and controlling the output levels of the second audio PCM signal and the video signal. 2. The satellite broadcast receiving device according to 1.