KR100212851B1 - Audio muting method in a digital dbs receiver - Google Patents

Abstract

The present invention relates to a method of audio mute in a digital DBS receiver, which comprises a microcomputer for outputting a mute control signal and an attenuation control signal, an audio decoding unit for performing a digital audio signal decoding process and generating a mute signal according to the mute control signal, A D / A converter for converting the decoded digital audio signal into an analog signal according to the mute signal, and an attenuator for attenuating the converted analog audio signal according to the attenuation control signal, Transmitting a control signal to the audio decoding unit (S1); Transmitting the attenuation control signal to the attenuator (S2); Generating a mute signal according to the mute control signal input by the audio decoding unit (S3); (S4) transmitting the decoded digital audio signal and the mute signal to the D / A converter; Determining whether the mute signal is input by the D / A converter, and terminating all the audio mute processes according to the determination result (S5); As a result of the determination in step S5, when the mute signal is input to the D / A converter, the D / A converter and the attenuator gradually attenuate the input digital audio signal to generate a voltage value of 0 [V] (S6) of converting an audio signal having a high voltage value into an analog audio signal having a high voltage value. The present invention has the effect of providing a higher quality audio service to a user by eliminating noise generated when an audio signal having a high voltage value is muted.

Description

A method of muting audio signals in a digital DBS receiver (Digital Direct Broadcasting Service receiver)

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an audio mute method in a digital direct broadcast service (DBS) receiver, and in particular, The present invention relates to an audio mute method for gradually attenuating an audio signal using an attenuation function to eliminate noise generated when an audio signal having a high voltage value is muted.

The mute function provided in most video and audio systems means a function of not deliberately outputting video or audio signals in accordance with a control signal of a user or a control signal of a microcomputer.

FIG. 1 is a block diagram schematically illustrating the configuration of a general video and audio system having the above-described audio mute function. The general video and audio system includes a receiving antenna 2, a tuner 4, a video signal processor 6 A video amplifying unit 8, a video signal output unit 10, a remote controller 12, a microcomputer 14, an audio signal processing unit 16, an audio amplifying unit 18, a switching unit 20, (22).

The switching unit 20 includes a protection resistor R and a transistor TR.

The signal received by the receiving antenna 2 is selected by the tuner 4 and then input to the video signal processing unit 6 and the audio signal processing unit 16 and processed appropriately. The signal-processed video signal is input to the video amplifier 8 and amplified, and then inputted to the video signal output unit 10 and displayed to the user.

The audio signal input from the audio signal processing unit 16 is amplified by the amplifying unit 18 and input to the switching unit 20 and then switched according to a control signal of the user or a control signal of the microcomputer.

That is, when there is a mute signal input, the switching unit 20 is turned off and the amplified audio signal is not output. On the other hand, when the mute signal input is not normal, the switching unit 20 is turned on and the amplified audio signal is output.

However, since the transistor TR of the switching unit 20 can not perform an accurate on / off operation due to the analog nature of the device, an accurate mute function can not be expected. In a digital system, A large amount of data may be lost. Therefore, there is a need for a new audio muting method that can accurately perform the mute function.

FIG. 2 is a block diagram illustrating the configuration of a digital DBS receiver applied to the new audio mute method. The digital DBS receiver includes a reception antenna 10, a tuner 12, an A / D conversion unit 14, A demultiplexer 16, a channel decoder 18, a transport stream demultiplexer 20, a decryption unit 22, a remote controller 24, a microcomputer 26, a modem 28, a smart card 30, A video decoding unit 34, an NTSC coding unit 36, an audio decoding unit 38, a D / A converter 40 and a radio frequency (RF) modulating unit 42 .

The D / A converter 40 includes a D / A converter 40-1 and an attenuator 40-2.

The D / A converter 40 includes a remote controller 24 for performing an audio mute function, a microcomputer 26, an audio decoding unit 38, a D / A conversion unit 40-1 and an attenuation unit 40-2. (40) will be mainly described, and the remaining parts will be described in detail in the present invention again and will be omitted.

First, QPSK modulation, channel coding, transport stream multiplexing, and video / audio encoded signals are relayed through a satellite repeater (not shown) at a transmitting end (not shown) and then received by the receiving antenna 10.

Since the received signal is an analog signal, it is subjected to A / D conversion, QPSK demodulation, channel decoding, and transport stream demultiplexing, and is input to the audio decoding unit 38.

The audio decoding unit 38 not only decodes the demultiplexed encoded audio signal but also generates a mute signal according to a mute control signal input from the microcomputer 26, 40-1.

The D / A converter 40-1 performs the following two operations according to the mute signal input together with the decoded digital audio signal.

First, when the input mute signal is high or mute, the D / A converter 40-1 converts the decoded digital audio signal into an analog signal having a voltage value of 0 [V] . That is, the D / A converter 40-1 does not output an audio signal.

Secondly, when the mute signal is low, that is, normally, the D / A converter 40-1 converts the decoded digital audio signal into an analog signal and outputs the analog signal. That is, the D / A converter 40-1 performs only a normal D / A conversion process.

The attenuation unit 40-1 is not used at the time of performing the mute function but is used for volume adjustment control of the user.

FIG. 3 is a flowchart illustrating an audio mute method in a conventional digital DBS receiver configured as described above. A conventional audio mute method will be described with reference to FIG.

In the first step S10, the microcomputer 26 transmits a mute control signal to the audio decoding unit 38. [ The mute control signal is a signal controlled by the user remote control 24 or a signal controlled by the microcomputer 26 itself.

In the second step S20, the audio decoding unit 38 generates a mute signal corresponding to the mute control signal.

That is, the audio decoder 38 generates a low level signal when the mute control signal is not input, and a high level signal when the mute control signal is input.

In the third step S30, the audio decoding unit 38 transmits the decoded digital audio signal and the mute signal to the D / A converter 40-1.

In the fourth step S40, the D / A converter 40-1 determines whether the mute signal is at a high level. If the input signal is at a low level, the D / A converter 40-1 terminates all audio mute methods do.

That is, when a low level mute signal is input to the D / A converter 40-1, the decoded digital audio signal is converted into an analog audio signal and then output in the following two ways. One is to output the analog audio signal to an audio output device (not shown) in the form of an audio left / right (Left / Right) stereo, and the other is to output to the RF modulating part 42, Output to the device.

On the other hand, if it is determined in the fifth step S50 that the mute signal is at a high level as a result of the determination in the fourth step S40, the D / A converting unit 40-1 sets the decoded digital audio signal to 0 Into an analog audio signal having a voltage value of [V] and outputs it.

That is, since the D / A converter 40-1 does not output an audio signal, the user can not hear any sound.

4A is a waveform diagram of the D / A-converted audio signal in a state in which the mute function is not provided, FIG. 4B is a waveform diagram of the audio signal output from the microcomputer 26 to the audio decoding unit 38, (C) is a waveform diagram of a mute signal input from the audio decoding unit 38 to which the mute control signal is inputted to the D / A conversion unit 40-1, (d) is a waveform diagram of the mute function FIG. 6 is a waveform diagram of an audio signal subjected to D / A conversion in a state in which it is provided. The solid line in (D) is a waveform diagram of an audio signal that is ideally D / A converted, and a dotted line is a waveform diagram of an audio signal actually D / A converted.

The audio mute process will be described with reference to the above drawings.

First, as shown in (b), the mute control signal maintains the low level and the mute signal maintains the low level according to the mute control signal as shown in (c), so that the D / A conversion unit 40-1) outputs an analog audio signal normally D / A-converted as indicated by the solid line in (d).

On the other hand, at the time of the mute, the mute control signal which kept the low level swings to the high level as shown in (b), and the mute control signal which kept the low level according to the mute control signal The D / A converter 40-1 outputs an analog audio signal having a voltage value of 0 [V] as indicated by the solid line in FIG.

However, in the audio mute method, when a digital audio signal having a high voltage level and a high-level mute signal are input to the D / A converter 40-1, And so on.

There has been a growing demand for a new audio muting method capable of eliminating a complicated sound caused by the noise, which is discomfort to the user.

Accordingly, the present invention provides a high-quality audio service that meets the above-mentioned needs, and more particularly to a digital DBS receiver for slowly muting an audio signal by using a D / A converter attenuation function when an audio signal is muted And to provide an audio muting method in a digital DBS receiver.

In order to achieve the above object, an audio mute method in a digital DBS receiver according to the present invention includes a microcomputer for outputting a mute control signal and an attenuation control signal and a digital audio signal decoding process, A D / A converter for receiving and decoding the decoded digital audio signal according to the mute signal, or converting the decoded digital audio signal to an analog signal, and a D / A converter for converting the decoded digital audio signal into an analog signal, A first step of transmitting the mute control signal to the audio decoding unit by the microcomputer, the digital DBS receiver comprising: an attenuation unit for receiving and attenuating an analog audio signal; A second step of the microcomputer transmitting the attenuation control signal to the attenuator; A third step of the audio decoding unit generating a mute signal according to the input mute control signal; A fourth step of delivering the digital audio signal and the mute signal decoded by the audio decoding unit to the D / A converter; A fifth step of, after determining whether the mute signal is input by the D / A converter, if the mute signal is not inputted, ending all the audio mute methods; As a result of the determination in the fifth step, when the mute signal is input to the D / A conversion unit, the D / A conversion unit 40-1 and the attenuation unit 40-2 output the input digital audio signal And outputting the analog audio signal having a voltage value of 0 [V].

According to the present invention as described above, the audio signal is gradually muted by using the attenuation function of the D / A converter, thereby eliminating the noise (puck sound) generated when the audio signal having the high voltage value is muted, To the user.

1 is a block diagram schematically showing the configuration of a general video and audio system having an audio mute function,

2 is a block diagram illustrating a configuration of a digital DBS (Direct Broadcasting Service) receiver having an audio mute function,

3 is a flowchart showing a conventional audio muting method in a digital DBS receiver having an audio mute function,

4A shows the waveform of the D / A-converted audio signal in a state in which the audio mute function is not provided,

(B) is a waveform diagram of a mute control signal input from the microcomputer to the audio decoding unit,

(C) is a waveform diagram of a mute signal input from the audio decoding unit to the D / A converter,

(D) The waveform of the D / A converted audio signal in the state where the audio muting function is provided,

5 is a block diagram schematically showing the entire configuration of a digital DBS system,

6 is a block diagram illustrating the configuration of a digital DBS receiver having an audio mute function according to the present invention.

7 is an input / output signal waveform diagram of the D / A converter,

FIG. 8 is a flowchart illustrating an audio mute method in a digital DBS receiver according to the present invention.

9 (A) shows the waveform of the D / A-converted audio signal in a state in which the audio muting function is not provided,

(B) is a waveform diagram of a mute control signal input from the microcomputer to the audio decoding unit,

(C) is a waveform diagram of an attenuation control signal input from the microcomputer to the attenuator,

(D) is a waveform diagram of a mute signal input from the audio decoding unit to the D / A converter,

(E) is a waveform diagram of the D / A converted audio signal in a state in which the audio muting function is provided.

DESCRIPTION OF THE REFERENCE NUMERALS

10: Receive antenna 12: Tuner

14: A / D conversion unit 16: QPSK demodulation unit

18: Channel decoding section 20: Transport stream demultiplexing section

22: decryption unit 24: remote control

26: Micom 28: Modem

30: smart card 32: memory

34: Video decoding section 36: NTSC coding section

38: Audio decoding unit 40: D / A converter

40-1: D / A converter 40-2: attenuator

42: RF modulation section

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, an overall configuration of a digital DBS system will be described in order to facilitate understanding of the present invention.

First, digital DBS refers to a broadcasting method in which a broadcasting signal is retransmitted through a satellite transponder for the purpose of direct reception in a general household. Since recent technology has been developed, direct reception is possible by installing a small antenna and a digital DBS receiver, .

The DBS can not perform local broadcasting, requires a large investment with a high reliability requirement, and has a disadvantage in that it causes a problem of propagation menstruation. On the other hand, the DBS is capable of uniformly high-quality broadcasting in a large area with a small output compared to terrestrial broadcasting, In Korea, it has begun to provide digital DBS test broadcasting from July 1, 1996 by using the Mugunghwa satellite because it has the advantage of reducing the reception disturbance and ghost phenomenon.

5 is a block diagram showing the overall configuration of a digital DBS system. The digital DBS system includes a service provider 1, a satellite transponder 2 and a subscriber 3, (1) and the subscriber side (3) are connected through a public switched telephone network (PSTN).

The service provider side 1 comprises a transmitter 11 (Encoder Transmitter) for encoding, converting and multiplexing television signals into transport stream packets and then channel-coding the signals to transmit them to a satellite in a frequency band of 14 GHz, And a resource subscriber management system (hereinafter referred to as RSMS) 12 for collecting usage information of the subscriber.

The transmitter 11 includes an MPEG-2 (Moving Picture Expert Group-2) coding unit 11-1, a FEC (Forward Error Correction) coding unit 11-2, a QPSK (Quaternary Phase Shift Keying) -3) and a transmission antenna 11-4.

The satellite transponder 2 receives the transport stream from the transmitter 11, amplifies it, and retransmits it to the 12 GHz frequency band.

The subscriber 3 comprises a receiving antenna 31, a Low Noise Block-Down (LNB) 32, a digital DBS receiver 33 and a television 34.

The digital DBS receiver 33 includes a tuner 33-1, a QPSK demodulator 33-2, an FEC decoder 33-3, and an MPEG-2 decoder 33-4.

The operation of the digital DBS system configured as above will be described below.

The MPEG-2 coding unit 11-1 of the transmitter 11 converts video, audio and data signals into digital signals in accordance with the MPEG-2 standard, compresses the digital signals, forms packet streams, Creates a signal stream.

Then, the plurality of digital television signal streams are multiplexed into transport stream packets and then sent to the FEC coding unit 11-2.

The FEC coding unit 11-2 performs channel coding in order to correct errors occurring in transmission.

The QPSK modulator 11-3 performs a modulation process to transmit the channel-encoded signal to the satellite.

The modulated signal is converted from an up-converter (not shown) to a ku-band (14 GHz), amplified sufficiently by a high power amplifier (HPA) .

The satellite is composed of at least one satellite transponder 2. The satellite transponder 2 receives and amplifies the 14 GHz uplink signal transmitted from the base station and converts it to 12 GHz and retransmits it to the ground again.

The 12 GHz band transport stream signal relayed from the satellite transponder 2 is received by the receiving antenna 31.

The LNB 32 drops the received 12 GHz transport stream signal to an intermediate frequency signal of 1 GHz band, removes the noise, and sends the signal to the tuner 33-1 through a cable.

The signal selected by the tuner 33-1 is demodulated by the QPSK demodulation unit 33-2, and the demodulation signal is restored by the FEC decoding unit 33-3.

The signal in which the transmission error is restored is decoded into a video, an audio and a data signal in the MPEG-2 decoding unit 33-4.

The decoded signal is displayed to the viewer through the television 34.

FIG. 6 is a block diagram showing a digital DBS receiver applied to the present invention.

The digital DBS receiver shown in FIG. 6 includes a reception antenna 10, a tuner 12, an A / D conversion unit 14, a QPSK demodulation unit 16, a channel decoding unit 18, a transport stream demultiplexing unit 20, a decryption unit 22, a remote control 24, a microcomputer 26, a modem 28, a smart card 30, a memory 32, a video decoding unit 34, an NTSC coding unit 36, An audio decoding unit 38, a D / A converter 40, and an RF modulating unit 42.

The D / A converter 40 includes a D / A converter 40-1 and an attenuator 40-2.

The receiving antenna 10 receives a transport stream from a satellite repeater (not shown), and the tuner 12 receives a transport stream received from the receiving antenna 10, Tune in.

The A / D converter 14 converts the selected analog signal into a digital signal, and the QPSK demodulator 16 receives the A / D-converted QPSK modulation signal and performs QPSK demodulation.

The channel decoding unit 18 receives the QPSK demodulated channel-encoded signal and channel-decodes the received signal.

The transport stream demultiplexer 20 demultiplexes the channel-decoded multiplexed stream and extracts only the audio / video data of a channel desired by the viewer. The decryptor 22 decrypts the received encrypted signal, Decrypts the data so that the user can view the data.

The microcomputer 26 controls the entire system according to a reception signal from the remote controller 24, and the modem 28 is a device for communication between a resource and subscriber management system (not shown) and a receiver.

The smart card 30 authorizes only the subscriber having the reception right to decrypt the encrypted data so as to receive the data, stores and provides information about the pay-per-view, Stores the program of the microcomputer 26. [

The video decoding unit 34 receives and decodes the extracted video signal, and the NTSC coding unit 36 encodes the decoded video signal into an analog signal in order to receive and display the decoded video signal.

There are the following two methods of encoding and outputting a video signal in the NTSC coding unit 36. One is for outputting the encoded video signal to a video output device (not shown) in the form of a baseband video signal, and the other is for outputting to the RF modulator 42.

The audio decoder 38 receives the extracted audio signal and decodes the audio signal. The audio decoder 38 decodes the decoded audio signal, an audio clock (ACLK), a bit clock (Bit CLK) A left / right clock (hereinafter referred to as LR CLK) and a mute control signal input from the microcomputer 26, and outputs the generated mute signal to the D / A converter 40-1 .

7 shows an input signal waveform and an output signal waveform of the D / A converter 40-1.

The ACLK shown in FIG. 7 is used only at the time of over sampling D / A conversion. The ACLK samples the audio signal decoded by the number of ACLKs in 1-bit clock period and determines whether the corresponding bit is '1' or '0'. When the normal, the sampling frequency is given by f _s, ACLK has a frequency of 256f or 384f _{s s.}

In addition, the bit CLK shown in FIG. 7 varies in frequency depending on how many bits of an audio signal sample are represented. For example, when one audio signal sample is represented by 16 bits, the frequency of the bit CLK is set to 16 * 2 * f _s (sampling frequency). In the equation for obtaining the frequency of the bit CLK, the meaning of 2 is to find a bit CLK corresponding to two samples of the left / right.

The LR CLK shown in FIG. 7 is a signal for discriminating whether the decoded audio signal is a left signal or a right signal. For example, when the LR CLK is '1', it indicates that the decoded audio signal is the left signal, and when the LR CLK is '0', it indicates that the decoded audio signal is the right signal.

When the mute signal is applied together with the decoded digital audio signal as shown in FIG. 7, the analog audio signal shown in FIG. 7 is output.

The D / A converter 40-1 receives the decoded audio data, which is a digital signal, and converts the decoded audio data into an analog signal, and outputs the analog signal in the following two ways. One is for outputting to the display device in the form of audio left / right (Audio - Right / Left) stereo, and the other is for outputting to the high frequency modulating part 42.

The RF modulator 42 modulates the audio / video signal and outputs an RF signal.

Then, the RF signal, the baseband video signal, and the left and right audio signals are displayed to a user via a video / audio input / output device (not shown).

FIG. 8 is a flowchart illustrating a method of audio mute in the digital DBS receiver configured as described above according to the present invention, and an audio mute method according to the present invention will be described with reference to FIG.

First, QPSK modulation, channel coding, transport stream multiplexing, and video / audio encoded signals are relayed through a satellite repeater (not shown) at a transmitting end (not shown) and then received at the receiving antenna 10.

Since the received signal is an analog signal, it is subjected to A / D conversion, QPSK demodulation, channel decoding, and transport stream demultiplexing, and is input to the audio decoding unit 38.

Then, the audio decoding unit 38 receives and demodulates the demultiplexed encoded audio signal.

At this time, the microcomputer 26 transmits a mute control signal to the audio decoding unit 38 in the first step S1. The mute control signal is a signal controlled by the user remote control 24 or a signal controlled by the microcomputer 26 itself.

At the same time, in the second step S2, the microcomputer transmits the attenuation control signal to the attenuator.

In a third step S3, the audio decoding unit 38 generates a mute signal corresponding to the mute control signal.

That is, the audio decoder 38 generates a low level signal when the mute control signal is not input, and a high level signal when the mute control signal is input.

In the fourth step S4, the audio decoding unit 38 transmits the decoded digital audio signal and the mute signal to the D / A converting unit 40-1.

In the fifth step S5, the D / A converter 40-1 determines whether the mute signal is at a high level. If the input signal is at a low level, the D / A converter 40-1 terminates all the audio mute methods do.

That is, when a low level mute signal is input to the D / A converter 40-1, the decoded digital audio signal is converted into an analog audio signal and then output in the following two ways. One is to output the analog audio signal to an audio output device (not shown) in the form of an audio left / right (Left / Right) stereo, and the other is to output to the RF modulating part 42, Output to the device.

On the other hand, if the mute signal is at the high level as a result of the determination in the fifth step S5 in the sixth step S6, the D / A conversion unit 40-1 and the attenuation unit 40-2 And gradually decodes the decoded digital audio signal to convert it into an analog audio signal having a voltage value of 0 [V] and output it.

That is, the D / A conversion unit 40-1 and the attenuation unit 40-2 gradually attenuate the audio signal so that no signal is finally output, so that the user can not hear any sound.

9A is a waveform diagram of a D / A-converted audio signal in a state where the audio mute function is not provided, FIG. 9B is a waveform diagram of a mute control signal input from the microcomputer to the audio decoding unit, and FIG. (D) is a waveform diagram of an attenuation control signal input to the attenuator in the microcomputer, (d) is a waveform diagram of a mute signal input to the D / A converter in the audio decoding unit, FIG. 2 is a waveform diagram of a D / A converted audio signal in a state in which the D / A conversion is performed.

The audio mute process will be described with reference to the above drawings.

First, as shown in (B), the mute control signal maintains the low level and the attenuation control signal also maintains the low level as shown in (C), and as shown in (D), the mute signal By maintaining the low level in accordance with the mute control signal, the D / A converter 40-1 outputs the analog audio signal normally D / A-converted as in (D).

On the other hand, at the time of mute, the mute control signal which kept the low level swings to the high level as shown in (b), and the attenuation control signal which maintains the low level as shown in (c) As shown in FIG. 4 (d), the mute signal, which maintains a low level according to the mute control signal, swings to a high level. As shown in (D), the D / A converter 40-1 and the attenuator Unit 40-2 gradually attenuates the inputted digital audio signal and converts it into an analog signal having a voltage value of 0 [V].

That is, the D / A conversion unit 40-1 and the attenuation unit 40-2 attenuate the input digital audio signal in three steps,

enuation), and at the end very severe attenuation (no signal output).

Therefore, the audio mute method in the digital DBS receiver according to the present invention uses the attenuation function of the D / A converter, which has been conventionally used for adjusting the volume, at the time of audio muting to gradually mute the audio signal, It removes the noise that occurs during mute.

As described above, since the audio signal is gradually muted by using the attenuation function of the D / A converter, it is possible to eliminate the noise (puck sound) generated when the audio signal having a high voltage value is muted, And the like.

Claims (1)

An audio decoder for performing a mute control signal and an attenuation control signal and for generating a mute signal according to a mute control signal input from the microcomputer as well as a digital audio signal decoding process, A digital DBS receiver including a D / A converter for receiving an audio signal and converting the received analog signal into an analog signal, and an attenuator for receiving and converting the converted analog audio signal according to the attenuation control signal, To the audio decoding unit (S1); A second step (S2) of transmitting the attenuation control signal to the attenuator by the microcomputer; A third step (S3) in which the audio decoding unit generates a mute signal according to the input mute control signal; A fourth step (S4) of delivering the digital audio signal and the mute signal decoded by the audio decoding unit to the D / A conversion unit; A fifth step (S5) of judging whether the mute signal is inputted in the D / A converter and then ending all the audio mute if the mute signal is not inputted; As a result of the determination in the fifth step S5, when the mute signal is input to the D / A converter, the D / A converter and the attenuator gradually attenuate the input digital audio signal so that 0 [V] And a sixth step (S6) of outputting an analog audio signal having a voltage value.