JPH11150694A - Sound signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an extraction timing error that occurs at the time of decoding a MUSE sound signal. SOLUTION: A frame synchronous pattern detection circuit 11 detects a frame synchronizing signal from a MUSE sound bit stream signal, and a majority discrimination circuit 16 discriminates data of a specific bit (e.g. bit 22) that takes a fixed value among control codes that are extracted by a control code extraction circuit 15 based on a frame synchronous pattern continuous detection signal S1 that is outputted when the frame synchronizing signal is continuously detected. A data extraction timing error detection circuit 17 detects whether required data is extracted from an inputted MUSE sound bit stream signal in a normal timing based on the signal S1 from the circuit 11 and a discrimination signal S5 from the circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal processing apparatus suitable for decoding audio data blocked in a predetermined range based on a frame synchronization signal.

[0002]

2. Description of the Related Art MUSE (mult) capable of realizing high-quality video and sound as a television system has already been realized.
An iple sub-Nyquist sampling encoding) system is known. An audio signal in a MUSE television signal (hereinafter simply referred to as a “MUSE signal”) is a quasi-instantaneous companding differential PCM (DANCE: differential pulse cod).
e modulation Audio Near-instantaneous Coresponding
and Expanding) in the vertical blanking period of the video signal. Such an audio signal (hereinafter "M
USE audio signal) is separated from the video signal by a signal separation circuit in the MUSE decoder,
It is input to an audio decoder that processes the E audio signal.

[0003] In an audio decoder, a MUSE audio signal which has been subjected to time compression and various interleaving is processed by a time decompression unit and a frame deinterleave unit to 1350 Kbit.
After being converted into a continuous bit stream signal of / sec, required decoding processing such as bit deinterleaving, error correction, and word deinterleaving is performed and output.

FIG. 3 shows an example of the frame structure of the MUSE audio bit stream signal as described above. The MUSE audio bit stream signal is shown in FIG.
And a basic unit (frame) is constituted by 1350 bits / msec data as shown in FIG.
Further, a master frame is constituted by every 36 frames.

As shown in FIG. 3B, the first 16 bits of one frame are used as a frame synchronization pattern composed of specific pattern data.
1010111110 ". The 22 bits following the frame synchronization pattern are used as control codes for voice control, and are data bits indicating a voice format, voice output suppression, and the like. The next 16 bits are channel 1 of the DANCE-converted audio data.
(CH1), the range bit of channel 2 (CH2), and within the 1296 bits following this range bit, DANCE audio data of channel 1, channel 2, range bits of channel 3 (CH3), channel 4 (CH4), channel 3, DANCE audio data of channel 4, independent data, and check bits. The frame structure shown in FIG. 3 is generally called an A mode in which a 15-bit original signal is encoded into 8 bits.

FIG. 4 shows the contents of the control code (22 bits) of the MUSE audio bit stream signal as described above. Bits 1 to 6 indicate bit data indicating the audio format, and bits 7 to 11 Are assigned as broadcast control extension bits. Bit 12 is a video scramble identification bit, which is "1" when video scrambling is performed and "0" when video scrambling is not performed. Bit 1
Reference numeral 3 denotes a scramble synchronization instruction bit, which is "1" when scramble synchronization is instructed, and is "0" when scramble synchronization is not instructed. Bit 14 is an identification bit of the master frame, and is "1" when the master frame is at the head, and "0" otherwise.

[0007] Bit 15 is a bit indicating whether data suppression is necessary or not, and bit 16 is a bit indicating whether audio output suppression is necessary. Each bit is set to "1" when necessary, and set to "0" when unnecessary. You. Bit 17 is a bit indicating an error correction mode, and is set to "0" when the error correction mode is the standard mode and "1" when the error correction mode is the enhancement mode.

Further, the following bit 21 is a bit indicating the presence or absence of a copy guard, and is set to "1" when there is a copy guard and "0" when there is no copy guard. The bit 22 is a bit for identifying the disc, and is "1" when the signal supply source of the MUSE signal is, for example, a video disc such as an LD (laser disc), and "1" when the source is other than that (for example, a broadcasting station). 0 ".

Of these 22-bit control codes, for example, a bit 17 indicating an error correction mode, a bit 21 indicating the presence or absence of a copy guard, and a bit 22 for disc identification are usually a MUSE signal composed of the same program. Depending on the signal source, the bit data takes a fixed value and is a bit whose data value does not change frequently.

In the above-described conventional audio decoder, if MUSE audio signal data is not extracted at a predetermined timing from an input signal, noise is generated when the decoded audio signal is output as audio. Therefore, it is necessary to correctly detect the timing of the MUSE audio signal from the input signal.

The detection of the timing of the MUSE audio signal in the audio decoder uses a frame synchronization pattern formed for each frame (1350 bits) of the MUSE audio bit stream signal. That is,
In the audio decoder, when a frame synchronization pattern is detected from an input signal, data is extracted about every 1350 bits (one frame) from a position where the frame synchronization pattern is detected. Then, when the frame synchronization pattern is continuously detected,
It is determined that the MUSE audio signal data is extracted from the input signal at regular timing, and the audio signal subjected to the decoding process is output as it is as audio.

On the other hand, if the audio decoder cannot detect the frame synchronization pattern from the input signal, for example, or if the frame synchronization pattern is detected at least once but cannot be detected continuously for a predetermined number of times, It is determined that the data is not MUSE audio data having a predetermined timing, and the decoded audio signal is suppressed (muted).

[0013]

However, when it is determined whether or not the MUSE audio signal data is extracted at a predetermined timing using the frame synchronization pattern as described above, the audio decoder performs the following operation. There is a problem that an error generated due to various factors cannot be detected.

First, as described above, in the audio decoder, whether or not the input signal is a MUSE audio signal extracted at a predetermined timing is determined using a frame synchronization pattern. If a bit error occurs in data after the frame synchronization pattern of a signal, it cannot be detected.

For example, as shown in FIG.
When one bit of the 22-bit control code included in the audio signal is lost, an error occurs such that 1-bit error data is added to the check bit.

In this case, in the circuit block for detecting the frame synchronization pattern, the frame synchronization pattern is detected at a normal timing. Therefore, in the circuit block for extracting the control code of the audio decoder, the bit data of the section A is used as the control code. In the circuit block for extracting the range bits, the bit data in the section B is extracted as the range bits. That is, in the circuit block for extracting the control code, the data after the missing bit is extracted with a shift of one bit at a time, and at least the least significant bit (LS) of the range bit is included in the control code bit 22.
The data of B) will be given.

As described above, when an error occurs in the extraction timing for extracting required data from the audio data received by the audio decoder due to some factor, the audio decoder may detect such an extraction timing error each time. It is impossible to do so, and a problem that noise is generated in the output voice occurs.

Further, for example, as shown in FIG.
In the DANCE audio data of the USE audio signal, for example, the same bit data as the frame synchronization pattern
If it occurs every 50 bits, the conventional audio decoder may erroneously detect this audio data as a frame synchronization pattern. In this case, the 22-bit audio data following the frame synchronization pattern and the audio data erroneously detected is used as the bit data of the control code, and the subsequent 1 bit.
6-bit audio data is extracted as range-bit bit data, and in this case also, a problem occurs in which noise is generated in the output audio.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an audio signal processing apparatus for extracting an audio signal from audio data blocked including a frame synchronization signal is provided. Frame synchronization signal detection means for detecting a frame synchronization signal from the audio data, control code extraction means for extracting a control code included in the audio data based on the frame synchronization signal, and a control code extracted by the control code extraction means Data extracting means for determining data of a specific bit of the data, a frame synchronization signal, and data extracting timing error detecting means for detecting a timing error of audio data based on the determining data from the data determining means. The error detection means may be configured to reset the audio data extraction timing. It was.

The data extraction timing error detection means detects a timing error of audio data based on the discrimination data from the data discrimination means when the frame synchronization signal and the input video lock signal are detected. I did it. The data of the specific bit of the control code takes a fixed value in the same audio information.

According to the present invention, the frame synchronization signal is detected from the audio data by the frame synchronization signal detection means, and when the frame synchronization signal is continuously detected, the control code extraction means extracts the frame synchronization signal based on the frame synchronization signal. Specific bits (for example, bit 2
The bit data of 2) is determined by the data determining means. The data extraction timing error detecting means extracts required data from the input audio data at normal timing based on the frame synchronization signal from the frame synchronization signal detecting means and the discrimination signal from the data discriminating means. Detect whether it is.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An audio signal processing apparatus according to an embodiment of the present invention will be described below. An audio signal processing apparatus according to the present embodiment generally includes a MUSE decoder for decoding a MUSE signal transmitted from a broadcasting station via satellite broadcasting or a communication satellite, and a laser disk (LD) on which information is recorded as a MSE signal. Since the present invention is applied to a reproducing apparatus that reproduces a recording medium such as a MUSE decoder, a MUSE decoder that decodes a MUSE signal transmitted via satellite broadcasting will be described as an example in this example.

FIG. 1 is a diagram showing an audio signal processing block of a MUSE decoder to which an audio signal processing device according to an embodiment of the present invention is applied. In FIG. 1, a radio wave transmitted from a broadcasting station (not shown) via a broadcasting satellite (BS) is input to a MUSE (BS) tuner 2 via a parabolic antenna 1 and a converter 1a. The MUSE signal of the channel selected by the MUSE tuner 2 is a low-pass filter (L
The signal is supplied to the A / D converter 4 via the PF 3. A / D
The MUSE signal converted to a digital signal by the converter 4 is
The video signal is supplied to the video signal processing unit 8 and the audio decoder 5.

The audio decoder 5 includes a first half processing unit 6 comprising a time decompression unit 6a and a frame deinterleave circuit 6b.
And a bit deinterleave circuit 7a and an error correction circuit 7
b, a second half processing unit 7 comprising a word deinterleave circuit 7c and a DANCE decoding circuit 7d.

The first-half processing section 6 has a ternary MUS
A ternary-to-binary conversion circuit for converting the E audio signal into a binary value is provided. The time decompressing unit 6a performs time-axis expansion of the binary-converted MUSE audio signal, and the frame deinterleave circuit 6b performs 1350 Kbit / bit conversion. The s bit serial signal is converted into a continuous MUSE audio bit stream signal and supplied to the second half processing unit 7.

The second half processing unit 7 receives the MU from the first half processing unit 6.
Bit deinterleaving, error correction, frame deinterleaving, DANC
It performs predetermined processing such as E-decoding and outputs it as an audio signal, and performs abnormal reception of an audio bit stream signal and detection of a data extraction timing error as described later.

The video signal processing section 8 is supplied with the MUSE signal from the A / D converter 4, performs predetermined processing on the video signal included in the MUSE signal, and outputs the processed video signal as a video signal. In addition, a video lock signal indicating the state of the reproduced video is output to the second half processing unit 7 of the audio decoder 5 as described later.

FIG. 2 shows an audio decoder 5 as described above.
FIG. 4 is a block diagram illustrating an example of an internal configuration of (mainly, a second half processing unit 7). In FIG. 2, a frame synchronization pattern detection circuit 11 detects a frame synchronization pattern included in each frame (1350 bits) of an input MUSE audio bit stream signal, and after detecting a frame synchronization pattern once. Performs a data check every 1350 bits from the detection position based on an input clock (1.35 MHz) CLK. When the frame synchronization pattern is detected continuously for a predetermined number of times, the frame synchronization pattern continuation detection signal S1 indicating that the frame synchronization pattern has been continuously detected is sent to the data extraction timing generation circuit 12 and the data extraction timing abnormality detection circuit 17 is output.

The data extraction timing generation circuit 12 receives a timing signal S2 for extracting a control code included in the MUSE audio bit stream signal when the frame synchronization pattern continuous detection signal S1 is supplied from the frame synchronization pattern detection circuit 11. A timing signal S3 for extracting a range bit and a timing signal S4 for extracting DANCE audio data are generated.

The DANCE audio data extraction circuit 13 extracts DANCE audio data contained in the input MUSE audio signal bit stream signal based on the timing signal S4 from the data extraction timing generation circuit 12. The range bit extraction circuit 14 receives the timing signal S3 from the data extraction timing generation circuit 12.
, The range bit data included in the input MUSE audio bit stream signal is extracted.

The control code extraction circuit 15 extracts a control code included in the input MUSE audio bit stream signal based on the timing signal S3 from the data extraction timing generation circuit 12, and specifies the extracted control code. Bit data (for example, bit 17, bit 21, and bit 22) is output to the majority decision circuit 16.

The majority decision circuit 16 performs a majority decision in units of master frames (36 frames) in order to prevent bit data of specific bits supplied from the control code extraction circuit 15 from being erroneous. Data extraction timing error detection circuit 17 as discrimination data
To be output.

Data extraction timing error detection circuit 17
When the frame synchronization pattern continuous detection signal S1 is supplied from the frame synchronization pattern detection circuit 11, the discrimination signal S5 from the majority decision circuit 16 is determined a predetermined number of times (n times).
MU based on these signals.
It is determined whether an error has occurred in the SE audio bit stream signal abnormal reception or data extraction timing. For example, when it is determined that an error has occurred in the data extraction timing, the frame synchronization pattern detection circuit 11
, A reset signal for the current data extraction timing is output.

DANCE extracted by the DANCE audio data extraction circuit 13 and the range bit extraction circuit 14
The CE audio data and the range bit data are subjected to an error correction process in an error correction circuit 18 and output to a deinterleave circuit 19, and a process is performed by bit deinterleave and word deinterleave so that the audio data becomes an original arrangement. After that, it is decoded by the DANCE audio decoding circuit 20 and output as an audio signal.

In the thus configured audio decoder 5 according to the present embodiment, when the frame synchronization pattern is continuously detected by the frame synchronization pattern detection circuit 11, the frame synchronization pattern continuous detection signal S1 is output at the data extraction timing. Output to the generation circuit 12 and the data extraction timing error detection circuit 17.

The data extraction timing generation circuit 12 generates a timing signal S2 for extracting a control code based on the frame synchronization pattern continuation detection signal S1 from the frame synchronization pattern detection circuit 11. Then, based on the timing signal S2, the control code extraction circuit 15
, The control code included in the input MUSE audio bit stream signal is extracted.

The control code extraction circuit 15 normally includes, for example, a bit 22 for disc identification, in which the bit data takes a fixed value without randomly changing the bit data, and a bit indicating the presence or absence of a copy guard. 21, any one of the bit data 17 indicating the error correction mode is extracted for each frame and output to the majority decision circuit 16.

The data of a specific bit (for example, bit 22) of the control code output from the control code extraction circuit 15 is subjected to a majority decision in the majority decision circuit 16 in master frame units, and the result of the decision is used as a decision signal S5. It is supplied to the data extraction timing error detection circuit 17. As described above, the majority decision circuit 16 performs majority decision on the specific bit (bit 22) of the input control code in master frame units (36 msec), so that a data error in the transmission system is detected, and the majority decision circuit 16 The discrimination signal S5 output from 16 has a very high probability of outputting a correct data value even if a data error occurs during transmission.

The data extraction timing error detection circuit 17 detects whether an abnormal reception of the MUSE audio bit stream signal or an extraction timing error has occurred based on the frame synchronization pattern continuation detection signal S1 and the discrimination signal S5. Will be done.

In this case, the data extraction timing error detection circuit 17 takes in the discrimination signal S5 from the majority decision discrimination circuit 16 only when the frame synchronization pattern detection circuit 11 supplies the frame synchronization pattern continuation detection signal S1. When the signal S5 is extracted n times, it is determined how many times the data has changed among the n times of data.

That is, the data extraction timing error detection circuit 17 receives the frame synchronization pattern continuation detection signal S1 from the frame synchronization pattern detection circuit 11 so that the input signal has a predetermined format.
It is determined whether or not the signal is a USE audio bit stream signal, and only when it is determined that the signal is a MUSE audio bit stream signal having a predetermined format, based on the determination signal S5 from the majority decision circuit 16, the signal is extracted from the MUSE audio bit stream signal. The presence or absence of a data extraction timing error is determined.

The specific bits (bit 17, bit 21,...) Of the control code determined by majority decision in the majority decision circuit 16
Since the data of bit 22) usually takes a fixed value, if this specific bit is extracted at normal timing,
The decision signal S5 output from the majority decision circuit 16 has a fixed value.

Therefore, the data extraction timing error detection circuit 17 is provided when the frame synchronization pattern continuous detection signal is detected from the frame synchronization pattern detection circuit 11 and the data change of the discrimination signal S5 from the majority decision circuit 16 is large. Determines that an error has occurred in the data extraction timing, and in this case, outputs a reset signal to the frame synchronization pattern detection circuit 11 to reset the operation of detecting the frame synchronization pattern in the frame synchronization pattern detection circuit 11. . As a result, in the audio decoder according to the present embodiment, an extraction timing error for extracting data such as a control code from a MUSE audio signal, which could not be determined conventionally, or an accidental occurrence in DANCE audio data. It is possible to prevent a detection error such as detecting the same data as the frame synchronization pattern as the frame synchronization pattern.

When the data extraction timing error detection circuit 17 determines that an error has occurred in the data extraction timing, the data extraction timing error detection circuit 17 suppresses the sound output by a circuit block for controlling the sound output (not shown). Mute) may be applied to prevent noise from being generated in the output voice.

Further, in the audio decoder according to the present embodiment, the determination signal S5 from the majority decision circuit 16 is detected only when the frame synchronization pattern continuous detection signal S1 is detected from the frame synchronization pattern detection circuit 11. I am trying to do it. Accordingly, for example, when the transmission medium of the MUSE signal is a radio wave, when the C / N (carrier-to-noise ratio) of the received MUSE signal is deteriorated due to weather conditions or the like,
The signal supply source of the MUSE signal is a laser disk (L
In the case of a recording medium such as D), for example, in a reproducing apparatus for reproducing a laser disk, special reproduction → normal reproduction, normal reproduction →
When an operation such as trick play is performed and the playback device switches from the locked state to the unlocked state, even if the data of a specific bit of the control code changes, an erroneous reception or extraction timing error may occur by mistake. Detection can be prevented.

In the above-described embodiment, the data extraction timing error detection circuit 17 of the audio decoder second half processing unit 7 performs the frame synchronization pattern detection circuit 1
The case where the discrimination signal S5 from the majority decision circuit 16 is discriminated only when the frame synchronization pattern continuous signal S1 from No. 1 is detected has been described, but the data extraction timing error detection circuit 17 includes the video signal processing unit 8 (see FIG. 1)
The video lock signal may be input from the CPU.

Then, in the data extraction timing error detection circuit 17, the frame synchronization pattern detection circuit 11
The determination signal S5 from the majority determination circuit 16 may be fetched only when the frame synchronization pattern continuous signal S1 from the CPU and the video lock signal input from the video signal processing unit 8 (see FIG. 1) are detected. . Further, the data extraction timing error detection circuit 17 receives the discrimination signal S5 from the majority decision discrimination circuit 16, and stops detecting the frame synchronization pattern continuously from the frame synchronization pattern generation circuit 11; If the video lock signal from the processing unit 8 is no longer detected,
The determination signal S5 from the majority determination circuit 16 may be read again.

In this embodiment, at least the frame synchronization pattern of the MUSE audio bit stream signal and the bit data of specific bits (for example, bit 22, bit 21, and bit 17) which are fixed values of the control code are used. A case has been described in which the presence / absence of an abnormal reception or an extraction timing error in the audio decoder is determined, but it is of course possible to use other bit data included in the MUSE audio bit stream signal.

In the present embodiment, MUSE
Although an audio bit stream signal has been described as an example, other bit stream signals having a frame synchronization pattern can be similarly realized.

[0050]

As described above, according to the present invention, the frame synchronization signal detecting means detects the frame synchronization signal from the audio signal, and when the frame synchronization signal is continuously detected,
Among the control codes extracted by the control code extracting means based on the frame synchronization signal, data of a specific bit (for example, bit 22) having a fixed value is determined by the data determining means. The data extraction timing error detecting means detects an extraction timing error occurring after the frame synchronization signal of the input audio data based on the frame synchronization signal from the frame synchronization signal detecting means and the determination signal from the data determination means. Detection is performed.

As a result, an extraction timing error for extracting data such as a control code from a MUSE audio signal which could not be detected conventionally, or the same data as a frame synchronization pattern accidentally generated in DANCE audio data is used for frame synchronization. This makes it possible to prevent a detection error such as detection as a pattern, and to prevent noise from being generated in the output voice.

[Brief description of the drawings]

FIG. 1 is a diagram showing an audio system block of a MUSE decoder to which an audio decoder according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram showing an internal configuration of a second half processing unit of the audio decoder according to the embodiment;

FIG. 3 is an explanatory diagram of a frame structure of a MUSE audio bit stream signal.

FIG. 4 is an explanatory diagram of control codes included in a MUSE audio bit stream signal.

FIG. 5 is a diagram showing a state of data extraction timing of a MUSE audio bit stream signal in a conventional audio signal processing device.

[Explanation of symbols]

1 BS antenna, 2 MUSE tuner, 3 LP
F, 4 A / D converter, 5 audio decoder, 6 first half processing unit, 7 second half processing unit, 8 video signal processing unit, 11 frame synchronization pattern detection circuit, 12 data extraction timing generation circuit, 13 DANCE audio data extraction circuit, 14
Range bit extraction circuit, 15 control code extraction circuit, 16
Majority decision circuit, 17 data extraction timing error detection circuit, 18 error correction circuit, 19 deinterleave circuit, 20 DANCE audio decoding circuit

Claims (3)

[Claims] 1. An audio signal processing apparatus for extracting an audio signal from audio data blocked including a frame synchronization signal, comprising: a frame synchronization signal detecting means for detecting a frame synchronization signal from the audio data; Control code extracting means for extracting a control code included in the audio data based on the control signal extracting means; data determining means for determining data of a specific bit of the control code extracted by the control code extracting means; Data extraction timing error detection means for detecting a timing error of the audio data based on the determination data from the data determination means, wherein the data extraction timing error detection means resets the extraction timing of the audio data. Audio signal processing apparatus characterized in that . 2. The data extraction timing error detecting means detects a timing of the audio data based on discrimination data from the data discrimination means when the frame synchronization signal and an input video lock signal are detected. The audio signal processing device according to claim 1, wherein an error is detected. 3. The data of a specific bit of the control code is:
The audio signal processing device according to claim 1, wherein a fixed value is taken for the same audio information.