JP2002170330A - Pcm audio signal reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an audio signal reproducing device capable of shortening silence time and hardly generating noise at the time of starting reproduction and changing audio signal methods or the like. SOLUTION: This audio signal reproducing device is provided with a bit pattern deciding device and a mute circuit for muting a reproduced audio signal. When reproduction is started, the mute circuit is operated, when the bit pattern deciding device detects a DTS synchronizing signal and a DTS header signal from a bit stream within a prescribed period, the reproduction mode of signal processing is changed to a DTS mode and the mute of the mute circuit is released, and when the bit pattern deciding device does not detect the DTS synchronizing signal and the DTS header signal from the bit stream within the prescribed period, the reproduction mode of the signal processing is changed to a PCM mode and the mute of the mute circuit is released.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention automatically discriminates between uncompressed PCM audio data in a bit stream transmitting PCM data and compressed PCM audio data of the DTS system, and sets the reproduction mode to PCM mode or DTS.
The present invention relates to an audio signal reproducing device capable of switching to a mode for reproduction.

[0002]

2. Description of the Related Art The standard of compact discs for music (hereinafter, compact discs are also referred to as CDs) was established in 1981 as a so-called red book, and thereafter, the CDs were described.
Many applications have been established, such as those that add an image signal to a PCM audio signal and record it on a CD. DTS (Digital Theater Systems) audio system is one of the applications using PCM data.
This is a system proposed by Digital Theater Systems, Inc., which is recorded on a recording medium such as the CD.

In this specification, uncompressed PCM audio data is also referred to as general PCM data. In general, digital music data is recorded as uncompressed PCM audio data for two channels on a recording medium, whereas in the DTS method, multi-channel PCM data is recorded as compressed PCM audio data. In a general music CD defined by the Red Book, two channels of uncompressed PCM audio data (general PCM data) are recorded, and general digital music data read from the CD is , And are output as uncompressed general PCM data through EFM demodulation and code error correction.

[0004] The DTS audio system is a system for compressing and recording multi-channel audio signals, and is adopted as a recording system not only for CDs but also for LD systems and DVD systems. DTS signals recorded on CDs and LDs are recorded as PCM data so that data can be read out by a reproducing device existing before the advent of the DTS system. Is compressed data.

FIG. 6 is a block diagram showing a general PCM audio signal reproducing apparatus. FIG. 6A shows a reading device of a general PCM audio signal reproducing device 20, and FIG. 6B shows a receiving device (receiver) of the general PCM audio signal reproducing device 20. The reader and the receiver are usually manufactured in separate housings, and the output of the reader is provided to the receiver via an optical cable or the like. The reading device includes an optical head 11 that reads data from a recording medium such as an optical disk, a first signal processing circuit 13 that performs EFM demodulation and error correction processing on the output of the optical head 11, and a digital audio interface format ( Hereinafter, also referred to as DAI)
And a DIT (Digital Interface Transmitter) 15 which modulates the signal into a signal conforming to the standard and transmits the signal. The digital interface transmitter (DI
T) 15 is a circuit for converting a digital audio signal into a DMI transmission code of CP-340 of EIAJ digital audio interface standard (DAI).

[0006] The receiver includes a DIR (digital interface receiver) 19 that receives and demodulates an input digital signal, and performs a decoding process or the like on the bit stream supplied from the DIR 19 in accordance with the signal system to perform a plurality of channel processes. And a mute circuit (mute circuit) 23 for preventing the output of the second signal processing circuit 21 from being output to a DAC (D / A converter) 25. It consists of. The DIR 19 demodulates the input modulated signal and converts the digital data to the second signal processing circuit 21 and the MPU 2
7 and a clock signal is generated and supplied to the MPU 27.

The second signal processing circuit 21 is a general PC
It has a DSP for PCM (digital signal processing circuit) for processing M signals and a DSP for DTS for processing DTS signals. The illustration of the PCM DSP and the DTS DSP is omitted. The DTS DSP decodes the DTS signal and outputs a multi-channel reproduction audio signal.
Construct a TS decoder. The digital interface receiver (DIR) 19 is a circuit that performs signal processing opposite to DIT on the received transmission code to demodulate the digital audio signal. The demodulated digital audio signal is transmitted to a second signal processing circuit. 21 and MPU2
7 and given.

The receiver further includes a bit pattern decision unit 2
9 and a microprocessor (MPU) 27 for controlling the entire PCM audio signal reproducing device 20. The bit pattern determiner 29 detects a specific bit pattern from the bit stream output from the DIR 19, and the MPU 27 supplies a reproduction mode signal to the second signal processing circuit 21 according to the result. The second signal processing circuit 21 sets the reproduction mode to the PCM mode or the D mode according to the reproduction mode signal.
The signal processing is performed in the TS mode. When the reproduction is started in response to the operation of the operator of the PCM audio signal reproducing apparatus, a mute signal for operating the mute circuit (mute circuit) 23 is supplied from the MPU 27 to the mute circuit (mute circuit) 23.

A plurality of channels of reproduced audio signals are output from a DAC (D / A converter) 25 according to the reproduction mode given to the second signal processing circuit 21. For example, if the playback mode is the PCM mode, a general 2-channel audio signal is output, and if the playback mode is the DTS mode, for example, a 5-channel surround audio signal is output.

[0010]

A playback mode (listening mode) indicating which method of decoding and reproducing a bit stream transmitting PCM data by signal processing or the like.
In addition to PCM mode and DTS mode, DOLB
There are Y DIGITAL mode and DVD mode. Here, general PCM mode and DTS mode are DIR1 mode.
9 will be described. When the playback mode is automatically or manually switched, if the playback mode is switched to a playback mode that does not conform to the method of the PCM data read from the recording medium or the PCM data input to the DIR 19 via the transmission path, the playback sound becomes a noise sound. Becomes

For this reason, since the non-audio flag is set in the DOLBY DIGITAL signal, the mute circuit 23 can instantaneously mute the signal and prevent the reproduction signal from being output. In DVD,
Since a predetermined flag is also present in the DTS signal, it is possible to easily determine whether the PCM data transmitted from the DVD device is of the DTS or of general PCM based on the presence or absence of the flag. However, in the case of a CD or LD, since the flag described above does not exist, the PCM data read by the reproducing apparatus is modulated by the DIT 15 into a signal conforming to the DAI standard, transmitted, and received by the DIR 19 to be demodulated. The determination unit 29 checks the presence or absence of the DTS header, and identifies whether the data is DTS PCM data.

In the bit stream output from the DIR 19, the DTS header signal is included every 1024 samples, and the time interval is about 1024/44100 when the sample frequency is 44.1 kHz.
It becomes 3.22 msec. DTS is included in PCM data.
Since a code sequence similar to the bit pattern defined as the bit pattern of the header is included, it is necessary to detect the DTS header twice consecutively to detect the DTS header reliably. It takes 48 msec, during which time it is unclear whether the input signal is for DTS or general PCM. Also, during unknown, the second
Normally, the reproduction mode of the signal processing circuit is on standby in the PCM mode. Therefore, when the PCM data input to the receiver is a DTS signal, the reproduction mode is set to DT.
Until switching to the S mode, there is a problem that a noise sound is output.

Further, in order to cope with the case where a recording medium in which general PCM data and DTS data are mixed is reproduced, when the DTS header signal is interrupted, the mode is switched from the DTS mode to the PCM mode. Also, in the case of a pause or track skip, noise is also generated when the reproduction is resumed immediately after receiving the DTS signal. If the DTS mode is fixed to the DTS mode after the DTS header signal is once detected, it is not possible to cope with the case of reproducing a recording medium in which general PCM data and DTS data are mixed as described above.

In order to solve the above problem, a conventional P
In the CM audio signal reproducing device, until the bit pattern decision unit 29 detects the DTS header twice consecutively,
Assuming that it is not clear which system the digital signal received by the DIR 19 is, the mute circuit (mute circuit) 23 is operated, and the output of the second signal processing circuit 21 is output from the DAC (D / A converter) 25 I was trying not to. As described above, it takes about 50 msec to detect the DTS header twice in succession, so that the reproduction signal of the audio data received during that time is D
There is a problem that the sound is not output from the AC (D / A converter) 25 and the sound is interrupted. Also, in order to reduce the sound interruption problem, if the mute operation time is shortened by, for example, detecting the DTS header only once, erroneous detection of the DTS header causes a change in the format at the start of reproduction or the digital signal. There is a problem that noise is easily generated in some cases.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a general PCM audio signal and D signal.
It is an object of the present invention to provide an audio signal reproducing apparatus capable of reproducing a TS signal and reducing the time of sound interruption at the time of starting reproduction or changing the system of a digital audio signal and making noise less likely to occur. .

[0016]

SUMMARY OF THE INVENTION A PCM audio signal reproducing apparatus according to the present invention has been made to solve the above-mentioned problems, and a first invention is an uncompressed PCM audio signal in a bit stream for transmitting PCM data. Data and DT
In an audio reproducing apparatus that automatically discriminates S-format compressed PCM audio data, performs signal processing in a signal processing circuit, and outputs a reproduced audio signal obtained by the signal processing, determines a bit pattern of the bit stream. A bit pattern determiner and a mute circuit for muting the reproduced audio signal; when the reproduction is started, the mute circuit is activated, and the bit pattern determiner converts the DTS synchronization signal and the DTS header signal from the bit stream within a predetermined time. Is detected, the reproduction mode of the signal processing is set to the DTS mode, the mute of the mute circuit is released, and if the DTS synchronization signal and the DTS header signal are not detected from the bit stream within the predetermined time, The playback mode of the signal processing is PCM
An audio signal reproducing apparatus is configured to release a mute of the mute circuit by setting a mode.

According to the present invention, when the bit stream is determined to be a general PCM signal or a DTS signal, the DTS
When the synchronization signal and the DTS header are detected within a predetermined time, it is determined that the signal is a DTS signal. In this determination method, erroneous determination can be prevented even if the number of times of detection of the synchronization signal or header related to the DTS is reduced, so that the time required for the determination can be reduced, and noise can be reduced at the time of starting reproduction or changing the digital audio signal system. Even if a mute having a time length corresponding to the determination time is operated to suppress the occurrence of the sound, the time of the mute operation can be shortened, so that the sound interruption is less likely to occur.

According to a second aspect of the present invention, in the PCM audio signal reproducing apparatus according to the first aspect, the predetermined time is substantially equivalent to one cycle of the DTS synchronization signal. .

According to the present invention, when the bit stream is determined to be a general PCM signal or a DTS signal, when the DTS synchronization signal and the DTS header are detected within a time period corresponding to substantially one cycle of the DTS synchronization signal. Is determined to be a DTS signal. In this determination method, the determination time required for the determination can be made shorter than the time corresponding to substantially one cycle of the DTS synchronization signal. Therefore, when a mute having a time length corresponding to the determination time is activated in order to suppress the generation of noise, the mute time can be shortened, and sound interruption does not easily occur.

According to a third aspect, in the audio signal reproducing apparatus according to the first or second aspect, the bit stream is data being read from a recording medium, and the reproduction mode is set to the PCM mode to be reproduced from the recording medium. During the operation, when the bit pattern determiner detects a DTS synchronization signal and a DTS header signal, the mute circuit is activated,
An audio signal reproducing device configured to release a mute of the mute circuit after switching a reproduction mode to a DTS mode.

According to the present invention, when reproducing a recording medium on which general PCM audio data and DTS data are recorded, when the read bit stream changes from general PCM data to DTS data, It is possible to make the generated noise and sound cut-out less noticeable.

According to a fourth aspect, in the audio signal reproducing apparatus according to the first or second aspect, the bit stream is data being read from a recording medium, and the reproduction mode is set to a DTS mode to be reproduced from the recording medium. DTS inside
When the synchronization signal and the DTS header signal are no longer detected, if the bit pattern determination unit detects audio data, the mute circuit is activated, the reproduction mode is switched to the PCM mode, and then the mute is released. FIG.

According to the present invention, when a recording medium on which general PCM audio data and DTS data are recorded is reproduced, the read bit stream is
It is possible to make noise and sound cutoff generated when data is changed to general PCM data less noticeable.

According to a fifth aspect of the present invention, in the audio signal reproducing apparatus according to any one of the first to fourth aspects, the bit pattern determination unit includes a predetermined bit pattern in a bit stream within the predetermined time. This is an audio signal reproducing apparatus that determines the presence or absence of a DTS synchronization signal and a DTS header depending on whether or not the audio signal is present.

According to the present invention, the DTS synchronization signal and the DTS header can be detected in a short time by comparing the pattern of the transmitted code string with a predetermined pattern.

According to a sixth aspect of the present invention, in the audio signal reproducing apparatus according to the first to fifth aspects, the bit pattern determiner includes a DTS synchronizing signal and a DTS within the predetermined time.
An audio signal reproducing apparatus which, when only one of the headers is detected, determines again whether or not a DTS synchronization signal and a DTS header exist within the predetermined time.

According to the present invention, a non-DTS signal is converted to a DTS signal by a bit pattern included in the signal.
Signal is erroneously determined, or the DTS signal is
The probability of erroneously determining a signal can be reduced.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION A PCM audio signal reproducing apparatus according to the present invention is characterized in that a bit stream read or transmitted from a recording medium is uncompressed PCM audio data or DTS compressed PCM audio data. Is an audio playback device that automatically determines whether or not the audio signal is a multi-channel playback audio signal obtained by the signal processing circuit, and outputs a multi-channel playback audio signal obtained by the signal processing. When the output is stopped by operating the circuit, and the DTS synchronization signal and the DTS header signal are detected from the bit stream within a predetermined time, the reproduction mode of the signal processing is set to DT.
In the S mode, the mute is released, and the DTS synchronization signal and the DTS
When the header signal is not detected, the reproduction mode of the signal processing is set to the PCM mode to release the mute.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram of a PCM audio signal reproducing apparatus to which the present invention can be applied.
This is the same as the block diagram of the audio signal reproducing device. In the present invention, the P shown in FIG.
The present invention can be applied to a CM audio signal reproducing device, or can be applied to a PCM audio signal reproducing device including the receiver shown in FIG. 6B and the reading device shown in FIG. 6A.

In the receiving apparatus (receiver) shown in FIG. 6B, the MPU 27 determines whether there is a demodulated audio signal in the signal supplied from the DIR 19, and determines whether to activate the mute circuit (mute circuit) 23. Used for When the output of DIR 19 is a PCM signal, MPU
Reference numeral 27 denotes a PCM mode as a reproduction mode signal to the second signal processing circuit 21, and a PCM D of the second signal processing circuit 21.
The SP outputs a reproduced audio signal with the input PCM data as it is or with a sound field effect added. Also, D
When the output of the IR 19 is a DTS signal, the MPU 27 gives the DTS mode as a reproduction mode signal to the second signal processing circuit 21, and the DTS DSP of the second signal processing circuit 21 performs DTS decoding processing on the input DTS signal. To output multi-channel playback audio signals.

FIG. 5 is a diagram showing the data structure of the DTS signal output from the DIR 19. As shown in FIG.
The DTS bit stream demodulated by the IR 19 is composed of audio frames of the same size, and each audio frame is a fixed-length DTS Sync Word (hereinafter referred to as DT).
S Sync or DTS synchronization signal).
This synchronization signal is formed by a specific bit pattern, and the cycle Ts is about 23.22 ms for a CD or LD. Immediately after the DTS Sync, there is a fixed-length DTS Header (DTS header) that transmits DTS auxiliary information such as the number of channels and the sampling frequency. The DTS Header is also formed by a specific bit pattern, but the specific bit pattern is not one type but one or more predetermined types.

The bit pattern determiner 29 detects a predetermined specific pattern from the bit stream provided from the DIR 19. When both the DTS Sync and the DTS Header are detected within a time period close to the DTS audio frame period Ts (23.22 ms) shown in FIG. 5, the MPU 27 converts the bit stream output from the DIR 19 into a DTS signal. Is determined, and the DTSSSync and the DTS Header are determined.
If at least one is not detected, the MPU
27 determines that the bit stream output from the DIR 19 is a general PCM signal. Basically MP
U27 sets the reproduction mode signal to the DTS mode when it is determined that the bit stream is a DTS signal,
When it is determined that the signal is a general PCM signal, the reproduction mode is set to the PCM mode.

The DTS cycle Ts is about 23.22 m in the case of reading data from a CD or LD.
It is about 10.67 msec for reading data from a DVD. In the second signal processing circuit 21, DTS is performed in accordance with the reproduction mode given from the MPU 27.
Either the DSP for PC or the DSP for PCM operates. DI
If the PCM data output from R19 is DTS PCM data, the second signal processing circuit 21 decodes the DTS signal with a DTS decoder.

FIG. 1 is a flowchart of a process when starting reproduction of an optical disk such as a CD. In each of the flowcharts described below, steps of “DTS Sync and Header detected?” Are scattered (S44, S56, S74, S86, S94).
And the DTS recording method in LD, the header is 10
Every 24 samples, the time interval is 1024/441 when the sample frequency is 44.1 kHz.
00 is about 23.22 msec, and about 24 hours at maximum to determine whether the DTS synchronization signal and the DTS header are detected.
This requires a determination time of about msec. Also, D
In VD, the sample frequency is 48 KHz and the DTS
The synchronization signal and the DTS header signal are included every 512 samples, and the cycle of the DTS synchronization signal and the DTS header signal is about 10.67 msec. Therefore, DVD
In this case, it takes about 11 msec at maximum to detect the DTS synchronization signal and the DTS header signal and determine the dts signal.

In the flowchart of FIG. 1, when the PCM audio signal reproducing apparatus starts reproducing the PCM audio signal, first, a mute circuit (mute circuit)
At 23, the mute is activated, and the reproduction mode is switched to the PCM mode (S40). Then, it waits for input of PCM data such as PCM data read from the optical disk (S41), and starts the timer as soon as the PCM data is input (S42), and measures the lapse of 25 msec (S41).
43). This 25 msec is the time when the DTS synchronization signal and the DT
It is set as the time required to read the S header signal once.

During the 25 ms, it is checked whether or not the DTS synchronization signal and the DTS header signal have been detected (S44).
When the S synchronization signal and the DTS header signal are detected,
After switching the reproduction mode to the DTS mode, the mute is released (S45), and the reproduction is performed in the DTS mode (S45).
46). On the other hand, during the period of 25 ms, the DTS
If the sync signal and DTS header signal are not detected,
The mute by the mute circuit (mute circuit) 23 is released (S47), and the reproduction is performed in the PCM mode (S4).
8).

FIG. 2 is a flowchart of a process during reproduction in the PCM mode. During playback in PCM mode,
Whether a DTS synchronization signal and a DTS header signal are detected (S
56) and whether or not PCM data has been input (S57) is continuously checked. When the DTS synchronization signal and the DTS header signal are detected, the mute is activated immediately, the reproduction mode is switched to the DTS mode, and then the mute is released (S66), and the reproduction is performed in the DTS mode (S46).
If the DTS synchronization signal and the DTS header signal are not detected and there is no data input, the timer is started (S5).
8) The progress of 5 seconds is measured (S59).

The 5 sec is set as a time slightly shorter than the time required when the optical disk to be reproduced is exchanged for another optical disk. That is, this 5 seconds
If no data is input during this time, it is determined that there is a possibility that the optical disk to be reproduced may be replaced with another optical disk, and the mute is activated (S61) to wait for input of PCM data from the replaced optical disk. State (S6
2). If the PCM data is input during the 5 seconds, it is determined that there is no possibility that the optical disk to be reproduced has been replaced instead of replacing the optical disk (S6).
0).

FIGS. 3 and 4 are flowcharts of the processing during reproduction in the DTS mode. During playback in DTS mode, D
Whether the TS synchronization signal and the DTS header signal are detected (S7
4) and whether or not PCM data is input (S75) is continuously monitored. If the DTS synchronization signal and the DTS header signal are not detected and there is no PCM data input, a timer is started (S76), 250 msec elapse is measured (S77), and the presence or absence of PCM data input within 250 msec is determined. Check (S78). 250 msec
Is set as the time during which the input of the DTS synchronization signal, the DTS header signal, and the PCM data is interrupted due to the operation of fast forward and fast reverse on the optical disk. If the input of the PCM data is resumed within the above 250 msec (S78), the DTS is executed for the operation of fast forward and fast reverse.
It is determined that the input of the synchronization signal, the DTS header signal, and the PCM data is temporarily interrupted, and the process returns to S74.

On the other hand, if the input of the PCM data is not resumed within the above 250 msec, the mute is activated, the timer is started (S79), and the lapse of 5 sec is measured again (S84). This 5 sec.
Similarly to 59, the time is set to be slightly shorter than the time required when the optical disk to be reproduced is changed to another optical disk. During the 5 seconds, the presence / absence of the detection of the DTS synchronization signal and the DTS header signal (S86) and the PCM
The presence / absence of data input (S88) is checked. If no DTS synchronization signal and DTS header signal are detected and no PCM data is input, it is determined that the optical disk to be reproduced may be replaced with another optical disk. The reproduction mode is switched to the PCM mode (S85), and the apparatus enters a state of waiting for input of data from the optical disc after the exchange (S62).

In step S86, within 5 seconds,
When the DTS synchronization signal and the DTS header signal are detected,
Since there is no possibility that the optical disk has been replaced with another optical disk, the mute is released (S87), and the process returns to S74. In step S86, the DTS synchronization signal and the DT
If at least one of the S header signals is not detected and PCM data is input, it is determined that verification is necessary and S92
Proceed to.

In FIG. 4, the processing in steps S92 to S97 is substantially the same as the processing in steps S42 to S47 shown in FIG. 1, and depends on whether the DTS synchronization signal and the DTS header signal have been detected within 25 msec. Then, it is determined whether the input PCM data is related to the PCM mode or the DTS mode, and the mode is set to the corresponding mode.
That is, in step S92, the timer is started and 25
The progress of msec is measured (S93). This 25mse
c is set to the same effect as 25 msec in step S43. The presence or absence of the detection of the DTS synchronization signal and the DTS header signal during 25 msec is detected (S9).
4) If detected, mute is released (S95),
Proceed to S74, and if not detected, change the playback mode to PCM.
The mode is switched to (S96), and the mute is released (S9).
7) Playback is performed in the PCM mode (S48).

In each of the above-mentioned flowcharts, "DTS Sync and Header detected?"
Steps (S44, S56, S74, S86, S9)
In 4), when the DTS synchronization signal and the DTS header are detected within the time corresponding to one cycle of the DTS synchronization signal, it is determined that the bit stream is a DTS signal. However, only one of the DTS synchronization signal and the DTS header may be detected. In that case, it is highly possible that the data is PCM data. However, just in case, the timer time is reset and the detection of the DTS synchronization signal and the DTS header is performed again within the time corresponding to one cycle of the DTS synchronization signal. If both are detected, it may be determined that the signal is a DTS signal.

As described in detail above, when a bit stream is determined to be a general PCM signal or a DTS signal, a conventional PCM audio signal reproducing apparatus uses a DTS signal.
When the header was detected twice consecutively, it was determined to be a DTS signal. For this reason, for example, D
For TS signals, a minimum of approximately 24 msec to a maximum of approximately 48 msec
The determination time of c is required, and when the reproduction is started or the digital audio signal format is changed, the sound cutoff occurs due to the mute corresponding to the determination time. Further, if the determination time is shortened in order to shorten the mute time, there is a problem that noise is likely to appear. In contrast, the PC of the present invention
According to the M audio signal reproducing apparatus, erroneous determination can be prevented even if the number of times of detection of the DTS header is reduced.
When the synchronization signal and the DTS header are detected once, it can be determined that the signal is a DTS signal. Therefore, for example, C
With the DTS signal recorded in D, the determination can be made with a maximum determination time of about 24 msec, and the time for activating the mute can be shortened. Therefore, there is an effect that sound interruption hardly occurs and noise hardly appears.

[Brief description of the drawings]

FIG. 1 is a flowchart of a process when starting reproduction of an optical disc such as a CD.

FIG. 2 is a flowchart of a process during reproduction in a PCM mode.

FIG. 3 is a first part of a flowchart of a process during reproduction in the DTS mode.

FIG. 4 is a second part of a flowchart of a process during reproduction in the DTS mode.

FIG. 5 is a diagram showing a data structure of a DTS signal output from DIR19.

FIG. 6 is a block diagram showing a general PCM audio signal reproducing apparatus.

[Explanation of symbols]

Reference Signs List 11 optical head 13 first signal processing circuit 15 DIT (digital interface transmitter) 19 DIR (digital interface receiver) 21 second signal processing circuit (signal processing circuit) 23 mute circuit (mute circuit) 25 DAC (D / A converter) 27 MPU (microprocessor) 29 bit pattern determiner

Claims (6)

[Claims] 1. A signal processing circuit for automatically discriminating between uncompressed PCM audio data and DTS-compressed PCM audio data in a bit stream transmitting PCM data, and performing signal processing by the signal processing circuit. An audio playback device that outputs a playback audio signal, comprising: a bit pattern determination unit that determines a bit pattern of the bit stream; and a mute circuit that mutes the playback audio signal. A bit pattern determiner converts the DTS synchronization signal and DT from the bit stream within a predetermined time.
When the S header signal is detected, the reproduction mode of the signal processing is set to the DTS mode, the mute of the mute circuit is released, and the DTS synchronization signal and the DTS header signal are not detected from the bit stream within the predetermined time. In this case, the audio signal reproducing apparatus is characterized in that a reproduction mode of the signal processing is set to a PCM mode and a mute of the mute circuit is released. 2. The audio signal reproducing apparatus according to claim 1, wherein the predetermined time is substantially equal to one of the DTS synchronization signals.
An audio signal reproducing apparatus, wherein the time is a time corresponding to a cycle. 3. The audio signal reproducing device according to claim 1, wherein said bit stream is data being read from a recording medium, and said bit stream is being reproduced from a recording medium by setting a reproduction mode to a PCM mode. When the pattern determination unit detects the DTS synchronization signal and the DTS header signal, the mute circuit is activated and the reproduction mode is set to D.
An audio signal reproducing apparatus, wherein the mute of the mute circuit is released after switching to the TS mode. 4. The audio signal reproducing apparatus according to claim 1, wherein the bit stream is data being read from a recording medium, and the reproduction mode is set to a DTS mode, and the DTS synchronization signal is reproduced during reproduction from the recording medium. And D
When the TS header signal is no longer detected, if the audio data is detected by the bit pattern determiner, the mute circuit is activated, the reproduction mode is switched to the PCM mode, and then the mute is released. Audio signal playback device. 5. The audio signal reproducing apparatus according to claim 1, wherein the bit pattern determination unit determines whether a bit stream within the predetermined time includes a predetermined bit pattern. An audio signal reproducing apparatus characterized in that the presence / absence of a DTS synchronizing signal and a DTS header is determined by the following. 6. The audio signal reproducing apparatus according to claim 1, wherein the bit pattern determination unit detects only one of a DTS synchronization signal and a DTS header within the predetermined time. In such a case, an audio signal reproducing apparatus characterized in that the presence or absence of a DTS synchronization signal and a DTS header is determined again within the predetermined time.