JP3538024B2 - PCM audio signal playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PCM audio signal reproducing apparatus capable of switching an audio reproduction mode between a PCM mode and a dts mode for reproduction.

[0002]

2. Description of the Related Art dts (= digital heat)
er systems) is a method of compressing and recording a multi-channel audio signal, and is adopted not only for DVD but also for CD and LD as a recording method.
CD and, dts signals recorded on the LD, in order to ensure the reading of at flops Reya with traditional, normal P
Recorded in CM.

[0003]

The sound reproduction mode (= listening mode) includes DOLBY DIGITAL in addition to PCM and dts. When switching these sound reproduction modes automatically or manually, switching to the wrong sound reproduction mode causes a noise sound. On the other hand, since the non-audio flag is set in the DOLBY DIGITAL signal, the mute can be instantaneously applied. In the case of a DVD, since a predetermined flag is also present in the signal of dts, whether the PCM data from the DVD is dts or normal PCM can be identified by the presence or absence of the flag. However, in a CD or LD, such a flag does not exist, so that the dts decoder signal built in the receiver reads the dts header signal from the PCM data read by the player, and determines whether the data is dts PCM data. . The dts header signal is included every 1024 samples, and the time interval is 1 when the sample frequency is 44.1 kHz.
It was about 23.22 msec on 024/44100. d
If the header is read twice to detect the ts header, it takes 24 to 48 msec, during which time it is unknown whether the input signal is of dts or normal PCM. Since it is normal to wait in the PCM mode, if the input PCM data is dts, until the sound reproduction mode is switched to the dts mode,
Noise noise is output. Furthermore, in order to cope with switching to a disc having a different audio reproduction mode, if the dts header signal is interrupted, the mode is switched from the dts mode and is usually switched to the PCM mode. In such a case, a noise sound is generated when the next reproduction is restarted. Once the dts header signal is detected, if it is fixed to the dts mode, it is not possible to cope with the continuous reproduction of a plurality of discs in different modes.

According to the description in Japanese Patent Application Laid-Open No. 8-36829, a mute is applied during a search in an optical disk reproducing apparatus in order to prevent noise sound output during the search. According to Japanese Patent Application Laid-Open No. 5-2816, during reproduction of an optical disk in which an audio signal and a data signal are mixed, it is possible to mute that a data signal is output as a sound at the time of track switching and noise noise is generated. Activate,
Avoided. According to the description of Japanese Patent Application Laid-Open No. Hei 5-114868, along with the switching of the reproduction mode, the data read out during the reproduction mode before the switching and remaining in the buffer are invalidated, and the audio output based on the data is not performed. At the same time, mute is applied until the data read in the playback mode after switching is decoded and a state in which sound can be output. According to the description in Japanese Patent Application Laid-Open No. 7-312014 , an audio CD and a CD-ROM
When a CD-ROM is set in a playback device capable of reproducing both of them, the mute is activated so that sound is not output. None of the prior arts mentions a problem caused by switching between the PCM mode and the dts mode read by common PCM data and a solution to the problem.

It is an object of the present invention to provide a PCM audio signal reproducing apparatus which can overcome the above-mentioned problems.

[0006]

According to the PCM audio signal reproducing apparatus (10) of the present invention, the mute is activated in the state of waiting for input of PCM data from the audio recording medium (S4).
0: Indicates a step number in a flowchart described later. same as below. ), With the start of PCM data input,
The elapse of the first predetermined time is measured (S43), and when the dts header signal is detected within the first predetermined time (S43).
44 → S45), the mute is released in the dts mode (S45), and if no dts header signal is detected within the first predetermined time (S43 → S47), the mute is released in the PCM mode (S47). ).

The state of waiting for input of PCM data from the audio recording medium is, for example, when reproduction of the audio recording medium is started.
Further, when the audio recording medium to be reproduced is exchanged and PCM data from the exchanged audio recording medium is waiting (S6).
2) is also included. Audio recording media include, for example, CDs and L
D is included. In the DVD, since a predetermined flag is also present in the signal of dts, it is possible to immediately identify whether the PCM data from the DVD is dts or normal PCM by the presence or absence of the flag. , Dts header signal is included at a predetermined cycle, and the present invention is applicable also when the audio recording medium is a DVD.

[0008] In the period waiting for input of the PCM data from the audio recording medium by activating the mute, it may be in the audio reproduction mode to the PCM mode (S40), may be in the audio reproduction mode to the dts mode . “In the dts mode state” and “in the PCM mode state” of “Unmute in dts mode state” and “Unmute in PCM mode state” mean that the audio playback mode is set to dts immediately before mute cancellation. Mode or PCM mode to switch to that state, or immediately after the mute is activated, the audio playback mode may be switched to the dts mode or PCM mode in advance, and the mute may be released in that state. .

When the dts header signal is detected within the first predetermined time, the number of times the dts header signal is detected is not limited to one time, but it may be two or more times such as two times in order to increase the detection accuracy. This includes some cases.

[0010] The mute is activated until the input of PCM data from the audio recording medium is awaited, and the input of PCM data from the audio recording medium is started and the audio reproduction mode is switched to the corresponding mode for input PCM data. Therefore, output of noise sound due to an error in the audio reproduction mode is prevented. Then, the output of the sound is started in a state where the mode is switched to the appropriate sound reproduction mode. In this way, it is possible to quickly perform reproduction in an appropriate audio reproduction mode while preventing output of noise sound due to an error in the audio reproduction mode.

According to the PCM audio signal reproducing apparatus (10) of the present invention, when the audio reproducing mode is set to the PCM mode and the dts header signal is detected while reproducing the audio recording medium (S5).
6 → S66), the mute is activated (S66), and the sound reproduction mode is switched to the dts mode (S66).
The mute is released (S66).

When the dts header signal is detected during reproduction of the audio recording medium by setting the audio reproduction mode to the PCM mode, it means that the selection of the audio reproduction mode is erroneous. Since the noise sound is output, the mute is activated to avoid outputting the noise sound. Then, after the sound reproduction mode is set to the dts mode, that is, after switching to the appropriate sound reproduction mode, the mute is released, whereby the reproduction in the dts mode is performed.

According to the PCM audio signal reproducing apparatus (10) of the present invention, while reproducing the audio recording medium by setting the audio reproducing mode to the PCM mode, the second predetermined signal is input after the PCM data input from the audio recording medium is interrupted. The passage of time is measured (S5
9) If PCM data is not input during the second predetermined time (S59 → S61), mute is activated (S61), and a state of waiting for input of PCM data from the audio recording medium (S62). .

When the audio recording medium set for reproduction is exchanged by manual operation or automatic operation by a changer, the audio recording medium before exchange and the audio recording medium after exchange can be read as PCM data. Nevertheless, the audio recording method is changed from PCM mode compatible to d.
In some cases, the ts mode has been changed. The second predetermined time is the time required for replacing the audio recording medium (eg,
5 sec), when the sound reproduction mode is exchanged, the mute is activated and the PCM data input wait state is set. Therefore, the recording method of the sound recording medium after the exchange is changed from the PCM mode correspondence. Even when trying to switch to the dts mode, it is possible to cope with noise sound output prevention due to an error in the audio reproduction mode at the start of the next reproduction.

According to the PCM audio signal reproducing apparatus (10) of the present invention, when the audio recording mode is set to the dts mode and the audio recording medium is reproduced, the dts header signal is not detected and the PCM audio signal is reproduced.
When the input of the M data is stopped (S74, S75 → S7)
6. The elapse of the third predetermined time is measured (S77). If PCM data is input from the audio recording medium within the third predetermined time (S78 → S74), the dts mode is maintained.

If a fast forward or fast reverse operation is performed during reproduction in the dts mode, detection of the dts header signal is temporarily interrupted. However, a third predetermined time (eg, 250 ms)
If PCM data is input in ec), temporary dt
It is determined that the interruption of the detection of the s header signal is not caused by the exchange of the audio recording medium, but is caused by the fast forward or the fast reverse. Therefore, even if the detection of the dts header signal is interrupted, if the PCM data from the audio recording medium is input within the third predetermined time, the PCM data is converted into the dts mode PCM data without any trouble in the dts mode. Can be played.

According to the PCM audio signal reproducing apparatus (10) of the present invention, the third predetermined time is equal to the PCM audio signal from the audio recording medium.
If no data is input (S77 → S7)
9) While the mute is activated (S79), a fourth predetermined time is measured (S84), and the dts header signal is not detected within this fourth predetermined time, and the input of PCM data from the audio recording medium is also stopped. If not (S84 → S85),
Waits for PCM data from the audio recording medium (S
85 → S62).

If no PCM data is input within the third predetermined time, it is determined that the interruption of the dts header signal this time is not a temporary interruption due to a fast-forward or fast-return operation. Then, a fourth predetermined time thereafter (eg, 5 sec.)
If the PCM data is not input in c), the audio recording medium is replaced, and in the replaced audio recording medium, the PCM recording method may be changed from the dts mode to the PCM mode. While holding the state, the apparatus enters a state of waiting for input of PCM data from the audio recording medium.

According to the PCM audio signal reproducing apparatus (10) of the present invention, the third predetermined time is equal to the PCM audio signal from the audio recording medium.
If no data is input (S77 → S7)
9) While the mute is activated (S79), a fourth predetermined time is measured (S84), and if the dts header signal is detected within the fourth predetermined time, the mute is released (S87).

If the dts header signal is detected within the fourth predetermined time, it is determined that the audio recording medium being reproduced is not set and is kept in the set state without being replaced. (S87), and by continuing the dts mode (S87 → S74), appropriate reproduction can be performed.

According to the PCM audio signal reproducing apparatus (10) of the present invention, when the dts header signal is not detected within the fourth predetermined time and PCM data is input (S88 →
(S92), a fifth predetermined time (for example, 50 msec) is measured (S93), and if a dts header signal is detected within the fifth predetermined time (S94 → S95), mute is performed in the dts mode. Release (S95), and if no dts header signal is detected (S93 → S96), the PC
In the state of the M mode (S96), the mute is released (S96).
97).

When the dts header signal is not detected within the fourth predetermined time and PCM data is input, it is uncertain whether the PCM data being input is of the PCM mode or of the dts mode. Then, the fifth predetermined time is measured, and the presence or absence of the detection of the dts header signal within the fifth predetermined time clarifies the dts header signal. Playback without sound generation can be performed.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a receiver 10 with built-in dts.
FIG. 4 is a block diagram of a portion related to processing of PCM data of FIG.
The digital audio input signal is DIR (Digit
al Interface Register) 11 and the analog audio input signal is A / D
A / D conversion is performed at (Analog / Digital) 12 and then input to DIR 11. The DIR 11 selects one input terminal from a plurality of digital input terminals by a control signal from the control microcomputer 18, generates a clock signal from the input signal of the selected input terminal, and converts the clock signal into a data signal. (Data) output together with the signal. The data signal from the DIR 11 is supplied to the one-shot circuit 13 and the PCM DSP (Digital Sign).
al Processor) 16 and DSP17 for dts
And the clock signal from DIR11 is DSM for PCM
It is sent to P16 and DSP 17 for dts.

FIG. 2 shows the input (in) of the one-shot circuit 13.
5 is a timing chart of the output (out). one
When a pulse is input, the shot circuit 13 outputs a rising pulse at the rising edge. The fall of the output pulse is 10m from the fall of the last input pulse.
It will be after sec.

When the output of the one-shot circuit 13 is “1”, the control microcomputer 18 reads the P from the optical disc such as a CD.
It is determined that there is input of CM data, and if it is “0”, it is determined that input of PCM data from the optical disk has been interrupted. The PCM DSP 16 outputs the input PCM data as it is or with an added sound field effect.
When reading data from a CD or LD, the dts DSP 17 outputs a dts header signal of about 23.22 msec.
If the data is read twice at intervals, it is determined that a dts header signal has been detected, and the input PCM data is determined to be dts PCM data. In reading data from the DVD, if the dts header signal is read twice at an interval of about 10.67 msec, it is determined that the dts header signal has been detected, and the input PCM data is determined to be dts PCM data. And a PC whose input signal is dts
If the data is M data, “H” is output to the dts detection port, and the PCM data is decoded by dts. The control microcomputer 18 exchanges data with the main microcomputer 19, and when the dts detection port of the dts DSP 17 is "L" and "H", the PCM DSP
Input from 16 and dts DSP 17 is clock selector
A control signal is sent to the clock selector 24 and the data selector 25 so as to be selected by the data selector 24 and the data selector 25. The post processor DSP 26 has a clock selector 24
And data are input from the data selector 25 and BASS MANAGEMENT, DEL
AY, mute and other processing are performed, and D / A (Dig)
ital / Analog) 27. The D / A 27 converts an input into an analog signal and outputs it.

FIG. 3 is a flowchart of a process when starting reproduction of an optical disk such as a CD. It should be noted that in the flowchart, the steps of “detection of dts?” Are scattered (S44, S56, etc.), but in the dts recording method for CD or LD, the header is included every 1024 samples, and The interval is 4 for the sample frequency.
In the case of 4.1 kHz, about 23.
22 msec. If the dts header signal is detected when the header can be read twice to detect the dts header, the detection of the presence / absence of the dts header signal is performed in 24 to 48 m.
It takes a time of sec. In DVD,
The sample frequency is 48 KHz, the dts header signal is included every 512 samples, and the time interval between the dts header signals is about 10.67 msec. Therefore, in the case of a DVD, the time required to read the header twice is 11 to 22 msec. First, the mute is activated, and the sound reproduction mode is switched to the PCM mode (S4).
1). Waiting for input of PCM data from the optical disk (S41), as soon as PCM data is input, the timer is started (S42), and the lapse of 50 msec is measured (S43). This 50 msec is set as a time required for reading the dts header signal twice. During 50 ms, it is checked whether or not a dts header signal has been detected (S44). If a dts header signal has been detected, the sound reproduction mode is switched to the dts mode, and the mute is released (S45). The reproduction is performed in the mode (S46). On the other hand, if no dts header signal is detected during the period of 50 ms, the mute is released (S47), and as a result, reproduction is performed in the PCM mode (S48).

FIG. 4 is a flowchart of a process during reproduction in the PCM mode. While playing back in PCM mode, constantly d
The presence / absence of the detection of the ts header signal (S56) and the presence / absence of the input of the PCM data (S57) are continuously checked. dt
When the s header signal is detected, the mute is activated immediately, the sound reproduction mode is switched to the dts mode, then the mute is released (S66), and the reproduction is performed in the dts mode (S46). No dts header signal is detected,
If there is no data input, the timer is started (S
58) The progress of 5 seconds is measured (S59). This 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, if no data is input during the 5 seconds, it is determined that there is a possibility that the optical disk to be reproduced may be replaced with another optical disk, the mute is activated (S61), and the PCM data from the replaced optical disk is (S62). If the PCM data is input during the 5 seconds, it is not an optical disc exchange, and it is determined that there is no possibility that the reproduced optical disc has been exchanged, and the process returns to S56.

FIGS. 5 and 6 are flowcharts of the processing during reproduction in the dts mode. During playback in dts mode, d
The presence / absence of the detection of the ts header signal (S74) and the presence / absence of the input of the PCM data (S75) are continuously monitored. dt
If the s header signal is not detected and no PCM data is input, the timer is started (S76), the elapse of 250 msec is measured (S77), and the PC within 250 msec is measured.
It is checked whether M data has been input (S78). 250ms
ec is set as a time during which the input of the dts header signal and the PCM data is interrupted for the operation of fast forward and fast reverse on the optical disc. This 250mse
If the input of PCM data is resumed in c, the detection of the dts header signal and the PC
It is determined that the input of the M data is temporarily interrupted, and the process returns to S74. On the other hand, this 250msec
If the input of the PCM data is not resumed within the period, the mute is activated, the timer is started (S79), and the data is newly set for 5 seconds.
Is measured (S84). This 5 sec.
Similarly to the above, the time is set to be slightly shorter than the time required when the optical disk to be reproduced is exchanged for another optical disk. During this 5 sec, the presence or absence of the detection of the dts header signal (S86) and the presence or absence of the input of the PCM data (S86)
If no dts header signal is detected and no PCM data is input, it is determined that the optical disk to be reproduced may be replaced with another optical disk, and the audio reproduction mode is switched to the PCM mode (S85). ), And waits for input of data from the replaced optical disk (S6).
2). If the dts header signal is detected within 5 seconds, it is determined that 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. Although no dts header signal is detected within 5 seconds, if PCM data is input, it is determined that verification is necessary, and the process proceeds to S92.

The processing in S92 to S97 is performed in S42 to S47.
The processing is almost the same as Based on the detection of the dts header signal within 50 msec,
It is determined whether the mode is related to the M mode or the dts mode, and the mode is set to the corresponding mode. That is, in S92, the timer is started and the elapse of 50 msec is measured (S93). This 50 msec is the 50 msec of S43.
It is set for the same purpose as c. The presence or absence of the detection of the dts header signal during 50 msec is detected (S9).
4) If detected, mute is released (S95),
Proceed to S74, and if not detected, set the audio playback mode to P
The mode is switched to the CM mode (S96), the mute is released (S97), and the reproduction is performed in the PCM mode (S48).

[Brief description of the drawings]

FIG. 1 is a block diagram of a portion related to processing of PCM data of a receiver with a built-in dts.

FIG. 2 is a timing chart of input and output of the one-shot circuit.

FIG. 3 is a flowchart of a process when starting reproduction of an optical disc such as a CD.

FIG. 4 is a flowchart of a process during reproduction in a PCM mode.

FIG. 5 is a first part of a flowchart of a process during reproduction in the dts mode.

FIG. 6 is a second part of a flowchart of a process during reproduction in the dts mode.

[Explanation of symbols]

10 dts built-in receiver (PCM audio signal playback device)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-64199 (JP, A) JP-A-9-294077 (JP, A) JP-A-7-23491 (JP, A) JP-A-6-29491 132912 (JP, A) JP-A-7-262711 (JP, A) JP-A-2-84171 (JP, U) JP-A-2-81600 (JP, U) Table 2001-505348 (JP, A) ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 20/00-20/16 351 G10L 11/00-19/00

Claims (7)

(57) [Claims] In a state of waiting for input of PCM data from an audio recording medium, a mute is activated, and the elapse of a first predetermined time is measured with the start of input of PCM data. When the dts header signal is detected, the mute is released in the dts mode, and when the dts header signal is not detected within the first predetermined time, P
A PCM audio signal reproducing device, wherein mute is released in a CM mode. 2. When the audio recording mode is set to the PCM mode and the audio recording medium is reproduced , dts is included in the reproduced PCM data.
When a header signal is detected, the PCM audio signal reproducing device activates a mute, switches the audio reproduction mode to the dts mode, and then releases the mute. 3. When the sound reproduction mode is set to the PCM mode and the sound recording medium is reproduced, a second predetermined time is measured after the input of the PCM data from the sound recording medium is stopped, and the second predetermined time is measured. If no PCM data is input during the time, the mute is activated and the P
P which is in a state of waiting for input of CM data
CM audio signal playback device. 4. When the dts header signal is not detected and no PCM data is input during the reproduction of the audio recording medium by setting the audio reproduction mode to the dts mode, the elapse of a third predetermined time is measured. A PCM audio signal reproducing apparatus that maintains dts mode when PCM data is input from an audio recording medium within a predetermined time. 5. When the third predetermined time elapses without input of PCM data from the audio recording medium, mute is activated, and a fourth predetermined time is measured. 5. The PCM audio signal reproducing apparatus according to claim 4, wherein when no dts header signal is detected and no PCM data is input from the audio recording medium, a standby state of PCM data from the audio recording medium is entered. . 6. When the third predetermined time has elapsed without input of PCM data from the audio recording medium, the mute is activated, and a fourth predetermined time is measured. 6. The PCM audio signal reproducing apparatus according to claim 4, wherein the mute is released when a dts header signal is detected. 7. When a dts header signal is not detected within a fourth predetermined time and PCM data is input, a fifth predetermined time is measured, and dts is measured within the fifth predetermined time.
7. The mute is released in a dts mode when a header signal is detected, and the mute is released in a PCM mode when a dts header signal is not detected. PCM audio signal playback device.