JP3576841B2 - PCM audio signal playback device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a PCM audio signal reproducing apparatus capable of switching a listening mode to a PCM mode and a dts mode for reproduction.
[0002]
[Prior art]
The dts (= digital theater systems) is a method of compressing and recording a multi-channel audio signal, and is adopted as a recording method for not only DVDs but also CDs and LDs. The PCM audio signal of dts recorded on a CD or LD is a normal PCM (hereinafter, “normal PCM” and “normal PCM audio signal”) in order to ensure reading by a conventional player. , Non-dts PCM and non-dts PCM audio signals).
[0003]
[Problems to be solved by the invention]
In the listening mode, in addition to PCM and dts, there is also DOLBY DIGITAL. When these listening modes are automatically or manually switched, a noise sound is generated when a dts PCM audio signal is reproduced in the PCM mode. 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 also exists in the signal of dts, it is possible to identify whether the PCM audio signal from the DVD is of the dts signal or of the normal PCM by the presence or absence of the flag. However, since such a flag does not exist in CDs and LDs, it is necessary to read out a dts header of a PCM audio signal read from a player by a dts decoder built in a receiver and identify whether or not the signal is a dts PCM audio signal. become. The dts header is included in each of A samples (for A, see the description of the embodiment of the invention described later), and the time interval is such that the sampling frequency is C2 kHz (for C2, the embodiment of the invention is described later). In the case of the form (see note of form), A / C2 is about D4 ms (for D4, see the note of the embodiment of the invention described later). If the header is read twice to detect the dts header, it takes D5 to D6 ms (for D5 and D6, see the notes of the embodiment of the invention described later), during which time the data is input from the optical disc. It is unclear whether the PCM audio signal is a normal PCM audio signal or a dts PCM audio signal, and it is normal to wait in the PCM mode while the PCM audio signal is unknown, so that the PCM audio signal is a dts PCM audio signal. In this case, a noise sound is output from the speaker until the listening mode is switched to the dts mode. Furthermore, in order to cope with switching to a disc having a different listening mode, if the PCM audio signal is interrupted, the system switches from the dts mode and switches to the normal PCM mode. However, a noise sound is generated when the next reproduction is restarted. Once the dts header is detected, if the mode is fixed to the dts mode, it is not possible to cope with continuous playback of a plurality of discs in different modes.
[0004]
According to the description in Japanese Patent Application Laid-Open No. 8-36829, mute is applied during the search in order to prevent noise sound output during the search in the optical disc reproducing apparatus. 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 to avoid. 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. JP-A-7-312014 According to the description of the gazette, in a reproducing apparatus capable of reproducing both an audio CD and a CD-ROM, when a CD-ROM is set, a mute is activated so that sound is not output. None of the prior art mentions the problems arising from the choice of PCM mode and dts mode for common PCM audio signals and their solutions.
[0005]
For this reason, the applicant has filed Japanese patent application No. 10-139203 (at the time of this application, an unknown technique before the application was published), when it is unknown whether the PCM audio signal from the audio recording medium is a normal PCM audio signal or a dts PCM audio signal, mute is performed. After the input of the PCM audio signal is started, the system waits for a predetermined period of time. If a dts header is input during that time, the mute is released with the listening mode set to the dts mode. If the dts header is not input, the PCM Mute is released in the mode. Further, when the PCM audio signal is interrupted from the audio recording medium, the audio recording medium may be replaced with an audio recording medium having a different listening mode. Therefore, the mute is activated, and the PCM audio signal from the audio recording medium is awaited.
[0006]
When the PCM audio signal is interrupted from the audio recording medium, the PCM audio signal is input to the one-shot circuit. When the PCM audio signal is continuously input, the output of the one-shot circuit is maintained at "1". If the input is interrupted, the output of the one-shot circuit becomes “0”. If the PCM audio signal is interrupted when the output becomes “0”, it is necessary to add the one-shot circuit as a component.
[0007]
During the mute operation, when the input of the PCM audio signal from the audio recording medium is started, the presence or absence of the input of the dts header within a predetermined time from that time is detected, and the PCM audio signal from the audio recording medium is changed to the dts PCM audio signal. Whether the signal is a signal or a normal PCM audio signal is detected. However, since the sampling frequency differs depending on the type of the audio recording medium, depending on the value of the predetermined time, the audio recording medium having a high sampling frequency is truncated and the sampling frequency is low. Noise occurs in the audio recording medium.
[0008]
An object of the present invention is to provide a PCM audio signal reproducing apparatus which can overcome the above-mentioned problems.
[0009]
[Means for Solving the Problems]
According to the PCM audio signal reproducing apparatus (10) of the present invention, a pulse in a predetermined direction is detected for a PCM audio signal from an audio recording medium during audio reproduction, and a timer on a program is reset for each detection. At the same time, the measurement of the elapsed time from the reset time is started by the timer, and when the measured value of the elapsed time by the timer becomes equal to or longer than the first predetermined time, it is determined that the PCM audio signal from the audio recording medium has been interrupted, When the listening mode is set to the PCM mode or the dts mode and during the sound reproduction, when it is determined from the measurement of the timer that the PCM sound signal from the sound recording medium has been interrupted, the input of the PCM sound signal within the second predetermined time from the judgment time point Judgment was made, and if there was no input, mute was activated.
[0010]
The audio recording medium includes, for example, all audio recording media such as CDs, LDs, DVDs, and the like, such as optical disks and magnetic tapes on which audio is recorded. A DVD has video recorded in addition to audio, but since it contains at least audio, it is included in the audio recording medium referred to herein. In the case of a DVD, a predetermined flag is present in the case of dts. Therefore, the presence or absence of the flag makes it possible to immediately identify whether the PCM audio signal from the DVD is a dts PCM audio signal or a normal PCM audio signal. Since the audio signal also includes the dts header, the present invention can be applied and the DVD is not excluded from the audio recording medium.
[0011]
The pulse edge of the PCM audio signal has a rising edge and a falling edge, and the edge in the predetermined direction is one of the rising edge and the falling edge of the pulse.
[0012]
The first predetermined time and the second predetermined time respectively correspond to t1 and E in an embodiment of the present invention described later.
[0013]
The timer on the program is reset every time the pulse of the PCM audio signal from the audio recording medium rises or falls, and measures the time elapsed since the reset. When the PCM audio signal from the audio recording medium continues, the timer on the program is reset frequently, and the measured value does not reach the first predetermined time. On the other hand, when the PCM audio signal from the audio recording medium is interrupted, the timer in the program reaches the first predetermined time or more without being reset. In this way, the interruption of the PCM audio signal from the audio recording medium can be detected by omitting the one-shot circuit.
[0014]
The interruption of the PCM audio signal from the audio recording medium occurs when the audio recording medium is fast-forwarded, rewinded, stopped, paused, or replaced with an audio recording medium. If the PCM audio signal from the audio recording medium is not input within the lapse of the second predetermined time after determining that the PCM audio signal from the audio recording medium has been interrupted, it is assumed that the audio recording medium will be replaced. . When the audio recording medium is replaced, the listening mode of the audio recording medium may be changed. Therefore, when the second predetermined time elapses without the input of the PCM audio signal, the mute is activated, and when the PCM audio signal input is suddenly restarted, noise is generated from the audio generator such as a speaker or a headphone. Prevent from leaving.
[0015]
It is determined that the PCM audio signal from the audio recording medium has been interrupted, and if there is an input of the PCM audio signal from the audio recording medium within a lapse of a second predetermined time, the PCM audio signal from the audio recording medium is output. The interruption time is assumed to be short, such as fast forward or fast reverse. In such a case, the audio recording medium is kept as it is, so that it is unnecessary to change the listening mode. Therefore, when the PCM audio signal is input before the second predetermined time elapses, the PCM mode or the dts mode is continuously maintained.
[0016]
According to the PCM audio signal reproducing apparatus (10) of the present invention, the PCM audio signal from the audio recording medium being reproduced is input to the edge interrupt port of the control microcomputer (14), and the control microcomputer (14) An interrupt is generated at each edge of the input pulse to the predetermined direction, and the timer is reset at each interrupt.
[0017]
The control microcomputer (14) detects the edge occurrence time of the pulse of the PCM audio signal based on the input to the edge interrupt port.
[0018]
According to the PCM audio signal reproducing apparatus (10) of the present invention, when the PCM audio signal is input in a state of waiting for the input of the PCM audio signal from the audio recording medium while operating the mute, the PCM audio signal is output. And sets a third predetermined time that differs for each sampling frequency, and sets the listening mode to dts mode and PCM mode based on the presence or absence of a dts header from the start of input of the PCM audio signal to the elapse of the third predetermined time. Mute is released in mode. Note that the “sampling frequency” referred to here may be called “frame frequency”, but have the same value.
[0019]
The third predetermined time corresponds to D1, D2, and D3 in an embodiment of the present invention described later.
[0020]
In general, the case where the mute is activated is a case where it is unknown whether the listening mode of the audio recording medium is a normal PCM mode or a dts mode. When the PCM audio signal is input while the mute is activated and the PCM audio signal is input from the audio recording medium, the sampling frequency is detected from the PCM audio signal. In dts, the number of samples to which one sample with a dts header is inserted is determined, and this ratio is not related to the type of the audio recording medium. However, since the sampling frequency varies depending on the type of the audio recording medium, it is necessary to read a predetermined number of dts headers in order to read the dts header once or to read a plurality of times such as two times for reliability. The appropriate time differs for each sampling frequency of each audio recording medium. If the time D required to read a predetermined number of dts headers is uniformly set irrespective of the type of the audio recording medium, the time D becomes longer than necessary for the audio recording medium having a large sampling frequency, and the time D becomes longer than necessary. If the mute is released after the elapse, the dts header is truncated. On the other hand, in an audio recording medium with a small sampling frequency, the time D is set to be shorter than the required time, and the mute is released before the dts header is read. Noise appears. In the PCM audio signal reproducing device (10), the time taken from the start of input of the PCM audio signal to the reading of the dts header is set in relation to the sampling frequency of the PCM audio signal. Or a dts PCM audio signal can be identified in a required minimum time, and it is possible to prevent the occurrence of a truncation or noise at the time of mute release.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
[Notes on signs]: In the following description, various predetermined values are indicated by signs, and the definitions of the signs are as follows.
t1: In FIG. 2, when the predetermined time t1 elapses without occurrence of the next interrupt from the time of occurrence of the interrupt, it is determined that the PCM audio signal from the source device has been interrupted. Unit ms. Three digits above the decimal point.
t2: The one-shot circuit 19 in FIG. 5 switches the output from "1" to "0" when the predetermined time t2 elapses without the next input pulse coming from the fall of the input pulse. Unit ms. Two digits above the decimal point.
A: A dts PCM audio signal contains a dts header at a rate of one sample to A samples. Four digit integer.
C1: Sampling frequency of PCM audio signal of DVD recording audio in dts format. Unit kHz. Two digits after the decimal point.
C2: sampling frequency of PCM audio signal of CD or LD recording audio in dts format. Unit kHz. Two digits after the decimal point. C2 <C1.
D1: Time required to read out two samples with dts header when the sampling frequency is C1. Unit ms. Two digits after the decimal point.
D2: Time required to read out two samples with dts header when the sampling frequency is C2. Unit ms. Two digits after the decimal point. D2> D1.
D3: Time required to read out two samples with dts header when the sampling frequency is C3 (C3 <C2 <C1). Unit ms. Two digits after the decimal point. D3>D2> D1.
D4: numerical value obtained by rounding off A / C 2 kHz to the third decimal place. Unit msec. Number with two decimal places and two decimal places.
D5: Numerical value obtained by rounding up D4 after the decimal point. Unit ms. Two digits after the decimal point.
D6: A value twice as large as D5. Unit ms. Two digits after the decimal point.
E: A time set as a possibility that the user may have exchanged the optical disk of the player when this time E or more has elapsed since it was determined that the data was interrupted. Unit seconds. One digit above the decimal point. For example, 5 seconds.
[0023]
FIG. 1 is a block diagram of a part of the PCM / dts receiver 10 relating to processing of a PCM audio signal. A digital audio input signal is directly input to a DIR (Digital Interface Register) 11, and an analog audio input signal is A / D converted in an A / D (Analog / Digital) converter 12 and then input to the DIR 11. You. Source devices such as a CD player, an LD player, and a DVD player have their output terminals connected to the digital input terminals of the DIR 11. Which input terminal the DIR 11 selects, including the input from the A / D converter 12, is determined by a control signal from the control microcomputer 14. The DIR 11 generates a clock pulse from an input signal, and outputs the clock pulse and a PCM audio signal (denoted as DATA in the drawing). The data signal from the DIR 11 is input to a DSP (Digital Signal Processor) 13 for PCM / dts, which also serves as PCM and dts, and a control microcomputer 14.
[0024]
FIG. 2 shows the relationship between the input of a PCM audio signal to the edge interrupt port of the control microcomputer 14 of FIG. The control microcomputer 14 receives the data signal from the DIR 11 into the edge interrupt port, and generates interrupts (1), (2), and (3) when the input pulse to the edge interrupt port rises. The control microcomputer 14 detects the presence or absence of data based on these interrupts (1), (2), and (3). That is, while the optical disk is being reproduced, the interrupt is continuously generated, whereas the interrupt in the control microcomputer 14 is interrupted when the optical disk is stopped, fast-forwarding or fast-returning, or when the optical disk is being replaced.
[0025]
FIG. 3 shows the relationship between the input of the PCM audio signal to the edge interrupt port of the control microcomputer 14 and the interruption determination of the PCM audio signal. The pulse in the lower part of FIG. 3 means the interrupt of FIG. 2, and when the next interrupt does not occur within t1 ms from the occurrence of the interrupt, the control microcomputer 14 determines that the PCM audio signal has been interrupted.
[0026]
The PCM / dts DSP 13 includes a PCM DSP unit and a dts DSP unit, and the PCM DSP unit outputs the input PCM audio signal as it is or with an added sound field effect. The dts DSP unit detects the presence or absence of a dts header in the input signal, outputs “H” and “L” to the dts detection port in accordance with the presence or absence of the dts header, and decodes the input PCM audio signal with dts. I do. When the dts detection ports of the dts DSP unit of the PCM / dts DSP 13 are “L” and “H”, the control microcomputer 14 outputs the outputs of the PCM DSP unit and the dts DSP unit of the PCM / dts DSP 13 respectively. Select and input to the post processor DSP unit built in the PCM / dts DSP 13. The post-processor DSP performs processing such as BASS MANAGEMENT, DELAY, and mute on the input signal, and sends it to a D / A (Digital / Analog) converter 27. The D / A converter 27 converts an input into an analog signal and outputs the analog signal.
[0027]
FIG. 4 is a block diagram of the PCM / dts receiver 10 for detecting interruption of the input signal from the source using the one-shot circuit 19. FIG. 5 is a timing chart of the input (IN) and output (OUT) of the one-shot circuit 19 of FIG. When a pulse is input from the DIR 11, the one-shot circuit 19 raises the output from "0" to "1". Then, the output is returned from “1” to “0” after a predetermined time t2 ms from the fall of the input. If the one-shot circuit 19 receives a pulse within the predetermined time t2ms, the start of the predetermined time t2ms is updated from the falling time of the new input pulse. In the PCM / dts receiver 10 of FIG. 4, the control microcomputer 14 determines whether the PCM audio signal from the source device is continuous or interrupted based on whether the input from the one-shot circuit 19 is “0” or “1”. I am trying to do it. The provision of the one-shot circuit 19 increases the number of components of the PCM / dts receiver 10 and complicates the structure of the PCM / dts receiver 10.
[0028]
FIG. 6 is a flowchart of a process of switching from a standby state of a PCM audio signal to a predetermined listening mode. For example, when exchanging an optical disk, it is unknown whether the listening mode of the next optical disk is the PCM mode or the dts mode. Head breaks. To avoid this, while the mute is activated, the input of the PCM audio signal is awaited. That is, in S25, the mute is turned on (operating state), and the PCM mode is selected as the initial listening mode. In S26, the input of the PCM audio signal (data) to the control microcomputer 14 is monitored, and as soon as the PCM audio signal is input, the process proceeds to S27. In S27, the sampling frequency of the PCM audio signal (data) to the control microcomputer 14 is detected. Then, the detected sampling frequency is compared with C1 kHz and C2 kHz (S28, S30). If the sampling frequency is C1kHz, the timer is started with the set time D1ms (S29). If the sampling frequency is C2kHz, the timer is started. It starts with the set time D2ms (S31). If the sampling frequency is neither C1 kHz nor C2 kHz, the timer is started with the set time D3ms (S32). The sampling frequency of a CD or LD is C1 kHz, and the sampling frequency of a DVD is C2 kHz. In S37, it is determined whether or not the timer has finished measuring the set time, and in S38, it is determined whether or not the dts header has been detected. If the dts header is detected before the timer finishes measuring the set time, the listening mode is switched to the dts mode, and the mute is turned off (released) (S39). If the dts header is not detected before the timer finishes measuring the set time, the listening mode is switched to the PCM mode, and then the mute is turned off (S40).
[0029]
FIG. 7 is a flowchart of a listening mode control process during playback by setting the listening mode to the PCM mode. First, the timer is started with the set time t1 ms (S44). In S45, it is determined whether or not a dts header has been detected. In S46, it is determined whether or not a PCM audio signal (data) has been input. In S47, it has been determined whether or not the elapsed time measurement value of the timer from activation of S44 has become t1 ms or more. Determine whether or not. If the dts header is detected before the time t1ms elapses after the timer is started in S44, as in the case where the PCM audio signal is switched from the normal PCM audio signal to the PCM audio signal of dts in this way, S55 When the PCM audio signal is continuously input, such as during reproduction, the dts header is not detected after the timer is started in S44, but before the elapse of t1 ms, the next PCM audio signal is input. Is input, the process returns to S44. Further, after the timer is started in S44, such as when the optical disk is fast-forwarded or exchanged, if t1ms elapses without detecting the dts header and inputting the PCM audio signal, that is, it is determined that the PCM audio signal has been interrupted. Then, the process proceeds to S48. In S48, a timer with the set time set to E seconds is newly activated. After the timer is activated in S48, it is determined whether E seconds have elapsed (S49), and it is determined whether the input of the PCM audio signal has been resumed (S50). When the PCM audio signal is input before the elapse of E seconds, such as when the optical disk is fast-forwarded, fast-returned, track skipped, or track jumped, the process returns to S44. If E seconds elapse without inputting the PCM audio signal again, the process proceeds to S51. In S51, the mute is turned on, and the apparatus enters a standby state (start in FIG. 6) of the audio recording medium. In S55, after the listening mode is switched to the dts mode, the mute is turned off, and the optical disc is reproduced in the dts mode (top of FIG. 8).
[0030]
8 and 9 are flowcharts of the listening mode control process during playback with the listening mode set to the dts mode. First, the timer is started with the set time t1 ms (S59). In S60, it is determined whether or not the dts header has been detected. In S61, it is determined whether or not the PCM audio signal (data) has been input. In S62, it has been determined whether or not the elapsed time measurement value of the timer from the start of S59 has reached t1 ms or more. Determine whether or not. In this way, as in the case where the PCM audio signal is continuously input, such as during the reproduction of the optical disc in the dts mode, the dts header is detected before the time t1ms elapses after the timer is started in S59, and When the PCM audio signal is input, the process returns to S59. After the timer is started in S59, such as when the optical disk is fast-forwarded or exchanged, when t1ms elapses without detecting the dts header and without inputting the PCM audio signal, that is, when it is determined that the PCM audio signal has been interrupted. , To S63. In S63, the mute is turned on. In S64, a timer with the set time set to E seconds is newly activated. After the timer is started in S64, it is determined whether or not E seconds have elapsed in S65, whether or not the dts header has been detected in S66, and whether or not the PCM audio signal input has been restarted is determined in S68. Then, if the dts header is detected before E seconds elapse, such as during fast forward, fast reverse, track skip, and track jump of the optical disc, the mute is turned off (S67) and the process returns to S59. That is, the dts mode is maintained. If the dts header is not detected before the elapse of E seconds, but a PCM audio signal is input, the process proceeds to S74. Further, when E seconds elapse without input of the dts header and no input of the PCM audio signal, such as when exchanging an optical disk, the apparatus enters a PCM audio signal waiting state (start in FIG. 6). .
[0031]
In S74, the sampling frequency detected from the PCM audio signal to the control microcomputer 14 is input. Then, the detected sampling frequency is compared with C1 kHz and C2 kHz (S76, S78). If the sampling frequency is C1kHz, such as when the optical disk is a CD or LD, the timer is set to the set time D1ms and started (S77). If the sampling frequency is C2 kHz, as in the case of the DVD, the timer is started with the set time D2 ms (S79). If the sampling frequency is neither C1 kHz nor C2 kHz, the timer is started with the set time D3 ms. (S80). In S84, it is determined whether or not the timer has finished measuring the set time, and in S85, it is determined whether or not the dts header has been detected. When the dts header is detected before the timer finishes measuring the set time, the mute is turned off while the dts mode is maintained (S86), and the process returns to S59. If the dts header is not detected before the timer finishes measuring the set time, the listening mode is switched to the PCM mode, and then the mute is turned off (S90). Thereafter, reproduction is performed in the PCM mode.
[0032]
In the flowchart of FIG. 7, if there is a DATA input during the measurement of the E seconds, the interruption of the data during this period is regarded as not due to the exchange of the optical disk but to the fast forward or the fast reverse, and the current listening mode is maintained. 8 and FIG. 9, in the flowchart of FIG. 8 and FIG. 9, even if there is a DATA input during the measurement of E seconds (the determination of S68 is Yes), the current listening mode is not maintained and the presence or absence of dts is detected. Is checked (S85), and the listening mode is determined. The reason is to cope with the following cases (a) to (c). (A) In a case where one optical disc includes a track of dts and a track of PCM, for example, track 1 is dts and track 2 is PCM, and a transition is made between such tracks . (B) When the optical disk is replaced within E seconds. (C) A case in which a player has a plurality of picks such as two, and an optical disc having a different listening mode is set for each pick, and a playback pick is switched.
[0033]
FIG. 10 is a flowchart showing a process different from that of FIG. 6 and a process of switching from a standby state of a PCM audio signal to a predetermined listening mode. In S95, the mute is activated, and the PCM mode is selected as the initial listening mode. In S96, the input of the PCM audio signal (data) to the control microcomputer 14 is monitored, and if there is data input, the process proceeds to S97. In S97, the timer is started with the set time D1ms. This D1ms corresponds to the sampling frequency of a CD or LD. In S98, it is determined whether D1 ms has elapsed, and in S99, it is determined whether a dts header has been detected. If the dts header is read during D1 ms, as in the case of an optical disc such as a CD or LD, the process proceeds to S112, and if D1ms has elapsed, the process proceeds to S104. In S104, the sampling frequency is input, and in S105, it is determined whether or not the sampling frequency = C2 kHz. C2 kHz corresponds to the DVD sampling frequency. If the sampling frequency is C2 kHz, the timer is started with the set time (D2-D1) ms (S106). If the sampling frequency is not C2 kHz, the timer is started with the set time (D3-D1) ms. (S107). (D2-D1) ms and (D3-D1) ms of the timer setting time are equivalent to setting D2 ms and D3 ms respectively from the start of the timer setting in S97. In S110, it is determined whether or not the timer has finished measuring the set time, and in S111, it is determined whether or not a dts header has been detected. When the dts header is detected before the timer finishes measuring the set time, the listening mode is switched to the dts mode, and the mute is turned off (S112). If the dts header is not detected before the timer finishes measuring the set time, the mute is turned off while the listening mode is maintained in the PCM mode (S115).
[Brief description of the drawings]
FIG. 1 is a block diagram of a part related to processing of a PCM audio signal of a PCM / dts receiver.
FIG. 2 is a diagram showing a relationship between input of a PCM audio signal to an edge interrupt port of the control microcomputer of FIG. 1 and occurrence of an interrupt in the control microcomputer.
FIG. 3 is a diagram illustrating a relationship between input of a PCM audio signal to an edge interrupt port of a control microcomputer and determination of interruption of the PCM audio signal.
FIG. 4 is a block diagram of a PCM / dts receiver that detects a break in an input signal from a source using a one-shot circuit.
FIG. 5 is a timing chart of an input (IN) and an output (OUT) of the one-shot circuit of FIG. 4;
FIG. 6 is a flowchart of a process of switching from a standby state of a PCM audio signal to a predetermined listening mode.
FIG. 7 is a flowchart of a listening mode control process during reproduction by setting the listening mode to the PCM mode.
FIG. 8 is a flowchart of a first part of a listening mode control process during playback with the listening mode set to dts mode.
FIG. 9 is a flowchart of a first part of a listening mode control process during playback with the listening mode set to the dts mode.
FIG. 10 is a flowchart of another process and a process of switching from a standby state of a PCM audio signal to a predetermined listening mode.
[Explanation of symbols]
10 PCM / dts receiver (PCM audio signal playback device)
13 DSP for PCM / dts
14 Control microcomputer

Claims (3)

For a PCM audio signal from an audio recording medium during audio reproduction, an edge in a predetermined direction of a pulse is detected, and a timer on a program is reset each time the detection is performed, and measurement of an elapsed time from the reset by the timer is started. When the measured value of the elapsed time by the timer becomes equal to or longer than a first predetermined time, it is determined that the PCM audio signal from the audio recording medium has been interrupted, and the listening mode is set to the PCM mode or the dts mode, and audio playback is performed. When it is determined from the measurement of the timer that the PCM audio signal from the audio recording medium has been interrupted, it is determined whether or not the PCM audio signal has been input within a second predetermined time from the time of the determination. A PCM audio signal reproducing apparatus characterized in that a mute is activated. The PCM audio signal from the audio recording medium being reproduced is input to the edge interrupt port of the control microcomputer (14), and the control microcomputer (14) interrupts each time an edge of the input pulse to the edge interrupt port in a predetermined direction. 2. The PCM audio signal reproducing apparatus according to claim 1, wherein the timer is reset every time an interrupt occurs. When the PCM audio signal is input in a state where the PCM audio signal is input from the audio recording medium while the mute is activated, the sampling frequency of the PCM audio signal is detected, and a third frequency different for each sampling frequency is detected. A predetermined time is set, and the mute is released in a state where the listening mode is set to the dts mode and the PCM mode depending on the presence or absence of the dts header from the start of the input of the PCM audio signal to the lapse of the third predetermined time, respectively. A PCM audio signal reproducing device characterized by the above-mentioned.

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