JP3159856B2 - Digital audio equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio device such as a mini disk.

[0002]

2. Description of the Related Art Conventionally, in a digital audio device such as a mini disk device capable of recording and reproducing an audio signal by switching between a stereo mode and a monaural mode, a signal format as shown in FIG. 5 is known.

FIG. 1A shows a format of a cluster of a recording medium. One cluster is composed of 36 sectors, 4 sectors of 36 sectors are used for a ring sector for completing error correction and for sub data, and 3
Two sectors are used to record audio data. FIG. 2B shows the format of an audio sector in which audio data is recorded. The audio sector has an area of 2356 bytes, and 2332 bytes are an audio block for recording audio data. The audio blocks of the even sector and the odd sector of the audio sector 424 shown in FIG.
Eleven sound groups having a byte area are formed, and each sound group records 2048 bytes of audio data after being compressed to about 1/5.

[0004] This 2048 bytes (16384 bits)
In the stereo mode, the audio data of
As shown in FIG. 6, each of the left and right audio data has 1024 bytes (8192 bits). Also,
In the case of the monaural mode, as shown in FIG.
It is composed of 24 bytes (8192 bits) of first audio data and second audio data.

That is, the sampling frequency is set to 44.1k.
When HZ is quantized by 16 bits, one sound group corresponds to about 11.6 ms in the stereo mode and about 23.2 ms in the monaural mode. Therefore, the recording and reproducing time is twice as long in the monaural mode as in the stereo mode. Can be.

In such a digital audio device, when an audio signal is recorded in a monaural mode,
It is known that left and right audio signals are mixed in the state of an analog signal, then converted into a digital signal and recorded. FIG. 3 shows a configuration example of a conventional digital audio device.

In FIG. 3, reference numeral 1L denotes a left channel signal input terminal, and an audio input signal SL supplied to the signal input terminal 1L is supplied to a matching amplifier 4L via an input amplifier 2L and a volume 3L. The matching amplifier 4L is for adjusting the signal level to the input sensitivity of the next stage circuit and for matching the impedance. The audio signal S1L output from the matching amplifier 4L is supplied to the A / D
It is supplied to the converter 5L. The audio signal S1L is converted into digital audio data SDL by the A / D converter 5L.
Is converted to The digital audio data SDL is supplied to a terminal 7a of the signal processing unit 7.

Reference numeral 1R denotes a right channel signal input terminal. An audio input signal SR supplied to the signal input terminal 1R is supplied to a matching amplifier 4R via an input amplifier 2R and a volume 3R. This matching amplifier 4R is also for matching the signal level to the input sensitivity of the next stage circuit and for matching the impedance similarly to the above-described matching amplifier 4L. The audio signal S1R output from the matching amplifier 4R is supplied to a movable terminal of the changeover switch 11. Audio signal S1R
Is supplied to the A / D converter 5R when the switch 11 is switched to the terminal a, and is supplied to the adder 10 when the switch 11 is switched to the terminal b. A / D converter 5
The audio signal S1R supplied to R is converted into digital audio data SDR and supplied to the terminal 7b of the signal processing unit 7.

Reference numeral 9 denotes a key operation unit.
Is for switching between a stereo mode and a monaural mode. The signal processing unit 7 and the changeover switch 11 are controlled by the control unit 8 in association with the operation of the key operation unit 9.

Here, when the stereo mode is set by operating the key operation section 9, the signal processing section 7 is set to the stereo mode by the control section 8 and the changeover switch 11 is set.
Is switched to the a-side terminal.

The audio input signal SR supplied to the signal input terminal 1R is amplified by an input amplifier 2R, adjusted in signal level by a volume 3R, and supplied to a matching amplifier 4R. The audio signal S1R output from the matching amplifier 4R is supplied to the changeover switch 11 and supplied to the A / D converter 5R from the terminal a. The audio signal S1R is converted into digital audio data SDR by the A / D converter 5R and supplied to the terminal 7b of the signal processing unit 7.

The audio input signal SL supplied to the signal input terminal 1L is, as in the case of the right channel,
It is supplied to the matching amplifier 4L via the input amplifier 2L and the volume 3L. The audio signal S1L output from the matching amplifier 4L is supplied to the adder 10. Since the changeover switch 11 is switched to the a-side terminal, no signal is supplied to the b-side terminal, and the audio signal S1L is supplied to the A / D converter 5L without the signal being added by the adder 10. Is done. This A / D converter 5L
Thus, the audio signal S1L is converted into digital audio data SDL and supplied to the terminal 7a of the signal processing unit 7.

FIG. 4 shows the operation of the signal processing section 7. FIG. 7A shows the audio signal S1L, and FIG. 7B shows the audio signal S1R. These audio signals S1L, S1R
Are converted into digital audio data SDL and SDR by A / D converters 5L and 5R. For example, the audio signal S
Digital audio data SDL and SDR obtained by sampling 1L and S1R at time t0 are L0 and R0, respectively.
Similarly, digital audio data S1L and S1R obtained by sampling at time tn are Ln and Rn.
It is said.

The digital audio data SDL and digital audio data SDR supplied to the terminals 7a and 7b of the signal processing section 7 are alternately arranged by the signal processing section 7 as shown in FIG. L1 → R1 → ・ ・ ・ → Ln →
The signals are arranged in the order of Rn and output as one signal sequence from the terminal 7c of the signal processing unit 7. As shown in FIG. 3, the output stereo digital signal DST is supplied to a next-stage circuit (not shown), where signal compression, modulation, and the like are performed and recording processing is performed.

Next, when the monaural mode is set by operating the key operation unit 9, the signal processing unit 7 is set to the monaural mode by the control unit 8, and the switch 11 is switched to the b-side terminal.

The audio signal S1R processed in the same manner as in the stereo mode and supplied to the changeover switch 11 is
Since the changeover switch 11 has been switched to the b-side terminal, it is supplied to the adder 10. Since the changeover switch 11 has been switched to the b-side terminal, the changeover switch 11
No signal is supplied to the A / D converter 5R and the terminal 7b of the signal processing unit 7 which are connected to the terminal a on the side.

The audio signal S1L processed in the same manner as in the stereo mode and supplied to the adder 10 is
The adder 10 adds the audio signal S1R to the audio signal S1R and supplies the resulting signal to the A / D converter 5L. With this A / D converter 5L,
The audio signal SADD obtained by adding the audio signal S1L and the audio signal S1R is a digital audio data SDM.
And supplied to the terminal 7a of the signal processing unit 7.

FIG. 4C shows the audio signal SADD. This audio signal SADD is converted into digital audio data S by the A / D converter 5L in the same manner as in the stereo mode.
Converted to DM. For example, the digital audio data SDM obtained by sampling the audio signal SADD at the time point tn is (L + R) n.

Since the signal processing section 7 is set to the monaural mode, the digital audio data SDM supplied to the terminal 7a is sequentially output from the signal processing section 7. In other words, as shown in FIG.
One (L + R) 1 →... → (L + R) n is output in sequence from the terminal 7c of the signal processing unit 7. FIG. E shows the structure of the signal sequence and compares the data amount with FIG. D, and does not show that the time has been shortened. The output monaural digital signal DM1 is supplied to the next-stage circuit, where signal compression, modulation, and the like are performed and recording processing is performed, as in the case of the stereo mode.

As described above, in the monaural mode, the data amount is half that in the stereo mode, so that the recording time can be twice as long as that in the stereo mode.

[0021]

In the conventional digital audio apparatus described above, when recording in the monaural mode, the audio signal S1L and the audio signal S1R are added, so that the phase difference between the audio signals S1L and S1R is used. There is a problem that the level changes or noise increases. Further, in the monaural mode, a changeover switch 11 for adding the audio signal S1R to the audio signal S1L is required. Further, the changeover switch 11 is provided in the stereo mode and the monaural mode so that the audio signal is not affected by noise. The switch is provided separately from the operation switch of the key operation unit 9 for selecting a mode, which causes a cost increase.

Therefore, the present invention provides a digital audio apparatus which can be constructed at low cost without changing the level of the audio signal or deteriorating the S / N, and which can record a monaural signal including information on the left and right audio signals. It is.

[0023]

SUMMARY OF THE INVENTION The present invention provides an input amplifying means for amplifying left and right analog audio signals and varying the signal level, and sampling left and right analog audio signals input to the input amplifying means to obtain a right and left analog audio signal. A / D conversion means for converting the digital signals output from the A / D conversion means into a single signal sequence according to a stereo mode or a monaural mode; Or control means for switching control to a monaural mode, and when the stereo mode is selected by the control means, the signal processing means alternately arranges the left and right digital signals into one signal sequence, and the control means selects the monaural mode. In this case, the signal processing means extracts the left and right digital signals alternately and
One signal sequence.

[0024]

In the present invention, when the monaural mode is selected, the left and right digital signals are alternately extracted by the signal processing means into one signal sequence, so that it is not necessary to add the left and right audio signals.

Therefore, there is no problem that the signal level changes due to the phase difference of the audio signal or that the S / N ratio deteriorates. In addition, a changeover switch for switching the signals so that the audio signals can be added is not required, and the configuration can be made at a low cost. Further, it is possible to record as a monaural signal independently including the information of the left and right audio signals.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital audio apparatus according to the present invention will be described below with reference to FIG.
In FIG. 1, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, an audio input signal SL input to a signal input terminal 1L is supplied to an A / D converter 5L via an input amplifier 2L, a volume 3L, and a matching amplifier 4L, and is converted into digital audio data SDL. Then, it is supplied to the terminal 6 a of the signal processing unit 6. Similarly, the audio input signal SR input to the signal input terminal 1R is supplied to an A / D converter 5R via an input amplifier 2R, a volume 3R, and a matching amplifier 4R, and is converted into digital audio data SDR to perform signal processing. It is supplied to the terminal 6b of the unit 6.

Here, when the stereo mode is set by operating the key operation unit 9, the signal processing unit 6 is set to the stereo mode by the control unit 8.

FIG. 2 shows the operation of the signal processing section 6.
In the figure, A indicates the audio signal S1L, and B indicates the audio signal S1R. As in the conventional example, the audio signals S1L and S1R are converted into digital audio data SDL and SDR by A / D converters 5L and 5R. For example, the digital audio data SDL and SDR obtained by sampling at the time point t0 are L0 and R0, and the time points t2n
The digital audio data SDL and SDR obtained by sampling are L2n and R2n.

The digital audio data SDL and SDR supplied to the terminals 6a and 6b of the signal processing section 6 are alternately arranged by the signal processing section 6 as shown in FIG.
→ L1 → R1 →... → Ln → Rn, and output from the terminal 6c of the signal processing unit 6 as one signal sequence. As shown in FIG. 1, the output stereo digital signal DST is supplied to a next-stage circuit (not shown), where signal compression, modulation, and the like are performed and recording processing is performed.

Next, when the monaural mode is set by operating the key operation section 9, the signal processing section 6 is set to the monaural mode by the control section 8. In this case, the signal processing unit 6
It is set so that digital audio data SDL and digital audio data SDR obtained at each sampling point are alternately selected. Therefore, as shown in FIG.
L0 → R1 →... →
The terminal 6 of the signal processing unit 6 is configured in the order of L2n-2 → R2n-1.
c to be output as one signal sequence. FIG.
Shows the structure of the signal sequence and compares the data amount with FIG. C, and does not indicate that the time has been reduced. This output monaural digital signal DM2
Is supplied to the next-stage circuit and subjected to signal compression, modulation, and the like, as in the case of the stereo mode, and is subjected to recording processing.

As described above, in the present embodiment, when the monaural mode is set, since the audio input signals SL and SR are processed independently without being added, the phases of the respective signals are different. The signal level does not change, and the noise does not increase. Furthermore, a changeover switch and an adder for adding the audio signal S1R to the audio signal S1L are not required, and the configuration can be made at low cost. Further, at the time of reproduction, a monaural signal including information of the left and right audio signals can be obtained.

In this example, the digital audio data SDL and SDR are alternately extracted in the order of L0 → R1 →... → L2n−2 → R2n−1 to form one signal sequence. For example, L0 → L1 Some digital audio data SDL and SDR may be collectively and alternately extracted in the order of → R2 → R3 → L4 →, or data may be thinned out in the order of L0 → R2 → L4 → to form one signal sequence.

[0034]

According to the present invention, when the monaural mode is selected, the left and right digital signals are alternately extracted by the signal processing means to form one signal sequence.
There is no need to add left and right audio signals. for that reason,
There is no problem that the signal level changes due to the phase difference of the audio signal or that the S / N deteriorates. In addition, a changeover switch for switching the signals so that the audio signals can be added is not required, and the configuration can be made at a low cost. Furthermore, it can be recorded as a monaural signal including the information of the left and right audio signals independently.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a digital audio device according to the present invention.

FIG. 2 is a diagram illustrating an operation of a signal processing unit according to the embodiment.

FIG. 3 is a diagram showing a configuration of a conventional digital audio device.

FIG. 4 is a diagram illustrating an operation of a signal processing unit of a conventional digital audio device.

FIG. 5 is a diagram illustrating an example of a signal format.

[Explanation of symbols]

 1L, 1R signal input terminal 2L, 2R input amplifier 3L, 3R volume 4L, 4R matching amplifier 5L, 5R A / D converter 6, 7 signal processing unit 8 control unit 9 key operation unit 10 adder 11 switch

Claims (1)

(57) [Claims] An input amplifying means for amplifying left and right analog audio signals and varying the signal level, sampling left and right analog audio signals input to the input amplifying means, and converting them into left and right digital audio data. A / D conversion means, signal processing means for arranging left and right digital audio data output from the A / D conversion means into one signal sequence according to a stereo mode or a monaural mode, Control means capable of switching control to a monaural mode, wherein when the stereo mode is selected by the control means,
The signal processing means alternately arranges the left and right digital audio data into one signal sequence. When the control means selects the monaural mode, the signal processing means alternately extracts the left and right digital audio data. A digital audio device characterized in that the signal sequence is one signal sequence.