JPS63250700A - Voice recorder/reproducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention converts a recording signal obtained from a microphone into a digital signal and stores it in a semiconductor memory, and also converts the signal stored in the semiconductor memory during playback operation. The present invention relates to a voice recording/playback device that reads out a voice, converts it into an analog signal, and then leaves it on a speaker.

(B) Conventional Technology Cassette tape recorders, which use magnetic tape called cassette tape, have become popular as devices for recording and playing back audio. Devices such as cassette tape recorders that use magnetic tape as a means of recording audio signals have the advantage of being able to perform long recording operations, but they are difficult to miniaturize. Since it requires a mechanism to drive the magnetic tape, there is a problem in that the failure rate is high. As an improved device in this respect, the audio signal is converted into a digital signal and stored in a semiconductor memory, and during playback operation, the signal stored in the semiconductor memory is read out, converted into an analog signal, and then left in the speaker. A technology has been developed that is based on
There is one disclosed in Japanese Patent No. 2800.

(c) Problems to be solved by the invention The technology disclosed in the above-mentioned publication uses a semiconductor memory as a means to record audio signals, which eliminates the need for a drive mechanism like a tape recorder, and makes the device compact. It has the advantage of being able to reduce the cost and failure rate. However, with such technology, since the time required for recording by specifying an address is long, a large portion of the memory is stored in non-recorded areas, that is, non-signal areas, making it impossible to efficiently use the capacity of semiconductor memory. There is a problem. The present invention aims to provide an audio recording/playback device that is improved in this respect.

(d) Means for solving the problems The present invention provides an ADPCM analysis and synthesis circuit that performs voice analysis and voice synthesis using the ADPCM method during recording and playback operations;
It is comprised of an address control circuit that controls the write operation of digital signals output from the ADPCM analysis and synthesis circuit into the semiconductor memory circuit and the read operation of the signals stored in the semiconductor memory circuit.

(*) Effect The present invention effectively uses the capacity of the semiconductor memory circuit by performing the audio analysis and synthesis processing by the ADPCM analysis and synthesis circuit and the storage operation in the semiconductor memory circuit in short intervals and continuously. It was designed to do so.

(F) Embodiment The circuit shown in FIG. 1 is an embodiment of the present invention, and FIG. 2 is a diagram for explaining the present invention in detail.

In the illustrated circuit, (1) is a microphone that converts an acoustic signal into an electrical signal, and (2) is the microphone (
1) is input with a recording signal converted into an electrical signal and amplifies the signal; (3) is unnecessary as the recording signal amplified by the recording amplifier circuit (2) is input. This is a low-pass filter that blocks high-frequency signals. (4) is the low pass filter (3)
A converts the analog signal passed through into a digital signal
-D converter (5) is an ADPC that performs digital processing using a method called ADPCM, that is, adaptive differential pulse code modulation.
M analysis and synthesis circuit, (6> is a D-A converter that converts the digital signal processed by the ADPCM analysis and synthesis circuit (5) into an analog signal, and (7) is the D-A converter (
6) is a low-pass filter into which the reproduced signal converted to an analog signal is input and which cuts off unnecessary high-frequency signals; The reproducing amplifier circuit (9) is a speaker to which the signal amplified by the reproducing amplifier circuit (7) is applied and leaves the signal alone. (10) is a control unit that controls the analysis operation and synthesis operation of the ADPCM analysis and synthesis circuit (5);
1) is an external circuit, the control section (10) and ADPCM
This is a data I10 buffer circuit that controls input/output operations of signals to/from the analysis/synthesis circuit (5). In such a circuit, an A-D converter (4), an ADPCM analysis and synthesis circuit (5)
), D-A converter (6), control section (10) and data I
The 10 buffer circuit (11) constitutes an audio processing circuit (11), but such a circuit can be, for example, one manufactured by Oki Electric Industry Co., Ltd. (7) LSI' MSM6258, and its details are omitted. do. (13) is a data I10 buffer circuit (1) constituting the audio processing circuit (12).
1) a RAM which is a semiconductor memory that stores digital signals output from the RAM; (14) an address control circuit that controls writing and reading operations of signals to the RAM (13); and (15) the audio processing circuit. (12), R.A.
This is a control circuit that controls the operations of M (13) and the address control circuit (14). (16) is a recording operation switch that can be pressed and closed when the audio signal is stored in the RAM (13), and (17) is a recording operation switch that can be pressed and closed when the signal stored in the RAM (13) is read out and played back. (18) is a fast-forward operation switch that is pressed and closed during fast-forward operation; (19) is a rewind operation switch that is pressed and closed during rewind operation; (20) is a stop operation switch. This is a stop operation switch that is closed when pressed.

The present invention is constructed as described above, and its operation will be explained next. Assuming that the sampling frequency in the audio processing circuit (μ) is 8 KHz and the number of quantization bits is 4, the bit rate is 32 bits/second, and RAM (13
) has a capacity of 1 Mbit, it can be stored for about 32 seconds. In the present invention, the analysis and synthesis processing by the ADPCM analysis and synthesis circuit (5) and the R
Write operations to AM (13) are performed every 250 milliseconds. In other words, the A
The analysis and synthesis operation by the DPCM analysis and synthesis circuit (5) is started, and after 250 milliseconds, the analysis and synthesis operation is stopped by a stop signal output from the control section (10). When a signal is written to the RAM (13), that is, during a recording operation, the signal analyzed and processed by the ADPCM analysis and synthesis circuit (5) during the 250 milliseconds is transferred to the RAM (13) through the data 110 buffer circuit (11). At the same time as being outputted, the address is written into the RAM (13) by the control operation of the address control circuit (14) while specifying the address. In addition, when reading a signal from the RAM (13), that is, during a playback operation, the signal synthesized by the ADPCM analysis and synthesis circuit (5) during the 250 milliseconds is input to the D-A converter (6) and analog converted into a signal. In this way, the audio processing circuit (1) and the address control circuit (1)
The control operation of R A M (13) according to 4) is performed, and each operation in this embodiment will be explained next.

When a recording operation is performed, power is supplied to the recording amplifier circuit (2), the recording operation switch (16) is pressed and closed, and the control circuit (15) performs a control operation for recording. The recording signal that has been converted into an electrical signal by the microphone (1) is input to the recording amplifier circuit (2), amplified, and then input to the audio processing circuit (婬〉) through the low-pass filter (3).The audio processing The recording signal inputted to the circuit is converted into a digital signal by the A-D converter (4) and analyzed by the ADPCM analysis/synthesis circuit (5) for 250 milliseconds as described above.

Further, the signal analyzed and processed by the ADPCM analysis and synthesis circuit (5) is outputted to the RAM (13) through the data I10 buffer circuit (11) and sent to the address control circuit (14).
is written into the RAM (13) by the control operation.

Then, while the recording operation is being performed, the above-mentioned ADPC
The analysis operation by the M analysis synthesis circuit (5) and the RAM (
The write operation to RAM (13) will be repeated until a stop operation is performed or until the capacity of RAM (13) is exhausted. Figure 2 (a) explains such a recording operation, in which the analysis operation by the ADPCM analysis and synthesis circuit (5) starts at point (A) and stops at point (B); The period between (A) and (B) is 250 milliseconds. Although the recording operation is performed in this manner, the reproduction operation will be explained next. When the playback operation is performed, power is supplied to the playback amplifier circuit (8) and the playback operation switch (
17) is pressed closed, and the control circuit (15) performs a control operation for regeneration. The signals stored in the RAM (13) are read out by the control operation of the address control circuit (14) and sent to the ADPCM analysis and synthesis circuit (5) through the data 110 buffer circuit (11).
is input. The digital signals input to the ADPCM analysis and synthesis circuit (5) are subjected to synthesis processing for 250 milliseconds each by the ADPCM analysis and synthesis circuit (5).
- Applied to the A converter (6>) and converted into an analog signal.The signal converted into an analog signal by the D-A converter (6) is passed through the low-pass filter (7) and sent to the reproduction amplifier circuit (8). After being input and amplified by the speaker (9), the readout operation from the RAM (13) and the synthesis operation by the ADPCM analysis and synthesis circuit (5) are stopped. The reproducing operation is repeated until the reproducing operation is completed or the signal written in the RAM (13) is exhausted.
The synthesis operation by the ADPCM analysis and synthesis circuit (5>) starts at point (A) and stops at point (B).
The period between A) and (B) is 250 milliseconds.

The recording and reproducing operations are performed as described above, but the fast-forwarding and rewinding operations will now be explained. When the user performs a fast forward operation, the fast forward operation switch (18) is closed and power is completely supplied to the reproduction amplifier circuit (8).

When the fast forward operation switch (18) is fully closed, the RA
The readout operation of the signal from M (13) and the synthesis operation by the ADPCM analysis and synthesis circuit (5) are performed as shown in FIG. 2(c). As is clear from the figure, the beginning part (A) to (B) between (A) and (B) was analyzed during the recording operation.
The reading and compositing processing is performed only during the period C), and the signal is left as it is from the speaker (9). Between (A) and (C),
) to (B) is set to 174, or 62.5 milliseconds, it will be played back at four times the speed compared to the playback operation described above, but unlike a tape recorder, it can be left unattended from the speaker (9). Since the frequency of the signal never increases, the reproduced signal can be heard, albeit in fragments. Although fast-forwarding is performed in this way,
Next, the rewinding operation will be explained. When the rewinding operation is performed, the rewinding operation switch (19) is closed and power is supplied to the reproducing amplifier circuit (8). When the rewind operation switch (19) is fully opened, the readout operation of the signal from the RAM (13) and the ADPCM analysis and synthesis circuit (5) are performed.
The combining operation is performed as shown in FIG. 2(d). As is clear from the figure, the analysis process was completed during the recording operation (
Only the beginning parts (A) to (C) between A) and (B) are read out and synthesized and left alone from the speaker (9), but the readout operation is performed in the direction of the recording operation. It goes in the opposite direction. Between (A) and (C), (A)
If you set the interval between (B) to 174, or 62.5 milliseconds, it will rewind and play at four times the speed, but unlike a tape recorder, the frequency of the signal left from the speaker (9) will not increase. Since the words are left alone, the reproduced signal can be heard, albeit in fragments.

Note that the recording and playback time can be increased by increasing the capacity of RAM (13) or by setting the sampling frequency low. Furthermore, if the RAM (13) is built into a container called an IC card and the IC card (RAM (13)) can be converted, it can be used as a recording means in place of a tape recorder even if the RAM (13) has a small capacity. Furthermore, although the analysis and synthesis time during recording and playback operations was set to 250 milliseconds, and the synthesis time during fast forward and rewind operations was set to 62.5 milliseconds, the times are not limited.

(G) Effects of the Invention The audio recording and reproducing device of the present invention performs the audio analysis and synthesis processing operation by the ADPCM analysis and synthesis circuit and the storage operation in the semiconductor memory circuit in short intervals and continuously, so that the recording operation is performed. If the recording operation is canceled by the time stop operation, the storage operation of the memory circuit can be stopped immediately, which has the extremely great advantage that the capacity of the radiating conductor memory circuit can be used effectively.

[Brief explanation of drawings]

The circuit shown in FIG. 1 is an embodiment of the present invention, and FIG. 2 is a diagram for explaining the present invention in detail. Explanation of main figure numbers 1)... Microphone, (2)... Recording amplifier circuit, (5)... ADPCM analysis and synthesis circuit, (8
)...Reproduction amplifier circuit, (9)...Speaker,
(Attack)...Audio processing circuit, (13)...RAM
, (14)...address control circuit, (15)...
・Control circuit.

Claims (1)

[Claims] (1) Convert the recorded signal obtained from the microphone into a digital signal and store it in a semiconductor memory circuit, and during playback operation, read out the signal stored in the semiconductor memory circuit, convert it into an analog signal, and leave it on the speaker. In the audio recording/playback device configured to
an address control circuit that controls writing of digital signals output from the analysis and synthesis circuit into the semiconductor memory circuit and readout of signals stored in the semiconductor memory circuit; A voice recording/playback device characterized in that a synthesis processing operation and a storage operation in a semiconductor memory circuit are performed in short intervals and continuously.