JPS63102068A - Sound recorder - Google Patents

Abstract

PURPOSE:To start sound recording without loss time or the top of the omitted sound and to make the best use of recording time by resetting an address counter at fixed intervals until a sound signal is inputted. CONSTITUTION:If the sound signal 5a is inputted after the fixed length of time lapses after a sound recording start switch 13 is turned on, a sound signal presence or absence detection circuit 50 transmitas a detection signal 50a to a resetting circuit 51 to stop its osciilation. An address specifying a RAM 8 carries from zero to a larger number corresponding to the lapse of time, and digital sound signals 7a are sequentially written at the carry address first in the RAM 8 in descending order in synchronization with a frequency fs. In that case, just before the digital sound signals 7a are inputted to the RAM 8, a write address in the RAM 8 is specified. Thus the digital sound signal 7a including the intitial one can be written, whereby the sound can be recorded without omitting its top.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a voice recording device, and is intended to be able to start recording without cutting off the beginning of the voice by emitting the voice toward a microphone.

<Prior art> Devices such as electronic still cameras that record image signals of still images on magnetic disks are already known.
II+1, which uses a floppy disk with a thickness of about 40 pm, has been standardized and put into practical use. The floppy disk is rotated at 3600 rpm, and 50 frames of still images are recorded in field recording, and 25 frames of still images are recorded in frame recording on 50 tracks. Truck congestion 6
0I1m, l-rack pitch is 100 μm, and a 40 μm guard band is provided between tracks. The reproduced image is displayed on a monitor such as a television set or printed as a hard copy by a printer.

To record an audio signal on such a 4TB disc, time axis compression is performed, and during playback, time axis expansion is performed. In other words, a 4P disc rotates once in 1/60 seconds, so it can only record 1760 seconds per track, but by compressing the time axis to, for example, 1/640, it is possible to record an audio signal of about 10 seconds. can. Audio signals include signals in various audio areas, such as commentary on recorded still images, background music for viewing reproduced images, and background sounds when photographing with an electronic still camera.

FIG. 3 shows the block configuration of a typical audio signal recording system, and FIG. 4 shows the block configuration of its reproduction system.

In FIG. 3, an audio signal 3 applied from a microphone 1 to an input terminal 2 is passed through a low pass filter (LPF) 4 and a noise reduction circuit (NR) 5, and then input to a time axis compression device 6. Time axis compression device [6 is A/
D conversion N7, RAM (random access memory)
8, D/A converter 9, address counter 10, write clock generator 11, and read clock generator 12
Equipped with.

A recording start switch 13 and a PG detection device 14 are connected to the address counter 10. If the time compression rate is M times, the frequency of the read clock signal 12a is as follows.
The frequency is set to M times the frequency fS of the write clock signal 11a, that is, M-fS. Noise reduction episode @
The audio signal 5a from S is converted into a digital audio signal 7a by an A/D converter 7 at a sampling frequency of f3. After the recording start switch 13 is turned on, this digital audio signal 7a is sent to the RA by advancing the address at a clock frequency of f in the address counter 10.
Stored in M8. 10a is an address signal. R.A.
When the digital audio signal 7a is completely stored in the predetermined area of M80, the address counter 9 advances the address at a clock frequency of Mf in synchronization with the PG signal 14a from the PG detection device 14 and reads out the contents of the RAM 8. The read digital audio signal 8a is converted to M-fll by the D/A converter W9.
It is converted into an analog audio signal 9a at a clock frequency of . The analog audio signal 9a obtained as described above is the audio signal 3 applied to the input terminal 2 whose time axis is compressed to 1/M.

The time-compressed analog audio signal 9a is high-frequency emphasized by a pre-emphasis circuit 15, and then subjected to modulation processing by a frequency modulator 16.
The data are recorded on appropriate tracks of the F4P disk 19 through the process. 20 is a motor that rotates the four-wheel drive disc 19-4.

The time compression rate is determined by the frequency band that can be recorded on the F4P disc 19 and the upper limit frequency required when recording audio signals. In electronic still cameras, etc., an audio signal with a compressed band of 3.2 MHz is transmitted to a futuristic disc rotating at 3,600 rpm.
MHz carrier can be FM modulated and recorded. Therefore, if the upper limit frequency of the audio signal is 1vKHz, M=320
It is given by 0/fV. Further, when the audio signal is recordable, rRT is T=M·1/60=3200/60 fV. Table 1 shows fV=2.5KHz, 5KHz, 1
The specifications for each side of 0 KHz are shown.

For playback, as shown in Figure 4, press the playback switch 3.
2 is turned on, the signal 21a from the magnetic head 21 is amplified! After amplification, the frequency modulation signal is demodulated by a demodulation section 23 and high frequencies are suppressed by a de-emphasis circuit 24, and the signal is input to a time axis expansion device 25. The time axis expansion device 25 includes an A/D converter, a RAM 27, a D/A converter 28, an address counter 29, and a write clock generator.
j30, and a read clock generator 31.

A regeneration switch 32 and a PG detection device 33 are connected to the address counter 29 . Write clock signal 3
The frequency of 0a is M-f8, which is the same as the read clock signal 12a in the time axis compressor 6 of the recording system shown in FIG. Further, the frequency of the read clock signal 31a is the same as that of the write clock signal 11a in the time axis compression device 6. The time-compressed analog audio signal 24a obtained from the de-emphasis circuit 24 is A/D converted.
6, the signal is converted into a digital audio signal 26a at a sampling frequency of M.-. This digital audio signal 26a
is stored in the RAM 27 by the address counter 29 advancing the address at a clock frequency of M·(6 or more) in synchronization with the PG signal 33a from the PG detection device 33. 29a is an address signal. When the digital audio signal 26m has been stored in the predetermined area, the address counter 29 advances the address at a clock frequency of f and reads out the contents of the RAM 27.The read digital audio signal 27a is converted to fS by the D/A converter 28. It is converted into an analog audio signal 28a at the clock frequency.The analog audio signal 28a obtained by the above is a signal in the audio band whose time axis has been returned to the original.This audio signal 28a
are a low-pass filter 34 and a noise reduction circuit 35.
The signal is then applied to a speaker 37 through an amplifier 36 and output as sound.

<Problems to be Solved by the Invention> In the conventional audio recording described above, recording can be performed without waste by turning on the recording start switch 13 shown in FIG. 3 and then immediately speaking into the microphone 1. In other words, in the 10-second mode, you can record the entire recording time of about 10 seconds. However, in reality, the start switch 1
There is often a time lag between turning on 3 and starting speaking. In such a case, the first part of the recording will be blank and the actual recording time will be shortened.

The recording blank period is thought to be about 1 to 2 seconds, although it varies depending on individual differences and the content of what is being said. Considering that the total recording time is about 10 seconds (in 10 seconds mode), the 1 to 2 seconds of lost time becomes a big problem.

In view of the above prior art, the present invention provides an audio recording device that starts recording on the condition that an audio signal is input from a microphone phone.

<Means for Solving the Problems> The configuration of the present invention for solving the above problems is such that, in an audio recording device that magnetically records an analog audio signal compressed using a time axis compression device, when starting recording, an address counter that starts the operation of specifying a memory write address when the recording start switch is turned on, and sequentially increments the specified address in synchronization with a first clock signal during writing; An audio signal presence/absence detection circuit that detects the presence or absence of an audio signal, and an address counter that is reset at regular time intervals during the period from the start of address designation operation by the address counter to the time when the audio signal presence/absence detection circuit detects the input audio signal. It is characterized by being equipped with a reset circuit.

<Function> Even after the recording start switch is turned on, the address counter is reset at fixed time intervals by the reset circuit until an input audio signal is input, so that recording blank periods can be almost eliminated.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that parts that are the same as those in the prior art are given the same numbers.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, numerals 1 to 20 are the same as those in the prior art shown in FIG. In other words, the audio signal 3 from the microphone 1 has unnecessary components removed and becomes the audio signal 5a. Audio signal 5a
is compressed by the time axis compressor 6 to become an analog audio signal 9a. The time-base compressed audio signal 9a is then recorded on the floppy disk 19.

Further, in this embodiment, an audio signal presence/absence detection circuit 50 and a reset circuit 51 are provided. Audio signal presence/absence detection circuit 5
0 is a circuit that determines whether or not the audio signal 5a is input to the A/D converter 7, and outputs a detection signal 50a when the input of the audio signal 5a is detected. On the other hand, reset circuit 5
1 is a circuit that oscillates a reset pulse 51a at fixed time intervals (every second in this example), and the recording start switch 1
3 starts oscillation when turned on, and stops oscillation when it receives the detection signal 50a.

The address counter 10 starts outputting the address signal 10a when the recording start switch 13 is turned on, but is reset each time the reset pulse 51a is input.

The operation of this embodiment will now be described with reference to FIG. 1, which is a block diagram, and FIG. 2, which shows operation timing. Note that the recording mode is 10 seconds mode (recording time approximately 10 seconds).

An example will be explained in which speaking starts 3.5 seconds after the recording start switch 13 is turned on. When the RAM 8 is put into a writing state and the recording start switch 13 is turned on, the address counter 10 starts outputting the address signal 10g and the reset circuit 51 starts oscillating. The designated address on the RAMB by the address signal 10a is sequentially incremented in synchronization with the frequency amount 9 of the clock signal 11a.

At this time, since the audio signal 5a+ is not input, the RAM8
No audio signal is written to the address area specified above and it becomes blank.

When one second has elapsed since the recording start switch 13 was turned on, a reset pulse 51a is output from the reset circuit 51, and the address counter 10 is reset by this reset pulse 51a. When such a reset is performed, the write designated address on RAM 10 by the address counter 10 returns to zero, and the designated address is sequentially incremented again from the zero address.

The address counter 10 is similarly reset by the reset pulse 51a when two seconds or even three seconds have passed since the recording start switch 13 was turned on.

=12- The audio signal 5a is input 3.5 seconds after the recording start switch 13 is turned on. Then, the detection signal 50a from the audio signal presence/absence detection circuit 50 is reset #
551, and the oscillation of the reset circuit 51 is stopped. On the other hand, the RAM80 specified address is from zero address to 0.5
The address is moved up to the address for which seconds have elapsed, and the digital audio signal 7 is sequentially moved up from this moved up specified address area.
A is written into the RAM 8 in synchronization with the frequency f. In this case, since the write address of the RAM 8 is specified immediately before the digital audio signal 7a is input to the RAM 8, it is possible to write from the first signal of the digital audio signal 7a, and it is possible to record without cutting off the beginning of the audio. .

In the end, after turning on the recording start switch 13, 3.
Even if you start speaking after 5 seconds, you can record it with the least blank period in the recording.

Note that a slight loss time T (0.5 seconds in this example) occurs between the time the address counter 10 is reset for the third time and the time the digital audio signal 7a is written.
The maximum loss time TI is only the oscillation interval (1 second) of the reset pulse 51a. Furthermore, by further shortening the oscillation interval of the reset pulse 51a, the loss time T can be extremely shortened.

After the digital audio signal 7a is written into the RAM 8 as described above, the audio signal is recorded onto the floppy disk 19 in the same manner as in the prior art.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the address counter is reset at fixed time intervals until an audio signal is input, so that recording can be performed without loss time or cutting off the beginning of the audio. You can start recording and make full use of your recording time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the operation of the embodiment, FIG. 3 is a block diagram showing a conventional recording device, and FIG. 4 is a conventional recording device. 1 is a block configuration diagram showing a playback device of FIG. In the drawing, 1 is a microphone, 6 is a time axis compression device, 7 is an A/D conversion station, and 8 is a RAM. 9 is a D/A converter, 10 is an address counter, 11.12 is a clock signal generator, 13 is a recording start switch, 18 is a magnetic head, 19 is a floppy disk, 50 is an audio signal presence detection circuit, 50a is a detection signal , 51 is a reset circuit, and 51a is a reset pulse.

Claims (1)

[Claims] A digital audio signal obtained by A/D converting an input audio signal, which is an analog signal, is written into the memory in synchronization with a first clock signal, and the digital audio signal written into the memory is transferred to the first clock signal.
In an audio recording device that records an analog audio signal obtained by D/A converting the read digital audio signal on a rotating magnetic recording medium, A recording start switch that is turned on when starting recording, and an operation for specifying a memory write address is started by turning on the recording start switch, and at the time of writing, the specified address is sequentially incremented in synchronization with a first clock signal. an audio signal presence/absence detection circuit for detecting the presence or absence of the input audio signal; An audio recording device comprising: a reset circuit that resets at regular time intervals.