JPS61109390A - Recording device - Google Patents

Abstract

PURPOSE:To make S/N of a sound signal into a practical value by using a noise reduction circuit and an emphasis circuit at the same time and installing these at the optimum position respectively. CONSTITUTION:When a sound signal is compressed by the time base, and recorded in the track in place of a video signal, the sound signal is supplied through the noise reduction circuit 12 to an A/D converting circuit 13 and the converting signal is written in a memory 16. Next, by a clock signal faster than a clock signal at the time of writing, the contents of the memory 16 are read, compressed by the time base, a reading signal is supplied to a D/A converting circuit 20, the converting signal is supplied through an emphasis circuit 24 to an FM modulating circuit 5 and a recording signal is obtained. A digital signal except the sound signal is inserted into the sound signal at the previous portion of the circuit 24, and the video signal is changed over at the latter portion of the circuit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to recording and reproducing audio signals using a still image recording and reproducing device such as an electronic still camera device.

[Conventional technology]

The L7 is equipped with an imaging device such as a CCD, and is designed to record any one field or frame of signals on a magnetic disk.
An electronic still camera device has been proposed.
-197.021 etc.).

In other words, in such a device, one field or one frame of the video signal from the imaging device is gated and extracted at the time of any shutter operation, and this signal is processed so that one field corresponds to one annular track. recorded on a magnetic disk. Note that the signal for one frame is 2
Recorded using book tracks. Therefore, in this device, a video signal of a still image can be formed by repeatedly reproducing one track or two tracks alternately.

It has been proposed to provide such devices with the additional possibility of recording audio signals. To do this, one idea is to use digital signal processing technology to compress the audio signal's time axis, raise the frequency band of the audio signal to the band of the video signal, and record it using the same recording system as the video signal. It will be done.

In this case, for example, by compressing the time axis of an audio signal up to 5 kHz by a factor of 600, it is possible to create a signal with a video band of 3 M) Iz. And in this case, 1
During the field period (1/60 second), 600 times that amount, about 10
It can record audio signals for seconds.

However, in this case, the S/interval of the video signal recording system is about 10 to 20 dB worse than that of the conventional audio signal recording system. Therefore, emphasis circuits with so-called non-linear characteristics are used in video signal recording systems, but when non-linear emphasis is applied to audio signals, sufficient performance cannot be obtained in terms of waveform distortion, modulation noise, return characteristics, etc. Ta.

On the other hand, for audio signals, a noise reduction circuit such as Dolby (trade name) is used, which takes into consideration the characteristics of the audio signal. However, since the S/distance of the recording thread of the video signal is extremely 11 ( (Met.

[Problem that the invention seeks to solve]

It was constructed like a conventional device. However, this device has a problem in that it is difficult to make the S/interval of audio transmission practical.

[Means for solving problem Ijj]

The present invention provides a recording and reproducing apparatus in which a video signal of one field is sequentially recorded concentrically as one trunk, by compressing the audio signal on the time axis and replacing it with the video signal in the above-mentioned 1-rack. When recording the audio signal into the memory (16), the audio signal is supplied to the AD conversion circuit (13) via the noise reduction circuit (12), and this AD converted signal is written into the memory (16). The memory is read out using a clock signal faster than the current clock signal, the time axis is compressed, this read signal is supplied to the DA conversion circuit 128 (20), and this DA converted signal is sent to the emphasis circuit (
24).

At the same time, a digital signal other than the audio signal is inserted into the audio signal at a stage (21) before the emphasis circuit, and switching with the video signal is performed by the emphasis circuit. This is a recording device in which the recording is performed at the latter stage (4) of the circuit.

[Effect]

According to the above-mentioned device, by using both the noise reduction circuit and the emphasis circuit and arranging them at optimal positions, it is possible to make the S/interval of the audio signal practical.

〔Example〕

In Fig. 1, a video signal is supplied to an input terminal (1), converted into a predetermined recording signal by a recording circuit (2), a pre-emphasis circuit (3) with non-linear characteristics, and a changeover switch (4).
) is supplied to the FM modulation circuit 5), and recorded on the disk D by the magnetic head (6) as an FM signal.

In addition, the audio signal is supplied to the input terminal (11) and is supplied (Jt) to the AD conversion circuit (13) through the noise reduction encoder circuit (12). Recording side contact R
Through bit reduction encoder circuit (15)
supplied to This bit-reduced signal is supplied to the memory device (16), and the memory controller (16) is supplied with the bit-reduced signal.
7) is written at a predetermined clock, and read at a clock that is, for example, 600 times faster than that, thereby compressing the time axis. This read signal is supplied to the bit reduction decoder circuit (18), and the decoded signal is passed through the recording side contact R of the recording/reproduction changeover switch (19) to the DA.
It is supplied to a conversion circuit (20). This analog-converted signal is supplied to a mixing circuit (21).

Further, control signals such as divisional recording of the audio signal and recording mode setting from the control circuit (22) are supplied to the memory controller (17) mentioned above, and the identification signal forming circuit (22) is supplied to the memory controller (17) mentioned above.
3), for example, an audio signal identification signal AID, 3
A bit mode identification signal 4MID, a star +-Rs separate signal SID for each divided segment, and an end identification signal BID are formed. These signals are supplied to a mixing circuit (21) and inserted in a time-division manner between each segment of the time-base compressed audio signal as shown in FIG.

The signal from this mixing circuit (21) is supplied to a pre-emphasis circuit (24) with linear characteristics, and the signal from this pre-emphasis circuit (24) is passed through a changeover switch (4) to FM conversion cycle 1(5). The signal is supplied as an FM signal and recorded on the disk D by the magnetic head (6).

Furthermore, during playback, the magnetic head (31)
The reproduced signal is supplied to the FM converter (δ)M circuit (32). When the demodulated signal is a video signal, this signal is sent to a de-emphasis circuit (33) with non-linear characteristics.
It is taken out to the output terminal (35) through the playback surface 11 (34).

Further, when the demodulated signal is an audio signal, this signal is supplied to an 8-digit conversion circuit (42) through a de-emphasis circuit (41) having linear characteristics. This digitally converted signal is supplied to the encoder circuit (15) for bit reduction through the reproducing side contact P of the recording/reproducing changeover switch (14).

In addition, the signal from the de-emphasis circuit (41) is supplied to '3 (43) at the identification signal detection time, each of the identification signals described in 1-1- is detected, and this signal is sent to the jlil control circuit (22) described above.
), the time axis of each segment is expanded, serialized, mode 1 setting, etc. are performed. As a result, a signal whose time axis has been expanded by a factor of 600, for example, is extracted from the bit reduction decoder circuit (18).

The extracted signal is supplied to the DA conversion circuit (44) through the playback side contact P of the recording/playback changeover switch (19). A signal from an oscillator (53) is supplied to this conversion circuit (44). This analog-converted signal passes through the noise reduction decoder circuit (45) to the output terminal (
46).

And in this time 12g, the encoder time 1/A (12) and the decoder time t? of noise reduction. R(45
) is configured, for example, as shown in the third part and the first part. Note 1 is that a part of the bits are shared during encoding and decoding. In step 1, the signal from the input terminal (51) is supplied to the non-inverting input of the playback amplifier (52).

The output of this amplifier (52) is supplied to a gain control amplifier (54) with characteristics as shown in Figure 4 through a filter (53) with D characteristics such as 41klA, and a gain control amplifier (54) with characteristics as shown in Figure 4C. The signal is supplied to a detection circuit (56) through a characteristic filter (55), and the gain of the amplifier (54) is controlled by the detection output. In addition, filter (55)
The characteristic is formed by connecting two filters having the characteristics shown in FIG. 4B. Furthermore, the output of the amplifier (54) is
The signal from the recording side contact R of this switch (58) is supplied to the inverting input of the amplifier (52) (J
The encoded signal at the time of recording is taken out from the output of the amplifier (52) to the output terminal (59), and the decoded signal at the time of reproduction is output from the playback side contact P of the switch (58) to the output terminal (60). ) is taken out.

Furthermore, the emphasis time 19 (24) of the linear characteristic is the fifth
A circuit with characteristics as shown in the figure is used.

Therefore, in this circuit, a noise reduction circuit (12) is provided before time axis compression is performed during recording, and an emphasis circuit II (24) with linear characteristics is provided for the pressure ah, so that the S/N of the audio signal can be sufficiently reduced. We were able to make it practical.

In the above-described circuit, since the linear characteristic is emphasized, the return characteristic, modulation noise, etc. can be improved. Furthermore, various identification signals are inserted into the recording signal as described above, and these must be detected before the time axis is expanded during one generation, so emphasis at the above-mentioned position is optimal. Note that if emphasis is applied before time axis compression during recording, it will become difficult to predict when performing pitch reduction, making 8i compression impossible.

The noise reduction circuit (12) can also be provided after time base compression by changing the time constant, but considering quantization noise during time base compression, noise due to P1 to reduction, etc., the above position is optimal. Become.

Furthermore, since FM recording is performed using the above-mentioned circuit, the distortion characteristics are worse than conventional bias recording, but since high-fidelity sound is not originally required for the medium to which this circuit is applied, the S/N, hit, etc. FM recording with advantageous characteristics is used. Furthermore, since it is FM recording, there is an advantage that the frequency change circuit and demodulation circuit for video signals can be shared.

Furthermore, in the above example, if the 5 ktlz, 10 second signal is digitized to 8 bits, approximately 1 Mbit of memory (16
) is required, but there is no risk of errors in the memory system for time axis compression, so bit reduction can be used effectively. That is, even if 8-bit quantization is compressed to 4 bits by DPCM, floating point coding, etc., almost no deterioration occurs in the circuit described above. Note that the bit reduction during playback results in an extremely high frequency, but for example, the above-mentioned DPC
M is applicable, and in that case, the recording system and reproduction system circuits can be used in common as shown in the figure.

〔Effect of the invention〕

According to the present invention, by using both a noise reduction circuit and an emphasis circuit and arranging them at optimal positions, it is possible to achieve a practical S/N ratio of an audio signal.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an example of the present invention, and FIGS. 2 and 5 are diagrams for explaining the same. (4) is a changeover switch, (5) is an FM modulation circuit, (11
) is the input terminal, (12) is the encoder circuit of the noise reduction η, (13) is the AD conversion circuit, (16) is the memory device, (17) is the memory controller, (20) is the DA conversion circuit, (23) is an identification signal generation circuit, (24)
is an emphasis circuit with linear characteristics.

Claims (1)

[Claims] In a recording device in which one field of video signals is sequentially recorded concentrically as one track, when an audio signal is time-axis compressed and recorded on the track instead of the video signal, the audio signal is supplied to an AD conversion circuit via a noise reduction circuit, this AD-converted signal is written into a memory, the memory is read out using a clock signal faster than the clock signal at the time of writing, and the time axis is compressed. This DA-converted signal is supplied to a modulation circuit via an emphasis circuit to obtain a recording signal, and a digital signal other than the audio signal is converted to the audio signal at a stage before the emphasis circuit. A recording device in which the signal is inserted into the video signal and the switching with the video signal is performed at a stage subsequent to the emphasis circuit.