JPH03254401A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To allow the device to hardly receive the effect of noise and to prevent the occurrence of distortion by adjusting a recording level of a digital signal resulting from AD-conversion of an analog signal with a digital variable resistor, converting an analog sound signal resulting from DA conversion of the digital signal into an FM audio signal and recording the result. CONSTITUTION:An analog sound signal selected by an input selector 1 is input ted to an A/D converter 4, in which the signal is converted into a digital signal. The digital audio signal is inputted to a digital variable resistor 11 and the level is adjusted by a level adjustment device 12. Then digital signal processing and four phase modulation are applied to the digital sound signal to obtain a PCM audio signal. On the other hand, the digital sound data subject to level adjustment is DA-converted and inputted to a HiFi sound signal processing circuit 9, from which an FM sound signal is obtained. Thus, the sound signal processing circuit 9 immune to noise and with less distortion is realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device (hereinafter referred to as rVTRJ) that records and reproduces video signals, FM audio signals (Hi-Fi audio signals), and PCM audio signals. More specifically, the present invention relates to an audio signal recording circuit.

[Conventional technology]

Figure 2 shows a video signal, Hi-F
FIG. 2 is a block circuit diagram of an audio signal recording circuit of a magnetic recording/reproducing apparatus of a type that simultaneously records an i-audio signal and a PCM audio signal.

In the figure, (1) is the input selector, (2) is the recording level adjuster, (3), +8) is the amplifier, (4) is the AD converter, (5) is the digital signal processing circuit,
(6) is a four-phase phase modulation circuit, (711+01 is a recording amplifier, and (9) is a HiFi audio signal processing circuit.

Next, the operation will be explained.

The analog audio signal selected by the input selector (11) is
A recording level adjuster (a recording level adjuster (
2) to the desired recording level, and then an amplifier (3) for analog-to-digital conversion (rA).
After being amplified to the optimal level necessary for the D conversion (referred to as "D conversion"), it is input to the AD converter (0) and converted to, for example, a 16-bit digital signal. This digital signal is processed by an error correction code, etc. is added and pulse code modulated, approximately 2.6 Mbps
After being converted into a PCM audio signal, it is converted into a QDPSK signal by a four-phase phase modulation circuit (5), and then converted to a QDPSK signal by a recording amplifier circuit (7).
) and then recorded on a magnetic tape via a rotary transformer 5 built into a rotating drum (not shown) and a PCM head.

On the other hand, the level-adjusted analog audio signal is processed by an amplifier (
After being amplified to the optimal level necessary for Hi-Fj audio recording processing by 8), it is input to the Hi-Fi audio recording processing circuit (9), where it is subjected to noise processing. The channels are frequency modulated with a 1.7 MHz carrier wave and added to form a Hi-Fi audio signal, which is amplified by the recording amplifier circuit (10) and then sent to the rotary transformer built in the rotating drum and the Hi-Fi audio signal.
- Recorded on magnetic tape via a Fi audio head.

[Problem to be solved by the invention]

Since the audio input device of the conventional magnetic recording and reproducing device is configured as described above, the recording level adjuster (2) is
Because it needs to be installed in front of the audio processing circuit board, the signal line connecting it to the audio processing circuit board is long, and the S/N ratio is poor because it easily picks up noise. Because of this, there was a problem that distortion increased.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain an audio signal processing circuit that is resistant to noise and has little distortion.

[Means to solve the problem]

The audio signal recording circuit of the magnetic recording and reproducing apparatus according to the present invention performs AD conversion on an input analog audio signal, adjusts the recording level using a digital volume in the state of this digital audio data, and performs digital signal processing on this digital audio signal. and PCM with four-phase phase modulation.
The present invention is characterized in that it is configured to obtain an audio signal, perform DA conversion on level-adjusted digital audio data, and then perform HjFi audio signal processing to obtain an FM audio signal.

[Function] In the audio signal recording circuit according to the present invention, the digital volume can be disposed on the audio signal processing board, and only the level adjuster can be disposed in front of the VTR, so that the length of the analog audio signal line can be shortened. This makes it less susceptible to noise.

Further, since the level adjustment is performed in the state of the digital audio signal, no distortion occurs.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

In the figure, (11) is a digital volume, (12)
The level adjuster adjusts the recorded audio level by calculating the AD-converted digital data. (
13) is a DA converter.

Next, the operation will be explained. The analog audio signal selected by the input selector (1) is input to the AD converter (4) and converted into, for example, a 16-bit digital signal. This digital audio signal is transmitted through a digital volume (
11), the digital data is operated to a level corresponding to the DC voltage adjusted by the level adjuster (2), level-adjusted, and input to the digital signal processing circuit (5). After error correction encoding and the like are performed as in the conventional example, the signal is QDPSK modulated and recorded on a magnetic tape as a PCM audio signal.

On the other hand, the digital signal output from the digital volume (11) is input to the DA converter (13), converted from analog to analog, and then sent to the Hi-Fi audio signal processing circuit (9).
), frequency modulated as in the conventional example, and FM
The audio signal is recorded on magnetic tape.

Note that the DA-converted audio signal is output for monitoring.

According to this embodiment, the digital volume (11) can be mounted on the audio signal processing board, and only the level adjuster (12) needs to be installed on the front of the VTR, so there is no need to route the audio signal line, so there is no noise. The influence of S
/N quality audio signals can be recorded.

In addition, since the recording level is adjusted using digital signal processing, distortion does not occur.
2) is controlled by DC voltage, so the digital volume (
11), it can be placed at any desired position.

In the above embodiment, the level adjuster (12) of the digital volume (11) is adjusted by DC voltage, but this may be done by adjusting the number of pulse signals by a snap switch, or by adjusting the level adjuster (12) of the digital volume (11) as digital data by a microcomputer. Also, in the above embodiment, the digital signal input to the digital volume (11) is a digital signal obtained by AD converting the input analog audio signal by the AD converter (4). The digital data may be input from a digital interface receiver according to the interface format.

In addition, in the embodiment E, the digital volume (11)
Although the level adjustment was performed using the level adjuster (12), it is also possible to use a remote control as an adjustment means.

【Effect of the invention〕

As described above, according to the present invention, the recording level of a digital signal obtained by AD converting an analog audio signal is adjusted with a digital volume, this digital signal is converted into a PCM audio signal, and this digital signal is converted into a PCM audio signal. Convert the analog audio signal into an FM audio signal and perform the above P.
Since the configuration is such that the CM audio signal and the FM audio signal are recorded by each head, there is an effect that a magnetic recording/reproducing device can be obtained that can record audio signals with a good S/N ratio and less distortion.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an audio signal processing circuit according to an embodiment of the present invention, and FIG. 2 is a block circuit diagram of a conventional V ``I' R audio signal processing circuit. (4) - A-D converter , (5)...Digital signal processing circuit, (6)...4-phase phase modulation circuit, (9
)-...HiFi audio signal processing circuit, Fll)-...Digital volume %Tl21-...Level adjuster, [+
31-・DA converter. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A PCM audio signal in which an audio signal is converted into digital data corresponding to a video field and this digital data is phase modulated, and an FM audio signal in which the above audio signal is frequency modulated.
In a magnetic recording and reproducing device configured to record and reproduce an audio signal and a video signal synthesized by frequency modulating a luminance signal and converting a color signal into a low frequency range on a magnetic tape using different magnetic heads, an analog audio signal is input. a digital volume for adjusting the recording level of this digital signal, a means for converting this level-adjusted digital signal into a PCM audio signal, and a means for DA-converting the level-adjusted digital signal. 1. A magnetic recording and reproducing apparatus comprising: a means for converting the analog audio signal into an FM audio signal.