JPH0799613B2 - Tape recorder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape recorder, and more particularly to a tape recorder with improved output monitor sound during high-speed dubbing.

(Prior Art) Conventionally, so-called high-speed dubbing is performed, in which two tape recorders are used and an audio signal reproduced by running a tape of one tape recorder at a high speed is recorded on the other tape that is also running at a high speed. At that time, the recorded sound was monitored by converting the high-speed playback signal into a sound as it is.

As described above, in the conventional monitor at the time of high-speed dubbing, the high-speed reproduction signal is converted into the sound and used as the monitor sound. However, since the spectrum of the high-speed dapping reproduced sound moves to the high frequency side as compared with the original sound, the monitor reproduced sound becomes a signal significantly different from the original sound. Therefore, it is difficult to grasp the characteristics of the original sound from the monitor reproduction sound, and it is difficult to identify the person when the voice of the person is monitored.

A technique for avoiding such a problem is disclosed in JP-A-56-163568.
No. In the same publication, as a prior art, for example, a half of a 0.1-second interval symbol of a reproduced signal is sampled at every 0.2-second interval, code-modulated and written in RAM, and the time width is expanded to a time width of 0.2 seconds. It is envisioned that the technology will be read out. On the other hand, this conventional technique has a problem that click noise occurs when the level of the joint between signal waveforms changes abruptly.

Therefore, the technique described in the publication, for example, eliminates a large discontinuity between signal waveforms by combining read symbols from two RAMs at a portion where the signal level increases and at a zero-cross point.

(Problem to be Solved by the Invention) However, in the above-described technique, as in the conventional technique, the signals read alternately from the two RAMs at a cycle of 0.1 second are connected to each other, so that the level difference between them is completely zero. It is not possible. Further, since two RAMs having a sufficient recording capacity for storing the voice symbols are required, there remains a problem in terms of hardware.

Therefore, an object of the present invention is to provide a tape recorder with simplified hardware, which is useful for a high-speed dubbing monitor in which the spectrum of the original sound is not lost even in the monitor sound during high-speed dubbing and a monitor sound faithful to the original sound is obtained. To provide.

(Means for Solving the Problems) In order to solve the above-mentioned problems, a tape recorder according to the present invention is a tape recorder for high-speed recording of a high-speed reproduction signal, wherein the high-speed reproduction signal is sampled at a predetermined frequency into a digital signal. An A / D converter for conversion, and a ring memory for recording the output of the A / D converter, which has a fixed storage capacity in which its recording address is circulated and repeated, and a sampling frequency of the A / D converter. A read address counter that supplies a read address that is incremented at an integer frequency to the ring memory, and data that is read from the ring memory as an input,
A low-pass filter that extracts and outputs only a specified low-frequency component, and converts the output of this low-pass filter into an analog signal
And a D / A converter, and is configured to output the output of the D / A converter as a monitor sound.

(Example) Next, this invention is demonstrated, referring drawings.

FIG. 1 is a block diagram showing an embodiment of a tape recorder according to the present invention.

From the input terminal, a reproduction signal reproduced at high speed by one tape recorder is input and supplied to the recording circuit 1 of the other tape recorder.

The signal processed by the recording circuit 1 is sent to the recording head 5 through the bias trap 3 and recorded on the magnetic tape running at high speed. This recording operation is performed using the oscillation signal from the bias oscillator 4.

The reproduced sound from the input terminal (the spectrum of the original sound is converted to the high frequency range) is also supplied to the frequency conversion device 2.

The frequency conversion device 2 reproduces at high speed by one of the tape recorders, converts the reproduced sound of the original sound whose spectrum has been moved to the high frequency side into the original sound having the original spectrum, and outputs the original sound. That is, the frequency conversion device 2 is a device that performs inverse characteristic processing of the frequency conversion characteristic by high-speed reproduction, and a monitor faithful to the original sound can be obtained from the monitor output.

FIG. 2 shows a detailed configuration example using the digital signal processor (DSP) of the frequency conversion device 2 in FIG.

The playback signal from the input terminal is converted into a digital signal by the A / D converter 21, and the digital signal processor (DS
It is input to the ring memory 221 in P) 22 and stored.

The ring memory 221 has a fixed storage capacity, and its recording address is circulated and repeated. The digital signal stored at the designated address from the read address counter 222 is read from the ring memory 221.

The digital signal read from the ring memory 221 is input to the digital low-pass filter 223, low-frequency components are extracted, converted into an analog signal by the D / A converter 23, and sent to the monitor terminal as a monitor signal. It

The operation of the frequency converter shown in FIG. 2 will be described more specifically below with reference to FIG. 3 showing spectrum characteristics.

Assuming a monitor sound of a double speed dubbing deck, the tape reproduction speed is doubled, so that the reproduction frequency spectrum is converted to twice the frequency of the original sound spectrum in FIG. 3 (a). (FIG. 3 (b)). Therefore, the spectrum of the input signal to the digital signal processor (DSP) 22 is as shown in FIG. 3 (c).
Here, f1 represents the high frequency of the original sound, and fS represents the sampling frequency in the A / D converter 21.

Therefore, in order to obtain the same reproduction frequency as in normal speed reproduction, it is necessary to halve the data read speed from the ring memory 221. That is, the read address counter 222 increments once every two sample periods to read digital data from the ring memory 221.
For example, starting from the sampling time point n, the data D0 written (stored) at this time is output to the low-pass filter 223 during this sampling period. However, the data D1 written in the ring memory 221 at the time of (n + 1) is not read at the time of the sampling period of (n + 1) but is read at the time of (n + 2). This relationship is shown in FIG.

As described above, since the ring memory has a finite storage capacity and new data is written in a circulating manner, half of the data is lost after a certain period of time, and the reading is restarted from the latest data. By selecting the storage capacity of the ring memory at high speed, it is possible to obtain sufficient monitor sound to obtain frequency (spectrum) information of the original sound.

Thus, the spectrum of the signal read from the ring memory 221 is shown in FIG. This signal passes through the low-pass filter 223 and is output from the D / A converter 23.
The spectrum of this output signal is shown in FIG. The low-pass filter 223 removes aliasing noise centered on fS / 2 generated by the above processing.

(Effects of the Invention) As described above, according to the present invention, the reproduced sound obtained by high-speed reproduction of the original sound is subjected to the conversion processing of the frequency characteristic opposite to the frequency conversion by the high-speed reproduction to obtain a spectrum faithful to the original sound. Since we have a monitor sound with characteristics,
Not only is it possible to obtain a monitor sound that is close to the original sound even during high-speed dubbing, but a phosphorus memory that cyclically uses the memory is used, and the read frequency is set to an integer fraction of the write frequency in response to the high-speed playback speed. Just by reading, there is no processing to connect a signal waveform as long as 0.1 seconds unlike the conventional technology, and the specified writing frequency is several KH.
Since it is about z (the sampling frequency is usually about 40 KHz in Hi-Fi recording), the problem of the joint of the signal waveform does not occur. In addition, the hardware is simplified because a ring memory is used instead of two RAMs.

[Brief description of drawings]

1 is a block diagram of an embodiment of the tape recorder according to the present invention, FIG. 2 is a detailed block diagram of the frequency converter 2 in the embodiment of FIG. 1, and FIGS. 3 (a) to 3 (e) are FIG. 4 is a spectrum diagram for explaining the operation of the frequency converter shown in FIG. 2, and FIG. 4 is a diagram for explaining the operation of the frequency converter shown in FIG. 1 ... Recording circuit, 2 ... Frequency converter, 3 ... Bias trap, 4 ... Bias oscillator, 5 ... Recording head, 21 ... A / D converter, 22 ... Digital signal processor, 221 ... Ring memory, 222 ... Read address counter, 223 ... Low-pass filter, 23 ... D / A converter.

Claims (1)

[Claims] 1. A tape recorder for high-speed recording of a high-speed reproduction signal, comprising: an A / D converter for sampling the high-speed reproduction signal at a predetermined frequency and converting it into a digital signal; And a read address incremented at a frequency that is an integer fraction of the sampling frequency of the A / D converter, the ring memory having a storage capacity of With a read address counter and data read from the ring memory as input,
A low-pass filter that extracts and outputs only a specified low-frequency component, and converts the output of this low-pass filter into an analog signal
A tape recorder comprising a D / A converter, and outputting the output of the D / A converter as a monitor sound.