JPH01307075A - Digital recording and reproducing device - Google Patents

Abstract

PURPOSE:To correct the dislocation of an editing point and the delaying of a monitor output by providing a means to switch from a reproducing signal to an analog signal at the time of recording the insertion, a means to switch from the monitor output of the reproducing signal to the analog input signal and a delaying circuit of the same delaying quantity as the delaying time of first and second digital filters. CONSTITUTION:When the insertion recording is executed by the punching-in, a signal is reproduced from a magnetic tape 1 with a reproducing head 2 at a reproduction mode, made into a digital signal by a reproducing signal processing circuit 4, the prescribed quantity only is delayed by a second digital filter 6, A/D-conversion 8 is executed through a cross fader 7 and a monitoring output is obtained from an A point. Next, a recording amplifier 17 is operated, a reproducing recording mode is obtained, and then, the reproducing signal of a C point is delayed by a delaying circuit 5 and added from a D point through a cross fader 15 to a recording signal processing circuit 16. The signal is added through the recording amplifier 17 to a magnetic head 18, and the time when the magnetic tape 1 comes from the reproducing head 2 to the head 18 and the delaying time of the signal channel when it comes from the head 2 through the circuit 5, the fader 15, etc., to the head 18 are made coincident.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a digital recording and reproducing apparatus that has a punch-in/out function and that can be applied to a digital audio tape recorder or the like that performs oversampling.

[Conventional technology]

2. Description of the Related Art Conventional digital recording and reproducing devices are known to have a so-called pan-nine/out function, which rewrites a portion of a signal already recorded on a recording medium with a new signal in order to edit a signal. Various types of recording media are used, such as magnetic tapes, magnetic disks, magneto-optical disks, and semiconductor memories. Here, a digital recording/reproducing apparatus using magnetic tapes will be described. FIG. 3 is a block diagram showing a conventional digital recording and reproducing apparatus having a pan-nine/out function. In the figure, 1 is a magnetic tape that is transported in the direction of arrow a, 2 is a reproducing head that reproduces the magnetic tape 1, 3 is a reproduction amplifier that amplifies the output of the reproduction head; 4 is a reproduction signal processing circuit that performs signal detection, demodulation, data deinterleaving, error correction, etc. on the output of the reproduction amplifier 3 to produce a reproduction signal; 11 is an analog signal , 20 is a low-pass filter for removing aliasing noise to which an analog signal is supplied, 21 is an A/D converter driven at a sampling frequency f that is twice the analog signal band, 15 is a reproduced signal processing circuit 4 A first signal for smoothly switching between the reproduction signal obtained from the A/D converter 21 and the output of the A/D converter 21 at a predetermined timing to form a recording signal.
In this embodiment, the crossfader 1
5 is used. Reference numeral 16 denotes a recording signal processing circuit that performs addition of an error correction code, data interleaving, modulation, etc. to the recording signal obtained from the crossfader 15;
7 is a recording amplifier that amplifies the recording signal processed by the recording signal processing circuit 16; 18 is a recording head that records the recording signal amplified by the recording amplifier 17 onto the magnetic tape 1; They are placed separately. 22 is a D/A converter supplied with the recording signal obtained from the crossfader 15 and driven at a sampling frequency f; 23 is a D/A converter;
A low-pass filter for removing aliasing noise is supplied with the output of the /A converter 22, and 10 is an output terminal from which the output of the low-pass filter 23 is taken out. Next, the operation will be explained. When recording inserts using Pan-Nine, first,
In the reproduction mode, a signal is reproduced from the magnetic tape 1 by the RAD 2, and this signal passes from the reproduction amplifier 3 to the reproduction signal processing circuit 4 and becomes a digital reproduction signal. At this time, the crossfader 15 has selected the playback signal side,
This reproduced signal is obtained as a monitor output from the output terminal 10 through the D/A converter 22 and the low-pass filter 23. Next, when a portion of the magnetic tape 1 slightly before a predetermined editing point reaches the reproducing head 2, the recording amplifier 17 is operated to establish a reproducing/recording mode. As a result, the recording signal from the crossfader 15 is transferred to the recording signal processing circuit 16.
The signal is applied to the recording head 18 through the recording amplifier 17 and recorded on the magnetic tape 1. In this case, the time taken for the magnetic tape 1 to reach the recording head 18 from the reproduction head 2 and the signal reproduced by the reproduction head 2 are determined by the reproduction amplifier 3. Reproduction signal processing circuit 4. Crossfader 15. Recording signal processing circuit 16. If the time required for the signal to be applied to the recording head 18 through the recording amplifier 17 is made to match, the reproduced signal can be recorded on the same portion of the magnetic tape 1 again. Next, when the editing point of the magnetic tape 1 comes to the playback head 2, the cross-fade mode is activated, and the cross-fader 15 is set to A.
/Select the D conversion side. The analog signal input from the input terminal 11 is then filtered through the low-pass filter 20. ^/D converter 21. A recording signal is generated through the cross fader 15, and this recording signal is applied to the recording head 18 through the recording signal processing circuit 16 and recording amplifier 17, thereby being recorded from the edit point on the magnetic tape 1. During this recording, the recording signal is obtained as a monitor output from the output terminal IO through the D/A converter 22 and the low-pass filter 23. When the above recording is completed, punch-out is performed and insert recording is completed. Note that the punch-out operation is performed by switching the crossfader 15 from the A/D conversion side to the reproduction signal side, contrary to the punch-in operation. As described above, in the punch-in/out operation, the signal input from the input terminal 11 is synchronized with the playback signal, so that there is no time lag on the magnetic tape 1 and the connection between the two signals is smooth. It will be held in In the above-mentioned digital recording/reproducing device, the sampling frequency f of the A/D converter 21 and the D/A converter 22 is
, and since we are using a frequency twice the signal band,
The low-pass filters 20 and 23 are required to have attenuation characteristics that drop sharply at f,/2 in order to remove aliasing noise caused by sampling. As a result, phase rotation becomes severe in the upper part of the signal band, causing problems in high-frequency transmission characteristics. To solve this problem, oversampling techniques have traditionally been used. FIG. 4 is a block diagram showing a digital recording/reproducing apparatus using oversampling. In the figure, 1 to 4, 10, 11, 15 to 18 indicate the same parts as in FIG. 12 is a low-pass filter to which the analog signal input from the input terminal 11 is added;
A type having a gentle attenuation characteristic from 2 to fl is used. 13 is an A/D converter to which the output of the low-pass filter 13 is applied, and is driven at a sampling frequency of 2f. 14 is the sampling frequency 2f of the A/D converter 13
. 6 is a first digital filter for linear decimation of the phase characteristic to lower the signal to f, and 6 is a linear interbolation filter of the phase characteristic to increase the sampling frequency fs of the recording signal obtained from the crossfader 15 to 2fs. second digital filter for eyes, 8
is a D/A converter to which the output of the digital filter 6 is added, and is driven at a sampling frequency of 2 fs. 9 is D
A low-pass filter to which the output of /A converter 8 is added
, /2 to f3 with gentle attenuation. According to the above configuration, since the low-pass filters 12.9 with gentle attenuation characteristics are used, the phase rotation of the analog signals passing through these low-pass filters 12, 9 is reduced. In addition, the A/D converter 13 and the D/A converter 8 perform sampling at twice the normal sampling rate, but the first digital filter 14 returns the sampling rate to the original sampling rate, and the second digital filter 14 returns the sampling rate to the original sampling rate. Filter 6 allows the original sampling rate to be doubled. Figure 5 shows linear FIR (Finite) phase characteristics.
2 shows a conceptual circuit configuration of a digital filter of the Inpulse Re5 pose type. This digital filter is similar to the first and second digital filters 1 in FIG.
4.6. In the figure, 30 is a digital signal input terminal, 31 is a delay element synchronized with the sampling period of the input digital signal and connected in multiple stages, and 32 is a coefficient al+a2 . . . a7 for the output of each delay element 31, respectively. 33 is an adder that adds each output of the multiplier 32; 34 is an adder that adds each output of the multiplier 32;
is an output terminal to which the output of the adder 33 is added. Note that the coefficients al+ a2 . . . a7 are symmetrical about the time axis. According to the above configuration, the digital signal input from the input terminal 30 is sequentially delayed by the multiple stages of delay elements 31, and the coefficient a1ga! is applied to the output of each delay element 31.
By multiplying by a7 and adding these multiplied values, a digital output having predetermined filter characteristics can be obtained from the output terminal 34. If the digital recording/playback device handles audio signals,
90d for the first and second digital filters 14 and 6
Attenuation characteristics of B or higher are required. In order to realize this, a large number of delay elements 31 are required, and the number of taps is 100 or more. In that case, the amount of delay is between the A/D side and the D
/A side is more than 1 m5ec, which is within the detectable range for humans.

[Problem a that the invention seeks to solve]

Conventional digital recording and reproducing devices are configured as described above, so when performing punch-in/out operations, the first
And the delay time of the second digital filter 14.6 becomes a problem. That is, in FIG. 4, during punch-in/out, the connection point between the recorded signal and the new signal is predetermined on the magnetic tape 1 due to the delay time of the first digital filter 14. It will be shifted after the edit point. Further, the monitor output obtained from the output terminal 10 is also delayed by the delay time of the second digital filter 6. When recording music, etc., you may perform while monitoring the playback sound from the monitor output, and perform insert recording at a predetermined timing. In such cases, if the monitor output is delayed, , it became impossible to perform accurate insert recording. This invention was made to solve the above-mentioned problems, and even when performing punch-in/out while performing oversampling using a digital filter, the editing point does not shift, and the monitor It is an object of the present invention to provide a digital recording/reproducing device that does not cause output delay.

[Means to solve the problem]

The digital recording and reproducing device according to the present invention switches between the reproduced signal obtained by delaying the reproduced signal by the sum of the delay times of the first and second digital filters and the output of the first digital filter via the first signal switching means. At the same time, a monitor output is obtained by D/A converting the reproduced signal through the second digital filter and the A/D conversion output through a second signal switching means. The signal switching timing of the first signal switching means is delayed from the signal switching timing of the second signal switching means by the delay time of the first digital filter.

[For use]

The first and second signal switching means and reproduction signal delay circuit of the present invention correct the editing point shift and monitor output delay based on the delay times of the first and second digital filters.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figures, 1 to 4, 6.8 to 18 refer to figures 3 and 4.
Since they correspond to the same reference numerals in the figure, their explanation will be omitted. 5 is a delay circuit for delaying the reproduced signal obtained from the reproduced signal processing circuit 4 and supplying the delayed signal to the crossfader 15; a first delay time τ of the first digital filter 4;
Second delay time τ of the second digital filter 6
. It has a total delay time of τ, +τ2. Reference numeral 7 denotes a second signal switching means for switching between the reproduced signal and the output of the A/D converter 13, and in this embodiment, a cross fader 7 is used. Note that a cross fader 15 is used as the first signal switching means 15. 1
9 is an input terminal for a timing signal for operating the crossfaders 15 and 7; 20 is a delay circuit for delaying the timing signal by the first delay time τ and applying the delayed signal to the crossfader 15; FIG. 2 shows a timing chart of signals at points 0 to 0 in FIG. Next, the operation will be explained. When performing punch-in, first, in the playback mode, the playback signal obtained from the playback signal processing circuit 4 at the 0 point has its sampling rate doubled by the second digital filter 6, and is delayed by τ1, so that the playback signal obtained from the 0 point crossfader 7
The signal is applied to the D/A converter 8 via the D/A converter 8. As a result, the monitor output is obtained at the point 0. When the recording amplifier 17 is operated a little before the editing point and enters the playback recording mode, the 0
The reproduced signal at the point is delayed by +τ2 at the delay circuit 5,
The signal is applied from point 0 to the recording signal processing circuit 16 via the cross fader 15, and further applied to the recording head 18 via the recording amplifier 17, thereby being recorded on the magnetic tape 1. In this case, the time it takes for the magnetic tape 1 to reach the recording head 18 from the reproduction head should be made to match the delay time of the signal path from the reproduction head 2 to the recording head 18 via the delay circuit 5, crossfader 15, etc. As a result, the reproduced signals are recorded on the same portion of the magnetic tape 1. Next, when the editing point comes to the playback head 2, the analog signal input from the input terminal 11 (point 0) becomes a digital signal through the low-pass filter 12 and the A/D converter 13. This digital signal is applied to the crossfader 7 from point 0, and is returned to the original sampling rate by the first digital filter 14, and then τ. is added to the crossfader 15 from the 0 point with a delay of .times. At this time, the crossfader 7 first performs a smooth signal switching operation according to the timing signal input from the input terminal 19 (point 0), and then the timing signal of the 0 point delayed by τ1 in the delay circuit 20 causes the crossfader 7 to switch smoothly. 1
5 performs the signal switching operation smoothly. According to the above, as shown in Figure 2, point ■, point ■, and 0
The edit point whose timing is aligned with the point is the crossfader 1
On the input side of 5, the 0 point, ■ point, ■ point are all set at the same time, and as a result, the editing operation by the crossfader 15 is performed at the editing timing that coincides with the input of the analog signal, and the Editing is performed without being affected by the delay time of the second digital filter 14.6. Also, the monitor output during insert recording is input terminal 11, low pass filter 12, A/D converter 13, cross fader 7,
D/A converter 8, low pass filter 9 and output terminal 10
Since there are no large delay elements such as the first and second digital filters 14 and 6, a delay-free monitor output can be obtained. In addition, in the above embodiment, the sampling frequency of oversampling was set to 2fs, but it is 4fs. The frequency may be 8f, . . . , etc. Also the first
and a crossfader 15 as a second signal switching means.
．． 7 was used, but other switches may be used as long as they do not generate abnormal sounds when switching signals and can smoothly switch signals.

【Effect of the invention】

As described above, according to the present invention, the first signal switching means switches from the playback signal to the analog input signal during insert recording, and the second signal switching means switches from the monitor output of the playback signal to the monitor output of the analog input signal. Since the structure is configured to include a delay circuit having the same delay amount as the delay time of the first and second digital filters for performing oversampling, even though it performs oversampling, editing points due to punch-in/out cannot be changed. This has the effect of providing no deviation and no delay in monitor output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a digital recording and reproducing device according to an embodiment of the present invention, FIG. 2 is a timing chart showing signal timing in each part of the device, and FIG. 3 is a block diagram showing a conventional digital recording and reproducing device. Figure, 4th
The figure is a block diagram of the same device with an oversampling technique added, and FIG. 5 is a circuit configuration diagram of an FIR type digital filter. 4 is a reproduced signal processing circuit, 5 is a delay circuit, 6 is a second digital filter, 7 is a cross fader, 8 is a D/A converter, 13 is an A/D converter, 14 is a first digital filter, 15 16 is a recording signal processing circuit, and 2o is a delay circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Corporation G: ■ Points.

Claims (1)

[Claims] A first digital filter is provided on the output side of the A/D converter, and a second digital filter is provided on the input side of the D/A converter, and oversampling is performed in the A/D converter and the D/A converter. In a digital recording/reproducing apparatus configured to perform the above-mentioned functions and having a punch-in/out function, the reproduced signal is passed through a first delay means having a delay time equal to the total delay time of the first and second digital filters, The output of the first delay means and the output of the first digital filter are made into a recording signal via the first signal switching means, and the output of the A/D converter and the reproduction signal are made into the second signal. The signal passed through the digital filter is supplied to the D/A converter via the second signal switching means, and the signal switching timing of the first signal switching means is set based on the second signal. A digital recording/reproducing apparatus characterized in that the switching timing is delayed by the delay time of the first digital filter.