JPS60106079A - Pcm reproducer - Google Patents

Abstract

PURPOSE:To remove return noises at the time of reproduction by making breaking frequency of a band restriction low-pass filter variable in accordance with variable sampling frequency at the time of reproduction for sampling frequency at the time of recording. CONSTITUTION:A signal F from a clock generator 11 is supplied to a low-pass filter 10. The signal F is a breaking frequency control signal of the low-pass filter 10, which is generated by the clock generator 11 from an oscillation output of a variable oscillator 13 changed in accordance with pitch control, etc. When the oscillation frequency of the variable oscillator 13 becomes higher than that at the time of recording, the signal F makes the cutoff frequency of the low-pass filter higher, and when the oscillation frequency of the variable oscillator 13 becomes low, the signal F makes the cutoff frequency of the low-pass filter 10 lower. Since the cutoff frequency of the low-pass filter for band restriction 10 is changed in accordance with sampling frequency at the time of reproduction for sampling frequency at the time of recording, generation of return noises at the time of reproduction can be satisfactorily prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a PCM playback device that can be used in a PCM playback device that records or plays back digital signals, such as a digital recording playback device or a digital audio disc playback device.
This relates to a CM playback device.

Configuration of a conventional example and its problems A conventional PCM reproducing apparatus will be explained using FIGS. 1 to 5. Figure 1 is a block diagram of a digital recording string, where the source is the input analog signal, (1) is the low-pass filter with a low band limit set to 11 sampling wave numbers, and (2) is the sample band-limited analog signal. Analog digital/L/& conversion tg (hereinafter referred to as F “A/119
``exchanger''. ), 131 is an error detection gl positive code addition block that determines the ability to prevent data dropout, and (4) is an error detection and correction encoded digital 1 block.
A recording device necessary for recording No. d on a recording medium such as a V'l'R tape or an optical disk (Recording No. 1J to be recorded on a recording medium, (5) is supplied to the above system. The clock generation 4g generates a sampling wave number k/1) at the timer 12). (6) is a crystal copying element for clock generation J.

Figure 2 shows the band-limiting low-pass filter (1
) and A/D hair change a12) is an explanatory diagram specifically explaining sampling using frequencies and numbers. Here, rs is the sampling frequency, and the occupied area IC shown in one diagonal line represents the response of the band-limited low-pass filter (υ).

On the other hand, Figure Ig3 is a block diagram of a digital reproduction thread that reproduces a recording medium on which such digital recording has been performed.
) is reproduction number 16 from the recording medium, (7) is the demodulator, (8
) is data error 9 detection correction and interrogation processing Grotsk-19
1&″i Daiji///L/・Analog conversion 4i (hereinafter '
It is written as "D/8 to change Ig" below. ), uci is a low-pass filter, (E] is a reproduction analog number 1, and dll is a clock generation for the reproduction yarn. if- is a crystal oscillator.

Here, the purlin frequency for digital recording systems will be explained. In the first place, sampling literally refers to the operation of reading an analog signal at a certain point in time, and sampling is generally performed at blue time intervals, and the reciprocal of that interval is called the purlin frequency. By the way, the analog number 1d with finite frequency and bandwidth is
It does not deteriorate even if it is sampled. According to the sampling theorem, if sampling is performed with M number of stations at least 2 in the 16th band,
This is because all the information of IJi No. 118 is included in the sample string. Sunawachi, band + T [Hz] (the above t'
The original symbol χitl of s/2) can be expressed using the ridgepole χ(nT), where n: integer, T: m-length interval. This equation shows that the original signal can be reproduced by passing all samples through a low-pass filter of band -i'i'[:iiZ]. On the other hand, if the band limitation during sampling is incomplete, the sampled signal 1d will have a direct deviation in the spectrum μ. This straight wave is called aliasing noise because the spectral distribution beyond the sampling frequency 1 is folded back into the signal band, and the aliasing noise generated in the low-pass filter during sampling and playback is It cannot be separated in subsequent processing.

Against this background, pitch control functions for restricting pitch and reproducing have recently been widely used in PCM reproducing devices such as digital audio discs and PCM recorders. In such a case, envy < i shown in Figure 4
Using J corpse oscillation <gu3t-, clock generator I in Fig. 3
This is done by making the iD oscillation source variable.

The pitch control /L/@+ of the conventional example as above
In the PCM reproducing device with t@, since the band-limiting low-pass filter Uυ has a custom-made fixed cutoff frequency, the purlin theorem described in Ill is no longer applicable, and aliasing noise increases.

Purpose of the Invention The present research aims to eliminate the above-mentioned conventional drawbacks, and is a PCM playback device in which the sampling frequency at the time of recording is different from the sampling frequency at the time of playback, which can reduce aliasing noise, improve harmonic distortion rate and The purpose of this invention is to provide a PCM playback device that can effectively prevent deterioration of custom-made audio such as H.

4th aspect of the invention In order to achieve the above object, the PCM playback device of the present invention uses a band-limiting low-pass filter according to the sampling INN wave pressure during playback, which is varied with respect to the sampling frequency during recording. 4
This is a well equipped with means for monitoring the first frequency.

DESCRIPTION OF EMBODIMENTS An embodiment of the invention will now be described with reference to the drawings.

FIG. 8g5 is a circuit block diagram of a PCM reproducing apparatus according to an embodiment of the 911 system, in which the same components as those shown in FIG.

The feature of this embodiment is the clock generator (issue 1d from the publication).
This signal IF"l is supplied to the pitch control /L/
etc. 1c Accordingly, the oscillation output of the variable oscillator 1 is reduced by i, and the clock is generated from the oscillation output of the variable oscillator. If the cutoff frequency of the low-pass filter uO is higher than that of
On the other hand, if the oscillation frequency of the variable oscillator becomes lower, this is the first step to lowering the cutoff frequency of the low-pass filter ild.

Figure 6 is an explanatory diagram of the operation of the low-pass filter uO.
indicates the same frequency as during recording, and the cutoff frequency is fa
/2. Further, (G) shows the case where the frequency is lower than that at the time of recording, and fI) shows the case where the frequency is higher.

In this way, the cutoff W1 frequency of the low-pass filter uO for band limitation is varied according to the sampling frequency during playback that is different from the sampling frequency during recording.
The occurrence of aliasing noise during playback can be effectively prevented.

Detailed Description of the Invention/Thus, according to the present invention, 1 ton of specimen at 4 vinegar hours
l, 1. 1. The sampling frequency during reproduction is varied with respect to the lil wave number. Since the cut-off frequency +iu of the low-pass filter for band control is changed to ijIf, it is possible to eliminate the noise caused by υr during reproduction, and its industrial utility value is extremely high.

[Brief explanation of the drawing]

Fig. 1 is a 1ll16 block diagram of the digital recording system, Fig. 2 is an explanatory diagram of the relationship between the sampling HJ wave number of the digital recording string and the interception frequency e of the band control tuyere-pass filter, and Fig. 3 The figure is a circuit block diagram of conventional digitally recycled yarn.
The figure shows the conventional de-f for pitch control, etc.
FIG. 5 is a circuit block diagram of the main part of the digital regenerated yarn. FIG. It is an explanatory diagram. (7)...Demodulator, (8)...Error accumulation/correction and interpolation processing group, 19+...υ/A fmg
g, u (卜...low-pass filter, iJ, ])...
Clock generator, - 11 city light imitation street agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. 3J band-limiting low-pass filter according to the sampling frequency during playback, which is different from the sampling frequency during recording. PC that was able to bite the iJ transformation method that makes 4 Moe frequency angry
M reproduction equipment d0