JPS58177044A - Pcm reproducer - Google Patents

Abstract

PURPOSE:To process the output applied with muting processing into a natural audible signal and to eliminate the unpleasant feeling of the reproduced output, by detecting the noise level included in a reproduced PCM signal and providing a noise level at the muting operation. CONSTITUTION:A PCM reproducer is provided with a noise generating circuit 7, the noise level included in a reproduced PCM signal outputted from a PCM reproduction processing circuit 1 is detected at the circuit 7, and the noise corresponding to the level is applied to a multiplier 8 of a signal switching circuit 14. The reproduced PCM signal from the circuit 1 is applied to a multiplier 2 of the circuit 14 and to a coefficient generating circuit 4, and a coefficient corresponding to a muting signal command is applied to the circuit 4 from a sequence control section 3. The output from the circuit 4 is applied to the multipliers 2, 8 and summed at an adder 9. At the operation of muting, the noise level is provided, the output processing of muting is formed into signals having audible naturality, and the unpleasant feeling of the reproduced output is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PCM reproducing device that reproduces information obtained by converting an audio signal into PCM, and particularly relates to an improvement in muter processing.

PCM playback devices generally play back PCM signals recorded on a magnetic chip 7, etc., so they can faithfully playback audio without being affected by tape distortion or noise.However, playback errors may occur in certain conditions. If a large amount of noise occurs, there is a risk that an audible click will occur.For this reason, the PCM playback device is equipped with a mute ink processing function to silence the playback sound during muting. The recorded audio signals generally have a certain noise level, and are converted into PCM including that noise.

For this reason, if normal mute ink processing is performed and a state with no noise is reproduced, the reproduction will feel unnatural.

The conventional equipment for this building will be explained below with reference to FIG.

A reproduction PC=M signal, which is an output of a PCM reproduction processing circuit (1) that reproduces a PCM signal from a recording medium such as a magnetic chip 11-source disk, is input to a multiplier (2).

On the other hand, the output of the coefficient generation circuit (4) generates coefficients corresponding to fade-out and fade-in processing in response to the regeneration state detected by the PCM regeneration processing circuit (1) and the mute ink command from the sequence control unit (3). is the coefficient of multiplier (2). The output of the multiplier (2) is converted into an IJ/Af converter (with digital analog conversion and low-pass filter characteristics).
5) and is sent to the audio output terminal (6).

Example 1 of the output waveform of the audio output terminal (6) is shown in Figure 2 (a).
Show the moon. The broken lines correspond to the coefficients of the coefficient generation circuit 14).

x 1 when not muting + x 0 during muting, fader - when muting ink is switched
Processing is in progress. FIG. 4B corresponds to the mute ink instruction signal.

Playback 4 - It can be seen that the signal head is smoothly faded out and no abnormal noise is generated, or there is no noise at all during muting. There is an inconvenience that this silence makes the sound unnatural.

This invention was made to eliminate the above-mentioned disadvantages, and includes a noise generation circuit that detects a noise level contained in a reproduced PCM signal and generates a noise signal according to the noise level, and a PCM reproduction processing circuit. Eliminates unnaturalness during muting by switching and outputting the reproduced PCM signal and noise signal according to the muting command signal that is issued when a reproduction error state is detected or the muting command signal sent from the sequence control unit. The purpose of the present invention is to provide a PCM reproducing device that can perform the following functions.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a PCM reproducing device according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same parts. In this device: - New number and noise generation circuit (7).

A multiplier (8) and an adder (9) are added, and the coefficient generation circuit (4) also generates coefficients for the multiplier (8). And coefficient generation circuit (4) 1 multiplier (2) 9 multiplier (8)
A signal switching circuit G for switching between the reproduced PCM signal and the noise signal is configured.

The noise generation circuit (7) has a function of detecting the noise level included in the reproduced PCM signal at the time of recording and a function of generating noise corresponding to the detected noise level, and the output of the noise generation circuit (7) is connected to a multiplier. (8) is input. The coefficient of the multiplier (8) is generated by the coefficient generating circuit (4) so that it becomes x0 during normal reproduction and x1 during muting.

Output waveform example g of the audio output terminal (6) according to the present invention
is shown in Fig. 4<c>. C in the same figure is the pc of the multiplier (2).
This corresponds to the output level C of the M signal, and the broken line corresponds to the coefficient of the multiplier (2). On the other hand, the figure (f) shows the P of the multiplier (8).
Corresponds to the output level f of the CM signal, and the broken line is the multiplier (8)
corresponds to the coefficient of Therefore, FIG. 4(C) is the same as FIG. 4(a).

This corresponds to the sum of the waveform C1i in (b). 4th I
N (b) is the mute ink instruction signal -0 In the above embodiment, the reproduction PCM signal output and the noise generation circuit (
The circuit was configured so that the outputs of 7) were both multiplied using multiplier +2) (8), but! As shown in figure J5, the number is reproduced by the selector aIl without using any multiplier.
The signal and the noise signal may be switched and output. Here, aα is a control circuit that generates a switching signal t16) for the selector dll in response to a reproduction error state detected by the PCM reproduction processing circuit () or a mute ink signal command from the sequence control unit (3). . In addition, as shown in FIG.
) may be configured without using.

Here, d2 is a multiplier (
This is a coefficient circuit that generates a control signal a9 of the circuit 1-03 that changes the coefficient of 2) and controls whether or not the noise output of the noise generating circuit (7) is added by the adder (9).

Several embodiments of the present invention have been described above, and detailed embodiments of the F noise generation circuit (7) will now be described.

The noise generation circuit (7) is roughly divided into a noise level detection unit (hereinafter referred to as (7a)) that detects the noise level during recording included in the reproduced PCM signal, and a noise level detection unit (hereinafter referred to as (7a)) that detects noise equivalent to the detected noise level. The noise generating part (hereinafter (7)
b) and).

An embodiment of the noise level detection section σ is shown in FIG.

The two-channel PCM signal from the PCMP4 raw processing circuit (1) is converted into an absolute value number by the absolute value converter (101) and stored in the flip-flop (102), and the output of the flip-flop (002) is Fritsuno Flop (103)
). Whether or not data is input to the flip-flop (103) is determined by a comparison between store data A of the flip-flop (102) and store data B of the flip-flop (103) in a comparator (104). When A>B, the data stored in the flip-frog (103) is updated. Comparator (10
4) is the sampling clock (10
5) works. On the other hand, the comparator α07 compares the store data B of the flip-flop (103) with the store data C of the flip-flop (106), and when B<C, the store data of the flip-flop (106) is updated. The comparator (107) operates for a certain period T
It operates with a clock (108) that is input every time (ec).

In this way, the maximum value of the amplitude occurring during the period T is changed to the minimum value Kmin or the output (
114), and this value corresponds to the amplitude value of noise during recording.

Fig. 8 shows its conceptual diagram. In the figure, each section from 1'1 to T61 has a certain period 'l', k1 to Ks is the maximum value of each section, and in this case, 1'4 is the minimum level at 4-3' min.
This is the section where 'k Ml was issued. The above configuration ζ
This allows the level of noise to be detected.

The above is an example of noise level detection. Another method is to use the fact that the noise level is dominated by high frequency components to create a digital high-frequency pass characteristic filter, and use its output to determine the noise level. There is a method for detecting the noise level in the above embodiment.At the same time, there is a simple high frequency pass characteristic filter that determines the difference between adjacent sample values as the noise level.

FIG. 9 shows an embodiment of the noise generating section (7b) that generates noise corresponding to the detection level of such noise.

In the figure, (109) is a random sequence generation circuit, which is combined with a soft register (110) and an exclusive OR (11
It consists of (1). This generated serial random sequence is converted into a parallel random sequence by a serial converter (112), multiplied by a noise level detector (7 detection result level 014) and a multiplier 113), and then output from the noise generating circuit ( 115).

Note that the above has only described one embodiment of the noise generation circuit (7), and various configurations from 1kN to 0 are possible as its configuration. For example, there is a method in which the multiplier (113) is not used and only a shift operation is performed. Also, random sequence generation circuit (
109) and before performing the correction process, the horse student P (L
There is also a method of using the M signal and outputting only the lowest hits corresponding to the noise level to substitute for noise. The conceptual table is shown in Figure 10.

The noise value number of the lower two bits of the C-force generated noise pattern of the tenth fixed reproduced PCM signal is the same, and the third dot from the lowest corresponds to the polarity bit number. Here, binary numbers are expressed in toes conbriment as l and n. The noise node (the one that generates the turn (the lower two bits of the above-mentioned reproduced PCM signal) C on the right side of the figure is set as the noise node (the lower two bits of the turn) C as shown by the arrow Al, and the other noise patterns are The value of the third lowest bit of the reproduced PCM signal corresponding to the detected noise level in this case may be substituted into each bit F as shown by arrow B.

Note that if the noise level is detected incorrectly, there is a risk that a large level of noise will be generated during the muting process, but as a countermeasure to this, determine the maximum value of the noise addition level, and then set the maximum value of the noise addition level to It is better to configure it so that it does not.

Furthermore, it would be convenient if the PCM reproducing apparatus is provided with a changeover switch so that the noise generating section can be changed over when not required, thereby enabling the conventional muting process.

Further, the noise addition level during muting may be lower than the noise detection level unless it is audibly unnatural.

As described above, the present invention adds a noise level during the mute ink operation, so the muting-processed output becomes audibly natural, and the PCM playback output is free from discomfort.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional PCM playback device;
144 is a diagram showing a reproduced output waveform by a conventional PCM reproducing device, FIG. 3 is a block diagram showing a PCM reproducing device according to an embodiment of the present invention, and FIG. 144 is a diagram showing a reproduced output waveform by the device in FIG. 5 and s6 are block diagrams showing a PCM reproducing device according to another embodiment of the present invention, and FIG. 7 is a detailed view of the noise level detection section (7a) of the noise generation circuit (7) according to the embodiment of the present invention. The block diagram shown in Figure 8 is j1!
7 is a waveform diagram for explaining the operation, FIG. 9 is a detailed block diagram of the noise generating section (7b) of the noise generating circuit (7),
FIG. 1O is a table showing a method of using a reproduced PCM signal instead of noise. Mountain... i-(, M regeneration processing circuit % (3)... sequence control section (muting command means), (71.
...Noise generation circuit, 041...Signal switching circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Makoto Kuzuno - Figure 1 Figure 2 (d) b No. 9 ■ Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 1987-60750 2,
Name of the invention Relationship to the case involving PCM regenerator 3, supplementary 1 Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Hitachi Katayama 4 , Agent address: 2-2-3-5, Marunouchi 2-chome, Chiyoda-ku, Tokyo Drawings subject to amendment (Figures 1 and 3) 6. Contents of amendment (1) Figures 1 and 3 as attached. correct. Above Figure 1

Claims (1)

[Claims] (1) A PCM reproduction processing circuit that reproduces a PCM signal from a recording medium, mute ink command means that outputs a mute ink command signal, and detects the noise level contained in the reproduced p c hi multiplied signal. A PCM reproducing device comprising: a noise generating circuit that generates a noise signal according to the noise level; and a signal switching circuit that switches between the reproduced PCM signal and the noise signal according to the mute ink command signal. . (2) The PCM reproducing apparatus according to claim 1, wherein the noise generating circuit generates a constant level of small signal noise using a random pattern. (3) The signal switching circuit performs switching between the reproduced PCM signal and the noise signal by a cross-fade process in which one of the two signals is faded in and the other is faded out. Range 1
The PCM reproducing device according to item 1 or 2. 14) The noise generation circuit divides the reproduced PCM signal into sections of a certain length of time, detects the maximum signal level within the section, and detects the minimum value among the maximum signal levels as the noise level. A PCM reproducing device according to claim 1 or 2, characterized in that: (5) The above-mentioned noise generation circuit divides the reproduced PCM signal into intervals of a certain length of time, detects the maximum difference between adjacent sample values within the interval, and detects the minimum value among the values as the noise level. A PCM reproducing device according to claim 1 or 2, characterized in that: (6) The above noise generation circuit is configured to generate F of the reproduced PCM signal.
2. The PCM reproducing apparatus according to claim 1, wherein the PCM reproducing apparatus generates a noise signal using the digit bit.