JPS61121615A - Muting device for decorder of dpcm coding - Google Patents

Abstract

PURPOSE:To reduce a pulse noise at muting by providing the 1st gate and the 2nd gate to the output of a DPCM coder and the input of a DPCM decoder so as to make zero a transmission difference signal thereby reducing gradually an analog output. CONSTITUTION:The ON/OFF of muting based on the request of a DPCM coder is controlled by the 1st control terminal 61 and the ON/OFF based on the request of the DPCM decoder is controlled at the 2nd control terminal 81. Since a transmission data in 8-bit is muted digitally before and after a transmission line by the muting ON in both the cases, the DPCM decoder acts that other difference data are zero. That is, the data subject to nonlinear extansion by an inverse quantizer 9 is zero as well, then an input to a leaked integration device 10 is zero and since no new integration data exists, the output of the leakage integration device holds the preceding value. However, since the leaked component exists, the output of the leakage integration device is reduced gradually and reaches zero for some time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to DPCM (Diff
rental Pulse Code Modula
tion) This relates to a circuit configuration of a muting device of a code decoder.

2. Description of the Related Art Mining devices using PCM technology have already been commercialized in the form of compact discs, players, and the like.

(For example, Compact Disc Player 5L-Pa manufactured by Matsushita Electric Industrial ■).

The above prior art is a muting device for a linear PCM decoder. In the conventional technology, muting is performed digitally at the input of the D/A converter.
If applied to a muting device for an M-code decoder, the result will be as shown in FIG.

In FIG. 3, in the DPCM encoder, the first gate 6
Passage of digital data of the D converter 1 is opened and closed, and when it is closed, the sound is turned off.

In the DPCM decoder, the second gate 8 also performs a similar operation. A prediction loop consisting of a quantizer 3, an inverse quantizer 4, and a leakage integrator 6 and an adder 2 constitute a nonlinear differential PCM code section, and an inverse quantizer 9 and a leakage integrator 10 form a nonlinear differential PCM code section. It constitutes a differential PCM decoding section. The leakage integrator 5 and the leakage integrator 10 are constructed as shown in the block diagram shown in FIG.

In Fig. 4, 51 is an input terminal, 12 and 16 are adders, 13 is a delay device, the 14-bit data is shifted by n bits (n is a positive integer) to the LSB side (usually the right side), and the left side is the M
This is a bit shifter that pads SB. The output of the delay device 13 and the output of the delay device 13 are shifted by the pit shifter 14 by -2(-n
) The multiplied data is added (subtracted) in an adder 15 to make it slightly smaller than the original data, which is then added to the input data in an adder 12 and applied to the input terminal of a delay device 13 in a loop. . This operates as an integrator with leakage.

Problems to be Solved by the Invention According to the above configuration, the analog output waveform during muting is the D/A waveform when the second gate 8 in FIG. 3 is closed.
Since digital muting is performed at the input of the converter, the signal suddenly becomes 0 level as shown in FIG. Also, when the first gate 6 in FIG. 3 is closed, the signal obtained through coding and decoding is the same as that in FIG. 5. If the audio signal is suddenly and violently clamped to the 0 level in this way, a problem arises in that pulse noise is generated and is unpleasant to the listener's senses.

Means for Solving the Problems The present invention solves the above problems by connecting the first gate and the second gate to the output side of the DPCM encoder and the DPCM encoder, respectively.
This is provided on the input side of the PCM decoder.

Effect: With the above-described configuration, the present invention reduces pulse noise during muting by gradually reducing the analog output by reducing the transmission difference value signal to zero instead of reducing the input/output signal itself to zero. It is something.

Embodiment FIG. 1 is a block diagram showing an embodiment of a muting device for a DPCM code decoder according to the present invention.

1 is a 16-bit A/D converter, 2 is a 16-bit adder,
3 is a quantizer that performs nonlinear compression from 16 bits (7) to 8 bits, 4 is an inverse quantizer that performs nonlinear expansion from 8 bits to 16 bits, and 5 is a leakage integrator that performs 16 bits. , input terminal 61.16 bit.

It has an output terminal 62. Further, 6 is an i1 gate and has a first control terminal 61. 100 is D which summarizes the above
It is a PCM encoder and the signal from the analog input terminal is
PCM encoding is performed and 8-bit digital data is output to the transmission line 7 from the digital output terminal.

Further, 8 is a second gate and has a second control terminal 81 . 9 is an inverse quantizer for non-linear expansion from 8 bits to 16 bits; 10 is a leakage integrator having a 16-bit input terminal 101 and a 16-bit output terminal 102; 11 is a 16-bit D/A converter. 20o is a DPCM decoder that combines the above, and receives 8-bit digital data from the transmission line 7 at a digital input terminal, performs DPCM decoding, and outputs an analog signal from an analog output terminal.

Based on the request from the DPCM encoder side (muting on,
The muting is turned off by the first control terminal 61, and the muting is turned on and off by the second control terminal 1 based on a request from the DPCM decoder. In any of the above cases, when muting is turned on, 8 bits 1. Since the transmission data of the two signals is digitally muted before and after the transmission path, the DPCM decoder operates as if the difference value data were zero.

In other words, the data non-linearly expanded by the inverse quantizer 9 is also zero,
Therefore, since the input to the leakage integrator 1o is zero and there is no new integrated data, the leakage integrator output maintains the previous value. However, since there is a leakage component, the leakage integrator output gradually decreases and becomes zero after a while. This data is D
/A converter 11 converts the signal into analog and outputs it. Second
The figure shows this operation as an analog output waveform.

As is clear from a comparison between FIG. 2 and FIG. 5 of the conventional example, it can be seen that this embodiment reduces pulse noise caused by muting being turned on. Furthermore, in the conventional example, the first gate and the second gate are placed after the 16-bit A/D converter and before the 16-bit D/A converter, so
A 6-bit transmission line was required, but in this embodiment, since they are placed before and after an 8-bit transmission line, the effect of compression of the transmission band can be obtained as a secondary effect, and there is an economical advantage that each 8-bit transmission line is sufficient.

Effects of the Invention As described above, according to the present invention, with an extremely simple block configuration, pulse noise caused by turning on muting can be reduced, a natural-looking muting effect can be obtained, and it is also economically superior. A muting device for a DPCM code decoder can be realized.

[Brief explanation of the drawing]

Fig. 1 is a professional diagram showing a muting device for a DPCM code decoder according to an embodiment of the present invention, Fig. 2 is a waveform diagram of its main parts, and Fig. 3 is a muting device for a conventional DPCM code decoder. FIG. 4 is a detailed block diagram of the leakage integrator, and FIG. 6 is a waveform diagram of the main part of the conventional example. 1...A/D converter, 2...Adder,
3... Quantizer, 4... Inverse quantizer,
5... Leakage integrator, 6... First gate, 7... Transmission line, 8... Second gate,
9...Inverse quantizer, 1o...Leak integrator, 11...D/A converter, 51...
Leak integrator input terminal, 52...Leak integrator output terminal, 61...First control terminal, 81...
・Second control terminal, 100...DPCM encoder,
200...DPCM decoder. Name of agent: Patent attorney Toshi Nakao, male, and one other person Desecration of drawings Document (Method) % Formula % 2 Name of Invention Relationship with the Case of Person Who Corrects Muting Device 3 of DPCM Code Decoder Patent Application Address 1006 Kadoma, Kadoma City, Osaka Name Name (
582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Hiuchi 6 Amendment Order Date October 29, 1985 A. Amendment Contents (1) “Figure 1...” on page 8, line 3 to line 8 of the specification.
It is... ' will be corrected as follows. FIG. 2 is a block diagram showing a muting device of a conventional DPCM code decoder, FIG. 3 is a detailed block diagram of a leakage integrator, and FIG. 4 is a waveform diagram of essential parts of the conventional example. (2) The drawing numbers of Figures 2, 3, 4, and 6 have been corrected to Figures 1, 2, 3, and 4 as written in red on the attached sheet. Masu. Procedural amendment Showa 6'F January 27 2 Name of the invention Muting device for DPCM code decoder 3 Relationship to the case of person making amendments Patent application Address 1006 Kadoma, Kadoma City, Osaka Name Name
(582) Matsushita Electric Industrial Co., Ltd. Representative Yama
Toshihiko Shimo 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 6 Subject of amendment 4, Brief explanation of drawings Drawing 6, Contents of amendment (1) Specification page 8 Lines 3 to 8 “Figure 1...
It is... ' will be corrected as follows. ``Figure 1 is a block diagram showing a muting device for a DPCM code decoder according to an embodiment of the present invention, Figure 2 is a waveform diagram of its main parts, and Figure 3 is a diagram showing a muting device for a conventional DPOM code decoder. 4 is a detailed block diagram of the leakage integrator, and FIG. 5 is a waveform diagram of the main part of the conventional example." (2) Drawings 1, 2, 3, and 5. Add Figure 4 No.

Claims (3)

[Claims] (1) Consisting of a DPCM code section including an A/D converter and a prediction loop, and a first gate, the first gate is
D provided between the CM code section and the digital data output terminal and configured to mute digital data.
DP including PCM encoder, second gate and prediction loop
It consists of a CM decoding section and a D/A converter, and the second gate is provided between a digital data input terminal and a DPCM decoding section including a prediction loop, so as to mute the digital data depending on the reception state etc. 1. A muting device for a DPCM code decoder, comprising: a DPCM decoder. (2) The muting device for a DPCM code decoder according to claim 1, wherein the prediction loop includes a quantizer, an inverse quantizer, and a leakage integrator. (3) D according to claim 2, wherein the leakage integrator is composed of an adder, a delay device, and a bit shifter.
Muting device for PCM code decoder.