JPS6328144A - Demodulation device for quasi-momentary compression pulse code modulation signal - Google Patents

Abstract

PURPOSE:To obtain the optimum effect of a privacy system, by setting the upper limit of a scale value, and expanding a compressed data by a limited scale value in case of non-subscriber, while an identification signal which represents the presence/ absence of the privacy system is detected, and the privacy system is applied. CONSTITUTION:The compressed data is detected by a compressed data detecting means 1, and the scale value, by a scale value detecting means 2, and the identification code, by an identification code detecting means 5, from an input signal, respectively. The upper limit of a detected scale value is limited by a scale value limiting means 7, and the upper limit of the scale value is decided by an identification code 51. The compressed data detected by the compressed data detecting means 1 is expanded corresponding to the scale value whose upper limit is limited by a data expanding means 3. An expanded data is D/A-converted by every sound sample, thereby an analog signal can be obtained. And when the identification code shows the privacy of a PCM data, the amplitude of an audio signal D/A-converted at a time when the upper limit of the scale value is set, for example, at '1' is limited, and the effect of the privacy system can be obtained without applying excessive load on a sound equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a polarized quasi-instantaneous compressed speech pulse code modulation CPCM)tl[modulator.

Conventional technology A transmission signal that transmits a quasi-instantaneous compressed audio PCM signal is divided into compressed sample data and an amplitude range that includes the maximum value of the amplitude of the sample data for each block in blocks at predetermined time intervals. It is basically composed of a scale value indicating .

Furthermore, when the transmitted data is polarized, an identification code is added to the data in order to determine whether polarization has been performed in the demodulator. Polarization is achieved by multiplying part or all of the transmitted data by tU (random code sequence (hereinafter referred to as PN code sequence)).

FIG. 2 shows a block diagram of a conventional quasi-instantaneous compressed PCM signal demodulation device, in which 1 is a compressed data detection means, 2 is a scale value detection means, 3 is an expansion means, 4 is a D/A conversion means, 5
6 is an identification code detection means, and 6 is a decoding means.

It consists of a quasi-instantaneous compressed audio PCM signal, a scale value, an identification code, etc. for each block. From the transmission signal, the compressed data detection means 1 detects the compressed data, the scale value detection means 2 detects the scale value, and the identification code detection means 5 detects the identification code. The compressed data is expanded by the expansion means 3 according to the scale value. The expanded PCM signal is converted into an analog signal by the D/A converter 4. The identification code detected by the identification signal detection means 5 is
It is given to the decoding means 6 as a control signal for depolarizing the device that has subscribed to the service. For devices that do not subscribe to the service, there is no decoding device 6 (or it does not work), so the digital code sequence obtained by multiplying the original PCM signal by the PN code sequence is directly demodulated into the D/A converted audio signal. (For example, Satellite Broadcasting Receiving Technology Investigation Committee Report Part 2 - Satellite Broadcasting Receiver Part 2 Desired Performance Appendix-2) Problems to be Solved by the Invention However, in the above configuration, polarization is not possible. When a voice signal is demodulated using a demodulation device that does not subscribe to the service, the following problems occur.

Since compressed data is multiplied by a PN code sequence,
In the decompressed data, bits are set randomly from the upper bit to the lower bit, regardless of the original PCM data.
The analog signal obtained by D/A converting this PCM data becomes a large amplitude impulse signal with a certain probability. The larger the scale value, the larger the amplitude of the impulse signal. This large-amplitude impulse signal is supplied to audio equipment such as amplifiers and speakers, causing problems such as overloading these equipment and causing discomfort to non-subscribers due to the degree of opening.

The present invention provides a demodulation device that demodulates a quasi-instantaneous compressed voice PCM signal that has been polarized by multiplying it by a PN code, without overloading external equipment even when the signal is not subscribed to. The purpose is to supply.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention detects an identification signal indicating the presence or absence of polarization, and determines the upper limit of the scale value when polarization is applied and if the user is not subscribed. The compressed data is expanded using this limited scale value.

According to the present invention, even when the scale value sent is large, the scale value is limited by a predetermined upper limit, so that the amplitude of the audio signal is limited by the level determined by the upper limit of the scale value.

Therefore, there is no overload on the sound wm device, and an appropriate privacy effect can be obtained.

Embodiment FIG. 1 is a block diagram showing an embodiment of a quasi-instantaneous compressed pulse code modulation signal demodulating apparatus according to the present invention.

1 is compressed data detection means, 2 is scale value detection means, 3
4 is a data expansion means, 4 is a D/A conversion means, 5 is an identification code detection means, and 7 is a scale value limiting means. The input signal 11 includes PCM data obtained by quasi-instantaneous compression of the audio signal, a scale value at the time of quasi-instantaneous compression, and an identification code indicating whether or not polarization has been performed. When polarization is applied, the PCM data is multiplied by a PN code sequence.

From this input signal, compressed data detection means 1 detects compressed data, scale value detection means 2 detects a scale value, and identification code detection means 5 detects an identification code.

The upper limit of the detected scale value is limited by the scale value limiting means 7. The upper limit of this scale value is determined by the identification code 51. The compressed data detected by the compressed data detection means 1 is expanded according to the scale value whose upper limit is limited by the data expansion means 3. The expanded data is D/A converted for each audio sample to obtain an analog audio signal.

Here, the rules for quasi-instantaneous companding are 14 bits - 8 bits, 8 bits
This will be explained by taking 14 bits as an example.

FIG. 3 shows the 8-bit to 14-bit expansion rule.

There are 7 scale values from 1 to 7, and 7 is the original P
The amplitude of the sample of the CM signal is the maximum range. The decompression process results in a bit array of sample data as shown in FIG. 3 depending on the scale value.

When the scale value is 7, the compressed data is arranged in order from the upper bits of the 14 bits, and each time the scale value becomes smaller, it is shifted towards the lower bits, and the upper bits are placed in the polarity bin) (
The same sign as MSB) is placed, and the sample is expanded so that the amplitude of the expanded sample becomes small.

In FIG. 1, when the identification code indicates polarization of PCM data, when the upper limit of the scale value is limited to 1, for example, the D/A
The amplitude of the converted audio signal is limited, and an appropriate polarization effect can be obtained without overloading the audio Wia device. When the identification code indicates that polarization has not been performed, the original audio signal can be reproduced by setting the upper limit of the scale value to 7. Furthermore, by fixing or limiting the scale value, even when the ratio of multiplication of PN code sequences is low, it is possible to impart unnaturalness to the reproduced sound, thereby enhancing the confidential conversation effect.

In the above example, the case where a linear PCM signal is quasi-instantaneously companded is explained, but the same effect can be obtained by other quantization methods, for example, when a differential PCM signal is quasi-instantaneously companded.

Effects of the Invention As described above, according to the present invention, by limiting the upper limit of the scale value, an appropriate polarization effect can be obtained without overloading the sound 9 equipment for polarization, and Accordingly, it is possible to realize a demodulator for quasi-instantaneous pressure 1i p CM audio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a demodulating device for a quasi-instantaneous compressed signal, which is an embodiment of the present invention, FIG. 2 is a block diagram of a conventional demodulating device for a YJL instantaneous compressed signal, and FIG. 3 is a rule for quasi-instantaneous companding. FIG. 1... Compressed data detection means, 2... Scale value detection means, 3... Expansion means, 4...
... D/A conversion means, 5 ... identification code detection means, 6 ... decoding means, 7 ... scale value limiting means. Name of agent: Patent attorney Toshio Nakao Idiot 1-I
To @ proboscis also to −ni

Claims (1)

[Claims] A pulse code modulation audio signal is divided into blocks each having a predetermined number of sample data and subjected to quasi-instantaneous compression, compressed sample data obtained by this quasi-instantaneous compression, and a scale value indicating the degree of compression for each block; The polarization is performed by multiplying a part or all of the compressed data and the scale value by a pseudo-random code sequence, and the transmission signal is formed to include an identification code indicating the presence or absence of polarization. when the identification code is detected, an identification code detection means for detecting the identification code, a scale value detection means for detecting the scale value, a scale value limiting means for setting an upper limit of the scale value detected by the detected identification code, and a restriction. 1. A quasi-instantaneous compressed pulse code modulation signal demodulating device, characterized in that it demodulates a transmission signal by comprising a decompression means for decompressing the compressed data detected by the scale value.