TW454166B - Sub-band plus mute speech coding system - Google Patents

Abstract

A sub-band coding system for storing and reproducing a speech subdivides a speech into sub-bands. In each sub-band, signals below a threshold level is considered as mute, and that above the threshold level is considered as non-mute. Upon modulation (e.g. by adaptive differential pulse-code modulation), the mute signal is converted into mute data to represent the starting time and duration of the mute period, while the non-mute signal is converted into non-mute data to represent signal levels. During replay, the mute data and the non-mute data are combined before conversion into different sub-band analog signals. The different sub-band analog signals are then summed to reproduce the original voice.

Description

Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 454166 B; 5. Description of the invention (/) The invention relates to the technology of sub-band coding and mute to achieve the storage and reproduction of sound signals. In general, the instant signal of speech generally includes some silent periods, and these periods of silence generally occupy about 120% to 40% of the total time. Such a signal can be converted into a digital audio signal to facilitate transmission and reproduction. Conventional signal processing methods include code modulation (PCM), delta modulation, and differential pulses: ^ _change ((ADPCM), etc.) When using these modulation methods, different ^ must be used. Interval, sample the speech signal, and quantify it into many potentials. The advantage of these conventional techniques is that their control circuit is quite simple, but the disadvantage is that it requires a lot of memory, so 'how to reduce the required memory , Without sacrificing the quality of the sound, is still the research theme of concern until now.

Wan et al., U.S. Patent No. 4,70-1,937, propose a system for storing and reproducing fixed pattern signals. The silent periods of the signals are not stored but regenerated. The signal of the silent period is modulated by pulse code modulation technology. During the silent period, the decoder of the storage memory is not activated, but during other periods, the storage memory is activated, so a large storage capacity is required. . The storage capacity required for both periods needs to be reduced. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to reduce the total storage memory capacity required for a sound storage and reproduction system. .. In each sub-band of a sub-band coding system, adding the mute period can achieve the above purpose. First set a critical potential, and then convert the letter 5 below the critical potential into mute data, which is expressed by the start time and duration of the mute period, and the signal above the critical potential is transformed into Non-silent data in terms of signal potential. Both silent and non-silent data are stored in memory. Since the signal potential of the mute period is zero, there is no need to store such a potential. Therefore, the sub-band coding technology plus the signal potential of the mute period is not stored. More memory capacity. (Please read the precautions on the reverse side before filling out this page) Binding · Order 1 2 This paper size is applicable to the Chinese country (CMS > A4 size (210X297 mm) -----————-— Note 1 (a) illustrates a typical time-domain waveform of a sound signal. _L (b) illustrates the continuum of the signal corresponding to Figure 1 (a). Figure 2 illustrates the sub-band and mute system of the present invention. Figure 3 Describe the encoder required to implement the present invention using the adaptive differential pulse code modulation technique "Fig. 4 illustrates the decoder required when implementing the present invention using the adaptive differential pulse code modulation technique. Gg The principle of sub-band coding technology is: In the frequency response of a sound, the / spectrum is not evenly distributed. Generally speaking, the _ in the intermediate frequency range will be greater than the high frequency range, so when the voice signal is transformed into a digital signal, The high __ range can be expressed in fewer bits than the IF range. This principle can be explained mathematically. Assume that the frequency of the impulse signal is BW1, the number of bits is Bitl, and the frequency of the high-frequency signal is BW2. , The number of bits is Bit2. Then, the required memory amount Ms is Data Rate (datarate) said that it is equal to:

Ms = BWl XBitl + BW2xBit2 (1) where Bit2 <Bitl; If the sub-band coding technology is not used, the amount of memory M required by the system is equal to: M = BW1 XBitl + BW2 XBitl (2) This is because regardless of the IF range or In the high-frequency range, the worst-case number of bits, Bitl, is required. When using sub-band coding technology, the required memory amount Ms will be less than M, because the Bit2 < Bitl ° Employee Welfare Committee of the Central Bureau of Standards of the Ministry of Economic Affairs prints it in a dual-band sub-band coding system. The silent mute period will appear in In the IF and HF bands, these silent periods occupy considerable memory space. J_… 4,701,937_ US patent mentioned that because of the emergence of the silent period, there is no need to store the zero signal data of this silent period, so the memory capacity can be saved. In the present invention, a voice is divided into two or more frequency bands, for example: a high frequency band and a low frequency band. There is a critical potential in each frequency band. Signals below this threshold are called “subband coding quiet ^ 1”; during the subband coding silence period, the zero signal is not stored in the memory. This paper size applies to China National Standards (CNS) 8-4 U10X297 mm) 4 Printed by the Staff Welfare Committee of the Central Standards Bureau of the Ministry of Economic Affairs 5 4 _2 illustrates the basic embodiment. First, a "low-pass filter" (LPW) and a "high-pass filter" (HPl) are used to divide a sound into a low-frequency range and a high-frequency range. The low-frequency signals transmitted by LP1 and the high-frequency signals transmitted by HP1 are detected by the critical silence detectors MDO and MD1, respectively. After detection, the signal leads to a memory and management unit MMU to determine the signal above the critical potential, which should be stored in the memory RAM. In the present invention, at least two sub-bands, that is, a high-frequency band and a low-frequency band, are respectively divided into mute data and non-mute data. The figure illustrates the time-domain waveform of a sound signal, and Figure 1 (b) illustrates the corresponding frequency spectrum. It can be seen from Fig. 1 (a) that there are some silent periods with no signal, marked with "A", and there are periods with small signal, marked with "B". In the present invention, if the signal in the "B" period is lower than a certain critical potential, it is regarded as mute. The relative spectral response is narrower than the silent response shown in Figure 1 (b) with a blank gap. During these silent periods, the signal potential is zero. These zero signals do not need to be converted into digital data and stored in memory. The digital data of these silent periods is called "silent data", which is only represented by "the start time and duration of the silent period". The required memory capacity M3 can be calculated by the following formula: M3 = BW0XBit0 + BWl 'XBitl + BW2XBit2 (3) Among them, BWO and BitO are the frequency bandwidth and number of bits during the mute period, and BW11 and Bitl are the frequency bandwidth and number of bits for the IF bandwidth. Since the number of bits in the silent period is zero, M3 = BWl'XBitl + BW2XBit2 (4) M3 in equation (4) will be smaller than Ms in equation (1) because the bandwidth BW1 · is less than BW1. Therefore, the total memory space required for the sub-band frequency band and the mute system of the present invention will be smaller than the conventional high- and low-frequency-band coding system, and smaller than the system proposed by Wan et al. That does not store the silent period. Figures 3 and 4 illustrate the schemes for encoding and decoding using the adaptive differential pulse coding modulation method, respectively. This architecture differs from Figure 1 because both the high and low frequency subbands include mute and non-mute data. In the encoding process illustrated in Figure 3, the input signal is divided into N frequency bands by "band-pass" filters BP0, BP1, ..., BPN. The filtered signals are modulated by the modulators MO, Mb, ... MN, so that they are converted into digital signals. The digital signal is detected by the mute detectors MDO, MD1, ..., MDN, and the low paper size is applied to the Chinese national standard (CNS> Α4 specification (2 丨 0 father 29 today mm) 4 5 4 1 6 6 h3 is critical The potential signals are eliminated; the signals above the critical potential are adapted to the differential pulse code modulators ADPCM (), ADPCM1, ... ADPC1 ^, respectively, to be converted into non-silent digital data. The adaptive differential pulse code is adapted. Passed data is stored in the memory element, but does not store the zero-potential data of the mute period; signals below the critical potential, only the information such as the start time and duration are stored as mute data. In the decoder of Figure 4 The data of different sub-bands stored in the memory RAM are sent to different ADPCM decoders DECODEO, DECODE1, ... DECPDEN. The signals from the decoder are then sent to the respective mute generators MG0, MG1, ... MGN, The zero-potential data of the mute period is inserted. The inserted mute data includes the start time and duration of the mute period. Then it is sent to the demodulation devices DMO, DM1, ... DMN, which will include the mute period information. The included data is converted into digital signals, and then sent to the band-pass filters BPO, BP1, ... BPN. Finally, the digital signals are mixed in a synthesis unit S to produce an output sound signal. From the above analysis, The dual sub-band architecture is used as an example for illustration. However, people in the same industry should understand that this architecture is also applicable to architectures with more than two sub-bands. Although the encoder used in Figure 3 and the decoder used in Figure 4 are both It is an ADPCM system, but other modulation systems are also applicable. The description of the foregoing example is only used as an example ^ This is not intended to limit the scope of the applicant's rights. For those in the same industry, anyone who applies the present invention The application or transfer of skills to other types of equal skills, whether the products they perform are better or worse, are the scope of rights claimed by the inventor of this case. Staff Welfare Committee, Central Standards Bureau, Ministry of Economic Affairs Will print New Zealand 7 9 2

Claims (1)

Printed by the Consumer Standards Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs. Patent application scope 1. A voice encoding and decoding system using both sub-band and mute at the same time, comprising: more than one frequency filtering device for filtering the aforementioned sound signals into different frequencies A modulation device that modulates the aforementioned audio signal into digital data in the aforementioned sub-band; a separating device that separates the aforementioned digital data into the following two kinds of data in at least one of the aforementioned sub-bands: (a) Mute data: set the aforementioned data below a critical potential as mute data 'and represent it by the start time and duration of the mute period; and 0 >) non-mute data: set the aforementioned signal high The data at the aforementioned critical potential is set as non-silent data; a storage device is used to store the aforementioned silent data and non-silent data in a memory element. 2. A speech encoding 'decoding system using both sub-band and mute simultaneously as described in item 1 of the scope of the patent application, wherein the aforementioned separation device uses a mute detector. 3. As described in item 1 of the scope of the patent application, a speech encoding and decoding system using both sub-band and mute simultaneously, further including an encoding device, so as to store the aforementioned mute data and non-mute data in the aforementioned memory element, Encode it. 4. A voice coding and decoding system using sub-band and mute at the same time as described in item 3 of the scope of the patent application, wherein the aforementioned coding device uses an "adapted differential pulse code modulator" (ADPCM). 5. A speech encoding and decoding system using subband and mute simultaneously as described in item 1 of the scope of patent application, wherein the aforementioned memory device uses random access memory. 6 'A voice encoding and decoding system using both sub-band and mute, which can reproduce the sound signal with digital data. The sound signal of the digital data is represented by more than one sub-band, and has (a) the aforementioned The mute data whose signal is lower than a critical potential, and expressed by the start time and duration of the mute period, and (b) the non-mute data where the aforementioned signal is higher than the aforementioned critical potential; includes: a regenerative device, In at least one sub-band, the aforementioned mute data and non-mute data are reproduced into the aforementioned digital data; ^ a demodulation device that demodulates the aforementioned digital data into a sub-band f tone signal; a filtering device in the aforementioned In the sub-band, the aforementioned sub-band sound signals are filtered; a synthesizing device mixes all the aforementioned sub-band sound signals to provide sound output. 7. A voice coding and solution system using both sub-band and mute at the same time, which can reproduce the sound signal of digital data with "Adjustable Differential Pulse Code Modulation" (ADPCM) ^ The sound signal of the aforementioned digital data consists of more than one Those indicated by the sub-frequency band and having (a) the aforementioned paper whose signal is lower than a critical potential are applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) (please read the precautions on the back before filling this page) ),? τ 4 54 1 6 6 Α8 Jiwubu ... D8, the scope of application for patents, printed data of employees' cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs, and expressed by the start time and duration of the silent period And (b) the non-mute data whose aforementioned signal is higher than the aforementioned critical potential; including: an ADPCM decoder, which reproduces the aforementioned non-muted data for the aforementioned sub-band; a muting generator, which reproduces the aforementioned in the aforementioned sub-band Mute data; demodulation split, in the aforementioned sub-band, demodulate the digital data from the aforementioned ADPCM decoder and the aforementioned muting generator to make it into Speech signal: Band-pass filter to filter the aforementioned sub-band voice signals: and a synthesis amplifier to mix the aforementioned sub-band voice signals. 8. ^ An encoding method using both a sub-band and a mute speech encoding and decoding system, the steps of which include: filtering-filtering the aforementioned sound signal into at least two sub-bands; transformation-converting sound in at least one sub-band Signal into a digital signal containing the following two items of data: & (a) mute data below a critical potential and expressed as the start time and duration of the mute period; and Φ) the aforementioned sound is higher than the aforementioned Critical potential non-silent data; and storage-storing the aforementioned silent data and non-silent data in a memory. 9. An encoding method for a speech encoding and decoding system using both sub-band and mute, as described in item 8 of the scope of the patent application, wherein the aforementioned memory is added in the form of "adapted differential pulse code modulation" (ADPCM) Coded. 10. —A decoding method using a sub-band and mute speech encoding and decoding system, which can decode digital data of a voice signal encoded by the sub-band and mute speech. The aforementioned digital data of a sound signal has (a) The aforementioned mute data whose sound signal is lower than a critical potential, and represented by the start time and duration of the mute period, and (b) the 'non-mute data' where the aforementioned sound signal is higher than the aforementioned critical potential, including: regeneration -In at least one of the aforementioned sub-bands, regenerating the aforementioned digital data from the aforementioned muted data and non-muted data; demodulation-demodulating the aforementioned digital data into a sub-band voice signal; filtering-for the aforementioned Filter the sub-band sound signals; and mix-mix all the aforementioned sub-band sound signals into the aforementioned sound signals (please read the precautions on the back before filling out this page) This paper standard applies to the Chinese National Standard (CNS) Μ Specifications (210X297 mm)