JP2006349848A - Band expanding device and deficient band signal generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal which includes a component similar to a wide-band signal from the beginning as a signal after band expansion. <P>SOLUTION: A deficient band signal generator of the present invention generates a signal component of a deficient band due to limitation from an input signal whose frequency band is limited to a low band or high band. The deficient band signal generator has a frequency shift means of shifting a frequency component of the input signal toward the deficient band by a specified frequency and a component extracting means of extracting a component within the deficient band range from the output signal of the frequency shifter and outputting the deficient band signal. A band expanding device of the present invention is equipped with such a deficient band signal generator and an adding means of adding the output deficient band signal and the input signal to each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a band extension device and a shortage band signal generator, and can be applied to, for example, a device that broadens a voice signal from a narrowband telephone or an exchange.

  Currently, voice communication such as telephone is actively performed using various networks. However, in accordance with the customs of the era when the conventional public network was used, telephone voice communication is generally limited to a frequency of 300 Hz to 3.4 kHz called a telephone band. However, speech uttered by humans includes low frequency components of 300 Hz or lower and high frequency components of 3.4 kHz or higher. These low frequency components and high frequency components are also related to the individuality of speech. It is an important ingredient. In addition, the lack of these low-frequency components and high-frequency components not only lacks individuality but also contributes to a decrease in speech recognition, and calls using voices containing these components are desired.

  However, an exchange in a general public network cannot transmit voice exceeding the telephone band. In addition, since the transmission side terminal is designed based on this practice even in a network other than a general public network, there is a problem that it is impossible to transmit voice exceeding the telephone band. In view of such points, Patent Document 1 proposes a band expander that expands a voice band.

  The band extender method described in Patent Document 1 will be described with reference to FIG. A narrowband audio signal (digital signal) DC whose frequency is limited from 300 Hz to 3.4 kHz is input to the band expander 10. The narrowband audio signal DC is converted into a converted original signal S whose sampling frequency is increased by the sampling frequency converter 11 (for example, from 8 kHz to 16 kHz). Extended signal (synthesized low frequency signal) LS extended to 300 Hz or less), extended signal (synthesized high frequency signal) HS extended to the high frequency side (3.4 to 7 kHz), extended signal (synthesized unvoiced signal) with the unvoiced part expanded ) US is generated by the low-frequency signal generator 12, the high-frequency signal generator 13, and the unvoiced signal generator 14, and is added by the conversion original signal S and the adder 15 to generate the band extension signal V. ing.

This band extension signal V simultaneously provides a low-frequency component signal, a high-frequency component signal, etc. generated from a band-limited narrowband audio signal DC together with the transmitted signal, and a wideband including these components. This makes it possible to listen to the sound as if it were a signal.
Japanese Patent Laid-Open No. 9-258787

  However, in the band expansion method of Patent Document 1, since only one type of frequency component is added to the low frequency side, the frequency of a specific value and its harmonic components are expanded, but not expanded as a whole low frequency band. However, there is a problem that the sense of reality is insufficient, and the ability to generate sound similar to the wideband signal from the beginning is insufficient.

  Therefore, there is a demand for a band extension device and a deficient band signal generator that can realize a signal similar to the original wideband signal after band extension.

  A shortage band signal generator according to a first aspect of the present invention generates a signal component of a band that is limited and insufficient from an input signal whose frequency band is limited to a low band or a high band. Frequency shift means for shifting the frequency component of the signal by a specific frequency to the insufficient band side, and component extraction means for extracting the component of the insufficient band range from the output signal of the frequency shifter and outputting the insufficient band signal It is characterized by that.

  The band extending apparatus according to the second aspect of the present invention includes the insufficient band signal generator according to the first aspect of the present invention, and an adding means for adding the insufficient band signal output from the insufficient band signal generator and the input signal. It is characterized by that.

  According to the band extending apparatus and the insufficient band signal generator of the present invention, a component is uniformly added to a band of frequency components limited in an input signal, and a signal similar to a wideband signal from the beginning is realized. Can do.

(A) First Embodiment Hereinafter, a first embodiment in which the band extending apparatus and the insufficient band signal generator according to the present invention are applied to a voice band extending apparatus will be described with reference to the drawings.

(A-1) Configuration of the First Embodiment FIG. 1 is a block diagram showing the configuration of the voice band extending apparatus 100 according to the first embodiment. In FIG. Are given the same reference numerals.

  In FIG. 1, a speech band extending apparatus 100 according to the first embodiment includes a sampling frequency converter 11, a low-frequency signal generator 12, a high-frequency signal generator 13, a silent part signal generator 14, and a low-band signal generator. 20 and an adder 90.

  Here, the sampling frequency converter 11, the low-frequency signal generator 12, the high-frequency signal generator 13, and the unvoiced signal generator 14 are the same as those described in Patent Document 1, respectively. However, the method of generating the synthesized low frequency signal LS, the synthesized high frequency signal HS, and the synthesized unvoiced signal US for generating the band extension signal V is not limited to that described in Patent Document 1, and other existing methods are used. It may be applied.

  The voice band extending apparatus 100 according to the first embodiment is different from the conventional one in that the low band signal generator 20 is provided and the adder 90 is different from the conventional one. Incidentally, the conventional adder 15 adds and synthesizes four types of signals. The adder 90 of the first embodiment is different from the conventional one in that five types of signals are added and synthesized. For example, the adder 90 adds and synthesizes five types of signals by weighted addition using five types of weighting coefficients whose sum is 1.

  The low band signal generator 20 receives the converted original signal S whose sampling frequency has been converted by the sampling frequency converter 11 and outputs the combined low band signal LLS to the adder 90. The adder 90 is a combination of the low-frequency signal generator 12, the high-frequency signal generator 13, the unvoiced signal generator 14, and the low-band signal generator 20, the combined low-frequency signal LS, the combined high-frequency signal HS, and the combined unvoiced signal US. And the synthesized low-band signal LLS is synthesized to obtain and output a band-extended audio signal V.

  Hereinafter, first, the low-band signal generator 20 will be described with reference to FIGS. 3 and 4. 3 is a block diagram showing the internal configuration of the low-band signal generator 20, and FIG. 4 is a block diagram showing the internal configuration of the frequency shifter 21. As shown in FIG.

  As is clear from FIG. 1, the digital signal whose sampling frequency is converted by the sampling frequency converter 11 is input to the low-band signal generator 20. In the case of the first embodiment, it is assumed that the processing is performed in units of audio frames (frames) in which a specific time (for example, 10 ms) is grouped, but the time length of the frame is not limited. Further, the processing is not limited to a fixed frame, and a variable-length frame may be used.

  In FIG. 3, the low-band signal generator 20 includes a frequency shifter 21, a signal determiner 22, a waveform converter 23, a component extractor 24, and a switch 25.

  The signal determination unit 22 receives the converted original signal S whose sampling frequency has been converted by the sampling frequency converter 11 and determines whether the processing of the frequency shifter 21 is enabled or disabled by sound / silence determination or the like. Is output to the switch 25.

  The switch 25 receives the conversion original signal S and the signal determination information SL, and switches the output destination of the conversion original signal S to the frequency shifter 21 or the waveform converter 23 based on the signal determination information SL.

  The frequency shifter 21 receives the converted original signal S, generates a converted signal CS whose frequency is shifted to the low frequency side, and outputs the converted signal CS to the component extractor 24. 4A and 4B show examples of the internal configuration of the frequency shifter 21, and the function of each part will be clarified in the explanation of the operation.

  The waveform converter 23 receives the converted original signal S, generates a converted signal CS having a low-band component in which the sound component in the converted original signal S is reduced, and outputs the converted signal CS to the component extractor 24.

  The component extractor 24 receives the converted signal CS, extracts a predetermined low band component in the converted signal CS, and outputs it as a synthesized low band signal LLS.

(A-2) Operation of the First Embodiment Next, the operation of the voice band extending apparatus 100 of the first embodiment will be described. In the first embodiment, the following operation is performed every time one audio frame is input.

  When a narrowband audio signal (digital signal) DC is input to the audio band extension device 100, the narrowband audio signal DC is converted into a converted original signal S whose sampling frequency is increased by the sampling frequency converter 11. (For example, 8 kHz to 16 kHz) Using this converted original signal S, the low-frequency signal generator 12, high-frequency signal generator 13, unvoiced signal generator 14, and low-band signal generator 20 A signal LS, a synthesized high-frequency signal HS, a synthesized unvoiced signal US, and a synthesized low-band signal LLS are generated, and an adder 90 generates these four types of synthesized low-frequency signal LS, synthesized high-frequency signal HS, synthesized unvoiced signal US, and synthesized The band extension signal V is generated by adding the low band signal LLS and the conversion original signal S described above.

  As described above, the low-band signal generator 20 inputs the converted original signal S for each voice frame, generates a low-band signal having a frequency lower than the telephone band as a synthesized low-band signal LLS, and adds the adder 90 Output to.

  In the low-band generator 20, the signal determination unit 22 calculates, for example, the power of the converted original signal S for each voice frame, determines whether the converted original signal S is valid or invalid from the power value, and determines the result. The signal determination information SL is output to the switch 25. In the first embodiment, the case where the signal is invalid refers to a case where the converted original signal S is sounded, and corresponds to a section where the speaker is speaking. For example, it corresponds to a portion where a harmonic structure of voice appears. Further, the case where the signal is valid means a case where the converted original signal S is silent, and corresponds to a portion where the speaker does not speak or a portion where the harmonic structure of the voice does not appear. . Therefore, even in the effective portion of the signal, that is, the silent portion, the component of the signal itself is often not zero. The determination is performed, for example, by setting a threshold value for the power value, and determining that there is no sound if the power is lower than the threshold value, and that there is sound if not. This threshold may be selected as appropriate and is not limited to a specific value. The method is not limited to the above method as long as it is a method for determining whether the signal is valid or invalid (for example, any of existing sound / silence determination methods can be applied). Furthermore, in the above description, the case where the converted original signal S is used for the power calculation has been described. However, the narrowband signal DC may be used instead of the converted original signal S, and the determination is possible if the power in the audio frame can be determined. The signal to be used is not limited.

  The switch 25 outputs the input conversion original signal S to the frequency shifter 21 when the signal determination information SL is instructed to be valid (no sound), and the signal determination information SL is instructed to be invalid. At that time (when there is sound), the input conversion original signal S is output to the waveform converter 23.

  If the frequency of the sounded part is simply changed as described later, the harmonic structure peculiar to the sounded part is changed, so that there is a possibility that the listener will be heard if there is an abnormal sound. Therefore, in the first embodiment, when the synthesized low band signal LLS is generated, the voiced portion and the silent portion are processed separately.

  The frequency shifter 21 receives the converted original signal S for each voice frame, shifts the frequency of the received converted original signal S to the low frequency side by a frequency shifting method described later, and uses the shift result as the converted signal CS. It outputs to the component extractor 24. In the first embodiment, the frequency shift amount is set to 300 Hz, but is not limited to this value.

  The outline of the frequency shift method applied by the frequency shifter 21 will be described with reference to FIG.

  FIG. 4A illustrates the concept of the frequency shift method according to the first embodiment. An input original signal corresponding to the converted original signal S input to the frequency shifter 21 is defined as sin (f · t). f represents an angular frequency corresponding to the frequency of the original signal, and t represents time. Further, F is an angular frequency corresponding to the frequency to be shifted. For example, F is an angular frequency corresponding to −300 Hz. Here, the negative frequency is used to shift to a lower frequency by the frequency shift.

  First, the original signal sin (f · t) is multiplied by the cosine wave signal cos (F · t) by the multiplication circuit 62. By this multiplication, a first multiplication result of sin (f · t) cos (F · t) is obtained. In parallel, the phase of the original signal sin (f · t) is delayed by π / 2 by the delay circuit 61, and a second multiplication circuit is applied to the delayed original signal sin (f · t−π / 2). Multiply -sin (F · t) by 63. By this multiplication, a multiplication result of −sin (f · t−π / 2) sin (F · t) = cos (f · t) sin (F · t) is obtained.

  These two multiplication results sin (f · t) cos (F · t) and cos (f · t) sin (F · t) are added by the adder circuit 64. Thereby, an addition result of sin (f · t) cos (F · t) + cos (f · t) sin (F · t) = sin ((F + f) · t) is obtained. This addition result sin ((F + f) · t) is a signal obtained by shifting the frequency of the original signal by a frequency corresponding to the angular frequency F.

  4A shows a configuration in which a signal sin ((F + f) · t) obtained by shifting the signal of the frequency f by the angular frequency F by the delay circuit 61, the two multiplying circuits 62 and 63, and the adding circuit 64 is shown. However, in consideration of component extraction processing (filter processing) by the component extractor 24 to be described later, the signal from the frequency shifter 21 only needs to include the frequency component sin ((F + f) · t).

  The configuration shown in FIG. 4B forms a signal including the frequency component sin ((F + f) · t) from the input signal sin (f · t). That is, when the input signal sin (f · t) is multiplied by the cosine wave signal cos (F · t) by the multiplication circuit 65, sin (f · t) cos (F · t) = {sin ((f + F) · t) + Sin ((f−F) · t)} / 2 is obtained, but if only the sin ((f + F) · t) term is extracted, the frequency shift method of FIG. Can be used.

  The frequency component f of the input signal sin (f · t) includes various components, but any frequency component f is shifted by a fixed frequency F.

  The waveform converter 23 receives the converted original signal S determined to be sound (invalid) from the switch 25 and converts it so that the converted original signal S is close to silence by the waveform conversion method described later (waveform compression). ) And output to the component extractor 24 as a converted signal CS. In this waveform conversion method, for example, the square value of the absolute value of each sampled value of the frame of the input converted original signal S is added to the sign of the sampled value. In other words, regardless of positive or negative, only the amplitude is reduced to the square root. The waveform conversion method is not limited to this. For example, the power in the frame may be calculated, the waveform value may be divided by the power, and then the frequency shift may be performed. In any case, it is only necessary to output a signal having a low-band component in which a sound component is reduced.

  The component extractor 24 extracts, for example, a low-band component of 300 Hz or less from the converted signal CS from the frequency shifter 21 or the waveform converter 23 that is operating effectively at that time, and generates a combined low-band signal. The result is output to the adder 90 as LLS. The component extractor 24 is provided because the frequency structure of the conversion signal CS exists at 300 Hz or more, and is provided for extracting a necessary frequency band. As the component extractor 24, for example, a low-pass filter that passes 300 Hz or less can be applied.

  Note that the upper limit frequency (for example, 300 Hz or less) extracted by the component extractor 24 may be the same frequency as the maximum frequency that can be output by the low-frequency signal generator 12.

(A-3) Effects of the First Embodiment According to the audio band extending device of the first embodiment, the band extension signal V obtained by extending the band from the original signal (narrow band audio signal DC or converted original signal S). Since the extended signal component is generated as a band signal for a low frequency, the frequency component can be added as a whole in the low band. As a result, it is possible for the listener to listen to a sense of spread of the entire low range. In addition, it is possible to eliminate the low-band shortage that has been heard when a specific frequency component is added. As a result, the sound quality of the output signal can be improved.

(B) Second Embodiment Next, a second embodiment in which the band extending apparatus and the insufficient band signal generator according to the present invention are applied to a voice band extending apparatus will be described with reference to the drawings.

  The overall configuration of the voice band extending apparatus according to the second embodiment can also be represented by FIG. 1 according to the first embodiment.

  The second embodiment is different from the first embodiment in the internal configuration of the low-band signal generator (reference numeral 30 is given to the second embodiment), and the others. Is the same as in the first embodiment.

  FIG. 5 is a block diagram showing an internal configuration of the low-band signal generator 30 according to the second embodiment. The same reference numerals are given to the same and corresponding parts as those in FIG. 3 according to the first embodiment. ing. In FIG. 5, the low-band signal generator 30 of the second embodiment includes a signal determiner 22, a waveform adjuster 28, a frequency shifter 21, and a component extractor 24.

  The signal determiner 22 determines whether the converted original signal S is valid (silent) or invalid (sound) in the same manner as in the first embodiment, and gives the signal determination information SL to the waveform adjuster 28.

  The waveform adjuster 28 receives the conversion original signal S and the signal determination information SL, and outputs the adjustment signal AS to the frequency shifter 21. When the waveform adjuster 28 determines that the sound is silent based on the signal determination information SL, the waveform adjuster 28 outputs the input conversion original signal S as it is as the adjustment signal AS. On the other hand, when the waveform adjuster 28 determines that the sound is sound based on the signal determination information SL, the waveform adjuster 28 adjusts the conversion original signal S to obtain an adjustment signal AS. The method of adjusting the waveform by the waveform adjuster 28 is not limited as long as the operation is performed so that the sound in one sound frame is close to silence. For example, a method of outputting the value obtained by dividing the input converted original signal S by the power value of the frame as the adjustment signal AS can be applied. Further, for example, a method may be used in which a value between the maximum value and the minimum value of the waveform in the previous frame is randomly output to obtain an adjustment waveform. Furthermore, the audio level of the adjustment signal AS to be output may be adjusted as necessary.

  The frequency shifter 21 receives the adjustment signal AS from the waveform adjuster 28, performs frequency shift by the same method as described in the first embodiment, and outputs the result to the component extractor 24 as the shift signal SS. .

  The component extractor 24 extracts a predetermined low band in the shift signal SS from the frequency shifter 21 and outputs it to the adder 90 as a combined low band signal LLS in the same manner as in the first embodiment.

  Even in the voice band extending apparatus of the second embodiment, when generating a band extension signal that is an extension of the band from the original signal, an extension signal component is generated as a band signal for a low frequency. , You can listen to the sense of spread of the entire low frequency, and can eliminate the lack of low frequency that was heard when adding a specific frequency component, resulting in improved sound quality of the output signal Can be made.

  Further, according to the second embodiment, a waveform adjuster is provided instead of the switch of the first embodiment, so that the processing configuration corresponding to the validity / invalidity of the signal can be integrated into one system. Reduction of processing complexity and reduction of processing amount can be expected.

(C) Third Embodiment Next, a third embodiment in which the band extending apparatus and the insufficient band signal generator according to the present invention are applied to a voice band extending apparatus will be described with reference to the drawings.

  The overall configuration of the voice band extending apparatus according to the third embodiment can also be represented in FIG. 1 according to the first embodiment.

  The third embodiment is different from the first embodiment in the internal configuration of the low-band signal generator (reference numeral 40 is assigned to the third embodiment), and the others. Is the same as in the first embodiment.

  FIG. 6 is a block diagram showing an internal configuration of the low-band signal generator 40 according to the third embodiment, which is the same as and corresponding to FIG. 3 according to the first embodiment and FIG. 5 according to the second embodiment. Parts are shown with the same reference numerals. In FIG. 6, the low-band signal generator 40 of the third embodiment includes a signal determiner 22, a frequency shifter 21, a component extractor 24, a waveform adjuster 33, an autocorrelation calculator 35, an output waveform storage 36, and A waveform memory 37 is provided.

  Hereinafter, while explaining the operation of the low-band signal generator 40 of the third embodiment, the function of each part will be clarified.

  In FIG. 6, the signal determiner 22 determines whether the converted original signal S is valid (silent) or invalid (sound) in the same manner as in the first embodiment, and the signal adjuster 33 receives the signal determination information SL. To give.

  In the low-band signal generator 40 of the third embodiment, the frequency shifter 21 is provided before the waveform adjuster 33 as shown in FIG. Although the position is different, the frequency shifter 21 of the third embodiment receives the input conversion original signal S and performs frequency shift by the same method as described in the first embodiment. The frequency shifter 21 outputs the frequency shift result to the waveform adjuster 33 as the shift signal SS.

  As in the case of the second embodiment, the waveform adjuster 33 basically processes the input transition signal SS when the signal determination information SL indicates validity (in the case of silence). If the signal determination information SL indicates invalidity (in the case of sound), the waveform adjustment is performed on the input transition signal SS, and after the waveform adjustment Is output as the adjustment signal AS.

  In the case of the third embodiment, as will be described later, the method of generating the adjustment signal AS in the case of sound is different from that of the second embodiment.

  The output waveform memory 36 stores the adjustment signal AS output from the waveform adjuster 33, and updates the stored content to the latest signal for each voice frame. The amount of data stored in the output waveform memory 36 is an amount necessary for calculating an autocorrelation function by an autocorrelation calculator 35 described later, and is necessary for use by the waveform adjuster 33 for the adjustment signal AS. For example, the amount of data is 50 ms (however, the time length is not limited to this).

  Hereinafter, a method for generating the adjustment signal AS when the signal determination information SL indicates invalidity (when there is sound) will be described.

  If it is determined that there is sound, the waveform adjuster 33 outputs an autocorrelation calculation request PR to the autocorrelation calculator 35. The autocorrelation calculator 35 calculates the period at the time by calculating the autocorrelation function, and outputs the period obtained by the calculation to the waveform adjuster 33 as the period data SP.

  In order to calculate the autocorrelation function, the autocorrelation calculator 35 first outputs a waveform update request DR to the waveform memory 37. When the waveform update request DR is input to the waveform memory 37, the waveform memory 37 copies the output waveform data SD stored in the output waveform memory 36 to itself. After copying the output waveform data SD from the output waveform memory 36, the waveform memory 37 stores the output waveform data until the next waveform update request DR is input, and the waveform data SD is used as the waveform data HD. Output to the autocorrelation calculator 35. The amount of the waveform data only needs to be sufficient to calculate the autocorrelation function, and is, for example, a data amount of 30 ms (however, it is not limited to this time length). Receiving the waveform data HD, the autocorrelation calculator 35 calculates the maximum delay amount of the autocorrelation function using the waveform data HD, and outputs this delay amount to the waveform adjuster 33 as the period data SP.

  The magnitude of the delay amount represented by the periodic data SP can be limited to a value in the range of, for example, 5 ms to 15 ms, but it is needless to say that the range that the delay amount can take is not limited to the above range. The waveform data HD used for calculating the autocorrelation (delay amount) is a silent part, and there may be no period in the audio component. In this third embodiment, the delay having the maximum autocorrelation function is used. The amount is used as the standard processing unit for output speech. In the description of the third embodiment, the delay amount that maximizes the autocorrelation function is expressed as a period. Further, if the period of the waveform data HD can be calculated, another method may be used without calculating the autocorrelation function.

  The waveform adjuster 33 that has received the periodic data SP takes out the necessary waveform data ND determined by the periodic data SP from the waveform storage 37, generates a signal by the adjustment signal generation method described later for each audio frame, and uses it as the adjustment signal AS. Output. The generation of the adjustment signal AS is continued for, for example, 6 sound frames. If the sound remains after the 6 sound frames have passed, the process when the sound is determined as described above is executed again, and silence is generated. A series of processing is repeated until it is determined that

  An example of the adjustment signal generation method in the waveform adjuster 33 will be described with reference to FIG.

  7 represents the waveform data SD (= ND) stored in the waveform memory 37, and the signal AS in FIG. 7 represents the adjustment signal AS output from the waveform adjuster 33. FIG. 7 shows a state in which the adjustment signals AS1, AS2,... Are output in order for each audio frame from the state where the sound is changed from silence to sound. The period T represents a period obtained from the period data SP output from the autocorrelation calculator 35.

  When the period T is determined, the adjustment signal AS is generated using the latest three periods of the waveform data SD. (0) in FIG. 7 represents a section used for the adjustment signal, and is equal to the latest three periods described above. 7 (1), (2), and (3) show the passage of time.

  The case where the adjustment signal AS1 is output will be described from the case of FIG. The adjustment signal AS1 is generated using the latest one period section Ta. The adjustment signal AS1 is generated by using only the period T from the oldest side to the newest side of one period section Ta. As shown in FIG. 7, when the entire period of one period section Ta is used, but less than one voice frame, it is output again from the oldest side of the period section Ta so that only one voice frame is generated in total. To do. That is, the section used for generating the adjustment waveform AS1 is the section of S11 and S12, and corresponds to the section from B1 to E1. At this time, it is preferable to implement a technique for continuously transitioning between the sections S11 and S12. For example, in the section S12, an oldest 1/4 cycle portion from the latest one cycle is secured, and the latest quarter cycle portion of the section S11 is added so as to continuously transition from the section S11 to the section S12. You may take the method of. Similar processing may be performed between SD and AS1, and processing after AS2.

  When the adjustment signal AS2 is output, the adjustment signal AS2 is generated by using one of the latest two period intervals after increasing one period. That is, the adjustment signal AS2 is generated using a section of Tb (= T1 + T2). The section used for generation starts output from the position B2 which is shifted by the section T from the last position E1 used for the output of the adjustment signal AS1, but the position E1 is not within the oldest one cycle T of the section Tb. In this case, the output is moved to the earliest side by the period T until it is within the one period T (in the case of FIG. 7 (2), the movement is not performed) and the output is started. Therefore, the interval from B2 to E2 is used to generate the adjustment signal AS2.

  When the adjustment signal AS3 is output, the adjustment signal AS3 is output using a period of three period Tc (= T1 + T2 + T3) increased by one period as in the case of the adjustment signal AS2. The method of extracting data from the section Tc is the same as in the case of the adjustment signal AS2. Therefore, the interval from B3 to E3 is used for generating the adjustment signal AS3.

  After the adjustment signal AS4, the interval used for generation is not expanded, but the interval Tc set by the adjustment signal AS3 is used for generation. The position used for output starts from the position used for the previous generation. That is, in the case of AS4, output is started from the position E3.

  As a result of the processing as described above, the adjustment signal AS from the waveform adjuster 33 changes the arrangement of the data SD while maintaining the periodicity of the period T in the waveform data SD (= ND) stored in the waveform storage 37. The period T is different and converted in units.

  The component extractor 24 extracts a predetermined low band in the adjustment signal AS from the waveform adjuster 33 in the same manner as in the first and second embodiments, and outputs it to the adder 90 as a combined low band signal LLS. Output.

  Also in the audio band extending apparatus of the third embodiment, when generating a band extension signal that is an extension of the band from the original signal, an extension signal component is generated as a band signal for a low frequency. , You can listen to the sense of spread of the entire low frequency, and can eliminate the lack of low frequency that was heard when adding a specific frequency component, resulting in improved sound quality of the output signal Can be made.

  Further, according to the third embodiment, it is possible to reduce the sound property in the low-band signal by using the immediately preceding non-sonic wave shape.

(D) Other Embodiments In the above embodiments, the low-band signal generator 12 and the low-band signal generators 20, 30, and 40 each generate a composite signal. The generator may be configured to exhibit the functions of the devices 20, 30, 40 and the function of the low-frequency signal generator 12. For example, the synthesized low-frequency signal LS and the synthesized low-band signal LLS may be added inside this generator and output to the adder 90 as a synthesized signal of the low-frequency part.

  Further, in each of the above embodiments, the one having both the low-band signal generator and the low-band signal generator is shown, but the present invention only needs to include at least the low-band signal generator. Further, depending on the input signal DC, a high frequency signal generator or a silent part signal generator may be omitted.

  That is, in each embodiment, an example in which four of the synthesized low-frequency signal LS, the synthesized high-frequency signal HS, the synthesized silent signal US, and the synthesized low-band signal LLS are generated and added to the converted original signal S has been described. The number of signals generated for addition is not limited to four as long as the combined low-band signal LLS is included, and may be more or less than this.

  In the second embodiment, the waveform adjuster and the frequency shifter are arranged in this order. However, as in the third embodiment, this processing order may be reversed. In the third embodiment, the frequency shifter and the waveform adjuster are arranged in this order. However, as in the second embodiment, the processing order may be reversed.

  In each of the above-described embodiments, it has been described that the low band to be expanded in consideration of the telephone public network is outside the telephone band. However, a part of the low band signal generated by the low band signal generator is a telephone band. It may be within the range of the band. Of course, the device on which the bandwidth expansion device of the present invention is mounted is not limited to a device related to communication via a general public network.

  In each of the above embodiments, the description has been made on the premise of the audio signal, but the present invention can also be applied to other periodic signals such as an image signal. Even for an image signal, it is possible to determine whether the frequency shift is valid (corresponding to silence) or invalid (corresponding to sound) based on power or the like.

  Furthermore, in the description of each of the above embodiments, the configuration has been described as an image implemented in hardware, but all or part of the configuration of the present invention may be implemented in software.

  In each of the above-described embodiments, the band expansion method using frequency shift is applied to the low frequency side. However, the band expansion method may be used for expansion on the high frequency side. For example, the high frequency signal generator 13 may apply a band expansion method using frequency shift.

It is a block diagram which shows the whole structure of the audio | voice band expansion apparatus of 1st Embodiment. It is a block diagram which shows the whole structure of the conventional audio | voice band expansion apparatus. It is a block diagram which shows the detailed structure of the low-band signal generator of 1st Embodiment. It is a block diagram which shows the detailed structure of the frequency shifter of 1st Embodiment. It is a block diagram which shows the detailed structure of the low-band signal generator of 2nd Embodiment. It is a block diagram which shows the detailed structure of the low-band signal generator of 3rd Embodiment. It is explanatory drawing used for operation | movement description of the low-band signal generator of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Sampling frequency converter, 12 ... Low-pass signal generator, 13 ... High-pass signal generator, 14 ... Unvoiced signal generator, 20, 30, 40 ... Low-band signal generator, 21 ... Frequency shifter, 22 ... Signal decision unit, 23 ... Waveform converter, 24 ... Component extractor, 25 ... Switcher, 28 ... Waveform adjuster, 33 ... Waveform adjuster, 35 ... Autocorrelation calculator, 36 ... Output waveform memory, 37 ... Waveform memory, 90... Adder, 100.

Claims (7)

An insufficient band signal generator for generating a signal component of the limited and insufficient band from an input signal whose frequency band is limited to a low band or a high band,
A frequency shift means for shifting the frequency component of the input signal to the shortage band side by a specific frequency;
A deficient band signal generator comprising: component extracting means for extracting a deficient band range component from the output signal of the frequency shifter and outputting the deficient band signal. Signal determination means for determining validity or invalidity of the input signal;
An alternative output signal forming means including the component extraction means as a component of the output stage for forming an alternative output signal to be output by replacing the insufficient band signal when the input signal is invalid,
2. The deficient band signal generator according to claim 1, wherein when the input signal is valid, a deficient band signal generated by the processing of the frequency shift unit and the component extracting unit is output.   3. The deficient band signal generator according to claim 2, wherein the substitute output signal forming means forms a substitute output signal by weakening a waveform shape of the input signal.   The alternative output signal forming means includes an output waveform memory for storing the alternative output signal or the insufficient band signal before passing through the component extraction means for a predetermined period, and is stored in the output waveform memory. 3. The deficiency according to claim 2, wherein a signal whose temporal arrangement is changed while the periodicity of the signal is maintained is formed as a new alternative output signal before passing through the component extraction means. Band signal generator.   5. The deficient band signal generator according to claim 2, wherein the signal determination unit determines whether the input signal is valid or invalid by comparing the power of the input signal with a threshold value. 6.   6. The insufficient band signal generator according to claim 1, wherein the input signal is an audio signal. The insufficient band signal generator according to any one of claims 1 to 6, wherein a signal component of the limited and insufficient band is generated from an input signal whose frequency band is limited to a low band or a high band,
A band extending apparatus comprising: an adding means for adding the insufficient band signal output from the insufficient band signal generator and the input signal.

Images