JPH10143197A - Reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the equalizer function which adjusts tone quality with a smaller amount of computations against the coded signals that are band divided. SOLUTION: When a coded bit stream equivalent to MPEG is inputted to a separating device 21, the device 21 separates the bit stream into quantized signals for every band and scale factor indexes (scfid). Then, in order for a listener to control the tone quality, the listener sets the amplification factors of the amplitudes for every band in a setting device 22. Scfid updating devices 23a to 23n increase or decrease the indexes in accordance with the amplification factors set for the amplitudes of every band. Then, the updated indexes scfid are converted into scale factors by scf inverse quantization devices 25a to 25n. Then, decoding devices 24a to 24n multiply the scale factors to the quanitzed signals outputted from the device 21 and decode the audio data for every band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for converting a band-divided speech coded signal into a speech signal having a desired sound quality by controlling a scale factor of the speech signal and performing band synthesis.

[0002]

2. Description of the Related Art As a coding method for compressing a band of an audio signal, audio band division encoding has been well known.
For example, there is a sub-band coding method as a coding method for compressing and coding each band signal after dividing an audio signal into bands, and the MPEG1 audio coding method corresponds to this (see ISO / IEC 11172-3: 1993).

[0003] When reproducing the audio signal encoded in this way, the frequency characteristic is set especially for the reproduced signal,
There is a demand for a playback device capable of adjusting the sound quality desired by the user. Therefore, in recent years, a reproducing apparatus has been developed in which a gain circuit that adjusts the amplitude level of each band signal that has been dequantized is provided for each band, and the audio frequency of each band is corrected. For example, there are a technique described in JP-A-5-135498 and a technique described in JP-A-6-348295. Among such techniques, a reproducing apparatus in the case of an MPEG1 audio encoded signal has a configuration roughly shown in FIG.

[0004] As shown in FIG. 10, first, an audio coded signal of the MPEG1 standard is used as an audio bit stream, and this bit stream is input to a separating device 71. The separating device 71 analyzes the bit stream, decomposes the bit stream into coded data for each frequency divided into 32 subbands, and sends the data to the decoding devices 73a to 73n and the scale factor (scf) inverse quantization devices 72a to 72n. Give each one.
Then, of the encoded data for each frequency band, first, the scale factor index is inversely quantized for each band by the scale factor inverse quantization devices 72a to 72n,
Decoding devices 73a-73 using the scale factors
At n, each band signal is decoded.

The setting device 74 sets the amplification factor of each band signal to control the amplitude for each band, and supplies the data to the band signal gain adjusting devices 75a to 75n. Then, according to the change of the amplification factor, the band signal gain adjusting devices 75a to 75n adjust the level of the amplitude of each of the band signals dequantized. Thereafter, each band signal whose gain has been adjusted is input to the band synthesizing device 76 and band-synthesized. Thus, the PCM audio signal whose frequency characteristic has been corrected is output.

[0006]

However, in the reproducing apparatus having such a configuration, as long as the gain is set by the setting device 74, the gain adjustment must be continuously performed for each band. For this reason, it is impossible to avoid an increase in the amount of processing operation and an increase in the circuit scale, which has been a factor of cost increase. In particular, in recent years, system playback devices have been developed on the premise of simultaneous playback of a plurality of media, such as images, instead of audio alone, and increasing the load on the amount of processing operations may be a fatal defect for the devices. There was no problem.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been dequantized by changing the amplification factor of each band signal by controlling the scale factor of each band signal. It is an object of the present invention to provide an audio signal reproducing apparatus capable of reducing the amount of arithmetic processing and the circuit size as compared with the conventional method of adjusting the gain of each band signal.

[0008]

In order to solve such a problem, the invention according to claim 1 of the present application divides a signal into bands and then quantizes and frames each band signal for each predetermined number of samples. Perform a scale factor that is a representative value of the amplitude of each band signal for each frame, input a coded bit stream generated by multiplexing the quantized signal and the scale factor, A reproducing apparatus for reproducing a synthesized signal, comprising: a separating unit configured to extract the quantized signal and the scale factor for each band from the encoded bit stream; and amplifying an amplitude of the quantized signal for each band. Setting means for setting a rate, and a scale factor for changing a value of the scale factor separated by the separating means according to the amplification factor for each band set by the setting means. Decoding means for multiplying the quantized signal extracted by the separating means by the scale factor changed by the scale factor changing means to decode each band signal, and decoding by the decoding means. And a band synthesizing unit for reproducing a signal whose frequency has been corrected with respect to the original signal by band-synthesizing each of the converted band signals.

The invention according to claim 2 of the present application divides the signal into bands and then performs quantization and framing of each band signal for each predetermined number of samples, and represents the amplitude of each band signal for each frame. Generate a scale factor that is a value, input a coded bit stream generated by multiplexing the quantized signal and a scale factor index that symbolizes the value of the scale factor, and input a band-synthesized signal. A reproducing apparatus for reproducing, comprising: a separating unit that extracts the quantized signal and the scale factor index for each band from the encoded bit stream; and sets an amplification factor of an amplitude of the quantized signal for each band. Setting means, and a value of a scale factor index separated by the separating means according to an amplification factor for each band set by the setting means. A scale factor index changing means for changing, a scale factor dequantizing means for converting a scale factor index output from the scale factor index changing means into a scale factor, and a scale factor dequantizing means for the quantized signal extracted by the separating means. Decoding means for multiplying the scale factor output from the scale factor dequantizer and decoding each band signal, and band-synthesizing each band signal decoded by the decoding means to the original signal by band synthesis And a band synthesizing means for reproducing a signal whose frequency has been corrected.

According to a third aspect of the present invention, there is provided a scale factor level interpolating means for further subdividing a minimum unit of the scale factor between the scale factor changing means and the decoding means, When the change of the amplification factor of the amplitude for each band is instructed by the means, the scale factor changing means changes the scale factor stepwise from the value before the change to the value after the change by the minimum unit amount, The scale factor level interpolating means further subdivides and changes the minimum unit amount of the scale factor by a predetermined step width, and controls the step width so that the change of the scale factor of all bands is completed in the same time. It is a feature.

The invention according to claim 4 of the present application is characterized in that a scale factor level interpolating means for further subdividing the minimum unit of the index is provided between the scale factor dequantizing means and the decoding means, When the setting means instructs to change the amplification factor of the amplitude for each band, the scale factor index changing means changes the scale factor index stepwise from the value before the change to the value after the change in the minimum unit amount. The scale factor level interpolating means further subdivides and changes the minimum unit amount of the scale factor by a predetermined step width, and controls the step width so that the change of the scale factor of all bands is completed in the same time. It is characterized by doing.

In the invention according to claim 5 of the present application, when the resolution of the scale factor level interpolation is N, the scale factor level interpolation means calculates a level change corresponding to a change value of the minimum unit amount of the scale factor. An interpolation level setting table for dividing into N equal parts, and a table interpolating means for multiplying an interpolation level value indicated by the interpolation level setting table by a scale factor output from the scale factor changing means are provided.

In the invention according to claim 6 of the present application, when the resolution of the scale factor level interpolation is N, the scale factor level interpolation means calculates a level change corresponding to a change value of the minimum unit amount of the scale factor. An interpolation level setting table for dividing into N equal parts, and a table interpolation means for multiplying the scale factor output from the scale factor inverse quantization means by the interpolation level value indicated in the interpolation level setting table. is there.

The invention according to claim 7 of the present application is characterized in that T is the change time of the amplification factor of each band signal, N is the scale factor level interpolation resolution, STP is the number of scale factor level interpolations per unit time, and STP is When the scale factor index change value of the signal is DS, the scale factor level interpolation means adjusts the step width so that the table step width SKP per level interpolation becomes SKP = N * DS / (STP * T). The present invention is characterized in that it has a step width adjusting means for performing the step width adjustment.

[0015] In the invention according to claim 8 of the present application, the setting means sets the amplification factor of the amplitude of the quantized signal for each band of the bit stream, and sets the amplitude of a specific bandwidth not limited to each bandwidth. Filter means for changing the frequency characteristic of the specific band set by the setting means, for the decoded signal of the band decoded by the decoding means, It is characterized by being provided between a decoding means and the band synthesizing means.

Further, in the invention according to claim 9 of the present application, the setting means sets the psychological amount to the amplification factor of each band so that the listener can set the amplification factor of each band by the psychological amount of sound. It is characterized by having parameter conversion means for conversion.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A reproducing apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a basic configuration of the playback device of the present embodiment. In this figure, a separating device 11 receives audio coded data and converts the bit stream into a bandwidth 500
This is a device that separates a quantized signal of 32 bands (subbands) of Hz into a scale factor.

Here, the first band is 0-500 Hz, the second band is 500 Hz-1 kHz, and the third band is 1 kHz-1.
5 kHz, 50 from 15.5 kHz to 16 kHz
It is divided by equal bandwidth into 32 bands at 0 Hz intervals.

For example, the structure of audio data of the MPEG standard is composed of data of a plurality of frames in units of a frame called AAU. The frame data includes a header, error check bits, actual audio data, and ancillary data. In the audio data area, an allocation, a scale factor, and a sample (encoded audio quantized data) are inserted. The allocation, the scale factor, and the sample are all arranged in the order of the number of the 32 subbands, and the number of bits of the sample data used for each subband is specified by the allocation.

The data of 12 samples in one sub-band is separated into waveform data and magnification data by an encoding device (not shown), and the waveform data has a maximum amplitude of 1.0.
Is normalized to be The scaling factor for converting the normalized amplitude into the actual amplitude on the decoding device side is called a scale factor, and is from +6 dB to -118 dB.
Up to B can be specified in about 2 dB units. For this reason, 6 bits are assigned to the scale factor of each subband.

The scale factor (scf) changing device 13a shown in FIG.
Input the scale factor of z) and set the value
This is a device that changes based on the set value of 2. Similarly, the scale factor changing device 13b is a device that inputs the scale factor of the second band (500 to 1000 Hz) from the separating device 11 and changes the value based on the set value of the setting device 12. Thus, the scale factor changing devices 13a to 13n are provided for the first to 32nd bands, respectively.

The setting device 12 is a device for setting the amplification factor of the amplitude for each of the 32 bands, and the amplification factor of each band is given to each of the scale factor changing devices 13a to 13n. The amplification factor is set by changing the physical quantity of the sound by manual operation like the amplification factor of each sub-band, or is input by the psychological quantity of the sound like power or clarity.

The quantized signals separated for each band by the separation device 11 are supplied to decoding devices 14a to 14n, respectively.
The decoding device 14a converts the quantized signal of the first band into a normalized signal using a built-in table, multiplies the normalized signal by the scale factor output from the scale factor changing device 13a, and This is to generate an audio signal. Similarly, the decoding devices 14b to 14n respectively convert the quantized signals of the second to 32nd bands into normalized signals using a built-in table, and convert the scale factors output from the scale factor changing devices 13b to 13n. The normalized signal is multiplied to generate an audio signal in the second to 32nd bands.

The band synthesizing device 15 is a device for outputting a PCM audio signal by band synthesizing each of the decoded band signals.

The operation of the reproducing apparatus thus configured according to the first embodiment will be described. First, the user of the playback device performs sound quality adjustment using the setting device 12 in FIG. 1 in order to obtain a desired sound quality. For example, if the user wants to emphasize the low-frequency part of the reproduced signal, the first band (0 to 500H)
The amplification factor of z) may be set high, and if it is desired to emphasize the high frequency region, the amplification factor of the 17th band or higher (8 kHz or higher) may be set high. Here, as an example, it is assumed that the user has set the amplification factor of the first band higher by 6 dB in order to emphasize the low band.

The separating apparatus 11 converts the input audio coded data into 32 band-divided quantized signals and 32
And a scale factor of. Next, the scale factor changing device 13a increases the value of the scale factor of the first band by 6 dB according to the value of the amplification factor of the first band set by the setting device 12.

Other scale factor changing devices 13b-1
In 3n, since there is no instruction of the amplification factor of the corresponding band signal, the input scale factor is output as it is. In the decoding devices 14a to 14n, the separating device 11
, The quantized signal of each band output from is converted to a normalized signal by inverse quantization, and each band signal is generated by multiplying the normalized signal by each scale factor. The band synthesizing device 15 inputs the respective band signals and performs band synthesis,
Outputs PCM audio signal.

As described above, according to the reproducing apparatus of the present embodiment, an equalizer function can be realized only by adding the setting device 12 and the scale factor changing device 13 for each band.
In addition, changing the amplification factor of each band only requires changing the scale factor of each band. Therefore, compared to the case of amplifying the dequantized data of each band, the increase in the amount of calculation due to the addition of the function is very small.

In the present embodiment, the gain is set or changed in a one-to-one manner for all 32 bands. Is also good. Depending on the band, a plurality of bands may be set by one operation.

(Embodiment 2) A reproducing apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing a basic configuration of the playback device of the present embodiment. In the figure, a separation device 21 is a device that inputs audio encoded data and separates from a bit stream into a quantized signal for 32 bands with a bandwidth of 500 Hz and a scale factor index.

Here, the scale factor index (s
cfid) is a value in which each scale factor value is associated with an index number, and is used when transmitting from an encoding device (not shown) to a reproducing device. FIG. 3 is a table showing the correspondence between 63 scale factor values and index numbers 0 to 62. Here, the index number 3 is a scale factor 1.000..., And the values of 63 scale factors that change in 2 dB steps are displayed.

The scale factor index (s
The cfid) changing device 23a is a device that inputs the scale factor index of the first band (0 to 500 Hz) from the separating device 21 and changes the value according to the set value of the setting device 22. Similarly, the scale factor index changing device 23b sends the second band (500 to 1) from the separation device 21.
000 Hz), and changes the value in accordance with the set value of the setting device 22. As described above, the scale factor index changing devices 23a to 23n are provided for the first to 32nd bands, respectively.

The setting device 22 is a device for setting the amplification factor of the amplitude for each of the 32 bands, and the amplification factor of each band is determined by each of the scale factor index changing devices 23a to 23n.
Given to. The amplification factor is set in the same manner as in the first embodiment.

Scale factor index changing device 2
The outputs of 3a to 23n are scale factors (sc
f) It is given to the inverse quantization devices 25a to 25n. The scale factor inverse quantization device 25 is a device that converts the index numbers shown in FIG. 3 into scale factors.

The quantized signals separated for each band by the separation device 21 are supplied to decoding devices 24a to 24n, respectively.
The decoding device 24a converts the quantized signal of the first band into a normalized signal using a built-in table, and multiplies the normalized signal by the scale factor output from the scale factor inverse quantization device 25a. . Similarly, the decoding devices 24b to 24n respectively convert the quantized signals of the second to 32nd bands into normalized signals using a built-in table, and scale factor inverse quantizers 25b to 25n.
Is a device for multiplying the normalized signal by the scale factor output from the.

The band synthesizing device 26 is a device for outputting a PCM audio signal by band-synthesizing each of the decoded band signals.

In the present embodiment, the setting device 22 changes the value of the scale factor index by 1 each time the setting of the amplification factor of each band signal changes by 2 dB. It is assumed that the setting is made to change by 2 dB in the inverse quantization of the factor.

The operation of the reproducing apparatus thus configured according to the second embodiment will be described. First, the user of the playback device performs sound quality adjustment using the setting device 22 to obtain a desired sound quality. For example, if the user wants to emphasize the low-frequency portion of the reproduced signal, the amplification factor of the first band (0 to 500 Hz) should be set high. If the user wants to emphasize the high-frequency portion, the gain should be higher than the 17th band (8 kHz). Above) may be set high. Here, as an example, it is assumed that the user has set the amplification factor of the first band higher by 6 dB in order to emphasize the low band.

On the other hand, the separating device 21 decomposes the input audio coded data into 32 band-divided quantized signals and 32 scale factor indexes. Next, the scale factor index changing device 23a
Then, the value of the scale factor index of the first band is increased by 3 in accordance with the instruction of the amplification factor of the first band set by the setting device 22.

Scale factor index changing device 2
In 3b to 23n, since there is no instruction of the amplification factor of the band signal corresponding to each, the scale signals are output as they are without changing each scale factor index. The scale factor dequantizers 25a to 25n dequantize the input scale factor index of each band and output the scale factor.

The decoding devices 24a to 24n inversely quantize the quantized signals output from the demultiplexing device 21 and convert the quantized signals into normalized signals. Generate a signal. Band synthesis device 2
6 inputs the respective band signals, synthesizes the band, and performs PCM.
Output the audio signal.

As described above, in this embodiment, the setting device 2
The equalizer function can be realized only by adding the scale factor index changing device 23 for each band 2 and each band. Moreover, since only the scale factor index of each band is changed to change the amplification factor of each band, the increase in the amount of calculation due to the addition of the function is very small as compared with the case of amplifying the dequantized signal of each band.

In this embodiment, the amplification ratio is changed one-to-one for all 32 bands. However, the gain may be limited to a band having a large auditory effect. Depending on the band, a plurality of bands may be set by one operation.

(Embodiment 3) A reproducing apparatus according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing a basic configuration of the playback device of the present embodiment. In the figure, a separation device 31 is a device that inputs audio encoded data and separates from the bit stream into a quantized signal for 32 bands with a bandwidth of 500 Hz and a scale factor index.

The scale factor index (scfi)
d) The change device 33a receives the first band (0 to 0) from the separation device 31.
This device inputs a scale factor index of 500 Hz) and changes the value of the index by one according to the set value of the setting device 32. Similarly, the scale factor index changing device 33b receives the scale factor index of the second band (500 to 1000 Hz) from the separating device 31, and changes the value of the index by one according to the set value of the setting device 32. It is. Thus, the scale factor index changing devices 33a to 33n are provided for the first to thirty-second bands, respectively.

The setting device 32 is a device for setting the amplification factor of the amplitude for each of the 32 bands, and the amplification factor of each band is determined by each of the scale factor index changing devices 33a to 33n.
Given to. The setting of the amplification factor is performed in the same manner as in the second embodiment. However, when the set value is changed, a switching signal is output from the setting device 32 to the scale factor level interpolation devices 36a to 36n described later. I do.

Scale factor index changing device 3
The outputs of 3a to 33n are scale factors (sc
f) It is given to the inverse quantization devices 35a to 35n. The scale factor inverse quantization device 35 is a device for converting an index number into a scale factor.

Scale factor inverse quantization devices 35a-3
The scale factors converted by 5n are output to scale factor level (scf) interpolators 36a to 36n, respectively. When the amplification factor of each band is changed by the setting device 32, the scale factor level interpolating device 36 changes the scale factor before the change dequantized by the scale factor dequantizing device 35 from the changed scale factor for a certain period of time. Is controlled so as to be able to be switched in finer steps. The scale factor level interpolating device 36 has a switching circuit (not shown). In a normal state, this switching circuit is connected to the decoding device 34, and the scale factor given from the scale factor dequantizing device 35 is used as it is in the decoding device 34. Output to On the other hand, when the scale factor is switched, the switching circuit is connected to the internal interpolation circuit based on the switching signal output from the setting device 32. Thus, the scale factor level interpolation device 36 repeatedly performs the scale factor level interpolation for the same time T for any band every time the scale factor index of the scale factor index changing device 33 is updated.

FIG. 5 shows a scale factor level interpolation device 3.
FIG. 6 is a configuration diagram showing details of a sixth example. As shown in the figure, the scale factor level interpolation device 36 includes an interpolation level setting table 38, a table interpolation means 39, a table skip adjustment means 40, a table pointer 41, and a switching circuit (not shown).

The interpolation level setting table 38 is a table for setting an interpolation level corresponding to one change of the scale factor index, in which level interpolation values of N stages at equal intervals on a logarithmic scale are registered.

The table interpolation means 39 is means for multiplying the scale factor by the scale factor level interpolation value (adding in dB) and performing the scale factor level interpolation. The scale factor level interpolation value is stored in the table pointer 41. Is indicated by the data of the interpolation level setting table 38.

FIG. 6 shows specific values of the interpolation level setting table 38 shown in FIG. Here, the index change 1 is further divided into 16 parts, and the value of one division is
It is set to 0.125 dB.

When the address of the interpolation level setting table 38 indicated by the table pointer 41 exceeds the last address of the table, the table pointer 41 is set to return to the start address of the interpolation level setting table 38.

The table skip adjusting means 40 is a means for calculating a table skip width (the number of skipped table reading steps) for each level interpolation. The change value of the scale factor index determined from the setting of the amplification factor in the setting device 32 is DS, the number of stages of the scale factor interpolation table (resolution) is N, the change time of the amplification factor of each band is T, and the number of interpolations per time T is STP. And The time T is the same for each band. The table skip adjustment unit 40 uses the table skip value SKP per level interpolation.
Is SKP = N * DS / (STP * T).

The quantized signals separated for each band by the separation device 31 are supplied to decoding devices 34a to 34n, respectively. The decoding device 34a converts the quantized signal of the first band into a normalized signal using a built-in table, and multiplies the normalized signal by the scale factor output from the scale factor level interpolation device 36a. Similarly, the decoding devices 34b to 34n respectively convert the quantized signals of the second to 32nd bands into normalized signals using a built-in table, and also perform scale factor level interpolation devices 36b to 36n.
Is multiplied by the scale factor output from.

The band synthesizing unit 37 is a device for outputting a PCM audio signal by band synthesizing each of the decoded band signals.

In the present embodiment, the setting device 32 changes the value of the scale factor index by 1 each time the setting of the amplification factor of each band signal changes by 2 dB, and when the value of the scale factor index changes by 1, It is assumed that the value is set to change by 2 dB in the inverse quantization of the scale factor.

The operation of the reproducing apparatus thus configured according to the third embodiment will be described. First, the user of the playback device performs sound quality adjustment using the setting device 32 to obtain a desired sound quality. For example, when the user wants to emphasize the low-frequency portion of the reproduction signal, the amplification factor of the first band (0 to 500 Hz) may be set to be high. When it is desired to emphasize the high frequency region, the amplification factor in the 17th band or higher (8 kHz or higher) may be set high. Here, as an example, it is assumed that the user has set the amplification factor of the first band higher by 6 dB in order to emphasize the low band.

The demultiplexer 31 converts the input audio coded data into 32 band-divided quantized signals,
And the scale factor index. Next, the scale factor index changing device 33a increases the value of the scale factor index corresponding to the first band by 3 according to the instruction of the amplification factor of the first band set by the setting device 32. Also, the scale factor inverse quantization device 35
In a to 35n, the scale factor is dequantized for each input band to generate a scale factor.

The scale factor level interpolation device 36b-
In 36n, since there is no instruction of the amplification factor of the band corresponding to each, the output is directly performed without changing the scale factor index while the built-in switching circuit is connected to the decoding device side.

Next, the scale factor level interpolation device 36
“a” does not immediately increase the scale factor index of the first band by 6 dB, but increases the amplification time of each band level by T by 2 dB every T / 3. Therefore, in the scale factor level interpolation device 36a of the first band, the skip width is calculated by the table skip adjustment means 40, and the table pointer 41 indicating the characteristic value of the interpolation level setting table 38 is shifted by the calculated skip width. Determine the level interpolation value for the scale factor. The table interpolation means 39 multiplies the scale factor by the level interpolation value of the scale factor indicated by the table pointer 41, and performs level interpolation of the scale factor.

In this embodiment, when the change value DS is set, the table skip value SK per one level interpolation is set.
P is specified by N * DS / (STP * T), and the table pointer 4 is set at regular intervals from the start of level interpolation to time T.
1 circulates through the addresses of the interpolation level setting table 38,
The change value of the scale factor index changing device 33 is incremented by one.

Each of the decoding devices 34a to 34n inversely quantizes the quantized signal of each band output from the demultiplexing device 31 to convert it into a normalized signal. Generate Band synthesis device 3
Reference numeral 7 inputs each band signal, performs band synthesis, and outputs a PCM audio signal.

As described above, in this embodiment, an equalizer function can be realized only by adding the setting device 32 and the scale factor index changing device 33 for each band.
In addition, changing the amplification factor of each band only involves changing the scale factor index of each band, so the increase in the amount of calculation due to the addition of functions is very small compared to the case of amplifying the dequantized signal of each band. .

Further, in this embodiment, since the level interpolation of the scale factor is performed, the equalizer function can be realized without generating discontinuous noise in the amplitude change of each band signal. Moreover, in this embodiment, since the scale factor level interpolation and the increase / decrease of the scale factor are performed alternately, the change range of the scale factor level interpolation itself is very small, and the circuit scale of the scale factor level interpolation device is also small. It can be realized on a very small scale.

In the present embodiment, the amplification factor is set and changed on a one-to-one basis for all 32 bands. However, the band is set to be limited to a band having a large auditory effect. Alternatively, depending on the band, a plurality of bands may be set by one operation. Further, in the present embodiment, the case of amplifying the signal of each band has been described for the sake of simplicity. However, needless to say, the case of attenuating the signal of each band can be realized by almost the same procedure. The above-described scale factor level interpolating device can be provided at a subsequent stage of the scale factor changing device 13 in the first embodiment.

(Embodiment 4) A reproducing apparatus according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing a basic configuration of the playback device of the present embodiment. In the figure, a separating device 51 is a device that inputs audio encoded data and separates from a bit stream into a quantized signal for 32 bands with a bandwidth of 500 Hz and a scale factor index.

The scale factor index (scfi
d) The change device 53a sends the first band (0 to 0) from the separation device 51.
This is a device that inputs a scale factor index (500 Hz) and changes the value according to the set value of the setting device 52. Similarly, the scale factor index changing device 53b sends the second band (500 to 100) from the separation device 51.
This is a device that inputs a scale factor of 0 Hz) and changes the value based on the set value of the setting device 52. As described above, the scale factor index changing devices 53a to 53n are provided for the first to 32nd bands, respectively.

The setting device 52 is a device for setting the amplification factors of a plurality of specific bands. In the present embodiment, the setting device 52 is 100 Hz or less, 100 to 200 Hz, 200 to 500 Hz, 500
~ 1kHz, 1k-2kHz, 2k-4Hz, 4-8k
And setting elements corresponding to eight frequency bands of 8 kHz to 16 Hz.

Of the eight setting elements in the setting device 52, the setting element of 200 Hz to 500 Hz corresponds to the change of the scale factor index of the first band, and
The setting element of z to 1 kHz is in the second band, the setting element of 1 k to 2 kHz is in the third to fourth band, the setting element of 2 k to 4 kHz is in the fifth to eighth band, and the setting element of 4 k to 8 kHz is in the ninth to 16 th bands.
The setting elements of the bands 8k to 16k correspond to the changes of the scale factor indexes of the 17th to 32nd bands, respectively. The set values at 100 Hz or less and 100 to 200 Hz set by the setting device 52 are 200 to 50 Hz.
The value is compared with the set value at 0 Hz, and the difference value is provided to a filter device 56 described later.

Next, the outputs of the scale factor index changing devices 53a to 53n are the scale factors (s
cf) given to the inverse quantization devices 55a to 55n. The scale factor inverse quantization device 55 is a device for converting an index number into a scale factor. In the scale factor index changing devices 53a to 53n,
It is assumed that the value of the scale factor index is changed by 1 each time the amplification factor of each band signal changes by 2 dB.

Scale factor inverse quantization devices 55a to 55a
The scale factors converted by 5n are output to the decoding device 54, respectively.
a to 54n. The quantized signals separated for each band by the separation device 51 are respectively decoded by the decoding devices 54a to 54a.
n. The decoding device 54a converts the quantized signal of the first band into a normalized signal using a built-in table, and multiplies the normalized signal by the scale factor output from the scale factor inverse quantization device 55a. Similarly, the decoding devices 54b to 54n respectively convert the quantized signals of the second to 32nd bands into normalized signals using a built-in table, and also perform scale factor inverse quantization devices 55b to 55n.
The normalized signal is multiplied by the scale factor output from 55n.

In the present embodiment, a filtering device 56 is provided at the subsequent stage of the decoding device 54a,
Delay devices 57b to 57n are provided at the subsequent stage of 54n. The filter device 56 is composed of, for example, a plurality of second-order IIR filters, and out of the signals of the first band output from the decoding device 54a, 100 Hz or less and 100 to 20
It corrects the frequency characteristics of the 0 Hz signal component.
The correction value is output from the setting device 52. Delay device 5
7b to 57n delay the output signals of the decoding devices 54b to 54n by the same time as the operation time of the filter device 56, respectively.

The band synthesizer 58 is a device for outputting a PCM audio signal by band-synthesizing the band signals output from the filter device 56 and the delay devices 57b to 57n.

The operation of the reproducing apparatus according to the fourth embodiment thus configured will be described. First, the user of the playback device performs sound quality adjustment using the setting device 52 to obtain a desired sound quality. Here, the user is 100H as an example.
The setting element below z is set higher by 6 dB, and 200 to 500
Hz setting element and 8 kHz to 16 kHz setting element are 2d
It is assumed that B is set higher. Then, the setting device 52 instructs the scale factor index changing device 53a of the first band to set the index to +1 so that the amplification becomes 2 dB. Also, it instructs the scale factor index changing device 53 in the 17th to 32nd bands to increase the index by +1 so that the amplification becomes 2 dB. In this case, the setting device 5
2 is 4 dB below 100 Hz for the filter device 56.
Instruct amplification and 2 dB attenuation in the 100-200 Hz band.

On the other hand, the separating device 51 separates the input encoded audio data into 32 band-divided quantized signals and 32 scale factor indexes.
Next, the scale factor index changing device 53a increases the value of the scale factor index of the first band by one in accordance with the instruction of amplification of the first band set by the setting device 52. The other scale factor index changing device 53 increases the value of the scale factor index corresponding to the 17th to 32nd bands by one.

In the scale factor index changing devices 53 for the second band to the sixteenth band, since there is no instruction to amplify the corresponding band signal, each scale factor index is output without being changed.
The scale factor inverse quantization devices 55a to 55n inversely quantize the scale factor index of each input band to generate a scale factor.

The filter device 56 performs a filtering process on the decoded data of the first band in accordance with an instruction from the setting device 52. The decoded signals in the second band to the 32nd band are output to the band synthesizer 58 after being delayed by the delay devices 57b to 57n. The band synthesizer 58 receives the band signals, performs band synthesis, and outputs a PCM audio signal.

As described above, in the present embodiment, the setting device 5
2. The equalizer function can be realized only by adding the scale factor index changing device 53 and the filter device 56 for correcting the frequency of the decoded signal of a part of the specific band. In particular, when each bandwidth is a linear scale, as seen in the audio sub-band encoding method of MPEG1 or the like, the bandwidth of the first bandwidth is perceptually wide. Here, by adding the filter device 56 to the low band, the resolution of the low band bandwidth can be increased. In addition, since a filter device is added to a part of the band as necessary, the amplification factor can be set with a bandwidth not limited to each band signal of the audio bit stream. In addition, in the band where the filter device 56 is not installed, the scale factor index of each band is only changed to change the amplification factor. Increase is negligible. Therefore, the circuit scale can be significantly reduced as compared with the case where the equalizer processing is performed by the filter device over a wide band.

Although a filter device is added only to the decoded signal of the first band in the present embodiment, a filter device may be added to any band depending on the use.

(Embodiment 5) A reproducing apparatus according to a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram showing a basic configuration of the playback device of the present embodiment. In the figure, a separating device 61 is a device that receives audio coded data and separates from a bit stream into a quantized signal of 32 bands with a bandwidth of 500 Hz and a scale factor index.

The scale factor index (scfi
d) The change device 63a sends the first band (0 to 0) from the separation device 61.
This is a device that inputs a scale factor index of 500 Hz) and changes the value based on the set value of the setting device 62. Similarly, the scale factor index changing device 63b outputs the second band (500 to 10) from the separation device 61.
(00 Hz), and changes the value based on the set value of the setting device 62. Thus, the scale factor index changing devices 63a to 63n are provided for the first to 32nd bands, respectively.

The setting device 62 is a device for setting a change value of the scale factor using a specific psychoacoustic scale. The psychoacoustic scale is a psychological quantity of sound such as sharpness and power. In the present embodiment, it is assumed that clearness can be set in three stages of-, 0, and +, and power can be set in three stages of-, 0, and +, for a total of nine combinations. Therefore, the setting device 62 has a parameter conversion unit 62a, a parameter conversion table 62b, and a change distribution unit 62c in order to convert the psychoacoustic scale into an amplification factor of a specific band.

Next, the outputs of the scale factor index changing devices 63a to 63n are the scale factors (s
cf) given to the inverse quantization devices 65a to 65n. The scale factor inverse quantization device 65 is a device for converting an index number into a scale factor. In the scale factor index changing devices 63a to 63n,
It is assumed that the value of the scale factor index is changed by 1 each time the amplification factor of each band signal changes by 2 dB.

Scale factor inverse quantization devices 65a to 65a
The scale factors converted by 5n are output to the decoding device 6 respectively.
4a to 64n. The quantized signals separated for each band by the separating device 61 are respectively decoded by the decoding devices 64a to 64a-6.
4n. The decoding device 64a converts the quantized signal of the first band into a normalized signal using a built-in table and multiplies the normalized signal by the scale factor output from the scale factor inverse quantization device 65a. Similarly, the decoding devices 64b to 64n convert the quantized signals of the second to 32nd bands into normalized signals using a built-in table, respectively, and the scale factor inverse quantization device 65b.
Multiply the normalized signal by the scale factor output from .about.65n.

As in the fourth embodiment, the decoding device 6
The filter device 66 is provided at the subsequent stage of 4a, and the delay devices 67b to 67n are provided at the subsequent stage of the decoding devices 64b to 64n. The filter device 66 includes a decoding device 64a.
It corrects the frequency characteristics of the signal components of 100 Hz or less and 100 to 200 Hz among the signals of the first band output from. The correction value is output from the setting device 62. The delay devices 67b to 67n are decoding devices 64b to 6b.
4n are respectively delayed by the same time as the operation time of the filter device 66.

The band synthesizing device 68 is a device that outputs a PCM audio signal by band synthesizing each band signal output from the filter device 66 and the delay devices 67b to 67n.

The operation of the reproducing apparatus thus configured according to the fifth embodiment will be described. First, the user of the playback device adjusts the sound quality using the setting device 62 to obtain a desired sound quality.

FIG. 9 is a table showing a specific example of the parameter conversion table 62b of the setting device 62. Setting device 6
The amplification factor of each band signal converted by the second parameter conversion unit 62a is allocated to the change values of the scale factor index change units 63a to 63n and the filter unit 66 by the change allocation unit 62c. For example, in the present embodiment, the amplification rate of 200 Hz to 500 Hz corresponds to the scale factor index changing device 63a of the first band, and 500 Hz to 1 kHz corresponds to the second band, 1 kHz to 2 kHz.
Is the third to fourth band, 2k to 4kHz is the fifth to eighth band, 4k
~ 8kHz is the 9th ~ 16th band, 8k ~ 16k is the 17th ~
32 band scale factor index changer 63
b to 63n.

The difference between the set value of the setting element of 100 Hz or less and the set value of 100 to 200 Hz from the set value at 200 to 500 Hz is calculated, and that value is given to the filter device 66. Also, the scale factor index changing device 6
In 3a to 63n, the amplification factor of each band signal is 2d
Each time B changes, the scale factor index value is set to 1
Shall be changed.

Parameter conversion means 62a of setting device 62
Uses the parameter conversion table 62b to convert a psychological measure of hearing into an amplification factor of a specific band. As shown in FIG.
Assuming that the user sets the sharpness to + and the power to-, the amplification factor of each band signal is 100 Hz or less, 10
0-200Hz, 200-500Hz, 500-1kHz
z, 1k-2kHz, 2k-4kHz, 4k-8kHz
z, each characteristic value of 8 kHz to 16 kHz is -4 dB,-
6dB, -4dB, -2dB, 0dB, 0dB, 4d
B, 4 dB, and 4 dB. Further, the change distribution means 62c determines that the amplification factors of these band signals are -4 dB for the first band, -2 dB for the second band, and 0 for the third to eighth bands.
dB, the ninth to thirty-second bands are distributed as 4 dB, and the scale factor index changing devices 63a to 63d are allocated.
3n. In addition, the change distribution means 62 c
0dB below Hz, -2dB from 100Hz to 200Hz
And given to the filter device 66.

On the other hand, the demultiplexer 61 converts the input audio coded data into a 32
And the scale factor index. The scale factor index changing devices 63a to 63n follow the instructions of the amplification factors of the respective bands set by the setting device 62,
The value of the scale factor index is -2 in the first band,
−1 in the second band, 0 in the third to eighth bands, ninth to third
Change by 2 in 2 bands.

The filter device 66 responds to the instruction from the setting device 62 with respect to the decoded signal of the first band in the range of 100 Hz to
For the 200 Hz band, an attenuation process of about -2 dB is performed. The decoded signals of the second band to the 32nd band are output to the band synthesizing device 68 after being delayed by the delay devices 67b to 67n. The band synthesizing unit 68 receives each band signal, performs band synthesis, and outputs a PCM audio signal.

As described above, in the present embodiment, in order to input a specific auditory scale, the setting device 62 including the parameter conversion means 62a, and the scale factor index changing device 63 for changing the scale factor index for each band. By simply adding the filter device 66 for correcting the frequency characteristic of the decoded signal of a part of the specific band, the adjustment of the original auditory scale can be realized by applying the equalizer processing. In addition, since a filter device is added to a part of the band as needed, the amplification factor can be set with a bandwidth not limited to each band signal of the audio bit stream. In addition, since the scale factor index of each band is only changed for the band in which no filter device is installed, the increase in the amount of calculation due to the addition of the function is negligible compared to the case of amplifying the dequantized signal of each band. Only needs to be done. The circuit scale can be significantly reduced as compared with the case where the equalizer processing is performed by the filter device over a wide band.

In the present embodiment, a filter device is added only to the decoded signal of the first band. However, depending on the application, a filter device may be added to any band.

[0096]

According to the first aspect of the present invention, there is provided a setting device for setting an amplification factor of the amplitude for each band, and a scale factor of each band according to the amplification factor of each band set by the setting device. An equalizer function can be easily added simply by adding a scale factor changing device to be changed. Moreover, since the calculation required for changing the amplification factor of each band is only the change of the scale factor, the amount of calculation is reduced as compared with the level adjustment of the decoded signal of each band.

According to the second aspect of the present invention, a setting device for setting the amplification factor of the amplitude for each band, and each band scale factor index is changed according to the amplification factor of each band set by the setting device. An equalizer function can be easily added simply by adding a scale factor index changing device. Moreover, since the operation required to change the amplification factor of each band is only the change of the scale factor index, the amount of calculation is reduced as compared with the level adjustment of the decoded signal of each band.

According to the third and fourth aspects of the present invention, in addition to the above-described effects, a scale factor level interpolation function is provided, so that the amplification factor can be changed without generating discontinuous noise.

According to the fifth and sixth aspects of the invention, the scale factor level interpolation is repeated every time the scale factor or the scale factor index is updated. For this reason, the circuit configuration is simplified by the extent that the range of the scale factor level interpolation is reduced. Further, since the interpolation level setting table is used, the calculation of the interpolation level value becomes unnecessary, and the amount of calculation is reduced accordingly.

According to the seventh aspect of the invention, by providing the step width adjusting means, the scale factor level interpolation can be performed in a fixed time. In addition, the change time of the amplification factor of each band can be made uniform. Furthermore, if the change time and the change start time can be set for each band, any auditory effect can be intentionally achieved.

According to the eighth aspect of the present invention, by adding a filter device to a part of the signal of a specific bandwidth,
The frequency characteristic can be adjusted with a bandwidth that is not limited to the bandwidth of the audio bit stream. In particular, when each bandwidth is a linear scale, the bandwidth of the auditory low band is widened. Therefore, by adding a filter device to the low band, the bandwidth resolution can be further increased. Moreover, the amount of calculation and the circuit configuration can be reduced as compared with the case where a filter device is added over the entire band.

According to the ninth aspect of the present invention, in order to set a specific auditory scale, it is possible to change the sound quality on an original auditory scale by applying an equalizer process by adding parameter conversion means.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a playback device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a playback device according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a scale factor index and a scale factor.

FIG. 4 is a block diagram illustrating a configuration of a playback device according to a third embodiment of the present invention.

FIG. 5 is a detailed diagram of a scale factor level interpolation device according to a third embodiment.

FIG. 6 is a diagram showing specific values of an interpolation level setting table.

FIG. 7 is a block diagram illustrating a configuration of a playback device according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of a playback device according to a fifth embodiment of the present invention.

FIG. 9 is a diagram illustrating a specific example of a parameter conversion table according to the fifth embodiment.

FIG. 10 is a block diagram illustrating a configuration example of a conventional playback device.

[Explanation of symbols]

11, 21, 31, 51, 61 Separating device 12, 22, 32, 52, 62 Setting device 13a to 13n Scale factor changing device 23a to 23n, 33a to 33n, 53a to 53n, 6
3a to 63n Scale factor index changing device 14a to 14n, 24a to 24n, 34a to 34n, 5
4a to 54n, 64a to 64n Decoding device 15, 26, 37, 58, 68 Band synthesis device 25a to 25n, 35a to 35n, 55a to 55n, 6
5a to 65n Scale factor inverse quantizer 36a to 36n Scale factor level interpolator 38 Interpolation level setting table 39 Table interpolator 40 Table skip adjuster 41 Table pointer 56, 66 Filter device 57b to 57n, 67b to 67n Delay device 62a Conversion means 62b Parameter conversion table 62c Change distribution means

Claims (9)

[Claims] After dividing a signal into bands, each band signal is quantized and framed for each predetermined number of samples, and a scale factor that is a representative value of the amplitude of each band signal for each frame is generated. A reproducing apparatus that receives an encoded bit stream generated by multiplexing the quantized signal and the scale factor and reproduces a band-combined signal. Separating means for extracting the quantized signal and the scale factor; setting means for setting an amplification rate of the amplitude of the quantized signal for each band; and a setting means for setting the amplification rate for each band set by the setting means. hand,
Scale factor changing means for changing the value of the scale factor separated by the separating means, and multiplying the quantized signal extracted by the separating means by the scale factor changed by the scale factor changing means, and A decoding unit for decoding the signal into a signal; and a band synthesizing unit for reproducing a signal whose frequency has been corrected with respect to the original signal by performing band synthesis on each band signal decoded by the decoding unit. A reproducing apparatus characterized by the above-mentioned. 2. After the signal is divided into bands, each band signal is quantized and framed for each predetermined number of samples, and a scale factor which is a representative value of the amplitude of each band signal for each frame is generated. A reproducing apparatus that receives an encoded bit stream generated by multiplexing a scale factor index obtained by symbolizing the value of the scale factor and the quantized signal and reproduces a band-synthesized signal, Separating means for extracting the quantized signal and the scale factor index for each band from an encoded bit stream; setting means for setting an amplification factor of the amplitude of the quantized signal for each band; setting by the setting means Depending on the amplification rate for each band
Scale factor index changing means for changing the value of the scale factor index separated by the separating means; scale factor dequantizing means for converting the scale factor index output from the scale factor index changing means to a scale factor; Decoding means for multiplying the quantized signal extracted by the separating means by the scale factor output from the scale factor inverse quantizer, and decoding each band signal, and decoding by the decoding means A band synthesizing unit for reproducing a signal whose frequency has been corrected with respect to the original signal by band-synthesizing each band signal. 3. A scale factor level interpolating means for further subdividing the minimum unit of the scale factor between the scale factor changing means and the decoding means, wherein the setting means amplifies the amplitude of each band. When the change of the rate is instructed, the scale factor changing means changes the scale factor stepwise from the value before the change to the value after the change by the minimum unit amount, and the scale factor level interpolating means changes the scale factor. 2. The reproduction according to claim 1, wherein the minimum unit amount of the factor is further subdivided and changed at a predetermined step width, and the step width is controlled so that the change of the scale factor of all the bands is completed in the same time. apparatus. 4. A scale factor level interpolating means for further subdividing a minimum unit amount of an index is provided between the scale factor inverse quantizing means and the decoding means. When the change of the amplification factor is instructed, the scale factor index changing means changes the scale factor index stepwise by a minimum unit amount from the value before the change to the value after the change, and the scale factor level interpolating means 3. The method according to claim 2, wherein the minimum unit amount of the scale factor is further subdivided and changed by a predetermined step width, and the step width is controlled so that the change of the scale factor of all bands is completed in the same time. The playback device as described in the above. 5. The scale factor level interpolation means, wherein the resolution of the scale factor level interpolation is N
An interpolation level setting table for dividing a level change corresponding to a change value of the minimum unit of the scale factor into N equal parts, and an interpolation level value indicated in the interpolation level setting table multiplied by a scale factor output from the scale factor changing means. 4. The reproducing apparatus according to claim 3, further comprising a table interpolating means for performing the operation. 6. The scale factor level interpolation means, wherein the resolution of the scale factor level interpolation is N
An interpolation level setting table for dividing a level change corresponding to a change value of the minimum unit amount of the scale factor into N equal parts, and a scale factor output from the scale factor inverse quantization means by using an interpolation level value indicated in the interpolation level setting table 5. A reproducing apparatus according to claim 4, further comprising a table interpolation means for multiplying by. 7. The change time of the amplification factor of each band signal is T, the resolution of the scale factor level interpolation is N, the number of interpolations of the scale factor level interpolation per unit time is STP, and the change value of the scale factor index of each band signal is DS.
Wherein the scale factor level interpolation means has a step width adjustment means for adjusting the step width so that the table step width SKP per level interpolation becomes SKP = N * DS / (STP * T). The playback device according to claim 4, wherein 8. The setting means has a function of setting an amplification factor of an amplitude of a quantized signal for each band of a bit stream and a function of setting an amplification factor of an amplitude of a specific bandwidth not limited to each bandwidth. Wherein, for a decoded signal of a band decoded by the decoding unit, a filter unit that changes a frequency characteristic of a specific band set by the setting unit, the decoding unit and the band synthesizing unit The playback device according to claim 1, wherein the playback device is provided between the playback devices. 9. The method according to claim 9, wherein the setting unit includes a parameter conversion unit that converts the psychological amount into an amplification factor of each band so that a listener can set the amplification factor of each band by a psychological amount of sound. Claim 1 to claim
9. The reproduction device according to any one of items 8 to 8.