JP2005165183A - Wireless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in which a conventional wireless transmission device which varies the transmission rate of an audio codec requires additional information not meeting the standards of the codec or increases compressibility for a section whose information amount is large. <P>SOLUTION: A soundless decision means A2 makes soundless decisions on respective sub-band components of an input audio signal and a transmission rate specifying means A3 which inputs decision results specifies transmission rates by the sub-band components according to the decision results and supplies them to a compressing means A1. The transmission rate is made low for a sub-band component whose soundless decision result is true. The compressing means A1 compresses the respective sub-band components according to supplied transmission rates and sends them out to a transmitting means B. Each sub-band component is compressed at a transmission rate corresponding to its information amount, so the power consumption is reduced. The soundless decision means A2 and transmission rate specifying means A3 are incorporated in a main body of a band-division encoding means A, thereby realizing optimum band-division encoding processing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless communication apparatus that performs communication while compressing voice information by band division coding and changing a transmission rate according to the amount of information, and more particularly to a technique for promoting reduction of power consumption.

  Among communication devices equipped with a conventional audio codec, for example, Japanese Patent Application Laid-Open No. H10-228667 discloses a device that aims to reduce power consumption by changing the transmission rate of a compressed audio signal. There, the transmission power is reduced by providing a mechanism for designating the maximum transfer rate for the variable rate audio codec device. However, in this example, the transmission rate is reduced only in the signal section where the amount of information is large, unless the existing voice codec apparatus to be controlled is a system that allows the specification of the maximum transfer rate from the beginning. As a result, the compressed signal to be transmitted does not match the information amount of the original signal.

  However, currently known variable-rate audio compression apparatuses using band division coding generally specify an average transmission rate. Therefore, it is considered ideal to control by changing the average transmission rate instead of limiting the maximum transmission rate as in the conventional example.

  Further, among the variable rate audio codec devices, Patent Document 2 is known as one that increases the compression rate of the silent section. However, in these conventional examples, it is necessary to newly add data indicating the length of the silent state to the compressed signal, and processing that does not fit in the standard of the existing compression method is required on the receiving side. Further, in this example, silence determination is performed by blocking the input PCM signal in a certain section.

However, in the currently known band division coding, the amplitude determination is performed after the original signal is converted into a subband component by filtering. Therefore, if the conventional silence determination method is applied as it is, the same processing must be repeated twice, which is not efficient.
JP-A-7-283758 (page 3, FIG. 1) Japanese Patent Laid-Open No. 11-52990 (page 3-5, FIG. 1)

  The silent compression means disclosed in the above-mentioned Patent Document 2 cannot be applied to an existing compression format as it is, or a new mechanism is required in a higher layer than the compression device, so that it can be applied to a communication device. Not optimal. In addition, when compression by band division coding is used, the same processing is repeatedly performed, which is not an optimal means.

  Moreover, in the low power consumption means of the wireless communication apparatus disclosed in Patent Document 1 described above, when an existing codec is used, there is a possibility that the transmission rate is compressed only in a section with a large amount of information. As a result, the transmitted signal does not necessarily correspond to a change in the information amount of the original signal.

  The present invention takes the following means in order to solve the above problems.

  This will be described with reference to FIG. The wireless communication apparatus of the present invention includes band division encoding means A and transmission means B for transmitting a signal with transmission power corresponding to the transmission rate of the output signal of band division encoding means A. Furthermore, the silence determination means A2 for determining the silence portion of the input audio signal from each subband component of the input audio signal to the compression means A1 in the band division encoding means A, and the compression means according to the determination result by the silence determination means A2. Transmission rate specifying means A3 for specifying the transmission rate of the output signal of A1.

  Silence determination means A2 performs silence determination for each subband component of the input audio signal, and gives the determination result to transmission rate designation means A3. The transmission rate designating unit A3 designates the transmission rate for each subband component according to the determination result of the silence determination, and gives it to the compression unit A1. For subband components for which silence determination is true, the transmission rate is lowered. The compression means A1 compresses each subband component according to the given transmission rate and sends it to the transmission means B. In this way, each subband component can be compressed at a transmission rate corresponding to the amount of information, and power consumption can be reduced. In this case, since the silence determination unit A2 and the transmission rate designation unit A3 are incorporated in the main body of the band division encoding unit A, it is possible to realize the band division encoding process optimal for reducing power consumption.

  Further, silence is determined for each subband component after the time domain signal is converted to the frequency domain, so that the DC component is particularly included when the analog signal includes a DC component, such as an input audio signal. It is possible to accurately perform the silence determination excluding the influence of.

  The compressed and output audio signal conforms to a predetermined format even during silence compression, and there is no need to change the upper layers of the transmission device and the reception device.

  In the above aspect, a preferable aspect is further provided with a silence determination threshold setting unit that holds a variable threshold for determining a silent part of the input audio signal and can set the threshold in the silence determination unit.

  When noise is mixed in the input audio signal, if the threshold value for silence determination is set above the noise level, the audio signal component masked by the noise can be determined as silence, and further communication power Can be reduced.

  Further, in the above preferred embodiment, a silence determination threshold setting unit that holds a plurality of stepwise thresholds for determining a silent part of the input audio signal and can set any one threshold in the silence determination unit. It is set as the structure provided with. The transmission rate designating unit is configured to specify the transmission rate of the output signal of the compression unit in a stepwise manner according to the determination result of the silence determination based on the threshold set in the silence determination unit. .

  Since the threshold for silence determination can be set in stages, and the transmission rate at the time of silence can be specified in stages accordingly, a finer and more flexible power saving effect can be obtained.

  In addition, a preferable aspect in the above further includes a subband silence determination threshold setting unit that holds a plurality of thresholds corresponding to each frequency band of the band division coding as a threshold for the silence part determination of the input audio signal. That is, it has a configuration provided. Then, the silence determination means reads a corresponding threshold value from the subband silence determination threshold setting means according to the band frequency of the silence portion of the input audio signal, and uses the threshold to perform silence determination on the subband component. Configured to do.

  Since the threshold for silence determination can be set for each frequency band, even if noise is mixed only in a certain frequency band of the input audio signal, the audio signal component masked by the noise is also determined as silence and low transmission Low power consumption is realized by giving a rate. Or, for input audio signals that do not need to be transmitted in some frequency bands, as in the case of speech, by setting a high silence threshold for unnecessary or unimportant frequency bands, low power consumption Is realized. In this case, since the other subband components are not determined to be silent, there is no fading in terms of hearing or practical use.

  In the wireless communication apparatus including the silence determination unit, the transmission rate designating unit is preferably configured as follows. Reference transmission rate designating means for holding a reference transmission rate when the input audio signal is not silent; and silence transmission rate designating means for holding a silent transmission rate when the input audio signal is silent When the silence determination means does not detect silence, the reference transmission rate from the reference transmission rate designation means is selected, while when the silence determination means detects silence, the silence transmission rate designation means from the silence transmission time designation means. Transmission rate specifying means comprising transmission rate selection means for selecting a transmission rate and giving it to the compression means.

  The above invention can be developed as follows with respect to a band division coding wireless communication apparatus that can use a joint stereo format that uses a sum / difference signal instead of an L / R signal.

  A wireless communication apparatus according to the present invention includes an audio signal compression unit using band division coding capable of using a joint stereo format, and a transmission unit that transmits a signal with a transmission power corresponding to a transmission rate of an output signal of the compression unit. And a joint stereo applicability determination unit that can determine whether the compression unit can apply the joint stereo format for each subband by the band division coding. Further, it further comprises transmission rate designating means for designating the transmission rate of the output signal of the compression means in accordance with the number of subbands for which joint stereo application is determined by the joint stereo application availability determining means.

  The joint / stereo applicability determination means obtains a sum / difference component from the L channel component and the R channel component of each subband component, and similarly calculates a scale factor. Then, the normal scale factor and the sum / difference component scale factors are compared for each subband, and joint stereo is adopted for the subbands that can compress the amount of information. The transmission rate designating unit designates a transmission rate according to the number of subbands for which joint stereo is determined to be applied, and supplies the transmission rate to the compression unit. For subbands with joint stereo, the transmission rate is lowered. The compression means compresses each subband component in accordance with the given transmission rate and sends it to the transmission means. In this way, each subband component can be compressed at a transmission rate according to the application of joint stereo, and power consumption can be reduced. In this case, since the joint / stereo applicability determination unit and the transmission rate designation unit are incorporated in the main body of the band division encoding unit, it is possible to realize a band division encoding process optimal for low power consumption.

  The compressed and output audio signal conforms to a predetermined format even when joint stereo is applied, and there is no need to change the upper layers of the transmission device and the reception device.

  A preferable aspect in the above is that the apparatus further includes a joint application effect extracting means for generating effect information of information amount saving by application of joint stereo. The joint application effect extraction means compares the scale factor of each subband component of the input audio signal by the joint stereo application applicability determination means and the sum or difference scale factor of the channel components of each subband component. Then, the effect information of the information amount saving by applying the joint stereo is generated and given to the transmission rate specifying means. The transmission rate designating unit is configured to designate the transmission rate in consideration of the information amount saving effect information from the joint application effect extracting unit.

  The amount of information saved by applying joint stereo can be calculated more accurately. In the input audio signal, a portion with a small amount of information has an effect of lowering the transmission rate, and a portion with a relatively large amount of information can prevent the transmission rate from being lowered too much, thereby realizing more efficient communication power control.

  Further, in the above, a preferable aspect is configured such that the transmission rate designation means designates the transmission rate in consideration of the effect information of auditory masking for each subband by the band division coding in the compression means. It is that you are.

  The amount of information saved by applying joint stereo, taking into account the ease of hearing for humans, is more accurately calculated. In the input audio signal, a portion with a small amount of information has an effect of lowering the transmission rate, and a portion with a relatively large amount of information can prevent the transmission rate from being lowered too much, thereby realizing more efficient communication power control.

  In the wireless communication apparatus including the joint stereo applicability determination unit, the transmission rate designation unit is preferably configured as follows. A reference transmission rate specifying means for holding a reference transmission rate; a transmission rate adjustment coefficient specifying means for holding a transmission rate adjustment coefficient; and the joint stereo for the reference transmission rate from the reference transmission rate specifying means. Transmission rate specifying means comprising transmission rate calculation means for calculating a transmission rate for the compression means by correcting the information from the applicability determination means and the transmission rate adjustment coefficient from the transmission rate adjustment coefficient specifying means.

  In any of the above wireless communication apparatuses, the transmitting means is preferably a transmitting means for transmitting a signal with a transmission power having a time average value proportional to the transmission rate.

  According to the present invention, in a wireless communication apparatus that compresses an audio signal by band division coding and transmits the transmission rate while varying the transmission rate according to the amount of information, the conventional mechanism for transmission rate compression is a band division coding means. By incorporating it into the main body, it is possible to control the transmission rate more accurately according to the information amount of the transmitted signal. In other words, it is possible to further reduce the power consumption of the communication device for an audio signal of equivalent sound quality.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a wireless communication apparatus according to the present invention will be described below in detail with reference to the drawings.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a wireless communication apparatus according to the present invention will be described below with reference to the drawings. The wireless communication devices described below are all wireless communication devices configured as shown in FIG.

  In FIG. 2, when an audio original signal S1 that is an input audio signal is input to the band division encoding apparatus 1, the band division encoding apparatus 1 compresses the audio original signal S1 by band division encoding, and an audio compression signal S2 Is output. The transmitter 2 modulates the audio compressed signal S2 and transmits a radio signal.

  The band division coding apparatus 1 of FIG. 2 can be generally expressed by a block diagram as shown in FIG.

  In the embodiment described below, operations other than those corresponding to the band division encoding apparatus 1 in FIG. 2 are the same as those in FIG. 2, and therefore only the band division encoding apparatus part will be described.

(Embodiment 1)
FIG. 3 is a block diagram showing the configuration of the band division coding apparatus according to Embodiment 1 of the present invention. The compression means A1 of FIG. 1 includes a filter unit 3, a quantization / frame formation unit 4, a scale factor calculation unit 5, and a bit allocation calculation unit 6. The silence determination means A2 is composed of a silence determination unit 8. The transmission rate designation means A3 includes a reference transmission rate designation unit 7, a silent transmission rate designation unit 9, and a transmission rate selection unit 10.

  When the audio source signal S1 (PCM signal) is input, the filter unit 3 blocks the audio source signal S1 for a predetermined time interval, performs a filter process, and converts this into a component S3 of each frequency region (subband). To do. The scale factor calculation unit 5 calculates a scale factor S4 that is maximum amplitude information for each subband of the subband component S3. The silence determination unit 8 to which the scale factor S4 is input holds a preset silence determination threshold Th. The silence determination unit 8 compares the silence determination threshold Th with each subband component of the scale factor S4. When the silence determination unit 8 determines that all the subband components of the scale factor S4 are small, the silence detection signal S8 is sent to the transmission rate selection unit 10. Output. Specifically, for example, when the silence determination threshold Th = 0 and the subband components of the scale factor S4 are all 0, the silence detection signal S8 is true. Alternatively, when the silence determination threshold Th = 2 and all the subband components of the scale factor S4 are 2 or less, the silence detection signal S8 is true.

  The reference transmission rate designating unit 7 holds in advance the transmission rate when the audio original signal S1 is not silent, and outputs this set value as the reference transmission rate S6. The silent transmission rate designation unit 9 holds in advance the transmission rate when the audio original signal S1 is in the silent state, and outputs this set value as the silent transmission rate S7. When the silence detection signal S8 is true, that is, the audio source signal S1 is silent, the transmission rate selection unit 10 selects the silent transmission rate S7 and outputs it as the designated transmission rate S9. On the other hand, when the silence detection signal S8 is false, the reference transmission rate S6 is selected and output as the designated transmission rate S9.

  The bit allocation calculation unit 6 calculates a bit allocation S5 for each subband based on the scale factor S4 and the designated transmission rate S9. The quantization / frame formation unit 4 quantizes the subband component S3 based on the bit allocation S5, forms a predetermined frame format by a compression method, and outputs the result as an audio compression signal S2.

  According to the configuration of the present embodiment, it is not necessary to provide an audio source signal blocking and silence determination mechanism outside the band division coding apparatus. And since silence determination can be performed by a slight change in the encoding process, the overall processing amount can be reduced.

  Also, unlike the conventional silence determination method, since the determination is performed after the time domain signal is converted to the frequency domain, the audio source signal is a direct current, particularly when the audio source signal is an analog signal A / D converted. When the component is included, it is possible to accurately determine and compress the silent portion excluding the influence of the DC component.

  Furthermore, the audio compression signal output from the band division coding apparatus and the audio compression signal sent to the reception side of the wireless communication apparatus are always based on a predetermined format even during silence compression. For this reason, there is no need to change the upper layer of the reception side device and the transmission side device.

(Embodiment 2)
FIG. 4 is a block diagram showing the configuration of the band division coding apparatus according to Embodiment 2 of the present invention. It differs from FIG. 3 of Embodiment 1 in that the configuration of the silence determination unit 8 and the silence determination threshold setting unit 11 are newly added. In the following, portions that operate in the same manner as in the first embodiment will be omitted, and only differences will be described.

  The silence determination unit 8 differs from that in the first embodiment in that the silence determination threshold can be updated. The silence determination threshold setting unit 11 holds a silence determination threshold S10, and the silence determination threshold S10 can be updated at any time by the user. The silence determination unit 8 acquires this value every time the value of the silence determination threshold S10 changes, and uses this value as a threshold for silence determination from the next silence determination. The other operations are the same as those in the first embodiment.

  According to the configuration of the present embodiment, in addition to the effects of the first embodiment, the silence determination threshold can be changed, so that when a certain level of noise is mixed during the input of the audio original signal, This makes it possible to perform silence determination in consideration of the influence of this noise. That is, by setting the silence determination threshold above the noise level, it is possible to determine that the audio signal component masked by noise is also silent, and further reduce communication power.

(Embodiment 3)
FIG. 5 is a block diagram showing the configuration of the band division coding apparatus according to Embodiment 3 of the present invention. The configuration and operation of the silence determination threshold value setting unit 12, the silence determination unit 13, the silent transmission rate designation unit 14, and the transmission rate selection unit 15 are different from those in FIG. In the following, portions that operate in the same manner as in the second embodiment will be omitted, and only differences will be described.

Silence determination threshold setting unit 12, N pieces of sound determination threshold Th ₁ ~Th _{N (N} is an integer) holds the, a relationship of _{Th 1> Th 2>···>} Th N. The threshold values Th _{1 to} Th _N can be updated at any time by the user. The threshold values Th _{1 to} Th _N are output from the silence determination threshold value setting unit 12 as the silence determination threshold value S11. The silence determination unit 13 acquires this value every time the value of the silence determination threshold S11 changes, and uses this value as a threshold for silence determination from the next silence determination. The determination operation of the silence determination unit 13 is as follows.

The silence determination unit 13 acquires silence determination thresholds Th _{1 to} Th _N from the silence determination threshold S11. When scale factor S4 from scale factor calculating section 5 is inputted, compares each subband component of silence determination threshold Th ₁ and scale factor S4, when the sub-band component of the scale factor S4 is determined that all small (e.g. scale When all the subband components of the factor S4 are equal to or less than the silence determination threshold Th ₁ , the value of the silence level signal S12 is set to “1” (in the initial state, S12 = 0 and represents a silence state). If it is not determined that all the sub-band components of the scale factor S4 are small, the previous value of the silence level signal S12 is continuously output, and the determination operation ends. The comparison operation with the silence determination threshold Th ₁ is completed as described above, and the comparison operation with the silence determination threshold Th ₂ is started only when it is determined that all the subband components of the scale factor S4 are small. Thereafter, the same operation is repeated from the silence determination thresholds Th _{2 to} Th _N.

That is, when the scale factor S4 is input, the silence determination threshold Th _M (1 ≦ M ≦ N) is compared with each subband component of the scale factor S4, and it is determined that all the subband components of the scale factor S4 are small. (For example, when all the subband components of the scale factor S4 are equal to or less than the silence determination threshold Th _M ), the value of the silence level signal S12 is set to M, and the comparison operation with the silence determination threshold Th _(M−1) is started. If it is not determined that all the sub-band components of the scale factor S4 are small, the previous value of the silence level signal S12 is continuously output, and the determination operation ends. The above is the determination operation of the silence determination unit 13.

  As a result, the silence level signal S12 is determined to any value of 0, 1, 2,..., N and is input to the transmission rate selection unit 15.

When the transmission rate designating unit 14 silence holds the silence determination threshold held in the threshold setting portion 12 and the same number of N silence during transmission rate _{Rt 1 ~Rt N, Rt 1>} Rt 2>···> Rt _N relationship. The rates Rt _{1 to} Rt _N can be updated at any time by the user. The transmission rate selection unit 15 acquires the silence level signal S12 every time the series of comparison operations of the silence determination unit 13 is completed, and selects the reference transmission rate S6 when S12 = 0, and calculates the bit allocation as the designated transmission rate S9. Output to unit 6. On the other hand, when 1 ≦ S12 ≦ N, the silent transmission rate Rt _X corresponding to “X” of the threshold Th _X indicated by the silent level signal S12 is selected by the silent transmission rate designating unit 14, and the silent transmission rate S13. And output to the bit allocation calculating unit 6 as the designated transmission rate S9. Subsequent operations are the same as those described in the first and second embodiments.

  According to the configuration of the present embodiment, in addition to the effects of the second embodiment, the silence determination threshold and the transmission rate during silence can be set in stages, so that the details according to the power saving effect desired by the user can be obtained. Transmission rate control is possible.

  In addition to using thresholds that can be set multiple times to determine whether the sound is nearly silent, for example, the thresholds are set in such a way as to equally divide the maximum amplitude of the input audio signal, and transmitted stepwise according to the input amplitude. Usage such as slightly reducing the rate is also possible, and flexible communication power control can be realized.

(Embodiment 4)
FIG. 6 is a block diagram showing a configuration of a band division coding apparatus according to Embodiment 4 of the present invention. It differs from FIG. 3 of Embodiment 1 in the point that the configuration of the silence determination unit 17 and the subband silence determination threshold setting unit 16 are newly added. In the following, portions that operate in the same manner as in the first embodiment will be omitted, and only differences will be described.

The subband silence determination threshold setting unit 16 holds _K subband silence determination thresholds Tf _{1 to} Tf K when using band division encoding that divides the audible band into K (K is an integer). The threshold values Tf _{1 to} Tf _K can be updated at any time by the user. The threshold values Tf _{1 to} Tf _K are output to the silence determination unit 17 as the silence determination threshold S14. The silence determination unit 17 acquires this value every time the value of the silence determination threshold S14 changes, and uses this value as a threshold for silence determination from the next silence determination. The determination operation of the silence determination unit 17 is as follows.

The silence determination unit 17 in the present embodiment has a function of determining each subband component (S4 _{−1 to} S4 _−K ) of the scale factor S4 using individual silence determination thresholds. When S4- _X is compared with the threshold value Tf _X (X = 1 to K) and it is determined that all the subband components of the scale factor S4 are smaller than the threshold value, it is determined that the audio original signal S1 is in a silent state. And true is output to the silence detection signal S8. The subsequent operation is the same as in the first embodiment.

  According to the configuration of the present embodiment, in addition to the effects of the first embodiment, the silence determination threshold can be set for each frequency band, so that noise is mixed only at a certain frequency of the input audio signal. In cases where there is no problem even if some frequency bands of the input audio signal are not transmitted (such as when the input data content is speech), it is possible to set a high silence threshold for unnecessary or unimportant frequency bands. Further, the effect of further reducing the power consumption can be obtained while maintaining no audibility or practically inferiority.

(Embodiment 5)
FIG. 7 is a block diagram showing a configuration of a band division coding apparatus according to Embodiment 5 of the present invention. In general, a band division coding apparatus having a joint stereo coding function can be expressed as shown in FIG. FIG. 7 of the present embodiment differs in that a transmission rate calculation unit 19 and a transmission rate adjustment coefficient designation unit 20 are added.

  Hereinafter, the operation of the band division coding apparatus of FIG. 7 will be described with reference to the drawings.

  In FIG. 7, when an audio source signal S1 (PCM signal) is input, the filter unit 3 blocks the audio source signal S1 for a predetermined time interval and performs a filter process, and this is processed in each frequency region (subband). Convert to component S3. The joint / stereo applicability determination unit 18 in FIG. 7 includes the same functions as the scale factor calculation unit 5 in FIG. The joint / stereo application applicability determination unit 18 calculates a scale factor that is maximum amplitude information for each subband of the subband component S3. At the same time, a sum / difference component (for example, (L + R) / 2 and (LR) / 2) is obtained from the L channel component and the R channel component of the subband component S3, and these sum / difference components are also obtained. Similarly, the scale factor is calculated. Then, the normal scale factor and the sum / difference component scale factors are compared for each subband. As a result, the joint stereo (instead of the LR signal) is used for subbands that can compress the amount of information. Adopt sum / difference signal). Information about which subband the joint stereo is applied to is output as a joint stereo application subband designation signal S15. To the scale factor S4, the scale factor of the sum / difference signal is output for the subband to which the joint stereo is applied, and the scale factor of the LR signal is output for the other subbands.

  The transmission rate adjustment coefficient designation unit 20 holds the transmission rate adjustment coefficient S16 and outputs it to the transmission rate calculation unit 19. The reference transmission rate designation unit 7 holds the reference transmission rate S6 and outputs it to the transmission rate calculation unit 19. The transmission rate calculation unit 19 determines the actual designated transmission rate S9 based on the reference transmission rate S6 using the joint / stereo application subband designation signal S15 and the transmission rate adjustment coefficient S16.

  Specifically, for example, the reference transmission rate S6 is a transmission rate when joint stereo is not used in any subband, and the number of subbands in which joint stereo obtained from the joint stereo application subband designation signal S15 is used. If NJ is NJ, a method of subtracting from the reference transmission rate S6 with the transmission rate adjustment coefficient S16 as a proportional constant according to NJ is used as the designated transmission rate S9 (that is, S9 = S6-S16 × NJ). It is done. The bit allocation calculation unit 6 calculates a bit allocation S5 for each subband based on the scale factor S4 and the designated transmission rate S9. The quantization / frame formation unit 4 quantizes the subband component S3 based on the bit allocation S5, forms a predetermined frame format by a compression method, and outputs the result as an audio compression signal S2.

  According to the configuration of the present embodiment, the sound quality improvement effect at the equal transmission rate by using joint stereo can be used for reducing communication power. That is, in the conventional configuration shown in FIG. 11, as long as the reference transmission rate S6 is constant, the saved amount of information due to the joint stereo application is redistributed to the entire band in the bit allocation calculation unit 6. Although it contributed to the improvement, it did not contribute to the decrease in the transmission rate. On the other hand, in this embodiment, it is possible to determine the amount of information saved due to the application of joint stereo and reduce the transmission rate correspondingly, which can greatly contribute to the reduction of communication power.

(Embodiment 6)
FIG. 8 is a block diagram showing a configuration of a band division coding apparatus according to Embodiment 6 of the present invention. This embodiment differs from FIG. 7 of the fifth embodiment in that a configuration of the transmission rate calculation unit 22 and a joint application effect extraction unit 21 are newly added. In the following, portions that operate in the same manner as in the fifth embodiment will be omitted, and only differences will be described.

  The joint / stereo applicability determination unit 18 is functionally the same as in FIG. 7 of the fifth embodiment, but can output scale factor information S17. The scale factor information S17 represents all values of the scale factor of the L / R signal and the scale factor of the sum / difference signal in the fifth embodiment.

  The joint application effect extraction unit 21 compares the sum of the scale factors of the L and R signals and the sum of the scale factors of the sum and difference signals in the subbands to which joint stereo is applied, and reduces the amount of information by applying joint stereo. Ask for. For example, a result obtained by subtracting the sum of the scale factors of the sum and difference signals from the sum of the scale factors of the L and R signals is used as the information saving effect, and is output as joint stereo application effect information S18.

  The transmission rate calculation unit 22 determines the actual designated transmission rate S9 based on the reference transmission rate S6 by using the joint / stereo application subband designation signal S15, the transmission rate adjustment coefficient S16, and the joint / stereo application effect information S18. To do. Specifically, for example, the actual designated transmission rate is increased or decreased by increasing or decreasing the reference transmission rate S6 according to the product size of the sum of the application effect information S18 and the transmission rate adjustment coefficient S16 in the subband to which joint stereo is applied. S9 is determined (that is, S9 = S6-S16 × Σ {S18}). The subsequent operation is the same as in the fifth embodiment.

  According to the configuration of the present embodiment, the amount of information saved by applying joint stereo can be calculated more accurately than the configuration of the fifth embodiment. Therefore, the transmission rate can be lowered at a portion where the information amount is small in the input audio signal, and an effect of preventing the transmission rate from being lowered too much at a portion where the information amount is relatively large, and more efficient communication power control can be realized.

(Embodiment 7)
FIG. 9 is a block diagram showing a configuration of a band division coding apparatus according to Embodiment 7 of the present invention. The configuration of the transmission rate calculation unit 23 and the bit allocation calculation unit 24 is different from FIG. 7 of the fifth embodiment. In the following, portions that operate in the same manner as in the fifth embodiment will be omitted, and only differences will be described.

  The bit allocation calculation unit 24 outputs the auditory model information S19 to the transmission rate calculation unit 23 before the transmission rate calculation unit 23 calculates the designated transmission rate S9. Here, the auditory model information S19 represents the magnitude of the auditory masking effect in each subband, and is used in bit allocation processing in general band division coding.

  The transmission rate calculation unit 23 determines the designated transmission rate S9 based on the reference transmission rate S6 using the information of the joint stereo application subband designation signal S15, the transmission rate adjustment coefficient S16, and the auditory model information S19. Hereinafter, the operation of the transmission rate calculation unit 23 will be described with a specific example.

When using band division encoding with the number of subbands = 4, subbands to which joint stereo is applied are subbands Sb _{1 to} Sb ₄ (Sb ₁ is the lowest range and Sb ₄ is the highest range). Sb ₁ and Sb ₂ are assumed. Furthermore, it is assumed that the masking effect obtained from the auditory model information S19 (the larger the greater the difficulty in hearing) is “5”, “1”, “1”, “5” for each of the subbands Sb _{1 to} Sb _4. . In this case, (1/5 + 1/1 + 0/1 + 0/1) × S16 is set as a proportional constant, and the reference transmission rate S6 is reduced to a designated transmission rate S9. In other words, the application effect of joint stereo is weighted according to the ease of hearing. The components for the sub-bands Sb _{1 to} Sb ₄ of the joint / stereo application sub-band designation signal S15 at this time are S15 ₁ to S15 ₄ (joint / stereo application when 1), and the auditory model information S19 is directly applied to each sub-band. and represents the magnitude of the masking effect on, if the component is formula as an _S19 1 _{~S19 4,}
S9 = S6-S16 × Σ {S15 _k / S19 _k } (k = 1 to 4)
It becomes. The operation example of the transmission rate calculation unit 23 has been described above.

  The operation after the designated transmission rate S9 is determined is the same as in the fifth embodiment.

  According to the configuration of the present embodiment, the amount of information saved by applying joint stereo in consideration of the ease of hearing for humans can be calculated more accurately than the configuration in the fifth embodiment. Become. Therefore, the transmission rate can be lowered at a portion where the information amount is small in the input audio signal, and an effect of preventing the transmission rate from being lowered too much at a portion where the information amount is relatively large, and more efficient communication power control can be realized. In addition, a higher effect can be expected by using this embodiment in combination with the configuration in the sixth embodiment.

  The wireless communication apparatus according to the present invention enables high-quality and power-saving wireless transmission of audio signals, and is useful for applications for portable devices such as transmission between a portable audio player and wireless headphones. It can also be applied to audio transmission to surround speakers in multi-channel systems such as home theaters.

The block diagram which shows the structure of the radio | wireless communication apparatus of this invention 1 is a block diagram of a basic configuration of a radio communication apparatus using a band division coding method according to an embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of a band division coding apparatus according to Embodiment 1 of the present invention. Block diagram showing the configuration of a band division coding apparatus according to Embodiment 2 of the present invention Block diagram showing the configuration of a band division coding apparatus according to Embodiment 3 of the present invention Block diagram showing the configuration of a band division coding apparatus according to Embodiment 4 of the present invention. FIG. 9 is a block diagram showing a configuration of a band division coding apparatus in Embodiment 5 of the present invention. Block diagram showing a configuration of a band division coding apparatus according to Embodiment 6 of the present invention Block diagram showing the configuration of a band division coding apparatus according to Embodiment 7 of the present invention Block diagram showing the configuration of a conventional band division coding apparatus A block diagram showing a configuration of a band division coding apparatus having a joint stereo coding function in the prior art

Explanation of symbols

A Band division coding means A1 Compression means A2 Silence determination means A3 Transmission rate designation means B Transmission means 1 Band division coding apparatus 2 Transmission section 3 Filter section 4 Quantization / frame formation section 5 Scale factor calculation section 6 Bit allocation calculation section 7 Reference transmission rate designation unit 8 Silence determination unit 9 Silence transmission rate designation unit 10 Transmission rate selection unit 11 Silence determination threshold setting unit 12 Silence determination threshold setting unit having N silence determination thresholds 13 N silence determination thresholds Applicable silence determining unit 14 Silent transmission rate specifying unit with N transmission rates 15 Transmission rate selecting unit capable of supporting N stages of silence levels 16 Subband silence with silence determination threshold for each of K subbands Determination threshold setting unit 17 Silence determination unit capable of determining silence for each of K subbands 18 Joint stereo for each subband Use permission determination unit 19 transmission rate calculation unit 20 transmission rate adjustment factor specifying section 21 joint application effect extraction unit 22 transmission rate calculation unit 23 transmission rate calculation unit 24 bit assignment calculation portion S1 audio source signal (input audio signal)
S2 Audio compression signal S3 Subband component of audio source signal S1 S4 Scale factor S5 Bit allocation information for each subband S6 Reference transmission rate S7 Silence transmission rate S8 Silence detection signal S9 Designated transmission rate S10 Silence determination threshold S11 Silence determination threshold Th _{1 to} Th _N
S12 during a silent level signal S13 silence transmission rate Rt ₁ to RT _N
S14 Silence determination thresholds Tf _{1 to} Tf _K corresponding to the subbands Sb _{1 to} Sb _K
S15 Joint stereo application subband designation signal S16 Transmission rate adjustment coefficient S17 Scale factor information S18 Joint stereo application effect information S19 Auditory model information

Claims (10)

Audio signal compression means using band division coding;
A wireless communication device comprising: transmission means for transmitting a signal with transmission power corresponding to a transmission rate of an output signal of the compression means;
Silence determination means for determining a silence portion of the input audio signal from each subband component of the input audio signal to the compression means;
A wireless communication apparatus comprising: a transmission rate designating unit that designates a transmission rate of an output signal of the compression unit according to a determination result by the silence determination unit. The wireless communication apparatus according to claim 1, further comprising a silence determination threshold setting unit configured to hold a variable threshold for determining a silent part of the input audio signal and set the threshold in the silence determination unit. In addition, it includes a plurality of stepwise thresholds for determining a silent part of the input audio signal, and includes a silence determination threshold setting unit capable of setting any one threshold in the silence determination unit,
The transmission rate designating unit is configured to stepwise specify a transmission rate of an output signal of the compression unit in accordance with a determination result of silence determination based on the threshold set in the silence determination unit. The wireless communication device according to 1. Furthermore, as a threshold for the silent part determination of the input audio signal, comprising a subband silence determination threshold setting means for holding a plurality of thresholds corresponding to each frequency band of the band division coding,
The silence determination means reads a corresponding threshold value from the subband silence determination threshold setting means according to the band frequency of the silence portion of the input audio signal, and performs silence determination on the subband component using the threshold value. The wireless communication apparatus according to claim 1, which is configured as described above. The transmission rate designation means includes
A reference transmission rate specifying means for holding a reference transmission rate when the input audio signal is not in a silent state;
A silent transmission rate designation means for holding a silent transmission rate when the input audio signal is silent;
When the silence determination means does not detect silence, the reference transmission rate from the reference transmission rate designation means is selected, while when the silence determination means detects silence, the silence transmission rate designation means transmits from the silence transmission rate designation means. 5. The wireless communication apparatus according to claim 1, further comprising: a transmission rate selection unit that selects a rate and gives the compression unit to the compression unit. Means for compressing an audio signal using band-division coding capable of using a joint stereo format;
Transmitting means for transmitting a signal with transmission power corresponding to the transmission rate of the output signal of the compression means;
A wireless communication apparatus comprising joint stereo applicability determination means capable of determining applicability of the joint stereo format in the compression means for each subband by the band division coding,
Wireless communication comprising transmission rate designating means for designating a transmission rate of an output signal of the compression means according to the number of subbands for which joint stereo application is determined by the joint stereo application availability determining means apparatus. Further, the scale factor of each subband component of the input audio signal by the joint stereo applicability determination means is compared with the scale factor of the sum or difference of the channel components of each subband component, and the joint stereo application A joint application effect extraction means for generating information on the effect of reducing the amount of information by
7. The wireless communication apparatus according to claim 6, wherein the transmission rate designating unit is configured to designate the transmission rate in consideration of the information amount saving effect information from the joint application effect extracting unit. The transmission rate designation means is configured to designate the transmission rate in consideration of the effect information of the auditory masking for each subband by the band division coding in the compression means. A wireless communication device according to 1. The transmission rate designation means includes
A reference transmission rate specifying means for holding a reference transmission rate;
A transmission rate adjustment coefficient specifying means for holding a transmission rate adjustment coefficient;
The reference transmission rate from the reference transmission rate designating unit is corrected by the information from the joint stereo applicability determining unit and the transmission rate adjustment coefficient from the transmission rate adjustment coefficient designating unit, and the compression unit is corrected. 9. The wireless communication apparatus according to claim 6, comprising transmission rate calculation means for calculating a transmission rate. The wireless communication apparatus according to claim 1, wherein the transmission unit transmits a signal with a transmission power having a time average value proportional to the transmission rate.

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