Audio processing apparatus for implementing level corrections of audio data

A audio processing apparatus capable of judging and correcting volume levels of audio data, with a level judgment thinning controller for thinning the frequency of the level judgments provided therein, can reduce a throughput and implement the level judgments and corrections in the case of multi-channel input audio data maintaining the original number of the channels thereof. The audio processing apparatus, with a plurality of level judging devices and level correcting devices further provided therein, can implement audio processings at optional settings in response to users' preferences. The present invention thereby provides the capability of judging and correcting levels of the multi-channel audio data while maintaining the original number of the channels thereof.

FIELD OF THE INVENTION

This invention relates to a digital signal processing technology, more particularly, to a audio processing apparatus for implementing level corrections of audio data.

BACKGROUND OF THE INVENTION

The conventional sound source is mostly two-channel stereo audio. Therefore, a two-channel-wise audio processing is implemented in the case of a audio processing apparatus implementing level corrections of the conventional audio data. More specifically, volume levels are detected with respect to an inputted two-channel audio data and a level correction processing is implemented in accordance with the volume levels to thereby complete the level corrections of the audio data. This method is implemented by means of, for example, a audio processing apparatus shown inFIG. 17.

A conventional audio processing apparatus5000comprises a level judging unit5100and a level correcting unit5200. The level judging unit5100judges whether the volume levels of the audio data inputted from outside are larger or smaller than a given reference volume. The level correcting unit5200implements the level corrections according to the volume levels judged by the level judging unit.

The level judging unit5100retrieves one sample data for each channel from the inputted two-channel audio data, and compares the retrieved data from the two channels to thereby employ the larger value as a level detection data. The level judging unit5100then compares the level detection data with the reference volume serving to judge the volume levels, and transmits the comparison results in the form of level judgment result signals to the level correcting unit5200.

The level correcting unit5200, based on the level judgment result signals from the level judging unit5100, reduces the volumes when the inputted data is larger than the reference volume and increases the volumes when the inputted data is smaller than the reference volume. A smoothing processing is implemented between the output results in consequence of the foregoing processings and output data of a previous sample so that the smoothing-processed output is handled as output data of a current sample.

Such a audio processing apparatus is used for a vehicle-mounted audio apparatus and an audiovisual apparatus used in a limited volume at midnight. The audio processing apparatus, in the foregoing uses, can compress a dynamic range of the two-channel audio data, thereby enabling a small sound to be more easily heard. Therefore, the audio apparatus can be fully enjoyed in noise-penetrating environments such as a car interior and any situation where the sound volume must be reduced.

The apparatus employing the conventional audio processing is disclosed in No. 5-275950 of the publication of unexamined patent applications. According to the conventional technology, when the dynamic range of sound signals are compressed in the case of CD (compact disc) reproduction and the like, a property of excessive compression can be improved without deteriorating a distortion rate, and the dynamic range can be thereby normally compressed without any distortion.

In the case of processing DVD, which is rapidly spreading in recent years, and the like, it is necessary to process multi-channel audio data. When the conventional audio processing apparatus5000is applied to the multi-channel audio data, a possible method is to down-mix the multi-channel audio data into the two-channel one, which is thereafter inputted to the audio processing apparatus5000. However, the audio processing apparatus5000can only emit the two-channel output in spite of the multi-channel input source. On top of that, there is a problem as follow.

The audio data has been increasingly diversified in accordance with the evolution of the multi-channel audio data. It can be hardly said to be flexibly responding to users' needs for the audio processing if the audio processing is implemented to all the sound sources at a universally common standard. In the case of the two-channel stereo sound source, it is not particularly necessary to change settings between the right and left channels. On the contrary, in the Dolby Digital, for example, five channels in total, which are a left front channel, right front channel, center channel, and surround two channels, and LFE (Low Frequency Effect) recording low-frequency sound effects are independently recorded and reproduced without being blended with one another. In such a case, an optimum setting is diverse depending on the sound sources, for example, the center channel should be pealed most, the front channel should be emphasized, LFE should be emphasized or the like. The multiple settings are even further diversified due to the users' needs. However, it is difficult to optionally change the settings in the configuration where the audio data is down-mixed into the two channel data.

SUMMARY OF THE INVENTION

Therefore, a main object of the present invention is to provide a audio apparatus capable of correcting volume levels of inputted audio data including multi-channel audio data while maintaining an original channel number thereof without down-mixing the inputted audio data into two-channel one.

Another object of the present invention is to provide a audio processing apparatus capable of optionally changing settings such as methods of judging levels, reference values, and degrees of level corrections depending on the kinds of the inputted audio data, users' preferences, and the like.

In order to solve the foregoing problem, the audio processing apparatus according to the present invention comprises:a level judging unit for judging volume levels of inputted audio data;a level correcting unit for correcting the volume levels based on the judgment results from the level judging unit; anda level judgment thinning controller for adjusting how often the level judgments should be implemented by the level judging unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention are described referring to the drawings.

FIG. 1is a view illustrating a configuration of a audio processing apparatus1000according to Embodiment 1 of the present invention.

The audio processing apparatus1000comprises a level judging unit1100, a level correcting unit1200, and a level judgment thinning controller1300. The present invention is characterized in that the level judgment thinning controller1300is provided in the audio processing apparatus.

The level judging unit1100is comprised of a plurality of level judging devices each capable of judging levels of at least audio data for one channel. In the same manner, the level correcting unit1200is comprised of a plurality of level correcting devices each capable of correcting levels of at least the audio data for one channel. The level judgment thinning controller1300thins the operation of the level judging unit1100with respect to the inputted audio data to thereby reduce a throughput.

The audio processing apparatus1000, with the level judgment thinning controller1300provided therein, is capable of correcting volume levels of even the inputted audio data having a multiplicity of channels while maintaining the original number the channels without down-mixing the data into the two-channel data.

Referring toFIG. 2, the audio processing apparatus1000according to Embodiment 1 is further described in detail. Described below is the case in which the inputted audio data is the multi-channel audio data. Any component inFIG. 2, which is identical to those inFIG. 1, has the same reference number.

The audio processing apparatus1000comprises a level judging unit1100, level correcting unit1200, level judgment thinning controller1300, an information communicating device2000, and an input device1600.

The level judging unit1100comprises a plurality of (three in the present example) level judging devices1101-1103each having a similar structure. In the same manner, the level correcting unit1200comprises a plurality of level correcting devices1201-1203each having a similar structure. The respective level judging devices1101-1103and level correcting devices1201-1203correspond one on one to each other. The audio processing apparatus1000further comprises a calculating coefficient memorizing device1400and a level judging device number switching device1500. The calculating coefficient memorizing device1400memorizes reference volumes respectively determined by first and second level correction parameters. The level judgment thinning controller1300comprises a per-decoder level judgment thinning controller switching device1310.

The input device1600, in response to input operation conducted by a user of the audio processing apparatus1000, transmits the input operation information to the information communicating device2000.

The operation of the audio processing apparatus1000is hereinafter described. The level judgment thinning controller1300receives decoder information S01indicating signal forms of the input audio data via the information communicating device2000. Signal forms in the present embodiment include, for example, stereo audio, the Dolby Digital, and the like. The decoder information S01is the information appended to input audio data S06and inputted from outside to the audio processing apparatus1000together with the input audio data S06.

The level judgment thinning controller1300determines how often an thinning processing should be implemented based on the decoder information S01. To be more specific, the controller1300, based on the decoder information S01indicating the signal forms of the input audio data (stereo audio, the Dolby Digital, and the like), determines the thinning frequency suitable for the level judgment of each channel data of the audio data of the signal forms without any problem in any of the level judging devices1101-1103. The controller1300transmits level judgment interval information S02indicating the determined thinning frequency to the level judging a unit1100.

The level judging device number switching device1500receives level judging device number information S03indicating the number of the level judging devices1101-1103of the level judging unit1100suitable for processing the audio data via the information communicating device2000. The level judging device number information S03is inputted to the input device1600by the user of the audio processing apparatus1000to be thereby supplied to the information communicating device2000. To describe the number of the level judging devices suitable for processing the audio data, it refers to the number of the level judging devices matching with the number of the channels of the audio data. The number of the level judging devices corresponding one on one to the respective channels of the audio data is designated by means of the level judging device number information S03. However, any single level judging device of the level judging unit1100may be designated to correspond to the multiple channels of the audio data.

The level judging device number switching device1500, based on the designated number of the level judging devices, creates operation-instructing information S04and transmits the information S04to the level judging unit1100. At that time, the level judging device number switching device1500implements the following processing based on the level judging device number information S03. The level judging device number information S03designates the number of the level judging devices1101-1103corresponding to the respective channels of the audio data (multi-channel data) inputted as described. The level judging device number switching device1500, in the wake of receiving the level judging device number information S03indicating the described information, specifies the X number (X≦the total number of the level judging devices) of the level judging devices1101-110X designated from the plural level judging devices1101-1103by the level judging device number information S03. The level judging device number switching device1500then transmits the operation-instructing information S04to the designated level judging devices1101-110X respectively. The level judging device number switching device1500thereby designates the level judging devices1101-110X judging the levels of the respective channel data of the inputted audio data and transmits the operation-instructing information S04to the designates level judging devices1101-110X.

The level judging devices1101-110X, in the wake of receiving the operation-instructing information S04, implements the judgments. Specifically, the level judging devices1101-110X implement the level judgments with respect to the input audio data based on the operation-instructing information S04and level judgment interval information S02. The level judging devices1101-110X, in doing so, implement the judgments while thinning the level judgment processing at a frequency level designated by the level judgment interval information S02. More specifically, the level judging devices1101-110X do not implement the level judgments at all time points of a sampling period2100set in the audio processing apparatus1000, as shown inFIG. 3A. The level judging devices1101-110X periodically thin an optional number of time points21001−m(m<n) from all the time points21001−ndefined in the sampling period2100based on an optional thinning period, as shown inFIG. 3B, to thereby implement the judgment processing at the remaining time points2100(m+1)−n. For example, the level judging devices1101-110X implement the judgment processing at a time point for every eight time points in all the time points21001−n, thus dispensing with (thinning) the judgment processing at the remaining seven time points.

In this manner, the overall number of the level judgments is reduced so that the level judgments can be implemented without creating any problem caused by the throughput overload of the level judging devices1101-1103.

The operation of the level judging devices1101-110X is described further in detail. The level judging devices1101-110X, in response to the reception of the first and second level correction parameters S07and S08via the information communicating device2000, creates calculating coefficient address information S09based on the first and second level correction parameters S07and S08and transmits the information S09to the calculating coefficient memorizing device1400. The first and second level correction parameters S07and S08are inputted to the input device1600by the user of the audio processing apparatus1000and subsequently supplied to the information communicating device2000from the input device1600. The calculating coefficient address information S09is described as follows. The calculating coefficient memorizing device1400store substantive values of the reference data for the respective audio data. The calculating coefficient address information S09is the address information designating the storing positions of the reference audio data in the calculating coefficient memorizing device1400.

The calculating coefficient memorizing device1400, in response to the reception of the calculating coefficient address information S09, reads out substantive values of reference volume data S10addressed by means of the calculating coefficient address information S09from the entire substantive values of the memorized reference volume data and transmits the read-out substantive values to the level judging devices1101-110X.

The level judging devices1101-110X, in response to the reception of the substantive values of the reference volume data S10, retrieve the channel data respectively allocated to the level judging devices1101-110X from the received input audio data S06to compare the retrieved channel data with the substantive values of the reference volume data S10for judging which is larger or smaller than the other and transmits level judgment result signals S11representing the comparison results to the level correcting devices1201-120X. The level judgment result signals S11are transmitted to the level correcting devices1201-120X respectively corresponding to the level judging devices1101-110X.

The level correcting devices1201-120X, in response to the reception of the level judgment result signals S11, correct the inputted audio based on the judgment results and send out output audio data S15. At this point, a series of the level corrections implemented by the audio processing apparatus1000are completed.

FIG. 4is a view of a graphed relationship between the levels of the input audio data inputted to the audio processing apparatus1000and the levels of the corresponding output audio data. A graph G1shows the case of implementing no level corrections, and a graph G2shows an example of correction patterns in the case of implementing the level corrections.

The level correcting devices1201-1203, in the wake of receiving the level judgment result signals S11from the corresponding level judging devices1101-1103, decode the level judgment result signals S11to thereby judge whether the volume levels of the channel data corresponding to the level correcting devices1201-1203are larger or smaller than the substantive values of the reference volume data S10.

When the judgment results in “larger”, it is judged that the input audio level is within the range of a audio level region H2arranged on the left side inFIG. 4with respect to the reference volume data S10. The channel data is then corrected based on a correction pattern (correction property) suitable for the audio level region H2so that the level of the output audio data is reduced with respect to the level of the input audio data.

On the contrary, when the judgment results in “smaller”, it is judged that the input audio level is within the range of a audio level region H1arranged on the right side inFIG. 4with respect to the reference volume data S10. The channel data is then corrected based on a correction pattern (correction property) suitable for the audio level region H1so that the level of the output audio data is increased by a predetermined degree with respect to the level of the input audio data.

The operation of the level judging unit1100is described further in detail referring toFIG. 5. The respective level judging devices1101-1103of the level judging unit1100comprise level judgment channel designating portions1111. The level judgment channel designating portions1111receive level judgment channel information S05via the information communicating device2000. The level judgment channel information S05is the information inputted by the user of the audio processing apparatus to the information communicating device2000via the input device1600and serves to designate the channels subject to the level judgments in the input audio data S06.

The level judgment channel designating portions1111, based on the received level judgment channel information S05, designates the channels subject to the level judgments in the level judging devices1101-1103having the level judgment channel designating portions1111incorporated therein. The designated channels can be single or plural. For example, in the case of the audio data according to the Dolby Surround System, the level judgment channel designating portions1111may collectively handle the audio data from the right and left channels as a single audio data subject to the judgment. In such a case, the level judgment channel designating portions1111determine a pair of audio data (right and left) as the channel to be judged. As described, the respective channels are designated by the level judgment channel designating portions1111based on the level judgment channel information S05.

The level judging devices1101-1103read out one sample of the channel data of the channels designated by the level judgment channel designating portions1111from the input audio data S06, which is handled as level detection data. When a plurality of the channels is designated as the channels subject to the level judgments, for example, the maximum values thereof are selected. The substantive values of the reference volume data S10for judging the volume levels are stored in the calculating coefficient memorizing device1400as a coefficient table. The level judging devices1101-1103read out the substantive values of the reference volume data stored at the address positions in the calculating coefficient memorizing device1400determined based on the first and second level correction parameters S07and S08received from the input device1600via the information communicating device2000.

The first level correction parameter S07, as described earlier, determines the output level of the output audio data S15in the audio level region H1in the case of the input volume level being smaller than the reference volume data S10and corresponds to a correction pattern G21inFIG. 4. In the same manner, the second level correction parameter S08determines the output level of the output audio data S15in the audio level region H2in the case of the input volume level being larger than the reference volume data S10and corresponds to a correction pattern G22inFIG. 4.

The first and second level correction parameters S07and S08are created by the information communicating device2000based on correction-property information of the user's choice inputted to the input device1600by the user of the audio processing apparatus1000and supplied to the level judging devices1101-1103.

The correction pattern G21is defined according to the following formula (first linear expression).
Y=a1X+b1X: input audio data of audio processing apparatusY: output audio data of audio processing apparatusa1: amplification coefficient of input audio data X, for which a fixed value is provided. (a1=1, in the present embodiment)b1: value of first level correction parameter S07, subject to optional change by input device1600

As is clear from the foregoing formula, the first level correction parameter S07is a y piece in the correction pattern G21, more specifically, represents values added to or deducted from the input audio data S06in order to calculate the output audio data S15. The correction pattern G22is defined according to the following formula (second linear expression).
Y=a2X+b2X: input audio data of audio processing apparatusY: output audio data of audio processing apparatusa2: amplification coefficient of input audio data X, for which a fixed value is provided. (a2=1, in the present embodiment)b2: value of second level correction parameter S08, subject to optional change by input device1600

As is clear from the foregoing formula, the second level correction parameter S08is a y piece in the correction pattern G22, more specifically, represents values added to or deducted from the input audio data S06in order to calculate the output audio data S15.

The reference volume data S10indicates the volume level on the borderline between the adjacent audio level regions H1and H2and is obtained as X value (input audio data S06) at an intersecting point of the formulas for the correction patterns G21and G22.

When the correction patterns G21and G22are determined based on the settings of the first and second level correction parameters S07and s08, the reference volume data S10representing the intersecting point is uniquely determined. Therefore, the level judging devices1101-1103can specify the substantive values of the reference volume data S10in the calculating coefficient memorizing device1400using the first and second level correction parameters S07and S08.

FIG. 6is a table showing the borderline specifying data for specifying the reference volume data S10based on the correlation between the first and second level correction parameters S07and S08. The borderline specifying data of the reference volume data S10is comprised of step values, for which 22 steps, from a value “0” up to a value “21”, are set. The borderline specifying data is defined as an amount of displacement representing the displacement from the reference level 0 db toward −∞db. The value “0” is the value closest to the 0 db level, and the value “21” is the value closest to the −∞db. More specifically, the larger the borderline specifying data of the reference volume data S10is, the closer it is to the −∞db. The borderline specifying data of the reference volume data S10thus defined is referred to as a level correction offset.

The level correction offset does not represent the substantive values of the reference volume data S10stored in the calculating coefficient memorizing device1400. The substantive values of the reference volume data S10are arranged to correspond to the level correction offset and then stored in the calculating coefficient memorizing device1400.

The table shown inFIG. 6is based on the assumption that the following conditions are set.The levels of the adjustment with respect to the first level correction parameter S07implemented by the user to the input device1600are set in six steps, from 0-5.In response to the adjustment in one step with respect to the first level correction parameter S07implemented by the user to the input device1600, the substantive values of the level correction offset range within the triple step interval (3).The levels of the adjustment with respect to the second level correction parameter S08implemented by the user to the input device1600are set in seven steps, from 0-6.In response to the adjustment in one step with respect to the second level correction parameter S08implemented by the user to the input device1600, the substantive values of the level correction offset range within the identical step interval (1).

In the table ofFIG. 6created based on the foregoing conditions, the level correction offset obtains 42 values calculated from 6×7=42, based on the six-step adjustment levels with respect to the first level correction parameter S07and seven-step adjustment levels with respect to the second level correction parameter S08.

Further, in response to the one-step adjustment with respect the first level correction parameter S07implemented by the user to the input devices1600, the substantive values of the level correction offset range within the three-step interval. In contrast to that, in response to the one-step adjustment with respect the second level correction parameter S08implemented by the user to the input devices1600, the substantive values of the level correction offset range in the one-step interval.

As described, the 22 steps from the value “0” to the value “21” are set for the substantive values of the level correction offset. Apparent from the closer look at the table ofFIG. 6, many of the values overlap with one another in the 42 different level correction offset. Therefore, in the calculating coefficient memorizing device1400, there are 22 substantive values of the level correction offset in consequence of eliminating the overlapped values of the level correction offset, as shown inFIG. 7. There are 22 substantive values, D0-D21, of the reference volume data S10corresponding to the 22 substantive values of the level correction offset. The 22 substantive value data D0-D21of the reference volume data S10are sequentially stored in 22 memory regions of the calculating coefficient memorizing device1400.

The substantive value data D0-D21of the reference volume data S10are read out from the calculating coefficient memorizing device1400having the reduced data volume as described based on the first and second level correction parameters S07and S08as follows.

FIG. 8is a flow chart showing a reading-out step of the substantive values D0-D21of the reference volume data S10from the calculating coefficient memorizing device1400.

First, the information communicating device2000creates the first and second level correction parameters S07and S08based on the input values of the input device1600and outputs the parameters S07and S08. The level judgment channel designating portion1111acquires the first and second level correction parameters S07and S08outputted by the information communicating device2000(S801, S802).

Next, the acquired first and second level correction parameters S07and S08are applied to the following formula so that the level correction offset is calculated (S803).

A relative comparison C1between the first level correction parameters S07and S08represents a relative comparison between an output variation C2of the substantive values of the first level correction parameter S07relative to the input adjustment level with respect to the first level correction parameter S07and an output variation C3of the substantive values of the second level correction parameter S08relative to the input adjustment level with respect to the second level correction parameter S08, and, more specifically, is obtained according to the following formula.
C1=C2/C3

In the present embodiment, C1=3/1=3 is obtained.

Based on the level correction offset obtained in the S803, the level judging devices1101-1103read out the substantive value data D0-D21of the reference volume data S10from the calculating coefficient memorizing device1400.

More specifically, as shown in the following formula, the level correction offset is multiplied by a coefficient data size of the calculating coefficient memorizing device1400so that a coefficient read-out address offset is calculated (S804).

The coefficient read-out address offset refers to the offset showing an interval between a top address in the memory regions storing the substantive value data D0-D21of the reference volume data S10and an address position storing the current substantive data Dn (0≦n≦21) in the calculating coefficient memorizing device1400.

Next, the coefficient read-out address offset calculated in the S804is added to the top address of the calculating coefficient memorizing device1400. Thereby, the address of the memory region storing the substantive value data Dn of the reference volume data S10is specified in the calculating coefficient memorizing device1400(S805).

The addresses calculated in the S805constitute the calculating coefficient address information S09. The calculating coefficient address information S09is transmitted to the calculating coefficient memorizing device1400from the level judging devices1101-1103. In the calculating coefficient memorizing device1400, the substantive value data Dn of the reference volume data S10stored at the address represented by the calculating coefficient address information S09are read out and transmitted to the level judging devices1101-1103.

The level judging devices1101-1103compares the volume levels of the level detection data with the volume levels of the reference volume data S10and transmits the level judgment result signals S11representing the comparison results of the comparison, to the level correcting devices1201-1203.

As described, in the level judging devices1101-1103, the relationship between the overlapped step values of the reference volume data S10and the substantive value data D0-D21of the reference volume data S10is organized by means of the foregoing read-out step set as described. Therefore, the substantive value data D0-D21of the reference volume data S10can be stored without any overlapping in the calculating coefficient memorizing device1400. In this manner, a memory capacity required for the calculating coefficient memorizing device1400can be reduced, which leads to a cost reduction.

The operation of the level correcting devices1201-1203is described.FIG. 9shows a configuration of the level correcting devices1201-1203. The level correcting devices1201-1203comprise processing channel switching portions1210, channel processing designating portions1220, level correction initial value switching portions1230, level correction value calculating portions1240, and level correction smoothing portions1250.

The level correcting devices1201-1203receive, via the information communicating device2000, the first and second level correction parameters S07and S08, processing channel information S12, channel processing designation information S13, and level correction initial value information S14. The mentioned information, S07, S08, S12, S13, and S14are inputted to the input device1600by the user of the audio processing apparatus1000. The information, S12, S13, and S14are not shown inFIG. 2.

The processing channel switching portions1210determine the channels of the audio data to be respectively level-corrected by the level correcting devices1201-1203based on the received processing channel information S12.

The channel processing designating portions1220determine whether or not the level corrections are implemented to the channels, which the respective level correcting devices1201-1203are in charge of in implementing the level corrections. Whether or not the level corrections are implemented is determined based on the channel processing designation information S13received by the level correcting devices1201-1203via the information communicating device2000. The channel processing designation information S13is the data to be set and inputted to the audio processing apparatus1000by the user of the audio processing apparatus1000.

The level correction initial value switching portions1230determine level correction initial values of the level correcting devices1201-1203based on the level correction initial value information S14received via the information communicating device2000.

The level correction value calculating portions1240implement the following level corrections based on the level judgment result signals S11received from the corresponding level judging devices1101-110X. When the level judgment result signals S11show (input audio data S06>reference volume data S10), the level correcting devices1201-120X implement the processing reducing the output levels of the respective channel data, which the devices1201-120X are respectively responsible for, to be smaller than the input levels thereof in compliance with the correction pattern G22determined by the second level correction parameter S08. On he contrary, when the level judgment result signals S11show (input audio data S06<reference volume data S10), the level correcting devices1201-120X implement the processing increasing the output levels of the respective channel data, which the devices1201-120X are responsible for, to be larger than the input levels thereof in compliance with the correction pattern G21determined by the first level correction parameter S07. The channels to be respectively processed by the level correcting devices1201-120X are designated by the processing channel switching portions1210.

The level correction smoothing portions1250implement a smoothing processing between the level-corrected data outputted from the level correction value calculating portions1240and the data level-corrected at the time of the previous sampling. The level correction smoothing portions1250then output the smoothing-processed data as the output audio data S15at the time of the current sampling.

The details of the smoothing processing are described referring to the flow chart ofFIG. 10. The smoothing processing described below is basically implemented by the level correction smoothing portions1250unless stated otherwise.

After the current level correction calculation values are inputted from the level correction value calculating portions1240(S1001), the level correction initial value switching portions1230judge whether or not the inputted current level correction calculation values are the inputted data to be first processed (S1002).

When it is judged in the S1002that the inputted current level correction calculation values are not the inputted data to be first processed, the level correction initial value switching portions1230output the instruction that the previous smoothing-processed correction values sequentially updated and recorded in the level correction smoothing portions1250are used as the previous smoothing-processed correction values without change to the level correction smoothing portions1250.

On the contrary, when it is judged in the S1002that the inputted current level correction calculation values are the inputted data to be first processed, the level correction initial value switching portions1230output the instruction that the level correction initial values designated by the level correction initial value information S14in the level correction smoothing portions1250are used as the previous smoothing-processed correction values (S1003).

After the S1001-S1003described above are implemented in the level correction initial value switching portions1230, the level correction smoothing portions1250calculate the current smoothing-processed correction values according to the following formula (S1004).

After the current smoothing-processed correction values are calculated in the S1004, the level correction smoothing portions1250calculate the current corrected output volume levels (already smoothing-processed) in their relevant channel data to be corrected according to the following formula (S1005).

After the current corrected output volume levels (already smoothing-processed) in the relevant channel data to be corrected are calculated in the S1005, the level correction smoothing portions1250, in order to move on to the next correction processing, update and record the current smoothing-processed correction values as the previous smoothing-processed correction values (S1006). After the implementation of the so-far described, the current corrected output volume levels (already smoothing-processed) are outputted to outside from the level correction smoothing portions1250(S1007).

InFIG. 11, an effect of the smoothing processing implemented by the level correction smoothing portions1250is shown.FIG. 11shows correction outputs of the level correction calculating portions1240and smoothing outputs of the level correction smoothing portions1250at time points in chronological order in the sampling period2100of the audio processing apparatus1000. InFIG. 11, S051-3are sampling values of the input audio data at the time points21001-3. References1001-3are the before-mentioned correction outputs at the time points21001-3,1101-3are the before-mentioned smoothing outputs at the time points21001-3,1201-3are the level correction calculation values at the time points21001-3, and1301-3are the smoothing-processed correction values at the time points21001-3.

As is clear fromFIG. 11, the smoothing-processed correction values1302,3at the time points21002,3can be smaller or larger than the level correction calculation values1202,3at the identical time points21002,3, however, the smoothing outputs1102,3are smaller than the correction outputs1002,3in variation. The variation here means the variation of the smoothing outputs1102,3and the level correction calculation values1202,3with respect to the sampling values S052,3at the identical time points21002,3.

The smoothing processing thus implemented enables the outputted output audio data S15, in spite of the level corrections implemented thereto, to be more easily heard.

When it is decided in the channel processing designating portions1220that the level corrections are not implemented, the level correcting devices1201-1203do not implement the level corrections for their relevant channels, and the input audio data S06is outputted as the output audio data S15without change.

In the described S1002, when it is judged that the current level correction calculation values are the first data to be processed, the level correction initial values designated by the level correction initial value information S14are used as the previous smoothing-processed correction values.

The level correction initial values in the foregoing case are optionally set in the range between the maximum value of the volume level (=0 dB) and the minimum value of the volume level (=−∞db).

Followings are three examples of the level correction initial values.1 level correction calculation value first subject to the processing.2 level correction value when the volume level is at the maximum value (=OdB).3 level correction value when the volume level is at the minimum value (=−∞db).

In the case of 1, the previous smoothing-processed correction values first subject to the processing at the time point2100sin the sampling period are same as the level correction calculation values at the time point2100sin the sampling period. This results in (current level correction calculation value−previous level correction calculation value=0), and the current smoothing-processed correction values also result in 0. Because of that, the smoothing processing is not implemented, the corrected output audio levels (already smoothing-processed) at the time point2100sin the sampling period are identical to the corrected output audio levels. As a result, the implementation of the smoothing processing substantially starts at the second time point2100s+1in the sampling period.

In the case of 2, the previous smoothing-processed correction values first subject to the processing at the time point2100sin the sampling period are the level correction values when the volume levels are at the maximum value and, as shown inFIG. 4, are the smallest value of all the correction values. Therefore, the smoothing-processed correction values are increased as the time point in the sampling period2100chronologically transfers from2100sonward.

In the case of 3, the previous smoothing-processed correction values first subject to the processing at the time point2100sin the sampling period are the level correction values when the volume levels are at the minimum value and, as shown inFIG. 4, are the largest value of all the correction values. Therefore, the smoothing-processed correction values are decreased as the time point2100in the sampling period chronologically transfers from2100sonward.

For example, when the volume levels at the top of the input audio data S06are small, to set the correction initial values at the maximum makes the audio at the top more listenable. When the volume levels at the top of the input audio data S06are large, to set the correction initial values at the minimum or original volume levels can prevent unnecessary clipping. Thus, the correction initial values can be selectively changed in accordance with the volume levels of the input audio data S06or the users' preferences.

In the audio processing apparatus1000, the throughput is reduced by thinning the judgment processing implemented by the level judging unit1100so that the judgments can be processed without causing any problem, including the case of implementing the level corrections to the multi-channel audio data.

Further, in the audio processing apparatus1000, a plurality of the level judging devices1101-1103are provided so that the channels not quite correlated with one another can be selectively level-judged by the level judging devices1101-1103. In this manner, a variety of optional settings are available depending on the kinds of the inputted audio data, the environment where the audio data is heard or watched, the users' preferences, and the like, which enables responding to different situations and requests.

Further, a plurality of the level correcting devices1201-1203are provided in the audio processing apparatus1000, a variety of the level corrections can be optionally set depending on the kinds of the inputted audio data, the environment where the audio data is heard or watched, the users' preferences, and the like, which enables responding to different situations and requests.

Further, when the decoder information is used in order to determine how often the multi-channel audio data is thinned, the level corrections can be implemented at an optimum thinning frequency depending on the forms of the audio data.

Further, the level judging devices1101-1103comprise the level judgment channel designating portions1111, and the level correcting devices1201-1203comprise the channel processing designating portions1220. This configuration can provide optional settings, that are, which channel is level-judged by which level judging devices1101-1103and also level-corrected by which level correcting devices1201-1203(which correction graph is used for the correction). Therefore, an optimum audio processing responding to the users' preferences and the kinds of the audio data can be implemented.

For example, taking the 5.1 ch Dolby Digital as an example, LFE (Low Frequency Effect) using right, left and front channels can be level-corrected.

Further, the level correcting devices1201-1203comprise the processing channel switching portions1210to thereby determine whether or not the level corrections with respect to the optional channels are implemented. In this manner, settings can be optionally changed depending on the kinds of the inputted audio data, the environment where the audio data is heard or watched, the users' preferences, and the like. Different situations and requests can be thereby successfully handled.

Further, the level correcting devices1201-1203comprise the level correction initial value switching portions1230so that the level correction initial values can be optionally set. The level correction initial values influence the correction level of the audio data at the initial stage. For example, some users prefer not to implement the corrections at the initial stage, while some users do prefer to implement the corrections at the initial stage to make the volume level larger because the volume level is small at the initial stage in most cases. In addition, the level correction initial values should be set at subtly different values depending on the different properties of the sound sources. Further, with the level correction initial value switching portions1230provided, the level correction initial values can be optionally set in accordance with the volume levels of the initial data of the input audio data and the users' preferences.

In the Embodiment 1, it is unnecessary to provide all of the level judgment channel designating portions1111, processing channel switching portions1210, channel processing designating portions1220, level correction initial value switching portions1230. For example, when the level correction initial values can be fixed, the level correction initial value switching portions1230are not necessary. It is unnecessary either to provide both the processing channel switching portions1210and channel processing designating portions1220.FIG. 12shows a structure not comprising the level correction initial value switching portions1230and channel processing designating portions1220.

Further, it is not always necessary to provide a plurality of the level correcting devices1201-1203in the level correcting unit1200. The level correcting unit1200can include a single level correcting device.

In the case of providing a single level correcting device, the level corrections are implemented according to a kind of the correction pattern. However, it still can be judged whether or not the volume levels of the audio data are larger or smaller than the reference volume data S10per channel. Therefore, more options are available for the audio processing compared to the conventional technology.FIG. 13shows a structure having a single level correcting device.

Further, in the Embodiment 1, the audio data for all the channels are inputted to the respective level judging devices1101-1103, and the channels to be level-judged are designated by the level judgment channel designating portions1111. However, it is unnecessary to input all the channel data of the input audio data S06to all the level judging devices1101-1103. For example, when the audio data having six channel data is inputted, the following arrangements are possible.A first channel data alone is exclusively supplied to the level judging device1101.Second to fifth channel data alone is exclusively supplied to the level judging device1102, and the channel data subject to the level judgments is designated by the level judgment channel designating portion1111.All the channel data is supplied to the level judging device1103, and the channel data subject to the level judgments is designated by the level judgment channel designating portion1111.

In the foregoing case, the level judging device1101is exclusively used for the first channel data only, therefore it is unnecessary to provide the level judgment channel designating portion1111. This configuration can be applied to the level correcting devices1201-1203as well.

FIG. 14a view illustrating a configuration of a audio processing apparatus3000according to Embodiment 2 of the present invention. The audio processing apparatus3000is different to the audio processing apparatus according to the Embodiment 1 in that the level judgment thinning controller1300comprises a per-simultaneous-implementation-function level judgment thinning controller switching device1320, not the per-decoder level judgment thinning controller switching device1310. The per-simultaneous-implementation-function level judgment thinning controller switching device1320, based on simultaneous implementation function information S16created inside the audio processing apparatus3000and received via the information communicating device2000, determines intervals for implementing the level judgments by the level judging devices1101-1103. For example, it is assumed that the audio processing apparatus3000comprise a function of implementing a processing1(virtual sound creating processing), a processing2(output band expansion processing), and a processing3(equalizer processing) simultaneously with the described level corrections according to the present invention. In such a case, as shown inFIG. 15, the per-simultaneous-implementation-function level judgment thinning controller switching device1320judges if there is any other processing to be implemented simultaneously with the correction processing according to the present invention and determines the intervals for implementing the level judgments by the level judging devices1101-1103in accordance with loads applied to the audio processing apparatus3000by any simultaneously-implemented processing. Taking the case shown inFIG. 15as an example, when none of the processings1-3is implemented simultaneously with the corrections according to the present invention, the frequency of implementing the judgments (thinning intervals) is set at two sampling periods. On the contrary, when all of the processings1-3are implemented simultaneously with the corrections according to the present invention, the frequency of implementing the judgments (thinning intervals) is set at 32 sampling periods.

When a large number of the processings are simultaneously implemented, the processings are thinned more often, and when a small number of the functions are simultaneously implemented, thinning is conducted at a reduced frequency. In this manner, an overall throughput is realized at an optimum level.

FIG. 16is a view illustrating a configuration of a audio processing apparatus4000according to Embodiment 3 of the present invention.

The audio processing apparatus4000further comprises a level judgment sample designating device1700in addition to the structures of the described audio processing apparatuses1000and3000. The level judgment sample designating device1700generates pseudorandom numbers for designating thinning positions in the judgment thinning control implemented by the level judgment thinning controller1300and supplies the pseudorandom numbers to the level judgment thinning controller1300. The level judgment thinning controller1300, based on the pseudorandom numbers supplied by the level judgment sample designating device1700, sets the thinning positions in the judgment thinning control, which are, in other words, allocation positions of the audio data samples subject to the judgments within a predetermined period.

In the audio processing apparatus4000, phases of the audio data samples subject to the level judgments can be varied.

When the described thinning processing according to the present invention is implemented with respect to the samples subject to the judgments, the following judgment errors possibly occur. When the thinning processing is implemented in such manner that frequencies based on the allocation positions of the samples to be thinned(thinning frequencies) and sample frequencies of the input audio data S05and S06of the audio processing apparatuses1000and1300are integral multiples relative to one another, the positions of the audio data subject to the judgments are fixed in the case of the input audio data S05and S06being standing wave such as sinusoidal wave, thereby causing the judgments implemented by the level judging unit1100to generate errors.

In response to the problem, the audio processing apparatus4000is capable of varying the phases of the audio data samples subject to the level judgments, thereby reducing the judgment errors to the minimum.

As thus far described, the audio processing apparatus according to the present invention can reduce the throughput and implement the volume level corrections of the audio data including the multi-channel audio data, without down-mixing the multi-channel audio data into the two-channel audio data and thus maintaining the original number of the channels.

Further, methods of the level judgments, reference values, degrees of the level corrections, and the like can be changed in response to the kinds of the inputted audio data and users' preferences.

While there has been described what is at present considered to be preferred embodiments of this invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of this invention.