JP2013172441A - Time difference correction method, audio signal processing apparatus, reproduction apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the time difference occurring between a signal of a main channel and a signal of an LFE channel, during production of a surround content, appropriately.SOLUTION: The time difference correction method for correcting the time difference between a main channel and an LFE channel, during production of a surround content, comprises: a time difference calculation step of calculating the time difference (amount of delay) of a signal in an LFE channel for a signal in a main channel, in a partial section of a surround content (S17); a correlation determination step of determining correlation of the signal in a main channel and the signal in an LFE channel (S18); and a time difference correction step of correcting the time difference calculated by the time difference calculation step (S22). The time difference correction step corrects the time difference only when a determination is made (S18: Yes)that there is correlation by the correlation determination step.

Description

  The present invention relates to a time difference correction method, an audio signal processing device, a playback device, and a program for correcting a time difference between a main channel and a bass sound effect channel.

  Conventionally, in a multi-channel surround playback apparatus that performs multi-channel playback using a plurality of speakers, an LFE (Low Frequency Effect) channel signal is lower than other channel (main channel) signals. A technique of generating using a pass filter is known. However, in this method, when a low-frequency component is extracted using a low-pass filter, the LFE channel signal is delayed. For this reason, for example, in Patent Document 1, correction processing is performed to correct the time difference (phase difference) between the main channel signal and the LFE channel signal. By this correction processing, the group delay characteristic obtained when the main channel and the LFE channel are synthesized is flattened, and the dullness of the bass and the lack of expression of the low music instrument are improved.

  By the way, a technique for creating a bass sound effect that is output from a main channel signal by a bass sound effect speaker during the production of surround content (music content) provided by package media such as DVD or Internet distribution is known. . Also in this case, since a low-frequency component is extracted from the main channel signal using a low-pass filter, a delay occurs in the LFE channel signal. On the other hand, for example, in Patent Document 2, a bass sound effect is appropriately output by correcting the time difference according to the characteristics of the low-pass filter at the time of producing the surround content.

JP 2002-369300 A JP 2005-027163 A

  However, in Patent Documents 1 and 2, the extraction of the low-frequency component using the low-pass filter and the correction of the time difference of the signal generated thereby are completed in the same system, so the time difference to be corrected is It can be easily obtained from the characteristics of a known low-pass filter. However, when surround content (contents with bass shifts) such as Patent Document 2 that has not been subjected to time difference correction is played back by a playback device, the characteristics of the low-pass filter used at the time of production are unknown. Therefore, it is difficult to correct the time difference. That is, even if the reproduction apparatus of Patent Document 1 is used, accurate time difference correction cannot be performed.

  Also, the main channel signal and the LFE channel signal are not always correlated. For example, there are cases where the main channel and the LFE channel are uncorrelated, such as movie and drama content. In this case, the time difference correction process itself is meaningless. In the case of music content, if the time difference is corrected unnecessarily despite the low correlation, the sound quality may be impaired.

  In view of the above problems, the present invention provides a time difference correction method capable of appropriately correcting a time difference between a main channel signal and a LFE channel signal in surround content (a time difference that occurs during surround content production) on the playback device side. An object is to provide an audio signal processing device, a playback device, and a program.

  The time difference correction method of the present invention is a time difference correction method for correcting a time difference between a main channel and a bass sound effect channel that occurs during the production of surround content, and a main channel signal and a bass sound effect in a partial section of the surround content. A signal acquisition step for acquiring a channel signal, a correlation determination step for determining the presence or absence of correlation between the main channel signal and the bass sound effect channel signal, and the time difference between the main channel signal and the bass sound effect channel signal is calculated. And a time difference correction step for correcting the time difference calculated by the time difference calculation step. The time difference correction step corrects the time difference only when the correlation determination step determines that the correlation is “present”. It is characterized by.

  The audio signal processing apparatus of the present invention is an audio signal processing apparatus that corrects a time difference between a main channel and a bass sound effect channel that occurs during the production of surround content, and is a main channel signal and bass in a partial section of the surround content. A signal acquisition means for acquiring a sound effect channel signal; a correlation determination means for determining the presence or absence of correlation between the main channel signal and the bass sound effect channel signal; and the time difference between the main channel signal and the bass sound effect channel signal. A time difference calculating means for calculating the time difference and a time difference correcting means for correcting the time difference calculated by the time difference calculating means. The time difference correcting means corrects the time difference only when the correlation determining step determines that the correlation is “present”. It is characterized by doing.

According to these configurations, since the time difference between the signal of the main channel and the signal of the bass sound effect channel is calculated, even if the content has a low-frequency component generated using an unknown low-pass filter, the time difference is calculated. It can be corrected. In other words, the bass shift at the time of content production can be corrected on the playback device side. Further, since it is determined whether or not there is a correlation between the main channel signal and the bass sound effect channel signal, and the correlation is determined to be “Yes”, the time difference is corrected, so that appropriate time difference correction can be performed. For example, in the case of content that has no correlation between the main channel and the bass sound effect channel, such as a movie / drama, the useless time difference correction process can be omitted. Also, in the case of music content, if it is determined that the correlation is “none”, the reliability of the time difference calculation result itself is low, and therefore it is possible to prevent deterioration in sound quality by not performing time difference correction.
Note that when surround content signals are acquired, it is determined whether or not there is a low-frequency component in both the main channel and the bass sound effect channel, and each step is executed only when it exists (each unit functions). Also good.
In addition, it is possible to determine the content type based on metadata such as genre information when acquiring the surround content signal, and to execute each step only for specific content (music content). According to these configurations, useless processing (time difference calculation and correlation determination processing) for content that has no correlation between the main channel and the bass sound effect channel such as a movie / drama can be omitted. If the beginning of the content can be determined, each step may be omitted for the entire content determined not to be the specific content.

  In the time difference correction method described above, the signal acquisition step, the correlation determination step, the time difference calculation step, and the time difference correction step are repeatedly executed every predetermined time, and the time difference correction step is determined as “no” correlation by the correlation determination step. The time difference calculated last time is maintained.

  According to this configuration, even when the beginning of content (music) cannot be determined, time difference correction can be performed without being aware of when the content is switched. In particular, this configuration is useful when the present configuration is applied to an apparatus that cannot perform playback control in units of music, such as an AV receiver.

  In the above time difference correction method, the polarity determination step for determining the polarity of the bass sound effect channel with respect to the signal of the main channel, and the polarity of the signal of the main channel or the signal of the bass sound effect channel according to the determination result of the polarity determination step And a polarity correcting step for correcting.

  According to this configuration, since not only the time difference between the main channel signal and the bass sound effect channel but also the polarity is corrected, in the case where the polarity of the bass sound effect channel signal is inverted with respect to the main channel signal, More accurate time difference correction can be performed. Thereby, the interference between signals can be suppressed to the minimum, and a bass with a strong attack can be obtained. In addition, stabilization of the low sound improves the overall sound quality balance including the high sound.

  In the time difference correction method described above, a pre-filter application step for extracting a low-frequency component by applying a pre-filter from the main channel signal is further executed. In the correlation determination step, after the pre-filter application step, the main channel signal is extracted. And the presence / absence of correlation between the signals of the bass sound effect channel and the bass sound effect channel signal.

  According to this configuration, by applying the pre-filter, it is possible to determine the presence or absence of correlation for only the low frequency component, so that a more accurate determination result can be expected.

  In the time difference correction method, the prefilter applying step is characterized in that a prefilter similar to the prefilter applied to the main channel signal is applied to the bass sound effect channel signal.

  When the pre-filter is applied to only one of the main channels, a delay due to the pre-filter characteristic occurs only in the main channel signal, and a time difference occurs between the low-frequency sound effect channel signal. According to this configuration, since the prefilter is also applied to the bass sound effect channel, such a problem can be solved.

  In the above time difference correction method, after the pre-filter application step, a normalization step for normalizing the signal amplitude of the main channel and the bass sound effect channel is further executed. In the correlation determination step, after the normalization step, the main channel It is characterized by determining the presence or absence of correlation between the signal of the above and the signal of the bass sound effect channel.

  According to this configuration, since the signal amplitudes of the main channel and the bass sound effect channel vary depending on the content, the presence or absence of correlation can be accurately determined by performing normalization regardless of the content.

  In the time difference correction method, the signal acquisition step is characterized in that a section in which the audio characteristics of the surround content are characteristic is extracted as a partial section.

  According to this configuration, it is possible to perform more appropriate time difference correction by executing each step on a characteristic section such as a section where the volume is high, a specific instrument sound generation section, and an attack sound generation section. Can do.

  A playback apparatus according to the present invention includes each unit in the audio signal processing apparatus described above, and plays back the surround content after the time difference correction by the time difference correction unit.

  A program according to the present invention causes a computer to execute each step in the time difference correction method.

  By using these playback devices and programs, the playback device can appropriately correct the time difference between the main channel signal and the LFE channel signal generated during the production of the surround content.

It is a figure which shows the structure of the reproducing | regenerating apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of an audio | voice signal processing circuit. (A) is a figure which shows the structure of a LFE polarity / delay analysis part, (b) is a figure which shows the structure of a correlation evaluation part. (A) is a figure which shows a correlation function, (b) is explanatory drawing of a correlation determination. (A)-(c) is a figure which shows the calculation process of a correlation function. It is a flowchart which shows the flow of a delay amount automatic correction process. FIG. 7 is a flowchart of a subroutine of FIG. 6 showing a flow of LFE polarity / delay analysis processing. (A) is a figure which shows the calculation formula of the sum of squares of differences, (b) is explanatory drawing of correlation determination, (c) is explanatory drawing of polarity determination and delay amount calculation.

  Hereinafter, a time difference correction method, an audio signal processing device, a playback device, and a program according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied to a 5.1 channel multi-channel surround AV receiver will be described.

  FIG. 1 is a diagram showing a configuration of a playback apparatus 1 assuming an AV receiver. The playback device 1 includes an audio signal processing circuit 2, a D / A converter 3, an amplifier 4, and a speaker 5. The audio data of the surround content serving as a sound source is converted into a digital audio signal by the audio signal processing circuit 2, and various signal processing is performed. Thereafter, the D / A converter 3 generates an analog audio signal, which is input to the amplifier 4 and emitted from the speaker 5. The “audio signal processing device” in the claims corresponds to the audio signal processing circuit 2.

  The speaker 5 includes a front left speaker 5L installed on the front left side of the listener, a front right speaker 5R installed on the front right side, a center speaker 5C installed on the front side, a surround left speaker 5SL installed on the rear left side, and a rear side. The surround right speaker 5SR installed on the right side and the bass sound effect speaker 5LFE for reproducing a low frequency component which is a bass sound effect are composed of six. Also, six D / A converters 3 and four amplifiers 4 are provided corresponding to each speaker 5. Note that the configuration of the playback device 1 is not limited to 5.1 channels, but may be 6.1 channels, 7.1 channels, or the like.

  Next, the configuration of the audio signal processing circuit 2 will be described with reference to FIG. The audio signal processing circuit 2 includes an audio decoder 21, an adder 22, an LFE polarity / delay analyzer 23, an LFE delay corrector 24, an LFE polarity corrector 25, and a system controller 26.

  The voice decoding unit 21 decodes the voice data. Thereby, multi-channel digital audio (L channel signal, R channel signal, C channel signal, SL channel signal, SR channel signal, LFE channel signal) is obtained. These six types of signals correspond to six D / A converters 3, amplifiers 4 and speakers 5, respectively. Note that the LFE channel is a bass sound effect channel (a channel dedicated to the ultra low frequency range). Further, the five channels other than the LFE channel are collectively referred to as main channels.

  The adder 22 adds each channel (L channel signal, R channel signal, C channel signal, SL channel signal, SR channel signal) of the main channel.

  The LFE polarity / delay analysis unit 23 analyzes the polarity of the LFE channel signal and the delay amount (time difference) with respect to the main channel signal under the control of the system controller 26. The addition result of the main channel by the adder 22 and the signal of the LFE channel are input to the LFE polarity / delay analyzer 23. Also, the analysis result of the LFE polarity / delay analysis unit 23 is notified to the system controller 26.

  The LFE delay correction unit 24 performs a delay process on the main channel signal. The delay amount of the delay process is controlled by the system controller 26 and becomes the same value for all channels. The LFE polarity correction unit 25 performs polarity inversion processing on the LFE channel signal. ON / OFF of the polarity inversion process is controlled by the system controller 26.

  The system controller 26 instructs the LFE polarity / delay analysis unit 23 to start analysis processing at regular time intervals (for example, every several tens of seconds). After that, when the system controller 26 detects that the analysis is completed, the system controller 26 displays the analysis result as an LFE delay. This is reflected in the correction unit 24 and the LFE polarity correction unit 25.

  Next, the configuration of the LFE polarity / delay analysis unit 23 will be described in more detail with reference to FIG. As shown in FIG. 3A, the LFE polarity / delay analysis unit 23 includes a buffer input control unit 71 (signal acquisition unit), a buffer 72, and a correlation evaluation unit 73.

  The buffer input control unit 71 repeatedly acquires the main channel signal and the LFE channel signal in a partial section of the surround content. Specifically, in response to an analysis start instruction from the system controller 26, the signal path switch (not shown) of the buffer input control unit 71 changes from OFF to ON, and the main channel (signal addition result of each channel) and the LFE channel are changed. The signals are taken into the respective buffers 72a and 72b for a predetermined time. The buffer 72a is a main channel buffer, and the buffer 72b is an LFE channel buffer. The signal path switch of the buffer input control unit 71 changes from ON to OFF at the time when the buffer capture of each signal is completed. Thereafter, the correlation evaluation unit 73 analyzes the correlation between the signal in the buffer 72a and the signal in the buffer 72b, and the polarity (normal phase / reverse phase) and the delay amount of the signal of the LFE channel with respect to the signal of the main channel are determined. The system controller 26 is notified of the analysis result.

  As shown in FIG. 3B, the correlation evaluation unit 73 includes a pre-filter application unit 81, a normalization unit 82, a time difference calculation unit 83, a correlation determination unit 84, and a polarity determination unit 85.

  The prefilter application unit 81 extracts a low-frequency component from the main channel signal including the high-frequency component by a pre-filter so that the correlation evaluation can be performed on only the low-frequency component. The prefilter used here is a low-pass filter. However, if the pre-filter is applied to only one of the main channels, a delay due to the pre-filter characteristics occurs only in the main channel, and a time difference is generated between the signal of the LFE channel and no high frequency component is included. A similar pre-filter is applied to the LFE channel.

  The normalization unit 82 normalizes the signal amplitude of the main channel signal and the LFE channel signal so that the maximum amplitude of the absolute value of the signal is 1. This is because the signal amplitudes of the main channel and the LFE channel are not constant depending on the content. By normalizing in this way, the calculation result of the correlation function can be evaluated with a constant numerical value (threshold value) regardless of the content.

  The time difference calculation unit 83 calculates the delay amount (time difference) of the LFE channel signal with respect to the main channel signal, using a correlation function (see FIG. 4A). The correlation determination unit 84 also determines the presence or absence of correlation between the main channel signal and the LFE channel signal using the correlation function. Further, the polarity determination unit 85 also determines the polarity of the LFE channel with respect to the main channel signal using the correlation function.

  Here, the calculation of the correlation function will be described with reference to FIGS. FIG. 4A shows a correlation function. In the figure, R (m) takes a value in the range from −1 to 1. R (m) takes a positive value if the correlation between the main channel signal x (n) and the LFE channel signal y (n) is positive, and is negative if the correlation is negative. Takes a value. R (m) takes a value close to 1 if the correlation is strong, and takes a value close to 0 if the correlation is weak. Thereby, the presence or absence of correlation is determined.

Furthermore, the nature of the correlation function R (m), the absolute value of R (m) | R (m ) | a m which is the maximum and m _MAX, when the value of the time and R (m _MAX), the main channel The delay amount of the signal y (n) of the LFE channel with respect to the signal x (n) is represented by m _MAX . Thereby, the delay amount (time difference) is calculated.

Furthermore, the nature of the correlation function R (m), the polarity of the signal LFE channels for signal x (n) of the main channel y (n) (positive phase / reversed phase), the sign of R (m _MAX) (+ / -) Thereby, polarity is determined.

Further, when the correlation between the main channel signal and the LFE channel signal is weak, the reliability of the analysis result is low. Therefore, as shown in FIG. 4 (b), the threshold TH _R for determining the presence or absence of the correlation provided, | R (m _MAX) | is determined to "correlation exists" equal to or more than TH _R, | R If (m _MAX ) | is smaller than TH _R , it is determined that there is no correlation. If it is determined that there is “correlation”, the analysis result of the correlation evaluation unit 73 is “success”, and if it is determined that “no correlation”, the analysis result of the correlation evaluation unit 73 is “failure”.

FIG. 5 is a diagram showing a correlation function calculation process. As shown in FIGS. 9A to 9C, the corresponding section (section) of the LFE channel with respect to the main channel is set so that the waveforms of the main channel signal and the LFE channel signal most closely match (so that the correlation becomes strong). X) is determined while gradually shifting. In the example shown in the figure, the delay amount m _MAX is obtained from the corresponding result of (b) in which the waveforms match most.

  Next, the flow of the delay amount automatic correction process will be described with reference to FIGS. The playback device 1 repeatedly executes the flowchart shown in FIG. 6 at predetermined time intervals. First, it is determined whether or not audio data is input (S01). If not input (S01: No), the process is terminated. If audio data is input (S01: Yes), it is determined whether or not the LFE channel is recorded in the surround content (S02). If not (S02: No), the process is performed. finish. If it is recorded (S02: Yes), the LFE polarity / delay analysis process (see FIG. 7) is performed (S03).

  Thereafter, it is determined whether or not the analysis result of the LFE polarity / delay analysis process is “success” (S04). If it is “success” (S04: Yes), the polarity of the LFE polarity correction unit 25 is updated (S05). Further, the delay amount of the LFE delay correction unit 24 is updated (S06). On the other hand, when the analysis of the LFE polarity / delay analysis process is “failure” (S04: No), the process ends. For example, when the correlation between the main channel signal and the LFE channel signal is weak, the analysis result is “failure”. In this case, S05 and S06 are omitted, and the previously calculated polarity and delay amount are maintained.

  FIG. 7 is a flowchart showing the flow of the LFE polarity / delay analysis process (S03 in FIG. 6). In the LFE polarity / delay analysis process, signals are first taken into the buffers 72a and 72b (S11), and it is determined whether or not a low frequency component exists in both the main channel and the LFE channel (S12). If there is no low frequency component in both (S12: No), the analysis result is set to “failure” (S13), and the LFE polarity / delay analysis process is terminated.

If both low-frequency components exist (S12: Yes), the pre-filter is applied to extract the low-frequency components from the main channel signal (S14), and the signal amplitude is normalized (S15). Thereafter, the correlation function R (m) is calculated (S16), and the delay amount m _MAX is searched (S17). Moreover, | R (m _MAX) | is determined whether the correlation depending on whether or not more than TH _R (S18), TH if _R is smaller than (S18: No), the analysis because of no correlation "Failure (S13).

Moreover, | R (m _MAX) | is (case with correlation) is equal to or greater than TH _R is (S18: Yes), R ( m MAX) , it is determined whether or not a positive value (S19), positive If it is a value (S19: Yes), the polarity of the LFE channel is set to the positive phase (S20). Conversely, if it is 0 or less (negative value) (S19: No), the polarity of the LFE channel is set to the opposite phase (S21). When the polarity is updated (S20, S21), the LFE delay amount is further updated to m _MAX obtained in S17 (S22), the analysis result is set to “success” (S23), and the LFE polarity / delay analysis process is terminated. .

  As described above, according to the present embodiment, in order to calculate the delay amount of the LFE channel signal with respect to the main channel signal, the content in which the low-frequency component is generated using the unknown low-pass filter at the time of content production Even so, the amount of delay can be corrected on the playback device 1 side. Since not only the delay amount but also the polarity is corrected, more accurate delay amount correction can be performed when the polarity of the bass sound effect channel signal is inverted with respect to the main channel signal. Thereby, the interference between signals can be suppressed to the minimum, and a bass with a strong attack can be obtained. In addition, stabilization of the low sound improves the overall sound quality balance including the high sound. Further, since the polarity correction unit is provided on the LFE channel side (LFE polarity correction unit 25, see FIG. 2), the processing amount required for the polarity correction process can be reduced as compared with the case where it is provided on the main channel side.

  In addition, the presence or absence of correlation between the main channel signal and the LFE channel signal is determined, and the delay amount is corrected only when the correlation is determined to be present. Therefore, appropriate delay amount correction can be performed. For example, in the case of content that has no correlation between the main channel and the bass sound effect channel, such as a movie / drama, the useless delay amount correction processing can be omitted. Also, in the case of music content, when it is determined that the correlation is “none”, the reliability of the delay amount calculation result itself is low, and therefore it is possible to prevent deterioration in sound quality by not performing delay amount correction.

  In addition, since the delay amount correction is repeatedly executed every predetermined time, even in an AV receiver that cannot determine the beginning of the content (music piece), the accurate delay amount correction is performed without being aware of when the content is switched. be able to.

  In addition, since pre-filtering is applied to both the main channel and the LFE channel as pre-processing for correlation determination, it is possible to determine the presence or absence of more accurate correlation only for low-frequency components while preventing delays due to pre-filter characteristics. it can. Further, by performing normalization thereafter, the presence or absence of correlation can be determined more accurately regardless of the signal amplitude of the content.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the correlation function is used, but in this embodiment, the sum of squared differences is used. Only differences from the first embodiment will be described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Moreover, the modification applied about the component similar to 1st Embodiment is applied similarly about this embodiment.

FIG. 8A is a diagram illustrating a calculation formula for the sum of squared differences. When using the sum of squares of differences, first, the sum of squares of differences when the main channel signal and the LFE channel signal are in a positive phase relationship is obtained by the calculation formula (1). In the calculation formula (1), S _pos (m) is always a positive value, and is 0 when it completely matches. Further, m is _calculated when S _pos (m) is minimum, and is set to m _{MIN_pos} .

Subsequently, the sum of squares of differences in the case where the main channel signal and the LFE channel signal are in a reverse phase relationship is obtained by the calculation formula (2). That is, the sum of squared differences between the main channel signal and the “LFE channel signal with reversed polarity” is obtained. In the calculation formula (2), S _neg (m) is always a positive value, and is 0 when it completely matches. In addition, m when S _neg (m) is minimized is determined as m _{MIN — neg} .

Subsequently, as shown in FIG. 8B, the presence or absence of correlation is determined using the results of the calculation formulas (1) and (2). That is, if any one of S _pos (m _{MIN — pos} ) and S _neg (m _{MIN — neg} ) is less than or equal to the threshold value TH _S , it is determined that “correlation exists”. Further, if both S _pos (m _{MIN — pos} ) and S _neg (m _{MIN — neg} ) are larger than the threshold value TH _S, it is determined that “no correlation”.

Further, as shown in FIG. 8C, the polarity is determined and the delay amount is calculated. That is, when S _pos (m _{MIN — pos} ) is equal to or less than S _neg (m _{MIN — neg} ), the polarity of the LFE channel signal is determined to be positive and the delay amount is set to m _{MIN — pos} . If S _pos (m _{MIN — pos} ) is larger than S _neg (m _{MIN — neg} ), the polarity of the LFE channel signal is determined to be in reverse phase, and the delay amount is set to m _{MIN — neg} .

  As described above, the presence / absence determination of the correlation, the determination of the polarity, and the calculation of the delay amount can be performed using not only the correlation function shown in the first embodiment but also the sum of squared differences.

  In the first embodiment and the second embodiment described above, both the polarity determination and the delay amount calculation are performed. However, only the delay amount may be calculated. That is, polarity determination may be omitted. According to this configuration, although it is not possible to completely correct content in which only the polarity of the signal is inverted without delay, the amount of calculation can be reduced. For example, the calculation of the calculation formula (2) (see FIG. 8A) and the final polarity determination (see FIG. 8C) when using the sum of squared differences can be omitted.

  In each of the above embodiments, the polarity correction unit (LFE polarity correction unit 25) is provided on the LFE channel side (see FIG. 2), but the polarity correction unit may be provided on the main channel side. In this case, polarity correction processing is performed for the five channels of L channel, R channel, C channel, SL channel, and SR channel. In this case, the polarity correction unit may be performed before or after the delay correction by the LFE delay correction unit 24.

  In each of the above embodiments, in the delay amount automatic correction process (see FIG. 6), when the LFE channel is recorded in the content, the LFE polarity / delay analysis process (see FIG. 7) is performed. Further, it is determined whether or not the audio characteristic of the content is characteristic, and the LFE polarity / delay analysis process may be performed only when it is determined as characteristic. That is, the LFE polarity / delay analysis process may be performed only in a section having a characteristic voice characteristic. Whether or not the sound characteristic is characteristic is determined based on, for example, the volume, the presence or absence of a specific instrument sound, the presence or absence of an attack sound, and the like. According to this configuration, the delay amount can be efficiently corrected by performing the LFE polarity / delay analysis process only on the characteristic section of the content.

  Moreover, it is possible to provide each component of the reproducing | regenerating apparatus 1 shown above as a program. Further, the program can be provided by being stored in various recording media (CD-ROM, flash memory, etc.). That is, a program for causing a computer to function as each component of the playback apparatus 1 and a recording medium on which the program is recorded are also included in the scope of the right of the present invention.

  In the above embodiment, the playback apparatus 1 is applied to an AV receiver. However, the playback apparatus 1 may be applied to other audio equipment such as a digital broadcast tuner and a BD / DVD disc player. Also, when playback control is possible in units of music, such as a BD / DVD disc player (when the beginning of the music can be identified), automatic delay amount correction processing (see FIG. 6) is performed only once at the beginning of the music. You may do it. Other modifications can be made as appropriate without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Playback apparatus 2 ... Audio | voice signal processing circuit 3 ... D / A converter 4 ... Amplifier 5 ... Speaker 21 ... Speech decoding part 22 ... Addition part 23 ... LFE polarity / delay analysis part 24 ... LFE delay correction part 25 ... LFE Polarity correction unit 26 ... System controller 71 ... Buffer input control unit 72 ... Buffer 72a ... Main channel buffer 72b ... LFE channel buffer 73 ... Correlation evaluation unit 81 ... Prefilter application unit 82 ... Normalization unit 83 ... Time difference calculation unit 84 ... Correlation determination unit 85 ... polarity determination unit

Claims (10)

A time difference correction method that corrects a time difference between a main channel and a bass sound effect channel that occurred during the production of surround content,
A signal acquisition step of acquiring a signal of the main channel and a signal of the bass sound effect channel in a partial section of the surround content;
A correlation determination step for determining the presence or absence of correlation between the signal of the main channel and the signal of the bass sound effect channel;
A time difference calculating step for calculating a time difference between the signal of the main channel and the signal of the bass sound effect channel;
A time difference correction step for correcting the time difference calculated by the time difference calculation step,
The time difference correction method, wherein the time difference correction step corrects the time difference only when the correlation determination step determines that the correlation is “present”. The signal acquisition step, the correlation determination step, the time difference calculation step, and the time difference correction step are repeatedly executed every predetermined time,
The time difference correction method according to claim 1, wherein the time difference correction step maintains the time difference calculated last time when the correlation determination step determines that the correlation is “none”. A polarity determination step for determining a polarity of the bass sound effect channel with respect to the signal of the main channel;
The time difference according to claim 1, further comprising a polarity correction step of correcting a polarity of the signal of the main channel or the signal of the bass sound effect channel according to a determination result of the polarity determination step. Correction method. A prefilter applying step of extracting a low-frequency component by applying a prefilter from the main channel signal;
2. The time difference correction method according to claim 1, wherein, in the correlation determination step, the presence or absence of the correlation between the main channel signal and the bass sound effect channel signal is determined after the prefilter application step. .   5. The prefilter applying step according to claim 4, wherein a prefilter similar to the prefilter applied to the main channel signal is applied to the bass sound effect channel signal. Time difference correction method. After the pre-filter applying step, further performing a normalizing step of normalizing the signal amplitude of the main channel and the bass sound effect channel,
5. The time difference correction method according to claim 4, wherein, in the correlation determination step, after the normalization step, the presence / absence of the correlation between the main channel signal and the bass sound effect channel signal is determined.   The time difference correction method according to claim 1, wherein in the signal acquisition step, a section in which audio characteristics of the surround content are characteristic is extracted as the partial section. An audio signal processing device that corrects a time difference between a main channel and a bass sound effect channel that occurs during the production of surround content,
Signal acquisition means for acquiring a signal of the main channel and a signal of the bass sound effect channel in a partial section of the surround content;
Correlation determining means for determining the presence or absence of correlation between the signal of the main channel and the signal of the bass sound effect channel;
A time difference calculating means for calculating a time difference between the signal of the main channel and the signal of the bass sound effect channel;
A time difference correction means for correcting the time difference calculated by the time difference calculation means,
The audio signal processing apparatus, wherein the time difference correction unit corrects the time difference only when the correlation determination step determines that the correlation is “present”. Each means in the audio signal processing device according to claim 8,
A reproduction apparatus for reproducing the surround content after the time difference correction by the time difference correction means.   The program for making a computer perform each step in the time difference correction method of any one of Claim 1 thru | or 7.

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