JP2005284162A - Signal coding device, signal decoding device, signal coding method, and signal decoding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a compression efficiency in the transformational coding of a signal by localizing a transformational coefficient with respect to a transformation rule such as a DCT (Discrete Cosine Transform) and an MDCT (Modified Discrete Cosine Transform) having no phase information clearly. <P>SOLUTION: The signal coding device 10 changes the timewise haracteristic of frame of an input signal divided by a frame dividing part 11 to a plurality of change values by using a timewise property changing part 13. A frame evaluation value calculating part 15 calculates evaluation values of the frames whose timewize properties are changed based on a prescribed criterion for evaluation. A signal coding part 17 transforms and codes a signal in which timewise properties of the frames are changed by optimum change quantities selected by a timewise property-change quantity selecting part 16. A coded series outputting part 18 outputs the transformed and coded signal as a signal coded series. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for codec decoding a signal such as an audio signal.

  In recent years, with the development of signal processing technology, many technologies for compressing and encoding audio signals with high efficiency have been proposed. The speech / acoustic encoding method is divided into a method of encoding in the time domain (time encoding method) and a method of encoding in the conversion domain after conversion according to a predetermined conversion rule (conversion encoding method). It can be divided roughly. As this conversion rule, for example, a rule for converting between the time domain and the frequency domain (time frequency conversion) such as DFT (Discrete Fourier Transform) and DCT (Discrete Cosine Transform) is generally used. Yes.

  In the time-frequency transform, a transform frame in the frequency domain is obtained by forming a transform frame by collecting a certain number of samples in the time domain and applying the transform rule to the transform frame. A method of compressing and encoding the transform coefficient is a transform coding method. As a typical audio signal coding technique using the transform coding system, there can be mentioned MPEG-2 Audio AAC (Moving Picture Expert Group-2 Advanced Audio Coding) standardized by ISO / IEC (for example, (Refer nonpatent literature 1.). In AAC, a conversion rule called Modified Discrete Cosine Transform (MDCT) is used, and this conversion rule is also a time-frequency conversion.

  Non-Patent Document 2 discloses a method that uses phase equalization in encoding processing of an analysis / synthesis system based on a pitch pulse driving sound source and LPC (Linear Predictive Coding) filter, which are time domain encoding. ing. Usually, in the synthesis of the pitch pulse driving sound source and the LPC filter, the phase characteristic is limited to the minimum phase characteristic, and it is difficult to achieve consistency with the original voice. Therefore, in the technology disclosed in Non-Patent Document 2, in view of the advantage that there is little change in subjective quality even when the phase of the audio is deformed, the audio obtained by phase equalizing the original audio to the minimum phase, And matching with the synthesized speech of the LPC filter.

  Further, Patent Document 1 discloses a method for avoiding a pre-echo that occurs when there is a steep rise (hereinafter referred to as “attack”) in the middle of a frame during transform encoding. This pre-echo is a distortion that occurs in a relatively small portion of the signal level existing before the attack, and is easily perceived as an annoying sound. In the technique described in Patent Document 1, pre-echo is avoided by controlling the position of an attack existing in the middle of a frame to be the start position of the frame.

JP 2000-196252 A ISO / IEC JTC1 / SC29 / WG11 MPEG.International Standard IS 13818-7 Information Technology -Generic Coding of Moving Pictures and Associated Audio, Part 7: MPEG-2 AAC, 1997. Masaaki Honda, “Speech analysis and synthesis system using phase equalized sound source”, IEICE Technical Report SP89-124, 1989.

However, the above prior art has the following problems.
First, regarding Non-Patent Document 1, the DFT change coefficient includes amplitude information and phase information of the conversion base, while the MDCT change coefficient includes only the amplitude information of the conversion base. In this respect, the coefficient of change of DCT is the same as that of MDCT. For this reason, when the phase of the signal component included in the input signal matches the phase of the conversion base having the same frequency as that of the signal component, the signal component can be expressed only by the conversion base. However, when these phases are shifted, a signal component cannot be expressed unless the conversion bases of other frequencies are referred to as well. As a result, there is a problem that the transform coefficient is diffused to other frequencies without being localized to the frequency of the signal component, and the compression effect is reduced.

  Further, as described above, the method described in Non-Patent Document 2 is a method for phase equalizing the original speech in view of the phase characteristics of the analysis / synthesis coding based on the pitch pulse driving sound source and the LPC filter. is there. However, since this method does not localize the transform coefficient of the input signal, the compression effect in transform coding does not increase. Also, when determining the phase equalization parameter, a process is performed in which an evaluation value is calculated for each parameter using a given evaluation criterion, and the parameter is determined based on a result of comparison of the evaluation value. Absent.

  Furthermore, the technique described in Patent Document 1 assumes a special situation in which an attack exists in the middle of a frame, and the document does not mention anything about a situation in which no attack exists.

  Therefore, in view of the above-described problems, an object of the present invention is to enable localization of transform coefficients for transform rules that do not explicitly include phase information, such as DCT and MDCT. It is to improve the compression efficiency in transform coding.

  A signal encoding apparatus according to the present invention includes a dividing unit that divides an input signal into frames, a changing unit that changes temporal characteristics of the frame by a plurality of changing amounts, and a time based on a predetermined evaluation criterion. A calculation unit that calculates an evaluation value of the frame in which a characteristic is changed, a selection unit that selects an optimal change amount from the plurality of change amounts based on the calculated evaluation value, and Coding means for transform-coding the signal whose temporal characteristics of the frame have been changed by the optimum change amount, and output means for outputting the transform-coded signal as a signal coding sequence.

  A signal encoding method according to the present invention includes a dividing step of dividing an input signal into frames, a changing step of changing temporal characteristics of the frame by a plurality of changing amounts, and a time based on a predetermined evaluation criterion. A calculation step for calculating an evaluation value of the frame in which a characteristic is changed, a selection step for selecting an optimal change amount from the plurality of change amounts based on the calculated evaluation value, and An encoding step for transform-encoding the signal in which the temporal characteristic of the frame is changed by the optimum change amount; and an output step for outputting the transform-encoded signal as a signal encoding sequence.

  Preferably, the signal encoding device according to the present invention further includes a determination unit that determines whether or not to change the temporal characteristic of the frame, and the changing unit is determined to change the temporal characteristic by the determination unit. The temporal characteristics of the received frame are changed by a plurality of change amounts, and the encoding means, with respect to the frame determined to change the temporal characteristics by the determination means, only the selected optimal change amount of the frame. The signal with the temporal characteristic changed is transform-coded, and for the frame determined not to change the temporal characteristic by the determination means, the signal of the frame is directly transform-coded.

In the signal encoding device according to the present invention, the encoding means encodes the optimal change amount in conjunction with the signal of the frame, and the output means in combination with the signal encoded sequence A change amount coded sequence indicating the change amount may be output.
The encoding means of the signal encoding apparatus according to the present invention can encode either the discrete cosine transform coefficient or the modified discrete cosine transform coefficient.

The calculation means of the signal encoding device according to the present invention can calculate a conversion gain based on a predetermined conversion rule.
The calculation means may calculate auditory entropy based on an auditory psychological model.
Furthermore, the calculation means can also calculate an objective evaluation value based on a distortion signal of a code decoded signal (also referred to as an encoded decoded signal).

  The calculation means of the signal encoding apparatus according to the present invention may calculate the distortion amount of the codec signal. The distortion amount of the codec signal is, for example, an auditory weighted distortion amount.

  The signal decoding apparatus according to the present invention includes a decoding unit that decodes an input signal encoded sequence into a decoded signal, and a phase change amount, a sample deletion amount, and a sample insertion by decoding the input change amount encoded sequence. Generating means for generating a decoding change amount including at least one of the amount and the temporal expansion / contraction change amount, a changing means for changing a temporal characteristic of the decoded signal based on the decoding change amount, and the changing means And outputting means for outputting a decoded signal whose temporal characteristics are changed.

  The signal decoding method according to the present invention includes a decoding step for decoding an input signal encoded sequence into a decoded signal, and a phase change amount, a sample deletion amount, and a sample insertion by decoding the input change amount encoded sequence. A generation step for generating a decoding change amount including at least one of the amount and a temporal expansion / contraction change amount, a change step for changing a temporal characteristic of the decoded signal based on the decoding change amount, and the change step And outputting a decoded signal whose temporal characteristics have been changed.

  According to these inventions, after the input signal is once divided into frames, these frames are subjected to the temporal characteristic (for example, phase) changing process and encoded. Thereby, the conversion coefficient is localized. Therefore, the compression efficiency in transform coding is improved even for transform rules that do not have phase information. Furthermore, if the determination as to whether or not to change the temporal characteristics is performed in units of frames, it is possible to suppress an increase in the amount of processing associated with changing the temporal characteristics even with respect to unnecessary frames. .

  According to the present invention, by changing the temporal characteristics to localize the transform coefficient, the compression efficiency in transform coding can be improved even for transform rules having no phase information such as DCT and MDCT. Can be improved.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings for illustration only. First, the configuration of the signal encoding device 10 in the present embodiment will be described. As shown in FIG. 1, the signal encoding apparatus 10 includes a frame dividing unit 11 (corresponding to the dividing unit), a temporal characteristic change amount indicating unit 12, a temporal characteristic changing unit 13 (corresponding to the changing unit), and a temporal characteristic. Change signal holding unit 14, frame evaluation value calculation unit 15 (corresponding to calculation means), temporal characteristic change amount selection unit 16 (corresponding to selection means), signal encoding unit 17 (corresponding to encoding means), and encoded sequence And an output unit 18 (corresponding to output means). These units are connected via a bus.

Hereinafter, each component of the signal encoding device 10 will be specifically described.
The frame dividing unit 11 divides the input signal into frames having a predetermined length N. In this embodiment, the input signal is an audio signal after AD conversion, that is, a digital signal.
The temporal characteristic change amount instruction unit 12 holds K (K is a natural number) temporal characteristic change amounts in advance. The temporal characteristic change amount instruction unit 12 changes the temporal characteristic for one temporal characteristic change amount c _k (k = 0, 1,..., K−1) from among these temporal characteristic change amounts. The time characteristic changing unit 13 is instructed.

Temporal characteristic change unit 13, the m-th temporal characteristics of the input frame signal x _m of the divided frames, changing only the temporal characteristic change amount instructed by the temporal characteristic change amount instruction section 12. The temporal characteristic is, for example, the phase of the input signal. In this case, the temporal characteristic change amount is the phase change amount of the input signal. The temporal characteristic changing unit 13 outputs a frame whose temporal characteristic has been changed as a temporal characteristic changing frame signal x _mk .

The temporal characteristic change signal holding unit 14 holds the temporal characteristic change frame signal x _mk input from the temporal characteristic changing unit 13. Further, the temporal characteristic change signal holding section 14, of all the temporal characteristic change amount c _k for the input frame signal x _m, temporal characteristic change amount of the optimum c _m, temporal characteristic change frame when taking _slt The signals x _{m and slt} are output to the signal encoding unit 17.

The frame evaluation value calculation unit 15 calculates a frame evaluation value from the temporal characteristic change frame signal x _mk input from the temporal characteristic change unit 13 using a predetermined calculation formula. As the frame evaluation value, for example, a conversion gain representing the degree of localization of the conversion coefficient can be used. When DCT (Discrete Cosine Transform) is applied as a conversion rule, the conversion coefficient g _mk is calculated by the following equation (1) using the DCT coefficient X _mkn (n = 0, 1,..., N−1). Can do.

Parameters other than the conversion gain can be used as the frame evaluation value. An example is auditory entropy. Auditory entropy is the minimum value of information necessary for encoding so that noise is not perceptually perceived. For a detailed method for calculating auditory entropy, see, for example, the document “Johnston, JD,“ Estimation of perceptual entropy using noise masking criteria ”, Proc. Of IEEE Int. Conf. Acoust., Speech and Signal Proc., Pp. 2524- 2527, 1988. ”.
Further, MDCT (Modified Discrete Cosine Transform) may be used as the conversion rule.

The frame evaluation value is calculated for the temporal characteristic change frame signal based on all temporal characteristic change amounts held in the temporal characteristic change amount instruction unit 12. That is, the frame evaluation value calculation unit 15 calculates the frame evaluation value E _mk for each of the K temporal characteristic change amounts _ck held in the temporal characteristic change amount instruction unit 12.

Temporal characteristic change amount selector 16, after the frame evaluation value E _mk for all temporal characteristic change amount c _k for an input frame signal x _m is calculated, the time frame evaluation value takes the highest value Select the characteristic change amount as the optimal change amount. When the frame evaluation value is the conversion gain, the temporal characteristic change amount having the largest corresponding conversion gain is selected as the optimum change amount. The temporal characteristic change amount selection unit 16 notifies the temporal characteristic change signal holding unit 14 of the optimal change amount _{cm, slt} of the selected temporal characteristic change amount.

The signal encoding unit 17 encodes the temporal characteristic change frame signal x _{m, slt} to generate a signal encoded sequence, and outputs the signal encoded sequence to the _subsequent encoded sequence output unit 18. The signal encoding unit 17 can use MPEG-2 Advanced Audio Coding (AAC) in MPEG-2 for transform encoding.
The encoded sequence output unit 18 outputs the signal encoded sequence input from the signal encoding unit 17 to an external device.

  The signal held in the temporal characteristic change signal holding unit 14 may not be a time signal. That is, when the frame evaluation value calculation unit 15 calculates the transform coefficient of the temporal characteristic change signal and this transform coefficient is used in the signal encoding unit 17, the transform coefficient is used as the temporal characteristic change signal holding unit. 14 may be held. In this case, there is an effect that it is not necessary to calculate the transform coefficient in the signal encoding unit 17.

Next, with reference to FIG. 2, the operation of the signal encoding apparatus 10 according to the present embodiment and each step constituting the signal encoding method according to the present invention will be described. As a premise for explaining the operation, it is assumed that the temporal characteristic change amount instruction unit 12 holds K temporal characteristic change amounts c _k (k = 0, 1,..., K−1).

First, when an input signal is divided into frames having a predetermined data length N (S1), “0” is set as an initial value to an index k for specifying a temporal characteristic change amount (S2). Subsequently, the magnitude relationship between the number K of temporal characteristic change amounts and the index k is compared (S3). if k <K is satisfied (S3; YES), the temporal characteristics of the input frame signal x _m is changed by the temporal characteristic change amount c _k, as a result, generation and temporal characteristic change frame signal x _mk It is held (S4).

In S5, the frame evaluation value E _{mk of} the temporal characteristic change frame signal x _mk generated in S4 is calculated. Thereafter, 1 is added to k (S6), and a series of processes from S3 to S6 are repeatedly executed until k = K is established.

When k <K is not satisfied, that is, when k ≧ K is satisfied (S3; NO), the most evaluated frame evaluation value E _mk corresponding to each temporal characteristic change amount _ck used in S4. A high value _{Em, slt} is selected. Then, the temporal characteristic change amount _{cm, slt} corresponding to this is selected as the optimum change amount (S7). In S8, the temporal characteristic change frame signal _{xm, slt} corresponding to the temporal characteristic change amount _{cm, slt} is encoded. The encoded sequence of the temporal characteristic change frame signal _{xm, slt} is output to the outside of the apparatus as a signal encoded sequence (S9).

  In S10, it is determined whether a series of processes (each process of S2 to S9) has been completed up to the final frame among the frames constituting the input signal divided in S1. If it has not been completed (S10; NO), it can be determined that there remains a frame for which a signal encoded sequence has not yet been output. When the above-described series of processing is completed for all the frames constituting the input signal (S10; YES), the signal encoding processing of the present embodiment ends.

  Here, FIG. 3 is a flowchart for explaining the operation of the signal encoding device 10 according to a modification of the first embodiment. Since the operation of the signal encoding device 10 in this aspect is similar to the operation of the signal encoding device 10 described in detail above, common steps are denoted by the same step numbers and description thereof is omitted. In this aspect, the processing of S7 is omitted by adding the processing of S11 to S13, which is the difference, as the post-processing of S5.

That is, in S11, it is determined whether or not k = 0. If k = 0 (S11; YES), E _{m, slt} = E _mk , _{cm, slt} = c _k , x _{m , Slt} = x _mk are set (S12). On the other hand, if k ≠ 0 (S11; NO), it is determined whether or not the evaluation of the frame evaluation value E _mk is higher than the evaluation of E _{m, slt} (S13). As a result of the determination, when the evaluation of the frame evaluation value E _mk is higher than the evaluation of E _{m, slt} (S13; YES), the process proceeds to S12, and the evaluation of the frame evaluation value E _mk is equal to or less than the evaluation of E _{m, slt} . (S13; NO), the process of S12 is omitted, and the process proceeds to S6 and subsequent processes.

  By adopting such a modification mode, if the temporal characteristic change signal, the temporal characteristic change amount, and the frame evaluation value with the highest evaluation are held in the signal encoding device 10, the transform coefficient is localized. can do. In other words, since it is not necessary to hold all temporal characteristic change signals, temporal characteristic change amounts, and frame evaluation values, data storage area can be saved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a block diagram showing a functional configuration of the signal encoding apparatus according to the present embodiment. Since the configuration of the signal encoding device 20 is similar to the configuration of the signal encoding device 10 described in detail in the first embodiment, common components are denoted by the same column (same end), and the description thereof will be given. While omitted, the differences from the first embodiment will be described in detail.

The change amount encoding unit 29 is a component unique to the signal encoding device 20.
The change amount encoding unit 29 encodes the temporal characteristic change amounts _{cm and slt} notified from the temporal characteristic change amount selection unit 26 to generate a change amount encoded sequence. This change amount encoded sequence is output by the encoded sequence output unit 28 together with the signal encoded sequence.

  Next, the signal encoding process in the second embodiment will be described with reference to FIG. This signal encoding process includes a plurality of steps in common with the signal encoding process (see FIG. 2) described in detail in the first embodiment. Specifically, S21 to S27 and S210 in FIG. 5 correspond to S1 to S7 and S10 shown in FIG. 2, respectively.

Hereinafter, S28 and S29, which are the differences between the first and second embodiments, will be described. In S28 of FIG. 5, the encoded sequence output unit 28 encodes the temporal characteristic change frame signal _{xm, slt} and the optimal change amount _{cm, slt} . As a result, a signal encoded sequence is generated from the temporal characteristic change frame signals x _{m and slt ,} and a change amount encoded sequence is generated from the optimal change amounts _{cm and slt} . These encoded sequences are output to the external device by the encoded sequence output unit 28 (S29).

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
FIG. 6 is a block diagram showing a functional configuration of the signal encoding apparatus according to the present embodiment. Since the configuration of the signal encoding device 30 is similar to the configuration of the signal encoding device 10 described in detail in the first embodiment, common components are denoted by the same reference numerals (same end), and the description thereof is as follows. While omitted, the differences from the first embodiment will be described in detail.

The temporal characteristic change determination unit 39 (corresponding to the determination unit) is a component unique to the signal encoding device 30.
The temporal characteristic change determination unit 39, and determines whether to perform the process of changing the temporal characteristics with respect to the divided m-th input frame signal x _m. As the basis for judgment, for example, calculates the power value of the input frame signal x _m, it may be utilized magnitude relation between the power value and the threshold value. That is, the temporal characteristic change determination unit 39 executes the temporal characteristic change process only when the power value of the frame is equal to or greater than the threshold value.

  Subsequently, a signal encoding process according to the third embodiment will be described with reference to FIG. This signal encoding process includes a plurality of steps in common with the signal encoding process (see FIG. 2) described in detail in the first embodiment. Specifically, S31 and S33 to S311 in FIG. 7 correspond to S1, S2 to S10 shown in FIG.

  Hereinafter, S32 and S312 which are the differences between the first and third embodiments will be described. In S32 of FIG. 7, the temporal characteristic change determination unit 39 determines whether or not to execute the temporal characteristic change process. As a result of the determination, if execution of the change process is determined (S32; YES), the process proceeds to S33 and subsequent steps. On the other hand, when it is determined not to execute the change process (S32; NO), the signal encoding process proceeds to S312. That is, the input frame signal is output from the frame dividing unit 31 to the signal encoding unit 37, and is encoded without being subjected to the temporal characteristic changing process (S39). The signal encoded sequence generated as a result of encoding is output to the outside from the encoded sequence output unit 38 (S310).

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a block diagram showing a functional configuration of the signal encoding apparatus according to the present embodiment. Since the configuration of the signal encoding device 40 is similar to the configuration of the signal encoding device 30 described in detail in the third embodiment, common components are denoted by the same reference numerals (same end), and description thereof will be given. While omitted, the differences from the third embodiment will be described in detail.

The temporal characteristic change determination unit 49, and determines whether to perform the process of changing the temporal characteristics with respect to the divided m-th input frame signal x _m. When it is determined that the temporal characteristic changing process is not to be executed, the temporal characteristic change determining unit 49 outputs the input frame signal directly to the signal encoding unit 47 and performs the temporal characteristic changing process. The change amount encoding unit 410 is notified of the time characteristic change amount “zero” indicating that the change is not made. On the other hand, when it is determined that the temporal characteristic changing process is to be executed, the temporal characteristic change determining unit 49 does not notify the change amount encoding unit 410 of the change amount “zero”, and the input frame signal Is output to the temporal characteristic changing unit 43.

The change amount encoding unit 410 encodes the temporal characteristic change amounts _{cm and slt} notified from the temporal characteristic change amount selection unit 46 to generate a change amount encoded sequence. Also, the change amount encoding unit 410 encodes the change amount “zero” input when the temporal characteristic change process is not executed, and generates a change amount encoded sequence. These change amount encoded sequences are output together with the signal encoded sequence by the encoded sequence output unit 48.

  Next, a signal encoding process in the fourth embodiment will be described with reference to FIG. This signal encoding process is basically the same as the signal encoding process (see FIG. 7) described in detail in the third embodiment. Specifically, S41 to S411 in FIG. 9 correspond to S31 to S311 shown in FIG. 7, respectively. In particular, the processes of S49 and S410 are the same as S28 and S29 (see FIG. 5) described in the second embodiment.

Hereinafter, S412 which is the difference between the third and fourth embodiments will be described. S412 in FIG. 9 is executed when it is determined that the temporal characteristic changing process is not executed (S42; NO). In S412, the input frame signal _{x m} is the temporal characteristic change frame signal _{x m,} is input to the signal encoding unit 47 as a _slt. Similarly, “zero” indicating that the change processing is not performed is input to the change amount encoding unit 410 as the optimum change amount _{cm, slt} . When the process of S412 ends, the process proceeds to S49 and subsequent processes.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a block diagram illustrating a functional configuration of a signal decoding apparatus that decodes a generated encoded sequence. As shown in FIG. 10, the signal decoding apparatus 50 includes a signal decoding unit 51 (corresponding to the decoding unit), a change amount decoding unit 52 (corresponding to the generating unit), and a temporal characteristic changing unit 53 (corresponding to the changing unit). And a temporal characteristic change decoded frame signal output unit 54 (corresponding to output means). These units are connected via a bus.

The signal decoding unit 51 decodes the input signal encoded sequence to obtain a decoded signal.
The change amount decoding unit 52 decodes the input change amount encoded sequence to obtain a decoding change amount including at least one of a phase change amount, a sample deletion amount, a sample insertion amount, and a temporal expansion / contraction change amount. Generate.

The temporal characteristic changing unit 53 changes the temporal characteristic of the decoded signal based on the generated decoding change amount. The temporal characteristic change unit 53 functions as, for example, a phase change unit. In this case, a change amount encoded sequence in which a phase change amount is encoded is used. For example, in the signal encoding device 20 according to the second embodiment, when the temporal characteristic of the input frame signal x _m is changed by the decoding change amount c _slt, the signal decoding device 50 according to the present embodiment uses − the c _slt, changes the temporal characteristics of the decoded frame signal _{x m.}
The temporal characteristic changed decoded frame signal output unit 54 outputs the decoded signal whose temporal characteristic has been changed to the outside as a temporal characteristic changed decoded frame signal (corresponding to the decoded signal).

Next, the operation of the signal decoding device 50 will be described with reference to FIG.
First, at T1, the signal decoding unit 51 decodes the input signal encoded sequence, and as a result, a decoded frame signal x ′ _m is generated. The decoded frame signal x ′ _m is input to the temporal characteristic changing unit 53. On the other hand, the change amount decoding unit 52 generates a decoding change amount _c′slt as a result of decoding the input change amount coded sequence (T2). This decoding change amount c ′ _slt is input to the temporal characteristic changing unit 53. The processes of T1 and T2 may be executed in the order of T2 and T1, that is, in the reverse order, or may be executed in parallel at the same time.

The temporal characteristic change section 53, 'the temporal characteristics of _m, the decoding change amount c' the decoded frame signal x to change based on _slt, temporal characteristic change decoded frame signal x _'m, to produce a _slt ( T3). The generated temporal characteristic change decoded frame signal x ′ _{m, slt} is output from the temporal characteristic change decoded frame signal output unit 54 (T4). At T5, it is determined whether or not the decoding process up to the final frame signal has been completed. If it has not been completed (T5; NO), the processes after T1 are executed again. When the signal decoding process for all the frame signals is completed (T5; YES), a series of signal decoding processes are completed.

  As described above, according to the signal encoding devices 10 to 50 in the first to fifth embodiments, after the input signal is divided into frames, the temporal characteristic (for example, phase) change processing is performed on these frames. And encoding (decoding in the fifth embodiment). Therefore, since the transform coefficient is localized even for a transform rule that does not explicitly include phase information, the compression efficiency (transformation efficiency in the fifth embodiment) in transform coding is improved. Furthermore, according to the signal encoding devices 10, 30, and 40 in the first, third, and fourth embodiments, since it is determined in units of frames whether or not the temporal characteristics are to be changed, it is unnecessary originally. Thus, the process of changing the temporal characteristics related to the frame can be omitted. As a result, the processing amount is reduced to a necessary minimum.

In addition, this invention is not limited to each embodiment mentioned above, In the range which does not deviate from the meaning, a deformation | transformation aspect can also be taken suitably.
For example, in the first to fifth embodiments, the temporal characteristic changing unit changes the phase, which is an example of the temporal characteristic, but may have a sample deletion function. That is, the temporal characteristic changing unit deletes the sample from the input signal by the amount of sample deletion when the sample deletion amount is instructed as the temporal characteristic change amount. In such an aspect, when the input signal is divided into frames, the frame dividing unit deletes the sample from the certain frame signal by the sample deletion amount, and then adds the sample to the subsequent frame signal by the sample deletion amount. Thus, a frame having a data length N is configured.

  On the contrary, the temporal characteristic changing unit may have a sample insertion function. That is, the temporal characteristic changing unit inserts a sample into the input signal by the amount of sample insertion when the sample insertion amount is instructed as the temporal characteristic change amount. In this aspect, when the frame dividing unit divides the input signal into frames, after inserting the sample by the sample insertion amount into a certain frame signal, the sample is inserted by the sample insertion amount from the sample at the end of the frame signal. Erase. Thus, a frame having a data length N is configured. The erased sample is used as the first sample of the subsequent frame signal.

  Furthermore, the temporal characteristic changing unit may have a temporal expansion / contraction function. That is, the temporal characteristic changing unit increases the time resolution of a certain part of the input frame signal and decreases the time resolution of another signal part accordingly. This realizes temporal expansion and contraction of the input frame signal without changing the number of samples.

  More specifically, with reference to FIG. 12, the temporal characteristic changing unit (for example, the temporal characteristic changing unit 13 in the first embodiment) can be divided into a plurality of characteristic changing units. That is, the first temporal characteristic changing unit 131 can have a phase changing function, and the second and third temporal characteristic changing units 132 and 133 can have a sample deletion function and a sample insertion function, respectively. In this case, the frame evaluation value calculation unit 15 calculates a frame evaluation value for each of the first to third temporal characteristic change signals.

For example, the temporal characteristic change amount instruction section 12, or K ₁ of the first temporal characteristic change amount, a second temporal characteristic change amount _two K, the third temporal characteristic change amount _three K, retained It shall be. In such an example, (K ₁ + K ₂ + K ₃ ) frame evaluation values are calculated. The temporal characteristic change amount selection unit 16 compares the frame evaluation values corresponding to all these temporal characteristic change amounts, and selects the temporal characteristic change amount having the highest evaluation as the optimal change amount. The temporal characteristic change signal corresponding to the selected optimal change amount is output from the temporal characteristic change signal holding unit 14 to the signal encoding unit 17.

  In this modification, the temporal characteristic change amount instruction unit 12 may instruct different types of temporal characteristic change amounts for each frame signal. Further, the time characteristic change amount to be indicated may be changed according to the time characteristic change amount selected in the past frame signal.

  Further, the signal coding apparatus according to another modification mode calculates coding distortion, and uses the distortion amount or the distortion amount subjected to auditory weighting as a frame evaluation value. Alternatively, an objective evaluation value calculated by PESQ (ITU-T recommendation P.862) or PEAQ (ITU-R recommendation BS.1387-1) using a codec signal may be used. FIG. 13 shows a configuration example of the signal encoding apparatus in an aspect (the former aspect) in which the amount of distortion of the codec signal is an evaluation value.

As shown in FIG. 13, the temporal characteristic change frame signal x _mk is encoded by the signal encoding unit 17, and as a result, a signal encoded sequence is generated. This signal encoded sequence is output to the encoded distortion amount calculation unit 19 and the signal encoded sequence holding unit 110. The coding distortion amount calculation unit 19 decodes the input signal coded sequence to obtain a coded signal. Then, a distortion energy amount (encoding distortion amount d _mk ), which is a difference between this signal and the input frame signal, is calculated.

When the encoding distortion amount d _mk corresponding to all temporal characteristic change amounts _ck is calculated for the input frame signal x _m , the temporal characteristic change amount selection unit 16 corresponds to the smallest encoding distortion amount. The temporal characteristic change amount is selected as the optimal change amount _{cm, slt} . In the signal encoded sequence holding unit 110, the temporal characteristic change amount and the signal encoded sequence are stored in advance in association with each other. The signal encoded sequence holding unit 110 outputs the signal encoded sequence corresponding to the optimal change amount _{cm, slt} notified from the temporal characteristic change amount selecting unit 16 to the encoded sequence output unit 18. The encoded sequence output unit 18 outputs this signal encoded sequence.

  Regarding the first embodiment, it is as described above that the modified embodiment described with reference to FIG. 3 can be adopted. However, this embodiment is similar to the other modified embodiments in the second to fourth embodiments. It is applicable to the form. This eliminates the need for the signal encoding device to hold all temporal characteristic change signals, temporal characteristic change amounts, and frame evaluation values. For this reason, the storage data capacity can be reduced.

It is a block diagram which shows the structure of the signal encoding apparatus in the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the signal encoding apparatus in 1st Embodiment. It is a flowchart which shows operation | movement of the signal coding apparatus in the deformation | transformation aspect of the 1st-4th embodiment of this invention. It is a block diagram which shows the structure of the signal encoding apparatus in 2nd Embodiment. It is a flowchart which shows operation | movement of the signal encoding apparatus in 2nd Embodiment. It is a block diagram which shows the structure of the signal encoding apparatus in 3rd Embodiment. It is a flowchart which shows operation | movement of the signal coding apparatus in 3rd Embodiment. It is a block diagram which shows the structure of the signal encoding apparatus in 4th Embodiment. It is a flowchart which shows operation | movement of the signal encoding apparatus in 4th Embodiment. It is a block diagram which shows the structure of the signal decoding apparatus in the 5th Embodiment of this invention. It is a flowchart which shows operation | movement of the signal decoding apparatus in the 5th Embodiment of this invention. It is a block diagram which shows the apparatus structure in the deformation | transformation aspect (The aspect which divided the time characteristic change part into the function) of 1st-5th embodiment. It is a block diagram which shows the structure of the signal coding apparatus in the deformation | transformation aspect (mode which uses distortion amount for an evaluation value) of 1st-4th embodiment.

Explanation of symbols

  10, 20, 30, 40 ... signal encoding device, 11, 21, 31, 41 ... frame division unit, 12, 22, 32, 42 ... temporal characteristic change amount instruction unit, 13, 23, 33, 43 ... time Characteristic change unit, 131... First time characteristic change unit, 132... Second time characteristic change unit, 133... Third time characteristic change unit, 14, 24, 34, 44. , 15, 25, 35, 45... Frame evaluation value calculation unit, 16, 26, 36, 46... Temporal characteristic change amount selection unit, 17, 27, 37, 47... Signal encoding unit, 18, 28, 38,. 48 ... Coding sequence output unit, 19 ... Coding distortion amount calculation unit, 110 ... Signal coding sequence holding unit, 29, 410 ... Change amount coding unit, 39, 49 ... Temporal characteristic change determination unit, 50 ... Signal Decoding device 51... Signal decoding unit 52. Change amount decoding unit 53 Temporal characteristic change portion, 54 ... temporal characteristics change decoded frame signal output unit

Claims (12)

A dividing means for dividing the input signal into frames;
Change means for changing the temporal characteristics of the frame by a plurality of change amounts;
A calculation means for calculating an evaluation value of the frame whose temporal characteristics have been changed based on a predetermined evaluation criterion;
Selection means for selecting an optimum change amount from the plurality of change amounts based on the calculated evaluation value;
Coding means for transform-coding a signal in which the temporal characteristics of the frame are changed by the selected optimum change amount;
And a signal encoding device comprising: an output unit configured to output the transform-coded signal as a signal encoded sequence. A determination means for determining whether to change the temporal characteristic of the frame;
The changing means changes the temporal characteristics of the frame determined to change the temporal characteristics by the determining means by a plurality of change amounts,
The encoding unit transform-encodes a signal in which the temporal characteristic of the frame is changed by the selected optimal change amount for the frame determined to change the temporal characteristic by the determining unit; 2. The signal encoding apparatus according to claim 1, wherein for the frame determined not to change the temporal characteristic by the determination unit, the signal of the frame is directly converted and encoded. The encoding means encodes the optimum amount of change together with the signal of the frame,
The signal encoding apparatus according to claim 1, wherein the output unit outputs a change amount coding sequence indicating the optimum change amount together with the signal coding sequence.   The signal encoding apparatus according to claim 1, wherein the encoding unit encodes either a discrete cosine transform coefficient or a modified discrete cosine transform coefficient.   The signal encoding apparatus according to claim 1, wherein the calculation unit calculates a conversion gain based on a predetermined conversion rule.   The signal encoding apparatus according to claim 1, wherein the calculating unit calculates an auditory entropy based on an auditory psychological model.   5. The signal encoding apparatus according to claim 1, wherein the calculation unit calculates an objective evaluation value based on a distortion signal of a code decoding signal. 6.   The signal encoding apparatus according to claim 1, wherein the calculation unit calculates a distortion amount of the codec signal.   The signal encoding apparatus according to claim 8, wherein the distortion amount of the codec signal is a perceptually weighted distortion amount. Decoding means for decoding an input signal encoded sequence into a decoded signal;
Generating means for generating a decoding change amount including at least one of a phase change amount, a sample deletion amount, a sample insertion amount, and a temporal expansion / contraction change amount by decoding the input change amount encoded sequence;
Changing means for changing a temporal characteristic of the decoded signal based on the decoding change amount;
An output means for outputting a decoded signal whose temporal characteristics have been changed by the changing means. A dividing step of dividing the input signal into frames;
A change step of changing the temporal characteristics of the frame by a plurality of change amounts;
A calculation step for calculating an evaluation value of the frame whose temporal characteristics are changed based on a predetermined evaluation criterion;
A selection step of selecting an optimal change amount from the plurality of change amounts based on the calculated evaluation value;
An encoding step of transform-encoding a signal in which the temporal characteristics of the frame are changed by the selected optimal change amount;
An output step of outputting the transform-encoded signal as a signal encoding sequence. A decoding step of decoding the input signal encoded sequence into a decoded signal;
Generating a decoding change amount including at least one of a phase change amount, a sample deletion amount, a sample insertion amount, and a temporal expansion / contraction change amount by decoding the input change amount encoded sequence;
A changing step of changing a temporal characteristic of the decoded signal based on the decoding change amount;
An output step of outputting the decoded signal whose temporal characteristics have been changed in the changing step.

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