JP2008158496A - Reproducing method and device, and program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent abnormal sounds from occurring due to influence of filtering delays when encoded audio data having stereo process information intermittently multiplexed are reproduced from an arbitrary frame. <P>SOLUTION: A monaural audio signal supplied from an input terminal 41 is band-divided by a band divider 44, and the stereo signals are generated by a stereo processor 45 on the basis of stereo process information from a terminal 42. The generated stereo signals are band-synthesized by band synthesizers 51 and 52. State variables of the band divider 44 are initialized when the stereo process information is not input and begin to be updated when the stereo process information is input. The monaural audio signal is copied and output from terminals 55 and 56 until the state variables are all updated, and a stereo audio signal generated through stereo processing by the stereo processor 45 based upon the stereo process information is output after the state variables are all updated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reproduction method and apparatus, a program, and a recording medium for decoding and reproducing encoded audio data transmitted by stereo-multiplexing information intermittently multiplexed with encoded information of a monaural audio signal. .

  2. Description of the Related Art There is known a playback device that receives a monaural audio signal and stereophonic information and generates a stereo audio signal by performing stereo processing on the monaural audio signal based on the stereogenic information.

  A general stereo process based on such monaural audio signal and stereo information will be described with reference to the drawings. FIG. 6 is a block diagram illustrating a configuration example of a general stereo device, and FIG. 7 is a diagram illustrating an example of a signal input to the stereo device of FIG. The stereo information may be multiplexed and transmitted.

  In FIG. 6, a monaural audio signal is supplied to the input terminal 41, and stereo information is supplied to the input terminal 42. The monaural audio signal from the input terminal 41 is sent to the band dividing unit 44 via the changeover switch 43, subjected to band division processing, and sent to the stereo processing unit 45. The stereo processing unit 45 is supplied with the stereo information from the input terminal 42, the band-divided monaural audio signal is stereo-processed, and the obtained stereo left and right channel signals are converted to the left channel (Lch). The data is sent to the band synthesis unit 51 and the right channel (Rch) band synthesis unit 52, respectively. The Lch audio signal from the band synthesizing unit 51 is sent to the changeover switch 53, and one of the signals from the changeover switch 43 via the delay unit 46 is selected and sent to the changeover switch 54 and the output terminal 55. . The Rch audio signal from the band synthesizing unit 52 is sent to the changeover switch 54, and one of the signals from the changeover switch 53 is selected and sent to the output terminal 56.

  FIG. 7 shows an example of a signal input to the stereo device of FIG. 6, and numbers # 0, # 1, # 2,... Are assigned for each transmission unit such as a frame or a block of encoded audio data. M represents a monaural audio signal and S represents stereo information. In the example of FIG. 7, the monaural audio signal M is always transmitted, but the stereo information S is multiplexed and transmitted, and is transmitted at a rate of once every five times. In this case, the stereo information S sent in the transmission unit # 0 is used for the stereo processing from the transmission units # 0 to # 4, and is switched to the next stereo information S in the transmission unit # 5. The stereo information S sent in the unit # 5 is used from the transmission units # 5 to # 9. Similarly, the stereo information S sent earlier is used until the next stereo information S is sent.

  In the configuration of FIG. 6, when the stereo information is input, the changeover switches 43, 53, and 54 are switched to the selection B terminal side. That is, the monaural audio signal input from the input terminal 41 is band-divided by the band dividing unit 44, and the stereo processing unit 45 creates a stereo signal based on the stereo information. The created stereo signal is subjected to band synthesis by the band synthesis processing units 51 and 52 of the respective channels, and the respective audio signals of the stereo left and right channels are output from the output terminals 55 and 56, respectively.

  On the other hand, when discontinuous frame reproduction such as fast-forward reproduction by thinning out reproduction of frames (transmission unit) is performed, or reproduction is performed from an arbitrary frame, multiplexed encoded information may be lost. . When encoded audio data is input from an arbitrary frame (transmission unit) by such discontinuous frame reproduction or the like, there is a state where there is no usable stereo information. For example, when the input starts from the position of the transmission unit # 2 in FIG. 7, the stereo information S of the transmission unit # 0 is not input by frame thinning or the like, and can be used between the transmission units # 2 to # 4. There will be no stereo information.

  In the apparatus of FIG. 6, even in a state where there is no usable stereoization information (for example, between transmission units # 2 to # 4 in FIG. 7) so that the number of channels of the output audio signal does not change depending on the presence or absence of stereoization information. The monaural audio signal is output to the stereo left and right channels. Specifically, the same monaural audio signal is output from the output terminals 55 and 56 by switching the selector switches 43, 53, and 54 to the selection A terminal side. Output. Here, when the changeover switch 43 is switched to the selection A terminal side, the monaural audio signal from the input terminal 41 is sent to the delay unit 46. This is the state in the band division unit 44, for example, as in FIR filter processing. This is because the variable is held and the state variable is updated every time it is processed, and a delay is generated, so that the input monaural audio signal is similarly given the delay generated by the band dividing unit 44. Since band synthesis is performed so that no delay occurs in the band synthesizing unit or the like, only the band dividing unit 44 is considered for the delay in the delay unit 46. The monaural audio signal from the delay unit 46 is output from the Lch output terminal 55 via the changeover switch 53 and output from the Rch output terminal 56 via the changeover switch 54. When there is no usable stereo information as in the transmission units # 2 to # 4 in FIG. 7, the state variables such as the internal band dividing unit 44 are initialized.

  Therefore, when data is input from the position of the transmission unit # 2 in FIG. 7, the internal state variables are initialized between the transmission units # 2 to # 4, and each of the stereo device of FIG. The change-over switches 43, 53, 54 are switched to the selection A terminal side. When data at the position of transmission unit # 5 is input, the change-over switches 43, 53, 54 are switched to the selection B terminal side, and the internal switches The state variable is updated. Note that the switching operation of each change-over switch 43, 53, 54 and the processing operation of each part are controlled by a control unit (not shown) according to the contents of input data, the internal state, and the like.

  Here, a specific example of an encoding method in which a part of encoded information for stereo processing or the like is multiplexed and transmitted to a monaural audio signal will be described below.

  For example, HE AAC (High Efficiency Advanced Audio Coding, international standard ISO / IEC 14496-3), particularly audio data encoded by the encoding method of HE AAC v2 (version 2) is necessary for decoding. Part of the encoded information is multiplexed and transmitted. This HE AAC v2 encoding method is configured by combining three technologies of AAC (Advanced Audio Coding) processing, SBR (Spectral Band Replication) processing, and PS (Parametric Stereo) processing. The encoded information is partially multiplexed and transmitted.

  The AAC process is an encoding process in a voice compression system standardized by MPEG (Moving Picture Experts Group) audio, and the SBR process is divided into a plurality of bands, and the high sound range is replicated from the low frequency range. The PS process is an encoding process for performing band extension, and the PS process is an encoding process for performing spatial encoding using spatial information or the like necessary for generating a stereo signal from a monaural signal.

  The encoded audio data encoded by the HE AAC v2 method includes encoded information of the AAC core corresponding to the monaural audio data encoded by the AAC encoding method, encoded information of the SBR process, It is comprised with the encoding information of said PS process. The encoded information of the SBR process is composed of encoded information (sbr header) that is multiplexed and transmitted intermittently and encoded information (sbr data) that is always transmitted, and decodes sbr data (SBR data). To achieve this, an sbr header (SBR header) is required. The content of the sbr header (SBR header) can be changed according to a certain rule, and the timing of transmission is left to the operation. The PS processing encoding information (ps data) is transmitted by being included in an extension area of sbr data (SBR data). Therefore, sbr header (SBR header) information is also required to decode ps data (PS data). In other words, the sbr header (SBR header) is information necessary for stereoization necessary to obtain ps data (PS data) for stereo processing. FIG. 8 shows an example of audio data encoded by the HE AAC v2 encoding method. In FIG. 8, AC indicates coding information of the AAC core, SH indicates the sbr header (SBR header), and SD indicates the sbr data (SBR data).

  As shown in FIG. 8, in order to decode SD (SBR data) and PS data included in the extension area, SH (SBR header) transmitted intermittently is required. When playback is performed from such an arbitrary frame, multiplexed SH (SBR header) may be lost. Here, especially when the multiplexed frame is not always monitored on the upper side or the like, the encoded information (AC) of the AAC core is reached until the frame where the multiplexed SH (SBR header) is obtained. ) Is used to generate an output audio signal. As the decoding process in this case, the AAC decoding process is performed, and the upsampling process is performed by the band division and synthesis process of the SBR.

  When a frame including multiplexed SH (SBR header) is reached, the SD (SBR data) and PS data included in the extension area are decoded using the SH (SBR header), and these SBRs are decoded. A complete (including stereo) decoding process using data and PS data is performed to generate an output stereo audio signal. In the case of decoding the HE AAC v2 encoded audio data, the AAC decoding process is performed, and after the band division and the high-frequency generation are performed in the SBR process, the space encoded in the PS process is used. Based on the information, a stereo signal is generated from the monaural signal obtained by band division, and an output stereo audio signal is generated by band synthesis processing of SBR processing.

  FIG. 9 is a block diagram showing a configuration example of a reproducing apparatus for encoded audio data encoded by the HE AAC v2 method. The input terminal 11 of FIG. 9 includes a bit stream (Coded Audio Stream) of encoded audio data including AAC core encoded information, high frequency band encoded information (SBR data), and PS encoded information (PS data). ) Is transmitted and input, and some encoded information is multiplexed and transmitted. As described above, SH (SBR header) multiplexed and transmitted is required to decode the high frequency band encoded information (SBR data) and PS encoded information (PS data).

  In the HE AAC v2 encoding method, when a part of SH (SBR header) is different from the previous frame, it is necessary to initialize the SBR process. By initializing the SBR process, state variables (delayed signals) such as a QMF analysis unit / synthesis unit and a hybrid analysis unit described later are initialized. Here, the state variable (delayed signal) is data (signal) held in the delay element in the filter. In the filter processing, the signal is input after being input according to the filter length. This means a delayed signal.

  Incidentally, monaural audio data obtained by decoding AAC encoded information encoded by the HE AAC v2 encoding method is upsampled by performing QMF analysis and QMF synthesis processing of SBR processing. For example, monaural audio data after AAC decoding is 24 kHz sampling and SBR processing is performed, so that audio data of 48 kHz sampling is obtained.

  In FIG. 9, encoded audio data from the input terminal 11 is sent to the payload deformator 12, and AAC core encoded information to the AAC core decoding unit 13, high-frequency generation encoded information (SBR data), PS It is separated into encoded information (PS data). The AAC core decoding unit 13 decodes the input AAC core encoded information, generates a monaural audio signal of the AAC core, and sends it to the SBR processing unit 20. The parser 14 of the SBR processing unit 20 acquires multiplexing information such as high-frequency generation encoded information from the payload deformator 12, confirms the contents, and determines whether or not initialization of the SBR processing is necessary. When initialization is required, an initialization control signal is output from the terminal 14t, and SBR processing of each unit is initialized as will be described later. The monaural audio signal sent from the AAC core decoding unit 13 to the SBR processing unit 20 is band-divided by the QMF analysis unit 21 and sent to the changeover switch 22. When the high-frequency generation encoded information (SBR data) is input, the changeover switch 22 is switched and connected to the selection B and C terminals, and the signal from the QMF analysis unit 21 is sent to the high-frequency generation unit 23. The high frequency generator 23 generates a high frequency signal, performs envelope adjustment with the envelope adjuster 24, and sends it to the changeover switch 25.

  When the stereo information is obtained from the PS encoded information (PS data), the changeover switches 22 and 25 are connected to the selection C terminal. A signal from the selection C terminal of the changeover switch 25 is sent to the hybrid analysis unit 27. The hybrid analysis unit 27 further divides the band of the input low frequency band signal into the signal analysis unit 29 and the stereo processing unit 30. The signal analysis unit 29 analyzes the input signal, adjusts the sound, and inputs the input signal to the stereo processing unit 30. The stereo processing unit 30 generates stereo left and right channel signals from the input band-divided signal and the stereo information. The generated stereo channel signals are synthesized by the hybrid synthesis units 31 and 32 of the respective channels, and the bands divided by the hybrid analysis unit 27 are further synthesized by the QMF synthesis units 33 and 34, respectively. The band divided by the QMF analysis unit 21 is synthesized to generate an output audio signal of stereo left and right channels (Lch, Rch). The Lch audio signal from the QMF synthesis unit 33 is sent to the changeover switch 36 and the output terminal 37. The Rch audio signal from the QMF synthesizing unit 34 is sent to the changeover switch 36, and one of the signals from the QMF synthesizing unit 33 is selected and sent to the output terminal 38.

  When multiplexed information such as the stereo information is not transmitted, the change-over switches 22, 25, 35, and 36 in FIG. 9 are switched and connected to the selection A or B terminal. In order to make the sampling frequency of the output audio signal constant, only the upsampling is performed using the QMF analysis unit 21 and the QMF synthesizing unit 33. Further, in order to make the number of output channels constant, the Lch audio signal is converted into the Rch audio signal. Copy to signal to generate output signal.

  FIG. 10 is a flowchart for explaining the decoding operation as described above in the configuration of FIG.

  In FIG. 10, the HEAAC v2 encoded data decoding process (deformatting process) is performed on the encoded information such as the bit stream of the encoded audio data input to the input terminal 11 in step S101. The above-described high-frequency generation encoded information and spatial encoded information as multiplexed encoded information are extracted, and the AAC core information is subjected to AAC signal processing in step S102. In the next step S103, it is determined whether or not to perform the SBR process. If YES, the process proceeds to step S104, and if NO, the process proceeds to step S114. These processes correspond to, for example, the processes in the payload formatter 12 and the AAC core decoding unit 13 in FIG.

  In step S104, for example, the QMF analysis unit 21 performs QMF band division processing. In the next step S105, it is determined whether or not the multiplexed encoded information has been decoded. If YES, the process proceeds to step S106, and if NO, the process proceeds to step S113. In step S106, for example, the high frequency generation unit 23 performs high frequency signal generation processing using multiplexed high frequency generation encoded information (multiplexed decoding information), and in the next step S107. It is determined whether or not PS processing is performed.

  If YES in step S107 (PS process is performed), the process proceeds to step S108 to perform a hybrid analysis process, a stereo signal generation process based on spatial information is performed in step S109, and a hybrid synthesis process is performed in step S110. The process proceeds to step S111. These processes correspond to, for example, the processes from the hybrid analysis unit 27 to the hybrid synthesis units 31 and 32 in FIG. When it is determined NO (No PS processing) in step S107, the process proceeds to step S111.

  In step S111, an Lch QMF band synthesis process is performed. In step S112, an Rch QMF band synthesis process is performed, and the obtained audio signal is output. In step S113, Lch QMF band synthesis processing is performed. In step S114, a monaural signal is duplicated as necessary to generate a stereo signal, and the obtained audio signal is output. These processes correspond to, for example, the processes performed by the changeover switches 22, 35, and 36 and the QMF synthesis units 33 and 34 in FIG.

  As conventional techniques, Patent Documents 1 and 2 disclose a technique for generating a stereo audio signal by performing stereo processing on a monaural audio signal based on stereo information, and Non-Patent Document 1 discloses the HE AAC. (High Efficiency Advanced Audio Coding) A coding standard is disclosed.

Special table 2004-535145 gazette JP 2006-085183 A ISO / IEC 14496-3: 2005, Information technology-Coding of audio-visual objects-part3: Audio

  By the way, when playback is performed from an arbitrary frame, such as by playing back discontinuous frames such as the frame skip playback described above, internal state variables are initialized, and then a part such as stereo information is multiplexed. Since the state variable is started to be updated when the encoded information is input, an abnormal sound is generated due to the influence of the filter delay or the like.

  For example, in the configuration of FIG. 6, when input starts from the position of transmission unit # 2 in FIG. When the stereo information is input at 5, each change-over switch 43, 53, 54 is switched to the selection B terminal side. The band division signal is generated by the band division unit 44 for the first time when switching to the selection B terminal side. Since the state variable of the band division unit 44 at this time is initialized, the transmission unit # 5 This effect will occur in the output corresponding to. For example, an influence such as attenuation of the output signal can be considered. For this reason, abnormal noise is caused.

  In the case of the configuration shown in FIG. 9 described above, if the frame data is played back discontinuously as in the case of fast-forward playback of the audio data encoded by the HE AAC v2 system by frame skip playback or the like, The sbr header (SBR header) may be dropped. For example, in the case of the example of FIG. 8, when playback is performed from frame (transmission unit) # 1, SH (SBR header) is transmitted starting from frame # 5. In this case, since the SBR encoded information and the PS encoded information of SD (SBR data) cannot be decoded until the frame in which SH (SBR header) is obtained, the changeover switch 22 is connected to the selection A terminal side, the changeover switch. 35 is connected to the selection A terminal side and the changeover switch 36 is connected to the selection B terminal side, and the monaural audio signal of the AAC core is monophonic using the QMF analysis unit 21 of SBR processing and the QMF synthesis unit 33 of Lch. The signal is upsampled to produce the same output audio signal for the stereo left and right channels.

  When frame playback is performed in a discontinuous manner as described above, the state variable (delayed signal) of the filter in the playback device and the audio data encoded by the input HE AAC v2 encoding method become discontinuous. It is necessary to initialize (including SBR process initialization) and initialize state variables in the playback apparatus. The state variables (delayed signals) inside the playback device include the state variables of the QMF analysis unit 21, the QMF synthesis units 33 and 34, and the hybrid analysis unit 27, and are set to 0 by initialization. Until the SH (SBR header) is transmitted, the SBR encoded information / PS encoded information cannot be decoded. Therefore, the changeover switch 22 selects the monaural audio signal of the AAC core decoding unit 13 and the changeover switch 35 The selection A terminal side and the changeover switch 36 are switched to the selection A terminal side, and the QMF analysis unit 21 and the Lch QMF synthesis unit 33 are processed to perform up-sampling and output to the stereo left and right channels as output audio signals. When SH (SBR header) is transmitted, SBR encoded information and PS encoded information are decoded for the first time after initialization of the playback device, and SBR processing and PS processing are executed. Since the QMF analyzer 21 and the Lch QMF combiner 33 are processed for upsampling even before SH (SBR header) is transmitted, the state variables are updated. On the other hand, the state variables of the hybrid analysis unit 27 and the Rch QMF synthesis unit 34 are initialized. As a result, the subsequent processing is affected, and abnormal noise is generated in the output audio signal. Examples of output audio signals of the stereo left and right channels (Lch, Rch) at this time are shown in FIGS.

  11A and 11B show a state in which there is no multiplexed encoded information (stereo information or the like) that can be used, for example, only an AAC-LC (Low Complexity) encoded information signal is input and SBR is input. From the state in which only up-sampling is performed, multiplexed encoded information including stereo information becomes valid (usable) at time t1, and AAC processing, SBR processing, and PS processing start. 11A shows the output audio signal of Lch, and FIG. 11B shows the output audio signal of Rch.

  In (A) and (B) of FIG. 11, at time t1, the encoded information multiplexed for the first time after initialization of the internal state variable is recognized, but the state variable changes from the initialized state. During the time t1 to t2, the influence of the state variable of the band synthesizing unit (Rch QMF synthesizing unit 34) for the SBR processing appears in the output audio signal of Rch, and during the time t2 to t3, The influence of the state variable of the hybrid filter (hybrid analysis unit 27) for PS processing appears in both the Lch and Rch audio signals. For this reason, abnormal noise occurs in the output audio signal.

  As a method of avoiding this, it is conceivable to always monitor the multiplexed encoded information. In this case, since the multiplexed information is transmitted simultaneously with the normal encoded information, all the encoded information is transmitted. Information needs to be decrypted, and the amount of processing cannot be reduced.

  The present invention has been proposed in view of such a conventional situation, and is obtained by intermittently transmitting multiplexed encoded information and information necessary for decoding (such as an SBR header). Negative effects on the output audio signal due to filter delays when necessary encoding information is input from the state in which internal state variables are initialized when playback is performed from an arbitrary position (occurrence of abnormal noise, etc.) It is an object of the present invention to provide a reproducing method and apparatus, a program, and a recording medium that can effectively prevent the recording medium.

  In order to solve the above-described problem, the present invention decodes encoded audio data that is transmitted after the information required for stereo processing is intermittently multiplexed with the encoding information of a monaural audio signal. When stereo information required is not input during playback, a stereo audio signal using a monaural audio signal is output. When stereo information is input, state variables in the filter are updated. The stereo audio signal using the monaural audio signal is output until all the state variables are updated. When all the state variables in the filter are updated, the monaural audio signal needs to be made stereo. Perform stereo processing based on the stereo information obtained from the information to convert the stereo audio signal. Characterized in that it forms output.

  Here, the stereo process is preferably performed on a monaural audio signal whose band has been extended.

  In addition, when the stereo necessary information is not input, the mono audio signal is divided into at least two or more subbands by band division filter processing, and up-sampled by band synthesis filter processing, and stereo audio using the monaural audio signal When a signal is output and the stereo-necessary information is input, it is preferable to process a state variable inside the filter of the monaural audio signal as a filter state variable of the stereo audio signal.

  The encoded audio data includes: AAC core encoding information corresponding to monaural audio data in HE AAC (High Efficiency Advanced Audio Coding) encoding scheme; SBR (Spectral Band Replication) processing encoding information; The encoded information of the SBR process is always transmitted as an SBR header (sbr header) that is multiplexed and transmitted intermittently. PS data (ps data), which is encoded information of the PS processing, is included in an extension area of the SBR data and transmitted, and the SBR header is transmitted as SBR data (sbr data) that is encoded information. It is mentioned that it is the said stereoization required information required in order to decode the said SBR data.

  According to the present invention, it is possible to reproduce a good stereo audio signal without occurrence of abnormal sound even when stereo necessary information is input from when no stereo required information is input.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an example of a stereo device used in a playback device or playback method according to an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 6 described above are given the same reference numerals.

  The monaural audio signal is supplied to the input terminal 41 in FIG. 1, and the stereo information is supplied to the input terminal 42. The monaural audio signal from the input terminal 41 is sent to the switch 43X and the delay unit 46. The monaural audio signal from the switch 43X is sent to the band dividing unit 44, subjected to band division processing, and sent to the stereo processing unit 45. The stereo processing unit 45 is supplied with the stereo information from the input terminal 42, and the mono audio signal subjected to the band division is stereo-processed. Among the obtained stereo left and right channel signals, the left channel (Lch) is processed. The signal is sent to the band synthesizing unit 51 via the switch 61, and the right channel (Rch) signal is sent to the band synthesizing unit 52 via the switch 62. The Lch audio signal from the band synthesizing unit 51 is sent to the changeover switch 53X, and one of the signals via the delay unit 46 is selected and sent to the changeover switch 54X and the output terminal 55. The Rch audio signal from the band synthesizing unit 52 is sent to the changeover switch 54X, and one of the signals from the changeover switch 53X is selected and sent to the output terminal 56. Note that the switching operation of each change-over switch 43X, 53X, 54X, the ON / OFF operation of the switches 61, 62, or the processing operation of each part is performed by a control unit (not shown) according to the content of input data, the internal state, etc. Be controlled.

  When the input signals (monaural audio signal M and intermittent stereo information S) as shown in FIG. 7 are supplied to the stereo device as shown in FIG. 1, it is transmitted in transmission unit # 0. The stereo information S thus used is used for the stereo processing of the transmission units # 0 to # 4, switched to the next stereo information S in the transmission unit # 5, and sent to the stereo unit S5. As described above, the information S is used from transmission units # 5 to # 9.

  When there is stereo information that can be used in this way, the switch 43X is connected to the selection B terminal, the switches 61 and 62 are connected to the selection C terminal, and the selector switches 53X and 54X are switched to the selection C terminal side. Connected. At this time, the monaural audio signal input from the input terminal 41 is band-divided by the band dividing unit 44, the stereo processing unit 45 creates a stereo signal based on the stereo information, and the created stereo signal is Then, band synthesis is performed by the band synthesis processing units 51 and 52 of the respective channels, and the respective audio signals of the obtained stereo left and right channels (Lch, Rch) are output from the output terminals 55 and 56, respectively.

  On the other hand, when encoded audio data is input from an arbitrary frame (transmission unit) by discontinuous frame playback such as fast-forward playback, there is a state where there is no usable stereo information. For example, when the input starts from the position of the transmission unit # 2 in FIG. 7, the stereo information S of the transmission unit # 0 is not input by frame thinning or the like, and can be used between the transmission units # 2 to # 4. There will be no stereo information. In this way, between the transmission units # 2 to # 4 where there is no usable stereoization information, the state variables of the internal band division unit 44 and the like are initialized, and each change-over switch 53X of the stereoization apparatus of FIG. , 54X are switched to the selection A terminal side, and the monaural audio signal from the input terminal 41 via the delay unit 46 is output from the Lch output terminal 55 via the changeover switch 53X and at the same time Rch via the changeover switch 54X. Output from the output terminal 56. This prevents the number of channels of the output audio signal from changing depending on the presence or absence of the stereo information. The delay unit 46 is provided in consideration of a delay caused by, for example, FIR filter processing of the band dividing unit 44.

  Next, when the data of the position of transmission unit # 5 in FIG. 7 is input and usable stereo information S is supplied, first, the switch 43X is connected to the selection B terminal, and the monaural audio is supplied to the band dividing unit 44. Although the signal is supplied, the switches 61 and 62 and the changeover switches 53X and 54X are not connected to the selection C terminal until the state variable of the band dividing unit 44 is sufficiently updated. For this reason, when there is no usable stereo information and the stereo information is input for the first time after the internal state variable is initialized, the switch 43X is connected to the selection B terminal, and the state of the band dividing unit 44 While updating the variable, the monaural audio signal from the delay unit 46 is output from the output terminals 55 and 56 via the selection A terminals of the changeover switches 53X and 54X. Thereafter, when the state variable of the band dividing unit 44 is sufficiently updated, the switches 61 and 62 are connected to the selection C terminal, and the changeover switches 53X and 54X are switched and connected to the selection C terminal side, as described above. The stereo signal is output from the output terminals 55 and 56 as an output audio signal. Therefore, the output audio signal is not affected by the state in which the state variable of the band dividing unit 44 is initialized, and a stereo audio signal in which the occurrence of abnormal noise or the like is prevented can be obtained.

  That is, in the present invention, stereo information is not input when decoding and reproducing encoded audio data that is transmitted after the stereo information is intermittently multiplexed with the encoded information of a monaural audio signal. In this case, a stereo audio signal using a monaural audio signal is output, and when stereo information is input, update of state variables inside the filter is started, and monaural is performed until all the state variables are updated. When a stereo audio signal using an audio signal is output and all the state variables in the filter are updated, the stereo audio signal is generated by performing stereo processing based on the stereo information on the monaural audio signal. I am trying to output.

  Next, the present invention is used to reproduce the above-mentioned HEAAC (High Efficiency Advanced Audio Coding, International Standard ISO / IEC 14496-3), particularly the encoded audio data encoded by the encoding method of HE AAC v2 (version 2). A configuration example of a playback apparatus to which the invention is applied will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 9 described above are denoted by the same reference numerals.

  The input terminal 11 in FIG. 2 includes coding information of the AAC core, high-frequency generation coding information (band extension coding information for SBR processing), and PS coding information (spatial information for stereo). The encoded audio data bit stream (Coded Audio Stream) is transmitted and input, and a part of the encoded information is multiplexed and transmitted. That is, as described in conjunction with FIG. 8 above, the encoding information SD (SBR data) for the SBR processing is always multiplexed with respect to the encoding information AC of the AAC core, whereas this SD ( SH (SBR header) required for decoding (SBR data) is intermittently multiplexed. The PS data for the PS process is included in the SD (SBR data) extension area and transmitted, and the SH (SBR header) is required to obtain the PS data. The header) is information necessary for stereo.

  In addition, when high frequency band encoded information (SBR data) and PS encoded information (PS data) are included, the audio signal decoded by the AAC core decoding unit (AAC Core Coder) 13 is the final output audio signal. Since the data is output at the half sampling rate, the upsampling is performed by combining the QMF analysis (Analysis) unit 21 and the QMF synthesis (Synthesis) units 33 and 34. For example, when the output signal of the AAC core decoding unit 13 has a sampling frequency of 24 kHz, the output audio signal from the QMF synthesis units 33 and 34 is a signal having a sampling frequency of 48 kHz.

  The encoded audio data (Coded Audio Stream) from the input terminal 11 is sent to a payload deformer (Bitstream Payload Deformatter) 12, and AAC core encoded information to the AAC core decoding unit 13 and high frequency generation encoded information Separated into PS encoded information.

  The high frequency band generation encoded information / PS encoded information is sent to the SBR processing unit 20, and is sent to the Huffman decoding / inverse quantization unit 15 via the parser (Bitstream Parser) 14 of the SBR processing unit 20. The frequency signal generation information, the envelope adjustment information, and the stereo information are extracted and sent to the units 23 and 24, and also sent to the stereo processing unit 30 via the Lch duplication process determination unit 16. The parser 14 of the SBR processing unit 20 acquires multiplexing information such as high-frequency generation encoded information from the payload deformator 12, confirms the contents, and determines whether or not initialization of the SBR processing is necessary. When initialization is required, an initialization control signal is output from the terminal 14t, and SBR processing of each unit is initialized as will be described later. Also, the Lch duplication process determination unit 16 determines that the encoded information is multiplexed for the first time after the initialization of the SBR process, outputs a determination output from the terminal 16t, and outputs an Lch QMF synthesis unit 33 to be described later. The state variable (delayed signal) of the Rch is copied to the Rch QMF synthesizer 34.

  The AAC core decoding unit 13 decodes the input AAC core encoded information and generates an AAC core monaural audio signal. The generated monaural audio signal is sent to the QMF analysis unit 21 of the SBR processing unit 20 to divide the band into 64 bands, and is sent to the changeover switch 22X. When high-frequency generation encoded information (SBR data) is input, the changeover switch 22X is switched and connected to the selection B and C terminals, and the signal from the QMF analysis unit 21 is input to the high-frequency generation unit (HF Generator) 23. Sent. The high-frequency generator 23 generates a high-frequency signal, performs envelope adjustment with an envelope adjuster 24, and sends it to a hybrid analysis unit 27 and a changeover switch 35X.

  When the stereo information is obtained from the PS encoded information (PS data), the changeover switch 22X is switched and connected to the selection C terminal. The hybrid analysis unit 27 further divides the low-frequency signal of the input band-divided signal, and together with the high-frequency signal of the input band-divided signal, a signal analysis (De-correlate) unit 29 and a stereo processing unit (Stereo Processing) unit Enter 30. The signal analysis unit 29 analyzes the input signal, adjusts the sound, and inputs the input signal to the stereo processing unit 30. The stereo processing unit 30 generates stereo left and right channel signals from the input band-divided signal and the stereo information. The generated stereo channel signals are sent to the hybrid synthesis units 31 and 32 of the respective channels via the switches 17 and 18, respectively. The hybrid synthesis units 31 and 32 synthesize the bands divided by the hybrid analysis unit 27. The signal from the hybrid synthesizing unit 31 is sent to the QMF synthesizing unit 33 and the changeover switch 19 via the changeover switch 35X, and the signal from the hybrid synthesizing unit 32 is sent to the QMF synthesizing unit 34 via the changeover switch 19. Sent. The QMF synthesis units 33 and 34 for each channel synthesize the bands divided by the QMF analysis unit 21 to generate output audio signals of stereo left and right channels (Lch, Rch). The Lch audio signal from the QMF synthesizing unit 33 is sent to the changeover switch 36X and the output terminal 37. The Rch audio signal from the QMF synthesizing section 34 is sent to the changeover switch 36X, and one of the signals from the QMF synthesizing section 33 is selected and sent to the output terminal 38.

  2 is controlled by control means (not shown) in accordance with the contents of the input encoded information, the state of each part, and the like.

  The playback device shown in FIG. 2 is different from the configuration of the playback device shown in FIG. 9 in that the switch configuration at the rear stage of the QMF analysis unit 21 and the switch configuration at the rear stage of the envelope adjustment unit 24 are changed. 18 and the changeover switch 19 are added, and the state variables of the QMF synthesis units 33 and 34 are duplicated.

  The case where encoded audio data is input from an arbitrary frame (transmission unit) as described above in the playback apparatus of FIG. 2 will be described. For example, when input starts from the position of transmission unit # 2 in FIG. 8 above, SH (SBR header), which is information necessary for stereoization of transmission unit # 0, is not input. Since SD (SBR data) cannot be decoded, usable stereo information (PS data) cannot be obtained, and the QMF analysis unit 21, the hybrid analysis unit 27, the QMF synthesis units 33 and 34 of the internal SBR processing unit 20, etc. The state variable (delay signal) is initialized. Next, when data at the position of transmission unit # 5 in FIG. 8 is input and SH (SBR header), which is information necessary for stereoization, is supplied, SD (SBR data) is decoded and usable. Stereo information (PS data) is obtained, and state variables (delayed signals) such as the QMF analysis unit 21, the hybrid analysis unit 27, and the QMF synthesis units 33 and 34 of the internal SBR processing unit 20 are updated. This state variable (delayed signal) is data (signal) held in the delay element in the filter. In the filter processing, a delay is caused between the input and output of the signal according to the filter length. Means this delayed signal.

  Here, in a state where usable stereolization information (PS data) is not obtained and the internal state variables are initialized, the changeover switches 22X, 35X, and 36X are switched and connected to the selection A terminal side. At this time, the monaural audio signal from the AAC core decoding unit 13 is band-divided by the QMF analyzing unit 21 and band-combined by the Lch QMF synthesizing unit 33, and the same audio signal is output for both Lch and Rch.

  Next, when the multiplexed encoded information is transmitted, each changeover switch 22X, 35X, 19, 36X is switched and connected to the selection B, C terminals. In this case, the selection B terminal is switched and connected only when the band extension encoded information is included, and the selection C terminal is switched and connected when the band extension encoded information (high band generation information) and the stereo information are included.

  Hereinafter, a case where SD (SBR data) is decoded and stereo information (PS data) can be obtained by transmitting SH (SBR header), which is information necessary for stereo, will be described. When coding information (SBR data) and stereo information (PS data) for SBR processing are obtained, a signal is first sent to the Rch QMF synthesizer 34. For this reason, if an output audio signal is generated without worrying about the state variable (delayed signal), the initialization signal of the state variable is output to the Rch audio signal, causing abnormal noise. Therefore, in the embodiment of the present invention, at this timing, the state variable (delayed signal) of the Lch QMF synthesizing unit 33 is converted into the Rch of the Rch by the state variable duplication processing by the judgment output from the Lch duplication processing judgment unit 16. Copy to the QMF synthesis unit 34. By this operation, the state variable equivalent to the state variable of the Lch QMF synthesizing unit 33 is changed to the Rch QMF synthesizing unit even though it is reproduced while being connected to the selection A terminal until the stereo information is transmitted. 34. When the duplication process is executed, the changeover switches 22X, 35X, 19, 36X are connected to the selection F terminal.

  Usually, when an unrelated appropriate signal is used as a delay signal in the band synthesis process, unintended amplification attenuation is performed in the band synthesis process, which may cause abnormal noise. In the method of the present embodiment, since the output is the point at which the output is switched from monaural to stereo in the frame in which the multiplexed encoded information is obtained for the first time after initialization, the state variables (delays) of the Rch QMF synthesis unit 34 Even if the state variable (delayed signal) of the Lch QMF synthesizer 33 is used as the signal), no abnormal noise is generated.

  Further, in the stereo processing (PS processing), in order to apply spatial coding information, band division by the hybrid analysis unit 27, stereo signal generation processing based on the analysis result by the signal analysis unit 29 and the transmitted spatial information, and hybrid Perform synthesis. Since the hybrid analysis unit 27 that requires delay is also processed for the first time after decoding the encoded information, the state variable (delay when the encoded information is obtained for the first time after the decoding internal variable is initialized) Signal) is initialized, affects the analysis of the signal analysis unit 29, and causes abnormal noise. That is, the signal divided by the QMF analysis unit 21 is input to the hybrid analysis unit 27, but the state variable (delayed signal) of the hybrid analysis unit 27 is in an initialized state, so that subsequent processing is not performed correctly. .

  Therefore, in the present embodiment, in order to eliminate this influence, when the hybrid analysis unit 27 is processed for the first time after initialization, the stereo of the hybrid analysis unit 27 and the stereo processing unit 30 is updated in order to update the delay signal. The left and right channel generation coefficients are updated, and the switches 35X and 19 are switched to the terminal F for output, and the signals branched in front of the hybrid analysis unit 27 are output to the QMF synthesis units 33 and 34 of the respective channels. Yes.

  Specifically, the switches 17 and 18 cut off the stereo signal until the state variable (delayed signal) of the hybrid analyzer 27 is sufficiently updated (both switches 17 and 18 are turned off). A signal transmitted via the selection F terminal of the changeover switches 22X and 35X is sent to the Rch QMF synthesis unit 34 via the Lch QMF synthesis unit 33 and the selection F terminal of the changeover switch 19. A signal from the Lch QMF synthesizing unit 33 is output from the output terminal 37, and a signal from the Rch QMF synthesizing unit 34 having the same state variable as that of the Lch QMF synthesizing unit 33 is output via the selection F terminal of the changeover switch 36X. 38.

  The state variable (delayed signal) of the hybrid analysis unit 27 has a delay of 6QMF samples as specified in Section 8.6.4 of Non-Patent Document 1. The stereo left / right channel generation coefficient update process of the stereo processing unit 30 is necessary because the coefficient is transmitted as difference information as described in Section 8.6.4.4 of Non-Patent Document 1 above. Become.

  When the state variable (delayed signal) of the hybrid analyzer 27 is sufficiently updated, both the switches 17 and 18 are turned on (connected to the selection E terminal), and the stereo left and right channel signals from the stereo processing unit 30 are It is sent to the hybrid synthesis units 31 and 32, respectively. The changeover switches 35X, 19, and 36X are respectively switched and connected to the selection E terminal side, and the signal from the hybrid synthesizing unit 31 is output from the output terminal 37 as a stereo Lch audio signal via the QMF synthesizing unit 33. The signal from the unit 32 is output from the output terminal 38 as a stereo Rch audio signal via the QMF synthesis unit 34. As for the timing at which the switches 17 and 18 and the changeover switches 35X, 19 and 36X are connected to the selection E terminal, the state variable of the Rch QMF synthesis unit 34 is updated even during the state variable update processing of the hybrid analysis unit 27. By doing so, it is possible to switch without generating abnormal noise within one frame processing.

  3 to 5 are flowcharts for explaining the decoding operation as described above in the configuration of FIG.

  In FIG. 3, the HEAAC v2 encoded data decoding process (deformatting process) is performed on the encoded information such as the bit stream of the encoded audio data input to the input terminal 11 in step S101. To extract the high-frequency generation encoded information (SBR data) and spatial encoded information (PS data) as multiplexed encoded information as described above, and for the AAC core information in step S102 To perform AAC signal processing. In the next step S103, it is determined whether or not to perform the SBR process. If YES, the process proceeds to step S104, and if NO, the process proceeds to step S114. These processes correspond to, for example, the processes in the payload formatter 12 and the AAC core decoding unit 13 in FIG.

  In step S104, for example, the QMF analysis unit 21 performs QMF band division processing. In the next step S105, it is determined whether or not the multiplexed encoded information has been decoded. If YES, the process proceeds to step S106, and if NO, the process proceeds to step S113. In step S106, for example, the high frequency generation unit 23 performs high frequency signal generation processing using multiplexed high frequency generation encoded information (multiplexed decoding information), and in the next step S107. It is determined whether or not PS processing is performed.

  When YES is determined in step S107 (PS process is performed), the PS process is performed in step S120, and then the process proceeds to step S111. When NO is determined in step S107 (PS process is not performed), the process directly proceeds to step S111. Proceed to A specific example of the PS process in step S120 will be described later with reference to FIG. 4 or FIG.

  In step S111, an Lch QMF band synthesis process is performed. In step S112, an Rch QMF band synthesis process is performed, and the obtained audio signal is output. In step S113, Lch QMF band synthesis processing is performed. In step S114, a monaural signal is duplicated as necessary to generate a stereo signal, and the obtained audio signal is output. These processes correspond to, for example, the processes performed by the changeover switches 35X and 36X and the QMF combining units 33 and 34 shown in FIG.

  FIG. 4 shows a specific example of the PS process in step S120 according to the embodiment of the present invention. When YES is determined in step S107 in FIG. 3 (PS process is performed), the process proceeds to step S108 and the hybrid process is performed. An analysis process is performed, a stereo signal generation process based on spatial information is performed in step S109, a hybrid synthesis process is performed in step S110, and then the process proceeds to step S115. In step S115, it is determined whether or not the state variable (delay signal) of the Rch QMF band synthesis process, for example, the state variable of the QMF synthesis unit 34 in FIG. 2, has been updated. If YES, the process proceeds to step S111 in FIG. If NO, the process proceeds to step S116. In step S116, after the state variable of the Lch QMF band synthesis process is copied to the state variable of the Rch QMF band synthesis process, the process proceeds to step S111 of FIG. These processes correspond to, for example, the processes from the hybrid analysis unit 27 to the QMF synthesis units 33 and 34 in FIG.

  In the specific examples shown in FIG. 3 and FIG. 4, the internal state of the playback device is changed when the encoded audio data transmitted by multiplexing a part of the encoded information is reproduced from an arbitrary frame. Even when there is no encoded information to be transmitted after being initialized and multiplexed, it is divided into at least two or more subbands, and a monophonic audio signal is output by performing upsampling by a band synthesis filter process in which a delay occurs. Thereafter, when the multiplexed encoded information is input and processing for generating a stereo signal from the monaural signal first is performed, the filter state variable (delayed signal) of the monaural signal is processed as the filter state variable of the stereo signal. (Steps S114, S115, and S116) prevents the generation of abnormal noise in the output audio signal due to the delay of the filter processing. It is.

  Next, FIG. 5 shows another specific example of the PS process in step S120 of FIG. 3 of the embodiment of the present invention. That is, when it is determined YES in Step S107 in FIG. 3 (PS processing is performed), the process proceeds to Step S108 in FIG. 5 and the hybrid analysis processing (for example, processing in the hybrid analysis unit 27 in FIG. 2) is performed. In step S119, it is determined whether all the state variables (delay signals) of the hybrid analysis process have been updated. If YES, the process proceeds to step S109. If NO, the process proceeds to step S117. In step S109, a stereo signal generation process based on spatial information is performed. After a hybrid synthesis process is performed in step S110, the process proceeds to step S115. In step S117, since all the state variables of the hybrid analysis process have not yet been updated, a signal obtained by duplicating the monaural signal to generate a stereo signal is used as an output of the hybrid synthesis process. After updating, it progresses to step S115.

  In step S115, it is determined whether or not the state variable of the Rch QMF band combining process (for example, the state variable of the QMF combining unit 34 in FIG. 2) has been updated. If YES, the process proceeds to step S111 in FIG. If so, the process proceeds to step S116. In step S116, the state variable of the Lch QMF band synthesis process is copied to the state variable of the Rch QMF band synthesis process, and the process proceeds to step S111 of FIG.

  In the specific examples shown in FIGS. 3 and 5, in addition to the configuration of the specific example described in conjunction with FIG. 4, the delay of the filter processing does not affect the output audio signal as shown in steps S119, S117, and S118. Thus, at least until all the filter state variables (delayed signals) are updated, the filter state variable update process and the output signal duplication process are performed, and after the filter state variable has been sufficiently updated, Thus, the generation of abnormal sound in the output audio signal due to the delay of the filter processing is prevented.

  Examples of output audio signals of the stereo left and right channels (Lch, Rch) in the embodiment of the present invention are shown in FIGS. About each time t1-t3, it is the same as that of description of (A) of FIG. 11 mentioned above, and (B). That is, there is no usable stereoization information until time t1 (for example, only an AAC-LC (Low Complexity) encoded information signal is input, and the SBR process is performed only up-sampling). At time t1, the multiplexed encoded information including the stereo information becomes valid (usable), and the AAC process, the SBR process, and the PS process are started. 11C shows an output audio signal of Lch and FIG. 11D shows an output audio signal of Rch, respectively.

  The output audio signals (C) and (D) of the stereo left and right channels in the embodiment of the present invention shown in FIG. 11 are time t1 as apparent from comparison with the conventional output audio signals (A) and (B). The influence of the state variable (delayed signal) of the band synthesizing unit (QMF synthesizing unit 34) for the SBR processing between t2 and t2 is also affected by the hybrid filter (hybrid analyzing unit) for the PS processing between times t2 and t3 27), the influence of the state variable does not appear, and according to the embodiment of the present invention, encoded information (stereo information, etc.) multiplexed for the first time from the state in which the internal state variable is initialized. Even when input, it is possible to reproduce a good stereo audio signal without occurrence of abnormal noise.

  The embodiment of the present invention described above is used when decoding and reproducing encoded audio data in which a part of encoded information including stereo information is multiplexed and transmitted to a monaural audio signal. The internal state variable (delayed signal) is initialized in a state where the multiplexed encoded information that is possible is not input, and a stereo audio signal using a monaural audio signal is output, and the internal state variable is initialized. When the multiplexed encoded information is input in the recorded state, update of the internal state variable is started, and the stereo audio signal using the monaural audio signal is updated until all the state variables are updated. When all of the internal state variables are updated, a scan based on the multiplexed encoded information for the monaural audio signal is performed. Performs signal processing including Leo process generates and outputs a stereo audio signal.

  That is, when stereo information is not input when decoding and reproducing encoded audio data that is transmitted after the stereo information is intermittently multiplexed with the encoded information of the monaural audio signal, the monaural audio signal is input. When stereo information is input, update of the state variable inside the filter is started, and the monaural audio signal is used until all the state variables are updated. When the stereo audio signal is output and all the state variables in the filter are updated, the stereo audio processing is performed on the monaural audio signal based on the stereo information, and the stereo audio signal is generated and output.

  According to another embodiment of the present invention, a decoding unit for encoded audio data in which a part of encoded information is multiplexed and transmitted, and a case in which a part of the multiplexed encoded information is not transmitted However, a means for obtaining information for generating an output audio signal from a part of the transmitted encoded information, an audio signal band dividing means for generating a band division signal by dividing the information into at least two or more bands, and A means for generating high frequency information by transmitting band extension coding information to the band division signal, and a delay for the band division signal by transmitting spatial coding information. Means for generating a subband division signal by means of the subband division signal generation means, generating a stereo signal from the monaural signal based on the spatial coding information, and a subband division signal combination for synthesizing the subband division signal into the band division signal. A coded audio data reproducing apparatus comprising: a means for synthesizing the synthesized band-divided signal by an audio signal synthesizing means that requires a delay, and generating an output audio signal; The subband signal generating means that requires a delay of the encoded audio data reproducing apparatus, the means for initializing the state variable (delayed signal) of the audio signal synthesizing means, and the reproduction is continued after the initialization. And, when the encoded information multiplexed for the first time is transmitted after the initialization and the spatial encoding information is decoded to generate the stereo signal from the monaural signal, the audio signal synthesis means of the generated stereo signal Means for processing using a state variable (delayed signal) of a monaural signal as a state variable (delayed signal).

  In addition, when the encoded signal that has been multiplexed is transmitted for the first time after the delay signal initialization of such an encoded audio data reproducing apparatus, the spatially encoded information is decoded and a stereo signal is generated from the monaural signal. Until the state variable (delayed signal) of the sub-band division signal generation means is all updated, the sub-band division signal generation means for pseudo-subband generation to update the state variable (delay signal) While the band division signal generation means is operating, the means for replicating the monaural band division signal input to the sub band division signal generation means and outputting it as a stereo band division signal to the audio signal synthesis means, In particular, while the subband division signal generating means is operating, means for updating the division coefficient updated by the difference between the means for generating the stereo signal from the monaural signal, and the subband division signal generation And means for generating a stereo signal from the mono signal based on spatial coded information after the delayed signal means is all updated.

  That is, in the decoding process of the encoded audio data that is transmitted by multiplexing a part of the encoded information, the delay signal of the decoder is initialized and multiplexed when performing normal reproduction from an arbitrary frame. Even when there is no encoded information to be transmitted, it can be divided into at least two bands and up-sampled by band synthesis filter processing that requires a delay to duplicate the monaural audio signal and output it as a stereo audio signal When the encoded information is transmitted for the first time and the spatial decoding process is enabled, the delay signal of the monaural signal audio signal band synthesis process is processed as the delay signal of the audio signal band synthesis process of the stereo signal. The generation of abnormal noise in the output audio signal due to the delay of the synthesis filter processing is prevented.

  In addition, delay signal update processing and output signal duplication processing are performed at least until all the delayed signals of the subband division filter processing are updated so that the delay of the subband division filter processing does not affect the output audio signal. After all the delayed signals have been updated, normal reproduction processing is performed, so that no abnormal noise is generated in the output audio signal due to the delay of the filter processing.

  As a result, even encoded audio data having a spatial decoding process in which a part of the encoded information is multiplexed and transmitted can be reproduced from an arbitrary position without generating any abnormal sound.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment of the present invention, the playback apparatus or the playback method having a hardware configuration has been described. However, the above-described processing of each process is realized by software, that is, a CPU (Central Processing Unit) is installed. It can be realized by causing the computer to execute the program, and the computer program can be recorded on a recording medium and provided.

It is a block diagram which shows schematic structure of the reproducing | regenerating apparatus used as embodiment of this invention. It is a block diagram which shows the structural example which applied embodiment of this invention to the reproducing | regenerating apparatus of the encoding audio data encoded by the HE AAC v2 system. 3 is a flowchart for explaining the operation of the playback apparatus shown in FIG. It is a flowchart for demonstrating one specific example of PS process of step S120 of FIG. It is a flowchart for demonstrating the other specific example of PS process of FIG.3 S120. It is a block diagram which shows the structural example of the conventional stereo-ized apparatus. It is a figure which shows an example of the signal input into the stereophonic apparatus of FIG. It is a figure which shows an example of the signal input into the stereo conversion apparatus of HE AAC v2. It is a block diagram which shows the structural example of the reproducing | regenerating apparatus of the encoding audio data encoded by the HE AAC v2 system. 10 is a flowchart for explaining the operation of the playback apparatus shown in FIG. 9. It is a wave form diagram which contrasts the output audio signal of the conventional reproducing | regenerating apparatus, and the output audio signal of the reproducing | regenerating apparatus to which embodiment of this invention was applied.

Explanation of symbols

  11 Input terminal for encoded audio data, 21 QMF analyzer, 23 High frequency generator, 27 Hybrid analyzer, 30, 45 Stereo processing unit, 31, 32 Hybrid combiner, 33, 34 QMF combiner, 44 Band division Part, 51, 52 Band synthesis part

Claims (8)

In a reproduction method for decoding and reproducing encoded audio data transmitted by intermittently multiplexing information required for stereo processing and encoded information of a monaural audio signal,
A first step of outputting a stereo audio signal using a monaural audio signal when the stereo-necessary information is not input;
A second step of starting to update a state variable inside the filter and outputting a stereo audio signal using a monaural audio signal until all of the state variables are updated when the stereo-necessary information is input;
When all the state variables in the filter are updated, the stereo audio signal is generated and output by performing a stereo process based on the stereo information obtained from the stereo necessary information on the monaural audio signal. 3. A reproduction method comprising the steps of:   2. The reproduction method according to claim 1, wherein the stereo process is performed on a monaural audio signal whose band has been extended. In the first step, the monaural audio signal is divided into at least two or more subbands by band division filter processing, up-sampled by band synthesis filter processing, and a stereo audio signal using the monaural audio signal is output.
3. The reproduction method according to claim 2, wherein in the second step, a state variable inside the filter of the monaural audio signal is processed as a filter state variable of the stereo audio signal.   The encoded audio data includes AAC core encoding information corresponding to monaural audio data in HE AAC (High Efficiency Advanced Audio Coding) encoding scheme, SBR (Spectral Band Replication) processing encoding information, PS ( The encoded information of the SBR process includes an SBR header (sbr header) that is encoded information that is multiplexed and transmitted intermittently, and an encoded information that is always transmitted. PS data (ps data) that is encoded information of the PS processing is transmitted by being included in an extension area of the SBR data, and the SBR header is the SBR header. 4. The reproduction method according to claim 3, wherein the information necessary for stereoization is required for decoding data. In a playback apparatus for decoding and reproducing encoded audio data that is transmitted by multiplexing and transmitting information required for stereo processing that is intermittently multiplexed with encoded information of a monaural audio signal,
Band dividing means for dividing the input monaural audio signal into bands;
Stereo processing means for performing a stereo process on the signal from the band dividing means based on the stereo information included in the multiplexed encoded information;
Band synthesizing means for synthesizing the left and right stereo channel signals from the stereo processing means;
When the stereo necessary information is not input, control is performed to output a stereo audio signal using a monaural audio signal. When the stereo necessary information is input, updating of a state variable in the filter is started. Controls to output a stereo audio signal using a monaural audio signal until all the state variables are updated. If all the state variables in the filter are updated, the stereo audio is required for the monaural audio signal. And a control unit configured to perform a stereo process based on the stereo information obtained from the information to generate and output a stereo audio signal.   6. The playback apparatus according to claim 5, wherein the stereo process is performed on a monaural audio signal whose band has been extended. A program for causing a computer to execute a process of decoding and reproducing encoded audio data transmitted by intermittently multiplexing information required for stereo processing and encoded information of a monaural audio signal. In
A first step of outputting a stereo audio signal using a monaural audio signal when the stereo-necessary information is not input;
A second step of starting to update a state variable inside the filter and outputting a stereo audio signal using a monaural audio signal until all of the state variables are updated when the stereo-necessary information is input;
When all the state variables in the filter are updated, the stereo audio signal is generated and output by performing a stereo process based on the stereo information obtained from the stereo necessary information on the monaural audio signal. A program characterized by comprising the steps of 3. A program for causing a computer to execute a process of decoding and reproducing encoded audio data transmitted by intermittently multiplexing information required for stereo processing and encoded information of a monaural audio signal. In the recording medium recorded with
The above program
A first step of outputting a stereo audio signal using a monaural audio signal when the stereo-necessary information is not input;
A second step of starting to update a state variable inside the filter and outputting a stereo audio signal using a monaural audio signal until all of the state variables are updated when the stereo-necessary information is input;
When all the state variables in the filter are updated, the stereo audio signal is generated and output by performing a stereo process based on the stereo information obtained from the stereo necessary information on the monaural audio signal. 3. A recording medium comprising the steps of 3.

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