WO2010137300A1 - 復号装置及び復号方法 - Google Patents
復号装置及び復号方法 Download PDFInfo
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- WO2010137300A1 WO2010137300A1 PCT/JP2010/003496 JP2010003496W WO2010137300A1 WO 2010137300 A1 WO2010137300 A1 WO 2010137300A1 JP 2010003496 W JP2010003496 W JP 2010003496W WO 2010137300 A1 WO2010137300 A1 WO 2010137300A1
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/005—Correction of errors induced by the transmission channel, if related to the coding algorithm
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/008—Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
Definitions
- the present invention particularly relates to a decoding apparatus and a decoding method used in a communication system that encodes and transmits a signal and receives and decodes the encoded signal.
- an encoding technique for a two-channel signal (stereo signal) of a left channel signal (hereinafter referred to as “L signal”) and a right channel signal (hereinafter referred to as “R signal”) is M / S (Middle). / Side)
- L signal left channel signal
- R signal right channel signal
- M / S Right channel signal
- a stereo encoding system or an intensity stereo encoding system can be cited as an existing technique.
- the M / S encoding method will be briefly described.
- a two-channel signal of an L signal and an R signal is converted into a sum signal (hereinafter referred to as “M signal”) of the L signal and the R signal, and a difference signal between the L signal and the R signal ( (Hereinafter referred to as “S signal”) to generate a signal from which the correlation between channels is removed.
- M signal a sum signal
- S signal a difference signal between the L signal and the R signal
- a signal from which the correlation between channels is removed is encoded.
- a technique called a parametric stereo coding method that uses the correlation between two channel signals of L signal and R signal.
- L channel and R channel 2 channel signals are represented by 1 channel signal and parameters representing the relationship between channels, and 1 channel signal and channel expansion parameters are encoded. To do.
- Patent Document 1 discloses a technique for suppressing abnormal noise due to a sudden change in the number of channels in a decoded signal when a frame loss occurs due to a transmission error or the like in a parametric encoding method for a multi-channel signal. Yes. Specifically, in Patent Document 1, when a frame loss occurs, a process of generating a replacement signal for an erroneous part is performed based on a stored parameter related to a past error-free signal. Further, Patent Document 1 discloses a process for applying stepwise muting of model parameters when a missing frame continues for a long time.
- Patent Document 1 does not disclose a sound quality deterioration suppression process at the time of frame loss for an M / S encoding method that is a non-parametric encoding / decoding method, and still has no frame in the M / S encoding method. There is a problem that the sound quality deteriorates when it disappears. Further, in Patent Document 1, since compensation processing is performed at a parameter level for an erroneous frame, spatial characteristics other than those parameters cannot be compensated with high accuracy, and performance for suppressing sound quality deterioration is insufficient. There is a problem that there is. Further, in Patent Document 1, there is a problem that fine muting cannot be performed in units of samples because stepwise muting at the parameter level results in muting processing for each frame.
- An object of the present invention is to reduce the number of channels in a decoded signal when a transmission error occurs due to frame loss in a method for encoding / decoding a multi-channel signal such as an M / S encoding / decoding method. It is an object to provide a decoding device and a decoding method that can reduce fluctuations, can be smoothed in units of samples, and can suppress deterioration in sound quality.
- the decoding apparatus includes an encoded monaural signal obtained by encoding a monaural signal calculated from a first channel signal and a second channel signal constituting a stereo signal, and the first channel signal and the second channel signal.
- a receiving means for receiving an encoded differential signal obtained by encoding a differential signal, a detecting means for detecting a temporal change in the received encoded differential signal, and a decoded monaural signal obtained by decoding the received encoded monaural signal And decoding the received encoded differential signal to obtain a decoded differential signal, and smoothing the decoded differential signal by calculating the decoded differential signal and a coefficient corresponding to the detected temporal change. Smoothing means for performing a decoding process; and a calculating means for calculating a decoded stereo signal from the decoded monaural signal and the decoded differential signal that has been smoothed.
- the decoding method of the present invention includes an encoded monaural signal obtained by encoding a monaural signal calculated from a first channel signal and a second channel signal constituting a stereo signal, and the first channel signal and the second channel signal.
- decoding the received encoded differential signal to obtain a decoded differential signal, and performing a smoothing process on the decoded differential signal by calculating the decoded differential signal and a coefficient corresponding to the detected temporal change.
- a step of calculating a decoded stereo signal from the decoded monaural signal and the smoothed decoded differential signal It was so.
- the present invention when a transmission error due to frame loss occurs in a method for encoding / decoding a multi-channel signal such as an M / S encoding / decoding method, the number of abrupt channels in the decoded signal is increased. While fluctuation can be reduced, smoothing can be performed in units of samples, and deterioration of sound quality can be suppressed.
- FIG. 1 is a block diagram showing a configuration of an encoding apparatus according to Embodiment 1 of the present invention.
- the block diagram which shows the structure of the decoding apparatus which concerns on Embodiment 1 of this invention.
- the flowchart which shows operation
- the block diagram which shows the structure of the decoding apparatus which concerns on Embodiment 2 of this invention.
- the flowchart which shows operation
- FIG. 1 is a block diagram showing a configuration of a communication system 100 according to Embodiment 1 of the present invention.
- the communication system 100 mainly includes an encoding device 101, a transmission path 102, and a decoding device 103.
- an encoding device 101 and a decoding device 103 can communicate with each other via a transmission path 102.
- both the encoding apparatus 101 and the decoding apparatus 103 are normally mounted and used in a base station apparatus or a communication terminal apparatus. Each configuration will be described in detail below.
- the encoding apparatus 101 will be described by taking as an example a configuration in which an L signal and an R signal, which are input signals, are each encoded by a CELP (Code Exit Exit Linear Prediction) method.
- the encoding apparatus 101 acquires the encoded information by encoding the L signal and the R signal, and transmits the acquired encoded information to the decoding apparatus 103 via the transmission path 102. Details of the configuration of the encoding apparatus 101 will be described later.
- the decoding apparatus 103 receives the encoded information transmitted from the encoding apparatus 101 via the transmission path 102, decodes the received encoded information, and acquires the decoded L signal and decoded R signal that are output signals. Note that the decoding apparatus 103 will be described by taking as an example a configuration in which decoding is performed by a CELP decoding method, similar to the encoding apparatus 101. Details of the configuration of the decoding apparatus 103 will be described later.
- FIG. 2 is a block diagram showing the configuration of the encoding apparatus 101.
- the encoding apparatus 101 mainly includes an M / S signal calculation unit 201, an M signal encoding unit 202, an S signal encoding unit 203, and an encoded information integration unit 204.
- the encoding device 101 receives an L signal and an R signal of two channels, converts the input L signal and R signal into an M signal and an S signal, and then encodes the M signal and the S signal respectively. Get encoding information. Then, the encoding apparatus 101 integrates the acquired encoded information by the encoded information integration unit 204 and transmits the integrated encoded information to the decoding apparatus 103. Each configuration will be described in detail below.
- the M / S signal calculation unit 201 inputs the L signal and the R signal, and calculates a sum signal (M signal) and a difference signal (S signal) according to the equations (1) and (2).
- M signal a sum signal
- S signal a difference signal
- i in the expressions (1) and (2) indicates a sample index in the frame
- N indicates a frame size.
- the M / S signal calculation unit 201 outputs the M signal calculated by the equation (1) to the M signal encoding unit 202, and outputs the S signal calculated by the equation (2) to the S signal encoding unit 203. .
- the M signal encoding unit 202 receives the M signal from the M / S signal calculation unit 201, encodes the M signal using a CELP speech encoding method, and calculates M encoded information. Then, the M signal encoding unit 202 outputs the calculated M encoded information to the encoded information integration unit 204.
- the S signal encoding unit 203 receives the S signal from the M / S signal calculation unit 201, encodes the S signal using a CELP speech encoding method, and calculates S encoded information. Then, the S signal encoding unit 203 outputs the calculated S encoded information to the encoded information integration unit 204. Since the CELP speech encoding method is an existing technology, a detailed description thereof will be omitted.
- the encoded information integration unit 204 receives the M encoded information from the M signal encoding unit 202 and the S encoded information from the S signal encoding unit 203, and inputs the input S encoded information and the M encoded information. Are integrated into encoded information. Then, the encoded information integration unit 204 outputs the obtained encoded information to the transmission path 102. This is the end of the description of the configuration of the encoding apparatus 101.
- FIG. 3 is a block diagram illustrating a configuration of the decoding device 103.
- the decoding apparatus 103 mainly includes a separation unit 301, an M signal decoding unit 302, an S signal decoding unit 303, a smoothing processing unit 304, and an L / R signal calculation unit 305.
- the decoding apparatus 103 receives the encoded information transmitted from the encoding apparatus 101 via the transmission path 102, decodes this using the M / S decoding method, and calculates a decoded L signal and a decoded R signal. Then, decoding apparatus 103 outputs the calculated decoded L signal and decoded R signal as 2-channel output signals. Each configuration will be described in detail below.
- Separation section 301 separates encoded information input from encoding apparatus 101 via transmission path 102 into M encoded information and S encoded information, and outputs the separated M encoded information to M signal decoding section 302 Then, the separated S encoded information is output to the S signal decoding unit 303. Separation section 301 detects the presence or absence of transmission errors in the input encoded information. Further, when the transmission unit 301 detects a transmission error, the separation unit 301 detects a temporal change in information included in the input encoded information. Then, the separation unit 301 outputs the detected temporal change to the smoothing processing unit 304 as the smoothing processing control information CI.
- the separating unit 301 detects whether or not S encoded information is included in the encoded information input from the encoding apparatus 101 via the transmission path 102. In addition, the separation unit 301 indicates when the frame that includes the S encoded information is switched to a frame that is not included, and when the frame that does not include the S encoded information is switched to a frame that is included. To detect. In addition, when the separation unit 301 detects a time point when the frame including the S encoded information is switched to the frame not including the S encoded information, the separating unit 301 sets the value of the smoothing process control information CI to 1.
- the separation unit 301 detects the time point when the frame is switched from the frame not including the S encoded information to the included frame, the separating unit 301 sets the value of the smoothing process control information CI to 2.
- the separation unit 301 includes a time point when the frame that includes the S encoding information is switched to a frame that is not included, and a point when the frame that does not include the S encoded information is switched to a frame that is included. If neither is detected, the value of the smoothing process control information CI is set to zero.
- the M signal decoding unit 302 receives the M encoded information from the separating unit 301, decodes the input M encoded information by a CELP speech decoding method, and calculates a decoded M signal.
- the speech decoding method in the M signal decoding unit 302 is a method corresponding to the encoding method in the M signal encoding unit 202 in the encoding apparatus 101.
- the M signal decoding unit 302 outputs the calculated decoded M signal to the L / R signal calculation unit 305.
- the S signal decoding unit 303 receives the S encoded information from the separation unit 301, decodes the input S encoded information by a CELP speech decoding method, and calculates a decoded S signal.
- the speech decoding method in S signal decoding section 303 is a method corresponding to the encoding method in S signal encoding section 203 in encoding apparatus 101. Further, the S signal decoding unit 303 outputs the obtained decoded S signal to the smoothing processing unit 304.
- the S signal decoding unit 303 includes the S encoding included in the frame immediately before the current frame (for example, the frame one frame before the current frame).
- a decoded S signal is calculated by decoding the information.
- the S signal decoding unit 303 stores the S encoded information or the decoded S signal in the current frame in an internal buffer, and updates the internal buffer for each frame process.
- the method for compensating the S signal by the above-described method is described as the compensation processing at the time of frame loss such as a transmission error.
- the present embodiment is not limited to this, and other than this method The same applies to the frame erasure compensation processing.
- the CELP speech decoding method is an existing technology, its detailed description is omitted.
- the smoothing processing unit 304 receives the decoded S signal from the S signal decoding unit 303 and the smoothing processing control information CI from the separation unit 301.
- the smoothing processing unit 304 performs time-dependent attenuation or amplification processing on the decoded S signal in accordance with the value of the smoothing processing control information CI, and smoothes the decoded S signal (hereinafter, “smoothed decoding S”). Signal)).
- the smoothing processing unit 304 is a coefficient that gradually attenuates with respect to the decoded S signal according to equation (3). To calculate a smoothed decoded S signal.
- the smoothing processing unit 304 multiplies the decoded S signal by a coefficient that gradually amplifies in accordance with the equation (4), A smoothed decoded S signal is calculated. Further, when the value of the smoothing processing control coefficient CI is 0, the smoothing processing unit 304 uses the decoded S signal as it is as a smoothed decoded S signal without multiplying anything.
- ⁇ 1 i in the equation (3) is an attenuation coefficient that decreases as i increases
- ⁇ 1 i is an amplification coefficient that increases as i increases.
- the smoothing processing unit 304 outputs the calculated smoothed decoded S signal to the L / R signal calculating unit 305.
- the L / R signal calculation unit 305 receives the decoded M signal from the M signal decoding unit 302 and the smoothed decoded S signal from the smoothing processing unit 304. Further, the L / R signal calculation unit 305 performs decoding using the input decoded M signal and smoothed decoded S signal according to the following equations (5) and (6) corresponding to the M / S signal calculation unit 201. Two channel signals of L signal and decoded R signal are calculated.
- the L / R signal calculation unit 305 outputs the decoded L signal and the decoded R signal calculated by the equations (5) and (6) as 2-channel output signals. Above, description of the structure of the decoding apparatus 103 is completed.
- FIG. 4 is a flowchart showing the operation of the decoding apparatus 103.
- the separation unit 301 detects whether or not S encoded information is included in the encoded information, and sets the value (0, 1, 2) of the smoothing process control information CI according to the detection result. (Step ST401).
- M signal decoding section 302 calculates a decoded M signal from the M encoded information
- S signal decoding section 303 calculates a decoded S signal from the S encoded information (step ST402).
- the smoothing processing unit 304 determines whether or not the value of the smoothing processing control information CI is 1 (step ST403).
- step ST403 When the value of the smoothing processing control information CI is 1 (step ST403: YES), the smoothing processing unit 304 multiplies the decoded S signal by a coefficient ⁇ 1 i that gradually decreases over time, A smoothed decoded S signal is calculated (step ST404).
- step ST403 determines whether or not the value of the smoothing process control information CI is 2 ( Step ST405).
- step ST405 When the value of the smoothing process control information CI is 2 (step ST405: YES), the decoded S signal is multiplied by a coefficient ⁇ 1 i that gradually amplifies the decoded S signal and the smoothed decoded S signal is obtained. Calculate (step ST406).
- step ST405: NO When the value of the smoothing process control information CI is not 2 (step ST405: NO), that is, when the value of the smoothing process control coefficient CI is 0, the decoded S signal is not multiplied by anything. The decoded S signal is smoothed as it is.
- L / R signal calculation section 305 calculates a decoded L signal and a decoded R signal from the calculated decoded M signal and decoded S signal, and outputs the calculated decoded L signal and decoded R signal (step ST407). ).
- a parameter is set. Smoothing processing (smoothing processing) of the number of channels between frames is performed at the signal level instead of the level. As a result, a sudden change in the number of channels in the decoded signal can be reduced, and deterioration in sound quality can be suppressed. Further, according to the present embodiment, smoothing of the number of channels at the signal level enables smoothing in units of samples and further suppresses sound quality degradation.
- the operation of the decoding apparatus 103 has been described using the flow of FIG. 4, but is not necessarily limited to this flow.
- the order of ST403 to ST404 and ST405 to ST406 may be reversed.
- the M / S encoding / decoding method has been described as an example of the multi-channel encoding / decoding method.
- the present invention is not limited to this, and other multi-channel encoding / decoding methods are used. The same applies to the method.
- the attenuation coefficient and the amplification coefficient have been described by taking as an example a configuration in which the attenuation coefficient and the amplification coefficient change from 1 to 0 or from 0 to 1 during one frame processing.
- the present invention is not limited to this.
- the present invention can be similarly applied to the case where the variation of the attenuation coefficient and the amplification coefficient is made slower.
- the attenuation coefficient and the amplification coefficient may be gradually changed from 1 to 0 or from 0 to 1 while the decoding apparatus processes encoded information for several frames.
- the decoding apparatus side stores a frame in which the attenuation process or amplification process for the S signal is started, and slowly changes the attenuation coefficient and the amplification coefficient during a predetermined number of frame processes from that frame.
- the present invention is similarly applied to a decoded S signal that has been compensated by a method other than the above-described compensation processing at the time of transmission error for the decoded S signal that is the target of the smoothing process described in the present embodiment.
- the attenuation described in the present embodiment is applied to a decoded S signal of a frame immediately before a transmission error occurs or a decoded S signal that is attenuated or amplified in time using a parameter for decoding the S signal.
- FIG. 5 is a block diagram showing a configuration of decoding apparatus 500 according to Embodiment 2 of the present invention.
- a decoding apparatus 500 illustrated in FIG. 5 adds an L / R correlation calculation unit 501 to the decoding apparatus 103 according to Embodiment 1 illustrated in FIG. 3, and a smoothing processing unit 502 instead of the smoothing processing unit 304.
- the communication system of the present embodiment has the same configuration as that of FIG. 1 except that it includes a decoding device 500 instead of the decoding device 103, and thus description thereof is omitted.
- the separation unit 301 instead of calculating the smoothing process control information CI in the first embodiment, the first smoothing process control information CI1 is calculated in the present embodiment.
- the decoding apparatus 500 includes a separation unit 301, an M signal decoding unit 302, an S signal decoding unit 303, an L / R correlation calculation unit 501, a smoothing processing unit 502, and an L / R signal calculation unit 305. Configured. Each configuration will be described in detail below.
- the M signal decoding unit 302 receives the M encoded information from the separating unit 301, decodes the input M encoded information by a CELP speech decoding method, and calculates a decoded M signal.
- the speech decoding method in the M signal decoding unit 302 is a method corresponding to the encoding method in the M signal encoding unit 202 in the encoding apparatus 101.
- the M signal decoding unit 302 outputs the calculated decoded M signal to the L / R signal calculation unit 305 and the L / R correlation calculation unit 501.
- the S signal decoding unit 303 receives the S encoded information from the separation unit 301, decodes the input S encoded information by a CELP speech decoding method, and calculates a decoded S signal.
- the speech decoding method in S signal decoding section 303 is a method corresponding to the encoding method in S signal encoding section 203 in encoding apparatus 101.
- the S signal decoding unit 303 outputs the obtained decoded S signal to the L / R correlation calculation unit 501 and the smoothing processing unit 502.
- the S signal decoding unit 303 calculates a decoded S signal by decoding the S encoded information included in the frame immediately before the current frame. To do.
- the S signal decoding unit 303 stores the S encoded information or the decoded S signal in the current frame in an internal buffer, and updates the internal buffer for each frame process.
- the L / R correlation calculation unit 501 receives the decoded M signal from the M signal decoding unit 302 and the decoded S signal from the S signal decoding unit 303. Further, the L / R correlation calculation unit 501 calculates the energy ratio between the L channel and the R channel from the decoded M signal and the decoded S signal as the correlation between the L channel and the R channel, and according to the calculated energy ratio. To determine the second smoothing processing control information CI2. The second smoothing process control information CI2 is calculated by the equation (7). Specifically, the L / R correlation calculation unit 501 has an energy ratio between the L channel and the R channel equal to or higher than the first threshold (TH1) or equal to or lower than the second threshold (TH2: TH2 ⁇ TH1).
- the value of the second smoothing process control information CI2 is set to 1.
- the L / R correlation calculation unit 501 includes the second smoothing process control information CI2 when the energy ratio between the L channel and the R channel is between the first threshold value and the second threshold value. Set the value to 0.
- TH1 and TH2 in the formula (7) are respectively predetermined threshold values. That is, when the energy ratio between the L channel and the R channel is greatly different, the value of the second smoothing process control information CI2 is set to 1. When the energy ratio is not so different, the value of the second smoothing process control information CI2 is set to 0.
- TH1 and TH2 in the formula (7) are respectively predetermined threshold values. That is, when the energy ratio between the L channel and the R channel is greatly different, the value of the second smoothing process control information CI2 is set to 1. When the energy ratio is not so different, the value of the second smoothing process control information CI2 is set to 0. And
- the L / R correlation calculation unit 501 outputs the obtained second smoothing processing control information CI2 to the smoothing processing unit 502.
- the smoothing processing unit 502 receives the decoded S signal from the S signal decoding unit 303, the first smoothing processing control information CI1 from the separation unit 301, and the second smoothing processing from the L / R correlation calculation unit 501.
- the control information CI2 is input. Further, the smoothing processing unit 502 performs attenuation or amplification processing on the time axis on the decoded S signal according to the values of the first smoothing processing control information CI1 and the second smoothing processing control information CI2, and performs smoothing. An encoding / decoding S signal is calculated.
- the smoothing processing unit 502 performs the smoothing processing of the decoded S signal according to the equations (8) and (9).
- ⁇ 2 i in equation (8) is an attenuation coefficient whose value decreases as i increases
- ⁇ 2 i in equation (9) is an amplification coefficient whose value increases as i increases.
- ⁇ 2 i and ⁇ 2 i have smaller amounts of change (amount of change) as i increases than ⁇ 1 i and ⁇ 1 i .
- the smoothing processing unit 502 performs the smoothing processing of the decoded S signal according to the equations (3) and (4). Further, the smoothing processing unit 502 outputs the calculated smoothed decoded S signal to the L / R signal calculating unit 305.
- the L / R signal calculation unit 305 receives the decoded M signal from the M signal decoding unit 302 and the smoothed decoded S signal from the smoothing processing unit 502. In addition, the L / R signal calculation unit 305 calculates two-channel signals of the decoded L signal and the decoded R signal according to the equations (5) and (6) corresponding to the M / S signal calculation unit 201. The L / R signal calculation unit 305 outputs the calculated decoded L signal and decoded R signal as a 2-channel output signal. Above, description of the structure of the decoding apparatus 500 is finished.
- FIG. 6 is a flowchart showing the operation of the decoding device 500.
- the separation unit 301 detects whether or not S encoded information is included in the encoded information, and sets the value (0, 1, 2) of the first smoothing process control information CI1 according to the detection result. Set (step ST601).
- M signal decoding section 302 calculates a decoded M signal from the M encoded information
- S signal decoding section 303 calculates a decoded S signal from the S encoded information (step ST602).
- the L / R correlation calculation unit 501 sets the value (0, 1) of the second smoothing process control information CI2 according to the energy ratio between the L channel and the R channel (step ST603).
- the smoothing processing unit 502 determines whether or not the value of the first smoothing processing control information CI1 is 1 (step ST604).
- step ST604 determines whether or not the value of the second smoothing processing control information CI2 is 0. (Step ST605).
- step ST605 When the value of the second smoothing processing control information CI2 is 0 (step ST605: YES), the smoothing processing unit 502 uses a coefficient ⁇ 1 i that gradually attenuates with respect to the decoded S signal. Multiply and calculate a smoothed decoded S signal (step ST606).
- step ST605 when the value of the second smoothing process control information CI2 is not 0 (step ST605: NO), that is, when the value of the second smoothing process control information CI2 is 1, the smoothing processing unit 502 Then, a smoothed decoded S signal is calculated by multiplying the decoded S signal by a coefficient ⁇ 2 i that gradually attenuates in time more gradually than in step ST606 (step ST607).
- step ST604 when the value of the first smoothing processing control information CI1 is not 1 in step ST604 (step ST604: NO), the smoothing processing unit 502 has the value of the first smoothing processing control information CI1 as 2. It is determined whether or not there is (step ST608).
- step ST608 determines whether or not the value of the second smoothing processing control information CI2 is 0. (Step ST609).
- step ST609 When the value of the second smoothing processing control information CI2 is 0 (step ST609: YES), the smoothing processing unit 502 uses a coefficient ⁇ 1 i that gradually amplifies the decoded S signal over time. To obtain a smoothed decoded S signal (step ST610).
- step ST609: NO When the value of the second smoothing process control information CI2 is not 0 (step ST609: NO), that is, when the value of the second smoothing process control information CI2 is 1, the smoothing process unit 502 Then, a smoothed decoded S signal is calculated by multiplying the decoded S signal by a coefficient ⁇ 2 i that gradually amplifies in time more slowly than in step ST610 (step ST611).
- step ST608 if the value of the first smoothing process control coefficient CI1 is not 2 (step ST608: NO), that is, if the value of the first smoothing process control coefficient CI1 is 0, smoothing is performed.
- the processing unit 502 uses the decoded S signal as a decoded S signal that is smoothed without any multiplication.
- the L / R signal calculation unit 305 calculates a decoded L signal and a decoded R signal from the calculated decoded M signal and the smoothed decoded S signal, and outputs the calculated decoded L signal and decoded R signal. (Step ST612).
- the present embodiment in addition to the effects of the first embodiment described above, in a scheme for encoding / decoding a multi-channel signal such as an M / S encoding / decoding scheme, It is possible to suppress deterioration in sound quality when a transmission error occurs due to loss. That is, according to the present embodiment, when performing smoothing processing (smoothing processing) of the number of channels between frames at the signal level instead of the parameter level, the energy between the L channel and the R channel is expressed as the correlation. The speed of the smoothing process is adjusted using the ratio. Thereby, sound quality degradation can be suppressed.
- smoothing processing smoothing processing
- the speed of the smoothing process which is an attenuation process or an amplification process, is reduced (the amount of time change is reduced).
- the speed of the smoothing process which is an attenuation process or an amplification process.
- decoding apparatus 500 has been described using the flow of FIG. 6, but is not necessarily limited to this flow.
- the order of ST604 to ST607 and ST608 to ST611 may be reversed.
- the case where the L / R correlation calculation unit 501 calculates the correlation of the L / R channel from the decoded M signal and the decoded S signal has been described as an example.
- the present invention is not limited to this.
- the present invention can be similarly applied to the case where the correlation between M / S channels is used.
- the present embodiment whether or not the energy ratio between the L channel and the R channel is greater than or equal to a predetermined first threshold value or less than or equal to a second threshold value when determining the value of the second smoothing process control information.
- the configuration in which the second smoothing process control information is determined as a binary value of 0 or 1 according to the determination result using the determination criterion has been described.
- the present embodiment is not limited to this, and can be similarly applied to a configuration in which the second smoothing processing control information is weighted instead of binary. That is, the larger the energy difference between the L channel and the R channel, the closer the value of the second smoothing process control information is to 1, and the smaller the energy difference between the L channel and the R channel, the second smoothing process.
- a configuration in which the value of the control information is close to 0 is given as an example. Further, in the smoothing processing unit, the closer the value of the second smoothing processing control information is to 1, the more smoothly the smoothing processing can be performed by slowly attenuating or amplifying the decoded S signal. Therefore, it is possible to further suppress deterioration in sound quality.
- FIG. 7 is a block diagram showing a configuration of decoding apparatus 700 according to Embodiment 3 of the present invention.
- Decoding apparatus 700 shown in FIG. 7 adds L / R correlation calculation section 703 to decoding apparatus 103 according to Embodiment 1 shown in FIG. 3, and S signal decoding section 701 instead of S signal decoding section 303. And an L / R signal calculation unit 702 instead of the L / R signal calculation unit 305.
- the communication system of the present embodiment has the same configuration as that of FIG. 1 except that it has a decoding device 700 instead of the decoding device 103, and therefore the description thereof is omitted.
- the decoding apparatus 700 includes a separation unit 301, an M signal decoding unit 302, an S signal decoding unit 701, a smoothing processing unit 304, an L / R signal calculation unit 702, and an L / R correlation calculation unit 703. Configured. Hereinafter, each configuration will be described in detail.
- Separating section 301 separates encoded information input from encoding apparatus 101 via transmission path 102 into M encoded information and S encoded information, and supplies the separated M encoded information to M signal decoding section 302.
- the separated S encoded information is output to the S signal decoding unit 701.
- Separation section 301 detects the presence or absence of transmission errors in the input encoded information.
- the separation unit 301 detects a temporal change in information included in the input encoded information, and the smoothing processing unit 304 uses the detected temporal change as the smoothing process control information CI. Output to.
- the M signal decoding unit 302 receives the M encoded information from the separating unit 301, decodes the input M encoded information by a CELP speech decoding method, and calculates a decoded M signal.
- the speech decoding method in the M signal decoding unit 302 is a method corresponding to the encoding method in the M signal encoding unit 202 in the encoding apparatus 101.
- the M signal decoding unit 302 outputs the calculated decoded M signal to the S signal decoding unit 701 and the L / R signal calculation unit 702.
- the S signal decoding unit 701 receives the S encoded information from the separation unit 301, decodes the input S encoded information by a CELP speech decoding method, and calculates a decoded S signal.
- the speech decoding method in the S signal decoding unit 701 is a method corresponding to the encoding method in the S signal encoding unit 203 in the encoding device 101. Further, the S signal decoding unit 701 outputs the calculated decoded S signal to the smoothing processing unit 304.
- the S signal decoding unit 701 calculates a decoded S signal by the following method. That is, the S signal decoding unit 701 receives the auxiliary information AI of the decoded S signal of the frame one frame before the current frame (hereinafter referred to as “previous frame”) input from the L / R correlation calculation unit 703 and the M signal. Using the decoded M signal input from the decoding unit 302 and the decoded L signal and decoded R signal of the previous frame input from the L / R signal calculation unit 702, a decoded S signal is calculated using equation (10). In the equation (10), L ′ ⁇ 1 and R ′ ⁇ 1 are signals calculated from the decoded L signal of the previous frame or the decoded R signal of the previous frame. The auxiliary information AI of the decoded S signal will be described later.
- L ′ ⁇ 1 and R ′ ⁇ 1 are calculated when the M signal decoding unit 302 calculates a decoded M signal for the decoded L signal (L ⁇ 1 ) and the decoded R signal (R ⁇ 1 ) of the previous frame. Calculation is performed using the pitch period obtained from the M encoded information and the decoded L signal and decoded R signal of the previous frame.
- the S signal decoding unit 701 cuts out a waveform of one period of the pitch period of the decoded L signal or the decoded R signal of the previous frame, and makes a number on the time axis so that the waveform of the decoded M signal matches the peak and valley.
- L ′ ⁇ 1 and R ′ ⁇ 1 are calculated by sliding the sample. That is, the S signal decoding unit 701 slides the decoded L signal or the decoded R signal of the previous frame on the time axis so that the phases of the decoded L signal or the decoded R signal of the previous frame and the M signal of the current frame are matched.
- FIG. 8 is a diagram showing processing for matching the peaks and valleys of the waveform in the S signal decoding unit 701.
- FIG. 8A shows the waveform of the decoded M signal of the current frame
- FIG. 8B shows the decoded L signal (L ′ ⁇ 1 ) of the previous frame
- FIG. ) Shows the decoded L signal (L ′ ⁇ 1 ) of the previous frame in which the pitch period is combined with the decoded M signal.
- the energy of the decoded L signal of the previous frame is larger than the energy of the decoded R signal of the previous frame will be described as an example.
- the smoothing processing unit 304 receives the decoded S signal from the S signal decoding unit 701 and the smoothing processing control information CI from the separation unit 301.
- the smoothing processing unit 304 performs a time-dependent attenuation or amplification process on the decoded S signal according to the value of the smoothing process control information CI, and calculates a smoothed decoded S signal.
- the smoothing processing unit 304 is a coefficient that gradually attenuates with respect to the decoded S signal according to the equation (3). To calculate a smoothed decoded S signal.
- the smoothing processing unit 304 multiplies the decoded S signal by a coefficient that gradually amplifies in accordance with the equation (4), A smoothed decoded S signal is calculated. Further, when the value of the smoothing process control coefficient CI is 0, the smoothing processing unit 304 uses the decoded S signal as it is as a smoothed decoded S signal without multiplying anything. Further, the smoothing processing unit 304 outputs the calculated smoothed decoded S signal to the L / R signal calculating unit 702.
- the L / R signal calculation unit 702 receives the decoded M signal from the M signal decoding unit 302 and the decoded S signal smoothed from the smoothing processing unit 304. In addition, the L / R signal calculation unit 702 calculates two-channel signals of the decoded L signal and the decoded R signal according to the equations (5) and (6) corresponding to the M / S signal calculation unit 201. Then, the L / R signal calculation unit 702 outputs the calculated decoded L signal and decoded R signal as 2-channel output signals. Also, the L / R signal calculation unit 702 outputs the calculated decoded L signal and decoded R signal to the S signal decoding unit 701 and the L / R correlation calculation unit 703.
- the L / R correlation calculation unit 703 receives the decoded L signal and the decoded R signal from the L / R signal calculation unit 702. Further, the L / R correlation calculation unit 703 calculates an energy ratio as a correlation between the L channel and the R channel from the input decoded L signal and decoded R signal, and auxiliary information of the decoded S signal according to the energy ratio. Determine the AI.
- the auxiliary information AI of the decoded S signal is calculated by the equation (11). Specifically, the L / R correlation calculation unit 703 compares the L signal and the R signal, and sets the value of the auxiliary information AI of the decoded S signal to 0 when the energy of the L signal is greater than the energy of the R signal. When the energy of the R signal is equal to or higher than the energy of the L signal, the value of the auxiliary information AI of the decoded S signal is set to 1.
- the L / R correlation calculation unit 703 outputs the obtained auxiliary information of the decoded S signal to the S signal decoding unit 701. Above, description of the structure of the decoding apparatus 700 is completed.
- FIG. 9 is a flowchart showing the operation of the decoding device 700.
- parts that are the same as those in FIG. 4 are given the same reference numerals, and descriptions thereof are omitted.
- Separating section 301 detects whether or not S encoded information is included in the encoded information, and sets the value (0, 1, 2) of smoothing process control information CI according to the detection result (step S1). ST401).
- the M signal decoding unit 302 calculates a decoded M signal
- the S signal decoding unit 701 calculates a decoded S signal.
- the S signal decoding unit 701 inputs the auxiliary information AI of the decoded S signal of the previous frame input from the L / R correlation calculation unit 703.
- the decoded S signal is calculated using the decoded M signal input from M signal decoding section 302 and the decoded L signal and decoded R signal of the previous frame input from L / R signal calculation section 702 (step ST901).
- the smoothing processing unit 304 determines whether or not the value of the smoothing processing control information CI is 1 (step ST403).
- the present embodiment in addition to the effects of the first embodiment described above, in a scheme for encoding / decoding a multi-channel signal such as an M / S encoding / decoding scheme, It is possible to suppress deterioration in sound quality when a transmission error occurs due to loss. That is, according to the present embodiment, when performing smoothing processing (smoothing processing) of the number of channels between frames at the signal level instead of the parameter level, the decoded L signal and decoded R signal decoded in the previous frame. The decoded S signal of the lost frame is calculated using the energy ratio. Thereby, sound quality degradation can be suppressed.
- smoothing processing smoothing processing
- the M signal that has been normally received and decoded and the channel on which the signal is concentrated A highly accurate decoded S signal can be calculated from the decoded signal (decoded signal of the previous frame).
- the above-described method is particularly effective for a situation where a channel in which signals are concentrated between frames does not switch so frequently.
- the two channel signals are described as the L signal and the R signal.
- the present invention is not limited to this, and the L signal and the R signal are reversed in the above description. Even in this case, the same effect can be obtained.
- the decoding method in the decoding apparatuses 103, 500, and 700 has been described as a method corresponding to the encoding method in the encoding apparatus 101.
- the decoding apparatus may be configured to decode the encoded information generated by the encoding apparatus that can generate the decodable encoded information.
- the energy ratio is used as the correlation between the L channel and the R channel.
- the present invention is not limited to this, and other indicators may be used.
- the signal processing program is recorded or written on a machine-readable recording medium such as a memory, a disk, a tape, a CD, or a DVD, and the operation is performed.
- a machine-readable recording medium such as a memory, a disk, a tape, a CD, or a DVD.
- each functional block is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.
- the LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.
- the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor.
- An FPGA Field Programmable Gate Array
- a reconfigurable / processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.
- the decoding apparatus and decoding method according to the present invention can suppress deterioration in sound quality even when a transmission error occurs due to frame loss, and can be applied to, for example, a packet communication system or a mobile communication system.
Abstract
Description
図1は、本発明の実施の形態1に係る通信システム100の構成を示すブロック図である。通信システム100は、符号化装置101と、伝送路102と、復号装置103とから主に構成される。通信システム100において、符号化装置101と復号装置103とは、伝送路102を介して互いに通信可能である。なお、符号化装置101及び復号装置103は、いずれも、通常、基地局装置あるいは通信端末装置等に搭載されて用いられる。以下に、各構成について、詳細に説明する。
図5は、本発明の実施の形態2に係る復号装置500の構成を示すブロック図である。
図7は、本発明の実施の形態3に係る復号装置700の構成を示すブロック図である。
Claims (11)
- ステレオ信号を構成する第1チャネル信号と第2チャネル信号とから算出したモノラル信号を符号化した符号化モノラル信号と、前記第1チャネル信号と前記第2チャネル信号との差分信号を符号化した符号化差分信号とを受信する受信手段と、
受信した前記符号化差分信号における時間的変化を検出する検出手段と、
受信した前記符号化モノラル信号を復号して復号モノラル信号を取得し、受信した前記符号化差分信号を復号して復号差分信号を取得する復号手段と、
前記復号差分信号と検出した前記時間的変化に対応する係数との演算により前記復号差分信号の平滑化処理を行う平滑化手段と、
前記復号モノラル信号と前記平滑化処理した前記復号差分信号とから復号ステレオ信号を算出する算出手段と、
を具備する復号装置。 - 前記復号モノラル信号及び前記復号差分信号から前記第1チャネル信号と前記第2チャネル信号との相関を算出する相関算出手段をさらに具備し、
前記平滑化手段は、前記相関に応じて異なる前記係数を前記復号差分信号に乗算する請求項1記載の復号装置。 - 前記相関算出手段は、前記相関として前記第1チャネル信号と前記第2チャネル信号とのエネルギー比を算出し、
前記平滑化手段は、前記エネルギー比に応じて異なる前記係数を前記復号差分信号に乗算する請求項2記載の復号装置。 - 前記平滑化手段は、前記エネルギー比が第1の閾値以上または前記第1の閾値より小さい第2の閾値以下の場合に、前記エネルギー比が前記第1の閾値より小さくかつ前記第2の閾値よりも大きい場合に比べて、前記復号差分信号の増幅量または減衰量が小さくなる前記係数を前記復号差分信号に乗算する請求項3記載の復号装置。
- 前記検出手段は、前記符号化差分信号が含まれているフレームから含まれていないフレームに変化したこと、または前記符号化差分信号が含まれていないフレームから含まれているフレームに変化したことを前記時間的変化として検出する請求項1記載の復号装置。
- 前記復号ステレオ信号を構成する、前記第1チャネル信号の復号結果である復号第1チャネル信号と前記第2チャネル信号の復号結果である復号第2チャネル信号との相関を算出する相関算出手段をさらに具備し、
前記復号手段は、前記符号化差分信号が現フレームに含まれていない場合に、算出した前記相関に基づいて、前記現フレームの前記復号モノラル信号と、前記現フレームの前のフレームの前記復号第1チャネル信号または前記復号第2チャネル信号とから、前記現フレームの前記復号差分信号を取得する請求項5記載の復号装置。 - 前記相関算出手段は、前記相関として前記復号第1チャネル信号と前記復号第2チャネル信号とのエネルギー比を算出し、
前記復号手段は、前記エネルギー比に基づいて、前記現フレームの前記復号差分信号を取得する請求項6記載の復号装置。 - 前記復号手段は、前記相関算出手段により算出したエネルギーの大きい前記前のフレームの前記復号第1チャネル信号と前記復号第2チャネル信号とのいずれか一方と、前記現フレームの前記復号モノラル信号とから前記現フレームの前記復号差分信号を取得する請求項7記載の復号装置。
- 請求項1記載の復号装置を具備する通信端末装置。
- 請求項1記載の復号装置を具備する基地局装置。
- ステレオ信号を構成する第1チャネル信号と第2チャネル信号とから算出したモノラル信号を符号化した符号化モノラル信号と、前記第1チャネル信号と前記第2チャネル信号との差分信号を符号化した符号化差分信号とを受信するステップと、
受信した前記符号化差分信号における時間的変化を検出するステップと、
受信した前記符号化モノラル信号を復号して復号モノラル信号を取得し、受信した前記符号化差分信号を復号して復号差分信号を取得するステップと、
前記復号差分信号と検出した前記時間的変化に対応する係数との演算により前記復号差分信号の平滑化処理を行うステップと、
前記復号モノラル信号と前記平滑化処理した前記復号差分信号とから復号ステレオ信号を算出するステップと、
を具備する復号方法。
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