JP2005024756A - Decoding process circuit and mobile terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decoding process circuit in which deterioration in output sound quality is suppressed even though an error is generated in audio data and to provide a mobile terminal device. <P>SOLUTION: An AAC decoder 61 restores low and middle range frequency band PCM data LM from AAC data and outputs the restored PCM data LM and remaining SBR data to an SBR decoder 62. In accordance with the instruction of a control section 60, the SBR decoder 62 conducts a correcting process of the PCM data LM, up-sampling of the PCM data LM and a high frequency extending process based on the SBR data to obtain high frequency band PCM data H. The control section 60 conducts to determine whether an error is generated in the AAC data and the SBR data, and the control section 60 controls the SBR decoder 62 based on the decision result and the correction process of the PCM data LM, up-sampling of the PCM data LM and a high frequency expanding process based on the SBR data are performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a decoding processing circuit that compensates for a code error and performs decoding in a digital information receiving apparatus used in, for example, a digital broadcasting system or a digital mobile communication system.
[0002]
[Prior art]
As is well known, a digital broadcasting system or a digital mobile communication system includes a core unit having audio information in low and middle frequency bands and a high frequency extension unit having audio information in high frequency bands. Some audio / audio signals can be used to transmit audio / audio information from low to high frequencies.
[0003]
An example of the audio / audio signal having such a data format is shown in FIG. This figure shows the syntax within one frame in an AAC (Advanced Audio Coding) + SBR (Spectral Band Replication) stream format. AAC data corresponds to the above-described core part, and SBR data corresponds to the high frequency band extension part.
[0004]
When an error occurs in the audio data, the quality of the output sound is degraded. However, when the error occurs in the audio data of the data format as described above, sufficient examination has not been made and appropriate error compensation is performed. The establishment of technology is anxious.
[0005]
For example, Patent Document 1 discloses a technique showing an error compensation circuit that keeps the quality of received data high by increasing the correlation between an error-compensated frame and frames before and after the AAC data frame. ing.
[0006]
[Patent Document 1]
JP 2001-339368 A.
[0007]
[Problems to be solved by the invention]
Conventionally, when an error occurs in audio data including a core unit having audio information in low and middle frequency bands and a high frequency extension unit having audio information in a high frequency band, sufficient There has been no study, and there has been a strong demand for the establishment of a technique for appropriate error compensation.
[0008]
The present invention has been made in response to the above-described demand, and includes audio data including a core unit having audio information in low and middle frequency bands and a high frequency extension unit having audio information in high frequency bands. It is an object of the present invention to provide a decoding processing circuit and a mobile terminal apparatus that can suppress the quality deterioration of output sound when an error occurs.
[0009]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a decoding processing circuit for decoding audio data having first audio data in a first frequency band and second audio data in a second frequency band. First decoding means for decoding the data and outputting the decoded data as first decoded data; sampling means for sampling the first decoded data into the second frequency band; and second for decoding the second audio data Of the sampling means, the second voice data judging means for judging whether or not an error has occurred in the second voice data, and the sampling means when the second voice data judging means judges that an error has occurred. The sampling result is output as the second decoded data. On the other hand, when the second audio data determination means determines that no error has occurred, the sampling result of the sampling means and the second Decoding control means for generating and outputting second decoded data based on the decoding result of the decoding means; first decoded data output by the first decoding means; second decoded data output by the decoding control means; On the basis of the above, decoded data generating means for generating decoded data having audio information in the first frequency band and audio information in the second frequency band is provided.
[0010]
According to the present invention, in the mobile terminal device that receives and reproduces audio data having the first audio data in the first frequency band and the second audio data in the second frequency band, the first audio data is decoded, A first decoding means for outputting the decoded data as first decoded data; a sampling means for sampling the first decoded data into a second frequency band; a second decoding means for decoding the second audio data; Second audio data determination means for determining whether or not an error has occurred in the second audio data, and when the second audio data determination means determines that an error has occurred, the sampling result of the sampling means is set to the second On the other hand, when the second audio data determination means determines that no error has occurred, the sampling result of the sampling means and the recovery of the second decoding means are output. Based on the decoding control means for generating and outputting the second decoded data based on the result, the first decoded data output by the first decoding means, and the second decoded data output by the decoding control means, Decoded data generating means for generating decoded data having audio information in the first frequency band and audio information in the second frequency band is provided.
[0011]
In the decoding processing circuit and mobile terminal apparatus configured as described above, when there is an error in the second audio data, the second decoding is performed by sampling the first decoded data obtained by decoding the first audio data into the second frequency band. On the other hand, if there is no error in the second audio data, the second decoded data is based on the sampled first decoded data in the second frequency band and the decoded second audio data. Is generated. Then, based on the first decoded data and the second decoded data, decoded data having audio information in the first frequency band and audio information in the second frequency band is generated.
[0012]
Therefore, according to the decoding processing circuit and the mobile terminal apparatus configured as described above, when decoding audio data having the first audio data in the first frequency band and the second audio data in the second frequency band, Since the second decoded data is generated by selectively using the first decoded data and the second decoded data depending on whether or not there is an error in the audio data, the error occurs in the audio data However, quality degradation of the output sound can be suppressed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of a mobile terminal apparatus including a decoding processing circuit according to an embodiment of the present invention. This mobile terminal device receives a broadcast signal transmitted from a broadcast station of a digital broadcast system or a digital mobile communication system (not shown) and reproduces video and audio.
[0014]
This mobile terminal apparatus includes an antenna 1, an RF unit 2, a data separation unit 3, a video data processing unit 4, a display unit 5, an audio / audio data processing unit 6, and a speaker 7. Here, as an example of an audio / audio signal, a case of handling audio / audio data in an AAC (Advanced Audio Coding) + SBR (Spectral Band Replication) stream format as shown in FIG. 2 will be described as an example.
[0015]
The antenna 1 receives the broadcast signal transmitted from the broadcast station from the space and outputs it to the RF unit 2. The RF unit 2 converts the broadcast signal into a baseband signal, performs demodulation processing, and extracts received data. The received data is divided into video data and audio / audio data by the data separation unit 3, and the video data is output to the video data processing unit 4, while the audio / audio data is output to the audio / audio data processing unit 6. Is output.
[0016]
The video data processing unit 4 decodes the video data, decompresses the compressed data, and converts it into a video signal. This video signal is output to the display unit 5 and displayed to the user.
[0017]
On the other hand, the audio / audio data processing unit 6 has an error compensation function, decodes the audio / audio data, converts it into an analog audio signal, and outputs the sound from the speaker 7. The control unit 60, the AAC decoder 61, An SBR decoder 62 and a PCM sound source 63 are provided.
[0018]
The AAC decoder 61 performs a decoding process based on the AAC decoding information in the audio / audio data as shown in FIG. 2 in accordance with an instruction from the control unit 60, so that the low-frequency to middle-frequency shown in FIG. The PCM data LM in the band f1 is restored, and the restored PCM data LM and the remaining SBR decode information (FILL Element) are output to the SBR decoder 62.
[0019]
The AAC decoding information includes a header (Header), CRC data (CRC1), and AAC data. CRC data (CRC1) protects part of the AAC data. The SBR decode information includes identification information (ID), CRC data (CRC2), and SBR data. CRC data (CRC2) protects all of the SBR data. For more details, see ISO / IEC 14496-3 and ISO / IEC JTC1 / SC29 / WG11 MPEG2002 / M7943.
[0020]
The SBR decoder 62 performs the correction process of the PCM data LM, the upsampling of the PCM data LM, and the high frequency band extension process based on the SBR decode information in accordance with the instruction of the control unit 60, and the high frequency band as shown in FIG. PCM data H in band f2 is obtained. Then, the PCM data LM and the PCM data H are synthesized and output to the PCM sound source 63. A detailed configuration will be described later.
[0021]
The PCM sound source 63 reproduces an analog audio signal based on the PCM data output from the SBR decoder 62. The analog audio signal is amplified by an amplifier (not shown) and then output from the speaker 7 as a loud voice.
[0022]
The control unit 60 controls each part of the voice / audio data processing unit 6 and determines whether or not there is an error in the AAC data based on the CRC data (CRC1), CRC data (CRC2 ) To determine whether or not an error has occurred in the SBR data, and based on the determination result, operation control of the AAC decoder 61 and the SBR decoder 62 is performed.
[0023]
FIG. 4 shows the configuration of the SBR decoder 62. The SBR decoder 62 includes a QMF (Quadrature Mirror Filter) analysis unit 621, a changeover switch 622, an HF (High Frequency) generation unit 623, an envelope correction unit 624, and a QMF synthesis unit 625.
[0024]
The QMF analysis unit 621 is a band division filter bank, and upsamples the data signal output from the AAC decoder 61 by the operation of the QMF synthesis unit 625 described later. Note that “0” data is set in the PCM data H in the high frequency band output from the QMF analysis unit 621.
[0025]
The changeover switch 622 is selectively controlled by the control unit 60 and selectively outputs the data signal output from the QMF analysis unit 621 to the HF generation unit 623 or the QMF synthesis unit 625.
[0026]
The HF generation unit 623 receives the PCM data LM, the PCM data H, and the SBR decode information through the changeover switch 622, and performs a high frequency band expansion process based on the SBR data in the SBR decode information. Then, the HF generation unit 623 replaces the “0” data in the PCM data H with the high frequency information obtained by the high frequency expansion process, and outputs it to the envelope correction unit 624 together with the PCM data LM.
[0027]
The envelope correction unit 624 performs envelope correction on the PCM data LM and PCM data H output from the HF generation unit 623, and outputs the corrected PCM data LM and PCM data H to the QMF synthesis unit 625.
[0028]
The QMF synthesizing unit 625 is a band division filter bank, and upsamples the data signal output from the AAC decoder 61 by the operation of the QMF analyzing unit 621 described above. The QMF synthesizing unit 625 includes a changeover switch 622 or an envelope correcting unit. PCM data LM and PCM data H output from 624 are combined, and PCM data from a low range to a high range is combined.
[0029]
Next, the operation of the mobile terminal apparatus having the above configuration will be described. Here, description of the reproduction processing of video data will be omitted, the reproduction processing of audio / audio data will be described, and in particular, the control operation relating to error compensation of audio / audio data will be mainly described.
[0030]
FIG. 5 is a flowchart for explaining the control operation of the control unit 60, and will be described below according to this flowchart. Note that the control unit 60 performs the processing shown in this figure in units of frames as shown in FIG.
[0031]
First, in step 5 a, the control unit 60 inspects the audio / audio data given from the data separation unit 3. Here, the control unit 60 determines whether or not an error has occurred for AAC data based on CRC data (CRC1), while an error has occurred for SBR data based on CRC data (CRC2). It is determined whether or not. When the determination is completed, the process proceeds to step 5b.
[0032]
If the controller 60 determines in step 5b that an error has occurred in the AAC data in step 5a, the process proceeds to step 5c. On the other hand, if it is determined that no error has occurred, the controller 60 proceeds to step 5d. Transition.
[0033]
In step 5c, the control unit 60 performs correction processing on the AAC data in which an error has occurred, and proceeds to step 5d. In this correction process, for example, correct AAC data in frames before and after the current frame is used to generate AAC data highly correlated with these AAC data.
[0034]
Details of this correction processing are described in detail in Japanese Patent Application Laid-Open No. 2001-339368 inventor of the present application. The AAC data generated by this correction processing is output to the AAC decoder 61. On the other hand, the AAC decoder 61 uses the AAC data provided from the control unit 60 in place of the AAC data provided from the data separation unit 3.
[0035]
If the controller 60 determines in step 5d that an error has occurred in the SBR data in step 5a, the control unit 60 proceeds to step 5e, whereas if it determines that no error has occurred, the controller 60 proceeds to step 5f. Transition.
[0036]
In step 5 e, the control unit 60 controls the changeover switch 622 so that the output of the QMF analysis unit 621 is input to the QMF synthesis unit 625. As a result, the SBR decoder 62 generates PCM data that has only been subjected to upsampling based on the PCM data LM, and outputs it to the PCM sound source 63.
[0037]
In step 5 f, the control unit 60 controls the changeover switch 622 so that the output of the QMF analysis unit 621 is input to the HF generation unit 623. As a result, the SBR decoder 62 generates PCM data that has been subjected to upsampling based on the PCM data LM and high-frequency extension processing based on the SBR data in the SBR decode information, and is output to the PCM sound source 63.
[0038]
As described above, the mobile terminal apparatus having the above configuration corrects the AAC data when there is an error in the AAC data. If there is an error in the SBR data, the PCM data LM in the low frequency band generated based on the AAC data is upsampled to generate the PCM data H in the high frequency band, while the SBR If there is no error in the data, the PCM data LM is upsampled, and a high frequency band expansion process based on the SBR data is performed to generate PCM data H in a high frequency band.
[0039]
Therefore, according to the mobile terminal apparatus configured as described above, when an error occurs in AAC data or SBR data, the PCM data H in the high frequency band is generated according to the error occurrence pattern. Even when an error occurs in the audio data, it is possible to suppress the quality deterioration of the output sound.
[0040]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. Further, for example, a configuration in which some components are deleted from all the components shown in the embodiment is also conceivable. Furthermore, you may combine suitably the component described in different embodiment.
[0041]
As an example, for example, as shown in FIG. 6, a level adjustment unit 64 is provided between the SBR decoder 62 and the PCM sound source 63, and an error occurs in the SBR data under the control of the control unit 60. Control may be performed to increase the volume level of the PCM data output from 62.
[0042]
According to such control, when an error has occurred in the SBR data, only upsampling is performed. However, since the high frequency expansion process is not performed only by upsampling, the output sound level is attenuated. Can be prevented. It has been confirmed by the present inventors that such level attenuation of the output sound becomes significant when a data error corresponding to 100 milliseconds or more occurs in terms of hearing.
[0043]
Hereinafter, a specific level adjustment process of the level adjustment unit 64 will be described.
If no error has occurred in the SBR data, the PCM data output from the SBR decoder 62 by the high frequency expansion processing of the HF generation unit 623 does not cause a relative drop in the volume level. Under the control of the control unit 60, the volume level of the PCM data is measured and stored, and the PCM data is output to the PCM sound source 63 without adjusting the volume level.
[0044]
On the other hand, when there is an error in the SBR data, only upsampling is performed by the QMF analysis unit 621 and the QMF synthesis unit 625, so that the relative volume level drops in the PCM data output from the SBR decoder 62. Occurs. For this reason, the level adjustment unit 64 predicts an appropriate volume level from the transition of the volume level of the saved past frame under the control of the control unit 60, and the volume of the current frame so as to become this volume level. Level adjustment is performed, and the PCM data is output to the PCM sound source 63. Therefore, when the level of the current frame is smaller than the value predicted from the past level transition, the current frame level is amplified to the predicted value to obtain the final output PCM. On the other hand, when the level of the current frame is larger than the value predicted from the past level transition, the signal of the current frame is determined to be a signal having a high level from the beginning, and is finally output without any level adjustment. It will be.
[0045]
In the above embodiment, the data is corrected when there is an error in the AAC data. In addition to this, when there is an error in the SBR data, the data is corrected. High frequency expansion processing may be performed. An example of the configuration of the SBR decoder 62 that performs such processing is shown in FIG.
[0046]
In this configuration, when there is no error in the SBR data, the control unit 60 controls the changeover switch 622 so that the output of the QMF analysis unit 621 is output to the HF generation unit 623 as well as the configuration of FIG. Is output to the SBR data correction unit 626 provided in FIG. Then, the SBR data correction unit 626 stores correct SBR data.
[0047]
On the other hand, when there is an error in the SBR data, the control unit 60 controls the changeover switch 622 to output the output of the QMF analysis unit 621 to the SBR data correction unit 626. Then, the SBR data correction unit 626 performs correction processing of the SBR data, and outputs the corrected SBR data and the PCM data LM output from the QMF analysis unit 621 to the HF generation unit 623.
The SBR data correction processing in the SBR data correction unit 626 is to generate SBR data having a high correlation with these SBR data using correct SBR data in the frames before and after the stored current frame. To do.
[0048]
Furthermore, in the above-described embodiment, the case of a decoding method that generates PCM data H in a high frequency band from PCM data LM in a low and middle frequency band has been described as an example. It is also possible to apply the present invention to a decoding scheme that generates PCM data LM in a low-middle frequency band from PCM data H in a high-frequency band by band expansion processing.
In addition, it goes without saying that the present invention can be similarly implemented even if various modifications are made without departing from the gist of the present invention.
[0049]
【The invention's effect】
As described above, in the present invention, when there is an error in the second audio data, the second decoded data is obtained by sampling the first decoded data obtained by decoding the first audio data into the second frequency band. On the other hand, if there is no error in the second audio data, the second decoded data is generated based on the sampled first decoded data in the second frequency band and the decoded second audio data. To do. Then, based on the first decoded data and the second decoded data, decoded data having audio information in the first frequency band and audio information in the second frequency band is generated.
[0050]
Therefore, according to the present invention, when decoding the audio data having the first audio data in the first frequency band and the second audio data in the second frequency band, is there an error in the second audio data? Depending on whether or not the second decoded data is generated by selectively using the first decoded data and the second decoded data, even if an error occurs in the audio data, the deterioration of the quality of the output sound is suppressed. It is possible to provide a decoding processing circuit and a mobile terminal device that can be used.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a configuration of an embodiment of a mobile terminal apparatus according to the present invention.
FIG. 2 is a diagram showing an example of a frame format of audio / audio data handled by the mobile terminal apparatus shown in FIG. 1;
FIG. 3 is a diagram showing a frequency distribution of audio data restored based on AAC decode information and SBR decode information.
4 is a circuit block diagram showing a configuration of an SBR decoder of the mobile terminal apparatus shown in FIG. 1. FIG.
FIG. 5 is a flowchart for explaining the operation of the voice / audio data processing unit of the mobile terminal apparatus shown in FIG. 1;
6 is a circuit block diagram showing a configuration of a modified example of the mobile terminal apparatus shown in FIG. 1;
7 is a circuit block diagram showing a configuration of a modified example of the SBR decoder of the mobile terminal apparatus shown in FIG. 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... RF part, 3 ... Data separation part, 4 ... Video data processing part, 5 ... Display part, 6 ... Audio | voice / audio data processing part, 7 ... Speaker, 60 ... Control part, 61 ... AAC decoder, 62 ... SBR decoder, 63 ... PCM sound source, 64 ... level adjustment unit, 621 ... QMF analysis unit, 622 ... changeover switch, 623 ... HF generation unit, 624 ... envelope correction unit, 625 ... QMF synthesis unit, 626 ... SBR data correction Department.

Claims (8)

In a decoding processing circuit for decoding audio data having first audio data in a first frequency band and second audio data in a second frequency band,
First decoding means for decoding the first audio data and outputting the decoded data as first decoded data;
Sampling means for sampling the first decoded data into a second frequency band;
Second decoding means for decoding the second audio data;
Second audio data determination means for determining whether an error has occurred in the second audio data;
When the second sound data determination means determines that an error has occurred, the sampling result of the sampling means is output as second decoded data, while the second sound data determination means indicates that no error has occurred. If so, decoding control means for generating and outputting second decoded data based on the sampling result of the sampling means and the decoding result of the second decoding means;
Based on the first decoded data output from the first decoding means and the second decoded data output from the decoding control means, the audio information of the first frequency band and the audio information of the second frequency band are included. A decoding processing circuit comprising: decoded data generating means for generating decoded data. A first audio data determination means for determining whether an error has occurred in the first audio data;
Voice data generating means for generating first voice data when the first voice data determining means determines that an error has occurred;
The first decoding unit decodes the first audio data generated by the audio data generation unit when the first audio data determination unit determines that an error has occurred, The decoding processing circuit according to claim 1, wherein the decoding processing circuit outputs the decoded data. The voice data generation means includes
Storage means for storing a plurality of samples of the first decoded data output by the first decoding means;
When the first audio data determination unit determines that an error has occurred, the first decoded data is based on the past first decoded data stored in the storage unit and the subsequent first decoded data. The decoding processing circuit according to claim 2, further comprising: generating means for generating Furthermore, when the second sound data determination means determines that an error has occurred, the sound data generation means for generating second sound data,
The said 2nd decoding means decodes the 2nd audio | voice data which the said audio | voice data generation means produced | generated, when the said 2nd audio | voice data determination means determines with the error having arisen. The decoding processing circuit according to 1. The voice data generation means includes
Storage means for storing a plurality of samples of the second decoded data output from the second decoding means;
When the second audio data determination unit determines that an error has occurred, the second decoded data is based on the past second decoded data stored in the storage unit and the subsequent second decoded data. The decoding processing circuit according to claim 4, further comprising: generating means for generating Furthermore, when the said 2nd audio | voice data determination means determines with the error having arisen, the sound volume level control means which controls the sound volume level of the decoding data which the said decoding data generation means produced | generated is provided. The decoding processing circuit according to 1. The volume level control means includes
Volume level detecting means for detecting the volume level of the decoded data generated by the decoded data generating means;
Storage means for storing a plurality of samples of volume levels detected by the volume level detection means;
When the second sound data determining means determines that an error has occurred, the sound volume level is predicted based on the sound volume level data stored in the storage means, and the decoding is performed based on the predicted sound volume level. 7. The decoding processing circuit according to claim 6, further comprising level control means for controlling a volume level of the decoded data generated by the data generating means. In a mobile terminal device that receives and reproduces audio data having first audio data in a first frequency band and second audio data in a second frequency band,
First decoding means for decoding the first audio data and outputting the decoded data as first decoded data;
Sampling means for sampling the first decoded data into a second frequency band;
Second decoding means for decoding the second audio data;
Second audio data determination means for determining whether an error has occurred in the second audio data;
When the second sound data determination means determines that an error has occurred, the sampling result of the sampling means is output as second decoded data, while the second sound data determination means indicates that no error has occurred. If so, decoding control means for generating and outputting second decoded data based on the sampling result of the sampling means and the decoding result of the second decoding means;
Based on the first decoded data output from the first decoding means and the second decoded data output from the decoding control means, the audio information of the first frequency band and the audio information of the second frequency band are included. A mobile terminal apparatus comprising: decoded data generation means for generating decoded data.

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