JP6514626B2 - Digital wireless microphone transmitter, receiver and system - Google Patents

Description

  The present invention relates to a transmitter, receiver and system of a digital wireless microphone, and a method of detecting an error in a digital audio signal used in the digital wireless microphone.

  There are an analog method and a digital method as a transmission method of the wireless microphone (radio microphone). The wireless microphone of the analog type transmits the audio signal as it is by analog modulation and transmits it, and although it has a short delay time, it has the disadvantage of being susceptible to obstacles and interference, etc. Research and development of digital wireless microphones are being carried out vigorously.

  A digital wireless microphone converts analog voice signals into digital voice signals for wireless transmission. In order to prevent data errors in digital voice signals from occurring in the radio propagation path, the digital wireless microphone has an error correction code for correcting errors and whether there are any errors that could not be corrected by the error correction codes. An error detection code to be detected is generally used in combination.

  FIG. 7 shows a configuration example of a conventional digital wireless microphone system in which an error correction code and an error detection code are used in combination. FIG. 7 (a) is a block diagram of a digital wireless microphone transmitter 100, and FIG. 7 (b) is a block diagram of a digital wireless microphone receiver 200. As shown in FIG.

  The digital wireless microphone transmitter 100 includes an information source coding unit 11, an error detection coding unit 12, an error correction coding unit 13, a modulation unit 14, a power amplification unit 15, and a transmission antenna 16. ing.

  The source coding unit 11 performs source coding on the input voice signal. That is, an analog audio signal is sampled at a predetermined sampling frequency (for example, 48 kHz), analog / digital (A / D) converted, and data compression is performed as necessary to generate a digital audio signal.

  The error detection coding unit 12 performs error detection coding on the digital speech signal. As an error detection code, a cyclic redundancy check (CRC) code is widely used as a representative code (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  FIG. 8 shows an outline of the conventional error detection coding. Here, although a bit configuration in which a 4-bit error detection code is added to a 22-bit digital audio signal is described as an example, the number of bits is not limited to this. By source coding, one sample of the audio signal becomes a 22-bit digital audio signal. The entire 22-bit digital audio signal is used as error detection coding target data, and 4-bit error detection coding is performed. That is, 4 bits of error detection code calculated for all audio bits (22 bits) are added to the digital audio signal, and the digital audio signal subjected to error detection coding becomes a bit string of 26 bits.

  The error correction coding unit 13 performs error correction coding on the output signal from the error detection coding unit 12 (a digital voice signal to which an error detection code is added). There are various error correction codes, and a convolutional code is widely used as a representative one (see, for example, Non-Patent Document 1).

  The modulation unit 14 performs signal modulation on the output signal from the error correction coding unit 13 using a predetermined modulation method. As a modulation scheme, any scheme can be used. For example, quadrature phase shift keying (QPSK) or 16 quadrature amplitude modulation (QAM) using a single carrier, or orthogonal frequency division multiplexing (OFDM) using a plurality of carrier frequencies. Etc. can be used.

  The power amplification unit 15 performs power amplification on the modulated signal, and transmits the signal from the transmission antenna 16 to the wireless propagation path.

  The receiving apparatus 200 of the digital wireless microphone of FIG. 7B includes a receiving antenna 21, a receiving amplification unit 22, a demodulation unit 23, an error correction decoding unit 24, an error detection decoding unit 25, and an information source decoding unit 26. And have.

  The reception amplification unit 22 performs reception power amplification on the signal received by the reception antenna 21.

  The demodulation unit 23 demodulates by the demodulation method corresponding to the modulation method on the transmission side, and generates digital signal data from the reception signal.

  The error correction decoding unit 24 performs error correction decoding on the demodulated digital signal data by a method corresponding to the error correction code added on the receiving side. Viterbi decoding is widely used as a typical error correction decoding.

  The error detection decoding unit 25 performs error detection decoding on the data after error correction decoding, and whether errors remain in the digital audio signal and the digital audio signal (and error detection code). Output error detection information.

  FIG. 9 shows an outline of the conventional error detection decoding. Here, as the error detection decoding corresponding to the error detection coding described in FIG. 8, the same bit configuration as that in FIG. 8 is described as an example, but the number of bits is not limited to this. The received signal is demodulated and error correction decoding is performed to obtain an error detection coded 26-bit bit string (the bit string shown in FIG. 8). The error detection decoding is performed with all 26 bits as an error detection range, and it is checked whether errors remain in the 26 bits, and the 22-bit digital voice signal and error detection information (error in all 26 bits) The information on whether or not there is left is output.

  The information source decoding unit 26 performs information source decoding on the digital audio signal output from the error detection decoding unit 25. That is, information source decoding corresponding to information source coding processing on the transmission side is performed, and the original sound signal is restored from the digital sound signal.

  Here, if the propagation condition deteriorates, errors can not be corrected by error correction decoding, and errors remain in the digital speech signal, the source-decoded speech signal does not become the original speech signal, depending on the case. This produces a very loud noise that is unbearable to listen to, and makes the person who is listening to the audio signal at the receiver side uncomfortable. However, if it is possible to detect that an error remains in the digital audio signal by the error detection information, measures can be taken. For example, by taking measures to not reproduce an audio sample containing an error, a large noise is generated. You can prevent.

JP 2014-209699 A JP, 2014-112815, A Unexamined-Japanese-Patent No. 2015-23460

"Specified Radio Microphone Land Mobile Station Radio Equipment" Standard Specification (ARIB STD-T112 1.4 Edition), Japan Radio Industry Association October 2, 2014 1.4 revision

  As described above, by utilizing an error detection code for signal processing of the digital wireless microphone, it is possible to sort out an erroneous voice signal and to prevent the generation of noise. However, even when an error detection code is used, it is determined that “an error does not exist” even though an error remains, for example, when the amount of error data exceeds the detection capability of the error detection code. May occur.

  An audio signal in the case where “missing error” occurs in the digital audio signal will be described based on FIG. In order to simplify the description, FIG. 10 shows an example in which linear PCM (pulse code modulation) of 4 bits per sample is performed as source coding of the audio signal. The solid line 30 shows the original speech waveform, and the black circle (●) shows the correct digital speech signal quantized with 4 bits. The analog audio signal generated from the correct digital audio signal can almost reproduce the original audio waveform as indicated by a dashed dotted line 31.

  In the fourth speech sample, it is assumed that a bit string (A) of 1010 is allocated. If the first bit (upper 1 bit) of these 4 bits is mistaken, it becomes a bit string (B) of 0010, and the level of quantization, that is, the magnitude of the sound is restored as a speech sample having a largely different magnitude. The analog audio signal will produce a large amount of noise as indicated by the broken line 32. Large noises not only cause discomfort to people, but also may damage the acoustic device on the receiving side.

  On the other hand, if the last bit (lower 1 bit) is wrong, it becomes a bit string (C) of 1011. However, the level of quantization does not differ greatly, so in the analog voice signal It only appears as a small noise. With small noise, it is possible to safely use the digital wireless microphone because the discomfort to a person is small and the sound device on the receiving side is not damaged.

  Therefore, an object of the present invention made in view of the above problems is a transmitting device and a receiving device of a digital wireless microphone capable of detecting and dealing with a data error of a digital audio signal which becomes a large noise with high accuracy. And providing a system.

  Further, the object of the present invention, which was made in view of the above-mentioned problems, is to use a digital voice signal demodulated and decoded by a digital wireless microphone to detect a data error which is a large noise with high accuracy. An object of the present invention is to provide a method for detecting an error in an audio signal.

In the present invention, in order to improve the detection accuracy of an error causing a large noise, the object to be subjected to error detection coding is limited to a priority bit with a large degree of influence.
That is, in order to solve the above problems, a transmitter of a digital wireless microphone according to the present invention is a transmitter of a digital wireless microphone that transmits a linear PCM signal, which is an uncompressed digital audio signal, according to the OFDM method. An information source coding unit for converting a signal into a digital voice signal, an error detection coding unit for error detection coding, an error correction coding unit for error correction coding, and modulation for signal modulation by the OFDM modulation method In the transmitter of a digital wireless microphone, the error detection coding unit includes a predetermined number in the digital audio signal in the order of the largest contribution to the output level of the audio signal when an error occurs. Of the plurality of digital voice signals among voice samples transmitted in one OFDM symbol , with the upper bits of The priority bits as an integral, with respect to the priority bits an integral, have rows error detection coding, and only the number of samples for performing error detection coding of the priority bits an integral said digital audio signal is collectively transferred The error correction coding unit performs error correction coding on the entire output from the error detection coding unit that has performed error detection coding on the priority bits .

In order to solve the above problems, a digital wireless microphone receiver according to the present invention is a digital wireless microphone receiver for transmitting a linear PCM signal which is an uncompressed digital audio signal according to the OFDM method, and the received modulation A demodulation unit that demodulates a signal, an error correction decoding unit that performs error correction decoding on the demodulated signal, an error detection decoding unit that performs error detection decoding, and an information source decoding unit that converts a digital audio signal to an audio signal In the digital wireless microphone receiver, a signal subjected to error detection coding for a priority bit having a large influence degree contributing to the output level of the voice signal when an error occurs in the digital voice signal is received. The error detection and decoding unit may be configured to : transmit the plurality of digital speech signals among speech samples transmitted in one OFDM symbol; There line error detection decoding as an integrated high-order bits of the predetermined number is a priority bit, and are transferred together with the said digital audio signal by error correction decoding the number of samples for performing error detection decoding of the priority bits collectively It is characterized by

In order to solve the above problems, a digital wireless microphone system according to the present invention is a digital wireless microphone system for transmitting a linear PCM signal, which is an uncompressed digital audio signal, according to the OFDM method, and at least on the transmitting side. An error detection coding unit for performing error detection coding and an error correction coding unit for performing error correction coding, and at least an error correction decoding unit for performing error correction decoding and an error detection decoding on the receiving side. In a digital wireless microphone system provided with an error detection and decoding unit, a predetermined number of upper bits are prioritized in descending order of the degree of influence of the output level of the audio signal among errors in the digital audio signal. and then, a plurality of digital audio of the audio samples to transmitting the error detection coding unit in one OFDM symbol Integrally the priority bit of No. performs error detection coding on the priority bits an integral, and, wherein only the number of samples for performing error detection coding of the priority bit digital audio signal together with an integral are transferred, the error correction encoding unit, the priority bit performs error correction coding with respect to the total output from the error detection coding unit which performs error detection coding on the error detection decoding section 1 one of have line error detection decoding as an integrated plurality of said upper bit of said predetermined number is a priority bit of the digital audio signal among the audio samples to be transmitted in OFDM symbols, and the prioritized bit error detection which is integrated The digital audio signals subjected to error correction decoding for the number of samples to be decoded are collectively transferred .

  According to the transmitter, receiver, system, and error detection method of the digital wireless microphone in the present invention, the propagation situation is bad, and even if the error correction decoding can not correct all errors, large noise occurs. Can reduce the probability of As a result, the user can use the digital wireless microphone with peace of mind without being affected by the large noise.

FIG. 1 is a diagram showing an example of configuration of a digital wireless microphone system according to a first embodiment. It is a figure which shows the example of the bit structure in the case of error-detection encoding of a priority bit. It is a figure which shows the example of the bit structure in the case of performing error detection decoding of a priority bit. FIG. 7 is a diagram showing an example of configuration of a digital wireless microphone system according to a second embodiment. It is a figure which shows the example of a bit structure in the case of error-detection encoding of a priority bit over multiple samples. It is a figure which shows the example of a bit configuration in the case of performing error-detection encoding of a priority bit over several samples in 1 OFDM symbol. It is a figure which shows the structural example of the system of the conventional digital wireless microphone. It is a figure which shows the outline | summary of the error detection encoding currently performed conventionally. It is a figure which shows the outline | summary of the error detection decoding currently performed conventionally. FIG. 6 illustrates an example of source coding (4-bit linear PCM) and the effect of a 1-bit error.

  Hereinafter, embodiments of the present invention will be described. As is clear from the relationship between bit errors and noise in the digital audio signal shown in FIG. 10, digitized audio bits have a large degree of influence when they are erroneous. The present invention takes advantage of this nature of digital audio signals to improve the accuracy of detecting errors in audio bits that have a high degree of influence, thereby preventing the generation of large noise.

Embodiment 1
FIG. 1 shows an example of the configuration of a digital wireless microphone system according to a first embodiment of the present invention. FIG. 1 (a) is a block diagram of a transmitter 101 of the digital wireless microphone according to the first embodiment of the present invention, and FIG. 1 (b) is a block diagram of a receiver 201 of the digital wireless microphone according to the first embodiment. FIG.

  A transmitter 101 of the digital wireless microphone includes an information source coding unit 11, a priority bit error detection coding unit 17, an error correction coding unit 13, a modulation unit 14, a power amplification unit 15, and a transmission antenna 16. Is equipped. The transmitting apparatus 101 of the present invention differs from the transmitting apparatus 100 of FIG. 7A in that the conventional error detection coding unit 12 is replaced by a priority bit error detection coding unit 17. The description will be simplified for the same configuration as the prior art.

The source coding unit 11 performs source coding on the input voice signal. This source coding performs sampling of an audio signal, A / D conversion, etc., and a digital audio signal to be output is non-quantized by a predetermined number of quantization bits (for example, 22 to 24 bits). Ru linear PCM signal der of compression.

  The priority bit error detection coding unit 17 is a kind of error detection coding unit that performs error detection coding on a digital voice signal, but in particular, performs priority bit error detection coding.

  FIG. 2 shows an outline of the priority bit error detection coding. Here, under the same conditions as FIG. 8 used as an example of the prior art, 22 bits of information source encoding is performed on one sample of an audio signal, and a bit configuration in which a 4-bit error detection code is added is described as an example. However, the number of bits is not limited to this.

  In the present invention, among digital voice signals, a predetermined number of bits are regarded as priority bits in descending order of influence when errors occur (errors remain), and the priority bits are subjected to error detection coding. In general, a large degree of influence means that the degree of contribution to the output level of the analog audio signal is large. In the example of FIG. 2, for example, the upper 8 bits are selected as the priority bits having a large degree of influence, and error detection coding is performed. That is, 4-bit error detection coding is performed using only the upper 8 priority bits of the 22-bit digital audio signal encoded by the information source as the target data for error detection coding, and the other digital audio signal No error detection coding is performed on the bits (lower 14 bits). Then, 4 bits of error detection code calculated for the priority bits (upper 8 bits) are added to the digital audio signal (22 bits), and the digital audio signal subjected to error detection coding is a bit string of 26 bits. Become. In this example, the upper 8 bits are selected as the priority bits having a large degree of influence, but depending on the bit arrangement of the digital audio signal, the bits having a large degree of influence may be arranged lower or may be arranged in the central portion It is also possible.

  Although a CRC code is typically used as an error detection code, any error detection code can be used according to the purpose.

  The error correction coding unit 13 performs error correction coding on the output signal from the priority bit error detection coding unit 17 (a digital voice signal to which an error detection code is added). This error correction coding is, for example, convolutional coding with a coding rate of 2/3 or 1/2.

  As in the prior art, the modulation unit 14 performs signal modulation on the output signal from the error correction coding unit 13 according to a predetermined modulation method, and the power amplification unit 15 performs power amplification on the modulated signal. And transmit from the transmitting antenna 16 to the wireless propagation path.

  The digital wireless microphone receiver 201 shown in FIG. 1B includes a receiving antenna 21, a receiving amplifier 22, a demodulator 23, an error correction decoder 24, a priority bit error detection decoder 27, and an information source decoder. And a unit 26. The receiving device 201 of the present invention differs from the transmitting device 200 of FIG. 7B in that the conventional error detection and decoding unit 25 is replaced by a priority bit error detection and decoding unit 27. The description will be simplified for the same configuration as the prior art.

  As in the prior art, the reception amplification unit 22 performs reception power amplification on the signal received by the reception antenna 21, and the demodulation unit 23 demodulates the signal according to the modulation scheme on the transmission side. , Generate digital signal data from the received signal. Furthermore, the error correction decoding unit 24 performs error correction decoding by a method corresponding to the error correction code added on the receiving side.

  The priority bit error detection decoding unit 27 is a kind of error detection decoding unit that performs error detection decoding on data after error correction decoding, but in particular, performs priority bit error detection decoding.

  FIG. 3 shows an outline of the priority bit error detection decoding. Here, the priority bit error detection decoding corresponding to the priority bit error detection coding described in FIG. 2 will be described using the same bit configuration as FIG. 2 as an example, but the number of bits is not limited to this.

  The received signal is demodulated and error correction decoding is performed to obtain an error detection coded 26-bit bit string (the bit string shown in FIG. 2). The priority bit error detection decoding performs error detection decoding with the 12 bits including the priority bit (here, the upper 8 bits) and the error detection code (4 bits) among these 12 as an error detection range. Detect the errors involved (whether errors remain after error correction decoding). Then, a 22-bit digital audio signal and error detection information (information indicating whether an error remains in 12 bits obtained by combining the priority bit and the error detection code of the digital audio signal) is output.

  Thereafter, the information source decoding unit 26 performs information source decoding on the digital speech signal output from the priority bit error detection decoding unit 27. That is, information source decoding corresponding to information source coding processing on the transmission side is performed, and the original sound signal is restored from the digital sound signal.

  When the information that the error remains in the priority bit (and the error detection code) as the error detection information is output from the priority bit error detection / decoding unit 27, the digital voice signal is not reproduced. In this case, for example, (1) the digital audio signal is deleted, and a zero value or a predetermined value is inserted. (2) Replace the erroneous digital audio signal with the digital audio signal immediately before the error occurs. (3) Linearly interpolate the erroneous digital audio signal from the digital audio signals before and after it. It is possible to perform information source decoding by performing necessary processing (mask processing) such as.

  In general, an error detection code has a property that the lower the coding rate is, the higher the error detection capability is, and the lower the probability of occurrence of an error miss. Here, the coding rate R is a numerical value represented by R = k / n, where k is the number of information bits before coding and n is the total number of bits after coding. Although the coding rate of the example of the conventional method (FIG. 8) is 22/26 ≒ 0.85, it becomes 8/12 ≒ 0.66 in the example of the method of the present invention, and the target for error detection coding is limited. Thus, it is possible to lower the coding rate to increase the error detection capability. Also, in general, in source coding such as linear PCM, bits are often arranged in descending order of the degree of influence as shown in the example of FIG. 10, and it is possible to easily apply this method. On the other hand, when an error occurs in a non-priority bit that does not use an error detection code, unlike the conventional method, the error can not be detected, but it is not possible to detect large noise that can not be tolerated even if it is restored as it is. It does not. Rather, if an error remains in the non-priority bit, a small noise is generated, which allows the user to know that the propagation condition is bad without listening to the large noise. Therefore, performing error detection coding only on the priority bits is a practical means contributing to the improvement of the operability of the digital wireless microphone.

Second Embodiment
If it is desired to further improve the error detection accuracy, it is possible to implement preferential bit error detection coding over multiple samples. An exemplary configuration of a digital wireless microphone system when error detection is performed on a plurality of samples is shown in FIG.

  FIG. 4 (a) is a block diagram of a digital wireless microphone transmitter 102 of the second embodiment of the present invention, and FIG. 4 (b) is a block diagram of a digital wireless microphone receiver 202 of the second embodiment. FIG.

  The transmitter 102 of the digital wireless microphone includes an information source coding unit 11, a multiple sample buffer unit 18, a priority bit error detection coding unit 17, an error correction coding unit 13, a modulation unit 14, and a power amplification unit. And a transmitting antenna 16. The transmitter 102 of the second embodiment differs from the transmitter 101 of the first embodiment in that a multiple sample buffer unit 18 is added to the transmitter 101 of FIG. 1A. The description of the same configuration as that of the first embodiment or the prior art will be simplified.

  The source coding unit 11 performs source coding on the input voice signal.

  The multiple sample buffer unit 18 holds the digital audio signal encoded by the information source encoding unit 11 for a predetermined number of samples. It is desirable that the number of samples to be held be the number of samples to be subjected to error detection coding in the next priority bit error detection coding unit 17. When the digital audio signal is accumulated for a predetermined number of samples (the number of samples to be subjected to the priority bit error detection coding collectively), the multiple sample buffer unit 18 causes the next priority bit error detection coding unit 17 to A number of digital audio signals can be transferred together.

  The priority bit error detection coding unit 17 of FIG. 4A performs priority bit error detection coding over a digital audio signal of a plurality of samples (that is, combining a plurality of samples).

  An overview of priority bit error detection coding for two speech samples is described with reference to FIG. As in FIG. 2 used as an example of the first embodiment, an example of a bit configuration in which 22 bits of information source encoding are performed on one sample of an audio signal and 4 bits of error detection code are added per sample is exemplified. Although explained, each bit number is not limited to this.

  In this embodiment, among the digital audio signals, a predetermined number of bits are set as priority bits in descending order of influence when errors occur (when errors remain), and priority bits of the digital audio signal of sample 1; The priority bits of the digital audio signal of sample 2 are put together (as one piece) and subjected to error detection coding. In the example of FIG. 5, for example, the upper 8 bits are set as the priority bits, and the higher priority bits (upper 8 bits) of sample 1 and the priority bits of sample 2 (upper 8 bits) are combined. Then, 8-bit error detection coding is performed by adding two sample error detection codes (4 bits each). That is, from the source-coded sample 1 and sample 2 22-bit digital audio signals, the upper 8-bit priority bits are extracted, and 16 bits of integrated data are combined for error detection. As target data, error detection coding is not performed on other bits (lower 14 bits, respectively) of the digital audio signal. Then, as encoded output, 8 bits of error detection code calculated for the priority bit (16 bits in total) for 2 samples with respect to the digital audio signal (22 bits), 4 bits for sample 1 and sample 2 The error detection coded digital audio signal is divided into 26 bits and added separately.

  The method of creating 16-bit data to be subjected to error detection encoding from the upper 8 bits can be determined as appropriate. For example, the upper 8 bits of sample 1 are followed by the upper 8 bits of sample 2 Alternatively, 16 bits of continuous data may be created by alternately arranging one bit each from the upper side of sample 1 and sample 2. In addition, a method of distributing the 8-bit error detection code obtained as a result of the error detection coding to sample 1 and sample 2 can also be set appropriately. When performing error detection decoding, it is sufficient if the 16 bits of priority bits to be subjected to error detection and the 8 bit error detection code can be reproduced from the samples 1 and 2 without error.

  The error correction coding unit 13 performs error correction coding on the output signal from the priority bit error detection coding unit 17 (a digital voice signal to which an error detection code is added). Further, as in the prior art, the modulation unit 14 performs signal modulation on the output signal from the error correction coding unit 13 according to a predetermined modulation scheme, and the power amplification unit 15 performs modulation on the modulated signal. Power amplification is performed and transmitted from the transmitting antenna 16 to the wireless propagation path.

  The digital wireless microphone receiver 202 shown in FIG. 4B includes a reception antenna 21, a reception amplifier 22, a demodulator 23, an error correction decoder 24, a multiple sample buffer 28, and priority bit error detection decoding. A unit 27 and an information source decoding unit 26 are provided. The receiving device 202 of the second embodiment is different from the receiving device 201 of the first embodiment in that a multiple sample buffer unit 28 is added to the receiving device 201 of FIG. The description of the same configuration as that of the first embodiment or the prior art will be simplified.

  As in the first embodiment, the reception amplification unit 22 performs reception power amplification on the signal received by the reception antenna 21, and the demodulation unit 23 demodulates the signal according to the demodulation method corresponding to the modulation method on the transmission side. To generate digital signal data from the received signal. Furthermore, the error correction decoding unit 24 performs error correction decoding by a method corresponding to the error correction code added on the receiving side.

  The multi-sample buffer unit 28 holds the error detection coded digital audio signal (a bit string of 26 bits each) decoded by the error correction decoding unit 24 by a predetermined number of samples. It is desirable that the number of samples to be held be the number of samples to be subjected to error detection decoding in the next priority bit error detection decoding unit 27. When the digital audio signal is accumulated for a predetermined number of samples (the number of samples to be subjected to priority bit error detection and decoding collectively), the multiple sample buffer unit 28 causes the next priority bit error detection / decoding unit 27 to Error detection coded digital audio signals can be transferred together.

  The priority bit error detection / decoding unit 27 shown in FIG. 4 (b) performs priority bit error detection decoding on a plurality of samples of error detection coded digital audio signals, and generates a digital audio signal and a priority bit of the digital audio signal. Outputs error detection information as to whether an error remains in (and an error detection code).

  The outline of the priority bit error detection decoding for two speech samples will be described based on FIG. From the bit string of each of 26 bits of the error detection coded sample 1 and sample 2 digital audio signals obtained as a result of the error correction decoding, the priority bit (here, the upper 8 bits) and the error detection code (4 bits) Is extracted as the range (target) of error detection. That is, 16 bits consisting of the priority bit (upper 8 bits) of sample 1 and the priority bit (upper 8 bits) of sample 2 and 8 bits error detection derived from the error detection code (2 bits each) of 2 samples The 24 bits combined with the code are subjected to error detection decoding as an error detection range, and errors contained in the 24 bits (whether errors remain after error correction decoding) are detected. Then, the digital voice signals of 22 bits each of sample 1 and sample 2 and error detection information (information indicating whether an error remains in 24 bits obtained by combining the priority bits of the two samples and the error detection code) are output. Be done.

  Thereafter, the information source decoding unit 26 performs information source decoding on the digital audio signal output from the priority bit error detection decoding unit 27 and restores the original audio signal. When the information that the error remains in the priority bit (and the error detection code) is output from the priority bit error detection / decoding unit 27, both digital audio signals of the two samples are not reproduced. This is because it can not be specified which of the two samples of the digital audio signal has an error. In this case, source digital decoding can be performed by performing necessary masking such as substituting two digital audio signals with other data.

  The effect in the case where error detection coding of only the priority bit is performed over two speech samples according to the second embodiment will be described. Generally, the error detection code has higher error detection capability as the number of added bits increases, but there is a restriction on the transmission rate of the bits that can be added. Therefore, if the error detection code is lengthened, digital voice signals The sound quality is degraded because the number of bits of V must be shortened. By performing error detection coding over a plurality of samples (for example, 2 samples), it is possible to increase the number of error detection coding bits to be added from 4 bits to 8 without changing the transmission rate of 26 bits per sample it can. In this case, the coding rate (R = k / n) is the same for the priority bit of one sample (8/12) and for the priority bit of two samples (16/24). In addition to the increase in the number of bits of the error detection code (for example, a CRC code can detect longer burst errors), the error is biased to one voice sample. Even if there is, it has the effect of increasing the possibility of detecting an error.

  When error detection coding is performed over a plurality of voice samples, error detection information is one in two samples, and mask processing using the error detection information is also in units of two samples. Therefore, error detection coding is performed once. There is a trade-off that if the number of samples to be performed is increased too much, the time for which the mask processing is performed will also be longer. Also, on the transmitting side, in order to perform error detection coding over a plurality of samples, it is necessary to wait for the arrival of all speech samples, which requires a buffer. Also, since it is necessary to perform error detection decoding over a plurality of samples on the receiving side as well, it is necessary to wait for the arrival of all audio samples, and a buffer is required. Therefore, there is a trade-off that increases delay for error detection coding and decoding.

  An OFDM digital wireless microphone is an example suitable for error detection coding of priority bits across multiple samples. OFDM is a type of multi-carrier transmission scheme, and by including OFDM modulation in the modulation section and OFDM demodulation in the demodulation section, a plurality of bits are transmitted at one time in one OFDM symbol. The digital wireless microphone of the OFDM system described in Non-Patent Document 1 performs transmission of four voice samples in one OFDM symbol (for example, a symbol simultaneously transmitted on 46 carriers). FIG. 6 shows an example of the bit configuration of speech samples in one OFDM symbol.

  An overview of the priority bit error detection coding for four speech samples will be described based on FIG. Among the digital audio signals, a predetermined number of bits are set as priority bits in descending order of influence when errors occur (errors remain), and the priority bits of the digital audio signals of sample 1 to sample 4 are combined ( Integrally, subject to error detection coding. In the example of FIG. 6, for example, the upper 8 bits are the priority bits and the error of 4 samples is compared with the 32 bits including the priority bits (upper 8 bits) of samples 1 to 4 as the audio bits having large influence. A 16-bit error detection coding is performed by adding up detection codes (4 bits each). That is, from the source-coded samples 1 to 4 of each 22-bit digital audio signal, the upper 8 priority bits are extracted, and the integrated data of 32 bits is combined with the error detection coding. As target data, error detection coding is not performed on other bits (lower 14 bits, respectively) of the digital audio signal. Then, 16 bits of the error detection code calculated for the priority bits of 4 samples (32 bits in total) are added to the digital audio signal (22 bits) separately in 4 bits in samples 1 to 4, The error detection coded digital audio signal is a 26-bit bit string.

  At the time of error detection decoding, the priority bits (here, the upper 8 bits) and the error detection code (4 bits) are extracted from the respective 26-bit bit strings of the error detected coded samples 1 to 4 of the digital audio signal. And the error detection range (target). That is, 48 bits including 32 bits consisting of priority bits (upper 8 bits) of sample 1 to sample 4 and 16 bit error detection code derived from 4 sample error detection codes (4 bits each) are Error detection decoding is performed as a range of error detection, and an error (whether an error remains after error correction decoding) contained in the 48 bits is detected. Then, each of the 22 bits of the digital audio signal of samples 1 to 4 and one error detection information (information indicating whether an error remains in 48 bits obtained by combining the priority bits of the four samples and the error detection code) Is output. In this example, the error detection code can be 16 bits, and extremely accurate error detection is possible.

  The data in one OFDM symbol in FIG. 6 is divided into two sets, and the priority bit of the digital audio signal of sample 1 and the priority bit of the digital audio signal of sample 2 are combined as shown in FIG. As a target of error detection coding, and may be a target of error detection coding by combining the priority bit of the digital audio signal of sample 3 and the priority bit of the digital audio signal of sample 4 .

  In order to transmit four speech samples in one OFDM symbol, it is not necessary to wait for the arrival of the next symbol even if error detection coding of priority bits is performed over two speech samples or four speech samples. Therefore, there is no delay in waiting for data.

  In each of the above-described embodiments, based on an example in which 22 bits of information source encoding and 4 bits of error detection encoding are performed at a transmission rate of 26 bits per audio sample, and 8 bits are selected as priority bits. Although the description has been made, the embodiment is not limited to these transmission rates and the number of bits. The priority bits may be, for example, 6 bits or 12 bits. The number of bits of the error detection code can be set as appropriate, although there is a trade-off relationship with the number of bits of the digital audio signal. In addition, although an example of 2 samples or 4 samples has been described as an example in which error detection coding of priority bits is performed over a plurality of samples, the number of samples is not limited as an embodiment.

  Furthermore, although the above-described embodiment has been described as a representative example, it is obvious to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes are possible without departing from the scope of the claims. For example, it is possible to combine a plurality of configuration blocks described in the embodiment into one, or to divide one configuration block.

100, 101, 102 Transmitter 11 Source coding unit 12 Error detection coding unit 13 Error correction coding unit 14 Modulation unit 15 Power amplification unit 16 Transmission antenna 17 Priority bit error detection coding unit 18 Multiple sample buffer unit 200, 201, 202 receiver 21 reception antenna 22 reception amplifier 23 demodulation unit 24 error correction decoding unit 25 error detection decoding unit 26 source decoding unit 27 priority bit error detection decoding unit 28 multiple sample buffer unit

Claims (3)

A transmitter of a digital wireless microphone for transmitting a linear PCM signal, which is an uncompressed digital audio signal, according to the OFDM method, comprising: an information source encoding unit for converting the audio signal to the digital audio signal; What is claimed is: 1. A transmitter of a digital wireless microphone, comprising: a detection coding unit; an error correction coding unit performing error correction coding; and a modulation unit performing signal modulation by an OFDM modulation method,
The error detection coding unit transmits a single OFDM symbol with a predetermined number of upper bits as priority bits in descending order of the degree of influence of the output level of the audio signal among errors in the digital audio signal. integrally the priority bit of the plurality of digital audio signals among the audio samples, to the priority bits an integral, have rows error detection coding and error detection coding of the priority bits an integral The digital audio signal is transferred together by the number of samples to be
The digital wireless network characterized in that the error correction coding unit performs error correction coding on the entire output from the error detection coding unit in which the error detection coding has been performed on the priority bits. Microphone transmitter. A receiver of a digital wireless microphone for transmitting a linear PCM signal which is an uncompressed digital audio signal according to the OFDM method, a demodulator for demodulating a received modulated signal, and an error correction decoder for error correction decoding of the demodulated signal In a receiver of a digital wireless microphone, the digital wireless microphone receiver comprising: an error detection and decoding unit that performs error detection and decoding; and an information source decoding unit that converts a digital audio signal into an audio signal.
The error detection and decoding unit receives a signal in which error detection coding has been performed on a priority bit having a high degree of influence that contributes to the output level of the audio signal when an error occurs in the digital audio signal . There line error detection decoding as an integrated said predetermined number upper bits of a prioritized bit of the plurality of the digital audio signal among the audio samples to be transmitted at OFDM symbol, and the error detection decoding of the priority bits an integral An apparatus for receiving a digital wireless microphone, wherein the digital voice signals error-corrected and decoded by the number of samples to be performed are collectively transmitted . A system of a digital wireless microphone for transmitting a linear PCM signal which is an uncompressed digital voice signal according to the OFDM method, comprising at least an error detection coding unit for performing error detection coding and error correction coding on the transmission side. A digital wireless microphone system comprising: an error correction coding unit to perform, an error correction decoding unit that performs error correction decoding, and an error detection decoding unit that performs error detection decoding on the reception side;
Of the digital audio signal, a predetermined number of upper bits of the descending order of contributing influence on the output level of the audio signal when an error occurs as priority bits, the error detection coding unit is transmitted in one OFDM symbol speech The number of samples for which error detection coding is performed on the priority bits integrated with the priority bits of a plurality of digital audio signals of a plurality of samples and error detection coding of the priority bits integrated The digital voice signal is collectively transferred, and the error correction coding unit performs error correction coding on the entire output from the error detection coding unit that has performed error detection coding on the priority bit. ,
There line error detection decoding integrally the upper bits of the predetermined number is a priority bit of the plurality of the digital audio signal among the audio samples to transmitting the error detection decoding section in one OFDM symbol, and, To integrally A system of a digital wireless microphone characterized in that the digital voice signals error-corrected and decoded by the number of samples for error detection decoding of the priority bits are transferred together .

Images