JP4078544B2 - Audio data transmission device and audio data reception device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for transmitting audio data such as telephone call audio data and an apparatus for receiving audio data.
[0002]
[Prior art]
For example, when transmitting voice data such as call voice over a narrow band data transmission path, such as wireless communication using Bluetooth using a frequency hopping (FH) modulation scheme, There is a problem that an error occurs in the transmission data due to a collision with the transmission data, and this appears as noise of the reproduced voice.
[0003]
In order to solve this problem, conventionally, measures such as adopting a protocol for retransmitting audio data when an error occurs have been taken (see, for example, JP-A-11-340956 (Patent Document 1)). .
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-340956
[Problems to be solved by the invention]
However, when resending is performed when an error occurs, voice information such as call voice for a certain time or more needs to be stored in a memory or the like in advance, and a relatively large delay occurs. There is a disadvantage that it is not suitable as a voice transmission system.
[0006]
In view of the above points, the present invention provides an apparatus capable of avoiding the influence of an occurrence error and obtaining good reproduction voice quality with less noise and delay even in transmission of voice data in a narrow transmission band. Objective.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, in the invention of claim 1,
Data compression means for compressing the digital audio signal every predetermined time to 1 / M (M>2);
Error detection code generation and addition means for generating and adding an error detection code to the digital audio signal compressed every predetermined time by the data compression means to form a compressed audio unit block;
A frame of a data transmission unit is obtained by adding a header and data arrangement information of the compressed audio unit block to continuous K (K is an integer of 2 or more, K <M) of the compressed audio unit blocks. Generating the data, discarding the oldest temporal block of the continuous K compressed audio unit blocks and adding the latest one, and adding the frame data to the predetermined data And a frame synthesis unit that sequentially updates every time,
The arrangement information is modulo data of modulo K,
There is provided an audio data transmission apparatus configured to transmit the sequentially updated frame data from the frame synthesis unit.
[0008]
[Action]
According to the first aspect of the present invention, the digital audio signal is data-compressed to 1 / M every predetermined time, an error detection code is generated and added to the compressed audio data, and a compressed audio unit is obtained. A block is formed. Then, header data and arrangement information are added to K consecutive compressed audio unit blocks to generate frame data.
[0009]
The frame data is updated every predetermined time by discarding the oldest temporally block of the K compressed audio unit blocks that are continuous and adding the latest one.
[0010]
Accordingly, audio data of the same compressed audio unit block is included in continuous K frame data. That is, the audio data of the same compressed audio unit block is transmitted K times.
[0011]
For this reason, on the receiving side of the transmission data, the audio data without error is extracted by extracting the audio data of the compressed audio unit block sent K times, in which no error is detected by the error detection code. Can be obtained. It can be determined by referring to the arrangement information where the compressed audio unit block having no error is arranged in the frame data.
[0012]
In this case, since the audio data is compressed and included as K compressed audio unit blocks in one frame, the delay can be fixed K frames, and a small delay amount is sufficient. There is an effect.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an audio data transmission apparatus and audio data reception apparatus according to the present invention will be described below with reference to the drawings.
[0014]
[Embodiment of Audio Data Transmission Device]
FIG. 1 is a block diagram showing an embodiment of an audio data transmission apparatus according to the present invention. In this example, call voice data is transmitted by wireless transmission.
[0015]
For example, an analog audio signal Sa obtained by collecting sound with a microphone or the like is encoded after being converted into a digital audio signal by the A / D converter 1 based on a sampling clock signal from the timing signal generator 11. The signal is supplied to the unit 2 and converted into, for example, a PCM signal of 64 Kbps.
[0016]
Then, the PCM signal from the encoding unit 2 is supplied to the data compression unit 3, and the data is 1 / M (M> 2) for each audio data block for a predetermined time T, for example, T = 3.75 msec. Compressed and time compressed to 1 / M hour worth of data. In this example, M = 4.
[0017]
As will be described later, the predetermined time T is equal to the transmission period of frame data which is transmission unit data in this example. Therefore, in the following description, the predetermined time T is referred to as a frame period.
[0018]
The compressed audio block data from the data compression unit 3 is supplied to the error detection code generation / addition unit 4, and an error detection code is generated and added to each of the compressed audio block data. The compressed audio block data to which an error detection code is added is referred to as a compressed audio unit block. In this example, a CRC (Cyclic Redundancy Check) code is used as the error detection code.
[0019]
Although not shown, the processing signal is supplied from the timing signal generator 11 to the encoder 2, the data compressor 3, and the error detection code generator / adder 4.
[0020]
In this embodiment, as will be described later, one frame of data, which is a data transmission unit, is formed by including K compressed audio unit blocks (K is an integer equal to or greater than 2 and K <M). Like that. In this example, K = 3. Therefore, in this embodiment, it is necessary to store three compressed audio unit blocks.
[0021]
Therefore, in the transmission apparatus of FIG. 1, three compressed audio unit block storage units 50, 51, and 52 are provided. These three compressed audio unit block accumulating units 50, 51, 52 are connected in series, and are connected to the input side by a timing signal synchronized with the frame period T from the timing signal generating unit 11. The compressed audio unit block data stored in the audio unit block storage unit is transferred to the compressed audio unit block storage unit.
[0022]
In other words, in the example of FIG. 1, the compressed audio unit block data from the error detection code generation / addition unit 4 is supplied to the compressed audio unit block storage unit 50, and the compressed audio unit block data from the compressed audio unit block storage unit 50 is supplied. The block data is supplied to the compressed audio unit block accumulating unit 51, and the compressed audio unit block data from the compressed audio unit block accumulating unit 51 is supplied to the compressed audio unit block accumulating unit 52. The
[0023]
Further, the compressed speech unit block data XT0, XT1, XT2 of the three compressed speech unit block storage units 50, 51, 52 are configured to be supplied to the frame synthesis unit 6 simultaneously.
[0024]
Then, as shown in FIG. 2, the data of the audio block for the frame period T is compressed in the data compression unit 3, and the error detection code generation / addition unit 4 converts the compressed audio block into the error detection code. The data of the compressed audio unit block to which is added is written to the compressed audio unit block storage unit 50 by the timing signal from the timing signal generation unit 11 every frame period T.
[0025]
In FIG. 2, N, N + 1, N + 2,... Indicate the numbers when numbers are sequentially assigned to the audio block data for one frame period. The same applies to FIGS. 3 and 5 described later.
[0026]
Prior to the writing of the compressed audio unit block data to the compressed audio unit block storage unit 50, the compressed audio unit block data stored in the compressed audio unit block storage unit 50 by the timing signal from the timing signal generator 11. Is transferred to the compressed audio unit block storage unit 51, and the data of the compressed audio unit block stored in the compressed audio unit block storage unit 51 is transferred to the compressed audio unit block storage unit 52. At this time, the data stored up to that point in the compressed audio unit block storage unit 52 is discarded.
[0027]
Therefore, as shown in FIG. 2, the latest compressed audio unit block data TX0 is accumulated in the compressed audio unit block accumulating unit 50, and the compressed audio unit block T before one frame period T is accumulated in the compressed audio unit block accumulating unit 51. The block data TX1 is accumulated, and the compressed audio unit block accumulating unit 52 accumulates the data TX2 of the compressed audio unit block two frames before T.
[0028]
When the latest compressed audio unit block data TX0 is accumulated in the compressed audio unit block accumulating unit 50, the accumulated data TX0, TX1, and TX2 of the three compressed audio unit block accumulating units 50 to 52 are stored in the frame synthesizing unit. 6 is transferred.
[0029]
Further, based on the timing signal of the frame period T from the timing signal generator 11, the header and modulo data creation unit 7 creates header information and modulo data for frame data that is transmission unit data, and creates the created header. Information and modulo data are supplied to the frame synthesis unit 6.
[0030]
The header and modulo data creation unit 7 generates modulo K, in this example, modulo 3 modulo data based on the timing signal of the frame period T from the timing signal generation unit 11. The modulo data is information indicating the accumulated data TX0, TX1, TX2 and the data delay relationship of the compressed audio unit block. That is, the modulo data is information indicating the correspondence relationship between the data of a certain compressed audio unit block and the stored data TX0, TX1, TX2.
[0031]
Based on the timing signal of the frame period T from the timing signal generator 11, the frame synthesizer 6 stores the accumulated data TX0, TX1, TX2 from the three compressed audio unit block accumulators 50 to 52 for each frame period T. Then, frame data is generated by adding a header and modulo data.
[0032]
A configuration example of the frame data is shown in FIG. That is, as shown in FIG. 3A, the header and modulo data are arranged at the head of the frame data in this example, and thereafter, the accumulated data TX2, TX1, and TX0 are arranged in this order.
[0033]
The frame data is created at the frame period T. As described above, the accumulated data TX2, TX1, and TX0, which are continuous K = 3 compressed audio unit blocks, are the most in time for each frame period T. Since the old compressed audio unit block is discarded and the latest compressed audio unit block is added, the content of the frame data generated in the frame period T depends on the change of the accumulated data TX2, TX1, TX0. Updated.
[0034]
Therefore, as can be seen from FIGS. 2 and 3, each compressed audio unit block is transmitted once in one frame period, but is transmitted three times in three frame periods.
[0035]
As described above, in the case of this embodiment, the same compressed audio unit block is transmitted over a period of 3 frames. However, in which arrangement position in the frame data the compressed audio unit block exists. , Modulo data is supported. Therefore, the modulo data is arrangement information of one compressed audio unit block in the frame data.
[0036]
Since the modulo data is modulo 3 in this example, three types of data [0], [1], and [2] can be taken. The correspondence relationship between the three types of modulo data and the compressed audio unit block data is as shown in FIGS. 3B, 3C, and 3D.
[0037]
For example, paying attention to the Nth compressed audio unit block, as shown in FIG. 3B, when it is included in the compressed audio unit block TX0 and arranged at the end of the frame data, the modulo data is , [0].
[0038]
As shown in FIG. 3C, when the Nth compressed audio unit block is included in the compressed audio unit block TX1 and arranged at the center of the frame data, the modulo data is [1]. is there. As shown in FIG. 3D, when the Nth compressed audio unit block is included in the compressed audio unit block TX2 and arranged at the beginning of the frame data, the modulo data is [2]. is there. Therefore, by referring to the modulo data, the arrangement position of the compressed audio unit block in the frame data can be determined.
[0039]
The frame data generated as described above is supplied from the frame synthesis unit 6 to the modulation unit 8 and is modulated by, for example, a frequency hopping modulation method. Then, the modulated frame data is transmitted from the transmission unit 9 through the transmission antenna 10.
[0040]
[Embodiment of Audio Data Receiving Device]
FIG. 4 is a block diagram showing an embodiment of an audio data receiving apparatus according to the present invention. In this example, call voice data wirelessly transmitted from the voice data transmission apparatus having the configuration shown in FIG. 1 is received and reproduced.
[0041]
Frame data received by the antenna 21 is supplied to the demodulation unit 23 through the reception unit 22, demodulated, and then supplied to the frame decomposition unit 24.
[0042]
The frame decomposing unit 24 separates each of the three compressed audio unit blocks and the modulo data from the frame data, and each of the three compressed audio unit block data is stored in the compressed audio unit block memories 250, 251 and 251. The modulo data is written to the modulo data memory 26.
[0043]
In this example, the compressed audio unit block memory 252 is written with the compressed audio unit block immediately after the header of the frame data, and the compressed audio unit block memory 251 has the compressed audio unit block arranged at the center of the frame data. And the compressed audio unit block arranged at the end of the frame data is written in the compressed audio unit block memory 250.
[0044]
When the compressed audio unit block data is written in the compressed audio unit block memories 250, 251, 252, the respective compressed audio unit blocks are read from the compressed audio unit block memories 250, 251, 252 and the error detection unit 270. , 271 and 272 respectively.
[0045]
In each of the error detection units 270, 271, and 272, in this example, an error check is performed to determine whether or not there is an error in the compressed audio data using the CRC code included in the compressed audio unit block. Then, each of the error detection units 270, 271, and 272 receives the compressed audio data RX0, RX1, and RX2 included in the compressed audio unit block and the error check results ED0, ED1, and ED2 based on the CRC code, and the buffer memory control unit 28. To supply.
[0046]
The modulo data stored in the modulo data memory 26 is also supplied to the buffer memory control unit 28.
[0047]
The buffer memory control unit 28 determines the arrangement position of the compressed audio unit block data on the frame data based on the modulo data, and each of the compressed audio data RX0, RX1, and RX2 is the compressed audio data at any delay timing. Determine if it exists. That is, for example, when the modulo data is [0], the compressed audio unit block data arranged at the end of the frame data is arranged at the center of the frame data when the modulo data is [1]. When the data is [2], it is determined that the data is arranged immediately after the header of the frame data.
[0048]
Then, among the compressed audio data sent three times, the compressed audio data determined to have no error by the CRC check is transferred to the buffer memory 29, and the compressed audio data written in the buffer memory 29 is read out. When the order is reached, the data is read from the buffer memory 29 and transferred to the data decompression unit 30.
[0049]
In the case of this example, the buffer memory control unit 28 writes the compressed audio data first determined not to have an error among the same compressed audio data sent three times to the buffer memory 29, and then arrives the same. The writing of the compressed audio data to the buffer memory 29 is stopped (prohibited).
[0050]
In this case, the buffer memory control unit 28 monitors the modulo data at the time of transferring the data of the compressed audio unit block to the buffer memory 29, thereby transferring the data of the compressed audio unit block up to the buffer memory 29. The compressed audio data to be written next to the buffer memory 29 is recognized, the error check result for the compressed audio data is referred to, and the error-free data is stored in the buffer memory 29. Try to write.
[0051]
For example, the processing in the buffer memory control unit 28 for the Nth compressed audio data block will be described as shown in FIG.
[0052]
As shown in FIG. 5, the Nth compressed audio data block first appears at the last position of the frame data. At that time, the Nth compressed audio data block is supplied to the buffer memory control unit 28 as compressed audio data RX0 from the error detection unit 270. The The modulo data at this time is [0].
[0053]
When it is determined that there is no error in the compressed audio data RX0 as a result of referring to the error check result ED0 input in accordance with the buffer memory 28 at this time, the buffer memory control unit 28 stores the compressed audio data RX0 in the buffer memory 29. And the subsequent writing of the same compressed audio data to the buffer memory 29 is stopped.
[0054]
In FIG. 5, as indicated by a broken line, the buffer memory control unit 28 reads out the compressed audio data RX <b> 0 at the time after three frame periods and transfers it to the data decompression unit 30.
[0055]
When it is determined that the compressed audio data RX0 includes an error based on the error check result ED0, the buffer memory control unit 28 refers to the error check result ED1 for the compressed audio data RX1 in the next frame period. . The modulo data at this time is [1].
[0056]
When it is determined that there is no error in the compressed audio data RX1 as a result of referring to the error check result ED1, the buffer memory control unit 28 transfers the compressed audio data RX1 to the buffer memory 29 and thereafter performs the same compression. Writing of the audio data to the buffer memory 29 is stopped.
[0057]
In FIG. 5, as indicated by a solid line, the buffer memory control unit 28 reads the compressed audio data RX1 at a time point after two frame periods and transfers it to the data decompression unit 30. Note that the compressed audio data RX1 used at this time is already delayed by one frame period on the transmission side, so that when viewed from the original audio data, it is delayed by three frame periods as in the case of the compressed audio data RX0. Equal to being played.
[0058]
When it is determined that the error is included in the compressed audio data RX1 based on the error check result ED1, the buffer memory control unit 28 refers to the error check result ED2 for the compressed audio data RX2 in the next frame period. The modulo data at this time is [2].
[0059]
When it is determined that there is no error in the compressed audio data RX2 as a result of referring to the error check result ED2, the buffer memory control unit 28 transfers the compressed audio data RX2 to the buffer memory 29.
[0060]
In FIG. 5, the buffer memory control unit 28 reads the compressed audio data RX2 at a time point after one frame period and transfers it to the data decompression unit 30 as indicated by a one-dot chain line. Note that the compressed audio data RX2 used at this time is already delayed by 2 frame cycles on the transmission side, and therefore, when viewed from the original audio data, it is delayed by 3 frame cycles as in the case of the compressed audio data RX0. Equal to being played.
[0061]
If any of the compressed audio data RX0, RX1, and RX2 is determined to have an error as a result of the error check, for example, the frame is set to be silent data.
[0062]
As described above, in the data decompression unit 30 controlled by the buffer memory control unit 28 and transferred with compressed audio data having no error, the compressed audio data is decompressed and the original digital audio data having the original time length is obtained. Is supplied to the decoding unit 31. In the decoding unit, after the PCM data is decoded, the D / A converter 32 returns the analog voice signal to reproduce the call voice. The reproduced call voice is supplied to a speaker (not shown) and is reproduced acoustically.
[0063]
Also on the receiving device side, various timing signals from the timing signal generator 33 are supplied to each unit. Although not shown, the timing signal generator 33 is synchronized with the received frame data, and performs the above-described decoding process of the frame data in units of the frame period T. Synchronization is performed, and the above-described frame data decomposition processing is performed in the frame decomposition unit.
[0064]
As described above, according to the above-described embodiment, the audio data of the same compressed audio unit block is transmitted three times, and there is no error in the audio data of the compressed audio unit block transmitted three times. Only the audio data is targeted for decoding, the compression is decompressed, and the audio is reproduced after being decoded. Therefore, it is possible to obtain a reproduced sound with less noise due to an error. In addition, since the delay amount may be three frame periods, there is an effect that it can be reduced.
[0065]
[Modification]
In the above embodiment, M = 4 and K = 3. However, this is only an example, and any value that satisfies M> 2 and K <M may be used. Note that K needs to be an integer value, but M may be a decimal value.
[0066]
In the above example, the present invention is applied to the case of wireless communication using frequency hopping modulation. However, the present invention can be applied to all cases in which voice data is transmitted through a data transmission path of a narrow band. The road may be wireless or wired. Needless to say, the voice data is not limited to the call voice.
[0067]
The frame data may be data having a time length equal to or shorter than one frame period T, and can also be referred to as packet data.
[0068]
In the above example, the error detection code is a CRC code that is an error detection code. However, other error detection codes can be used, and an error detection and correction code can also be used. In the case of using an error detection and correction code, a compressed audio unit block that has been detected and corrected by error can be used for decoding, assuming that it has been received correctly.
[0069]
Further, the arrangement information in the frame data of the data of the compressed audio unit block is not limited to the modulo data, and if it is identification information that can specify the arrangement relationship in the frame data of the K compressed audio unit blocks, Any information may be used.
[0070]
【The invention's effect】
As described above, according to the present invention, audio data of the same compressed audio unit block is included in K consecutive frame data and transmitted K times. For this reason, on the receiving side of the transmission data, the audio data without error is extracted by extracting the audio data of the compressed audio unit block sent K times, in which no error is detected by the error detection code. Can be obtained.
[0071]
In this case, since the audio data is compressed and included as K compressed audio unit blocks in one frame, the delay can be fixed K frames, and a small delay amount is sufficient. There is an effect.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an audio data transmission apparatus according to the present invention.
FIG. 2 is a diagram for explaining an embodiment of an audio data transmission apparatus according to the present invention;
FIG. 3 is a diagram showing an example of the structure of frame data used in the embodiment of the audio data transmission apparatus according to the present invention.
FIG. 4 is a block diagram showing an embodiment of an audio data receiving apparatus according to the present invention.
FIG. 5 is a diagram for explaining the operation of the embodiment of the audio data receiving apparatus according to the present invention;
[Explanation of symbols]
3 Data compression unit 4 Error detection code generation addition unit 50, 51, 52 Compressed speech unit block storage unit 6 Frame synthesis unit 7 Header and modulo data creation unit 24 Frame decomposition unit 250, 251, 252 Compressed speech unit block memory 26 Modulo Data memory 270, 271, 272 Error detection unit 28 Buffer memory control unit 29 Buffer memory 30 Data decompression unit

Claims (2)

Data compression means for compressing the digital audio signal every predetermined time to 1 / M (M>2);
Error detection code generation and addition means for generating and adding an error detection code to the digital audio signal compressed every predetermined time by the data compression means to form a compressed audio unit block;
A frame of a data transmission unit is obtained by adding a header and data arrangement information of the compressed audio unit block to continuous K (K is an integer of 2 or more, K <M) of the compressed audio unit blocks. Generating the data, discarding the oldest temporal block of the continuous K compressed audio unit blocks and adding the latest one, and adding the frame data to the predetermined data A frame composition unit that updates the data sequentially with time, and
The arrangement information is modulo data of modulo K,
An audio data transmission device characterized in that the sequentially updated frame data from the frame synthesis unit is transmitted. K consecutive compressed audio unit blocks (K is 2 or more) formed by generating and adding an error detection code to a digital audio signal for each predetermined time that is data-compressed to 1 / M (M> 2) Frame data in which an arrangement information is added to a header and data of the compressed audio unit block with respect to K <M), and the time among the continuous K compressed audio unit blocks In the audio data receiving device for receiving the frame data sequentially updated at every predetermined time, the oldest one is discarded and the latest one is added,
Separating means for separating each of the continuous K compressed audio unit blocks from the frame data and the arrangement information;
K accumulating units for accumulating each of the compressed audio unit blocks separated by the separating unit;
K error detection means for performing error detection on the compressed speech unit block by the error detection code added to each of the compressed speech unit blocks stored in the K storage units;
Data decompression means for decompressing the compression of the audio data of the compressed audio unit block;
Based on the error detection result from the K error detection means and the separated arrangement information, the audio data of the compressed audio unit block without error is prohibited from being written to the buffer memory in the same audio data. Buffer memory control means for temporarily storing and supplying the compressed voice unit block audio data from the buffer memory to the data decompression means sequentially in the original time order;
And the arrangement information is modulo K modulo data .

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