JP2002268691A - Method and device for voice data reception - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of excessive or insufficient data when digital voice data are asynchronously transmitted, through simple processing and constitution. SOLUTION: A transmission device is equipped with a compressing means which compresses and encodes voice data sampled at a specific sampling frequency, a storage means which stores the voice data temporarily compressed by the compressing means, a transmitting means which sends the voice data stored in the storage means to a specific transmission line, and a control means which varies and sets the compressibility of compressive encoding by the compressing means according to the storage amount of the voice data in the storage means. A reception device, on the other hand, is equipped with a receiving means which receives the compressed and encoded voice data, an expanding means which expands the received voice data from the compressive encoding state to the original rate, and a control means which judges the compressibility of the voice data from auxiliary data added to the voice data received by the receiving means and makes the expanding means perform the expansion processing corresponding to the judged compressibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an audio data transmitting apparatus and an audio data receiving apparatus applied to a transmitting side and a receiving side when digital audio data is transmitted in an asynchronous state between a transmitting side and a receiving side.

[0002]

2. Description of the Related Art In recent years, various short-distance wireless transmission systems having a transmission distance of up to several tens of meters have been developed, and digital audio data is wirelessly transmitted in a home or the like using such a wireless transmission system. Have been proposed and are being put to practical use.

FIG. 7 is a diagram showing a configuration example of a conventional transmitting side and a receiving side for wirelessly transmitting digital audio data.
In this example, an audio signal source 81 for outputting an audio signal is provided in the transmitting device 80. As the audio signal source 81, for example, a CD (compact disk)
For example, a reproduction apparatus for a digital audio data recording medium such as a digital broadcast, a tuner for receiving digital broadcasting, and the like can be considered. The digital audio signal output from the audio signal source 81 is supplied to a compression circuit 82 and is converted into audio data that has been compression-encoded for wireless transmission. The compression-encoded audio data is supplied to a transmission circuit 83, which performs modulation processing for transmission, frequency conversion to a transmission frequency, and the like, and wirelessly transmits the data from an antenna 84.

In a receiving device 90 for receiving a radio signal from a transmitting device 80, a receiving circuit 9 to which an antenna 91 is connected is connected.
In 2, the signal of a predetermined frequency is frequency-converted into an intermediate frequency signal (or baseband signal), and the frequency-converted received signal is demodulated. The demodulated received signal is supplied to a decompression circuit 93, which performs decoding for decompressing the data compressed and encoded at the time of transmission to the original data. Expansion circuit 9
By the decoding in step 3, digital audio data having the original constant sampling frequency is obtained. The digital audio data decoded by the decompression circuit 93 is output to an error detection / correction circuit 9.
4 to perform error detection and correction of the data using an error detection (correction) code or the like added to the audio data.

[0005] The digital audio data with the error corrected is supplied to a digital / analog converter 95 to be converted into an analog audio signal. The converted analog audio signal is supplied to an audio output circuit 96 that performs analog processing such as amplification, and outputs audio from left and right two-channel speakers 97L and 97R connected to the audio output circuit 96.

[0006]

In such conventional transmission processing, as a measure against transmission errors, an error correction code is added to transmission data on the transmission side, and a check using the error correction code on the reception side is performed. Error detection and correction were performed. By the way, in the case of so-called asynchronous transmission in which the sampling rate of the digital audio data to be transmitted and the transmission rate of the wireless transmission system are set asynchronously, the clock frequency of the audio data handled on the transmission side,
It is difficult to completely equalize the clock frequency of audio data handled on the receiving side, and a slight shift occurs. This slight difference in clock frequency is basically no problem in terms of reproduction sound quality, etc., but from the viewpoint of data processing, the difference in sampling frequency between the transmission side and the reception side indicates that the data on the reception side is excessive or insufficient. Will come. Also, the actual transmittable data rate may change due to retransmission of an error frame or the like.

That is, if the sampling frequency at which analog conversion is performed at the receiving side is slightly lower than the sampling frequency at the transmitting side, the amount of data stored in the buffer memory or the like at the stage before analog conversion is reduced at the receiving side. It increases by one. Such a problem is not a problem in a short transmission, but for example, if it is continuously transmitted for tens of minutes,
The buffer memory of the receiving side overflows,
The sound received and output is interrupted temporarily.

On the other hand, if the sampling frequency for performing analog conversion on the receiving side is slightly higher than the sampling frequency on the transmitting side, the amount of data stored in a buffer memory or the like at the receiving side before the analog conversion is performed. Gradually decreases, and in continuous transmission, the data stored in the buffer memory provided on the receiving side is lost, resulting in an underflow, and the sound received and output is also temporarily interrupted.

As described above, when digital audio data is transmitted asynchronously, the sampling rate of the audio data and the transmission rate are asynchronous, so that there is a problem of excessive or insufficient audio data on the receiving side.

[0010] In view of the above, the present invention solves the problem of excessive or insufficient data when asynchronously transmitting digital audio data.
The purpose is to solve the problem with a simple process and configuration.

[0011]

An audio data transmitting apparatus according to the present invention comprises a compression means for compressing and encoding audio data sampled at a predetermined sampling frequency, and a storage for temporarily storing the audio data compressed by the compression means. Means, transmission means for transmitting the audio data stored in the storage means to a predetermined transmission path, and control for variably setting the compression ratio of the compression encoding in the compression means based on the amount of audio data stored in the storage means. Means.

According to the audio data transmitting apparatus of the present invention, the audio compression ratio is variably set according to the transmission state at that time, and the temporary storage amount in the storage means provided in the transmitting apparatus is set within a predetermined range. Can be.

The audio data receiving apparatus according to the present invention comprises: a receiving means for receiving compression-encoded audio data; an expansion means for expanding the audio data received by the receiving means from the compression encoding to the original rate; And control means for judging the compression rate of the audio data from the auxiliary data added to the audio data received by the means, and causing the decompression means to execute decompression processing corresponding to the judged compression rate.

According to the audio data receiving apparatus of the present invention, even if the compression coding rate of the transmitted audio data is variably set, correct decompression processing is performed based on the instruction of the auxiliary data added to the received audio data. Can be extended to the original rate.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to FIGS.

In this embodiment, the present invention is applied to a system for wirelessly transmitting digital audio data by asynchronous transmission. As a wireless transmission system for performing the asynchronous transmission, a wireless transmission system of a standard called Bluetooth is applied here. This standard is for wireless transmission of audio data, image data, computer data, and the like between a plurality of devices using a 2.4 GHz frequency band. The wireless transmission distance between the devices is assumed to be a relatively short distance network from several meters to at most about 100 m. For each type of data to be transmitted, a profile is defined which defines how the data is transmitted. Standardization of profiles for transmitting digital audio data for high-quality audio reproduction is also underway.

The wireless transmission system of the Bluetooth standard will be described. Such wireless transmission is one in the 2.4 GHz band.
Transmission is performed on channels set at MHz intervals. However, the signal of each channel is subjected to a process called frequency hopping in which a transmission frequency is changed at a slot interval described later. If frequency hopping is performed for each slot, one slot is 625 μm.
Since it is seconds, the frequency is switched 1600 times per second, and interference with other wireless communication is prevented. As a modulation method of the wireless transmission signal, GFSK (Gaussian f
A modulation scheme called “ilterd FSK” is applied. This modulation method is a frequency shift keying method in which the frequency transfer characteristic is band-limited by a low-pass filter having a Gaussian distribution.

[0018] In the Bluetooth standard, TDD (Time Division Duple) that basically performs transmission and reception alternately.
x) The system is applied, and processing of transmission slots and reception slots are alternately arranged. That is, as shown in FIG. 2, for example, when one device performing wireless transmission is set as a master and the other device is set as a slave, 1
The data of the slot configuration is transmitted during the slot (625 μsec) (A in FIG. 2), and the data of the slot configuration is transmitted from the slave to the master during the next one slot (B in FIG. 2). Hereinafter, the alternate transmission is repeated as long as the transmission continues. However, the frequency for wireless transmission is changed to frequency f (k), f (k + 1), f (k + 2)... For each slot as described above. Note that a plurality of slots may be continuously used depending on the transmission rate at that time. The cycle at which this slot is transmitted is a cycle set independently of the sampling cycle of audio data described later.

FIG. 3 is a diagram showing a packet structure of one slot of data wirelessly transmitted according to the Bluetooth standard. As shown in FIG. 3A, a 72-bit access code is added to the head of one packet, followed by 5 bits.
A 4-bit header is added, and the remaining section is a payload that is actual transmission data. In the case of this example, audio data is arranged in the section of the payload. The section of the payload is set to a variable length according to the amount of data to be transmitted.

As shown in FIG. 3B, the access code is composed of a 4-bit preamble and a 64-bit sync word, and no data is arranged in the remaining sections. As shown in FIG. 3C, the header includes an address (AM ADR) for each device, a type representing the type of payload, and bits (FLOW, FLOW,
ARQN, SEQN) and an error check bit (HEC).

FIG. 4 is a diagram showing an example of the configuration of one frame of the audio data of the present example arranged in the payload section of each packet. In the case of this example, a header is arranged at the beginning of the audio data of one frame, and audio compressed data as audio data is arranged after the header. Then, auxiliary data is arranged in the last section. Various data accompanying the audio data is arranged in the auxiliary data. In this example, data relating to the compression ratio of the audio data arranged in the frame is also transmitted using the auxiliary data. I have to do it.

For details of the Bluetooth communication system, see Bluetooth SI, a standardization body that has established standards.
G has published.

Next, the configuration of the transmitting apparatus and the receiving apparatus of the present embodiment for transmitting voice data wirelessly by such a wireless transmission method will be described with reference to FIG. In the present example, the audio signal output from the audio signal source 11 built in the transmission device 10 is wirelessly transmitted to the reception device 30 and output from the audio signal output terminal 36 of the reception device 30.

First, the configuration of the transmitting device 10 will be described. In the transmitting device 10 of this embodiment, an audio signal source 11 for outputting an audio signal is prepared. Note that the audio signal source 11 may be configured separately from the transmission device 10, and the separate audio signal source may be connected to the transmission device 10.

The audio signal output from the audio signal source 11 is supplied to an analog / digital converter 12 and converted into digital audio data having a fixed sampling frequency. A clock supplied from the clock generation circuit 22 is used as a clock for conversion by the analog / digital converter 12. When the audio signal source 11 outputs digital audio data, the analog / digital converter 12 is not required.

The digital audio data output from the analog / digital converter 12 is supplied to a compression circuit 13 and compressed and encoded so that the audio data can be arranged in the above-mentioned payload section of the packet of the Bluetooth standard. Data. For example, the sampling frequency 44.1k
In order to transmit the digital audio data of two channels of 1 Hz in the packet of the Bluetooth standard described above,
It is necessary to compress the data at a transmission rate of about 00 kbps. However, in the case of the present example, the compression ratio at the time of compression encoding by the compression circuit 13 can be variably set within a certain range, and the compression ratio is determined by an instruction from the compression ratio setting circuit 21. It is like that. The compression ratio variably set is, for example, from 100 kbps to 700
It can be changed in the range of kbps. As a compression encoding method with a variable compression ratio, various known methods can be applied. For example, ATRAC (Adaptive Transfo
rmAcoustic Coding) compression method called 3 method, M
A compression method called a P3 method is applicable.

The compression-encoded audio data is supplied to a header adding circuit 14, where the header data and auxiliary data shown in FIG. 4 are added to the audio data to form frame-structured data. At this time, data of the compression ratio supplied from the control unit 20 described later is added to the auxiliary data.

The audio data frame-structured by the header adding circuit 14 is supplied to a buffer memory 15. The buffer memory 15 is configured as a first-in first-out (so-called FIFO) memory for temporarily storing audio data to be transmitted, and writing to this memory 15 is linked with the data output of the circuit 14 in the preceding stage. The reading from the memory 15 is performed in conjunction with the data transmission from the transmitting device 10. Writing and reading of data to and from the buffer memory 15 are executed under the control of the control unit 20 that controls the transmission operation of the transmission device 10. The control unit 20 performs control such that the amount of data temporarily stored in the buffer memory 15 is substantially constant within a predetermined range. A specific control processing example will be described in detail in the description of the transmission state described later.

The audio data in frame units read from the buffer memory 15 is supplied to the transmission processing circuit 17 via the first fixed contact 16a of the changeover switch 16. The changeover switch 16 is a switch for controlling the switching of the movable contact 16m under the control of the control unit 20.
Is connected to the fixed contact 16a, the output of the buffer memory 15 is supplied to the transmission processing circuit 17. In a normal operation state, the movable contact 16m is connected to the first fixed contact 16a.
Connected.

The output of the empty packet data storage unit 19 is supplied to the second fixed contact 16b of the changeover switch 16, and when the movable contact 16m is connected to the second fixed contact 16b, the empty packet data The free packet data stored in the storage unit 19 is supplied to the transmission processing circuit 17. The empty packet here is packet data in which no audio data is arranged.

In the transmission processing circuit 17, the changeover switch 16
Is transmitted as a transmission data having a packet structure of the Bluetooth standard shown in FIG. 3, and the transmission data is modulated into a signal to be transmitted from a predetermined transmission channel. Send. For the transmission processing in the transmission processing circuit 17, a clock generated by the clock generation circuit 23 is used. The clock for this transmission processing is the analog / digital converter 1
2 is asynchronous with the clock for modulation, and in the case of this example, there is no direct relationship between the frequencies of the two clocks.

Next, the configuration of the receiving apparatus 30 will be described. The transmission signal of a predetermined channel supplied to the receiving processing circuit 32 via the antenna 31 is transmitted to the receiving processing circuit 32.
, And extracts transmission data arranged in the payload section of each packet from the received signal and supplies it to the decompression circuit 33. The decompression circuit 33 performs decoding for decompressing the audio data compressed and encoded at the time of transmission to the original data. At this time, the auxiliary data included in the packet received by the reception
To supply. The compression ratio detection circuit 37 detects the compression ratio of the received audio data from the data of the data compression ratio arranged in the auxiliary data, and causes the expansion circuit 33 to set the expansion ratio corresponding to the compression ratio.

By controlling the decompression processing in the decompression circuit 33 in this way, even if the compression ratio of the audio data included in the received signal is variable, the decompression circuit 33 can correctly perform the decompression processing, and Digital audio data of the sampling frequency is obtained as an output of the decompression circuit 33.

The reception processing circuit 32 includes a PLL circuit 32a for locking to a clock included in the received data, and uses the clock generated by the PLL circuit 32a to perform processing in the demodulation circuit 32, The processing in the decompression circuit 33 is executed.

The digital audio data output from the expansion circuit 33 is supplied to a first fixed contact 34a of a changeover switch 34. The changeover switch 34 is a switch whose switching is controlled by the control of the control unit 40, and supplies data obtained at the movable contact 34m of the changeover switch 34 to the digital / analog converter 35.

The output of the decompression circuit 33 is supplied to a memory 38
Is also supplied. The memory 38 is a memory that stores the supplied digital audio data for a predetermined period (here, one sampling period) and is used as a delay unit. To the second fixed contact 34b. Therefore, under the control of the changeover switch 34, the digital audio data supplied to the digital / analog converter 35 can be switched between the data currently being received in the sampling period and the data one sampling period before.

The control unit 40 controls the switching of the changeover switch 34 by judging the detection state of the empty packet detection circuit 39 and the like. In a normal state, the movable contact 34m of the changeover switch 34 is in the first position. It is connected to the fixed contact 34a. The empty packet detection circuit 39 includes a decompression circuit 33.
When the digital audio data output from the decompression circuit 33 is data obtained by processing an empty packet (that is, a packet in which no audio data exists), this is detected. The control processing in the control unit 40 based on the detection of the empty packet detection circuit 39 will be described in detail in the description of the transmission state described later.

The digital / analog converter 35 converts the supplied digital audio data into an analog audio signal, and outputs the converted audio signal from an audio signal output terminal 36. In the digital / analog converter 35, the analog audio signal to be output can be converted to a silent audio signal by performing a mute process in accordance with a command from the control unit 40. The state in which the mute process is executed will be described later. The clock supplied from the clock generation circuit 41 is used for the analog conversion in the digital / analog converter 35. The audio signal output from the output terminal 36 of the receiving device 30 is supplied to, for example, an audio amplifier device to which a speaker is connected, so that the audio is output from the connected speaker. In addition, by connecting an audio recording device to the output terminal 36, the recording device can record an audio signal on a recording medium. If the audio device connected to the receiving device 30 is a device that can directly input digital audio data, the digital audio data that has not been subjected to analog conversion by the digital / analog converter 35 is transmitted to the connected audio device. You may make it supply.

Next, the transmitting apparatus 10 thus configured
A transmission state and a reception state under the control of the control unit in each device when audio data is wirelessly transmitted between the device and the reception device 30 will be described. First, an operation state of the transmission device 10 at the time of transmission will be described with reference to a flowchart of FIG.

The control unit 20 of the transmission device 10 determines the amount of data stored in the buffer memory 15 and controls the transmission state. That is, the control unit 20 sets an appropriate data accumulation range as the data accumulation amount of the buffer memory 15, sets the upper limit of the appropriate range as an overflow threshold, and sets the lower limit of the appropriate range for underflow. There is a threshold. Then, the control unit 20 determines whether the current data storage amount of the buffer memory 15 has exceeded the overflow threshold (step 10).
1).

When it is determined in step 101 that the overflow threshold has been exceeded, the current compression circuit 1
It is determined whether the compression coding rate can be made higher than the compression coding rate of the audio data in step 3 (step 10).
2). If it is determined that the compression ratio can be increased, a command to change the compression ratio in the compression circuit 13 to the set ratio setting circuit 21 is sent (step 10).
3). At this time, for example, if the compression ratio can be changed stepwise, the compression ratio is changed to a compression ratio one step higher than the currently set compression ratio.

If it is determined in step 102 that the currently set compression ratio is the highest and the compression ratio cannot be further increased, the changeover switch 16 is moved from the first fixed contact 16a to the first fixed contact 16a. 2 fixed contacts 16
b, and temporarily stores the empty packet data storage unit 1
9 to transmit the empty packet data stored in the transmission processing circuit 17
To temporarily erase the data stored in the buffer memory 15 (step 104).

If it is determined in step 101 that the amount of data stored in the buffer memory 15 does not exceed the overflow threshold, it is determined whether the amount of data has fallen below the underflow threshold (step 105). . If it is determined that the value is not below the threshold value for underflow, the process returns to step 101 and the amount of data stored in the memory 15 is monitored.

If it is determined in step 105 that the value is below the threshold value for underflow, is it possible to set the compression coding rate lower than the current compression coding rate of the audio data in the compression circuit 13? It is determined whether or not it is (step 106). When it is determined that the compression ratio can be reduced, a command to lower the compression ratio in the compression circuit 13 to the set ratio setting circuit 21 is sent (step 1).
07). At this time, for example, if the compression ratio can be changed in a stepwise manner, the compression ratio is changed to a compression ratio one step lower than the currently set compression ratio.

If it is determined in step 106 that the currently set compression ratio is the lowest compression ratio and the compression ratio cannot be further reduced, the changeover switch 16 is moved from the first fixed contact 16a to the first fixed contact 16a. 2 fixed contacts 16
b, and temporarily stores the empty packet data storage unit 1
9 to transmit the empty packet data stored in the transmission processing circuit 17
To temporarily erase the data stored in the buffer memory 15 (step 108).

Then, steps 103, 104 and 10
When the processes in steps 7 and 108 are executed, the process returns to the determination in step 101, and the determination of the overflow or the underflow of the memory 15 is repeatedly performed.

Next, the operation state of the receiving device 30 at the time of reception will be described with reference to the flowchart of FIG.

The control unit 40 of the receiving device 30
It is determined whether or not the received audio data is continuously supplied in the correct frame number order from the output status of step 3 (step 201). Here, it is determined whether or not the packets are supplied in the order of frame numbers. For example, when no empty packets are transmitted, it is determined that the packets are transmitted correctly in the order of the frame numbers. Judge as not in numerical order. If it is determined in step 201 that there is not a continuous frame number but a frame loss, it is determined whether the loss is a loss of only one sample of audio data (step 202).

When it is determined that only one sample is missing, the control unit 40 switches the movable contact 34m of the changeover switch 34 to the second fixed contact 34b, and the digital / analog converter 35 The data to be supplied is replaced with the data one sample before, which has been delayed by the storage in the memory 38 (step 203). At this time, only one sample is replaced, and during the next sample period, a process of returning the movable contact 34m of the changeover switch 34 to the first fixed contact 34a is performed.

If it is determined in step 202 that the loss is not a loss of only one sample, as long as the loss continues, the digital / analog converter 35 mutes the output audio signal to a silent signal (step 20).
4).

When it is determined in step 201 that the received audio data is continuously supplied in the correct frame number order, if there is an error in the received audio data in error detection processing of the received data or the like. It is determined whether or not it is (step 205). If it is determined that there is no error in the received voice data in this determination, step 201
Return to the judgment.

When it is determined that there is an error in the received voice data, it is determined whether the error is a burst error or a temporary error (step 206). If it is determined in this determination that the error is a temporary error, the process proceeds to step 203, where the control unit 40 switches the movable contact 34m of the changeover switch 34 to the second fixed contact 34b side for one sample period.
The data supplied to the digital / analog converter 35 is replaced with the data one sample before, which is delayed by the storage in the memory 38.

If it is determined in step 206 that the error is a burst error, step 204
Then, as long as the error continues, the digital / analog converter 35 performs a mute process to make the output audio signal a silent signal.

When the processing in steps 203 and 204 is performed, the process returns to the determination in step 201.

By performing the transmission processing and the reception processing in this way, wireless transmission of audio data from the transmission apparatus 10 to the reception apparatus 30 is performed satisfactorily. That is, the audio data is transmitted with the compression ratio changed in accordance with the amount of data stored in the buffer memory 15 included in the transmission device 10.
It is possible to effectively prevent a situation in which the buffer memory 15 overflows or underflows. Even if the sampling rate of the digital audio data to be transmitted is asynchronous with the transmission rate, the audio is continuously output. Data can be transmitted, and sound interruption on the receiving side can be effectively prevented.

In this case, the audio data to be transmitted is provided with auxiliary data indicating the compression ratio in the compression circuit 13, so that the receiving device 30 refers to the auxiliary data to receive the received data. Can be determined, correct decompression processing can be performed based on the compression rate at that time, and good reproduction processing can be performed.

When overflow or underflow of the buffer memory 15 cannot be prevented due to a change in the compression ratio at the time of transmission, empty packet data prepared in advance in the storage unit 19 is temporarily transmitted. On the receiving side, a sound signal in a silent state can be temporarily obtained, and transmission of erroneous sound data is prevented by overflow or underflow of the buffer memory 15,
No abnormal sound is output as the output sound of the audio data received by the receiving device 30. Further, such transmission of empty packet data is performed only temporarily when overflow or underflow of the buffer memory 15 cannot be prevented, so that interruption of transmission of audio data can be minimized. Good transmission conditions are maintained as much as possible.

When the transmission of empty packet data is temporary, the receiving apparatus 30 interpolates the audio data of the sample lost in the transmission of the empty packet with the audio data of the immediately preceding sample. By performing the mute process when the sound is lost, interruption of the sound output is avoided as much as possible, and a good sound output state is maintained.

In the embodiment described so far,
I applied Bluetooth as a wireless network,
It goes without saying that the processing of the present invention can also be applied to wireless transmission using another similar wireless network.
In addition, the asynchronous transmission is also applicable to the case of processing audio data transmitted by wire.

In the above-described embodiment, the data indicating the compression rate of the transmitted audio data is added to the auxiliary data. However, the data other than the data indicating the direct compression rate can determine the compression rate. You may do it. For example, data indicating the data length per unit of audio data may be added to the auxiliary data so that the compression ratio can be determined on the receiving side from the data length.

Further, the position at which the auxiliary data in which the data such as the compression ratio is arranged is not limited to the configuration shown in FIG. Further, data such as the compression ratio and the data length may be arranged and transmitted in all frames, or may be transmitted only when the compression ratio and the data length are changed.

[0062]

According to the audio data transmitting apparatus of the present invention,
The audio compression ratio is variably set in accordance with the transmission state at that time, and the temporary storage amount in the storage means provided in the transmission device can be set within a predetermined range. Therefore, it is possible to effectively avoid a situation in which the audio data transmitted from the transmission device is lost, and the receiving side of the audio data transmitted from the transmission device continuously receives and outputs the audio data. Processing can be performed.

In this case, the audio data transmitted by the transmission means is provided with auxiliary data indicating the compression ratio of the compression means or the data length of the audio data, so that the reception side refers to the auxiliary data. Thus, the compression ratio of the received data can be determined.

Further, the control means deletes the data temporarily stored in the storage means when the overflow or underflow of data storage in the storage means cannot be prevented due to a change in the compression ratio of the compression means. Thus, correction of the transmission timing by erasing the data stored in the storage means is minimized, and a good transmission state is maintained as much as possible.

According to the audio data receiving apparatus of the present invention, even if the compression coding rate of the audio data to be transmitted is variably set, correct expansion is performed based on the instruction of the auxiliary data added to the received audio data. It can be decompressed to the original rate by processing. Therefore, even if the compression ratio is variably processed on the transmission side, the original data can be correctly restored in the receiving device, and the output of the received audio data can be performed well.

In this case, when an error is detected in the audio data decompressed by the decompression means, the control means replaces the error-detected audio data with the immediately preceding audio data, so that a transmission error occurs. At times, it is possible to prevent the data in the error occurrence section from being interpolated by the immediately preceding data, thereby preventing abnormal noise and the like from being output.

Further, when an error is detected in the audio data decompressed by the decompression means, the control means mutes the audio data in which the error has been detected. It is possible to prevent abnormal noise and the like from being output.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a transmission configuration example according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an example of a packet configuration according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration example of transmission data according to an embodiment of the present invention;

FIG. 4 is an explanatory diagram showing a data configuration example of one packet according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating a processing example of transmission data according to the embodiment of the present invention;

FIG. 6 is a flowchart illustrating a processing example of received data according to an embodiment of the present invention;

FIG. 7 is a block diagram illustrating an example of a conventional transmission configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Transmission apparatus, 11 ... Audio signal source, 12 ... Analog / digital converter, 13 ... Compression circuit, 14 ... Header addition circuit, 15 ... Buffer memory, 16 ... Switch, 17 ... Transmission processing circuit, 18 ... Antenna, 19: empty packet data storage unit, 20: control unit, 21: compression ratio setting circuit, 22, 23: clock generation circuit, 30: receiving device, 31: antenna, 32: reception processing circuit, 32a: P
LL circuit, 33 ... expansion circuit, 34 ... changeover switch, 35
... Digital / analog converter, 36 ... Audio signal output terminal, 37 ... Compression rate detection circuit, 38 ... Memory, 39 ... Empty packet detection circuit, 40 ... Control unit, 41 ... Clock generation circuit

Claims (6)

[Claims] 1. A compression unit for compressing and encoding audio data sampled at a predetermined sampling frequency, a storage unit for temporarily storing audio data compressed by the compression unit, and a voice stored in the storage unit. Audio data comprising: transmission means for transmitting data to a predetermined transmission path; and control means for variably setting a compression rate of compression encoding by the compression means based on the amount of audio data stored in the storage means. Transmission device. 2. The audio data transmitting apparatus according to claim 1, wherein auxiliary data indicating a compression ratio of said compression means or a data length of the audio data is added to the audio data transmitted by said transmission means. Audio data transmission device. 3. The audio data transmitting apparatus according to claim 1, wherein the control means is configured to, when a change in a compression ratio of the compression means cannot prevent an overflow or underflow of data storage in the storage means. An audio data transmitting device configured to delete data temporarily stored in a storage unit. 4. Receiving means for receiving compression-encoded audio data, decompression means for decompressing the audio data received by the receiving means from the compression encoding to the original rate, and receiving by the receiving means An audio data receiving apparatus comprising: control means for judging a compression rate of the audio data from auxiliary data added to the audio data, and causing the expansion means to execute expansion processing corresponding to the determined compression rate. 5. The audio data receiving apparatus according to claim 4, wherein, when an error is detected in the audio data decompressed by the decompression means, the control means replaces the detected audio data with the immediately preceding audio data. An audio data receiving device that is to be replaced. 6. The audio data receiving apparatus according to claim 4, wherein the control means, when detecting an error in the audio data expanded by the expansion means, mutes the audio data in which the error is detected. Receiver.