JP2002217852A - Method and device for transmitting data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently conduct radio-transmission of a sub-code attached to audio data. SOLUTION: The method includes the steps where frame-structured digital audio data are arranged in the first position of the payload section of a first packet for radio-transmitting it with a radio network of a prescribed format; the sub-code attached to the digital audio data is arranged in the second position of the payload section of the first packet; and data on the arrangement of the sub-code are added to the header section of the first packet and the first packet is radio-transmitted with the radio network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method and a data transmission apparatus suitable for transmitting audio data according to a wireless transmission standard called Bluetooth, for example.

[0002]

2. Description of the Related Art In recent years, it has been proposed to establish a wireless network (wireless network) using a wireless transmission system of a standard called Bluetooth, and it is being put to practical use. This wireless network transmits voice data for telephone communication, image data for facsimile, data for computers, etc. between multiple devices.
The wireless transmission is performed using the 2.4 GHz frequency band. The wireless transmission distance between the devices ranges from several meters to 100 at the maximum.
A relatively short distance network up to about m is assumed. For each type of data to be transmitted, a profile is defined which defines how the data is transmitted.

[0003] Details of the Bluetooth communication system are disclosed by the Bluetooth SIG, a standardization organization that has established standards.

Here, studies have been made to make it possible to transmit digital audio data using a Bluetooth standard wireless network. That is, various methods for compressing and encoding data at a fixed sampling rate and compressing the data amount to about a fraction of a number have been put into practical use for digital audio data. In addition, transmission can be easily performed in real time even at a transmission rate of the Bluetooth standard.

[0005]

By the way, on a recording medium for recording digital audio data, some subcodes are simultaneously recorded. That is, for example, an optical disk called a compact disk (CD),
A sub-code is added to audio data on a magneto-optical disk or an optical disk called a mini-disc (MD) so that the sub-code can be recorded. In addition to information directly used when reproducing recorded music, such as information on recording time, information on the number of channels, and the like, information for display, such as music title information and text information, may be recorded.

[0006] Here, in the case where audio data and subcode data reproduced from, for example, a compact disc or mini disc are considered to be wirelessly transmitted according to the conventionally proposed Bluetooth standard, audio data is transmitted to a certain radio. It is necessary to perform a process of transmitting a subcode to a partner device using a transmission channel using a wireless transmission channel different from a wireless transmission channel for audio data while transmitting the subcode to a partner device. . As described above, if the audio data and the subcode are wirelessly transmitted by different processes, the transmission process and the reception process of the wireless signal are performed twice, and there is a problem that transmission efficiency is poor.

[0007] In view of the above, it is an object of the present invention to efficiently transmit a subcode attached to audio data by radio.

[0008]

According to the present invention, frame-structured digital audio data is arranged at a first position of a payload section of a first packet for wireless transmission over a wireless network of a predetermined format. , The sub code added to the digital audio data
Is arranged at a second position of the payload section of the first packet, data relating to the arrangement of the subcode is added to the header section of the first packet, and processing for wirelessly transmitting the first packet through the wireless network is performed. It was made.

[0009] By doing so, the digital audio data and the subcode are arranged in one packet and transmitted wirelessly.

[0010]

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

[0011] In the present invention, Bluetooth (Blue
This is a wireless transmission method called tooth), which is applied to a wireless communication system in which a wireless network is established between two or three or more devices. First, the wireless transmission system of the Bluetooth standard will be described.

FIG. 1 is a diagram showing the configuration of a wireless transmission apparatus in which transmission / reception processing is performed according to the wireless transmission method. Transmission / reception processing unit 2 in wireless processing unit 10 to which antenna 1 is connected
In the above, a radio transmission process and a radio reception process are performed by performing a high-frequency signal process. The signal transmitted and received by the transmission / reception processing unit 2 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.

The signal received by the transmission / reception processing unit 2 and the signal to be transmitted by the transmission / reception processing unit 2 are transmitted to the data processing unit 3
Performs the baseband processing. In the Bluetooth standard, TDD (Time Div.) That basically performs transmission and reception alternately
The data processing unit 3 alternately performs processing of a transmission slot and processing of a reception slot. That is, as shown in FIG. 4, for example, when one device performing wireless transmission is set as a master and the other device is set as a slave, data of a slot configuration is transmitted from the master to the slave during one slot (625 μsec). Then, during the next one slot period, data of a slot configuration is transmitted from the slave to the master (B in FIG. 4). 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. In the Bluetooth standard, continuous use of a plurality of slots is possible depending on the transmission rate at that time.

Returning to the description of FIG. 1, the data processing unit 3 has a function processing block 2 via an interface unit 4.
0 is connected and the received data is transferred to the function processing block 2
0 or the data sent from the function processing block 20 is processed by the data processing unit 3 as a transmission slot. Processing for transmission in the transmission / reception processing unit 2, the data processing unit 3, and the interface unit 4 is executed under the control of the controller 5.

The function processing block 20 corresponds to a part that actually executes a function as a device. For example, when the device that performs the wireless communication is an audio recording / reproducing device,
It corresponds to a part for processing recording and reproduction of audio data.

Next, an example of a device having the built-in radio processing unit 10 shown in FIG. 1 will be described. FIG. 2 shows an example in which an audio recording / reproducing device is used as a device in which the wireless processing unit 10 is built. The audio recording / reproducing apparatus 100 of this example records and reproduces audio signals and the like as digital data by using a magneto-optical disk or an optical disk called a mini disk (MD) stored in a resin package as a recording medium. Device.

As a configuration of a recording system of the audio recording / reproducing apparatus 100, an analog two-channel audio signal input from the outside is converted into digital audio data by an analog / digital converter 101. The converted digital audio data is supplied to the ATRAC encoder 102,
Encode into audio data compressed by the AC (Adaptive Transform Acoustic Coding) method. When digital audio data is directly input from the outside, the input audio data is directly supplied to the ATRAC encoder 102 without passing through the analog / digital converter 101. The data encoded by the encoder 102 is supplied to a recording / reproducing unit 103 to perform a recording process, and an optical pickup 104 is driven based on the processed data, and the data is written to a disk (magneto-optical disk) 105. Record.
At the time of recording, magnetic field modulation is performed by a magnetic head (not shown).

As a configuration of a reproducing system of the disk recording / reproducing apparatus 100, data recorded on a disk (magneto-optical disk or optical disk) 105 is read by an optical pickup 104.
To read out, and perform a reproducing process in the recording / reproducing unit 103,
The audio data compressed by the RAC method is obtained. The reproduced audio data is supplied to an ATRAC decoder 106, where the reproduced audio data is decoded into digital audio data of a predetermined format, and the decoded audio data is converted into a digital / analog converter 10
7, and is converted into a two-channel analog audio signal and output. When digital audio data is directly output to the outside, the audio data decoded by the ATRAC decoder 106 is directly output without passing through the digital / analog converter 107.

The audio recording / reproducing apparatus 100 of the present embodiment
Is provided with a wireless processing unit 10 for performing wireless communication according to the Bluetooth method described above, and performs bidirectional wireless communication with a wireless processing unit on the other side via the connected antenna 1. For example, the audio data received by the wireless processing unit 10 is supplied to the recording / reproducing unit 102 via the ATRAC encoder 102, and can be recorded on the disk 105. Also, the disk 105
The audio data reproduced from the
The data is supplied to the wireless processing unit 10 via the RAC decoder 106, and can be wirelessly transmitted to a device on the other side.

The recording and reproduction processing in the audio device 100 and the transmission and reception processing in the wireless processing block 10 are executed under the control of a central control unit (CPU) 110. A memory 111 serving as a work RAM is connected to the CPU 110. The operation panel 11
2 is supplied to the CPU 110 to perform operation control corresponding to the operation information.

The processing of the subcode recorded on the disk 105 and the processing of the subcode reproduced from the disk 105 are also performed by the central control unit 110. In this case, for example, the sub-code reproduced from the disc together with the reproduced audio data is transmitted to the radio processing unit 10.
When it is necessary to transmit the data by wireless, the necessary data in the reproduced subcode is supplied to the wireless processing unit 10 so that the signal transmitted wirelessly includes the subcode.

FIG. 3 shows this disk recording / reproducing apparatus 100.
FIG. 2 is a diagram illustrating an example of an audio amplifier device 200 as an example of a device that performs wireless communication with the apparatus. The audio amplifier device 200 includes a wireless processing unit 10 'for performing wireless communication in a Bluetooth system, and performs bidirectional wireless communication with a wireless processing unit on the other side via a connected antenna 1'. It is. If the data received by the wireless processing unit 10 ′ is audio data as stream data, the data is supplied to the ATRAC decoder 201. When the data received by the wireless processing unit 10 'is data such as a control command, the audio amplifier device 20'
Central control unit (CPU) 210 that controls the operation of
To supply. Further, data such as a subcode attached to the audio data is also supplied to the central control unit 210.

When audio data is received as stream data by the radio processing unit 10 ′, the audio data is decoded by the ATRAC decoder 201 from the ATRAC system, and the decoded digital audio data is supplied to the selection circuit 202. The selection circuit 202 is a circuit for selecting input audio data under the control of the central control unit 210, and selects desired audio data from digital audio data input to the amplifier device 200 based on a user operation or the like. .

The audio data selected by the selection circuit 202 is supplied to a digital / analog converter 203 to be converted into left and right two-channel analog audio signals, and the converted audio signals of the respective channels are amplified by an amplification circuit 204. ,
At 205, the signal is amplified for driving a speaker, and the amplified audio signal of each channel is supplied to a speaker device (not shown) for each channel connected to the audio amplifier device 200. Processing states such as amplification factors in the amplification circuits 204 and 205 are controlled by the central control unit 210.

A RAM 211 as a work memory is connected to the central control unit 210. The operation status and the like are displayed on the display unit 212 under the control of the central control unit 210, and the operation information of the operation buttons 213 arranged on the amplifier device 200 is supplied to the central control unit 210. It is. The display unit 212 can display the number of tracks, performance time, song title, lyrics, and the like based on, for example, a subcode attached to the received audio data.

Next, the audio recording / reproducing apparatus 10 of this embodiment
The wireless transmission process between the audio amplifier 200 and the audio amplifier 200 will be described. Here, it is assumed that, for example, audio data reproduced from a disc by the audio recording / reproducing device 100 is wirelessly transmitted and received by the audio amplifier device 200.

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

As shown in FIG. 5B, the access code is composed of a 4-bit preamble and a 64-bit sync word, and no data is arranged in the remaining section. As shown in FIG. 5C, the header includes an address (AM ADR) for each device, a type indicating the type of payload, and bits (FLOW,
ARQN, SEQN) and an error check bit (HEC).

Here, in the present embodiment, compression-encoded audio data, which is stream data, and a subcode added to the audio data are transmitted using a common packet. .

FIG. 6 is a diagram showing an example of a transmission processing state of audio data in the present embodiment. In the case of this example, audio data (audio data) of two channels of a left channel (Lch) and a right channel (Rch) is transmitted. For example, an audio signal of the left channel shown in FIG. And the right channel audio signal shown in FIG. 6 is individually digitized, and as shown in FIG. 6C, one sample data of each channel to which a subcode is added is defined as one subframe, and one frame is composed of two left and right channels. Data. The frame configuration shown in FIG. 6C is a configuration specified by IEC60958, which is one of the audio data transmission formats.

The subcode is, for example, 2 per sample.
In terms of bits, 512 samples × 2 bits, 1024 bits in one subframe, and 2048 bits in one frame including two channels. In the case of 3 bits per sample, 3072 bits per frame. As for the data of this subcode, basically, the process of compressing the data amount is not performed, and the number of bits is transmitted as it is.

FIG. 7 shows an example of the format of a subframe. In this example, a synchronization preamble and AUX data are arranged at the beginning of one subframe, and audio data is arranged subsequently. The audio data is composed of two's complement data. Subcodes are arranged following the audio data. Here, as sub codes, a V bit (validity flag), a U bit (user data), and a C bit (channel status)
And P bits (parity bits) are arranged in a predetermined number of bits. As the synchronization preamble, three types of M pattern, W pattern, and B pattern are prepared as described later.

By arranging the sub-frames thus configured in two channels, a frame structure is formed as shown in FIG. Here, 192 frames from frame 0 to frame 191 constitute one unit block. For the synchronization preamble, an M pattern is used for the synchronization preamble in channel 1 which is the left channel, and W is used for synchronization preamble in channel 1 which is the right channel for channel identification of the frame.
The pattern is used. However, the B pattern is used for the synchronization preamble in the first channel 1 of the 192 frame for the block synchronization identification.

Returning to the description of FIG. 6, in the case of the present example, the audio data portion of the digital audio data having the frame structure is compression-coded. Here, it is assumed that audio data of two channels is compression-encoded by the ATRAC method. In the case of ATRAC system,
The audio data of 512 samples for about 11.6 ms is compression-encoded into one unit of data. This one unit of data is prepared for two channels, left and right. Then, a predetermined bit of the sub-code added to the audio data of each sub-frame is added to the compression-encoded audio data. Specifically, a sub-code of several bits (for example, 2 bits or 3 bits) per sample is extracted.

If the extracted subcode is, for example, 2 bits per sample, it is 512 samples × 2 bits, and 1024 units per ATRAC system (one frame).
There are bits, 204 in one frame for two channels
8 bits. In the case of 3 bits per sample, 3072 bits per frame. As for the data of this subcode, basically, the process of compressing the data amount is not performed, and the number of bits is transmitted as it is.

In this example, the audio data that has been compression-encoded and from which the sub-code has been extracted are arranged in an L2CAP packet defined by the Bluetooth standard. The L2CAP packet is a packet defined by L2CAP, which is a data link layer communication procedure for controlling data transmission such as division / assembly of data transmitted according to the Bluetooth standard and flow control.

As shown in FIG. 6D, for example, as shown in FIG.
Following the header of the 2CAP packet, the left channel compressed audio data and the right channel compressed audio data are arranged for one frame. Also, one L2
Ancillary data at the end of the CAP packet
, The left channel subcode and the right channel subcode are continuously arranged.

As shown in FIG. 6D, L
When a 2CAP packet is configured, a 1-bit identification code indicating that the data in the auxiliary data section is valid is set in a predetermined section d1 of the header of the packet.
Also, data indicating the data length of the compressed audio data is arranged in another section d2 of the header, and data indicating the data length of the auxiliary data section is arranged in another section d3 of the header.

The L2CAP packet thus configured is transmitted to the baseband processing unit in the radio processing unit 10 in a payload section of a packet for generating a transmission slot in units of 625 μsec as shown in FIG. Divide and place. At this time, all data of the header, audio data, and auxiliary data constituting the L2CAP packet are arranged in the payload section in order from the top. When a vacancy occurs in the last packet, the head of the next L2CAP packet is arranged. The baseband packet generated in this manner is transmitted, and the audio recording / reproducing apparatus 100 wirelessly transmits data having a slot configuration in units of 625 μsec, as already described with reference to FIG.

On the side receiving the data (audio amplifier device 200), the payload section of the baseband packet obtained by the reception processing is extracted, and the L2CA
The P packet is restored, and the compressed audio data arranged in the data section of the restored L2CAP packet is
The data is decoded by the ATRAC decoder 201, and the decoded audio data of the left and right two channels is converted into an analog signal, amplified, supplied to a connected speaker device, and emitted. At this time, the subcode arranged in the auxiliary data section of the L2CAP packet is supplied to the central control unit 210 of the audio amplifier device 200 to execute processing such as display based on the subcode. For example, when information such as a track number (song number), performance time (reproduction time), and song name is obtained as a subcode, the information is displayed on the display unit 212.

In this way, since the audio data is compressed and encoded and transmitted to the other device, the audio data can be transmitted efficiently with a small amount of data. Then, by transmitting the subcode using the compressed data and the auxiliary data section in the common packet frame, a packet is generated only for transmitting the subcode and transmitted separately from the audio data. The processing configuration on both the transmitting side and the receiving side is simplified as compared with the case where processing is performed. Further, the transmission band required for wireless transmission is reduced, and the transmission efficiency is improved accordingly.

In this case, since the data having the data length of the audio data and the data having the data length of the auxiliary data are arranged in the header section of the data to be transmitted, the receiving side refers to this data in the header section. Thus, audio data and auxiliary data can be reliably separated and extracted, and transmission errors can be prevented.

When the sub-codes are transmitted by radio, it is not necessary to transmit all the sub-codes reproduced from the disc, and only the necessary sub-codes need to be transmitted on the receiving side. For example, only the subcode directly related to the display may be transmitted.

The packet configuration described in the above embodiment is an example, and other packet configurations may be used. For example, the L2CA shown in FIG.
In the P packet, compressed audio data is arranged in a section following the header, and auxiliary data is arranged after that. However, auxiliary data is arranged after the header section, and compressed audio data is arranged after that. May be.

In the above-described embodiment, the present invention is applied to the case where audio data is wirelessly transmitted between the disk recording / reproducing device and the amplifier device. However, the present invention can be applied to other devices which wirelessly transmit audio data. is there.

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.

[0047]

According to the present invention, digital audio data and sub-codes are arranged in one packet and transmitted wirelessly, and digital audio data with the sub-code is transmitted using a limited transmission band. Wireless transmission can be performed efficiently.

In this case, the data relating to the data length of the subcode is arranged in the header section of the packet,
The side receiving the wirelessly transmitted signal can easily determine the position of the subcode from the information in the header section.

Further, in the header section of the packet, the data relating to the data length of the section in which the digital audio data is arranged is further arranged. Can be determined with certainty.

The packets formed in this manner are divided into the payload sections of the packets to be wirelessly transmitted and arranged, and are subjected to the wireless transmission processing, whereby the wireless transmission is favorably performed in a wireless network such as the Bluetooth standard. Will be able to do it.

The digital audio data to be packetized is at least digital audio data obtained by compressing and encoding digital audio data of the first channel and digital audio data of the second channel by a predetermined compression encoding method. Thus, digital audio data of two or more channels can be efficiently transmitted by wireless.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration example of an audio recording and reproducing device according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration example of an audio amplifier device according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a transmission example according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an example of a packet configuration according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of audio data transmission processing according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an example of a subframe format according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an example of a frame and block format according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Transmission / reception processing part, 3 ... Data processing part,
4 Interface unit, 5 Controller, 10 Wireless processing unit, 20 Functional processing block, 100 Audio recording / reproducing device, 110 Central control unit (CP
U), 200: audio amplifier device, 210: central control unit (CPU)

Claims (10)

[Claims] 1. A frame structured digital audio data is arranged at a first position of a payload section of a first packet for wireless transmission over a wireless network of a predetermined format, and is added to the digital audio data. The sub-code is arranged at a second position of a payload section of the first packet, and data relating to the arrangement of the sub-code is added to a header section of the first packet. A data transmission method, wherein the first packet in which is disposed is wirelessly transmitted in the wireless network. 2. The data transmission method according to claim 1, wherein data relating to a data length at the second position where a subcode is disposed is arranged in a header section of the first packet. 3. The data transmission method according to claim 2, wherein a header section of the first packet further includes the first packet.
A data transmission method in which data relating to the data length of a section is arranged. 4. The data transmission method according to claim 1, wherein the first packet is divided and arranged in a payload section of a second packet wirelessly transmitted, and the second packet is wirelessly transmitted. Data transmission method. 5. The data transmission method according to claim 1, wherein the frame-structured digital audio data is obtained by converting at least a first channel digital audio data and a second channel digital audio data into a predetermined compression code. A data transmission method that is digital audio data that has been compression-encoded by an encryption method. 6. The input digital audio data is
The sub-code added to the digital audio data is located at the first position of the payload section of the first packet for wireless transmission in the wireless network of a predetermined format, and is placed in the second position of the payload section of the first packet.
And in the header section of the first packet,
A data transmission device, comprising: packet data generation means for adding data relating to the arrangement of subcodes; and transmission means for wirelessly transmitting the first packet generated by the packet data generation means for the wireless network. 7. The data transmission apparatus according to claim 6, wherein said packet data generating means arranges data relating to a data length of said second position where a subcode is arranged in a header section of said first packet. Data transmission device. 8. The data transmission apparatus according to claim 7, wherein said packet data generating means arranges data relating to a data length of said first section in a header section of said first packet. Transmission equipment. 9. The data transmission apparatus according to claim 6, wherein the transmitting unit divides the first packet into a payload section of a second packet wirelessly transmitted, and
A data transmission device that performs a process of sequentially performing wireless transmission processing of packets at specified timing. 10. The data transmission apparatus according to claim 6, wherein the digital audio data input to the packet data generating means is a digital audio data of at least a first channel and a digital audio data of a second channel. A data transmission device which is digital audio data compression-encoded by the compression-encoding method.