JP4101361B2 - Audio data transmitting / receiving apparatus and audio data transmitting / receiving system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio data transmission / reception device and an audio data transmission / reception system, and more particularly to an audio data transmission / reception device and an audio data transmission / reception system with improved processing when asynchronously transferring audio data.
[0002]
[Prior art]
In recent years, various bus standards for personal computer peripheral devices have been developed as computer interfaces. Examples of such bus standards for personal computer peripheral devices include USB (Universal Serial Bus) and IEEE1394. and so on.
[0003]
By using such a computer interface such as USB or IEEE 1394, the processing speed is increased, and between a host computer (hereinafter referred to as “host”) and a device connected to the host, for example, Real-time transfer of audio data such as digital audio data has become possible.
[0004]
Here, the USB data transfer technology described above will be described. In USB, a plurality of types of data can be mixed in a single physical cable bidirectionally, and the plurality of types of data can be transmitted in real time. Has been made.
[0005]
More specifically, in USB, the data that flows through one physical cable is individually packetized, and the packetized data has a time of 1 mSec (1 millisecond) called a frame. It is divided and transmitted. At this time, as shown in FIG. 1, data indicating a frame number called SOF (Start Of Frame) is sent from the host to the transmission line on the transmission line at the head of each frame. Each packet is time-divided and transmitted from the host to the device or vice versa from the device to the host.
[0006]
That is, as shown in FIG. 1, for example, when digital audio data is transmitted, the amount of data required by the device is transmitted and received by dividing it into packets within a 1 millisecond frame. Has been made.
[0007]
In FIG. 1, for example, packets A and A + 1 are reproduction digital audio data (hereinafter referred to as “audio reproduction data”) transmitted from the host to the device, and packets B and B + 1. Is digital audio data for recording (hereinafter referred to as “audio recording data”) transmitted from the device to the host.
[0008]
Further, when there is another type of data to be transmitted, the remaining time in each frame is secured and transmitted.
[0009]
As described above, USB is a transmission method that allows a plurality of types of information to flow through a single physical cable bidirectionally in a time-sharing manner and can be transmitted and received between a host and a device. In USB, the host transmits SOF data every millisecond in order to synchronize with the connected device.
[0010]
Here, as a method of data transfer, for example, at the time of reproduction of digital audio data, generally, a synchronous transfer in which a device on the receiving side synchronizes with a host clock (SOF in USB) on the transmitting side, and a receiving side Asynchronous transfer in which data processing is performed with a clock generated by each device.
[0011]
For example, in USB, in synchronous transfer, a device synchronizes its own clock with SOF and processes audio reproduction data which is data transmitted from the host. Therefore, according to the synchronous transfer, the amount of data transmitted by the host and the amount of data processed by the device are exactly the same, and therefore it is not necessary to feed back the amount of data processed by the device to the host.
[0012]
However, in asynchronous transfer, there is an error between the SOF which is the clock of the sending host and the clock of the receiving device, so that the sending host requires how much data the receiving device needs. It is necessary to transfer data while always confirming whether or not there is feedback from the device on the receiving side.
[0013]
That is, in the asynchronous transfer, as described above, the device clock does not synchronize with the SOF transmitted by the host, so an error occurs in both clocks. The amount of data transferred from the host and the data processing in the device The amount will not match.
[0014]
In USB, in order to correct the discrepancy between the amount of data transferred from the host and the amount of data processed by the device, the device may change its own between one SOF transmitted from the host and the next SOF. The number of clocks counted is counted, and as shown in FIG. 2, the clock count value as the counting result is returned to the host as feedback. The host adjusts the amount of data to be transmitted from the returned clock count value, thereby synchronizing the host and the device.
[0015]
That is, in USB, data (clock count value) fed back from the device to the host is a packet of data representing the number of sample clocks of the device counted between one SOF and the next SOF. Then, the mechanism for transmitting the audio reproduction data in the host repeatedly performs the process of transmitting the amount of data equal to the fed back clock count for each frame.
[0016]
If the data amount is adjusted as described above to synchronize, the host is synchronized with the clock on the device side as a result.
[0017]
By the way, in the above asynchronous transfer process, in a device that transfers the same kind of data in both directions between the host and the device, for example, an audio recording / playback apparatus, as shown in FIG. There is a problem that a route for transferring the audio recording data to the side becomes necessary, and the processing in the host and the device becomes complicated.
[0018]
In USB, physically, SOF, digital audio data (audio reproduction data and audio recording data), and clock count data all flow through the same cable. The “route” means a logical thing regarding USB. However, even in the communication mode in which a cable is physically prepared for each type of data, in the case of asynchronous transfer processing, a cable as a “route” is further required in the same manner as described above. There was a similar problem of increasing complexity.
[0019]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to simplify processing when performing bidirectional audio data communication. An audio data transmitting / receiving apparatus and an audio data transmitting / receiving system are to be provided.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in the asynchronous transfer, regarding the amount of data transmitted from the device to the host, the device processes the data with its own clock and transmits the data corresponding to the processed amount. In order to request the host to do so, the amount of data is determined based on a value calculated from the number of clocks counted between a certain SOF and the next SOF, and the host transmits data to be transmitted in reverse from the data amount. This is based on the idea that the clock count value transfer path can be omitted as shown in FIG.
[0025]
That is, the invention of claim 1 of the present invention is an invention relating to the host, in the voice data transmitting and receiving apparatus for transmitting and receiving an external device and the audio data through the communication path, the first audio data from the external device through a communication path Receiving means, sample counting means for counting the number of samples of the first audio data received by the receiving means within a predetermined time, and storage means for storing the second audio data to be transmitted to the external device The second audio data stored in the storage means is read out from the storage means, and the second number of samples corresponding to the number of samples of the first audio data within the predetermined time counted by the sample counting means. Transmitting means for transmitting audio data to the external device through the communication path every predetermined time.
[0026]
Here, the billing according to the invention described in claim 1 "voice data transmitting and receiving device" corresponds to "host 10" in the embodiment described later, "external device" in the invention described in claim 1 will be described later It corresponds to “device 100” in the embodiment, and “first audio data” in the invention described in claim 1 corresponds to “audio recording data” in an embodiment described later, and described in claim 1. The “second audio data” in the present invention corresponds to “audio reproduction data” in an embodiment described later.
[0027]
The invention of claim 2 is the invention according to claim 1 of the present invention further includes a synchronization data generating means for generating the synchronous data with a predetermined period, through the communication channel The synchronization data generated by the synchronization data generation means is transmitted to the external device, and the predetermined time for which the sample counting means counts the number of sample signals is the next after a certain synchronization data is generated. This is the time until the synchronization data is generated.
[0028]
Here, the “synchronization data” in the second aspect of the invention corresponds to “SOF” in an embodiment described later.
[0029]
The invention according to claim 3 of the present invention relates to an audio data transmission / reception system including a host and a device, and includes a first audio data transmission / reception device and a second audio data transmission / reception device through a communication path. Audio data transmission / reception system for transmitting / receiving audio data between the first audio data transmission / reception apparatus and the second audio data transmission / reception apparatus connected by a communication path, wherein the first audio data transmission / reception apparatus comprises: First storage means for storing the first sound data, and first reception for receiving the first sound data from the second sound data transmitting / receiving apparatus through the communication path and writing to the first storage means. Means, clock generating means for periodically generating a clock signal, and first audio data received by the first receiving means by the clock generating means. Output means for outputting in response to the generated clock signal, clock counting means for counting the number of clock signals generated by the clock generating means within a first predetermined time, and the second audio data transmitting / receiving apparatus Second storage means for storing second sound data to be transmitted, and second sound data stored in the second storage means are read from the second storage means and counted by the clock counting means. A first audio data having a number of samples corresponding to the number of clock signals within the first predetermined time is transmitted to the second audio data transmitting / receiving apparatus through the communication path every first predetermined time. The second voice data transmitting / receiving device receives the second voice data from the first voice data transmitting / receiving device through the communication path. Sample counting means for counting the number of samples of the second audio data received by the second receiving means within the second predetermined time, and first audio data to be transmitted to the first audio data transmitting / receiving device A third storage means for storing the first sound data stored in the third storage means and reading the first sound data from the third storage means within the second predetermined time counted by the sample counting means Second transmission means for transmitting the first audio data of the number of samples corresponding to the number of samples of the second audio data to the first audio data transmitting / receiving apparatus through the communication path every second predetermined time. It is made to have.
[0030]
Here, "the first voice data transmitting and receiving apparatus" in the invention described in claim 3 corresponds to the "device 100" in the embodiment described later, "a second voice in the invention described in claim 3 The “data transmission / reception device” corresponds to “host 10” in the embodiment described later, and the “first audio data” in the invention described in claim 3 corresponds to “audio reproduction data” in the embodiment described later. The “second audio data” in the invention described in claim 3 corresponds to “audio recording data” in an embodiment described later.
[0031]
According to a fourth aspect of the present invention, in the third aspect of the present invention, the second audio data transmitting / receiving device further generates synchronization data at a predetermined cycle. And a first counting unit configured to transmit the synchronization data generated by the synchronization data generation unit to the first audio data transmitting / receiving device through the communication path, and the sample counting unit counts the number of sample signals. The predetermined time 2 is a time from when certain synchronization data is generated until the next synchronization data is generated, and the first audio data transmitting / receiving apparatus further includes the second audio data through the communication path. When the synchronization data transmitted from the transmission / reception device is received and the clock counting means counts the number of clock signals, is the first predetermined time received? In which the next synchronization data is to the time until it is received.
[0032]
Here, the “synchronization data” in the invention described in claim 4 corresponds to “SOF” in an embodiment described later.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of an audio data transmitting / receiving apparatus and an audio data transmitting / receiving system according to the present invention will be described in detail with reference to the accompanying drawings.
[0034]
FIG. 4 is a block diagram of an audio data transmission / reception system according to the present invention. In the audio data transmission / reception system shown in FIG. 4, an audio data transmission / reception apparatus (hereinafter referred to as “host”) as a host. ) 10 and an audio data transmitting / receiving apparatus (hereinafter referred to as “device”) 100 as a device are connected by USB, and audio reproduction data is transmitted from the host 10 to the device 100 and the device 100 reproduces the audio. In addition, the audio recording data obtained by the input of the device 100 is transmitted to the host 10 and stored in the host 10.
[0035]
FIG. 5 is a detailed block diagram of the host 10. The host 10 transmits audio reproduction data to the device 100 to reproduce sound, and receives audio recording data transmitted from the device 100. It is something to remember.
[0036]
The host 10 then includes a USB host controller 12, a timer 14, a recording data buffer 16, a reproduction data buffer 18, a sample number buffer 20, a first sample number counter 22, and a second sample number counter. 24, a USB reception buffer 26, and a USB transmission buffer 28.
[0037]
Here, the timer 14 generates an SOF timing signal every 1 millisecond and supplies it to the USB host controller 12, the first sample number counter 22 and the second sample number counter 24.
[0038]
The recording data buffer 16 stores audio recording data transmitted from the device 100, and the reproduction data buffer 18 stores audio reproduction data to be transmitted to the device 100.
[0039]
Further, the sample number buffer 20 is a FIFO (first-in first-out) buffer that stores the count value of the first sample number counter 22 and causes the second sample number counter 24 to read the stored count value.
[0040]
The USB reception buffer 26 stores audio recording data transmitted from the device 100, and the USB transmission buffer 28 stores audio reproduction data to be transmitted to the device 100.
[0041]
Here, the USB host controller 12 performs the following processes (1) to (3) based on the SOF timing signal generated by the timer 14.
[0042]
(1) The SOF is transmitted to the device 100.
[0043]
(2) The audio reproduction data stored in the USB transmission buffer 28 is transmitted to the device 100 as a packet.
[0044]
(3) The audio recording data transmitted as a packet from the device 100 through the USB is received and written into the USB reception buffer 26.
[0045]
Next, the first sample number counter 22 performs the following processes (1) and (2) based on the SOF timing signal generated by the timer 14.
[0046]
(1) Count the number of samples of the audio recording data written in the USB reception buffer 26 and store the count value in the sample number buffer 20.
[0047]
(2) The audio recording data written in the USB reception buffer 26 is transferred to the recording data buffer 16.
[0048]
Further, the second sample number counter 24 performs the following processes (1) to (2) based on the SOF timing signal generated by the timer 14.
[0049]
(1) The count value is read from the sample number buffer 20.
[0050]
(2) The audio reproduction data for the number of samples represented by the count value is transferred from the reproduction data buffer 18 to the USB transmission buffer 28.
[0051]
Next, the device 100 will be described with reference to a detailed block diagram of the device 100 shown in FIG. 6. The device 100 receives and reproduces audio reproduction data transmitted from the host 10, and The input audio signal is transmitted to the host 10 as audio recording data.
[0052]
The device 100 includes a clock counter 102, a clock oscillator 104, a DSP (digital signal processor) 106, a digital / analog converter (D / A) 108, and an analog / digital converter (A / D). ) 110, digital audio buffer 112, USB transmission / reception logic 114, audio output terminal 116, and audio input terminal 118.
[0053]
Here, the clock counter 102 is supplied with a clock from the clock oscillator 104 and is supplied with an SOF reception signal indicating that the SOF has been received from the USB transmission / reception logic 114 (note that details of the operation of the USB transmission / reception logic 114 are described). The number of clocks generated between one SOF and the next SOF is counted based on the supplied clock and the SOF reception signal. When the clock counter 102 receives the SOF reception signal, the clock counter 102 has a memory (not shown) so that the USB transmission / reception logic 114 can read the counted number of clocks (hereinafter referred to as “clock count value”). And reset the current clock count value.
[0054]
Next, the clock oscillator 104 supplies a clock to the clock counter 102, the DSP 106, and the D / A 108 described above.
[0055]
The DSP 106 is driven by the clock supplied from the clock oscillator 104, performs signal processing on the audio reproduction data received by the USB transmission / reception logic 114 and stored in the reception buffer of the digital audio buffer 112, and outputs the signal. The processed data is output to the D / A 108. On the other hand, the DSP 106 performs signal processing on the audio recording data supplied from the A / D 110 and writes the data after the signal processing in the transmission buffer of the digital audio buffer 112.
[0056]
Further, the D / A 108 is driven by the clock supplied from the clock oscillator 104, inputs the audio reproduction data that has been subjected to the signal processing by the DSP 106 as described above, converts the audio reproduction data into an analog signal, and outputs the audio signal. The signal is output from the output terminal 116 to the outside.
[0057]
On the other hand, the A / D 110 converts an analog audio signal that has been manually input from the outside through the audio input terminal 118 into a digital signal, and outputs the digital signal to the DSP 106 as audio recording data.
[0058]
The digital audio buffer 112 temporarily stores audio playback data received by the USB transmission / reception logic 114 and audio recording data subjected to signal processing by the DSP 106. And a transmission buffer.
[0059]
The USB transmission / reception logic 114 performs the following processes (1) to (4) every time an SOF is received, that is, every frame.
[0060]
(1) When an SOF transmitted from the host 10 is received through the USB, an SOF reception signal is transmitted to inform the clock counter 102 that the SOF has been received.
[0061]
(2) Read the clock count value from the clock counter 102.
[0062]
(3) The audio reproduction data transmitted as a packet from the host 10 through the USB is received and written into the reception buffer of the digital audio buffer 112.
[0063]
(4) The number of samples of audio recording data to be transmitted in one frame is calculated from the clock count value read in (2) above, and the audio recording data for the calculated number of samples is accurately digital audio buffer 112. Are sent out from the transmission buffer and sent to the host 10 as packets.
[0064]
Therefore, the audio data transmission / reception system described above is extremely effective when the same type of data is always transferred between the host 10 and the device 100 and the data transfer amount is synchronized with the device 100 side.
[0065]
That is, according to the audio data transmission / reception system described above, by calculating the required number of samples from the number of packet data (audio recording data) received on the host 10 side, packet transmission for sample number feedback can be eliminated. By omitting the packet handling process, the processing load on the transmission system and the host 10 can be significantly reduced.
[0066]
Further, in this audio data transmission / reception system, when only reproducing the audio reproduction data, the device is switched appropriately to use the packet from the device 100 side for transmission of the number of samples, so that the device can be used even when the recording operation is not performed. The required number of samples can be efficiently fed back.
[0067]
That is, in this audio data transmission / reception system, when recording and playback are simultaneously performed, the packet sent from the device 100 to the host 10 only needs to be the recording data itself, so that the processing load on the transmission system and the host 10 is remarkably high. In the case of reproduction only, a packet of the necessary number of samples may be transmitted.
[0068]
【The invention's effect】
Since the present invention is configured as described above, the present invention has an excellent effect that simplification of processing when bidirectional audio data communication is performed can be achieved.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing data on a transmission line in USB.
FIG. 2 is a block diagram showing a case where audio reproduction data is transferred by asynchronous transfer in USB.
FIG. 3 is a block configuration diagram showing a case where audio reproduction data and audio recording data are transferred by asynchronous transfer in USB.
FIG. 4 is a block diagram showing an audio data transmission / reception system according to the present invention.
FIG. 5 is a block diagram showing the configuration of the host side of the audio data transmitting / receiving apparatus according to the present invention.
FIG. 6 is a block diagram showing a device-side configuration of the audio data transmitting / receiving apparatus according to the present invention.
[Explanation of symbols]
10 Host 12 USB Host Controller 14 Timer 16 Recording Data Buffer 18 Playback Data Buffer 20 Sample Number Buffer 22 First Sample Number Counter 24 Second Sample Number Counter 26 USB Receive Buffer 28 USB Transmit Buffer 100 Device 102 Clock Counter 104 Clock oscillator 106 DSP (digital signal processor)
108 Digital / analog converter (D / A)
110 Analog / Digital Converter (A / D)
112 Digital audio buffer 114 USB transmission / reception logic 116 Audio output terminal 118 Audio input terminal

Claims (4)

In an audio data transmitting / receiving device that transmits and receives audio data to and from an external device through a communication path,
Receiving means for receiving first audio data from an external device through a communication path;
Sample counting means for counting the number of samples of the first audio data received by the receiving means within a predetermined time;
Storage means for storing second audio data to be transmitted to the external device;
Second audio data stored in the storage means is read from the storage means, and the second audio data having the number of samples corresponding to the number of samples of the first audio data within the predetermined time counted by the sample counting means. A voice data transmitting / receiving apparatus comprising: a transmitting unit configured to transmit data to the external device through the communication path every predetermined time. The voice data transmitting / receiving apparatus according to claim 1 further includes:
Having synchronization data generating means for generating synchronization data in a predetermined cycle, and transmitting the synchronization data generated by the synchronization data generating means to the external device through the communication path;
The predetermined time during which the sample counting means counts the number of sample signals is a time from when certain synchronization data is generated until the next synchronization data is generated. In an audio data transmission / reception system for transmitting / receiving audio data between a first audio data transmission / reception device and a second audio data transmission / reception device through a communication path,
A first audio data transmission / reception device and a second audio data transmission / reception device connected by a communication path;
The first audio data transmitting / receiving device includes:
First storage means for storing first audio data;
First receiving means for receiving first voice data from the second voice data transmitting / receiving device through the communication path and writing the first voice data in the first storage means;
Clock generation means for periodically generating a clock signal;
Output means for outputting the first audio data received by the first receiving means in accordance with a clock signal generated by the clock generating means;
Clock counting means for counting the number of clock signals generated by the clock generating means within a first predetermined time;
Second storage means for storing second audio data to be transmitted to the second audio data transmitting / receiving device;
The second audio data stored in the second storage means is read from the second storage means, and the number of samples corresponding to the number of clock signals within the first predetermined time counted by the clock counting means First transmission means for transmitting the second audio data to the second audio data transmitting / receiving device through the communication path at the first predetermined time,
The second audio data transmission / reception device includes:
Second receiving means for receiving second audio data from the first audio data transmitting / receiving device through the communication path;
Sample counting means for counting the number of samples of the second audio data received by the second receiving means within a second predetermined time;
Third storage means for storing first audio data to be transmitted to the first audio data transmitting / receiving device;
The first audio data stored in the third storage means is read from the third storage means, and the number of samples of the second audio data within the second predetermined time counted by the sample counting means is obtained. And a second transmission means for transmitting the first audio data of the corresponding number of samples to the first audio data transmitter / receiver through the communication path every second predetermined time. . The voice data transmission / reception system according to claim 3 ,
The second audio data transmitting / receiving device further includes:
Synchronization data generating means for generating synchronization data at a predetermined period, and transmitting the synchronization data generated by the synchronization data generating means to the first audio data transmitting / receiving device through the communication path; The second predetermined time in which the number of sample signals is counted is a time from when a certain synchronization data is generated until the next synchronization data is generated,
The first audio data transmitting / receiving device further includes:
The synchronization data transmitted from the second audio data transmitter / receiver through the communication path is received, and the first predetermined time for the clock counting means to count the number of clock signals is after a certain synchronization data is received. Audio data transmission / reception system that is the time until the next synchronization data is received.

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