JP2005276226A - Data transfer device and method for controlling it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent data from lacking when transferring digital data, especially AV data, between digital data output equipment and the external device thereof, without placing any special burden on the user. <P>SOLUTION: An intermediate circuit 10 that receives AV data comprising digital data and a control signal for controlling the AV data to transfer the AV data or the decoded AV data includes a USB controller 3 that transfers the AV data, the control signal and the decoded AV data by USB communications and extracts the AV data from the signal received; a memory 5 for accumulating the AV data extracted by the USB controller 3; and a light transmission unit 8 that continuously provides outputs from the memory 5 at constant speed by means of the control signal of the signal received. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data transfer apparatus and a data transfer method used when digital data is transferred between a digital data output device such as a player device including a personal computer (PC) or a mobile phone and an external device, In particular, the present invention relates to a data transfer apparatus and a data transfer method for preventing data loss in AV data transfer.

  Conventionally, when AV data is transferred between a digital data output device such as a PC and an audiovisual device (hereinafter referred to as “AV device”), various interfaces represented by USB (Universal Serial Bus) It is common for digital data to be transferred through the network.

  For example, when transferring AV data by USB communication, the normal isochronous method is adopted. The isochronous method is one of four data transfer methods stipulated in USB communication, and is a data transfer method that guarantees the amount of data transferred within a certain period (hereinafter referred to as “one frame”).

The isochronous system has the following characteristics a. To c.
a. In the isochronous method, since the bandwidth or transfer speed of data transfer is preferentially secured, even when other data transfer is performed simultaneously on the same communication line, the isochronous method is performed by the other data transfer. Data transfer subject to the method is not interrupted.
b. In the isochronous method, even if a transfer error occurs during target data transfer in the isochronous method, retransmission of missing data is not performed.
c. In the isochronous method, the amount of data transferred in one frame is always constant, and data with a different amount of data cannot be transferred each time.

  Since the isochronous system has the characteristics a. To c. Described above, it is suitable for AV data communication in which real-time property of data transfer is more important than prevention of data loss. In playback and duplication of AV data, fluctuations in the playback tempo due to the loss of real-time data transfer are more adversely affected than instantaneous interruptions in moving pictures or music due to data loss. Because it affects.

  In the isochronous method, a certain amount of data is transferred for each frame by transferring one isochronous packet for each frame, for example, every 1 ms. In the isochronous method, it is not determined at which timing in the frame the isochronous packet is transferred, and is performed at any timing in the frame. Therefore, in the AV data transfer between the digital data output device and the AV device, the isochronous packet including the amount of AV data required for reproduction or duplication for one frame, for example, 1 ms is included in the frame. Is supplied at an arbitrary timing.

  In order to transfer AV data, for example, stereo audio data with a sampling frequency of 48 kHz and a resolution of 16 bits, which is generally handled by PCs and player devices, in real time, data transfer of 48 kHz × 16 bits × 2 channels = 1.536 Mbps per second Speed is required. Therefore, in a data transfer apparatus that connects a PC or player device and an external AV device, the clock timing and the like are often set so as to ensure a data transfer rate of 1.536 Mbps.

  As described above, if the clock timing of the digital data output device or data transfer device is set to ensure the required data transfer speed, the AV data can be converted theoretically except for data errors due to unexpected noise. Can be transferred in real time. For example, if the AV data to be transferred is audio data, it should be possible to transfer the audio data at a transfer speed that does not cause sound interruption.

  However, actually, even when the clock timing of the digital data output device or the data transfer device is set so as to ensure the above transfer speed, the transfer data is lost, and the AV device side cuts the frame of the video or music. Often causes sound interruption.

  This is because the output operation of the digital data output device becomes temporarily unstable.

  For example, in a digital data output device, the operation of application software (hereinafter referred to as “application”) that transfers AV data may be hindered by the operation of other applications. That is, an application that transfers AV data by USB communication or the like normally requests various calculation processes and control processes from the CPU of a digital data output device such as a PC, and causes the CPU to execute these processes, thereby Perform the transfer.

  For this reason, when another application requests a new process from the CPU, a limited processing capacity of the CPU is allocated to the process, and the processing capacity to be allocated to the transfer of the AV data is temporarily insufficient. Become. On the operating system of operation software (hereinafter referred to as “OS”), it is difficult to assign the CPU processing capacity in preference to the transfer of the AV data, and transfer is performed when the CPU processing capacity is insufficient as described above. AV data is lost, and the AV device side cuts out the frames of the moving image and cuts off the sound of the music.

  As a simple solution to the above problem, the environment of the digital data output device is set so that no application other than the application that transfers AV data on the digital data output device operates during the transfer of AV data. It is possible to consider

  However, such a method is not realistic. This is because a large number of applications are installed in recent digital data output devices, and in these applications, even if the user does not start intentionally, the operation software is linked to the start of the digital data output device Many applications start automatically. For example, when Windows (registered trademark) is adopted as the OS of the PC, if the application is registered in the startup folder, Windows (registered trademark) automatically starts the application simultaneously with the startup of the PC. There are applications that require processing from the CPU in a so-called background without requiring a special activation instruction by the user or the OS, unlike the power management utility of a notebook PC.

  In addition, when various applications are activated, the processing capacity of the CPU is often consumed more than the user recognizes even if the user does not give a special instruction to the application. The above applications voluntarily perform various processes that the user is not aware of, such as a network connection process that connects the PC to the Internet, etc., and a mail check process that periodically checks the presence of received mail by accessing the server. This is because there are many requests to the CPU.

  As described above, since the operating environment of recent digital data output devices is extremely complicated, it is difficult for novice users to limit and manage processing requests to the CPU by all applications other than applications that transfer AV data. Is difficult, and even for so-called power users, the operability and convenience of the digital data output device are greatly limited.

  The present invention has been made to solve the problems of the conventional methods as described above, and the object of the present invention is to perform digital communication between a digital data output device and its external device without imposing a special burden on the user. An object of the present invention is to provide a data transfer device and a data transfer method for preventing data loss when transferring data, particularly AV data.

  A data transfer apparatus according to the present invention is a data transfer apparatus that receives AV data composed of digital data and a control signal for controlling the AV data, and transfers the AV data or decoded AV data obtained by decoding the AV data. The AV data, the control signal, and the decoded AV data are transferred by USB communication. AV data extracting means for extracting AV data from the received signal, and the AV data extracted by the AV data extracting means AV data accumulating means for accumulating and AV data output means for continuously outputting from the AV data accumulating means at a constant speed by the control signal of the received signal are provided.

  The data transfer device control method according to the present invention is a data transfer method for transferring digital data from a digital data output device to an external device of the digital data output device by USB communication. Extracting temporally continuous AV data from the digital data, storing the extracted AV data, and reading the stored AV data to the external device continuously at a constant speed Output stage.

  According to the above invention, AV data is extracted from the digital data transferred from the digital data output device, and the extracted AV data is temporarily stored and then read and output to the external device.

  Further, according to the above invention, the digital data output device and the data transfer device can be simply connected by USB communication which is widely used as an interface for connecting the digital data output device and the peripheral device, and high-speed data transfer can be performed. Can be done.

  Therefore, by always accumulating AV data above a certain level, even if the digital data transfer from the digital data output device is temporarily interrupted due to insufficient processing capacity of the CPU in the digital data output device, AV data is stably output to the external device.

  As a result, data is lost when AV data is transferred between the digital data output device and the external device without imposing a special burden on the user, and AV data is lost due to such data loss. It is possible to suppress the frame cut-off and the sound cut-out phenomenon of music that occur during playback and duplication.

  According to the present invention, data loss that occurs when AV data is transferred without imposing a special burden on the user, and frames of moving images that are generated when AV data is reproduced or duplicated due to such data loss And the effect of being able to suppress the sound interruption phenomenon of music.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the intermediate circuit (data transfer device) of this embodiment. In the figure, an intermediate circuit 10 is connected to a PC 1 (digital data output device) via a USB cable 2 and further connected to an external audio device 11 (external device) via an optical cable 9. Yes. Inside the intermediate circuit 10, there are a USB controller 3 (AV data extraction means), a memory controller 4 (storage state control means), a memory 5 (AV data storage means), an audio timing generation circuit 6, a digital audio transmitter 7, and an optical transmission. A unit 8 (AV data output means) is provided.

The USB controller 3 is a control circuit that receives digital data transferred from the PC 1 according to the USB data transfer protocol, and extracts audio data (AV data), various timing signals, control signals for external devices, and the like.

  The memory 5 is a semiconductor memory in which digital data can be freely written and read.

  The memory controller 4 is a control circuit that manages writing and reading of the audio data in the memory 5 and controls the audio data storage state of the memory 5.

  The audio timing generation circuit 6 is a circuit that generates a timing signal for normally transferring and reproducing the audio data.

  The digital audio transmitter 7 is a circuit that converts the audio data into an interface signal in synchronization with a timing signal generated by the audio timing generation circuit 6.

  The optical transmission unit 8 is an output circuit that converts an interface signal as an electrical signal generated by the digital audio transmitter 7 into an optical signal and outputs the optical signal to the optical cable 9.

  FIG. 2 is a block diagram showing the internal configuration of the PC 1 shown in FIG. Inside the PC 1, a CD-ROM drive 12, a hard disk drive 13, an audio application 14, and a USB driver 15 are provided.

  The CD-ROM drive 12 and the hard disk drive 13 are recording media for storing in advance the audio data that the PC 1 transfers to the external audio device 11. The audio application 14 is a memory or CPU (CPU ( This is an application for processing, storing, transferring, and the like of the audio data integrated with a hardware configuration such as none (not shown).

  Next, the operations of the PC 1, the intermediate circuit 10, and the audio device 11 will be described with reference to FIGS.

  First, in the PC 1, a communication speed when transferring digital data including the audio data to the intermediate circuit 10 is set to 6 Mbps, for example. Specifically, the following procedure is performed. In FIG. 2, the audio application 14 selects an audio data file to be transferred to the intermediate circuit 10 and the audio device 11 from the plurality of audio data files recorded in the CD-ROM drive 12 and the hard disk drive 13. Read. The audio application 14 performs a predetermined format conversion on the read audio data file together with various timing signals and control signals of external devices so as to conform to the USB data transfer protocol. The digital data obtained in this way includes the audio data, and the audio application 14 transfers the digital data to the USB driver 15 at a transfer rate of 6 Mbps. The USB driver 15 transfers the digital data to the USB controller 3 (see FIG. 1) of the intermediate circuit 10 at the same transfer rate of 6 Mbps according to the USB data transfer protocol.

  In the intermediate circuit 10, the USB controller 3 extracts the time-sequential audio data, various timing signals, external device control signals, and the like from the transferred digital data, and transfers them to the memory controller 4. .

  The fact that the audio data is continuous in time means that the audio data is sound data for performing continuous reproduction or duplication while changing with time.

  The USB controller 3 transfers the extracted audio data to the memory controller 4 together with various timing signals and control signals for external devices.

  The memory controller 4 temporarily stores the audio data in the memory 5 and then synchronizes with the timing signal generated by the audio timing generation circuit 6. For example, the audio data is stereo audio having a sampling frequency of 48 kHz and a resolution of 16 bits. If it is data, the audio data is read from the memory 5 at a speed of 1.536 Mbps, and the audio data is transferred to the digital audio transmitter 7 at the same speed.

  Note that the memory controller 4 constantly monitors the audio data storage state of the memory 5 and controls the storage or deletion of the audio data in the AV data storage means according to the audio data storage state.

  Specifically, the memory controller 4 supplies the audio data so that the memory 5 always accumulates the audio data of a predetermined amount or more, while the supply speed of the audio data is too high, and the memory 5 overflows. Together with the USB controller 3, the transfer rate of the USB communication is controlled. The memory controller 4 sequentially erases the audio data already transferred to the digital audio transmitter 7 from the audio data stored in the memory 5.

  The digital audio transmitter 7 converts the audio data into an interface signal in synchronization with the timing signal generated by the audio timing generation circuit 6, and transfers the interface signal to the optical transmission unit 8 at a speed of 1.536 Mbps. .

  The optical transmission unit 8 converts the interface signal as an electrical signal into an optical signal and outputs the optical signal to the optical cable 9. The optical cable 9 transmits the optical signal to an external audio device 11, and the audio device 11 performs music reproduction and recording (duplication) based on the transmitted optical signal.

  That is, the operations of the PC 1, the intermediate circuit 10, and the audio device 11 are performed temporally from the digital data transferred from the PC 1 in the data transfer method for transferring digital data from the PC 1 to the intermediate circuit 10 and the audio device 11. Extracting the continuous audio data, storing the extracted audio data, and reading the stored audio and outputting it to the audio device 11.

  As described above, in this embodiment, the transfer rate of the digital data from the PC 1 to the intermediate circuit 10 is 6 Mbps, and the transfer rate of the audio data from the intermediate circuit 10 to the audio device 11 is 1.536 Mbps. Therefore, even if it is considered that the digital data includes a control signal other than the audio data, the transfer speed of the audio data included in the digital data transferred between the PC 1 and the intermediate circuit 10 is the intermediate circuit. 10 and several times the transfer speed of audio data between the audio device 11 and the audio device 11.

  Therefore, the data amount of the audio data stored in the memory 5 exceeds the data amount of the audio data read from the memory 5, and a certain amount or more of the audio data is always stored in the memory 5. And can be secured.

  As a result, even if the processing capacity of the CPU is insufficient due to the operation of another application in the PC 1 and the digital data transfer from the PC 1 to the intermediate circuit 10 is temporarily interrupted, the audio data is stored in the memory reliably and stably. 5 to the audio device 11. Therefore, the audio device 11 can reproduce and record the audio data without omission.

  Further, when the digital data transfer from the PC 1 is temporarily interrupted and resumed, the digital data transfer is supplied from the PC 1 to the data transfer device at a high speed, so that the influence of the data transfer interruption from the PC 1 is further reduced. Is possible.

  The time during which the interruption of the digital data transfer is allowed depends on the amount of audio data stored in the memory 5. Simply, the amount of audio data stored in the memory 5 is converted from the intermediate circuit 10 to a unit time. It can be calculated as the time divided by the data amount of the audio data to be output to. That is, as the capacity of the memory 5 is larger and more audio data is accumulated, the allowable time becomes longer.

  In the present embodiment, for example, when the audio data of 8 Mbit is stored in the memory 5, the allowable time is 8Mbit ÷ 1.536Mbps≈5.2 seconds. Usually, the interruption of the transfer of the audio data from the PC 1 is often less than one second, and it is practically sufficient if the interruption of the digital data transfer is allowed for several seconds.

[Embodiment 2]
Further embodiments of the present invention will be described below with reference to the drawings.

  The hardware configuration of the intermediate circuit and the PC according to the present embodiment is the same as that of the intermediate circuit 10 and the PC 1 shown in FIGS.

  FIGS. 3A and 3B are explanatory diagrams showing time charts of communication frames in data communication between the intermediate circuit 10 and the PC 1 of the present embodiment. As shown in FIGS. 2A and 2B, in this embodiment, isochronous USB communication is adopted for audio data transfer in the data communication.

  As described above, according to the isochronous method, a predetermined amount of data transferred per frame is preferentially guaranteed in the USB communication. Thus, even when other data transfer is performed simultaneously on the same USB communication line, the transfer of the audio data subject to the isochronous method is not interrupted by the other data transfer.

  For example, when stereo audio data having a sampling frequency of 48 kHz and a resolution of 16 bits is transferred without interruption, a data transfer rate of 1.536 Mbps is required as described above. That is, the amount of data transferred per 1 ms frame is 1.536 Mbps × 1 ms = 1536 bits = 192 bytes (8 bits = 1 byte conversion). FIG. 3A shows a time chart in the case of performing isochronous USB communication at the above data transfer rate. As shown in the time chart of FIG. 5A, a commercially available audio device using USB communication performs data transfer of stereo audio data by assigning a data transfer rate of 1536 bits / frame to the isochronous system.

  However, at the above data transfer rate, if the digital data transfer from the PC 1 to the intermediate circuit 10 is temporarily interrupted in the PC 1 due to the operation of other applications, etc. In the present embodiment, when performing the isochronous USB communication, a transfer rate several times (for example, 192 bytes / frame) of a required transfer rate (for example, 768 bytes / frame), that is, a communication frame is used. Reserve the upper bandwidth.

  Next, specific data transfer operations of the PC 1, the intermediate circuit 10, and the audio device 11 will be described with reference to FIG. 1 again.

  The procedure for transferring the audio data from the PC 1 to the memory controller 4 of the intermediate circuit 10 is the same as in the first embodiment.

  The memory controller 4 constantly monitors the audio data accumulation state of the memory 5 and controls the accumulation or erasure of the audio data in the AV data accumulation means according to the accumulation state of the audio data.

  Specifically, the memory controller 4 supplies the audio data so that the memory 5 always stores a predetermined amount or more of the audio data. Among the audio data stored in the memory 5, the memory controller 4 is already a digital audio transmitter. The audio data transferred to 7 is sequentially deleted.

  On the other hand, in order to prevent the supply of the audio data from being too fast and causing the memory 5 to overflow, the memory controller 4 temporarily transfers the audio data to the USB controller 3 when the memory 5 is full of the audio data. Instruct the interruption. Upon receiving the instruction, the USB controller 3 transmits the instruction to the PC 1 by the control transfer of USB communication. The control transfer is data transfer mainly used for device configuration and control signal communication in USB communication.

  Receiving the instruction, the PC 1 stops the transfer of the audio data, and instead transfers dummy data of the same transfer speed as that of the audio data, that is, 768 bytes / frame. As a result, since a constant amount of data is always transferred from the PC 1 to the intermediate circuit 10 per frame, the isochronous standard in USB communication is satisfied even when the audio data is not transferred.

  In this case, the dummy data transferred by the PC 1 is discarded by the USB controller 3 and is not stored in the memory 5. Therefore, as the intermediate circuit 10 continues to output the audio data to the audio device 11, the data amount of the audio data stored in the memory 5 decreases. As a result, when the audio data stored in the memory 5 falls below a predetermined amount, the memory controller 4 notifies the USB controller 3 to that effect, and the USB controller 3 that has received the notification transfers the PC 1 by the control transfer. To resume the transfer of the audio data.

  The PC 1 that has received the transfer restart request transfers the audio data again at a transfer rate of 768 bytes / frame until the capacity of the memory 5 becomes full.

  The time chart of FIG. 3B shows a state in which the PC 1 mixes and transfers the audio data and the dummy data according to the procedure described above.

  As a result, even when the digital data transfer from the PC 1 is temporarily interrupted due to the lack of processing capability of the CPU in the PC 1, the audio data can be output reliably and stably. Further, when the digital data transfer from the PC 1 is temporarily interrupted and then resumed, the digital data can be supplied from the PC 1 to the data transfer device at a high speed, so that the influence of the data transfer interruption from the PC 1 can be further reduced. It becomes.

  FIG. 4 is a flowchart for explaining the outline of the data transfer operation step by step when the intermediate circuit 10 and the PC 1 according to the present embodiment transfer a plurality of the audio data. As shown in the figure, the data transfer operation can be represented by steps S1 to S5. These steps S1 to S5 will be described in order.

  In S1, the USB controller 3 requests the PC 1 to transfer a predetermined amount of the audio data. When the transfer of the audio data from the PC 1 starts, the process proceeds to step S2.

  In S2, the USB controller 3 determines whether or not the received audio data is the final data to be transferred, that is, the last audio data. Specifically, if the received audio data is the final data, a notification to that effect is transferred from the PC 1 to the USB controller 3, so the USB controller 3 confirms the presence or absence of the notification.

  If it is determined in S2 that the audio data received by the USB controller 3 is the final data, the USB controller 3 ends the communication with the PC1.

  On the other hand, if it is determined in S2 that the audio data received by the USB controller 3 is not final data, the process proceeds to step S3.

  In S3, the USB controller 3 accesses the memory controller 4 to monitor the amount of audio data stored in the memory 5, and whether the memory 5 is full, that is, whether the capacity of the memory 5 is free. Judging.

  In S3, if the USB controller 3 determines that the memory 5 is not full, that is, the memory 5 has a free space, it continues to receive the audio data and repeats the steps S2 to S3. .

  On the other hand, if the USB controller 3 determines in S3 that the memory 5 is full, that is, there is no free space in the memory 5, the process proceeds to S4.

  In S4, the USB controller 3 requests the PC 1 to interrupt the transfer of the audio data. Receiving the interruption request, the PC 1 interrupts the transfer of the audio data and starts transferring the dummy data instead.

  Even after the transfer of the audio data is interrupted, the intermediate circuit 10 continues to output the audio data at a constant speed. On the other hand, as described above, the memory controller 4 sequentially deletes the audio data already transferred to the digital audio transmitter 7 among the audio data stored in the memory 5. Audio data will decrease over time.

  In S5, the USB controller 3 accesses the memory controller 4 again to monitor the amount of data stored in the memory 5, and whether or not the remaining data in the memory 5 has become less than a predetermined amount, that is, the capacity of the memory 5 It is determined whether or not a vacancy has occurred.

  If the USB controller 3 determines in S5 that the remaining data in the memory 5 is not less than the predetermined amount, that is, that there is no free space in the memory 5, the memory controller 5 repeats the above step S5, thereby 5 waits for the audio data stored in 5 to decrease.

  In S5, if the USB controller 3 determines that the remaining data in the memory 5 is equal to or less than the predetermined amount, that is, the capacity of the memory 5 is empty, the process returns to the step of S1 and the USB controller 3 Again, the PC 1 is requested to transfer a predetermined amount of the audio data.

[Embodiment 3]
Further embodiments of the present invention will be described below with reference to the drawings.

  The hardware configuration of the intermediate circuit and the PC according to the present embodiment is also the same as that of the intermediate circuit 10 and the PC 1 shown in FIGS.

  FIG. 5 is an explanatory diagram showing a time chart of a communication frame in data communication between the intermediate circuit 10 and the PC 1 of the present embodiment. As shown in the figure, in this embodiment, bulk USB communication is employed for transferring audio data in the data communication.

  The bulk method is one of the data transfer methods defined in USB communication, which is different from the isochronous method described above. If a free area occurs in a communication frame, a new packet is assigned to the free area and data is transferred. This is a data transfer method in which a large amount of data is transferred by transferring.

The above bulk system has the following characteristics a. To c.
a. Data transfer is performed by assigning a packet containing data of a maximum of 512 bits to an empty area of a communication frame and transferring the packet.
b. If a transfer error occurs during target data transfer in the bulk method, the missing data can be retransmitted.
c. When communication lines are crowded with transfer data using a transfer method with a higher priority, such as an isochronous method, in order to secure the bandwidth for data transfer, the target data for the bulk method has a transfer order To be deferred.

  The bulk method is suitable for transferring a large amount of data while ensuring the reliability of the transfer data.

  Generally, when a PC transfers audio data, it is often not communicating with a device other than an audio device. In such a case, by adopting the above bulk method, the free space of the communication frame is reduced. Effective use makes it possible to transfer a large amount of audio data.

  Conventionally, when audio data is transferred by the bulk method, loss of real-time property due to data loss, that is, instantaneous sound interruption often occurs. However, in the present invention, the intermediate circuit 10 has the above-described problem. The above problem is solved by providing the memory 5 for storing the audio data.

  Note that the USB high-speed transfer standard (Revision 1.1) is a maximum of 12 Mbps, so if 1 frame is set to 1 ms, for example, simple calculation transfers audio data of a maximum of 12000 bits / frame = 1500 bytes / frame by the above bulk method. It becomes possible. Actually, since a part of transfer data by USB communication is used as a synchronization signal or a control signal, the data amount of all 12000 bits / frame is not allocated to the bulk method. According to the USB communication standard, The amount of data that can be transferred as the bulk method is determined to be 512 bits × 19 packets = 9728 bits, that is, a maximum of 1216 bytes / frame per frame.

  As shown in FIG. 5, in this embodiment, bulk USB communication is employed for audio data transfer in the data communication, and the audio data is batch transferred over a long period of time in one frame. Then, it can be seen that the data transfer is interrupted.

  The state of subsequent data transfer will be described again with reference to FIG. As the audio data is output from the intermediate circuit 10 to the external audio device 11 (see FIG. 1), the audio data stored in the memory 5 decreases. When the audio data stored in the memory 5 becomes less than a predetermined amount and a notification to that effect is received from the memory controller 4, the USB controller 3 sends the audio data for the free capacity of the memory 5 to the PC 1 by the control transfer. Request. Receiving the request for audio data, the PC 1 resumes the transfer of the audio data by the bulk method again.

  FIG. 6 is a flowchart illustrating an outline of control in the intermediate circuit 10 of the present embodiment. The control includes steps S6 to S9, and steps S6 to S9 will be described in order.

  In S6, the USB controller 3 requests the PC 1 to transfer a predetermined amount of the audio data. When the transfer of the audio data from the PC 1 starts, the process proceeds to step S7.

  In S7, the USB controller 3 determines whether or not the received audio data is the final data to be transferred, that is, the last audio data. Specifically, if the received audio data is the final data, a notification to that effect is transferred from the PC 1 to the USB controller 3, so the USB controller 3 confirms the presence or absence of the notification.

  If it is determined in S7 that the audio data received by the USB controller 3 is final data, the USB controller 3 ends communication with the PC 1.

  On the other hand, if it is determined in S7 that the audio data received by the USB controller 3 is not final data, the process proceeds to step S8.

  In S8, the USB controller 3 determines whether or not the reception of the specified amount of data has been completed, that is, whether or not the data amount of the audio data transferred from the PC1 has reached the specified amount requested to the PC1 in S6. to decide.

  In S8, it is determined that the USB controller 3 has not finished receiving the specified amount of data, that is, the data amount of the audio data transferred from the PC 1 has not reached the specified amount requested to the PC 1 in S6. For example, the end of the data reception is awaited by repeating the steps S7 to S8.

  On the other hand, if it is determined in S8 that the USB controller 3 has finished receiving the specified amount of data, that is, the data amount of the audio data transferred from the PC1 has reached the specified amount requested to the PC1 in S6. , The process proceeds to step S9. Note that the intermediate circuit 10 continues to output the audio data at a constant speed even after the reception of the specified amount of data is completed. On the other hand, as described above, the memory controller 4 sequentially deletes the audio data already transferred to the digital audio transmitter 7 among the audio data stored in the memory 5. Audio data will decrease over time.

  In S9, the USB controller 3 accesses the memory controller 4 to monitor the amount of data stored in the memory 5, and whether or not the remaining data in the memory 5 is less than or equal to the predetermined amount, that is, the capacity of the memory 5 is empty. It is determined whether or not

  If the USB controller 3 determines in S9 that the remaining data in the memory 5 is not less than the predetermined amount, that is, there is no space in the capacity of the memory 5, the memory controller 5 repeats the step in S9 to 5 waits for the audio data stored in 5 to decrease.

  In S9, if the USB controller 3 determines that the remaining data in the memory 5 is equal to or less than a predetermined amount, that is, the memory 5 has a free space, the process returns to the step of S6, and the USB controller 3 The PC 1 is requested to transfer the audio data for the free capacity.

[Embodiment 4]
Further embodiments of the present invention will be described below with reference to the drawings.

  FIG. 7 is a block diagram showing a hardware configuration in which the intermediate circuit 10 shown in FIG. 1 includes a decode circuit 20 (AV data decompression means). Constituent members common to those in FIG. 1 are denoted by common member numbers and description thereof is omitted.

  In FIG. 7, a decoding circuit 20 is connected between the memory controller 4 and the digital audio transmitter 7 and is an arithmetic circuit for decompressing and restoring the audio data transferred from the memory controller 4.

  Audio data stored in the PC 1 is often compressed by a data compression format such as MP3 with emphasis on the capacity of the recording medium and convenience when obtaining it from various networks. Therefore, when the audio device 11 cannot perform reproduction or the like corresponding to the data compression format, the PC 1 normally performs intermediate processing after decompressing and restoring the compressed audio data to the original state by the CPU or the like. It will be transferred to the circuit 10.

  However, when the audio data is transferred by the USB communication or the like after the PC 1 expands the audio data as described above, the size of the audio data to be transferred becomes large, and the transfer of the audio data is It often occupies data transfer in USB communication on the same communication line and often hinders USB data transfer between the PC 1 and devices other than the intermediate circuit 10.

  For example, since the data compression rate of MP3 reaches about 1/10, when the audio data compressed by MP3 is expanded, the audio data to be transferred from the PC 1 to the intermediate circuit 10 is about 10 times the data amount. Will increase.

  Further, as described above, when the PC 1 performs the decompression and restoration of the audio data, since the CPU processing capacity of the PC 1 is consumed for the decompression process, the CPU processing capacity regarding the transfer of the audio data tends to be insufficient. There is a high possibility that the audio data to be transferred is lost or the transfer of the audio data is interrupted.

  Therefore, in the present embodiment, the audio data contained in the digital data transferred between the PC 1 and the intermediate circuit 10 is transferred from the PC 1 to the intermediate circuit 10 in a compressed state. The audio data that has been compressed and transferred is decompressed and restored by the decoding circuit 20 in the intermediate circuit 10.

  Next, specific data transfer operations of the PC 1, the intermediate circuit 10, and the audio device 11 will be described with reference to FIG. However, the operation from the time when the USB controller 3 of the intermediate circuit 10 extracts the temporally continuous audio data from the digital data transferred from the PC 1 and transfers it to the memory controller 4 is the same as in the first embodiment and FIG. Therefore, the description thereof is omitted here.

  The memory controller 4 that has received the compressed audio data from the USB controller 3 temporarily stores the audio data in the memory 5, and then reads out the audio data from the memory 5 according to the request of the decoding circuit 20. Forward to.

  The decoding circuit 20 decompresses the compressed audio data and sends it to the digital audio transmitter 7 at a constant transfer rate.

  The digital audio transmitter 7 converts the audio data into an interface signal in synchronization with the timing signal generated by the audio timing generation circuit 6 (see FIG. 1), and transfers the interface signal to the optical transmission unit 8.

  The optical transmission unit 8 converts the interface signal as an electrical signal into an optical signal and outputs the optical signal to the optical cable 9. The optical cable 9 transmits the optical signal to an external audio device 11, and the audio device 11 performs music reproduction and recording based on the transmitted optical signal. The data transfer speed in the above operation and the management of the audio data storage state of the memory 5 by the memory controller 4 are the same as those in the first embodiment and FIG.

  According to the above configuration, since the audio data is transferred from the PC 1 to the intermediate circuit 10 in a compressed state, the data amount of the transferred audio data and the digital data including this is reduced, and the PC 1 and the intermediate data are reduced. The communication burden on the circuit 10 is reduced. Further, since the decompression process of the compressed audio data is performed not by the PC 1 but by the decoding circuit 20 provided in the intermediate circuit 10, the CPU processing capacity of the PC 1 is not consumed by the decompression process.

  As a result, it is possible to further suppress the data loss that occurs when the audio data is transferred from the PC 1 and the sound interruption phenomenon that occurs during reproduction or duplication of the audio data due to such data loss. In addition, if the same amount of audio data is transferred, the capacity of the data transfer can be increased as compared with the case where the decompressed audio data is transferred. Therefore, in the data transfer using the same communication line, It becomes easy to transfer data other than audio data.

  8 (a) and 8 (b) both show the communication frame in the case where the control signal and the audio data are transferred between the intermediate circuit 10 and the PC 1 in the USB data transfer of the same line. It is explanatory drawing showing a time chart. FIG. 4A shows an example in which USB communication is performed by an isochronous method, and FIG. 4B shows an example in which USB communication is performed by a bulk method.

[Embodiment 5]
In the data transfer device and the data transfer method described in the first to fourth embodiments, the audio application 14 (see FIG. 2) on the PC 1 instructs the audio from the PC 1 when the user instructs the audio data to be stopped. Even if the data transfer is stopped, the audio data remains in the memory 5 of the intermediate circuit 10, and the remaining audio data continues to be output from the intermediate circuit 10 to the audio device 11. That is, there arises a problem that the user instruction is not immediately reflected in the output state of the audio data.

  Therefore, in the present embodiment, the output of the audio data from the intermediate circuit 10 is controlled based on the control signal transferred from the PC 1 together with the audio data.

  A specific procedure of the control will be described as follows.

  When the audio application 14 on the PC 1 receives the audio data reproduction stop instruction from the user, the audio application 14 stops the transfer of the audio data from the PC 1 and simultaneously sends a control signal to the intermediate circuit 10 to stop outputting the audio data to the USB driver. 15 to transfer. The USB driver 15 transfers the control signal in addition to the audio data to the USB controller 3 of the intermediate circuit 10.

  The USB controller 3 separates the control signal from the transferred digital data. The USB controller 3 controls the memory controller 4 according to the control signal, thereby stopping the reading of the audio data from the memory 5 and the transfer to the digital audio transmitter 7. Further, the memory controller 4 erases the audio data stored in the memory 5 as necessary.

  When the decoding circuit 20 is provided in the intermediate circuit 10 as in the fourth embodiment, the USB controller 3 similarly controls the memory controller 4 to read the audio data from the memory 5. The transfer to the decoding circuit 20 is stopped, or the audio data stored in the memory 5 is deleted. Further, the USB controller 3 stops the decoding process of the decoding circuit 20 and the output of the audio data from the digital audio transmitter 7 and the optical transmission unit 8 as necessary.

  As a result, the user's instruction can be immediately reflected in the output state of the audio data, and the user can directly operate the output state of the audio data.

  In the above description, the operation in the case where the user instructs to stop the reproduction of the audio data has been described. However, the contents of the control signal are not limited to the reproduction of the audio data, but the reproduction of the audio data is resumed. Or a change in the playback order.

[Others]
A data transfer device according to the present embodiment is connected between a digital data output device and an external device of the digital data output device, and is a data transfer device that transfers digital data from the digital data output device to the external device. The digital data transfer between the digital data output device and the external device is performed by USB communication, and AV data continuous in time is extracted from the digital data transferred from the digital data output device. AV data extracting means, AV data accumulating means for accumulating the AV data extracted by the AV data extracting means, reading the AV data from the AV data accumulating means, and continuously to the external device at a constant speed And AV data output means for outputting to.

  In the above-described embodiment, temporally continuous AV data refers to audio / video data in general for performing continuous reproduction or duplication while changing over time.

  According to the above embodiment, the AV data included in the digital data transferred from the digital data output device is transferred to the external device via the connected data transfer device. That is, the AV data extraction means of the data transfer device extracts the AV data from the digital data transferred from the digital data output device, and the extracted AV data is temporarily stored in the AV data storage means. After that, it is read by the AV data output means and outputted to the external device.

  Further, according to the embodiment, the digital data output device and the data transfer device are simply connected by USB communication that is widely used as an interface for connecting the digital data output device and the peripheral device, so that high-speed data can be obtained. Transfer can be performed.

  Therefore, by always storing a certain amount or more of AV data in the AV data storage means, the digital data from the digital data output device is caused by insufficient processing capacity of the CPU in the digital data output device. Even when the transfer is temporarily interrupted, the AV data is stably output from the AV data storage means to the external device.

  As a result, data is lost when AV data is transferred between the digital data output device and the external device without imposing a special burden on the user, and AV data is lost due to such data loss. It is possible to suppress the frame cut-off and the sound cut-out phenomenon of music that occur during playback and duplication.

  Further, according to the above embodiment, the output of the AV data can be controlled accurately and simply based on a fixed clock timing, so that various data communication based on the clock timing can be used for the transfer of the AV data. The standard can be used.

  Preferably, the data transfer device includes storage state control means for controlling storage or erasure of the AV data in the AV data storage means in accordance with the storage state of the AV data.

  According to the embodiment, even when the storage capacity of the AV data storage means is limited, the AV data storage means is controlled by controlling the storage or erasure of the AV data by the storage state control means. It is possible to appropriately control the contents of AV data to be accumulated and the data amount.

  In the data transfer device, the transfer rate of AV data contained in the digital data transferred from the digital data output device is the transfer rate of the AV data between the data transfer device and the external device. Larger is preferred.

  According to the embodiment, the data amount of the AV data stored in the AV data storage means exceeds the data amount of the AV data read from the AV data storage means, and the AV data storage It is possible to always store and secure a certain amount or more of AV data in the means.

  As a result, even when digital data transfer from the digital data output device is temporarily interrupted due to insufficient processing capability of the CPU in the digital data output device, the AV data can be reliably and stably transferred to the external device. Data can be output. In addition, when the digital data transfer from the digital data output device is temporarily suspended and resumed, the digital data can be supplied from the digital data output device to the data transfer device at a high speed. The influence of data transfer interruption can be further reduced.

  In the data transfer device, the USB communication is preferably an isochronous method.

  According to the embodiment, in the USB communication, a predetermined amount of data transferred per frame is preferentially guaranteed. As a result, even when other data transfer is performed simultaneously on the same USB communication line, the transfer of the AV data subject to the isochronous method is less likely to be interrupted by the other data transfer.

  In the data transfer device, the USB communication is preferably a bulk method.

  According to the embodiment, in the USB communication, if there is a free area in the communication frame, packet transfer using the free area is performed, so that a large amount of AV data can be transferred. Further, when an error occurs during the AV data communication, the AV data can be reliably transferred without omission by retransmitting the AV data.

  In the data transfer apparatus, AV data included in the digital data transferred from the digital data output device is compressed, and AV data expansion means for expanding the AV data is provided. It is preferable.

  According to the embodiment, since the AV data is transferred from the digital data output device to the data transfer device in a compressed state, the AV data to be transferred and the digital data including the AV data are transferred. The amount of data is reduced, and the communication burden of the digital data output device and the data transfer device is reduced. Further, the decompression processing of the compressed AV data is performed not by the digital data output device but by the AV data decompression means of the data transfer device, so that the CPU processing capability of the digital data output device is decompressed by the decompression processing. It is not consumed by processing.

  As a result, data loss that occurs when AV data is transferred between the digital data output device and the external device, and frame loss or music that occurs during reproduction or duplication of AV data due to such data loss. It is possible to further suppress the sound interruption phenomenon. In addition, if the same amount of AV data is transferred, the capacity of the data transfer can be increased compared to the case where the decompressed AV data is transferred. Therefore, in the data transfer using the same communication line, It becomes easy to transfer data other than AV data.

  Furthermore, in the data transfer device, the AV data output means preferably controls the output of the AV data based on a control signal included in the digital data transferred from the digital data output device.

  According to the embodiment, the output of the AV data by the AV data output means is controlled by the control signal. For example, when the user instructs the digital data output device to stop the transfer of the AV data, not only the digital data transfer from the digital data output device to the data transfer device is stopped, but also from the AV data output means. The output of the AV data can be stopped.

  As a result, the user's instruction can be immediately reflected in the output state of the AV data, and the user can directly operate the output state of the AV data.

  The present invention can be applied to digital data transfer between a digital data output device such as a player device including a personal computer (PC) or a mobile phone and an external device.

It is a block diagram showing the structure of the intermediate circuit which concerns on one Embodiment of this invention. It is a block diagram showing the internal structure of PC shown in FIG. (A) (b) is explanatory drawing showing the time chart of the communication frame in the data communication between the intermediate circuit which concerns on the further embodiment of this invention, and PC. It is a flowchart explaining the outline of the data transfer operation | movement in case the intermediate | middle circuit and PC which concern on the said embodiment transfer several said audio data in steps. It is explanatory drawing showing the time chart of the communication frame in the data communication between the intermediate circuit and PC which concern on further embodiment of this invention. It is a flowchart explaining the outline of the control in the intermediate circuit of the said embodiment. FIG. 2 is a block diagram showing a hardware configuration in which a decoding circuit is built in the intermediate circuit shown in FIG. 1. In the case where the control signal and the audio data are transferred between the intermediate circuit according to the further embodiment of the present invention and the PC by (a) by isochronous USB communication and (b) by bulk USB communication. It is explanatory drawing showing the time chart of the communication frame in FIG.

Explanation of symbols

1 PC (digital data output device)
3 USB controller (AV data extraction means)
4. Memory controller (accumulation state control means)
5 Memory (AV data storage means)
7 Digital audio transmitter (AV data output means)
8 Optical transmission unit (AV data output means)
10 Intermediate circuit (data transfer device)
11 Audio equipment (external equipment)
20 Decoding circuit (AV data decompression means)

Claims (2)

In a data transfer apparatus that receives AV data composed of digital data and a control signal for controlling the AV data, and transfers the AV data or decoded AV data obtained by decoding the AV data.
The AV data, control signal, and decoded AV data are transferred by USB communication.
AV data extracting means for extracting AV data from the received signal;
AV data storage means for storing the AV data extracted by the AV data extraction means;
A data transfer apparatus comprising: AV data output means for continuously outputting from the AV data storage means at a constant speed in accordance with a control signal of the reception signal. In a data transfer method for transferring digital data from a digital data output device to an external device of the digital data output device by USB communication, temporally continuous AV data from the digital data transferred from the digital data output device Extracting the
Accumulating the extracted AV data;
A method of controlling the data transfer apparatus, comprising: reading the stored AV data and continuously outputting the AV data to the external device at a constant speed.

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