Abstract:
A command synchronization establishment system using a network wherein data is transferred by an isochroous transfer, a command is transferred by an asynchronous transfer, and a synchronized clock is shared by apparatuses connected to the network, the system comprising a controller connected to the network, comprising a transmitter that transmits a command including a time-stamp to a target apparatus by using the asynchronous transfer, and the target apparatus connected to the network, comprising a receiver that receives the command, a storage device that temporally stores the received command in order not to execute the received command instantly, and a executing device that executes the received command in accordance with the time-stamp included in the command to be executed.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application is based on Japanese Patent Application 2002-250472, filed on Aug. 29, 2002, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    A) Field of the Invention  
           [0003]    This invention relates to a technique for establishing command synchronization wherein a command can be executed at a time designated by a time-stamp added to the command when the command is transmitted to a target from a controller via a communication network.  
           [0004]    B) Description of the Related Art  
           [0005]    The IEEE 1394 Standard is well known as a recent serial interface standard. In this Standard, data is transmitted in real time by an isochronous transfer in which a right for certainly transmitting data at a fixed cycle is given to each node. This is suitable for transferring data that is important to be transferred particular in real time such as images and sound. Generally, in the network using this Standard, by using a command format determined by IEC61883-1, a device dealing with audio and video transmits and receives information by an asynchronous transaction (command) transferred after isochronous area. For example, it conventionally has been performed that a command is transmitted in asynchronous from a PC to an audio device wherein the transmission is controlled by the PC with making the PC a controller and audio device a target.  
           [0006]    In the network based on the IEEE 1394 Standard, it is considered that an isochronous packet is certainly transferred during a transmission cycle started by a cycle signal generated in accordance with a timing signal of 125μ-second cycle. Then, in a transmitter station, the isochronous packet added with a time-stamp corresponding to time difference of the above-described timing signal and the sampling timing on the data sampled from an analogue signal at a predetermined sampling timing is generated to be transmitted. In a receiver station, a system that reconstructs the data on the time axis based on the before-described time-stamp is considered (referrer to Japanese Patent Application Laid-open No. Hei-10-32606).  
           [0007]    In the network based on the above-described IEEE 1394 Standard, when receiving timings for a plurality of receiving devices are needed to be agreed with each another, they are controlled by the above-described command although it is not easy to agree those timings. For example, in a case that each command is transmitted from the controller to the first and second targets to control those target devices, it was difficult to establish synchronization, that is, agreeing operating timings of the targets. Also, a case is considered that a command is received from other controller to be executed in one target device, and it was not possible to execute the desired command always at the same time. Moreover, in a different type of the target device, since executing speed is different by type of the devices, the timing may be shifted.  
           [0008]    Also, in the network based on the IEEE 1394 Standard, when an isochronous transfer area is large, an asynchronous transfer area will be decreased, and there is a case that the command to be transferred in the asynchronous transfer area will be transferred in the next cycle may occur frequently. By that, command transfer will be delayed, and the controlling timing between the plurality of targets may be shifted.  
           [0009]    The technique disclosed in JP-A Hei10-32606 is using the time-stamp in order to reconstruct waveform data, etc. to be transferred by isochronous packets on a time axis, and is not a technique at a time when to transfer the command by an asynchronous packet.  
         SUMMARY OF THE INVENTION  
         [0010]    It is an object of the present invention to provide a command synchronization establishment system that can establish synchronization of timings of controls between targets by a command transmitted from a controller to the targets in a network having a structure for transferring wave data etc. by the isochronous transfer in real time and a structure for transferring a command by the asynchronous transfer.  
           [0011]    According to one aspect of the present invention, there is provided a command synchronization establishment system using  
           [0012]    a network wherein data is transferred by an isochroous transfer, a command is transferred by an asynchronous transfer, and a synchronized clock is shared (used together) by apparatuses connected to the network, the system comprising: a controller connected to the network, comprising a transmitter that transmits a command including a time-stamp to a target apparatus by using the asynchronous transfer; and the target apparatus connected to the network, comprising a receiver that receives the command, a storage device that temporally stores the received command in order not to execute the received command instantly, and a executing device that executes the received command in accordance with the time-stamp included in the command to be executed.  
           [0013]    According to the present invention, synchronization of the processes corresponding to the command transmitted by the asynchronous transfer can be established in the targets. For example, audio wave data can be received at the same time by making the command a reception start command of the audio wave data (a logical connection to the transmission) and by designating a reception timing in the command.  
           [0014]    Also, by assigning scene setting changes of mixers and parameter changes of effectors to the commands, a synchronized remote control of each device becomes possible. Also, either one of a method for executing the command immediately or a method for executing the command at a time of the time-stamp can be designated.  
           [0015]    By using a part of the area for the time-stamp data representing a time as a flag for the designation, the command data can be transmitted without increasing an overall amount of the command data.  
           [0016]    Moreover, the synchronization can be perfectly established among the devices of different versions by designating a command execution terminating time. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIGS. 1A and 1B are diagrams showing examples of a network structure according to an embodiment of the present invention.  
         [0018]    [0018]FIG. 2 is a diagram showing an example of a packet arrangement on the bus in an isochronous transfer mode.  
         [0019]    [0019]FIGS. 3A and 3B are command flow diagrams between the controller and the target.  
         [0020]    [0020]FIGS. 4A and 4B are diagrams showing a register space of the target.  
         [0021]    [0021]FIGS. 5A to  5 C are diagrams showing an example of a command packet.  
         [0022]    [0022]FIG. 6 is a timing diagram showing a progress of the operation in each device of the system.  
         [0023]    [0023]FIGS. 7A and 7B are flows of a process in a target device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    [0024]FIGS. 1A and 1B show examples of a network structure according to an embodiment of the present invention. FIG. 1A is a block diagram showing a hardware structure of the network, and FIG. 1B shows an example of a hardware structure corresponding to the structure shown in FIG. 1A. As shown in FIG. 1B, a PC  101 , a mixer  102 , an effecter  103 , an AD converter  104 , a recorder  105  and a loudspeaker  106  are physically connected to the network based on the IEEE 1394 Standard. This hardware structure shown in FIG. 1B can be considered logically as the structure shown in FIG. 1A. A bus  110  is a virtual bus (serial bus) for performing data transfer between devices  101  to  106 . Each device connected to this bus  110  is called a node.  
         [0025]    In the embodiment of the present invention, the network structure operates a data transmission as a system based on the IEEE1394 Standard. Particularly, the PC  101  transmits commands to the devices  102  to  106  as a controller to control the devices. Each of the other devices receives the controlling commands transmitted from the controller (PC  101 ) as a target and operates a process corresponding to the instruction of each command. In this specification, the controller is a device to transmit a command, and the target is a device to receive the command.  
         [0026]    The mixer  102  arbitrary performs mixing of digital sound signals of plurality of input channels and outputs a mixed signal (or mixed signals) to arbitral output channels. The mixer  102  equips with plurality of faders and can set each channel level with the fader. Also, the mixer  102  has a function of scene setting. The scene indicates a mixing status and a connecting status at a certain moment. The setting statuses are stored as one scene, and setting statuses can be easily reconstructed by recalling the stored scene. The effecter  103  is a device that adds various kinds of effects to the digital sound signal. The AD converter is a device that converts the input analogue sound signal into digital sound signal. The recorder  106  is a sound system that sounds the analogue sound data converted from the digital musical data. A wiring condition of each device can be set arbitrary from, for example, the PC  101 .  
         [0027]    [0027]FIG. 2 is a diagram showing an example of a packet arrangement on the bus in an isochronous transfer mode. Three types of packets, a cycle start packet  201 , an isochronous packet  202  and an asynchronous packet  203 , are arranged on the time axis. Arrows  211  and  212  indicate a timing signal (cycle sync) that is considered as a standard timing in this system. This timing signal is a signal at a 125μ-second cycle (8 kHz).  
         [0028]    The cycle start packet  201  is a packet transmitted from a node called a cycle master that is one of plurality of nodes connected to this bus. A new transmission cycle is started by the cycle start packet. The cycle master has a precise clock generator, and it tries to transmit the cycle start packet at a time interval of the above-described timing signal. However, when the transmission of other packet is in progress, transmission of the above-described cycle start packet is held to be waiting until the transmission is completed. A reference number  214  indicates delay time (start delay), and this delay time is encoded in the above-described cycle start packet and transmitted to each node. Moreover, the packet transmitted from the above-described node is guaranteed to be received by other node in the same clock period.  
         [0029]    Each node equips with a cycle time register of 32 bits. By using the lower 12 bits, each cycle time register counts a clock signal of 24.576 MHz (cycle of 40.7 n seconds) by dividing by 3072 as a divisor and counts a standard cycle of the above-described 8 kHz by the upper 13 bits.  
         [0030]    Then, it is consisted to count seconds from the upper 7 bits (FIGS. 4A and 4B). Then, the above-described cycle master makes the cycle time registers of all other nodes copy contents of its own cycle time register, all the nodes are synchronized within a specific phase difference. By doing that, the common time standard is guaranteed in this network.  
         [0031]    The isochronous packet  202  is a channel used for transmitting the data requiring a precise timing reference such as digital sound, video and musical performance data. These isochronous packets  202  are guaranteed to be certainly transmitted in each transmission cycle. Also, the above-described asynchronous packet  203  is a packet transmitted asynchronously when there is a blank time in the transmission cycle after finishing the transmission of the above-described isochronous packet  202 . In the embodiment of the present invention, a command is transmitted from the PC  101  to each target devices  102  to  106  by using this asynchronous packet  203  to control each device.  
         [0032]    [0032]FIGS. 3A and 3B are command flow diagrams between the controller and the target. When the command is transmitted from the controller to the target by using the asynchronous packet as shown in the arrow  301 , the target executes the command and responses Complete response  302  indicating that the command has executed within 100 mm seconds to the controller. It is difficult to establish synchronization of the operations among the plurality targets by only the method.  
         [0033]    [0033]FIG. 3B shows a command flow between the controller and the target in the system of the embodiment of the present invention shown in FIGS. 1A and 1B. A command  311  is transmitted from the controller to the target. This command  311  includes a time-stamp T_res. The time-stamp T_res is a data to designate a time to execute the command. The target that received the command  311  transmits Interim response  312  to the controller within 100 mm seconds. The Interim response  312  is a responce representing that the received command is in a received condition. When a cycle time representing the present time reaches the time represented by the time-stamp T_res, the command is executed, and a Complete response  313  is transmitted to the controller. In FIG. 3B, since the time to execute the command can be designated by each target, synchronization of the operations among the plurality of targets can be established.  
         [0034]    [0034]FIG. 4A shows a register space of the target in the embodiment of the present invention. As shown in FIG. 4B, a cycle time register  401  is consisted of a second counter (Second_count)  411  of 7 bits, a cycle counter (Cycle_count)  412  of 13 bits and a cycle offset (Cycle_offset)  413  of 12 bits. The second counter  411  counts in measures of second. The cycle counter  412  counts in measures of cycle (125 μsecond). The cycle offset  413  is a counter to count the standard clock (24.576 MHz, cycle of 40.7 n seconds) of the system by dividing by 3072 as a divisor. The value of the cycle offset  413  ranges from 0 to 3071. Therefore, normally it hardly happens that all of 12 bits of the cycle offset  413  are 1 (0×FFF in a hexadecimal scale; Ox represents a hexadecimal scale). The command register  402  is an area to be set the command transmitted from the controller.  
         [0035]    Each target device has such a register space. When the controller receives the transmitted cycle start packet, a cycle time included in the cycle start packet is written in the cycle time register  401  of each device. By that, synchronization can be established among all the devices connected to the network.  
         [0036]    [0036]FIG. 5A shows an example of a command packet that is transmitted from the controller to the target in the embodiment of the present invention. The command packet includes a fixed header information (AV/C header, type, bender ID). Following to the header information, time-stamp areas  501  and  502  are provided, and command areas  503  and  504  are provided. Formats of the time-stamps  501  and  502  are the same as those of the cycle time explained with reference to FIG. 4B. These time-stamps  501  and  502  are the command executing timing T_res explained with reference to FIG. 3B.  
         [0037]    Especially, in this embodiment, the cycle offset  413  is used as a flag because the cycle offset normally does not become 0×FFF in order to have a selection (the designation) of executing the process as shown in FIG. 3A or as shown in FIG. 3B. That is, when the cycle offset of the time-stamp  501  and  502  in the command transmitted from the controller is 0×FFF, the command is immediately executed as FIG. 3B. When the cycle offset of the time-stamp  501  and  502  in the command transmitted from the controller is not 0×FFF, the command is executed as FIG. 3B after the time represented by the time-stamps  501  and  502 .  
         [0038]    [0038]FIG. 6 is a timing diagram showing a progress of the operation in each device of the system in FIGS. 1A and 1B. As indicated by the reference numbers  601  to  606 , the PC  101  transmits the commands A, B, C, D and B′ to the mixer  102 , the recorder  105 , the effecter  103 , the AD converter  104  and a recorder  2  (not shown in FIGS. 1A and 1B). The times t_A, t_B, t_C, t_D and t_E represent time-stamps stored in the commands A, B, C, D and E. The time-stamp registered in the command B′ is “t_B” as same as in the command B. The sequential order from the beginning to the end is following: t_D, t_B, t_A, t_E, and t_C.  
         [0039]    First, the command D is executed in the AD converter  104  at the timing of t_D. This is for executing the process of audio input port setting as indicated by reference number  615 . Next, the command B in the recorder  105  and the command B′ in the recorder  2  are executed at the timing t_B. This is for executing a recording start process as indicated by the reference numbers  613  and  616 . Since the time-stamps of the command B and B′ are the same t_B, the recording start timings in both recorders are synchronized. Next, the command A is executed in the mixer  102  at the timing of t_A, and a scene setting process is execited as indicated by the reference number  611 . Thereafter, the command E is executed in the mixer  102  at the timing t_E, and a changing process of a fader value as indicated by the reference number  612  is executed. Moreover, the command C is executed in the effecter  103  at the timing of t_C, and an effect setting process as indicated by the reference number  614  is executed.  
         [0040]    As described in the above, each device can be controlled at the timing represented by each time-stamp determined in advance, and the synchronized operation as a whole can be realized.  
         [0041]    [0041]FIGS. 7A and 7B are flows of the command reception event process in the target device of the embodiment of the present invention. The time-stamp of the received command is set to a work register OST at Step  701 . It is judged whether the lower 12-bit of OST is 0×FFF or not at Step  702 . When the lower 12-bit of OST is 0×FFF, the received command is executed immediately at Step  705 . Then, a response is transmitted at Step  706 , and the process is finished. When the lower 12-bit of OST is not 0×FFF, a synchronizing command event corresponding to the received command is set at Step  703 . Then, the Interim response is transmitted at Step  704 , and the process is finished.  
         [0042]    [0042]FIG. 7B shows a flow of the synthesizing command event at Step  703 . At Step  711 , a value of the cycle register representing the present time is set to a register CT, and it is judged that the CT becomes equal to or greater than OST or not at Step  712 . Step  711  and Step  712  are repeated to make the process wait until the register CT becomes equal to or greater than the register OST (CT&gt;=OST) as a result. When the CT becomes equal to or greater than OST, the received command is processed at Step  713 , the response is transmitted at Step  714 , and the process is finished.  
         [0043]    Moreover, instead of making the process wait at Step  712 , the command may be processed in advance, and the result of the process may be validated when the register CT becomes equal to or greater than the register OST (CT&gt;=OST). That is, the command may be terminated before the register becomes equal to or greater than the register OST (CT&gt;=OST), the process may be validated by adding only trigger at a timing of CT&gt;=OST. In this case, the time-stamp value OST in the command means a time when the execution of the command is finished instead of the time when the command is executed.  
         [0044]    However, the processing method of the command (FIG. 3A or FIG. 3B) is decided whether the flag that is in the cycle offset area in the time-stamps  501  and  502  in FIG. 5A is 0×FFF or not, the area used as the flag is not limited to be in the cycle offset area. For example, other area  511  in the command may be used as an area for the flag as shown in FIG. 5B.  
         [0045]    Also, although the time-stamps  501  and  502  are defined as the same format as the cycle time register, the format of the time-stamp in the command is not limited only to the above. As a time-stamp in the command, a part (for example, only the cycle counter and the cycle offset) of the cycle time register may be used. Moreover, the second counter cannot represent more than 127 seconds as far as the format is the same as the cycle time register because an area for the second counter is 7-bit. Then, as shown in FIG. 5C, areas of the time-stamps  521  and  522  are defined to be in the format in FIG. 4B as same as that shown in FIG. 5A, and an area of the time-stamp  523  is defined as an area to designate a time in measures of 128 seconds. By that, time after 128 seconds or more may be designated. In this case, it is necessary to have a register representing a time in measures of 128 seconds other than the cycle time register in FIG. 4 in the target side.  
         [0046]    Although, in the above-described embodiment, the example for controlling each device from the PC as a controller has been explained, the present invention can be applied to any case to establish a synchronization of operation of each device. For example, when the sound instruction commands are transmitted to a plurality of the target devices to make them sound, the sequencer reads the automatic performance data in advance, and each sound instruction command are transmitted to each target device in advance with the time-stamp representing a time to sound. By that, sounding timings at the plurality of target devices can be synchronized.  
         [0047]    Also an arbitral device in the network can be the controller or the target according to the embodiment of the present invention. Moreover, one device may have functions of both of the controller and the target devices.  
         [0048]    Although the example using the network based on the IEEE 1394 Standard has been explained in the above embodiment, the present invention can be applied to any communication system as far as having a structure for transferring a command in the asynchronous transfer mode, a structure for transferring wave data such as audio data, etc. in the isochronous transfer mode and a structure for establishing synchronization among devices having a common cycle time (clock).  
         [0049]    The present invention has been described in connection with the preferred embodiments. The invention is not limited only to the above embodiments. It is apparent that various modifications, improvements, combinations, and the like can be made by those skilled in the art.