JP3825848B2 - Communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus conforming to IEEE 1394-1995.
[0002]
[Prior art]
Currently, a system in which a plurality of devices are connected using a serial bus compliant with IEEE 1394-1995 (hereinafter referred to as IEEE 1394) and information signals and control signals are communicated between these devices is being studied.
Hereinafter, an example of a configuration of a communication device that transmits image data and data accompanying the device to the system configured as described above will be described with reference to FIG.
[0003]
In FIG. 5, the received packet received via the bus cable 501 is input to the receiver 503 through the physical layer 502. On the other hand, a transmission packet transmitted via the bus cable 501 is transmitted from the transmitter 504 to the bus cable 501 through the physical layer 502.
[0004]
Here, the received packet received via the bus cable 501 is composed of, for example, image data for one transmission packet and accompanying data. Of these, the image data is compressed image data reproduced from a digital VTR that compresses the amount of image data for one frame and performs recording and reproduction on 10 tracks, and 150 data per track. Blocks are recorded. Further, the image data for one transmission packet is composed of, for example, six data blocks.
[0005]
The value of the cycle time register 512 is set to substantially the same value between the nodes connected on the bus cable 501 serving as a transmission path in accordance with the IEEE 1394 standard.
[0006]
In the received packet, the packet header is removed by the receiver 503, the image data is input to the data buffer 505, and the data header is input to the data header buffer 506. The time data detection unit 507 connected to the subsequent stage of the data header buffer 506 checks whether there is hourly data per frame written in the data header once per frame accompanying the image data. If detected, the value is read from the data header buffer 506 and written to the first memory 508.
[0007]
When the time data detection unit 507 detects the next frame-by-frame data after receiving one frame of the packet, the contents of the first memory 508 are transferred to the second memory 509, and the first memory In 508, a newly detected hourly data value of the frame is written. The first and second memories 508 and 509 are controlled by the memory control unit 510.
[0008]
Next, the frame-by-frame data values written in the first memory 508 and the second memory 509 are sent to the computing means 511. Here, assuming that the time data value written in the first memory 508 is m1 and the time data value written in the second memory 509 is m2, the calculation means 511 calculates m1-m2. To obtain the frame period.
[0009]
FIG. 6 shows an outline of data in each component of the communication apparatus shown in FIG. In FIG. 6, reference numeral 601 denotes packet data input to the receiver 503, which is composed of a packet header, a data header, and compressed image data. Among these, the data header 602 is sent to the data header buffer 506, and the image data 603 is sent to the data buffer 505.
[0010]
In the data header 602, frame-by-frame data 604 is written once per frame along with the image data. Note that, during a period in which the data for each frame is not written, certain fixed data is written in the payload in which the data for each frame is to be written. When the time data detection unit 507 detects the hourly frame data 604 in the data header 602, the value is written in the first memory 508.
[0011]
When the time data detection unit 507 detects the time data for each frame again after one frame, the value written in the first memory 508 is transferred to the second memory 509 and 1 is stored in the second memory 509. The frame-by-frame data 606 before the frame is written, and the newly detected value of the frame-by-frame data 605 is written in the first memory 508. Then, the calculation means 511 performs the above calculation to obtain a frame period.
[0012]
[Problems to be solved by the invention]
However, in the above-described conventional example, the frame period of the image data obtained on the receiving side is a numerical output obtained by calculation from the time data of each frame. As it was difficult to use.
[0013]
Accordingly, an object of the present invention is to make it possible to easily generate a synchronization signal for a frame on the receiving side.
[0014]
[Means for Solving the Problems]
The communication apparatus according to the present invention, for example, subtracts predetermined time data from the time data detecting means for detecting time data from the received packet, the cycle time register defined by IEEE 1394-1995, and the value of the cycle time register. Subtracting means, and pulse generating means for generating a pulse corresponding to the frame period of the image data using the time data output from the subtracting means and the time data output from the time data detecting means. It is characterized by.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a configuration example of a communication apparatus according to the first embodiment of the present invention. In FIG. 1, packet data arriving from the bus cable 101 is input to the receiver 103 through the physical layer 102. On the other hand, the transmission packet is transmitted from the transmitter 104 to the bus cable 101 through the physical layer 102. It should be noted that the value of the cycle time register 112, which is the source of frame-by-frame data, is set to a value that is substantially common among the nodes in accordance with the IEEE 1394 protocol.
[0027]
In the received packet, the packet header is removed by the receiver 103, the image data is input to the data buffer 105, and the data header is input to the data header buffer 106. The time data detection unit 107 connected to the subsequent stage of the data header buffer 106 checks whether there is hourly frame data written in the data header once per frame accompanying the image data. If detected, the value is read from the data header buffer 106.
[0028]
The frame-by-frame time data sent from the transmitting side node is added with fixed time data, which will be described later, by the offset adding unit 108 and input to the comparator 109. On the other hand, time data obtained from the cycle time register 112 is also input to the comparator 109. The comparator 109 outputs a pulse when the values of these two input data match. Note that the control of the offset adding unit 108 and the comparator 109 is performed by the control unit 110.
[0029]
The flow of time data in the communication apparatus shown in FIG. 1 will be described with reference to FIG. In FIG. 2, the time axis 201 indicates the time lapse of the value of the cycle time register 112 of the sender side node of packet data, and the time axis 202 indicates the time lapse of the value of the cycle time register 112 of the receiver side node. Both are set to substantially the same value in accordance with the IEEE 1394 protocol.
[0030]
First, it is assumed that when the cycle time is 203, a node on the sender side sends data every frame. It is assumed that the value of the hourly data per frame at this time is the value of the cycle time at 203. Assuming that time 204 is spent for data transmission, the frame-by-frame data arrives at the receiver node at the time 205.
[0031]
The receiver side node adds the preset offset data 207 to the transmitted frame time data value 206 to obtain a time data value 208 to be compared. Then, the time data value 208 calculated in this way is compared with the value of the cycle time 202 of the receiver side node, and a pulse is output when the two values match. Alternatively, it detects that the value of the cycle time 202 has changed from a value smaller than the value 208 of the time data to be compared to a value larger than the value 208 of the time data to be compared, and outputs a pulse. That is, the pulse is generated when the time indicated by the value of the cycle time 202 reaches 209 (= 208).
[0032]
Here, if the value of the offset data 207 is set to a value sufficiently longer than the time 204 spent for data transmission, the time spent for transmission changes, and the arrival time 205 of the packet at the node on the receiver side changes. Even if there is a variation, it is possible to accurately obtain the frame period pulse 111 of the image at the sender side node from the packet data written by the sender side node as the hourly frame data.
[0033]
As described above, in the first embodiment of the present invention, the value of the time data obtained by adding a predetermined offset to the time data of one frame unit generated on the transmission side is the value of the cycle timer on the reception side. A pulse is generated by detecting the coincidence or more. Therefore, on the receiving side, pulses can be easily generated at a cycle of once per frame without being affected by variations in transmission time. As a result, a synchronization signal for frame timing can be easily supplied to a device such as a digital VTR to which the communication apparatus of the present embodiment is connected or has a function capable of obtaining the same effect as the present embodiment. can do.
[0034]
(Second Embodiment)
FIG. 3 shows a configuration example of a communication apparatus according to the second embodiment of the present invention. In FIG. 3, those given the same reference numerals as those shown in FIG. 1 have the same functions and perform the same operations, and thus detailed description thereof will be omitted.
[0035]
In the second embodiment, offset data is not added (added) to the frame-by-frame time data from the sender side node detected by the time data detection unit 107, but the cycle time register 112 of the receiver side node. The offset adding unit 308 adds (subtracts) the offset data to the more output time data. In this case, the time data detection unit 107 and the offset addition unit 308 are controlled by the control unit 310.
[0036]
That is, in the second embodiment, the hourly frame data transmitted from the sender side node is input to the comparator 109 as it is. On the other hand, the time data obtained from the cycle time register 112 of the receiver side node is subtracted with fixed time data, which will be described later, by the offset adding unit 308 and input to the comparator 109. The comparator 109 outputs a pulse when the values of these two input data match.
[0037]
The flow of time data in the communication apparatus according to the second embodiment shown in FIG. 3 will be described with reference to FIG. In FIG. 4, the time axis 401 indicates the time passage of the value of the cycle time register 112 of the sender side node, and the time axis 402 indicates the time passage of the value of the cycle time register 112 of the receiver side node. Both are set to substantially the same value in accordance with the IEEE 1394 protocol.
[0038]
First, it is assumed that when the cycle time is 403, the node on the sender side sends data per frame. It is assumed that the value of hourly frame data at this time is the value of the cycle time at 403. Assuming that time 404 is spent on data transmission, the frame-by-frame data arrives at the receiver node at time 405.
[0039]
At the receiver side node, the preset offset data 407 is subtracted from the value of the cycle time register 112 represented by the time axis 402 to obtain a new time axis 410. Then, the value of the hourly frame data 406 sent from the sender side node is compared with the value of the new time axis 410, and a pulse is output when the two values match. Alternatively, it is detected that the value of the new time axis 410 has changed from a value smaller than the frame-per-hour data 406 written in the transmission packet to a value greater than the frame-per-hour data 406, and a pulse is output. That is, a pulse is generated when the cycle time indicated by the new value on the time axis 410 reaches 409 (= 403).
[0040]
Here, if the value of the offset data 407 is set to a value that is sufficiently longer than the time 404 spent for data transmission, the time spent for transmission changes, and the arrival time 405 of the packet at the receiver side node changes. Even if there is a variation, it is possible to accurately obtain the frame period pulse 111 of the image at the sender side node from the packet data written by the sender side node as the hourly frame data.
[0041]
As described above, in the second embodiment of the present invention, the time data of one frame unit generated on the transmission side is received on the reception side, and a predetermined offset is set from the value of the cycle timer on the reception side at that time. A pulse is generated by detecting that the value of the new cycle timer obtained by subtraction matches or exceeds the time data. Therefore, on the receiving side, pulses can be easily generated at a cycle of once per frame without being affected by variations in transmission time. As a result, a synchronization signal for frame timing can be easily supplied to a device such as a digital VTR to which the communication apparatus of the present embodiment is connected or has a function capable of obtaining the same effect as the present embodiment. can do.
[0042]
In the embodiment of the present invention, the time data received on the receiving side is described as time data generated in units of one frame on the transmitting side. However, for example, it is generated in units of one field or other synchronization timing. It may be time data.
[0043]
In addition, this invention can be implemented in various forms, without deviating from the mind or its main characteristics. For example, in the present embodiment, a system configured using a serial bus conforming to IEEE 1394-1995 has been described. However, the present invention can also be applied to a system having the same function as the system. Therefore, the above-mentioned embodiment is only an illustration in all points, and should not be interpreted limitedly.
[0044]
【The invention's effect】
According to the present invention, a synchronization signal for a frame can be easily generated on the receiving side.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a communication device according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an operation example of the communication apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of a communication apparatus according to a second embodiment of the present invention.
FIG. 4 is a diagram illustrating an operation example of a communication apparatus according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating a configuration of a conventional communication apparatus.
FIG. 6 is a diagram illustrating an operation example of a conventional communication apparatus.
[Explanation of symbols]
107 Time data detection unit 108 Offset addition unit 109 Comparator 110 Control unit 111 Frame pulse 112 Cycle time register 308 Offset addition unit 310 Control unit

Claims (2)

Time data detecting means for detecting time data from the received packet;
A cycle time register defined in IEEE 1394-1995;
Subtracting means for subtracting predetermined time data from the value of the cycle time register;
It has pulse generation means for generating a pulse corresponding to a frame period of image data using the time data output from the subtraction means and the time data output from the time data detection means. Communication device.   The communication apparatus according to claim 1, wherein the time data detected from the received packet is generated for each frame.

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