JP2006332966A - Data transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the same bit rate as the time of receiving by simple processing, and at the same time, control a transmission packet rate to a desired mode by simple processing, when transmitting the data packets which are transmitted in a network according to a request, after they have been stored once. <P>SOLUTION: When receiving data packets transmitted via the network, a packet counter 42 removes data packets from a receiving buffer 41 counting the number of the data packets for every fixed period timing, records it to an accumulation device 22, and records the information of a data packet number in a packet count table 46. When transmitting the stored data packet to the network, a reader 44 reads out the necessary number of data packets from the accumulation device 22, according to setting information of a packet rate setting part 48 referring to the number information recorded in the counting table 46 for the fixed period timing, and a transmitter 47 transmits them to the network. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data transmission device that transmits encoded data packets via a network.

  For example, in a data transmission system for transmitting a video signal via a network, on the transmission side, for example, an analog video signal output from a camera is encoded into digital data, and the digital data is converted into a data packet so that it can be transmitted to the network. Send to the network. On the receiving side, the transmitted data packet is received, and the extracted digital data is decoded as an analog video signal that can be displayed on a monitor, for example.

  An example of a data recording / reproducing apparatus used in the data transmission system as described above will be shown. FIG. 8 is a block diagram showing a configuration example of a conventional data recording / reproducing apparatus. The data recording / reproducing apparatus 100 is provided between a transmission-side encoder and a reception-side decoder connected via a network, records a data packet transmitted from the encoder, and records the recorded data packet. , Transmit to the network so that the decoder can receive. The data recording / reproducing apparatus 100 looks like a decoder when viewed from the encoder, and looks like an encoder when viewed from the decoder.

  The data recording / reproducing apparatus 100 temporarily stores a data packet such as a video signal received via a network and bit rate data received together with the data packet, and reads and stores the data packet from the reception buffer 101. A recording unit 102 for recording in the device 111, a reading unit 103 for reading out data from the storage device 111 and storing it in the transmission buffer 104, and sequentially reading out the data stored in the transmission buffer 104 to output a data packet and detecting it A bit rate value detection unit 105 that also outputs bit rate data, an interval calculation setting unit 106 that calculates an interval for transmitting a data packet based on the bit rate data, and outputs the data packet and the bit rate data; In the calculation setting unit 106 And a sending unit 107 for transmitting data packets in order was intervals (e.g., see Patent Document 1).

  At this time, the encoder transmits a data packet such as a video signal and also transmits transmission bit rate data of the data packet. As a result, when transmitting a data packet of a video signal recorded in the storage device 111, it is possible to adjust an interval for transmitting the data packet by using the bit rate data received together with the received data packet. it can.

  FIG. 9 is a diagram showing a specific example of a packet transmission method during reproduction of a conventional data recording / reproducing apparatus. In this data recording / reproducing apparatus 100, the bit rate at the time of recording (at the time of reception) can be reproduced at the time of reproduction (at the time of transmission) by controlling the packet transmission interval. Therefore, the receiving side device that receives the transmitted data packet can accurately decode the data packet.

JP-A-8-191330

  In the conventional data recording / reproducing apparatus, when transmitting the accumulated data packet, the bit rate data is required to determine the transmission interval of the data packet. Therefore, the encoder generates the bit rate data and transmits it. A mechanism to do this is necessary, and versatility is reduced. Further, since it is necessary to calculate the time interval of the data packet and send it in accordance with the time interval, the processing becomes complicated. Further, when calculating the time interval of the data packet from the bit rate data, there is a possibility that an arithmetic rounding error may occur, and there is a possibility that it is shifted from the time axis when the data packet is received from the encoder.

  Furthermore, when trying to control the transmission packet rate of the data packet, it is necessary to calculate the transmission packet rate of the control target from the bit rate data and send the data packet in accordance with the time interval. Become.

  The present invention has been made in view of the above circumstances, and when receiving and accumulating data packets transmitted to the network and then transmitting them in response to a request, when received by simple processing; It is an object of the present invention to provide a data transmission apparatus that can reproduce the same bit rate and can control the transmission packet rate in a desired manner by simple processing.

  A data transmission apparatus according to the present invention includes a reception buffer that temporarily stores data packets received via a network, a timing generation unit that generates a timing signal having a fixed cycle timing, and a packet that stores the number information of the data packets. Number information storage means, storage means for storing the data packet, recording means for recording the data packet in the storage means, and reading the data packet from the reception buffer at each fixed cycle timing to the recording means A packet counting means for counting the number of the data packets received within the fixed period timing and outputting the number information of the data packets to the packet number information storing means; and the number of packets for each fixed period timing Data packet from information storage means The number of read data, a read means for reading out data packets from the storage means for the read number, or a number less than or equal to a predetermined value, and a predetermined number of data packets to be read at a constant cycle timing in the read means. Packet rate setting means for setting a value and sending means for sending the read data packet to the network.

  As a result, when the stored data packets are read out and transmitted to the network, the number of data packets to be transmitted can be controlled at fixed cycle timings based on the number information of the recorded data packets. Thus, it is possible to reproduce the same bit rate (transmission packet rate) as that received at the time of transmission. Further, the transmission packet rate can be controlled to a desired mode with simple processing, and transmission can be performed at an arbitrary transmission packet rate equal to or lower than a predetermined value, or transmission can be performed at a predetermined transmission packet rate.

  Further, the present invention is the above data transmission apparatus, wherein the packet number information storage means includes, as the number information of the data packets, processing period information relating to the fixed period timing and packet reception number information for each processing period. Are stored at least.

  Thereby, the process at the time of data packet transmission can be appropriately executed by a simpler process based on the processing cycle information, and the degree of freedom of the system can be increased.

  Also, the present invention is the data transmission apparatus described above, wherein the storage means records the data packets so that they can be individually read in packet units.

  This makes it possible to appropriately read out the stored data packets in response to a request when transmitting the data packets.

  According to the present invention, after receiving and accumulating data packets transmitted to the network, when transmitting data packets as requested, the same bit rate as when received by simple processing can be reproduced, It is possible to provide a data transmission apparatus capable of controlling the transmission packet rate to a desired mode with simple processing.

  In this embodiment, as an example of a data transmission apparatus, an encoded data packet transmitted via a network, for example, an RTP (Real-Time Transport Protocol) packet including digital data obtained by encoding a video signal in the MPEG format is received. An example of the configuration of an apparatus for temporarily storing the data packet and transmitting the data packet to the network in response to a request will be described.

  FIG. 1 is a block diagram showing a configuration of a data transmission system according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a data recording / reproducing system including a data recording / reproducing apparatus for data transmission on a network. The data transmission system 10 according to the present embodiment encodes an analog video signal captured by the camera 12 into digital data and transmits the digital data to the network 15, and decodes the digital data transmitted via the network 15. A decoder 13 for outputting to the monitor 14 is provided, and these encoder 11 and decoder 13 are connected to a network 15.

  In this data transmission system, the encoder 11 encodes an analog video signal output from the camera 12 into digital data, further packetizes the digital data so that it can be transmitted to the network 15, and transmits it as a data packet 16 to the network 15. Send. The decoder 13 receives the data packet transmitted from the network 15, decodes the extracted digital data as an analog video signal that can be displayed on the monitor 14, and outputs it to the monitor 14. As a result, the video transmitted over the network is displayed on the monitor 14.

  In the configuration shown in FIG. 1, a data recording / reproducing system 20 shown in FIG. The data packet recording / reproducing device 21 is connected to the network 15 to which the encoder 11 and the decoder 13 are connected. The data packet recording / reproducing device 21 receives the data packet transmitted by the encoder 11 and records it in a storage device 22 composed of a hard disk drive or the like. The recorded data packet is transmitted to the network 15 so that the decoder 13 can receive it. In the configuration of FIG. 2, the data packet recording / reproducing device 21 looks like the decoder 13 when viewed from the encoder 11 and looks like the encoder 11 when viewed from the decoder 13.

  FIG. 3 is a block diagram showing the configuration of the data packet recording / reproducing apparatus 21 according to this embodiment. The data packet recording / reproducing device 21 includes a reception buffer 41, a packet counting unit 42, a recording unit 43, a storage device 22, a reading unit 44, a clock generating unit 45, a packet count table 46, a sending unit 47, and a packet rate setting unit 48. Configured.

  The reception buffer 41 temporarily stores data packets such as video signals received via the network 15. The clock generation unit 45 corresponds to an example of a timing generation unit, and generates a clock having a constant cycle timing (for example, a cycle of 100 ms) in synchronization with the system clock of the device itself. The packet counting unit 42 corresponds to an example of a packet counting unit, reads a data packet from the reception buffer 41 and outputs the data packet to the recording unit 43 at a certain periodic timing notified from the clock generation unit 45, and the constant The number of data packets received within the cycle timing is counted, and the number information of data packets is recorded in a packet count table 46 corresponding to an example of a packet number information storage unit.

  The recording unit 43 corresponds to an example of a recording unit, and records the data packet received from the packet counting unit 42 in the storage device 22 corresponding to an example of a storage unit such as a hard disk drive. The packet rate setting unit 48 sets the packet rate of the data packet to be transmitted, and outputs this packet rate information to the reading unit 44. The reading unit 44 corresponds to an example of a reading unit. The reading unit 44 reads the number information of the data packets from the packet count table 46 at regular cycle timing notified from the clock generation unit 45, and uses the number information to read the packet. The number of data packets not exceeding the packet rate set by the rate setting unit 48 is read from the storage device 22. The sending unit 47 corresponds to an example of sending means, and transmits the data packet read by the reading unit 44 to the network 15.

  The operation of the data packet recording / reproducing apparatus 21 configured as described above will be described with reference to FIGS. FIG. 4 is a timing chart showing the flow of data packet processing at the time of reception (recording) in this embodiment, FIG. 5 is a diagram showing an example of a packet count table, and FIG. 6 is a diagram showing a packet data accumulation method. 7 is a diagram illustrating a packet transmission method at the time of transmission (reproduction) in the present embodiment.

  First, the data packet input to the reception buffer 41 will be described. This data packet is, for example, an RTP packet obtained by encoding a video signal by the MPEG method. The arrival timing of this RTP packet, for example, is not constant when encoding at the variable bit rate (VBR) when encoded by the encoder 11, for example, but even when encoded at a fixed bit rate (CBR) It may not be constant due to fluctuations due to delays. Therefore, as shown in FIG. 4A, the reception interval of data packets varies.

  Next, the timing for processing the data packet input to the reception buffer 41 is performed at regular intervals as shown in FIG. 4B according to the timing generated by the clock generation unit 45. As this clock generation method, for example, a method using a periodic interrupt of an operating system (OS) or a method using a hardware timer interrupt from the outside can be considered.

  At this fixed cycle timing, the data packets accumulated in the reception buffer are output to the recording unit 43 and the number of data packets is recorded in the packet count table 46. As shown in FIG. 5, the packet count table 46 includes header information 51 such as processing cycle information, and packet reception number information 52 for each processing cycle. In the example of FIG. 4, the packet count table 46 records n1 = 4, n2 = 5, n3 = 3,... From FIG. It is desirable to add header information 51 to the packet count table 46 as shown in FIG. Thereby, the information of the fixed cycle timing generated by the clock generation unit 45 at the time of data packet reception can be included in the header information 51 of the packet count table 46, and the processing at the time of data packet transmission can be executed more appropriately. In addition, the degree of freedom of the system can be expected to increase. Note that the information of the packet count table 46 may be recorded in the storage device 22.

  In addition, the recording unit 43 can individually read out the RTP packet data 61 one by one in units of packets as shown in FIG. 6 when recording transmission data in the storage device 22 in units of data packets, that is, RTP packets. Record with.

  Next, the operation when the data packet recorded in the storage device 22 as described above is transmitted to the network will be described with reference to FIG.

  First, at the time of recording (at the time of reception), it is assumed that the number of packets received in the processing period A is 4 and the number of packets received in the processing period B is 5 as shown in FIG. . When the recorded data is reproduced (at the time of transmission), four packets are transmitted at the timing of the processing cycle A as shown in FIG. Send packets.

  As described above, in this embodiment, the number of data packets recorded in the packet count table 46 can be read from the storage device 22 and transmitted every processing cycle generated by the clock generation unit 45. For this reason, since the clock generated by the own apparatus has the same timing during recording and during reproduction, the average bit rate when received can be reproduced during transmission. At this time, it is only necessary to follow a fixed cycle timing by the clock generation unit 45 of the device itself, so there is no need to synchronize the clock with the encoder or decoder. In particular, since the processing at the time of recording / reproduction only needs to count data packets, the amount of processing is small, and rounding error due to decimal arithmetic does not occur.

  In the present embodiment, the data rate is counted in the transmission process, so that the packet rate can be easily controlled. Therefore, the packet rate setting unit 48 can set the operation of the reading unit 44 to a plurality of operation modes. At this time, not only the reading operation for reproducing the packet rate at the time of recording as described above, but also a reading operation for reproducing at an arbitrary packet rate below a predetermined set value and a reading operation for reproducing at a predetermined packet rate. You can set the action.

  In the case of a read operation for reproducing at a packet rate equal to or lower than a predetermined set value, the packet rate set by the packet rate setting unit 48 is input to the read unit 44, and the clock generation unit is based on the packet rate in the read unit 44. The number of processing packets to be transmitted per unit processing cycle is obtained from 45 processing cycles. Then, the reading unit 44 reads from the storage device 21 a number of data packets whose number information recorded in the packet count table 46 is equal to or less than the number of processing packets for each processing cycle, and sends it out from the sending unit 47. At this time, the number information recorded in the packet count table 46 in each processing cycle exceeds the number of processing packets is taken over in the next processing cycle. This processing enables transmission at an arbitrary packet rate equal to or lower than a predetermined value, that is, at a variable packet rate up to an arbitrary packet rate.

  In the case of a read operation for reproducing at a predetermined packet rate, the read unit 44 transmits from the processing cycle of the clock generation unit 45 per unit processing cycle based on the packet rate set by the packet rate setting unit 48 as described above. Obtain the number of processed packets. Then, the reading unit 44 reads data packets corresponding to the number of processing packets from the number information recorded in the packet count table 46 for each processing cycle, and sends the data packets from the storage unit 21. By this processing, it becomes possible to transmit at an arbitrarily designated transmission packet rate.

  Here, since the decoder 13 is originally arranged via the encoder 11 and the network 15, a countermeasure against the influence of fluctuation in the network 15 is generally taken. In particular, it is designed so that there is no problem even if a plurality of packets are temporarily received in a burst form. That is, even if a plurality of data packets are transmitted together at the timing generated by the clock generation unit 45, there is no influence.

  As described above, in this embodiment, in the data recording / reproducing apparatus for recording / reproducing data packets such as video signals transmitted to the network on the data transmission system, at the time of recording, the data packets are read at regular cycle timings. In addition to recording, the number of data packets received within the fixed cycle timing is counted and the number information is recorded. As a result, when a data packet is recorded and stored and then transmitted and reproduced as requested, the same bit rate (transmission packet rate) as when received by simple processing can be reproduced. In addition, when the stored data packets are sent out and played back according to the request, it is transmitted by a simple process such as transmission at an arbitrary transmission packet rate below a predetermined value or transmission at a predetermined transmission packet rate. The packet rate can be controlled in a desired manner.

  The present invention can reproduce the same bit rate as when received by a simple process when transmitting a data packet in response to a request after receiving and accumulating the data packet transmitted to the network. This has the effect of allowing the rate to be controlled in a desired manner with simple processing, and is useful for a data transmission apparatus that transmits encoded data packets via a network.

The block diagram which shows the structure of the data transmission system which concerns on embodiment of this invention 1 is a block diagram showing a configuration of a data recording / reproducing system including a data recording / reproducing apparatus according to an embodiment of the present invention. A block diagram showing a configuration of a data packet recording / reproducing apparatus according to the present embodiment Timing chart showing the flow of data packet processing during reception (recording) in this embodiment The figure which shows an example of the packet count table in this embodiment The figure which shows the accumulation | storage method of the packet data in this embodiment The figure which shows the packet transmission method at the time of transmission (reproduction | regeneration) in this embodiment Block diagram showing a configuration example of a conventional data recording / reproducing apparatus The figure which shows the specific example of the packet transmission method at the time of reproduction | regeneration of the conventional data recording / reproducing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Data transmission system 11 Encoder 12 Camera 13 Decoder 14 Monitor 15 Network 16 Data packet 20 Data recording / reproduction system 21 Data packet recording / reproduction apparatus 22 Storage apparatus 41 Reception buffer 42 Packet count part 43 Recording part 44 Reading part 45 Clock generation part 46 Packet Count table 47 Transmission unit 48 Packet rate setting unit 51 Header information 52 Number of received packets 61 RTP packet data

Claims (3)

A receive buffer for temporarily storing data packets received over the network;
Timing generating means for generating a timing signal having a constant cycle timing;
Packet number information storage means for storing the number information of the data packets;
Storage means for storing the data packet;
Recording means for recording the data packet in the storage means;
The data packet is read from the reception buffer at each fixed cycle timing and output to the recording means, and the number of the data packets received within the fixed cycle timing is counted to obtain the number information of the data packets. Packet counting means for outputting to the information storage means;
Read means for reading the number of data packets from the packet number information storage means at each fixed cycle timing, and reading means for reading the data packets from the storage means, the number of read, or a number less than a predetermined value or a predetermined number;
A packet rate setting means for setting a predetermined value of the number of data packets to be read at a constant cycle timing in the reading means;
Sending means for sending the read data packet to the network;
A data transmission device comprising: The data transmission device according to claim 1,
The packet number information storage means stores at least processing cycle information relating to the fixed cycle timing and packet reception number information for each processing cycle as the number information of the data packets. The data transmission device according to claim 1 or 2,
The storage means records the data packets so that the data packets can be individually read in units of packets.

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