JP5343573B2 - How to send image data - Google Patents

Description

  The present invention relates to a communication system for transmitting image data between communication terminals or between a communication terminal and a host computer via various lines, and more particularly to a method for transmitting image data in accordance with the communication speed of the line.

  For communication of image data between the communication terminal and the host station, a communication system that can be transmitted via various lines (eg PHS, FOMA, satellite mobile phone, MCA wireless, serial, Ethernet (registered trademark)) The transmission route can be changed.

  As shown in FIG. 3, the basic transmission process sequentially creates image data (n-1 to n-6) to be transmitted by the CPU on the transmission side (S1), and generates these as communication protocols. Are sequentially transferred to the transmission buffer of the communication device (S2). In the communication protocol, the data is transferred to the buffer of the communication device (S3), the communication device sends the data on the line, and this data is received by the partner device (S4). ).

  In such a transmission / reception process, for example, when still images are continuously transmitted, the image data is not a fixed capacity (number of bytes), but depends on the image size (vertical × horizontal number of pixels). The amount of data. By sending this periodically, a pseudo moving image can be obtained. This application is often used like a surveillance camera and requires real-time performance.

When image data is continuously transmitted in the transmission / reception processing shown in FIG. 3, among the images to be transmitted (n-1 to n-6), the first image (n-6) is sequentially transmitted to the transmission buffer and transmitted. The data is transferred from the buffer to the communication device buffer and sent to the line. At this time, in many cases, the limit of the communication speed of the line type is a bottleneck in the image update.

  For example, in remote image monitoring, when camera control is performed by looking at a transmitted image, the image monitor starts and ends camera control based on the transmitted image. However, the actual start and end of control are delayed by the amount of delay of the image. If the amount of delay increases, the response feels bad, and camera control in a short time becomes difficult. Regarding data loss, if part of image data is lost, image reproduction is disturbed, and if data loss occurs for a long time, it becomes a serious problem in an online monitoring system.

  As a communication method to ensure real-time performance against the limitation of communication speed depending on the type of line, a plurality of node devices are installed in a transmission line configured in a loop, and this transmission line is separated by a preset time slot. A data communication structure in which node device information is allocated to unit time slots, and node devices sequentially receive and transmit data frames, and unit time slots are assigned to one terminal as necessary. A system in which a plurality of systems are assigned has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2001-186518

  In the communication method of Patent Document 1, transmission data is divided and transmitted in separate data frames. The transmission of individual data frames is the same as in FIG. 3, and the limit of communication speed depending on the line type is image update. Bottleneck.

  Since the state in which the line efficiency is the best is the state in which data is constantly sent, the maximum update speed can be obtained by constantly sending more data than the communication speed.

  However, since this state is always “transmission amount to the transmission buffer> transmission amount to the line”, the transmission buffer and the communication buffer are full. Will occur. That is, in FIG. 3, the images n-4 to n-6 are delayed.

  Therefore, there is a problem that the delay increases or decreases depending on the line, and an image with lost real-time property is received.

  An object of the present invention is to provide an image data transmission method capable of minimizing the amount of image data staying in a transmission buffer while transmitting image data making the most of the bandwidth of a communication line.

  In order to solve the above problems, the present invention divides image data in an image data transmission source device and transfers it to a transmission buffer, and the image data transferred to the transmission buffer is connected from the transmission buffer via a communication line. Measures the transmission speed on the communication line from the time until transmission processing is performed toward the destination device, repeats measurement of the transmission speed while increasing the amount of data transferred to the transmission buffer, and transfers the data to the transmission buffer. The amount of transfer data is increased until the transmission speed with respect to the amount does not change, and is characterized by the following method.

(1) The image data transmission source device and the transmission destination device are connected by a communication line. The transmission source device transfers the image data to the transmission buffer, and the image data transferred to the transmission buffer is transmitted to the transmission destination device. In the image data transmission method to
The transmission source device is:
A process of transferring the partial image data divided from the image data to the transmission buffer;
Processing for measuring the transmission speed on the communication line from the time until the partial image data transferred to the transmission buffer is transmitted from the transmission buffer to the transmission destination device connected on the communication line;
The process of repeating the measurement of the transmission speed while increasing the transfer data amount of the partial image data transferred to the transmission buffer, and increasing the transfer data amount until the transmission speed for the transfer data amount to the transmission buffer does not change;
The method is characterized in that the image data is transmitted.

  (2) The transmission source apparatus performs the measurement of the transmission speed a plurality of times with the same transfer data amount, and sets the average value as the transmission speed.

  (3) The transmission source apparatus is characterized in that the transfer data amount is increased roughly at first, and then increased finely after the communication speed does not change.

  (4) The transmission source device increases the transfer data amount, and increases the transfer data amount only when the difference between the measurement value before the increase and the measurement value after the increase is a certain value or more.

  (5) The transmission source apparatus monitors the current data amount of the transmission buffer, and transfers the next image data to the transmission buffer by a predetermined amount when the data amount becomes a predetermined amount or less. Features.

  As described above, according to the present invention, the image data transmission source device divides the image data and transfers it to the transmission buffer, and the image data transferred to the transmission buffer is connected to the transmission buffer via the communication line. Measure the transmission speed on the communication line from the time until the transmission processing to the destination device, repeat the measurement of the transmission speed while increasing the amount of data transferred to the transmission buffer, and the amount of data transferred to the transmission buffer Since the amount of transfer data is increased until the transmission speed does not change, the amount of image data staying in the transmission buffer can be minimized while transmitting image data making the most of the bandwidth of the communication line.

In particular,
(1) Since the delay caused by staying in the buffer can be minimized while making the best use of the communication band, both the maximum image update speed and the minimum delay amount can be achieved.

  (2) Even when the type of communication line changes and the communication band changes, an optimal communication state can be obtained.

  (3) The transmission data amount can be increased or decreased by a simple method by setting the threshold value, and a more optimal data transfer rate can be obtained.

  (4) Communication efficiency and delay can be adjusted in real time according to the line status.

The block diagram of the communication terminal which shows embodiment of this invention. An example of continuous transmission processing of image data. Basic transmission processing procedure for image data.

(Embodiment 1)
FIG. 1 is a configuration diagram of a communication terminal showing an embodiment of the present invention. An arithmetic unit (CPU) 1 of a communication terminal having a computer configuration includes a ROM 2 that mainly stores a program, a RAM 3 that is used as a data processing buffer, an execution area of the program, a VIDEO input circuit 4, an I / O The OMC interface 5 and the PCMCIA interface 6 serving as an I / F for the communication card are connected by bus. A video camera 7 is connected to the VIDEO input device 4. Further, a communication card 8 is connected to the PCMCIA interface 6, and image data is transmitted or received by the communication card 8 to or from the other party via a public line network or the like.

  For example, image information photographed by the video camera 7 is taken into the RAM 3 via the VIDEO input circuit 4, and is connected to the public line network or various communication devices via the PCMCIA interface 6 by the FOMA, PHS, or serial communication card 8. Take the configuration sent to.

  As the buffer of image data used in each communication process, the CPU 1 allocates an area on the RAM 3 by a program built in the ROM 2, and as shown in the figure, as a transmission buffer 3A, a reception buffer 3B, an image buffer 3C, etc. used. The communication card 8 includes a transmission buffer 8A and a reception buffer 8B for image data transmitted and received via the transmission path.

  When the image data is continuously transmitted, the CPU 1 executes the following process shown in FIG.

  (S 11) Image data captured by the video camera 7 is taken in via the VIDEO input circuit 4.

  (S12) The captured image data is stored in the image buffer 3C on the RAM 3.

  (S13) A fixed amount of data (partial image data) is extracted from the image buffer 3C and transferred to the transmission buffer 3A managed by a communication protocol such as TCP / IP.

  (S14) The communication protocol transfers the partial image data in the transmission buffer 3A to the transmission buffer 8A. The partial image data in the transmission buffer 8A is transmitted to a reception buffer in a communication apparatus as a transmission destination through a public line network or the like.

  In the image data transmission processing (S11 to S14) described above, the image data is divided into a predetermined size and transmitted to the transmission buffer. That is, the image data captured by the CPU 1 is temporarily stored in the image buffer 3C in the RAM 3. The stored image data is divided, for example, for each transmission block size, and transferred to the transmission buffer 3A in order from the oldest in time series. At this time, the transmission process is realized by the CPU executing a communication protocol configured by a program such as TCP / IP. At that time, the communication protocol secures the protocol transmission buffer 3A on the RAM 3, and performs processing for sequentially transferring the data sent therein to the transmission buffer 8A of the communication card 8 (transmission device). Send.

  Here, the size when the image data is divided into a certain size and transferred to the transmission buffer will be described.

  For example, when transmitting using a communication device such as FOMA, PHS, satellite telephone, etc., as shown in FIG. 2, if the transmission block size is large, large data is stored in the transmission buffer 3A. Even if there are fluctuations or fluctuations in communication processing or transmission band, the transmission speed is averaged because the transmission time is long compared to the fluctuation time. Send).

  For this reason, if the transmission buffer is sufficiently large with respect to the size of the image data, the transmission process can be dedicated to the process of transmitting data, and the transmission bandwidth can be utilized effectively, thereby increasing the communication efficiency, The image update speed can be increased. However, since it always has a large amount of data that depends on the transmission buffer size, more past images are held in the buffer, eventually resulting in a delay of the buffer size and loss of real-time characteristics. To go.

  Conversely, if the transmission buffer size is made sufficiently small relative to the size of the image data, the delay will decrease, so real-time performance will be ensured, but the overhead processing amount due to the increase in the number of transmission processes will increase, and the bandwidth will be effective. As a result, the image update speed decreases.

  As described above, when the amount of data sent to the buffer cannot be appropriately adjusted according to the communication speed (bandwidth) that varies depending on the communication medium to be used, there arises a problem of loss of real time due to the image update speed or delay.

  Therefore, in this embodiment, a function for measuring the time from when the partial image data is transferred from the transmission buffer 3A to the transmission buffer 8A until it is transmitted to the counterpart device is provided, and the amount of transmission data to the transmission buffer 8A is set to 1. By doubling, doubling, and doubling, the transmission speed is obtained from the communication time for the data volume, and the transmission data volume is increased until the transmission speed does not change, thereby maximizing the bandwidth of the communication line. A transmission method that minimizes the amount of data that stays in the transmission buffer 8A while making full use of it.

  The procedure for measuring the communication speed will be specifically described.

  (1) The amount of data transferred to the transmission buffer is adjusted to a fixed amount α. Initially, this value α is set to an arbitrarily determined value.

  (2) First, the timer A is started and α is transmitted to the transmission buffer possessed by the communication protocol. The timer A can be easily realized by counting up the cleared counter at regular intervals.

  (3) The communication protocol extracts data from the transmission buffer and transmits it to the communication device buffer.

  (4) The transmission data is sequentially transmitted according to the communication band of the communication device, and the amount of data in the transmission buffer decreases accordingly. At this time, the data amount of the transmission buffer is managed by a register.

  (5) The program monitors the data amount of the transmission buffer by reading the register, and reads the value of timer A when all transmission is completed. This value is assumed to be t1.

(6) By repeating this, the transmission rate k can be calculated by the following equation. k (1) = α / t1
(7) Next, for example, the transmission speed when the value of timer A is measured as t2 when the transmission data amount to the transmission buffer is doubled by 2α is calculated by k (2) = 2 × α / t2. Is done.

  (8) Here, k (2) <k (1) indicates that there is a margin in the data communication band.

  (9) This is repeated, and the point at which the transmission speed does not increase even when the data amount is increased becomes the upper limit of the transmission speed of the line.

  In this way, data is always stored in the communication buffer, and image data can be transmitted taking full advantage of the bandwidth of the communication line, and the amount of image data remaining in the transmission buffer is minimized to minimize delay. Can be suppressed.

(Embodiment 2)
In this embodiment, the number of times of obtaining the transmission speed k with the same transfer data amount is performed a plurality of times, and the average value thereof is used as the transmission speed, thereby dealing with variations due to changes in the communication speed.

  For example, by repeating the calculation with the same transmission data amount three times, it becomes possible to obtain a transmission speed that is less affected by the change in communication speed over time.

(Embodiment 3)
In the present embodiment, the transmission data amount when determining the transmission speed k is not changed by an integral multiple (such as 2), but is adjusted by a variation having a fractional part such as 1.2 times. The range can be made finer, and a more accurate communication speed can be obtained. Thus, it is possible to set a transmission data amount that can obtain the shortest delay and update time.

(Embodiment 4)
In the third embodiment, fine adjustment is possible, but the adjustment time becomes longer because the number of changes in the data amount increases until the adjustment is completed.

  In order to eliminate this inconvenience, in the present embodiment, first, adjustment is performed with a large change amount as in the first embodiment, and when there is no change, the previous data amount is used as a reference as in the third embodiment. Make fine adjustments to achieve a small increase. Thereby, a short adjustment time can be obtained.

(Embodiment 5)
In this embodiment, the amount of transfer data is increased only when the ratio k (n) / k (n-1) of the transmission speed k is equal to or greater than a certain value, and the amount of calculation consumed for adjustment is reduced. .

  For example, by setting {k (2) / k (1)}> 1.2 and ignoring changes below the threshold, the number of adjustments due to variation can be reduced.

(Embodiment 6)
In the present embodiment, monitoring is performed by reading the current data amount in the transmission buffer, and when the amount falls below a certain amount (for example, 20% of α), the next image data is stored in the transmission buffer by a predetermined amount (for example, α). Make it forward. By repeating this, since there is always data in the transmission buffer, there is no time zone without data, and the bandwidth can be used effectively.

  For example, whenever the transmission data amount α falls below 20%, the value of the timer A is set to t and the timer A is restarted. This is repeated at all times during communication, and the previous value ta and the current value tb of the timer are compared. When ta> tb, it is determined that the bandwidth is widened and the value of α is increased, and when ta <tb, the bandwidth is narrowed. By determining that the value of α is small, it is possible to always select the optimum amount of transmission data according to the change in the bandwidth of the line.

1 CPU
2 ROM
3 RAM
4 VIDEO input circuit 5 IO interface 6 PCMCIA interface 7 video camera 8 communication card

Claims (4)

The image data transmission source device and the transmission destination device are connected by a communication line, the transmission source device transfers the image data to the transmission buffer, and the image data transferred to the transmission buffer is transmitted to the transmission destination device. In the sending method of
The transmission source device is:
A process of transferring the partial image data divided from the image data to the transmission buffer;
The time until said partial image data transferred to the transmission buffer are all transmission process to the destination device connected by a communication line from the transmission buffer, the process of measuring the transmission rate in the communication line,
The transmission while buffer increasing amount of transfer data of the partial image data to be transferred to repeatedly the measurement of the transmission velocity for transferring data amount after the increasing transmission rate does not change this repeat transmitted data amount after increasing the by performing up, a process of increasing the amount of data transferred,
The current amount of data in the transmission buffer is monitored, and when this amount of data becomes a certain amount or less , the next image data is transmitted by the increased amount of transferred data that is increased until the transmission speed does not change. Processing to transfer to the buffer;
A method of transmitting image data, characterized by transmitting image data.   2. The image data transmission method according to claim 1, wherein the transmission source device measures the transmission speed a plurality of times with the same transfer data amount, and sets the average value as the transmission speed. The transmission source device, the transfer data amount initially roughly increased, since the longer the communication speed is changed, an image according to claim 1, wherein the Yasu finely increasing the transfer data amount after the increasing How to send data. The transmission source device increases the transfer data amount, and increases the transfer data amount after the increase only when the difference between the measurement value before the increase and the measurement value after the increase is a certain value or more. The method of transmitting image data according to claim 1.

Images