JP5168314B2 - COMMUNICATION DEVICE, COMMUNICATION METHOD, COMMUNICATION PROGRAM - Google Patents

Description

  The present invention relates to a communication device, a communication method, and a communication program that change the resolution of image data based on the amount of change in the available bandwidth of the network when transmitting image data via a network.

  When a communication device transmits and receives image data such as a TV conference in real time via a network such as the Internet, an image is transmitted at a transmission rate suitable for a bandwidth (bandwidth: Available Bandwidth) in order to stably transmit the image data. You need to send data. The bandwidth that can be used by the communication apparatus varies depending on the situation such as the region, the provider, and the time zone. Therefore, in order to stably transmit image data, a communication device that transmits image data needs to transmit image data with a data amount that matches the bandwidth of the network.

  For example, an invention described in Patent Document 1 has been proposed as an imaging apparatus that transmits image data with a data amount that matches a network bandwidth. In the imaging apparatus described in Patent Document 1, the resolution is sequentially reduced to create a plurality of reduced images. For the reduced image with the lowest resolution, the image data is encoded and output, and for the other reduced images and the original image, the difference data from the predicted image data of the reduced image of the previous stage is encoded. The number of stages is switched according to the bandwidth available for transmission.

JP 2006-108869 A

  However, the invention described in Patent Document 1 has a problem that the processing load on the image processing computer increases because the resolution is reduced in stages and a plurality of reduced images are created. In addition, since the usable bandwidth of the network constantly varies according to the amount of data flowing through the network, it is necessary to change the resolution of the image data to be transmitted based on the variation amount of the usable bandwidth of the network. However, in the invention described in Patent Document 1, wasteful processing is performed because images of several kinds of resolutions are always generated. In addition, when changing the resolution of the original image, a certain amount of time is required to make the change, and thus it is not possible to flexibly cope with a change in the bandwidth. Therefore, unless an appropriate method is selected, it takes time to change the resolution of the image data and there is a problem that the processing load becomes heavy.

  The present invention has been made to solve the above-described problem, and can provide a communication device, a communication method, and a communication method that can change the resolution of image data in a method that matches the amount of change in the available bandwidth of the network. An object is to provide a communication program.

  A communication device according to a first aspect of the present invention is a communication device capable of transmitting image data to another communication device via a network, and has an image generation function having a resolution conversion processing function for converting the resolution of the generated image data Means, converted image creation means for creating image data by reducing or enlarging the image data generated by the image generation means, communication bandwidth measurement means for measuring the available bandwidth of the network, and communication bandwidth measurement means A fluctuation amount calculating unit that calculates a fluctuation amount of the usable bandwidth measured by the method, a resolution of image data generated by the image generation unit based on the fluctuation amount calculated by the fluctuation amount calculating unit, and the converted image Resolution changing means for changing at least one of the resolutions of the image data converted by the creating means, and the resolution changed by the resolution changing means The image data encoding, and an output means for outputting to the other communication apparatus via the network.

  In this communication apparatus, at least one of the resolution of the image data generated by the image generation unit and the resolution of the image data converted by the converted image generation unit based on the fluctuation amount of the usable bandwidth of the network calculated by the fluctuation amount calculation unit. Therefore, at least one of the resolutions of the image generation unit and the converted image generation unit can be switched according to the fluctuation amount of the usable bandwidth of the network. Therefore, it is possible to prevent a loss of time and a burden of processing due to a change in resolution from becoming heavy.

  Further, when the fluctuation amount calculated by the fluctuation amount calculation means is within a predetermined range, the resolution changing means may change the resolution of the image data generated by the image generation means. When the amount of change in the available bandwidth of the network is small, the resolution is not changed frequently. Therefore, the resolution of the image data generated by the image generation means that takes a long time to change the resolution but does not impose a heavy processing burden Can be changed.

  Further, when the fluctuation amount calculated by the fluctuation amount calculation means is not within a predetermined range, the resolution changing means may change the resolution of the image data converted by the converted image creating means. good. When the amount of change in the usable bandwidth of the network is large, the resolution is frequently changed. Therefore, it is possible to change the resolution of the image data converted by the converted image creating means that does not take time to change the resolution.

  A communication method according to a second aspect of the present invention is a communication method for performing communication by changing the resolution of the image data, which is performed in an apparatus for generating image data transmitted via a network. An image generation process capable of resolution conversion processing for converting resolution, a converted image generation process for generating image data by reducing or enlarging the image data generated in the image generation process, and measuring the usable bandwidth of the network A communication bandwidth measuring step; a fluctuation amount calculating step of calculating a fluctuation amount of the usable bandwidth measured by the communication bandwidth measuring step; and the image generating step based on the fluctuation amount calculated by the fluctuation amount calculating step. Resolution change for changing at least one of resolution of generated image data and resolution of image data converted in the converted image creating step Degree and the coded image data of the changed resolution by the resolution changing step, and an output step of outputting to the other communication apparatus via the network.

  According to the communication method according to the second aspect, at least one resolution of the image data generated in the image generation step and the image data converted in the converted image generation step is switched according to the fluctuation amount of the usable bandwidth of the network. be able to. Therefore, it is possible to prevent a loss of time and a burden of processing due to a change in resolution from becoming heavy.

  A communication program according to a third aspect of the present invention includes an image generation process capable of resolution conversion processing for converting the resolution of image data to be generated, and image data generated by reducing or expanding the image data generated in the image generation process. A converted image creating step for creating a network, a communication band measuring step for measuring an available bandwidth of the network, a fluctuation amount calculating step for calculating a fluctuation amount of the available bandwidth measured by the communication band measuring step, A resolution changing step of changing at least one of the resolution of the image data generated in the image generation step and the resolution of the image data converted in the converted image creation step based on the amount of change calculated in the variation amount calculating step; The image data having the resolution changed in the resolution changing step is encoded and output to the other communication device via the network. Characterized in that to execute a power step the image data into transmittable computer to other communication devices via the network.

  According to the communication program according to the third aspect, at least one resolution of the image data generated in the image generation step and the image data converted in the conversion image generation step is switched according to the fluctuation amount of the usable bandwidth of the network. be able to. Therefore, it is possible to prevent a loss of time and a burden of computer processing due to a change in resolution from becoming heavy.

It is a functional block diagram of the present invention. 1 is a block diagram showing an electrical configuration of a video conference system 100 and a communication device 1. FIG. 3 is a schematic diagram of a storage area of a hard disk drive (HDD) 13. FIG. It is a schematic diagram which shows an example of the resolution change table. It is a schematic diagram which shows an example of the resolution change table of a 1st specific example. It is a graph which shows distribution of the measurement result of the zone of the 1st example. It is a schematic diagram which shows an example of the resolution change table of a 2nd specific example. It is a graph which shows distribution of the measurement result of the zone of the 2nd example. It is a schematic diagram which shows an example of the resolution change table of a 3rd specific example. It is a graph which shows distribution of the measurement result of the zone of the 3rd example. 3 is a flowchart of main processing executed by a CPU 10 of the communication device 1. 4 is a flowchart of a subroutine of bandwidth calculation processing executed by the CPU 10 of the communication device 1. 4 is a flowchart of a resolution change process subroutine executed by the CPU 10 of the communication apparatus 1. 4 is a flowchart of a subroutine for resolution change destination switching processing executed by the CPU 10 of the communication device 1. It is a schematic diagram which shows an example of the resolution change table. It is a graph which shows the sampling condition of the zone | band in the case of the connection of multiple bases.

  Hereinafter, functional blocks of the communication apparatus 1 as an embodiment embodying the communication apparatus of the present invention will be described. As shown in FIG. 1, the communication device 1 is connected to an image generation unit 2 that generates original image data. Further, the communication device 1 is provided with a bandwidth control unit 3 that measures the usable bandwidth of the network and calculates the fluctuation amount of the measured usable bandwidth, and the communication device 1 includes the bandwidth control unit 3. Are provided with a switch unit 4 that can be switched by the control from, and a converted image creation unit 5 that is connected to the switch unit 4 and reduces or enlarges image data. The communication device 1 is also provided with an encoding unit 6 that encodes the image data generated by the image generation unit 2 or the image data generated by the converted image generation unit 5.

  Next, with reference to FIG. 2, the video conference system 100 provided with the communication apparatus 1 as an embodiment that further embodies the communication apparatus 1 will be described with reference to the drawings. The drawings to be referred to are used for explaining technical features that can be adopted by the present invention. The configuration of the apparatus, the flowcharts of various processes, and the like described in the drawings are not intended to be limited to these, but are merely illustrative examples.

  First, the configuration of the video conference system 100 will be described with reference to FIG. The video conference system 100 includes at least two communication devices 1. The communication device 1 is connected to another communication device 1 via the network 8. The communication device 1 communicates various data with other communication devices 1.

  The video conference system 100 of the present embodiment is a system for users at a plurality of bases to hold a video conference. Each communication device 1 packetizes image data and audio data and transmits / receives them to / from each other, thereby sharing video and audio from a plurality of locations. The communication device 1 may be any device that can execute data communication via the network 8. Specifically, it may be a dedicated video conference terminal arranged at each site for performing a video conference, or may be a personal computer or the like that performs various information processing.

  In the communication device 1 of the present embodiment, a bandwidth that can be used with the communication device 1 that is a communication partner (hereinafter, referred to as an available bandwidth) is measured, and corresponds to the measured variation in the available bandwidth. Thus, at least one of the resolution of the image generated by the camera 33 as the image generation unit 2 or the resolution of the image reduced or enlarged by the CPU 10 functioning as the converted image generation unit 5 is changed, Image data is sent to the other party. Hereinafter, the communication apparatus 1 of the present embodiment will be described in detail.

  First, the electrical configuration of the communication device 1 will be described with reference to FIG. The communication device 1 includes a CPU 10 that controls the communication device 1. A ROM 11, a RAM 12, a hard disk drive (hereinafter referred to as “HDD”) 13, and an input / output interface 19 are connected to the CPU 10 via a bus 18. The CPU 10 functions as the switch unit 4, the converted image creation unit 5, the encoding unit 6, and the band control unit 3 illustrated in FIG. 1.

  The ROM 11 stores a program for operating the communication device 1, an initial value, and the like. The RAM 12 temporarily stores various information used in the control program. The HDD 13 is a non-volatile storage device that stores various types of information such as a control program. Instead of the HDD, a storage device such as an SSD (Solid State Drive), an EEPROM, or a memory card may be used.

  Connected to the input / output interface 19 are a microphone 31 for inputting sound, a speaker 32 for outputting sound, a camera 33 for capturing images, a display device 34 for displaying images, an operation unit 25, and an external communication I / F 26. Yes. The operation unit 25 is used for a user to input various instructions to the communication device 1. The external communication I / F 26 connects the communication device 1 to the network 8.

  Next, various storage areas of the HDD 13 will be described with reference to FIG. The HDD 13 is provided with a program storage area 131, a resolution change table storage area 132, a base registration storage area 133, a band storage area 134, an average and standard deviation storage area 135, and the like. The program storage area 131 stores the communication program of the present invention. The resolution change table table storage area 132 stores resolution change tables 132A to 132E, which are correspondence tables between the available communication band of the network and the resolution in that band. In the base registration storage area 133, data of the partner base of communication is stored. The bandwidth storage area 134 stores the measured bandwidth. The average and standard deviation storage area 135 stores the calculated average of band, standard deviation, and update flag.

  As shown in FIG. 2, the communication device 1 is connected to another communication device 1 via a network 8. The communication device 1 communicates various data with other communication devices 1. The image generation unit 2 and the camera 33 correspond to the image generation unit, and the converted image generation unit 5 and the CPU 10 that functions as the conversion image generation unit 5 by executing a program to be described later correspond to the conversion image generation unit. The CPU 10 that functions as the bandwidth control unit 3 by executing the bandwidth control unit 3 and a program to be described later corresponds to a communication bandwidth measurement unit, a fluctuation amount calculation unit, and a resolution change unit. Further, the CPU 10 that functions as the encoding unit 6 by executing the encoding unit 6 and a program to be described later corresponds to an output unit.

  In the video conference system 100, each communication device 1 packetizes image data and audio data, and transmits and receives the data, while measuring a usable bandwidth with the communication device 1 of the communication partner. When a packet is transmitted at a transmission rate that exceeds the usable bandwidth, packet loss, transmission delay, and the like occur. On the other hand, if the transmission rate is too low, the bandwidth cannot be fully utilized and the efficiency is poor. Accordingly, each communication device 1 controls the transmission rate according to the measured bandwidth. Here, the “usable bandwidth” refers to the maximum transmission rate at which the receiving communication device 1 can receive data at a transmission rate substantially equal to the transmission rate of data transmitted by the transmitting communication device 1. In order to compare the bandwidth and the transmission speed between the communication apparatuses 1, the bandwidth is represented by a transmission path capacity (kbps).

  Next, an example of the resolution change table 132A will be described with reference to FIG. In the resolution change table 132A, a bandwidth (transmission path capacity (kbps)) that can be used with a communication apparatus 1 that is a predetermined communication partner, and a resolution that indicates the size of image data to be transmitted in that band ( (The number of dots in the horizontal direction × the number of dots in the vertical direction) is stored. This value is determined by calculation or experiment. In the case of calculation, since the time required for communication is obtained by dividing the number of dots in the horizontal direction × the number of dots in the vertical direction by the bandwidth (kbps), it may be determined so as to satisfy the required communication time. Further, in the case of an experiment, it is only necessary to perform a measurement experiment of a usable bandwidth among a plurality of communication apparatuses 1 in advance and determine the resolution of image data that does not cause packet loss, transmission delay, and the like.

  Next, the measurement principle of the band used in this embodiment will be described. In the video conference system 100, the communication device 1 that transmits data (hereinafter referred to as “transmitting device”) packetizes the data into a plurality of packets. The transmission device transmits a plurality of packets continuously to another communication device 1 (hereinafter referred to as “reception device”) via the network 8. If the transmission rate (unit: bps) at the time of transmitting a packet is equal to or less than the bandwidth (unit: bps) that can be used between the transmission device and the reception device, the packet does not jam. In this case, the interval (reception interval) at which the reception device receives a plurality of packets transmitted by the transmission device is theoretically the same as the transmission interval. On the other hand, if the transmission rate is higher than the bandwidth, the packet is congested and the reception interval is longer than the transmission interval.

When measuring the bandwidth, the transmission device transmits a plurality of packets while gradually increasing or decreasing the transmission interval. The transmission rate when a packet is transmitted is given by the following equation (1)
Transmission rate (bps) = packet size (bit) / time interval between previous packet transmission and current packet transmission (s) (1)
Is required. When a plurality of packets are transmitted while gradually increasing the transmission interval, the reception interval becomes longer than the transmission interval while the transmission rate is higher than the bandwidth. However, if the transmission interval becomes longer and the transmission speed becomes equal to or less than the bandwidth, the reception interval and the transmission interval become the same. Therefore, the transmission rate at the time when the value of “reception interval−transmission interval” changes can be measured as a band. The band measurement principle is not limited to the above method, and other band measurement methods may be used. For example, a method based on packet delay or delay fluctuation may be used. Specifically, the delay time of the packet is measured, and if the delay time increases, it is determined that the traffic is congested, and the bandwidth is considered to be narrower than the current one. For example, a method of determining a band by a relative comparison from the current state in which it is assumed that is wider than the current state may be used.

  Next, the principle of the resolution changing process according to the present embodiment will be described with reference to FIGS. First, as a first specific example, a case where the resolution of an image generated by the image generation unit 2 shown in FIG. 1 is changed will be described. In this case, the resolution format of the image data generated and output by the image generation unit 2 (in the embodiment shown in FIG. 2, the camera 33) is changed. In the digital camera and digital video camera used for the camera 33, the resolution of the image to be output can be switched. This change in the resolution of the image data output from the camera 33 takes time for switching the format of the camera 33, etc. Therefore, when the fluctuation range of the network usable communication band is large, the image data output from the camera 33 is changed. Changes in resolution are often required and are time consuming and unsuitable. Therefore, in the first specific example, when the fluctuation of the band is within a predetermined range, the resolution of the image data output from the camera 33 is changed.

First, the bandwidth control unit 3 measures and samples the available bandwidth of the network 8.
In this embodiment, the CPU 10 that measures the available bandwidth of the network 8 and performs sampling processing corresponds to the bandwidth controller 3. Next, a standard deviation is obtained from the sampled data. Here, an example of the resolution change table 132B will be described with reference to FIG. When the band is br, the resolution of the image data generated and output by the camera 33 is the number of horizontal dots w, and the number of vertical dots is h, the resolution is w (0) × when the band is br (0). When h (0), band: br (i-1), resolution: w (i-1) × h (i-1), when band: br (i), resolution: w (i) × h ( i) When the band is br (n), the resolution is w (n) × h (n). A range from br (i) to br (i-1) is a minimum range in which a band can be set.

  Here, when the standard deviation of the data of the available bandwidth of the network 8 measured and sampled is σ, as shown in FIG. 6, the data of the available bandwidth of the network 8 is normally distributed, and br (i) When> (average ± 2σ)> br (i−1), the amount of fluctuation of the band is small, so the resolution of the image generation unit 2 (camera 33) is set to w (i−1) × h (i−1). The image data output from the image generation unit 2 (camera 33) is directly input to the encoding unit 6 without being reduced or enlarged. As the encoding unit 6, the CPU 10 that performs software encoding processing corresponds to the encoding unit 6 in the communication device 1 of the present embodiment. Here, “average ± 2σ” is used because, in the case of a normal distribution, 95.44% of the data of the available bandwidth of the sampled network 8 falls within the range of “average ± 2σ”.

  Next, a case where the resolution of the image data created by the converted image creation unit 5 shown in FIG. 1 is changed will be described as a second specific example of the resolution changing process of the present embodiment. When the fluctuation range of the usable communication band of the network is large, the resolution changing process of the second specific example is performed. In this case, the format of the resolution of the image data created and output by the converted image creation unit 5 (CPU 10 that reduces or enlarges the image data in the embodiment shown in FIG. 2) is changed. As shown in FIG. 1, the image output from the image generation unit 2 (camera 33) is input to the converted image creation unit 5 via the switch unit 4. In the second specific example, the resolution of the image data converted by the converted image creation unit 5 is changed without changing the resolution of the image data output from the image generation unit 2 (camera 33).

  Also in the second specific example, first, the bandwidth control unit 3 measures and samples the available bandwidth of the network 8. Next, a standard deviation is obtained from the sampled data. Here, an example of the resolution change table 132C for changing the resolution of the image data converted by the converted image creation unit 5 will be described with reference to FIG. When the band is br, the resolution of the image data output from the converted image creation unit 5 is the number of horizontal dots w, and the number of vertical dots is h, the resolution is w (0) when the band is br (0). When xh (0), band: br (i-1), resolution: w (i-1) * h (i-1), when band: br (i), resolution: w (i) * h (I) When the band is br (n), the resolution is w (n) × h (n). A range from br (i) to br (i-1) is a minimum range in which a band can be set.

  Here, when the standard deviation of the data of the available bandwidth of the network 8 measured and sampled is σ, as shown in FIG. 8, the data of the available bandwidth of the network 8 is normally distributed, and br (i) > Average> br (i−1) and (average + 2σ)> br (i) or (average−2σ) <br (i−1), the amount of change in the available bandwidth of the network 8 Therefore, the resolution of the image generation unit 2 (camera 33) is not changed, and the image data is input from the image generation unit 2 (camera 33) to the converted image generation unit 5 without changing the resolution. When the usable bandwidth of the network 8 is measured by the bandwidth control unit 3 and the usable bandwidth is wider than br (i), an image with a resolution of w (i) × h (i) from the converted image creation unit 5 Is output. Further, when the usable bandwidth of the network 8 is measured by the bandwidth control unit 3 and the usable bandwidth is narrower than br (i), if br (m + 1)> (measured bandwidth)> br (m) Then, an image with a resolution of w (m) × h (m) is output from the converted image creation unit 5 (where “m” is a value smaller than “i”).

  Next, a third specific example of the resolution changing process according to the present embodiment will be described. In the third specific example, the resolution of the image generated by the image generation unit 2 shown in FIG. 1 is changed, and the resolution of the image generated by the converted image generation unit 5 is changed.

  Also in the third specific example, first, the bandwidth control unit 3 measures and samples the available bandwidth of the network 8. Next, a standard deviation is obtained from the sampled data. Here, an example of the resolution change table 132D will be described with reference to FIG. When the band is br, the resolution of the image data output from the converted image creation unit 5 is the number of horizontal dots w, and the number of vertical dots is h, the resolution is w (0) when the band is br (0). When xh (0), band: br (j), resolution: w (j) × h (j), when band: br (i−1), resolution: w (i−1) × h (i -1) In the case of band: br (i), the resolution is w (i) × h (i), and in the case of band: br (n), the resolution is w (n) × h (n). A range from br (i) to br (i-1) is a minimum range in which a band can be set.

  Here, in the third specific example, in addition to the processing of the second specific example, the network 8 measured from the band corresponding to the resolution of the image data generated and output by the image generation unit 2 (camera 33) that is currently set. When the available bandwidth is large, the resolution of the image generated by the image generation unit 2 shown in FIG. 1 is changed. As shown in FIG. 10, the value to be changed is a resolution corresponding to (average + 2σ) <br (m).

  Next, referring to the flowcharts shown in FIGS. 11 to 14, the resolution change table 132E shown in FIG. 15, and the graph showing the sampling status of the band in the case of connection of multiple sites shown in FIG. 16, the communication shown in FIG. Processing executed by the CPU 10 of the device 1 will be specifically described. First, with reference to FIG. 11, the main process which CPU10 of the communication apparatus 1 performs is demonstrated. This main process is executed by the CPU 10 of the communication apparatus 1 according to a program stored in the program storage area 131 of the HDD 13 when an instruction to transmit / receive image data is input.

  As shown in FIG. 11, when the main process is started, the communication apparatus 1 is initialized (S11). In this initialization process, data and the like stored in the RAM 12 are initialized (S11). Next, a bandwidth calculation process (S12) is performed. Next, resolution change processing (S13) is performed. Details of the bandwidth calculation process (S12) will be described later with reference to the flowchart of FIG. Details of the resolution changing process (S13) will be described later with reference to the flowchart of FIG. After the resolution changing process (S13), an encoding process is performed in accordance with the band (S14). Thereafter, the image data is transmitted from the external communication I / F 26 to the communication apparatus 1 of the communication partner via the network 8 (S15). If the transmission of the image data does not end (S16: NO), the process returns to S12 and executes the processes of S13 to S15. If the transmission of the image data is completed (S16: YES), the process is terminated.

  Next, with reference to FIG. 12, the subroutine of the band calculation process will be described. This bandwidth calculation processing is executed by the CPU 10 of the communication device 1 according to a program stored in the program storage area 131 of the HDD 13 of the communication device 1. In the bandwidth calculation process subroutine, when the process is started, one of the bases registered in the base registration storage area 133 of the HDD 13 is selected as a communication partner (S121). Next, the available bandwidth of the network 8 with the base is calculated (S122).

  In the calculation of the available bandwidth (S122), the packet including the time data on the transmission side is sent from the external communication I / F 26 to the communication device 1 at the selected base via the network 8 at a bandwidth interval to be measured. Send. Next, the communication device 1 on the reception side returns the packet to the communication device 1 on the transmission side. Next, the delay time is calculated from the time when the CPU 10 of the communication device 1 on the transmission side transmits the packet and the time when the packet is received. Next, if the delay time is within a certain time within the communication problem, it is determined that the band is an available band, and if the delay time is not within the certain time, the band is not an available band.

  Next, when packet communication is performed with the communication devices 1 of all the sites registered in the site registration storage area 133 of the HDD 13 and the bandwidth measurement is not completed (S123: NO), the process goes to S121. The processing of returns S121 to S122 is performed. Further, when packet communication is performed with the communication devices 1 of all the sites registered in the site registration storage area 133 of the HDD 13 and the bandwidth measurement is completed (S123: YES), the narrowest bandwidth is selected. The data is stored in the bandwidth storage area 134 of the HDD 13 (S124). In the process of S124, when the communication apparatus 1 is connected to a plurality of points, for example, as shown in FIG. 16, the band of the base A (solid line) and the band of the base B (two-dot chain line) are the narrowest. One band (broken line) is sampled, and the band is stored in the band storage area 134. When the number of bands stored in the band storage area 134 of the HDD 13 is a certain number (for example, 20) or more (S125: YES), the average and standard deviation of the stored bands are calculated, and the average and standard deviation of the HDD 13 are calculated. The calculated average and standard deviation of the bandwidth are stored in the storage area 135 together with the data update flag (S126). If the number of stored bands is less than a certain number (S125: NO), the process is terminated and the process returns to the main process.

  Next, a resolution change processing subroutine will be described with reference to the flowchart of FIG. This bandwidth calculation processing is executed by the CPU 10 of the communication device 1 according to a program stored in the program storage area 131 of the HDD 13 of the communication device 1. First, it is determined whether or not the band average and standard deviation have been updated (S131). This determination is made based on whether an update flag is stored in the average and standard deviation storage area 135. When the average and standard deviation of the band are updated (S131: YES), the resolution change saki switching process (S132) is performed, and the process returns to the resolution change process. This resolution change destination switching process is performed by a resolution change destination switching process subroutine, which will be described later. If the average and standard deviation of the band are not updated (S131: NO), it is determined whether or not the image generation unit 2 and the converted image creation unit 5 are directly connected (S133). In the example of the functional block shown in FIG. 1, this determination is YES when the switch unit 4 is directly connected to the converted image creation unit 5, but the CPU 10 of the communication apparatus 1 shown in FIG. In the case of executing each function shown in the above, YES is determined by not performing the image conversion process. When it is determined YES in the process of S133, the resolution of the image data created by the converted image creation unit 5 (CPU 10) is changed (S134). If NO is determined in the process of S133, the process ends and the process returns to the resolution change process.

  Next, a subroutine for resolution change destination switching processing will be described with reference to the flowchart shown in FIG. 14 and the resolution change table 132E shown in FIG. When the subroutine for the resolution change destination switching process is started, the variable i is reset to “1” (S31). When the average of the HDD 13 and the average of the bands stored in the standard deviation storage area 135> br (i-1) (S32: YES), the process proceeds to the determination process of S34, and the average of the bands> br (i-1). (S32: NO), 1 is added to the value of i, and the determination process of S32 is performed. In the determination process of S34, for example, when br (i)> (average of band ± a)> br (i−1) (a is an arbitrary value, and “a = 2σ” is taken as an example). (S34: YES), the resolution of the image generator 2 (camera 33) is changed to w (i−1) × h (i−1) with reference to the resolution change table 132E shown in FIG. 15 (S35). . The process of S35 is executed by sending a resolution change instruction signal from the CPU 10 to the camera 33, so that the control unit (not shown) of the camera 33 changes the resolution format of the image data. The process of S35 is the process of the first specific example described above. Thereafter, the image generation unit 2 and the encoding unit 6 are directly connected by the switch unit 4 (S36), and the process is terminated. In the communication apparatus 1 shown in FIG. 2, the CPU 10 performs software encoding without performing the reduction or enlargement processing of the image data input from the camera 33.

  If NO is determined in the determination process of S34, it is determined whether (average band + a)> br (i) is satisfied (S37). When (average band + a)> br (i) (S37: YES), the resolution of the image generation unit 2 (camera 33) is referred to the resolution change table 132E shown in FIG. It is changed to w (k) × h (k) that satisfies the case of <(average of band + a) <br (k + 1) (S38). If br (k) is the maximum bandwidth br (n) of the resolution change table 132E, the resolution is w (n) × h (n). The process of S38 is the process described in the third specific example.

  Next, the resolution of the image data created by the converted image creation unit 5 is set to w satisfying the case of br (l) <(average band) <br (l + 1) with reference to the resolution change table 132E shown in FIG. (L) × h (l) is changed (S39). If br (l) is the minimum bandwidth br (0) of the resolution change table 132E, the resolution is w (0) × h (0). The process of S39 is the process described in the second specific example. Thereafter, the image generation unit 2 (camera 33) and the converted image creation unit 5 are directly connected (S40), and the process ends. In the communication apparatus 1 shown in FIG. 2, this processing is performed by the CPU 10 performing reduction or enlargement processing on the image data input from the camera 33, and then performing software encoding.

  As described above, in the above embodiment, when the width of the band variation is small and br (i)> (average band ± 2σ)> br (i−1) is satisfied (first Specifically, only the resolution of the image data generated by the image generation unit 2 (camera 33) is changed (S35). This is because the change of the resolution of the image data generated by the image generation unit 2 (camera 33) takes longer than the change of the resolution of the image data generated by the converted image generation unit 5, but the width of the fluctuation of the band. This is because it is small and does not change frequently. Further, in the case of changing the resolution of the image data created by the converted image creating unit 5, the load on the CPU 10 is large, but for changing the resolution of the image data generated by the image generating unit 2 (camera 33). The load on the CPU 10 is not large.

  In the above-described embodiment, when the bandwidth fluctuation is large (second specific example), the resolution of the image data created by the converted image creation unit 5 is changed (S39). When the bandwidth fluctuation is large, it is necessary to change the resolution of the image data frequently. Therefore, the resolution of the image data created by the converted image creation unit 5 is changed regardless of time.

  Further, when the width of the band fluctuation is large (when br (i)> (average band ± 2σ)> br (i−1)), the band fluctuation width is a predetermined condition ((average band + 2σ)). > Br (i)), the resolution of the image data generated by the image generation unit 2 (camera 33) is changed (S35), and the resolution of the image data generated by the converted image generation unit 5 is changed. (S39) (third specific example).

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, a case has been described in which each function unit illustrated in FIG. 1 is realized by software using the known personal computer as the communication device 1 as an example. You may use the apparatus which implement | achieved by hardware.

  Further, when the communication apparatus 1 is connected to a plurality of points, for example, as shown in FIG. 16, the narrowest band (the two-dot chain line) of the base A band (solid line) and the base B band (two-dot chain line) (Dotted line) may be sampled, and the resolution may be set from the band.

DESCRIPTION OF SYMBOLS 1 Communication apparatus 2 Image generation part 3 Band control part 4 Switch part 5 Conversion image creation part 6 Encoding part 8 Network 10 CPU
11 ROM
12 RAM
13 HDD
26 External communication I / F
33 Camera 100 Video Conference System 132A-132E Resolution Change Table

Claims (5)

A communication device capable of transmitting image data to another communication device via a network,
Image generation means having a resolution conversion processing function for converting the resolution of image data to be generated;
Converted image creation means for creating image data by reducing or enlarging the image data generated by the image generation means;
A communication bandwidth measuring means for measuring an available bandwidth of the network;
A fluctuation amount calculating means for calculating a fluctuation amount of the usable bandwidth measured by the communication band measuring means;
Resolution changing means for changing at least one of the resolution of the image data generated by the image generating means and the resolution of the image data converted by the converted image creating means based on the fluctuation amount calculated by the fluctuation amount calculating means. When,
A communication apparatus comprising: output means for encoding image data having a resolution changed by the resolution changing means and outputting the encoded image data to the other communication apparatus via the network.     The resolution changing unit changes the resolution of the image data generated by the image generating unit when the variation calculated by the variation calculating unit is within a predetermined range. The communication device described.     The resolution changing means changes the resolution of image data converted by the converted image creating means when the fluctuation amount calculated by the fluctuation amount calculating means is not within a predetermined range. Item 3. The communication device according to Item 1 or 2. A communication method for performing communication by changing the resolution of the image data performed in an apparatus that generates image data transmitted via a network,
An image generation process capable of resolution conversion processing for converting the resolution of image data to be generated;
A converted image creating step for creating image data by reducing or enlarging the image data generated in the image generating step;
A communication bandwidth measuring step for measuring the available bandwidth of the network;
A fluctuation amount calculating step of calculating a fluctuation amount of the usable band measured by the communication band measuring step;
A resolution changing step of changing at least one of the resolution of the image data generated in the image generation step and the resolution of the image data converted in the converted image creation step based on the variation amount calculated in the variation amount calculation step. When,
An output step of encoding the image data having the resolution changed in the resolution changing step and outputting the encoded image data to the other communication device via the network. An image generation process capable of resolution conversion processing for converting the resolution of image data to be generated;
A converted image creating step for creating image data by reducing or enlarging the image data generated in the image generating step;
A communication bandwidth measuring step for measuring the available bandwidth of the network;
A fluctuation amount calculating step of calculating a fluctuation amount of the usable band measured by the communication band measuring step;
A resolution changing step of changing at least one of the resolution of the image data generated in the image generation step and the resolution of the image data converted in the converted image creation step based on the variation amount calculated in the variation amount calculation step. When,
Encoding the image data with the resolution changed in the resolution changing step, and outputting the image data to the other communication device via the network is executed by a computer capable of transmitting the image data to the other communication device via the network. A communication program characterized by the above.

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