Information transmission device, information transmission method, and computer program

Abstract

To provide an information transmission device that can reduce fluctuations in image quality due to fluctuations in network bandwidth.SOLUTION: An information transmission device for transmitting information such as video includes calculation means for calculating a first representative value that is a representative value of an estimated bandwidth of a network in a first period, and a second representative value that is a representative value in a second period that is longer than the first period, and control means for controlling a transmission bit rate so as to be between an upper limit based on the first representative value and a lower limit based on the second representative value.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an information transmission device, an information transmission method, a computer program, and the like. [Background technology]

[0002] In the past, dynamically controlling the transmission bit rate in response to changing network conditions was effective in real-time distribution without video distortion or long pauses. However, when streaming video or other content over a network in real time, the use of the same network by an unspecified number of people can limit the network bandwidth, potentially causing video distortion or pauses.

[0003] In contrast, a technology called Adaptive Bit Rate (ABR) dynamically controls the transmission bit rate according to network conditions, allowing for continuous streaming without image distortion or long pauses.

[0004] One method for achieving ABR is to control the transmission bit rate using a bandwidth estimated from network information. For example, SRT (Secure Reliable Transport), a video transmission protocol, has a function for obtaining an estimated network bandwidth, which can be used to achieve ABR.

[0005] For example, in Patent Document 1, a bandwidth is estimated based on a measurement value of the period from the start of data transmission to the reception of a reception acknowledgment, and the transmission bit rate is controlled with the estimated bandwidth as the upper limit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-89416 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the performance of ABR varies depending on how the estimated bandwidth is used. For example, if the estimated bandwidth is quickly followed, and the bandwidth is limited immediately after recovery, the transmission bit rate will also increase and then decrease immediately, causing large fluctuations in the quality of the streaming video and resulting in video distortion.

[0008] Furthermore, if the rate is made to follow slowly, it takes time for the transmission bit rate to increase after the band is recovered, which results in a longer period of low bit rate and a longer period of low image quality.

[0009] Therefore, one object of the present invention is to provide an information transmission device that can reduce fluctuations in image quality due to fluctuations in network bandwidth. [Means for solving the problem]

[0010] In order to achieve the above object, an information transmission device according to one aspect of the present invention comprises: a calculation means for calculating a first representative value that is a representative value of an estimated bandwidth of a network in a first period and a second representative value that is a representative value in a second period that is longer than the first period; The present invention is characterized by comprising a control means for controlling the transmission bit rate so that it is between an upper limit based on the first representative value and a lower limit based on the second representative value. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an information transmission device that can reduce fluctuations in image quality due to fluctuations in network bandwidth. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of the configuration of an information transmission system 100 according to a first embodiment of the present invention. [Figure 2]1 is a functional block diagram showing an example of the internal configuration of a camera 1000 according to a first embodiment of the present invention. [Figure 3] 2 is a functional block diagram showing an example of the internal configuration of a client device 2000 according to the first embodiment of the present invention. FIG. [Figure 4] 4 is a flowchart showing an example of a transmission bit rate control process in the information processing method according to the first embodiment of the present invention. [Figure 5] 10 is a graph illustrating an example of a change in the average estimated bandwidth for a first period according to the first embodiment of the present invention. [Figure 6] 10 is a graph showing an example of a change in the average estimated bandwidth for a second period according to the first embodiment of the present invention. [Figure 7] 10 is a table showing an example of the degree of change in estimated bandwidth for each time period according to the second embodiment of the present invention. [Figure 8] 10 is a table showing an example of a process for increasing a transmission bit rate for each degree of change in an estimated bandwidth according to the second embodiment of the present invention. [Figure 9] 10 is a flowchart showing an example of a parameter adjustment process in an information processing method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment. In each drawing, the same members or elements are given the same reference numerals, and duplicated descriptions will be omitted or simplified.

[0014] <Embodiment 1> An information transmission device according to a first embodiment of the present invention will be described below with reference to Figures 1 to 6. Figure 1 is a diagram showing an example of the configuration of an information transmission system 100 according to the first embodiment of the present invention. The information transmission system 100 in this embodiment is composed of a camera 1000, a client device 2000, a network 3000, etc. The camera 1000 can transmit video data to the client device 2000 via the network 3000.

[0015] 2 is a functional block diagram showing an example of the internal configuration of a camera 1000 according to the first embodiment of the present invention. The camera 1000 functions as an information transmission device. Note that some of the functional blocks shown in FIG. 1 are realized by causing a CPU 1006, which serves as a computer included in the camera 1000, to execute a computer program stored in a memory, which serves as a storage medium.

[0016] However, some or all of these functions may be implemented by hardware. Examples of hardware that can be used include dedicated circuits (ASICs) and processors (reconfigurable processors, DSPs). Furthermore, the functional blocks shown in FIG. 1 do not have to be built into the same housing, and may be configured as separate devices connected to each other via signal paths. The above explanation regarding FIG. 2 also applies to FIG. 3.

[0017] In Fig. 2, reference numeral 1001 denotes a control unit, which performs overall control of the camera 1000 as an information transmission device. The control unit 1001 has a CPU 1006 as a computer. Reference numeral 1002 denotes a storage unit. The storage unit 1002 is mainly used as a storage area for various data, such as a storage area for computer programs executed by the control unit 1001 and a work area during execution of the computer programs.

[0018] Reference numeral 1003 denotes an imaging unit. The imaging unit 1003 captures an image of a subject, converts the acquired analog signal into digital data, and outputs the digital data as a captured image to the storage unit 1002. Reference numeral 1004 denotes a communication unit. The communication unit 1004 transmits information such as video data and various setting values ​​to the client device 2000 via the network 3000 using the video transmission protocol SRT, and receives information such as various setting values ​​and confirmation responses.

[0019] A transmission bit rate control unit 1005 controls the transmission bit rate when transmitting video data to the client device 2000 based on network information obtained by the communication unit 1004.

[0020] 2 is an example of a preferred embodiment of the information transmission device of the present invention, and various modifications and changes are possible within the scope of the present invention. For example, the communication unit uses SRT as the video transmission protocol, but is not limited to SRT.

[0021] 3 is a functional block diagram showing an example of the internal configuration of the client device 2000 according to the first embodiment of the present invention. Reference numeral 2001 denotes a control unit that performs overall control of the client device 2000. The control unit 2001 has a CPU 2006 as a computer.

[0022] Reference numeral 2002 denotes a memory unit. The memory unit 2002 is mainly used as a storage area for various data, such as a storage area for computer programs executed by the control unit 2001 and a work area during execution of the computer programs. Reference numeral 2003 denotes an output unit. The output unit 2003 is composed of, for example, an LCD or an organic EL display, and outputs various setting screens and screens of images received from the camera 1000 to the user of the client device 2000.

[0023] Reference numeral 2004 denotes an input unit. The input unit 2004 is composed of, for example, buttons, a cross key, a touch panel, a mouse, etc., and notifies the control unit 2001 of the content of screen operations performed by the user. Reference numeral 2005 denotes a communication unit. The communication unit 2005 receives information such as video data and various setting values ​​from the camera 1000 via the network 3000 using the video transmission protocol SRT, and also transmits various setting values, confirmation responses, etc.

[0024] 3 is an example of a preferred embodiment of the information transmission device of the present invention, and various modifications and changes are possible within the scope of the present invention. For example, the communication unit uses SRT as the video transmission protocol, but is not limited to SRT.

[0025] Fig. 4 is a flowchart showing an example of transmission bit rate control processing in the information processing method according to the first embodiment of the present invention, and the transmission bit rate control processing performed in the camera 1000 that solves the above-mentioned problems will be described using the flowchart of Fig. 4. Note that the operation of each step in the flowchart of Fig. 4 is performed sequentially by a CPU or the like serving as a computer in the control unit 1001 executing a computer program stored in memory.

[0026] While the camera 1000 is distributing video at an arbitrary transmission bit rate to the client device 2000, in step S4001, the SRT function is used to measure, acquire, and save the current estimated bandwidth from network statistical information. Here, the estimated bandwidth is an estimate of the maximum amount of data that can be transmitted over the network per unit time.

[0027] In step S4002, an average (first representative value) is calculated as a representative value of the estimated bandwidth acquired from the present to a predetermined time ago, which is defined as a first period (short period). Also, an average (second representative value) is calculated as a representative value of the estimated bandwidth acquired from the present to a predetermined time ago, which is defined as a second period (long period) longer than the first period.

[0028] Here, step S4002 functions as a calculation step (calculation means) that calculates a first representative value that is a representative value of the estimated bandwidth of the network in a first period and a second representative value that is a representative value in a second period that is longer than the first period.

[0029] In this embodiment, the first period is, for example, 3 seconds, and the second period is, for example, 15 seconds. Then, the average of the estimated bandwidth acquired from the present to 3 seconds ago and the average of the estimated bandwidth acquired from the present to 15 seconds ago are calculated.

[0030] If this process has just started and the first or second period has not yet elapsed, the average of the estimated bandwidth from the start to the present is calculated. The average described above may be a weighted average calculated by assigning a larger weight to newer estimated bandwidths along the time series. In other words, the first representative value or the second representative value may be a weighted average calculated by assigning a larger weight to newer estimated bandwidths along the time series.

[0031] FIG. 5 is a graph illustrating an example of a change in the average estimated bandwidth for a first period according to embodiment 1 of the present invention, and FIG. 6 is a graph showing an example of a change in the average estimated bandwidth for a second period according to embodiment 1 of the present invention.

[0032] Graphs 5001 and 6001 show the fluctuations in the estimated bandwidth, and graphs 5002 and 6002 show the averages of the estimated bandwidth calculated every 3 seconds (first period) and 15 seconds (second period), respectively. As shown in Figures 5 and 6, the longer the time taken to calculate the average, the smaller the change in the average estimated bandwidth and the more delayed the change. In step S4003, when α is a predetermined margin (threshold), the average estimated bandwidth for the first period calculated in step S4002 -α is set as the upper limit, and it is determined whether the transmission bit rate exceeds the upper limit.

[0033] If the transmission bit rate is set to the same value as the estimated bandwidth, there is a risk of exceeding the bandwidth, so in this embodiment, the upper limit is set to a value α (e.g., 3 Mbps) lower than the estimated bandwidth. That is, the upper limit is set to a value obtained by subtracting a predetermined margin α from the average value serving as the first representative value. If the result of the determination in step S4003 is that the transmission bit rate exceeds the upper limit, the transmission bit rate is reduced in step S4004.

[0034] That is, in this embodiment, the average estimated bandwidth for the first period (3 seconds) -α (3Mbps) is set as the upper limit, and if the transmission bit rate exceeds this upper limit, the transmission bit rate is reduced so that it is equal to or less than the upper limit based on the first representative value. After that, the transmission bit rate is not changed for at least 1 second, for example. Then, the process returns to step S4001.

[0035] If the result of the determination in step S4003 is that the transmission bit rate is equal to or lower than the upper limit, the process proceeds to step S4005. In step S4005, when α is a fixed margin, the average of the estimated bandwidth for the second period (second representative value) calculated in step S4002 -α is set as the lower limit, and it is determined whether the transmission bit rate is lower than the lower limit.

[0036] That is, the lower limit here is the value obtained by subtracting a predetermined margin α from the average value serving as the second representative value. In this way, the upper or lower limit is the first or second representative value to which a predetermined margin has been added or subtracted.

[0037] If it is determined that the transmission bit rate is lower than the lower limit, the transmission bit rate is increased above the lower limit based on the second representative value in step S4006.

[0038] In this embodiment, the lower limit is set to the average estimated bandwidth for 15 seconds (second period) -α (3 Mbps), and if the transmission bit rate is lower than the lower limit, the transmission bit rate is increased above the lower limit, and then the transmission bit rate is not changed for at least 1 second, for example.Then, the process returns to step S4001 and the control of the transmission bit rate is repeated.

[0039] Here, steps S4004 and S4006 function as a control step (control means) that controls the transmission bit rate so that it is between an upper limit based on the first representative value and a lower limit based on the second representative value.

[0040] As explained above, in this embodiment, the process for lowering the transmission bit rate (step S4004) is performed based on the average estimated bandwidth for the first period (short period) where the amount of change is large and the response is fast, while the process for increasing the transmission bit rate (step S4006) is performed based on the average estimated bandwidth for the second period (long period) where the amount of change is small and the response is slow.

[0041] This allows the transmission bit rate to be quickly lowered when restricting the bandwidth, preventing image distortion and long pauses, and when restoring the bandwidth, the transmission bit rate can be increased after the bandwidth has stabilized, suppressing fluctuations in image quality and shortening the period of low image quality.

[0042] Although the first embodiment uses an average (arithmetic mean value, etc.) as the representative value, the representative value is not limited to the average and may be, for example, a statistical median, mode, etc. Alternatively, the representative value may be a value obtained by passing through a predetermined filter (a low-pass filter, a median filter, etc.).

[0043] In the above description, the speed at which the transmission bit rate is decreased or increased, the first period, the second period, the value of the margin α, etc. can be set arbitrarily. The video transmission protocol is not limited to SRT, and other protocols can be used. Audio may also be transmitted in addition to video.

[0044] <Embodiment 2> Next, a second embodiment of the present invention will be described with reference to Figures 7 and 8. In the second embodiment, the configurations in Figures 1 to 3 and the control process for increasing the transmission bit rate performed by the camera 1000 in Figure 4 are the same as those in the first embodiment, and therefore will not be described again.

[0045] In the first embodiment, the increase in the transmission bit rate is constant during the second period (long period) in the transmission bit rate control process. In the second embodiment, these values ​​are adjusted taking into account that the degree of network congestion varies depending on the time of day.

[0046] FIG. 7 is a table showing an example of the degree of change in estimated bandwidth for each time period in embodiment 2 of the present invention, and shows an example of measuring the degree of change in estimated bandwidth for each time period during a day.

[0047] As shown in Figure 7, when the network is most congested at night, sudden restrictions on the network bandwidth occur frequently, causing the degree of change in the estimated bandwidth to increase. Therefore, the parameters are adjusted so that the transmission bit rate increases more gradually during times when the degree of change in the estimated bandwidth is greater.

[0048] If the transmission bit rate is increased too quickly during a period when the estimated bandwidth is changing significantly, the bandwidth may be suddenly restricted, causing the transmission bit rate to drop, resulting in drastic fluctuations in image quality and resulting in video distortion.

[0049] Fig. 8 is a table showing an example of a process for increasing the transmission bit rate for each degree of change in the estimated bandwidth according to the second embodiment of the present invention. In the second embodiment, based on a table like that shown in Fig. 8, the second period (long period) is lengthened and the increase in the transmission bit rate is reduced during the nighttime, which is a time period when the degree of change in the estimated bandwidth is large. This allows the transmission bit rate to increase gradually, reducing drastic fluctuations in image quality and video distortion.

[0050] 9 is a flowchart showing an example of a parameter adjustment process in an information processing method according to the second embodiment of the present invention. Note that the CPU serving as a computer in the control unit 1001 executes a computer program stored in memory, thereby sequentially performing the operations of the steps in the flowchart in FIG.

[0051] In step S9001, the SRT function is used to measure and acquire the current estimated bandwidth from network statistical information, and store it. In step S9002, it is determined whether a third period has elapsed since the start of the flow in Figure 9, or whether a third period has elapsed again since the previous third period elapsed. If the determination in step S9002 is No, the process returns to step S9001.

[0052] If the determination in step S9002 is Yes, in step S9003, a value representing the degree of change in the estimated bandwidth acquired from the present to a predetermined time ago, which is determined as a third period, is calculated. In the second embodiment, the third period is set to, for example, four hours, and the degree of change in the estimated bandwidth for the third period is calculated as a statistical variance.

[0053] In step S9004, it is determined whether a predetermined period has elapsed since the start of the flow in Fig. 9, or whether a predetermined period has elapsed again since the previous predetermined period elapsed. In this embodiment, the predetermined period is, for example, 24 hours, and if the determination result shows that 24 hours (predetermined period) have not elapsed, the process returns to step S9001 and repeatedly calculates the variance of the estimated bandwidth for the next 4 hours (third period).

[0054] If the answer in step S9004 is Yes, in step S9005, the variances calculated for each third period (4 hours) from the present to the predetermined period (24 hours) ago are compared. In step S9006, the larger the variance of the period, the longer the second period (longer period) is made when performing transmission bit rate control processing in the next period, or the smaller the increase in transmission bit rate is made.

[0055] That is, in the second embodiment, the degree of change in the estimated bandwidth in a third period that is longer than the second period is calculated, and the greater the degree of change in the period, the more gradually the transmission bit rate is increased in the next period, or the second period is lengthened in the next period.

[0056] Thereafter, the process returns to step S9001, and the process is repeated to adjust the value of the second period and the increase amount of the transmission bit rate when the transmission bit rate control process is performed in the next cycle.

[0057] The third period in the second embodiment may be, for example, one day, and the predetermined cycle may be, for example, one week, and the network congestion level may be measured for each day of the week. Also, the value representing the degree of change in bandwidth may be a different statistical value instead of the variance, or may be a time-differential value.

[0058] As described above, in the second embodiment, the increase in the transmission bit rate during the second period in the transmission bit rate control process is adjusted depending on the degree of network congestion depending on the time period. This allows the transmission bit rate to be increased more gradually during times of network congestion, making it possible to reduce large fluctuations in image quality and video distortion caused by sudden bandwidth restrictions.

[0059] Although the present invention has been described in detail above based on the preferred embodiments, the present invention is not limited to the above embodiments, and various modifications and combinations of the above embodiments are possible based on the spirit of the present invention, and are not excluded from the scope of the present invention. The present invention also includes the following combinations.

[0060] (Configuration 1) An information transmission device characterized by comprising: a calculation means for calculating a first representative value that is a representative value of an estimated bandwidth of a network in a first period, and a second representative value that is a representative value in a second period that is longer than the first period; and a control means for controlling a transmission bit rate so that it is between an upper limit based on the first representative value and a lower limit based on the second representative value.

[0061] (Configuration 2) The information transmitting device according to configuration 1, wherein the estimated bandwidth is an estimate of the maximum amount of data that can be transmitted over the network per unit time.

[0062] (Configuration 3) The information transmission device described in configuration 1 or 2, characterized in that the first representative value or the second representative value is a weighted average value calculated by assigning a larger weight to the newer estimated band along a time series.

[0063] (Configuration 4) An information transmission device according to any one of configurations 1 to 3, characterized in that the upper limit or the lower limit is obtained by adding or subtracting a predetermined margin to the first representative value or the second representative value.

[0064] (Configuration 5) The information transmission device described in any one of configurations 1 to 4, characterized in that the control means calculates the degree of change in the estimated bandwidth in a third period that is longer than the second period, and the greater the degree of change in the period, the more gradually the transmission bit rate is increased in the next period.

[0065] (Configuration 6) The information transmission device described in any one of configurations 1 to 5, characterized in that the control means calculates the degree of change in the estimated bandwidth in a third period that is longer than the second period, and the greater the degree of change in the period, the longer the second period is made in the next cycle.

[0066] (Method) An information transmission method comprising: a calculation step of calculating a first representative value that is a representative value of the estimated bandwidth of a network in a first period and a second representative value that is a representative value in a second period that is longer than the first period; and a control step of controlling a transmission bit rate so that it is between an upper limit based on the first representative value and a lower limit based on the second representative value.

[0067] (Program) A computer program for controlling each means of the information transmitting device according to any one of configurations 1 to 6 by a computer.

[0068] In order to realize part or all of the control in the above-described embodiments, a computer program that realizes the functions of the above-described embodiments may be supplied to an information transmission device or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the information transmission device or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. [Explanation of symbols]

[0069] 1000: Camera 2000: Client device 3000: Network

Claims

1. a calculation means for calculating a first representative value that is a representative value of an estimated bandwidth of a network in a first period and a second representative value that is a representative value of an estimated bandwidth of a network in a second period that is longer than the first period; an information transmitting device comprising: a control means for controlling a transmission bit rate so that the transmission bit rate is between an upper limit based on the first representative value and a lower limit based on the second representative value.

2. 2. The information transmitting device according to claim 1, wherein the estimated bandwidth is an estimated value of a maximum amount of data that can be transmitted over the network per unit time.

3. 2. The information transmission device according to claim 1, wherein the first representative value or the second representative value is a weighted average value calculated by assigning a larger weight to the newer estimated band along a time series.

4. 2. The information transmitting device according to claim 1, wherein the upper limit or the lower limit is obtained by adding or subtracting a predetermined margin to the first representative value or the second representative value.

5. The information transmission device described in claim 1, characterized in that the control means calculates the degree of change in the estimated bandwidth in a third period longer than the second period, and the greater the degree of change in the period, the more gradually the transmission bit rate is increased in the next period.

6. The information transmission device according to claim 1, characterized in that the control means calculates the degree of change in the estimated bandwidth in a third period longer than the second period, and the greater the degree of change in the period, the longer the second period is made in the next cycle.

7. a calculation step of calculating a first representative value that is a representative value of the estimated bandwidth of the network in a first period and a second representative value that is a representative value in a second period that is longer than the first period; a control step of controlling a transmission bit rate so that the transmission bit rate is between an upper limit based on the first representative value and a lower limit based on the second representative value.

8. A computer program for controlling each means of the information transmitting apparatus according to any one of claims 1 to 6 by a computer.

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