JPH11161571A - Adaptive transmission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit image information to a client with the delay a degree without giving unpleasant feeling even when using a radio channel and a low- speed channel whose the throughput fluctuates. SOLUTION: Image request signals from a client 1 are informed to a server 3 provided with original images through a proxy server 2 in the case that the image information is not stored in a cache 3 of the proxy server 2 and the image information sent from the server 3 is stored in the cache 4. The proxy server 2 inquires a channel speed prior to the transmission of the image information and the client 1 informs the channel speed. The proxy server 2 changes the image quality of the image information by an image quality change function 2a corresponding to the channel speed, transmits it to the client 1 and stores the image information of the changed image quality in the cache 4. The proxy server 2 can be provided with a frequency component separation function 2b, a low frequency component can be sent to the client 1 and a high frequency component can be sent later.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting image information stored in a server to a client in an information communication network such as the Internet, in accordance with the speed of a transmission path and its fluctuation. Proxy
The present invention relates to an adaptive transmission control system capable of adaptively converting and transmitting an image by a server (Proxy Server). Here, the image information includes both a still image and a moving image. On the Internet, WWW (World Wide W
When accessing hypertext including text, graphics, images, and the like using the browser of eb), it is generally a problem to efficiently transmit image information whose data amount is much larger than that of text information. In particular, it is important to deal with this problem when using a line such as a wireless line whose throughput varies depending on the radio wave condition or a low-speed line using a modem.

[0002]

2. Description of the Related Art Conventionally, in accessing WWW information, a proxy server capable of realizing efficient access by reducing the load of line use by caching original information and holding the information is provided at an appropriate location. Can be placed in
Is becoming more common. This is the same for image information. The proxy server, in addition to the cache function,
Offers firewall function, code conversion function, multi-protocol function, etc.

The operation of the cache function of the proxy server is as follows. First, when a client requests data acquisition by a URL (Uniform Resource Locator), which is a data identification name, the proxy server receives the data from the WWW server having the original data via a communication line and returns the data to the client. . At this time U
Cache RL and data. The same UR after the second time
When there is a data acquisition request at L, the cached data is returned to the client without making an inquiry to the WWW server. With respect to accessing image information via a proxy server, the conventional approach has simply cached the original information without changing the data size.

[0004]

Therefore, when the transmission path between the proxy server and the client is unstable like a wireless line and the throughput fluctuates every moment, or when the PPP (Point-to-Point to-Point Protocol)
In the case of a low-speed line such as that accessed by a user, simply transmitting cached image information with a large amount of data takes too much time, and gives the user a satisfactory access feeling. I can't. The present invention has been made in view of the above-described circumstances, and has a delay that does not cause a user to feel discomfort even if the throughput fluctuates when using a wireless line, or even if a slow line is used from the beginning. It is an object of the present invention to be able to transmit image information to a client.

[0005]

FIG. 1 is a diagram illustrating the principle of the present invention. As shown in the figure, in the present invention, the client 1 is provided with a line speed detecting function 1a and a function of notifying the proxy server 2 of the line speed, and the proxy server 2 is provided with an image quality changing function (or a frequency component of image information). Separation function) 2a and a function of receiving the line speed notified from the client are provided, and the above-mentioned problem is solved as follows.

[0006] (1) An image request signal from the client 1 is stored in the cache 4 of the proxy server 2.
Is not stored in the server 3, the server 3 having the original image is notified via the proxy server 2. The image information sent from the server 1 is stored in the cache 4 of the proxy server, and the image quality is changed by the image quality changing function 2a according to the line speed between the clients 1 and transmitted to the client. Here, in the proxy server 2,
Prior to transmitting the image information to the client 1, the client 1 is inquired about the line speed, and the quality of the image generated by the proxy server 2, that is, the data amount is determined according to the line speed information. That is, an image having a smaller amount of data is generated by lowering the quality as the line is slower. If the proxy server 2 and the client 1 are wireless lines using a PHS or PDC (cellular phone), the actual line speed (throughput) changes every moment depending on the radio wave condition. Therefore, based on the time when the radio wave condition is good, the image quality is reduced in accordance with the degradation of the line speed obtained from the client, and the data amount is reduced for transmission. As a result, it is possible to give the user a feeling of access as if the user were always connected at the maximum speed, without unnecessarily increasing the transmission delay.

In the case of a wireless line in which the effective throughput changes with time, a high-quality image is once transmitted with the throughput obtained at the start of image transmission, and then the radio wave condition changes. It is considered that the throughput is deteriorated. In such a case, cancel the first transmission and regenerate a lower quality image,
Transmit the image. Thereby, it is possible to avoid deterioration of the transmission delay.

(2) When a low-speed line is used between the proxy server and the client, the transmission time becomes worse as the lower-speed line is used. Therefore, based on the time when a high-speed line is used, the image quality is reduced according to the state of the decrease in the line speed obtained from the client to reduce the amount of data for transmission. As a result, it is possible to give the user a sense of access that does not make the user aware that the connection is made via the low-speed line without unnecessarily increasing the transmission delay.

(3) Image information created by changing the quality in response to a transmission request from the client 1 is stored in the cache 4 of the proxy server 2 together with the original image.
In response to an image transmission request received from another client according to the transmission speed, if there is any cached image information that matches the required quality from the client, the cached image information is sent directly to the client. . Thereby, the processing time of the image information can be omitted.

(4) The proxy server 2 is provided with a profile information table 2b storing profile information for each user, and an image (for example, an image desired to be transmitted by the user while reducing the quality, that is, the data amount) is stored in the profile information table 2b. The identification name of the advertisement information is registered. If the image information requested by the user is previously registered in the profile information table 2b by the user, the proxy server 2 reduces the quality of the image, that is, the data amount, and transmits the image to the client 1. (5) The proxy server 2 is provided with a frequency component separation function 2a for separating the frequency component of the image information, and the image information is added to the low-frequency component capable of displaying a rough image, and a fine image is obtained by adding the component. Divided into high frequency components that can be displayed. Then, the low-frequency component is first sent to the client 1 to show a rough image, and the high-frequency component is sent later according to the idle time of the line or a request from the user, thereby improving the line utilization efficiency.

In the invention of claims 1 and 2 of the present invention,
Since it is configured as described in (1) and (2) above,
By absorbing the line speed between the server and the client and its fluctuation by changing the image quality, it is possible to always connect to the user at a virtually constant line speed without extremely increasing the time required for image transmission. It is possible to give the user a sense of access. In the invention of claim 3 of the present invention, the time required for image processing is shortened because the image having the quality changed is cached in the cache 4 of the proxy server 2 together with the configuration as described in (3) above. can do. In the invention of claim 4 of the present invention,
By configuring as in the above (4) and registering in advance the identification name of the image information that is not so important in the profile information table 2b of the proxy server 2, the quality of the image information is automatically reduced. The time required for image transmission can be reduced. In the invention of claim 5 of the present invention, since the configuration is made as in the above (5), it is possible to increase the line utilization efficiency.

[0012]

FIG. 2 shows the configuration of a system according to a first embodiment of the present invention. In the figure, 11 is a client, 12 is a proxy server, 13 is a server,
The client 11 is provided with a line speed detecting function 11a for detecting a line speed.
In response to the inquiry from the client 2, the line speed is transmitted from the client 11 to the proxy server 12 via the communication line 15. Further, the proxy server 12 is provided with an image quality changing function 12a, and when the line speed between the clients is notified, the proxy server 1
The image quality of the image to be transmitted is changed according to the line speed between the client 2 and the client 11 and transmitted to the client. Further, the proxy server 12 has a cache 14, and the image information and image quality changing function 12
a, the image information is changed, and the image information is
Is accumulated in

In FIG. 1, an image request signal from a client 11 is transmitted via a communication line 15 to a proxy server 1.
2, the proxy server 12 notifies the server 13 having the original image via the communication line 15 that the requested image is not stored in the cache 14.
Then, the image information sent from the server 13 is stored in the cache 14 and sent to the client 11. If the requested image is stored in the cache 14, the image information stored in the cache 14 is transmitted to the client 11.

Before transmitting the image information, a proxy
The server 12 inquires the client 11 about the line speed. Line speed detection function 11 of client 11
In response to the inquiry, a notifies the proxy server 12 of the line speed information. The image quality changing function 12a of the proxy server 12 changes the image quality of an image transmitted to the client 11 according to the line speed information. That is,
The lower the line speed, the lower the quality of the image, and the smaller the amount of data, the more the image is transmitted to the client 11. The image information created by changing the quality in response to a transmission request from the client is stored in the cache 14 together with the original image. In response to an image transmission request received from another client according to the transmission speed, if there is any cached image information that matches the required quality from the client, the cached image information is sent directly to the client. . Thereby, the processing time of the image information can be omitted.

The proxy server 12 and the client 11
If the interval is a wireless line using a PHS or PDC (mobile phone), the actual line speed (throughput) changes every moment depending on the radio wave condition. Therefore, based on the time when the radio wave condition is good, the image quality is reduced according to the deterioration state of the line speed obtained from the client 11, the data amount is reduced, and the data is transmitted from the proxy server 12 to the client 11.
Thus, without unnecessarily increasing transmission delay,
It is possible to give the user an access feeling as if the user were always connected at the maximum speed.

When a radio line whose effective throughput changes with time is targeted, a high-quality image is once transmitted at the throughput obtained at the start of image transmission, and then the radio wave condition changes. It is conceivable that the throughput deteriorates. In such a case, once transmission of a high-quality image, that is, a large amount of information, is started from the proxy server 12 and the transmission speed is degraded due to a change in the status of the wireless communication line, the first transmission is canceled. Alternatively, an image whose quality is lowered, that is, an image with a small amount of information may be newly generated, and the image may be transmitted. This can prevent the transmission delay from becoming extremely worse.

On the other hand, between the proxy server 12 and the client 11, a PPP (Point-to-Point Pro
In the case of (tocol), the transmission time becomes worse as a slower line is used. Therefore, based on a high-speed line being used, the image quality is reduced according to the state of the decrease in the line speed obtained from the client, and the data amount is reduced for transmission. As a result, it is possible to give the user a sense of access that does not make the user aware that the connection is made via the low-speed line without unnecessarily increasing the transmission delay.

FIG. 3 is a flowchart showing an outline of the image quality conversion processing procedure in the proxy server. In this embodiment, the image is intended for JPEG. The q factor (quality factor) is a coefficient representing the quality of a JPEG image. The larger the value, the better the quality and the larger the data tatami. Also, in this flow chart,
Fig. 4 shows the relationship between data size (vertical axis) and q factor (horizontal axis)
Shown in

In the present embodiment, the image quality conversion processing is performed as follows. (1) Generate an image of q = 30. The data size of the image of q = 30 is set to s30 (step S1). (2) The difference Δ between the data size s30 and the target data size (data size as a target value: Target Data Size) is obtained (step S2). Then, it is checked whether or not the difference Δ falls within the allowable error range (± 5 to 10%) (Step S).
3) If within the allowable error range, the current image quality parameter is used as an estimated value corresponding to the target data size, and the target image is set to an image of q = 30 (step S1).
3).

(3) If the difference Δ does not fall within the allowable error range, a new image is generated. At this time, since the target data size is larger than s30, q is changed in a larger direction. Specifically, 20 is added to q as the initial value of q Step (if the target data size is smaller, q Step is subtracted), and q step is changed to （(steps S4 and S5). ). Here, when the target data size is smaller and the q Step is subtracted, if it becomes smaller than the longest value of the image quality parameter, the image quality parameter is replaced with the previous value (steps S6 and S8), and the process goes to step S12.

(4) Generate a new image (q = 50).
The data size at this time is set to s50 (step S
7). (5) Compare s50 with the target data size and find the difference Δ
(Steps S9 and S10). If the current difference is larger than the previous difference, the image quality parameter is replaced with the previous value (step S11), and the process goes to step S12. If the current difference is smaller than the previous difference, step S
Go to 12.

(6) In step S12, the image quality parameter change value q Step is changed to the minimum value q St of the image quality parameter change value.
Compare with ep _- min (step S12), and q Step <q Step
_In the case of -min, in step S13, the current image quality parameter is used as an estimated value corresponding to the target size. If q Step> q Step _- min,
Returning to step S4, as described above, the initial value of q Step is added to q (if the target data size is smaller, subtract q Step), q step is changed to を, and the above processing is performed. repeat. By repeating the above processing, the data size can be made close to the target size as shown in FIG.

The proxy server 12 in the overall flow operates as follows. [1] The current line speed is obtained from the client 11. [2] An optimal image quality parameter q (quality factor) is obtained from the line speed in accordance with the above processing procedure. [3] The image quality parameter and the image requested by the client 11 are provided, and the quality change processing of the JPEG image is performed by the image quality change function 12a, thereby obtaining a desired image (a reduced quality). Proxy server 12
Then, the image quality of the image is changed according to the line speed. Basically, the target image is considered in JPEG, but the GIF image is
Conversion to EG is also included as one function. In the case of a JPEG image, a q factor (quality factor), which is a parameter for controlling the image quality when creating the JPEG image, is specified.

The quality factor controls the image quality as well as the bit rate. I mean
Decreasing the quality factor lowers the image quality, but also lowers the bit rate. That is, since the data size can be reduced, the transmission time can be reduced. Since the relationship between the quality factor of JPEG and the data size of an image depends on the image, it is difficult to show a universal relationship that applies to all images, but as an example, the quality parameter and bpp (bit / bit / pi
xel) is shown in FIG.

In the evaluation using a certain sample image, q = 7
When the image created in step 5 is dropped to q = 30, the data size of that image is halved. Further, if q = 10, it is further reduced to １ ／. Here, assuming that the original data size is 100 kB and the line speed is 2 kB / s, it usually takes 50 s for transmission, but when q = 30, 25 s and q = 10
In this case, the transmission time can be reduced to 13 s. Regarding the image quality, even if q = 30, there is not much difference. q =
In 10, the deterioration can be recognized as such, but there is no problem in recognizing the image.

Changing the quality factor depends on the user's preference. FIG. 6 shows the user preferences for changing the image quality, that is, the configuration of the setting screen. 1. , 2. In, the setting for controlling the image quality and shortening the transmission time is performed. 1. Select "Yes" to activate the image quality control. If you want to change the quality factor, you have another option. For wireless lines,
When the line speed changes, the image quality also decreases according to the decrease in the line speed. This corresponds to the user preference 4. in FIG. Activate by selecting "Yes" in. In this case, an access feeling is obtained virtually as if the connection was established at the maximum line speed, but the image quality fluctuates depending on the state of the wireless line. This function is realized by having the client tell us the line speed before the image quality change processing.

FIG. 7 is a diagram showing a second embodiment of the present invention. In the present embodiment, the proxy server 12 has user-based profile information, and when an image is registered as profile information, the quality of the image, that is, the data amount is reduced and transmitted to the client. 7, the same components as those shown in FIG. 2 are denoted by the same reference numerals. In this embodiment, the proxy server 12 is provided with a profile information table 12b, and the profile information table 12b Is registered with an identification name (URL) of an image that the user desires to transmit with reduced quality, that is, data amount. An example of such an image is advertising information, for example. The information registered in the profile information table is not originally desired by the user on the receiving side, but is automatically entered by the information creator or the system and incorporated into the hypertext, so that the transmission time is reduced. You can drop the quality to make it faster.

In this embodiment, the proxy server 12
Works as follows. When there is an image request from the client 11, an image request signal is sent to the proxy server 12 via the communication line 15. The proxy server 12
If the requested image is not stored in the cache 14 as described above, the image request is notified to the server 13 having the original image via the communication line 15. Then, the image information sent from the server 13 is stored in the cache 14 and sent to the client 11. If the requested image is stored in the cache 14, the image information stored in the cache 14 is transmitted to the client 11.

When transmitting the image information, the proxy server 12 refers to the profile information table 12b. If the image information requested by the client 11 is previously registered in the profile information table 12b, the proxy server 12 reduces the quality of the image, that is, the data amount, and transmits the image to the client as described above. Further, the image information created by changing the quality is stored in the cache 14 together with the original image. In response to an image transmission request received from another client according to the transmission speed, if there is any cached image information that matches the required quality from the client, the cached image information is directly sent to the client 11. send.

FIG. 8 is a diagram showing a third embodiment of the present invention. In the present embodiment, the image information is divided into a low-frequency component capable of displaying a rough image and a high-frequency component capable of displaying a fine image by being added to the image information. By displaying rough images and sending high-frequency components later as necessary, the line utilization efficiency is improved.

In FIG. 8, the same components as those shown in FIG. 2 are denoted by the same reference numerals. In the present embodiment, the proxy server 12 is provided with a frequency component separation function instead of the image change function 12a. A function 12c is provided, and the image information is separated into a low frequency component and a high frequency component by the frequency component separation function 12c. FIG. 9 is a diagram showing an example of the configuration of the frequency component separation function. Frequency component separation function 12
As shown in FIG. 3, c is a frequency component separation unit 121 that separates image information into frequency components, a separation image storage unit 122 that stores images of the separated frequency components, and a separation image storage unit 122 that stores the information. And a selection unit for selectively transmitting the image of each frequency component.

In this embodiment, the proxy server 12
Works as follows. Client 1 as described above
1 receives an image request, the image request signal is transmitted to the communication line 15.
Via the proxy server 12. Proxy
If the requested image is not stored in the cache 14, the server 12 notifies the image request to the server 13 having the original image via the communication line 15. Then, the image information sent from the server 13 is stored in the cache 14 and sent to the client 11. If the requested image is stored in the cache 14, the image information stored in the cache 14 is transmitted to the client 11. When transmitting the image information, the proxy server 12 separates the image information into a low-frequency component and a high-frequency component that can display a fine image by adding the image information, and stores the separated image by the frequency component separating function 12c. The information is stored in the unit 122. Then, the low-frequency component is sent to the client 11 first to show a rough image, and the high-frequency component is sent later as necessary.

As a trigger for transmitting the high frequency component, the signal can be transmitted automatically using the idle time of the line, or can be transmitted at the request of the user. For example, the high-frequency component is sent to the client 11 as follows. (1) The proxy server 12 sends the low-frequency component of the image in advance to show the user a rough image, and then automatically removes the high-frequency component of the image when a line that does not send other data is available. To show the user a fine image. (2) The proxy server 12 sends the low-frequency component of the image in advance to show the user a rough image, and then, after the user views the coarse image, responds to the user's request, and thereafter the high-frequency component of the image. To show a fine image.

[0034]

As described above, according to the present invention,
The following effects can be obtained. (1) Since an image whose image quality has been changed or an image separated into frequency components is transmitted according to the line speed between the proxy server and the client and its fluctuation, the line speed and its fluctuation can be absorbed, and the user A constant sense of access can always be given to the user. For this reason, even when accessing from a low-speed line or a line where the situation fluctuates such as wireless communication, transmission within an appropriate time can be performed without significantly deteriorating transmission delay for access to image data. It becomes possible. (2) The cached image is cached in the proxy server together with the deteriorated image. If any of the cached images matches the quality required by another client, the cached image information is sent to the client. Can be sent, and the time required for image processing can be reduced. (3) Registering, in the proxy server, images that the user wishes to transmit with reduced quality, such as advertisement information, and images that are not so important, and transmitting the image information with reduced quality. And the time required for image transmission can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating a configuration of a system according to a first exemplary embodiment of the present invention.

FIG. 3 is a flowchart illustrating an outline of image quality conversion processing in a proxy server.

FIG. 4 is a diagram illustrating a relationship between a data size and a q factor.

FIG. 5 is a diagram showing a relationship between a q factor and bpp (bit / pixel).

FIG. 6 is a diagram illustrating an example of a setting screen for changing image quality.

FIG. 7 is a diagram showing a configuration of a system according to a second example of the present invention.

FIG. 8 is a diagram showing a configuration of a system according to a third example of the present invention.

FIG. 9 is a diagram illustrating a configuration example of a frequency component separation function.

[Explanation of symbols]

 1 Client 1a Line Notification Function 2 Proxy Server 2a Image Change Function / Frequency Component Separation Function 2b Profile Information Table 3 Server 4 Cache 11 Client 11a Line Notification Function 12 Proxy Server 12a Image Change Function / Frequency Component Separation Function 12b Profile Information Table 12c Frequency component separation function 13 Server 14 Cache 15 Communication line

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04L 12/58

Claims (5)

[Claims] An adaptive transmission control system in an information communication network for transmitting image information stored in a server to a client via a proxy server via a wireless line, wherein the client has a line speed detection function. When the proxy server has an image quality change function and transmits image information of the server from the proxy server to the client, the proxy server detects the line speed between the proxy server and the client detected by the line speed detection function. An adaptive transmission control system characterized in that the quality of an image transmitted to a client is changed by the image quality changing function according to a change in the speed of a wireless line. 2. An adaptive transmission control system in an information communication network for transmitting image information stored in a server to a client via a proxy server through a low-speed line, wherein the client has a line speed detection function. The proxy server is provided with an image quality change function, and the proxy server checks in advance the line speed between the proxy server and the client detected by the above line speed detection function, and sends the server image information to the client. An adaptive transmission control system, wherein a quality of an image transmitted to a client is changed according to a line speed between the proxy server and the client during transmission. 3. A proxy server, comprising: an original image;
Caches and stores several types of image information created by changing the quality of the original image according to the transmission request from the client, and responds to image transmission requests received from other clients according to the transmission speed. 3. The adaptive transmission control system according to claim 1, wherein the cached image information is sent to the client when the cached image information matches the quality required by the client. 4. A proxy server is provided with a profile information table for storing profile information for each user, the proxy server refers to the profile information table, checks the identification name of the image information requested by the user, and notifies the client When the image to be transmitted is an image in which the user has registered in the profile information table in advance that the image quality is to be reduced, the image quality is reduced and transmitted to the client regardless of the line speed. The adaptive transmission control system according to claim 1, 2 or 3, wherein 5. An adaptive transmission control system in an information communication network for transmitting image information stored in a server to a client via a proxy server, wherein the client has a line speed detection function and a proxy server. Is provided with a frequency component separation function of image information, and when transmitting the image information of the server from the proxy server to the client, the proxy server sends the low frequency component of the image separated by the frequency component separation function first to be rough. Show the image to the user, and then when the line is free,
Alternatively, an adaptive transmission control system characterized by transmitting a high frequency component of the image to show a fine image in response to a user request.