KR100388492B1 - Method for dynamic frame selection scheme on the video on demand - Google Patents

Abstract

The present invention utilizes a dynamic frame selection method to effectively provide a video cassette recorder function that can optimize traffic generation, thereby minimizing service quality deterioration according to network conditions and at the same time providing a VCR function. In order to provide a dynamic frame selection method in video on demand to dynamically adjust traffic while dynamically adjusting, a first method of switching a current user session to an interactive service mode according to a video cassette recorder (VCR) function request from a user. step; A second step of checking a traffic situation by calculating an available bandwidth capacity with the switched service condition and total bandwidth capacity; A third step of determining whether to provide a service according to the traffic situation; Determining a corresponding frame selection parameter according to whether the service is provided and selecting a dynamic frame for the video selected by the determined selection parameter; And a fifth step of transmitting a selection frame by variably adjusting an amount of traffic and a quality of service generated according to the determined frame selection parameter, and used for an on-demand video system.

Description

Method for dynamic frame selection scheme on the video on demand}

The present invention relates to a dynamic frame selection method in video on demand and a computer readable recording medium recording a program for realizing the method, in particular, a video in an on-demand video service through MPEG (Moving Picture Expert Group) video. By using dynamic frame selection method to effectively provide Video Cassette Recorder (VCR) function, it minimizes service quality deterioration according to network situation and dynamically adjusts service quality when VCR function is provided. A dynamic frame selection method in video on demand for variably controlling traffic and a computer readable recording medium having recorded thereon a program for realizing the method.

VCR functions such as Fast Forward and Fast Reverse (FF) in video-on-demand services are generally achieved through separate additional files, and the amount of bandwidth used is significantly higher than normal playback. . Therefore, while minimizing the need for such additional storage device, the traffic generated while dynamically adjusting the quality of service when providing the VCR function is controlled.

In general, the methods used to provide VCR functions on MPEG video are client-driven and server-driven. Here, as a client-driven method, assuming N times faster playback, when the server transmits a frame to the client at an N times speed, the client may play back at an N times faster refresh rate. This method has the problem of exerting a high load on the network and the client system while the reproducing continuity is excellent.

One way to solve this problem is to transmit only I frames of compressed video. This method uses the frame pattern feature generated when using a variable compression method such as MPEG video. It is noted that an intra-frame, which is a frame compressed to be independently reproduced, is generated at a constant interval (GOP). It is to use. However, this method is easy to implement and has excellent continuity of playback. However, since the amount of data is relatively large compared to other frames (B and P frames), there is a large demand for additional disk capacity or network resources in actual service.

Therefore, when using the conventional method, not only a lot of load is placed on the server and the client, but also a large share of network resources.

The present invention has been proposed to solve the problems described above, and uses a dynamic frame selection method to effectively provide a video cassette recorder (VCR) function that can optimize traffic generation. By minimizing the deterioration of the quality of service according to the network situation, the dynamic frame selection method and the program for realizing the above method are recorded. Its purpose is to provide a computer readable recording medium.

1 is an exemplary configuration diagram of an on-demand video system for dynamic frame selection to which the present invention is applied.

2 is a flow diagram of an embodiment of a method for dynamic frame selection in video on demand according to the present invention.

Figure 3 is a detailed diagram of an embodiment of a dynamic frame selection method according to the present invention.

4 is a detailed flowchart illustrating an embodiment of a dynamic frame selection process provided according to a playback mode in a dynamic frame selection method according to the present invention.

* Explanation of symbols for the main parts of the drawings

11: MPEG Video 12: Frame Information DB

13: VCR Video 14: Session Manager

15: stream selection module 16: bandwidth allocation / renegotiation module

17: video transmission module

In order to achieve the above object, the present invention provides a dynamic frame selection method applied to an on-demand video system, comprising: a first step of switching a current user session to an interactive service mode according to a video cassette recorder (VCR) function request from a user; ; A second step of checking a traffic situation by calculating an available bandwidth capacity with the switched service condition and total bandwidth capacity; A third step of determining whether to provide a service according to the traffic situation; Determining a corresponding frame selection parameter according to whether the service is provided and selecting a dynamic frame for the video selected by the determined selection parameter; And a fifth step of transmitting a selection frame by variably adjusting an amount of traffic and a quality of service generated according to the determined frame selection parameter.

The present invention also provides an on-demand video system with a processor, comprising: a first function of switching a current user session to an interactive service mode in response to a video cassette recorder (VCR) function request from a user; A second function of checking the traffic situation by calculating the available bandwidth capacity with the switched service condition and the total bandwidth capacity; A third function of determining whether to provide a service according to the traffic situation; A fourth function of determining a corresponding frame selection parameter according to whether the service is provided and selecting a dynamic frame for the video selected by the determined selection parameter; And a computer-readable recording medium having recorded thereon a program for realizing a fifth function of transmitting a selection frame by variably adjusting the amount of traffic and the quality of service generated according to the determined frame selection parameter.

The present invention relates to a method for providing an effective interactive service for MPEG video transmission in an on-demand video service. By using a dynamic frame selection technique, a VCR function is implemented while maintaining a frame refresh rate of a client. This method also utilizes the remaining frames that are contiguous in an I-frame, so that it has an optimal bandwidth utilization in a situation where a large bandwidth is required such as fast playback.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exemplary configuration diagram of an on-demand video system for dynamic frame selection to which the present invention is applied.

As shown in FIG. 1, the video-on-demand system is basically divided into a session manager 11, a stream selection module 12, a bandwidth allocation / renegotiation module 13, and a video transmission module 14. The session manager 11 distinguishes playback requests from the user (normal playback and VCR playback such as FF / FR), and the stream selection module 12 applies normal playback or dynamic frame selection techniques according to the playback request. It serves to transmit selection (the method for dynamic frame selection follows the procedure of FIG. 4 to be described later). In this way, resources are allocated through the bandwidth allocation / renegotiation module 13 for the selected stream and the stream is transmitted through the video transmission module 14.

2 is a flowchart illustrating a method of selecting a dynamic frame in video on demand according to the present invention.

As shown in FIG. 2, the dynamic frame selection is divided into a normal service mode and an interactive service mode. In the interactive service mode, a frame is transmitted by applying a dynamic frame selection method according to traffic conditions. In this case, the frame selection is performed using a frame information database extracted from the MPEG video.

First, in order to provide a video transmission service (201) requires the user's VCR function (FF or FR function), according to the service mode (202) to switch to the normal service mode to perform the normal service (203) traffic conditions After checking (204), the frame is transmitted (205).

On the other hand, the current user session is switched to the interactive service mode according to the VCR function (FF or FR function) request from the user (206).

Subsequently, the system checks the traffic situation by calculating the available bandwidth capacity based on the service status of the entire user and the total bandwidth capacity and the like (207), and determines whether to provide a service (admission control) (208).

Then, if the user request is accepted, the dynamic frame selection parameter is determined according to the service policy already determined (the method of determining the frame selection parameter will be described later with reference to FIG. 2). In frame is selected (209). In this case, the frame selection is performed by referring to a frame information database that is already made offline.

Subsequently, the selected frame is transmitted according to the type of the requested VCR function (210). That is, the frame selection and transmission functions vary according to the type of VCR function. The FF function can be selected and transmitted dynamically, whereas the FR cannot reverse play due to the characteristics of MPEG video. Therefore, the FR function is serviced using the stream data already generated.

As such, the dynamic frame selection is performed during the service, and the amount of traffic generated and the quality of service can be variably adjusted according to the frame selection parameter (see FIG. 4).

The operation of the dynamic frame selection method in video on demand will now be described in detail.

3 is a detailed diagram illustrating a dynamic frame selection method according to an embodiment of the present invention, and includes a group of picture (GOP) selection and a frame (picture) selection within a selected GOP in an MPEG video structure. For reference, MPEG video has a hierarchical structure. First, video sequences exist in groups of each frame (GOP), and each GOP exists in several consecutive frames. In this case, three types of frames are defined in MPEG video, and are composed of I frames, B frames, and P frames. I-frames are independent frames, and because they are compressed only by the frames themselves, they can be reproduced by themselves. In the case of B frames, they can be restored by bidirectional interpolation with a later P frame. In the case of a P frame, the frame is predicted from the preceding I frame.

The dynamic frame selection method in the present invention intends to use this structural characteristic.

As shown in FIG. 3, the dynamic frame selection method defines G as the size of the GOP, which means the number of frames before the I frame and the next I frame. In this case, for services such as fast playback, instead of transmitting only I frames, β frames are selectively transmitted within the selected GOP while skipping the GOP at α predetermined intervals. This method can significantly reduce the amount of traffic generated simultaneously while maintaining the continuity of the frame by selecting the appropriate parameters.

For example, if the number of frames selected in one GOP is β, the frame pattern of the β frames is determined by ω, which is a distance between key frames. In the case of an I frame, one is necessarily selected, while a B frame and a P frame are flexible. This is because at least one P frame may be selected according to the distance variable ω between the I frame and the P frame. However, the selection of β must be selected so that it ends with P frame due to the characteristics of the MPEG sequence, so that B frames can be reproduced in the middle.

At this time, the number of selected I, B, P frames can be obtained as shown in Equation 1 below.

Then, the actual required traffic is obtained by the number of frames selected previously. First, the average bandwidth for each frame is used to determine the unit traffic generated in one GOP. That is, since average traffic information for I, B, and P frames can be known in advance before the service, it must be calculated online in real time during the service to remove the load. On the other hand, given the frame selection parameters α, β, the amount of traffic for fast playback depends on the number of frames selected. Traffic consumption for each frame can be obtained as shown in Equation 2 below. Thus, the obtained traffic amount is then used as information for bandwidth allocation.

here, Represents the average size of each frame.

As a result, by determining the appropriate parameters to provide the VCR function for a given video, the quality of service of the video is optionally determined. Here, the quality of service is due to the continuity of the frame, and the continuity of the frame is determined according to the frame selection parameter.

Next, a method of determining the reproduction speed will be described. Since the VCR providing function such as fast playback proposed by the present invention must selectively transmit a frame to be played while maintaining the original frame rate, it is inevitable to rely on the α and β values, which are frame selection parameters, to determine the double speed. In other words, the playback speed ( ) Can be obtained.

The above equation means the playback speed because a frame as much as β is selected while moving in a period of α with respect to a given GOP size. For example, the parameter for normal reproduction speed, i.e., 1x speed, becomes "DFSS (1, G)". This is because all GOPs are selected and all frames in the selected GOP are transmitted.

On the other hand, when the double speed is determined, both the continuity of playback and the optimality of bandwidth consumption must be satisfied for optimal service. However, as an assumption for considering optimal continuity, it is assumed that the continuity of reproduction may vary depending on the frame selection policy even at the same double speed. Under this assumption, the criterion for continuity is the deviation between frames caused by the selective frame transmission policy. For more accurate continuity measurements, the present invention uses standard deviation for the selected frames. That is, the standard deviation between the frames can be obtained as shown in Equation 4 below.

4 is a detailed flowchart illustrating a dynamic frame selection process provided according to a playback mode in the dynamic frame selection method according to the present invention. The playback speed and the quality of service may be determined using a frame selection parameter.

When providing on-demand video service, the VCR function generated by user's request should basically use two methods. That is, depending on the playback mode, there is a dynamic selection transmission method for the FF function and a transmission method using a separate reconstructed stream, while the reverse function of the dynamically selected frame is impossible due to the characteristics of the MPEG frame for the FR function. Only services through separate reconfiguration are possible. However, even in the case of FR service, dynamic selection and playback are not possible, but the configuration method for creating a separate stream file can be provided based on the dynamic frame selection policy of the present invention, thereby providing flexibility of frame reconstruction. Has advantages In addition, since dynamic frame selection for FF and transmission are basically made within the playable range, no reconstruction is required on the transmitting side or the receiving side, and the dynamically selected frame is an I frame. Compared to other data sources, it generates less traffic because it contains B and P frames with a relatively small amount of data, which can be selectively controlled, which minimizes VBV (Video Buffering Verifier) constraints. Transmission by frame selection may increase the load on the server when providing a multi-user service, but this may be solved by a high performance disk).

As shown in FIG. 4, in the regeneration mode (401) and in the fast regeneration (FF) state (402), the frame information is extracted from the frame information database to determine the selection parameters (α, β) (403). Then select (α, β) the parameter based frame (404), calculate the traffic for the selected frame transmission (405), allocate bandwidth for the calculated traffic (406), and then verify that the bandwidth allocation is successful ( 406).

As a result, if the bandwidth allocation is successful, the selection frame is transmitted (408), and after performing the bandwidth renegotiation (409), the process is repeatedly performed from the process of checking whether the bandwidth allocation is successful (407). The process is repeated from step 407 to check.

On the other hand, according to the reproduction mode (401), if the fast reverse reproduction (FR) state (410), the frame information is extracted from the frame information database to determine the selection parameters (α, β) (411). Next, the process selects a stream 412, calculates traffic for the selected storage stream 413, and allocates bandwidth for the calculated traffic 406.

As such, the present invention uses a dynamic frame selection method in providing an on-demand video service, thereby minimizing additional storage requirements and serving without degrading the quality of service for the VCR function. In addition, since the method proposed in the present invention can be processed online, a bandwidth allocation service considering traffic conditions is possible. Accordingly, the present invention allows more users to be serviced by optimizing network resources used in providing on-demand video services supporting multiple users.

The method of the present invention as described above may be implemented as a program and stored in a computer-readable recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.).

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention does not deteriorate the service quality without rapidly increasing traffic even when providing an interactive service that can be generated during MPEG video transmission, that is, a VCR function. Serviceability can minimize bandwidth waste and service more users.

That is, according to the present invention, by using a dynamic frame selection method in providing an on-demand video service, not only can additional storage requirements be minimized but also service can be performed without degrading the quality of service for the VCR function, and the processing is performed online. Since it is possible to provide a bandwidth allocation service considering the traffic conditions.

Claims (7)

In the dynamic frame selection method applied to the video on demand system, A first step of switching a current user session to an interactive service mode in accordance with a video cassette recorder (VCR) function request from a user; A second step of checking a traffic situation by calculating an available bandwidth capacity with the switched service condition and total bandwidth capacity; A third step of determining whether to provide a service according to the traffic situation; Determining a corresponding frame selection parameter according to whether the service is provided and selecting a dynamic frame for the video selected by the determined selection parameter; And A fifth step of transmitting a selection frame by variably adjusting an amount of traffic and a quality of service generated according to the determined frame selection parameter; Dynamic frame selection method in video on demand comprising. The method of claim 1, The fourth step, Determining a state of a play mode of the video cassette recorder to determine the frame selection parameter; As a result of the determination in the sixth step, if the play mode is in the fast play (FF) state, the frame information is extracted through the frame information database to determine the frame selection parameters (α, β), and the frame based on the determined parameter is selected. A seventh step; Calculating a traffic for transmitting the selected frame and allocating a bandwidth for the calculated traffic; As a result of the determination in the sixth step, if the play mode is a fast reverse play (FR) state, the frame information is extracted from the frame information database to determine the frame selection parameters α and β, and the prestored stream data is selected. Tenth step; An eleventh step of calculating traffic for the selected storage stream and allocating a bandwidth for the calculated traffic; Dynamic frame selection method in video on demand comprising. The method according to claim 1 or 2, The dynamic frame, And a group of picture (GOP) selection in the MPEG video structure and a frame (picture) selection in the selected GOP. The method of claim 3, wherein The selected frame is, A dynamic frame selection method in video on demand, characterized by a predetermined form of a frame (I, B, P frame) as shown in the following formula. The method of claim 4, wherein The process of determining the frame selection parameters (α, β), The amount of traffic for fast playback is obtained depending on the number of selected frames, the traffic consumption for each frame is obtained by the following formula, and the traffic consumption is used as information for bandwidth allocation. How to choose a frame. The method of claim 5, The fast playback decision method, Determining the double speed by selectively transmitting the frame to be played while maintaining the original frame. ), And select frames as many as β while moving in a period of α with respect to the size of the GOP. On-demand video system with a processor, A first function of switching a current user session to an interactive service mode in accordance with a video cassette recorder (VCR) function request from a user; A second function of checking the traffic situation by calculating the available bandwidth capacity with the switched service condition and the total bandwidth capacity; A third function of determining whether to provide a service according to the traffic situation; A fourth function of determining a corresponding frame selection parameter according to whether the service is provided and selecting a dynamic frame for the video selected by the determined selection parameter; And A fifth function of transmitting a selection frame by variably adjusting an amount of traffic and a quality of service generated according to the determined frame selection parameter A computer-readable recording medium having recorded thereon a program for realizing this.