Interactive video distribution systems – User-requested video program system – Video-on-demand
Reexamination Certificate
1997-06-24
2002-07-23
Faile, Andrew (Department: 2611)
Interactive video distribution systems
User-requested video program system
Video-on-demand
C370S486000, C370S487000, C709S230000, C709S231000, C709S227000, C709S228000
Reexamination Certificate
active
06425130
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a video network server, and more particularly, to a video network server which selects a data transfer method or sets various parameters in accordance with status of a network system in a video network system for distributing sound/video image information to terminals.
BACKGROUND OF THE INVENTION
In recent years, with a progress of an image compression technology or a high-speed digital network technology, a wide variety of multimedia systems are increasingly constructed. In order to construct a multimedia network system by combining various equipments using a general computer and operate it smoothly, there is a need for a function for setting various parameters such as a time slot period and a time slot size or a number of allowable terminals according to status of the system and a function for reconstructing the system by resetting these various parameters in accordance with change of status.
A description is given of time slot management of the video server which decides setting of parameters with reference to FIG.
35
. Since it is difficult to distribute data to each terminal in a given ratio in a network system including a plurality of terminals only by reading and transferring the data sequentially, particularly in the case by using motion picture data of a large capacity, a time slot management method wherein data is sent to each terminal periodically for a given time is generally employed in the video network server. As shown in
FIG. 35
, the video server divides a given time interval, i.e, a time slot period uniformly and allocates the divided given time interval to each terminal. The time allocated to each terminal in a time slot period is a time slot size. The video server reads and transfers data to each terminal for each time slot size, thereby distributing data to a plurality of terminals in a given ratio. As shown in
FIG. 35
, data is sequentially read and transferred for each time slot size as follows: data A
1
to a terminal A→data B
1
to a terminal B→data C
1
to a terminal C (one time slot period)→data A
2
to the terminal A . . . . Conventionally, a time slot period and a time slot size are decided when parameters are set in the video server and then, on the basis of the time slot period and the time slot size, a number of allowable terminals or a response speed, i.e., the other parameters are decided.
A description is given of a function for setting various parameters for operating a system in a video net work server which distributes sound/video image information or the like to a plurality of terminals employed conventionally with reference to figures.
FIG. 34
is a diagram illustrating a prior art video network server. In the figure, a parameter computing means
901
is for computing parameters in accordance with a construction of a system. The construction of the system includes a number or performance of storage devices such as connected disks, or a capacity of a memory mounted in the system, for example. A parameter computation information holding means
902
is for holding information with which the parameter computing means
901
computes parameters. A parameter setting means
903
is for setting the parameters computed by the parameter computing means
901
in the system. Actually, various components such as a system construction checking means for checking the construction of the system are necessary, and are dispensed with herein.
The prior art server constructed above operates as follows in setting parameters. The parameter computation information holding means
902
holds information as to the construction of the system such as a type and a number of disks as storage devices or a capacity of a memory, or information for setting parameters such as a formula for computing parameters on the basis of the former information. The parameter computing means
901
computes parameters such as the time slot period and the time slot size in the time slot management mentioned above or the number of allowable terminals or the transfer speed in view of performance in accordance with the construction of the system, on the basis of the information which is held by the parameter computation information holding means
902
. The parameter setting means
903
sets the parameters which are computed by the parameter computing means
903
in the system.
The video network system is operated according to thus set parameters, and when the construction and status of the system change, parameters are reset following the procedure.
In the prior art server, when parameters are computed or set, it is possible to compute and set appropriate parameters in view of factors determined by the constructions of the system such as the number or performance of disks, but it is difficult to compute and set appropriate parameters in view of external and dynamic factors such as change of network operating form or change of network traffic (congestion). Therefore, if performance of the system with parameters initially set is degraded due to changes of the external factors, the system is operated without changing initialization, so that status of the network becomes worse than predicted and the server is overloaded, causing damaging effects on use of data. On the other hand, when status of the network is more preferable than predicted, performance of the system is degraded without making the best use of a reserve power of the system.
In the former case in which status of the system becomes worse than predicted, when traffic of the network increases or the network server is overloaded in reproducing motion picture data at the terminal, discontinuity of sound of data occurs or response of the server becomes worse, causing stop of reproduction.
In this case, since response of the server is worse than predicted, changing parameters of the system which decides response speed such as making the time slot period shorter than normal, limiting the number of allowable terminals must be performed, or when operating status is worse than described above, which is difficult to cope with by changing parameters, it is difficult to avoid the adverse effects without taking actions for reducing load of the server, such as performing switching of a method of obtaining data so as to transfer all data to terminals and reproduce the data at the terminals. As the method of obtaining data, a method wherein terminals receive data which is reproduced by the server itself using NFS protocol, for example, is less burdensome and desirable to the terminals. However, when status of the server or the network is worse and the adverse effects occur, it is desirable to transfer all data to the terminals and reproduce the data at the terminals using FTP protocol, since discontinuity of data is avoided.
In the latter case, the reserve power of the server is not made the best use of if status of the network is more preferable than predicted. For example, when the system is set to transfer all motion picture data to the terminals and reproduce the data at the terminals or the number of allowable terminals is limited severely allowing for congestion of the network or load of the server, it is impossible to reproduce data or to increase terminals to which data is supplied, with the server less overloaded than predicted. In another case, assuming that data requiring a fast transfer rate is used, when a time slot period is set according to its required transfer rate, use of data of required transfer rate which is lower than predicted causes time of no use in a time slot.
In the prior art server, in order to improve the above-described problem which may occur when status of the system changes, the user must interrupt operation of the system consciously and check its status, and then change parameters or various conditions.
In some cases, the user demands that discontinuity of sound or stop of reproduction be avoided with a number of terminals limited, while the user demands that many terminals be used with discontinuity of sound or stop of reproduction occurri
Akiyoshi Takashi
Asai Rieko
Faile Andrew
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P
Vu Ngoc
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