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Building Continuous Media Applications .

Kouki Oohira

Scho ol of Information Science,

Japan Advanced Institute of Science and Technology

February 14, 1997

Keywords: continuous media data , to olkit ,StreamManager .

Background

Nowadays,it makes rapidprogress that Information Science, Electronics , and Physics.

We can buy personal computer which have enough computing resource and environ-

ment to pro cessing for movie and sounds . The case in point is Video Playerand Video

Conference software such asCU-SeeMee.

In this research , we concentrate our discussion on processing for Continuous Media

Data . We studyof Processing forall of Continuous Media Datasuchas movie data.

ContinuousMediaDataiscontinuousdataunderthereal time. But,computerdivide

the dataintomomentaryphenomenonwhichcallsamples. Forinstance,itisp eriodically

observation, divisionandpreservationthatpro cessingofincorp orationcontinuousmedia

data into a computer . This processing makes many data which divided under the real

time in Application . So application must processing many data one after another. If

stagnate a part of processing ,it makes omissionof data . This break waste the data .

In short , continuous mediadata depend on real time, and processing forContinuous

media data also depend on real time. These processing is dicult for implementation.

So, it need a system whichhelp construct toContinuousMedia Application.

The related works pay attention to handling continuous media data . An example is

ContinuousMediaServerwhichprocessingcontinuousmediadata inplaceof application.

If application want to handle continuous media data, it may only request processing

mediadata tocontinuousmedia server. In this system,application programmerdoesnot

have to construct data handler which need real time processing. However, this system

needreconstructingtheserverwhenapplicationprogrammerneedsnewfunction. So,this

structure do es not have enoughextensibility.

Media Tool kit. This system was presented for library to link with program which was

wrote by application programmer. This to ol kit have divided handler for continuous

media data. These handlercalled Modules. Application programmercan makestructure

ofmediadatahandlerwithjoiningmodules. Ifapplicationprogrammerneednewfunction,

programmermaycreateanewmoduleunderthe moduleclass,andappendanewmodule

totool kit. After all,if applicationprogrammer need new function,programmer doesnot

need reconstruct allof tool kit suchas continuousmedia server.

But,this structurehavenew problem. Continuousmediadata willowbetweenmod-

ules,becausemediadatahandlerwasdividedintomodules. Applicationprogrammermay

requesthandlingtoaserverunderthecontinuousmediaserver. Forexample,application

programmer's command (start , stop ,and so on...) may request to unique server. But,

applicationprogrammerneedselectandrequestsomemodulesfromoutofmanymodules,

because handlerwas divided into many modules. Soapplication programmer's work will

larger underthe continuous mediatoolkit than underthe continuous mediaserver.

We mustprop ose a new structure which have enough exibility and extensibility for

handling to continuousmedia data .

Handling continuous media data have another problem. In computers, continuous

media data consistof many samples ,because toexpress a continuous phenomenon.

Continuous mediaapplicationmusthandle largedata underarequest fordependence

with real time. So ,handling continuous media data will consume large CPU resource.

If CPU resource is too short ,continuous media application will not satisfy a request for

dependencewith realtime. Continuousmediaapplicationneedamechanismofwatchfor

CPU usageand autonomouscontrol for reduct handling.

1 Our Goal

We examine problem for continuous media application in the ab ove, and we propose a

structure for handle continuousmedia data.

Weconsiderthedesignofcontinuousmediaapplication,producttoolkitforsupportof

constructionof continuousmediaapplication,and evaluatecontinuousmediaapplications

under the tool kit.

In thisresearch, weuse videodata togiveanexampleofcontinuousmediadata. But,

we construct a toolkit for allof continuous media data.

2 Outline

VuSystem supplied structure of continuous media application,which divide up into \In-

band(handlemedia data)"and \Out-of-band(use toIn-band)". Continuous mediaappli-

cation may construct Out-of-band,because In-band was already implemented by VuSys-

tem.

In-band was divided to small handlers which call Modules. In-band modules consist

construct a large handler for complex pro cessing, you could construct the handler by

joining Modules. Still more, if you needed to new handler by new specications, you

could construct the handler by default module's template.

This system abstracts handling continuous media data from continuous media appli-

cation,so this system reduce application programmer's work. However,this system does

not control owof continuous mediadata . It isvery diculthandling pluralcontinuous

media data with inter-media synchronization underthe VuSystem.

So, we prop ose new structure,that divided into \In-band",\Stream Manager", \Out-

of-band" . In-band component handles continuous media data, Out-of-band component

handles user interfaceand so on.

Stream Manager manages the conguration of in-band modules, and providesprimi-

tivesforcontrollingin-bandmodulesfromanout-of-bandcomponentasModule,Stream,

Link, Command, Delivery, QosControl, SyncControl. Each media stream has its own

stream manager for controlling the b ehavior stream . Stream Manager process follow

employment.

It presentsobjectsfor constructing continuous media applications .

It presentsabstraction of mediadata,which calledStream .

It presentscommands tocontrol Stream .

It support for inter-stream synchronization,dynamic QoS control.

Weconstructcontinuousmediato olkitwhichcanimplementadvancedstreamcontrols

as dynamicQoS(Quality of Service) control,inter-streamsynchronization.

This applicationmay watchfortoo matchof usingCPUresource, and reduceQuality

of Service for purpose of avoid over load and data drop. Data drop is the worst case in

continuous media applications, because data drop raise very large jitter and deteriorate

data. So we must media scaling ,and reduce CPU usage for suitable processing. In this

tool kit , we choice point to scaling as video frame rate which mean processing number

of frame p erseconds . Reducing frame rate isvery eectiveness,because directly reduce

the numb erof processing frames .

Conclusion

Weconsiderthe designofcontinuousmediaapplicationandproducttoolkit. Thistoolkit

support follow points.

Thissystem managesdividedmediadata handler. Wecall dividedhandlerModule

.Application programmercan construct complexhandler fromconnecting modules.

StreamManagerabstractIn-bandstructure. Applicationprogrammerbenetfollow

{ Stream Manager can setpolicyof delivery of commands.

{ Stream Manager supp ort callingback for autonomous controls.

This system construct with function of real time OS for time dependent operation

and system resource reservation.