Context-Aware Adaptation: Overcoming Inconsistencies for Consistent Multimedia, Slides of Applications of Computer Sciences

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Context-aware Adaptation Of Multimedia Documents For Consistent Presentations

Basic Concepts

• What is a Multimedia Document?
• What is a temporal graph?
• Why should we improve the execution of a Multimedia Document?

Mechanisms in SMIL

• Casual: Actions that must be executed when some conditions are satisfied
• Ex: Image I starts….exhibition of a video V must stop
• Constraint:

Define restrictions that must be fulfilled during a presentation

• Ex: A video V must and its accompanying sound S must start and finish their presentations at the same time.

Inconsistencies with the Mechanisms

• Dead locks may occur due to a bad specification of a casual relationship.
• Ex: Consider two medias A and B. A can start only when B has achieved presentation. B can start only when A has achieved its own presentation.
• These type of inconsistencies are called intrinsic inconsistencies.

Mismatch

 A mismatch occurs when object data cannot be timely delivered.  The requested data may be hosted on different servers located over heterogeneous networks.  The time taken to recovery is called lag or latency.  For a consistent presentation a component called multimedia formatter is required  Computes the temporal graph and determines the feasible scenarios.  Also considers the unpredictable events.

Elastic Time Computation

• Formatter should select some objects time duration to be shrinked or stretched so that it reduces lags.
• Implementation of pre fetching mechanism becomes a necessity.
• But to generate a good presentation resource limitations should be taken into account.
• Within this context the authors proposed a context aware adaptation technique for SMIL encoded documents.

Brief summary of the Paper(contd…)

• At authoring stage algorithm produces different sub codes such that each one can be adapted in a specific context.
• At compile time, it makes it possible to assess whether the QOS of the presentation can be guaranteed or not.
• At runtime the algorithm can provide a mechanism to monitor the elastic time computation in case of a mismatch occurrence.

Related works

• Madeus
  • Authoring and presentation system for interactive multimedia documents
  • During compile time, formatter checks the intrinsic consistencies.
  • During exhibition, formatter computes the elastic time.
  • However Madeus formatter is based on a greedy solution and does not consider the qualitative result of presentation.

Overview of SMIL

• Synchronized Multimedia Integration Language
• Based on XML
• Sample Code

……… ………

Head and Body Tags

• Head :
  • It describes the layout of multimedia.
  • 1. Root Layout: size and part of the screen used to display.
  • 2)The Regions : Each region is a frame located inside the root layout and dedicated to display one or more as in the SMIL document.
  • A region is located by giving its dimensions and its position.
• Body :
  • Contains information referring to temporal behavior.

Context Aware Adaptation

Approach

• Adaptation of a multimedia document can be performed at compile or run time.
• Usually performed by the player.
• But such adaptations are energy and CPU consuming and so should be run on resource- limited devices.
• So, a proxy server is preferred. It recovers the user file and some context information. The formatter run by proxy checks the intrinsic consistency of the code by building a temporalDocsity.com

• Elastic time adjustments may also be enforced in order to guarantee a consistent presentation.
• Elastic runtime when applied in runtime permits to correct presentation mismatches caused by unpredictable conditions, like wait delays and user interactions.
• Usually a still object duration doesn’t make a great impact on the presentation content.
• Shrinking or stretching of a continuous media should be done with caution. Docsity.com

SMIL Request Pattern

• Pre fetching can be very effective if the client predicts the user patterns accurately.
• This pattern is characterized by the following parameters.
• Id(O): identifier of the media object O.
• Req(O): a URL associated with the media O; URL is used to request the data.
• Size(O): size of the file.

• Ps and Pe are two mappings that encode the conditioning relations specified.
• Ps(O’,O)=1 if the start of O is conditioned by start or end of O’.
• Pe(O’,O)=1 if the end O is conditioned by either start or the end of the object O’.
• These relations make it possible to check the intrinsic consistency of the document.
• Minbegin(O) and Maxbegin(O).