Autonomic MPEG-4

Adaptation Policies

1. Ranking Policies
   The content adaptation operation may yield multiple MPEG-4 compositions and in multiple representation formats that satisfy the given client and network adaptable parameters. A set of resulting MPEG-4 objects are called a match list. A match list will be rank scored according to the following policies.
   1. Response Time vs. Best-fit Tradeoff
      If a match list consists of multiple MPEG-4 representation formats, preference is given to the format that results in the fastest end-to-end response time.

      Example 1:

      If an MP4 file format exists, do not encode the XMT even if the latter may yield a better fit by other metrics.

   
   
   2. Fidelity
      For a given adaptable parameter and a corresponding match list, preference is given to the object that produces the best audio-visual experience for the user.

      Example 1:

      Large screen size over small size.

      Example 2:

      High bit rate over low bit rate.

   
   
   3. Prioritization of Adaptable Parameters
      In ranking objects in a match list, some parameters are given higher priorities than others. The parameters can be assigned different weights, or higher priority items may veto lower ones.

      Example 1:

      The bit rate overrules the screen size. If object A has a higher bit rate but smaller screen size than object B, object A is preferred.

      Example 2:

      Larger screen size is preferred over color depth.



2. Adaptation Control Point Decision Policy
   Depending on configurations, an end-to-end MPEG-4 content delivery system involves a pipeline of several system components ranging from the content encoder, application server, streaming server to the client device, each of which may support its own set of adaptable parameters. Furthermore, the sets may overlap resulting in a conflict when components are brought online, or their adaptability characteristics are dynamically changed. This policy sets a guideline for conflict resolution.

   Example:

   The application server and the streaming server can perform the same bit rate adaptation. One policy is to defer adaptation downstream. Therefore, the application server delegates the adaptation task to the streaming server.



3. Streaming Service Preference
   MPEG-4 supports multiple streaming services -- methods and formats. Currently, the supported services include RTP, HotMedia over HTTP, and Flexible-multiplex over HTTP.

   Example preference list:

   Flexible-multiplex; HotMedia; RTP.



4. Access Speed vs. Storage Requirement Tradeoff
   If we are to assume that contents are accessed repeatedly, we want to save the results of encoding and adaptation to improve access speed at the expense of large storage requirements. This policy sets decision parameters for the tradeoff.



5. Predictive Content Push
   We monitor the content access patterns and estimate encoding cost and storage requirements. Based on that information we may pre-adapt the contents with high probability of access. The contents can also be pushed to an intelligent distribution and caching system.

Monitoring

1. Client Monitoring
   
   

     Device and network conditions

   end-to-end bandwidth estimate
   screen size and color depth
   device playback capability
   device decoding capacity
   scalable MPEG-4 stream support level

   
   
   

     User preferences

   language
   captions
   overdub or subtitle

   
   
   

     Accessibility needs

   vision impairments
   deaf/hard of hearing
   cognitive disability
   limited hand use
   mobility limitation
   speech and language disabilities



2. Server Monitoring

    

   content access events
   encoding and composition times
   storage utilization
   streaming server availability and adaptability

Plan

In the context of MPEG-4, an execution plan is a sequence of actions for encoding, composing, converting, and delivering customized MPEG-4 content to the end-user device.

Example 1:

1. Select a suitable streaming server.
2. Encode, compose, or convert MPEG-4 content to a suitable target format as needed.
3. Publish the target format to the streaming server.
4. If desired, remove the target and intermediate contents from the server.