Multimedia Authoring System

Multimedia Authoring Systems are designed with two primary target users: They are

• Professionals who prepare documents, audio or sound tracks, and full motion video clips for wide distribution.
  
• Average business users preparing documents, audio recordings, or full motion video clips for stored messages or presentations.
  

The authoring system covers user interface. The authoring system spans issues such as data access, storage structures for individual components embedded in a document, the user's ability to browse through stored objects, and so on. Most authoring systems are managed by a control application. The authoring system is called in when a user selects an EDIT function in the control application menu.

The control application managing the authoring system must determine storage location and compression format according to the type of multimedia object, the capturing equipment in use, and the software drives and compression standards supported by the authoring system. The control application must also be designed to handle sufficient cache storage to manage compressed as well as decompressed objects before they are dispatched to other multimedia server objects.

Design issues for multimedia Authoring

Enterprise wide standards should be set up to ensure that the user requirements are fulfilled with good quality and made the objects transferable from one system to another. So standards must be set for a number of design issues:

• Display Resolution.
  
• Data formula for capturing data.
  
• Compression algorithms.
  
• Network Interfaces.
  
• Storage Formats.
  

Display Resolution

Display Resolution should be at various levels since user's requirement differs accordingly. For example, for television, people will watch it at distance of atleast 10 to 15 feet's away. But in the case of computer (i.e. Desktop), people will watch only at the distance of 12-18 inches away. So, display resolution must be more than for TV. So we should set the display resolution as per user's requirement. In a large organization, there are a number of different display types with large variations in resolution and display technologies. Hence, the display resolution becomes an important consideration. A number of design issues must be considered for handling different display outputs.

They are:

• Levels of standardization on display resolutions.
  
• Display control standardization.
  
• Corporate norms for service degradations.
  
• Corporate norms for network traffic degradations as they relate to resolution issues.
  

Setting norms will be easy, if the number of different work station types, window managers, and monitor resolutions are limited in number.

File Format and Data Compression Issues

There are varieties of data formats available for image, audio and full motion video objects. Since the varieties are so large, controlling them becomes difficult. So we should standardize on a single format. Instead, we should select a set for which reliable conversion application tools are available. 

• Another key design issue is to standardize on one or two compression formula for each type of data object. For example for facsimile machines, CCITT group 3 and 4 should be included in the selected standard. Similarly for full motion video, the selected standard should include MPEG and its derivatives such as MPEG 2.
  

• Standardizing protocols in WAN's is essential to ensure that multimedia objects can be transformed from one LAN via a WAN to another LAN without loss of information. All hubs, routers, switches, etc.must be standardized.

• Storing and retrieving of very large objects is an important consideration. Storing should be done quickly and retrieving should be done efficiently. 

• While doing storage, it is useful to have some information about the object itself available outside  the object to allow a user to decide if they need to access the object data.
  

Types of Attributes

• Comparison Type 
  
• Size of Object 
  
• Object Orientation
  
• Data and Time of Creation
  
• Source file name
  
• Version Number
  
• Required software application to display etc..
  

Sevice Delegation policies

Setting up corporate norms for network traffic delegation is difficult as they relate to resolution issues. To address these design issues, several policies are possible.

They are: 

(i) Decline further requests with a message to try later.

(ii) Provide the playback service but at a lower resolution.

(iii) Provide the playback service at full resolution but, in the case of sound and full motion video, drop intermediate frames.

Design Approach to authoring

Designing an authoring system spans a number of design issues. They include:

1. Hypermedia application design specifies
   
2. User Interface aspects
   
3. Embedding/linking streams of objects to a main document or presentation.
   
4. Storage of and access to multimedia objects.
   
5. Playing back combined streams in a synchronized manner.
   

A good user interface design is more important to the success of hypermedia applications. User interface presents a window to the user to control storage and retrieval, to insert objects in the documents and to specify the exact point of insertion, and to index marks for combining different multimedia streams and rules for playing them back. The authoring system must allow playing several streams in a coordinated manner to produce a final product.

Dedicated Authoring Systems

Dedicated Authoring Systems are designed for a single use and generally for single streams. Designing this type of authoring system is simple, but if it should be capable of combining even two object streams, it becomes complex. The authoring is performed on objects captured by the local video camera and image scanner or an objects stored in some form of multimedia object library. in the case of dedicated authoring systems, users need not to be experts in multimedia or a professional artist. But the dedicated systems should be designed in such a way that it has to provide user interfaces that are extremely intuitive and follow real-wold metaphors. A structured design approach will be useful in isolating the visual and procedural design components.

Timeline Based Authoring

In a Timeline Based Authoring system, objects are placed along a timeline. The timeline can be drawn on the screen in a window in a graphic manner, or it is created using a script in a manner similar to a project plan. But the user must specify resource object and position it in the timeline. On playback the object starts playing at that point in the time scale. In most timeline based approaches, once the multimedia object has been captured in a timeline, it is fixed in location and cannot be manipulated easily. So, a single timeline causes loss of information about the relative time lines for each individual object. Editing a component causes all objects in the time line to be reassigned because the positions of objects are fixed in time, only in sequence. Copying portions of timeline becomes difficult because it is difficult to predict the start of new section. This limitation of using timeline approach can be overcome by defining time relations directly between objects.

Structued Multimedia Authoring

A Structured Multimedia Authoring system consists of two stages:

1. The Construction of the structure of presentation.
   
2. Assignment of detailed timing constraints
   

A successful structured authoring system must provide the following capabilities for navigation though the structure of the presentation.

1. Ability to view the complete structure.
   
2. Maintain a hierarchy of objects.
   
3. Capability to zoom down to any specified component.
   
4. View specific components in part or from start to finish.
   
5. Provide a running status of percentage full of the designated length of the presentation.
   
6. Clearly show the timing relations between the various components.
7. Ability to address all multimedia types, including text, image, audio, video and frame based digital images.

The author must ensure that there is a good fit within each object hierarchy level. The navigation design of authoring system should allow the author to view the overall structure while examining a specific object segment more closely. The design of the views must show relevant information for a specific view.