Tcl/Tk Workshop `95 - Saturday: Session 9

Joeseph Konstan (U. Minn)

Tcl Commands in a distributed Multimedia toolkit

• Multimedia: Coherent integration of media types
• Implemented with CMT
• Tcl Commands as a media type, with new "temporal" events
• Simple demo integrating text, images and simple stick-figure animations

Questions:

• Can this be used for general work-flow problems?
  • We haven't addressed that
• What about threading?
  • We haven't found it needed
• How do you synchronize time clocks over the network?
  • CMT has facilities to do this, and fine-grain resolution isn't required

Taming the Complexity of Distributed Media Applications

Frank Stajano, Rob Walker - Ollevetti Research

• Medusa, a Tcl/TK extension with heterogeneous distributed widgets, using incr-tcl
• Interfaced Medusa's thread model with TK's event system
• Media modules arranged as a process pipeline with control streams
• Used Smalltalk's Model-view-control model

Plug and Play with Wires(s)

Max Ott, NEC Usa

• Communication in distributed multimedia systems with mobile applications
• 3-d view of information sources and sharable, synchronous workspaces
• Need to manage the integration of synchronous and asynchronous event handling
• Lack of fine-grain control of thread scheduling is a problem for synchronization
• use Tk's update and after commands to manage synchronization
• wish list: Separate access to tk's event loop, support for X extension events

Questions:

• What is the event rate?
  • The problem is the communication with the X server for video
• Are the media module call backs "C" calls or "TCL" calls
  • C Call backs(?)
• The "honest" button problem is fixed in 4.0
  • In the beta I'm using I still had problems with it

RIVL: A resolution independent Video Brian Smith, Cornell University

by Johnathan Swartz

• Addition of images and video as first class TK widgets
• Supports image processing as a language primitive
• !command foo is equivalent to set foo [command $foo]
• Defined a set of primitives for operating on video sequences
• Example: Can cut/paste sequences, or apply image operations to individual images in a sequence
• Mechanism for referring to a collection of images as a single entity using "%X" style substitutions
• System can be extended by adding new image processing primitives.
• Have a mechanism for TCL to generate C code for image processing using common C templates.
• Implementation issues: Lazy evaluation if image primitives. Operations only done at image-write time
• Sample Video editor in TK, built in 3-days, which is customizable by the user with tcl commands

Questions:

• Have you though of making 1 line expressions more efficient?
  • They seem efficient enough
• Why are rivl commands not implemented as commands ala TK widgets
  • To permit caching and lazy evaluation of commands