Centralized Conferencing Media Control Models

1
Centralized ConferencingMedia Control Models

• Eric Wm. Burger
• 59th IETF
• Seoul, ROK

2
Media Manipulation Models

• Low-Level Device Control
• Manipulate Media Resource Objects
• Manipulate Plumbing Between Objects
• Application-Level Device Control
• Manipulate Conference Primitives
• Conference, Sidebar, Speaker, Preferred Speaker
• Dynamic Device Control
• Manipulate Semantic Primitives
• Mixer Advertises and Endpoint Learns Capabilities

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Low-Level Device Control Characteristics

• Client Specifies Plumbing
• Client Specifies Low-Level Media Processing
• Internal Media Topology
• Algorithm Graph
• Connections to Media Resources

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Example Conference With Three Loudest Talkers in
Mix

• Create Input Multiplexer
• Create Selector that Detects Three Loudest
  Talkers
• Create Mixer that Mixes All Streams
• Create 3 Subtraction Resources
• Create Output Multiplexer

• Connect Inputs to Selector
• Connect Inputs to Mixer
• Connect Outputs of Mixer to Subtraction Resources
• Connect Outputs of Selector to Subtraction
  Resources
• Connect Outputs of Selector to Output Multiplexer

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Examples

• Play Prompt IntoConference
• Create Audio Player
• Connect Audio Player
• Into Mixer, if Mixed In
• Disconnect Multiplexer, Connect to Endpoints if
  Played Out
• Start Audio Player

• Record Conference
• Create Audio Recorder
• Connect Audio Recorder to Output of Mixer
• Start Audio Recorder

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Implementations of Low-Level Device Control

• H.248
• Follows Steps Outlined On Previous Slides
• Create Graph as Sequence of Commands
• draft-even-sipping-media-policy-requirements-00
  and draft-mahy-xcon-media-policy-control-01
• Assert Graph in XML
• Assert Changes to Graph Using, e.g., XPATH

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Pro/Con of Low-Level

• Pro
• Absolutely No Limit to Topology
• Absolutely No Limit to Mixing Algorithm

• Con
• Anything Can Be Done in Assembly Language
• Applications Must be Constructed in Terms of DSP
  Resources, not Application Constructs
• Wrong Programmer Market
• Media Processor Cannot Optimize Resources
• Three-Loudest Talkers is Often Single DSP Image,
  not 7 Resources
• Three-Loudest With Preference is Often Single DSP
  Image, not 9 Resources
• DSP Resources is the Level of Control

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Application-Level Device Control Characteristics

• Client Specifies Conference-Level Requests
• Create a Conference
• Join Users to Conference
• Mute a Leg
• Set Preferred Speaker
• Select Mixing Algorithm
• Play Prompt
• Record Conference

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Examples

• Conference With Three Loudest Talkers In Mix
• Create Conference (INVITE)
• INVITE Attendees to Conference
• Mute Leg
• Tell Mixer to Mute Leg
• Use Preferential Mixing
• Tell Mixer that Leg is in Preferred Mix

• Play Prompt
• Tell Conference to Play Prompt
• Record Conference
• Tell Conference to Record Conference
• Perform IVR on Leg
• Tell Conference to Detach Leg
• Play/Collect
• Tell Conference to Put Back Leg

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Implementations of Application-Level Device
Control

• draft-vandyke-mscml-04
• SIP Invented for Conferencing
• SIP Appropriate for Loosely-Coupled Development
  Model
• Use Loose Coupling

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Pro/Con of Application-Level

• Pro
• Application-Level Construction
• Programmer Productivity
• LOC/day
• What it Takes to do Same Task
• Model is Conference (Application)-level, Not DSP
  Level
• Conference Is the Resource Controlled

• Con
• Algorithms and Topologies Fixed
• Not Clear if This is Bug or Feature

12
Dynamic Device Control

• Client Discovers Capabilities of Media Processor
• Media Processor Presents Set of Templates
• Templates are Application-Appropriate
• Templates are Self-Describing
• Dynamic, On-the-Fly Control Construction

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Examples

• Conference With Three Loudest Talkers In Mix
• Ask for Basic Conference Template
• INVITE Attendees to Conference
• Fill-In Template With Attendees
• Mute Leg
• Fill-In Template to Mute Leg

• Use Preferential Mixing
• Fill-In Template to Say Leg is in Preferred Mix
• Play Prompt
• Create/Connect to Player
• Fill-In Template to Direct Stream to Player
• Start Player
• Fill-In Template to Put Stream Back

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Pro/Con of Dynamic

• Pro
• Application-Level Construction
• Programmer Productivity
• LOC/day
• What it Takes to do Same Task
• Model is Conference (Application)-level, Not DSP
  Level

• Con
• Mixer, not Conference, Is the Resource Controlled
• Model Not Directly Amenable to Conference IVR
  Needs
• Is This a Problem?