Developing with VoiceXML

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(No Transcript)
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Developing with VoiceXML

• Building a Video Conference Application

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Agenda

• VoiceXML
• Video using VoiceXML
• Components of a Video Conference Server
• System Architecture
• SIP RTP flows
• JSLEE Mobicents
• Software Architecture
• Controlling Participants
• Putting it all together

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VoiceXML What is it?

• VoiceXML is an IVR scripting language
• Used to develop complex IVR applications, such as
• Phone-based self-help services (i.e., labyrinths
  ?)
• Multi-level auto-attendants
• Calling card services
• Standardized by W3C
• http//www.w3.org/Voice/
• Also used as a control protocol between VoIP
  application servers and media servers
• Supported by most media server vendors

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Developing an Application with VoiceXML

• This presentation shows how to develop a video
  conferencing application using VoiceXML and
  off-the-shelf components
• We will use the Voxpilot/HP video extensions to
  VoiceXML
• Provides playing and recording video prompt
• Supports multiple video codecs
• Proposed by Burke (Voxpilot) McGlashan (HP)
• Extensions may get integrated into VoiceXML 3.0
• We will cover the system architecture,
  components, protocols, and support for multiple
  audio and video codecs

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Video Conferencing Application

• Components for building a video conferencing
  solution are now much cheaper
• Good web cam
• Good headset
• Video softclient
• Open source telecom framework
• Video-enabled media server
• Small Medium Enterprises can now use it
• Can even be deployed in home offices

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Video Conference Application - Goals

• Low Cost
• Must use standard components protocols
• Easy to Use Minimal Learning Curve
• Same interface as existing meet-me conference
  bridges
• Advanced interface accessible through web
• Provide Common Conferencing Features
• PIN number validation
• Mute one or more participants
• Prime Speaker
• Manual or Automated Video Source Control
• Good Video Quality
• At least CIF (352x288) _at_ 15 frames/second

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Video Conference System Architecture
RTP
SIP
SIP, NETANN, VoiceXML
SIP
Video Conference Application
Video-Enabled Media Server
SIP
RTP
RTP
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Major Component Responsibilities

• Video Conferencing Application
• Back-to-back SIP user agent (B2BUA)
• Controls conference participants when conference
  is up
• e.g., muting a participant, giving priority to a
  participant
• Delegates to VoiceXML script the task of PIN
  validation
• VoiceXML script
• Validates PIN (uses CGI script to access a
  database)
• Transfers the call to conference bridge
• Media Server
• Executes VoiceXML script
• Performs audio mixing
• Performs video processing

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Basic Call Flow SIP VoiceXML
Video Conference Application
1. SIP INVITE
validate.cgi?phone[phone]pin1234
11. SIP 200 OK
Refer-To sipconf-1_at_MS
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Video Conference Application Software

• Video application is built on top of JSLEE, a
  Java real-time framework
• Database contains a list of active conferences,
  phone numbers, and PINs
• Apache provides
• Web pages
• Access to VoiceXML scripts
• Access to media files
• Execution of CGI scripts

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Video-enabled Media Server

• Video-enabled Media Servers are available from
  many vendors
• Select a media server that supports Video IVR and
  Video Conferencing
• Video Codec H.263 and H.264 _at_ CIF resolution
  (352x288)
• Video Conferencing mode should have at least
• Manual Control
• Automated control (e.g., follow-me)
• Audio mixing should provide
• Audio Codec G.711 ulaw/A-Law, G.729, AMR
• Audio mixing without introducing echo
• Noise reduction
• Packet Loss Concealment algorithm

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Mobicents a Telecom Framework

• Mobicents is an open source JSLEE container
• JSLEE is a Java-based framework for real-time
  apps
• JSLEE is to telecom what J2EE is to business apps
• Mobicents is written by some JBoss developers
• Mobicents provides
• Soft real-time event routing
• SIP stack
• Traces, logs, alarms
• See http//www.mobicents.org

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Mobicents - Internals

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Video Conference Application Software
Components

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IVR Service

• IVR service provides a high-level API to playback
  and digit collection functions
• Hides details of SIP and media server protocols
• Isolates applications from Media Server protocol
• e.g., if MS protocol changes from VoiceXML to
  MSCML, only IVR service must change
• IVR service implemented as a JSLEE Service
  Building Block (SBB)

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IVR Service - API

• Simple API hides IVR complexity
• Instantiate and send an event to IvrSBB
• Events supported
• CreateConnection
• Play
• PlayCollect
• Release

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VoiceXML Using video extensions

• Playing video clips using VoiceXML 2.0
• ltaudio srchttp//as/welcome_h263.movgt
• ltaudio srchttp//as/welcome_h264.mov /gt
• lt/audiogt
• Two video clips are provided one for H.263 video
  clients, the other for H.264 video clients
• The example is using the VoiceXML fallback audio
  feature for supporting both codecs
• The VoiceXML interpreter will try to play each
  video clip in the list until it finds one that is
  compatible with the video codec of the remote
  device

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Muting a participant using RFC3264

• The conference leader can mute a participant
• This is achieved by the Video Conf App sending a
  SIP reINVITE with SDP containing asendonly to
  the media server
• v0
• oCaller 10 20 IP4 10.1.2.3
• sParticipant
• cIN IP4 10.1.2.3
• t0 0
• maudio 5004 RTP/AVP 0
• artpmap0 PCMU/8000
• asendonly

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Manual Control of the Video Feed

• The conference leader can manually control the
  video feed displayed to all participants
• This is achieved by turning-off the video source
  of all participants except one
• Send a reINVITE with SDP containing asendonly
  applied to video
• v0
• oCaller 10 20 IP4 10.1.2.3
• sParticipant
• cIN IP4 10.1.2.3
• t0 0
• maudio 5004 RTP/AVP 0
• artpmap0 PCMU/8000
• asendrecv
• mvideo 5006 RTP/AVP 98
• artpmap98 H264/90000
• asendonly

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Putting it all Together

• VoiceXML provides the user interface to the video
  conference
• Mobicents provides an easy to use real-time
  framework for telecom applications
• Mobicents hides SIP complexity
• Building the business logic for a video
  conferencing application is no longer difficult
• Low-cost video phones and softclients make this
  solution possible
• Entire solution can be deployed in small and
  medium businesses