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Developing with VoiceXML

Developing with VoiceXML. Building a Video Conference Application. 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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Developing with VoiceXML

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  1. Developing with VoiceXML Building a Video Conference Application

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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) @ 15 frames/second

  7. Video Conference – System Architecture RTP SIP SIP, NETANN, VoiceXML SIP Video Conference Application Video-Enabled Media Server SIP RTP RTP

  8. 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

  9. 2. SIP INVITE voicexml=http://as/askpin.vxml 7. SIP REFER 8. SIP INVITE sip:conf-1@MS 10. SIP reINVITE 6. HTTP POST 4. SIP 200 OK 5. SIP 200 OK 9. SIP 200 OK 3. HTTP GET Basic Call Flow – SIP & VoiceXML Video Conference Application 1. SIP INVITE validate.cgi?phone=5551212&pin=1234 11. SIP 200 OK Refer-To: sip:conf-1@MS

  10. 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

  11. 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 @ 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

  12. 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

  13. Mobicents - Internals

  14. Video Conference Application – Software Components

  15. 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)

  16. IVR Service - API • Simple API hides IVR complexity • Instantiate and send an event to IvrSBB • Events supported: • CreateConnection • Play • PlayCollect • Release

  17. VoiceXML – Using video extensions • Playing video clips using VoiceXML 2.0 <audio src=“http://as/welcome_h263.mov”> <audio src=“http://as/welcome_h264.mov” /> </audio> • 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

  18. 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 “a=sendonly” to the media server: v=0 o=Caller 10 20 IP4 10.1.2.3 s=Participant c=IN IP4 10.1.2.3 t=0 0 m=audio 5004 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly

  19. 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 “a=sendonly” applied to video: v=0 o=Caller 10 20 IP4 10.1.2.3 s=Participant c=IN IP4 10.1.2.3 t=0 0 m=audio 5004 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendrecv m=video 5006 RTP/AVP 98 a=rtpmap:98 H264/90000 a=sendonly

  20. 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

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