Developing with VoiceXML Building a Video Conference Application
- 2. Developing with VoiceXML Building a Video Conference Application
- 3. 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
- 4. 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
- 5. 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
- 6. 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
- 7. 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
- 8. Video Conference – System Architecture Video Conference Application Video-Enabled Media Server SIP SIP SIP SIP, NETANN, VoiceXML RTP RTP RTP
- 9. 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
- 10. Basic Call Flow – SIP & VoiceXML 1. SIP INVITE validate.cgi?phone=5551212&pin=1234 Video Conference Application Refer-To: sip:conf-1@MS 11. SIP 200 OK 3. HTTP GET 4. SIP 200 OK 5. SIP 200 OK 2. SIP INVITE voicexml=http://as/askpin.vxml 6. HTTP POST 10. SIP reINVITE 7. SIP REFER 8. SIP INVITE sip:conf-1@MS 9. SIP 200 OK
- 11. 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
- 12. 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
- 13. 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
- 15. Video Conference Application – Software Components
- 16. 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)
- 17. IVR Service - API Simple API hides IVR complexity Instantiate and send an event to IvrSBB Events supported: CreateConnection Play PlayCollect Release
- 18. 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
- 19. 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
- 20. 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
- 21. 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
Editor's Notes
- #9: Discuss role of each component: Video Conference Application implements the business logic: PIN number validation, control of the conference mode Video phone, mobile phone, PC: establish call with conference application, transmit and receive audio/video to/from media server Media server: performs audio mixing, muting participants, video switching or mixing Discuss protocols: SIP for signalling RTP for media. There are two separate RTP streams per video phone: one for audio and one for video
- #20: Note that sending an SDP with “a=recvonly” to the participant device is not secure: there is no way to know if the participant device will comply.