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Advances in Speech Coders: A VoIP Perspective by Roar Hagen, CTO

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25 diapositives · 426 Views · Aug 15, 2014

Join Roar Hagen, CTO at Global IP Sound, as he delves into the advancements in speech codecs relevant to VoIP technology. This session covers the history and current status of speech coding, Quality of Service (QoS) challenges, and innovative solutions like iLBC for optimally handling packet-based communication. Gain insights on how to improve user experience and sound quality over diverse network environments, and experience a live demo followed by an interactive Q&A, addressing common concerns in the realm of VoIP.

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  1. Speech Coders – a VoIP perspective Roar HagenCTO SIP/email: roar.hagen@globalipsound.com

  2. Agenda • Speech Coders – a VoIP perspective • Demo • Q&A

  3. QoS – (endpoints) status”A lot of talk, ... but not much work” • Year after year the same story • More then 3000 papers since 1984 • Limited ToS support at the end points

  4. percentage of respondents 0 10 20 30 40 50 60 source: Forrester Research/AT&T (2000) QoS – statusIndustry’s perspective quality concerns unproven technology PSTN works fine too busy to switch not compelling economics

  5. PSTN Managed network Wireless Managed network Public Internet [ ] Next generation codecs should address the needs of all applications Background - Diverse Environment

  6. Packet Loss San Francisco – Hong Kong

  7. Jitter San Francisco – Hong Kong

  8. Homg Kong to China VoIP Call

  9. Wireless VoIP – The Big Unknown ? Mobility Vehicle 2G/2.5G 3G WLAN Walk Fixed LAN Bluetooth 0.1 10 1 Mbps 100

  10. Approach We need holistic view/approach for both • Horizontal (end-to-end) perspective • Vertical (top-down) perspective

  11. Vertical (Top Down) Perspective Presentation Speech Codecs/… Session SIP/H.323 Transport RTP/UDP/RSVP Network IP/WFQ/IP-prec Link MLPPP/FR/ATM AAL1 Physical

  12. VoIP Aspirations • IP innovation rather than PSTN replication • New features and services through voice and data convergence • End-to-end IP • Better than PSTN sound quality

  13. Current speech processing technology not designed for packet switched environments “FALL OFF A CLIFF” shape of curve forces over provisioning MOS = USER EXPERIENCE OVERPROVISIONED NETWORK CONGESTED NETWORK * MEAN OPINION SCORE

  14. …congestion related VoIP QoS problems can be solved without over provisioning… MOS = USER EXPERIENCE OperateAT and ABOVE congestion point without customer knowing OVERPROVISIONED NETWORK CONGESTED NETWORK * MEAN OPINION SCORE

  15. GIPS Ehanced G.711+ GIPS NetEQ™ G.711+GIPS NetEQ™ G.711+ITU PLC G.729A G.711+No PLC 0% 5% 10% 15% 20% 25% 30% narrow band sound quality equal to PSTN wide band sound quality Better Than PSTN Quality Matching PSTN Quality Telephony bandwidth speech test result Wideband speech 5 5 4.5 4.5 4.0 4.0 3.5 3.5 MOS MOS 3.0 3.0 2.5 2.5 GIPS iPCM™-wb+ 2.0 2.0 GIPS NetEQ™-wb G.722+ GIPS NetEQ™-wb 1.5 1.5 G.722.1 Source + no PLC 1.0 1.0 0% 5% 10% 15% 20% 25% NETWORK CONDITION (% PACKET LOSS) NETWORK CONDITION (% PACKET LOSS) SOURCE LOCKHEED MARTIN GLOBAL TELECOMMUNICATION (COMSAT)

  16. Jitter Buffer/PLC Enhancements Source: Lockheed Martin Global Telecommunications (COMSAT)

  17. 140 Jitter Adaptive jitter buffer Fixed jitter buffer NetEQ™ 120 100 80 Delay (ms) 60 40 20 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Packet number Delay gain with NetEQ™approx. 30-60ms compared to traditional jitter buffers

  18. The NextGen Speech Codec Ideal • Need one concept that will work for a long time • footprint importance • Need to handle large diversity of transport network • low rate • high quality, high rate • packet loss • jitter • low delay • Manageable IPR situation • Signal Robustness • speech • music • Suitable for variety of applications, e.g. IP video-conferencing

  19. iLBC (internet Low Bitrate Codec) • Speech sampled at 8 kHZ, • using a block-independent linear-predictive coding (LPC) algorithm. • Bandwidth 13.867 kbps (52 bytes per 30 ms) • Frame size 30 ms (support for 20 ms in the next revision) • Complexity and memory requirements are similar to ITU G.729A • Basic Quality is equal to or better than G.729. Packet loss robustness is significantly better than G.729. • Packet loss concealment - Integrated example solution

  20. MOS Results Source: Dynastat Inc.

  21. iLBC - IETF work • IETF deliverables, submitted during February ‘02: • iLBC codec specification draft - experimental standards track • iLBC RTP Payload Profile - regular standards track (AVT) • Statement about IPRs in iLBC and its “freeware nature” • MOS results submission to the AVT mailing list during March ‘02

  22. Why iLBC !? • Current low bit rate codecs: ITU G.729, G.723.1, GSM-EFR, and 3GPP-AMR were developed for circuit switched & wireless telephony and are all based on the CELP (Code Excited Linear Prediction) paradigm. • CELP coders are stateful, they have memory, error propagation results from lost or delayed packets. • iLBC treats every packet individually, making it suitable for packet communications.

  23. More information • Coming Soon - web site www.ilbcfreeware.org with: • Info about initiative • Info about codec • Latest iLBC IETF drafts (spec and payload format) • Latest iLBC float point Source code • FAQ list • IETF drafts: • draft-andersen-ilbc-00.txt - codec spec (exper. stds track) • draft-duric-rtp-ilbc-00.txt - RTP payload profile (AVT group) • Web site www.globalipsound.com • Free demo SIP client available, please request at: SIP/email: alan.duric@globalipsound.com

  24. Summary • Current speech coding technology not suited for VoIP • VoIP opens possibilities • Move quality exprience to the next level with wideband coders • NGN will not be NGN unless we move step forward on all of its fields • iLBC – internet Low Bit Rate Codec • Provide an open standard ”the Internet way” for coder

  25. Demo