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Speech Coders – a VoIP perspective Roar Hagen CTO SIP/

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Presentation on theme: "Speech Coders – a VoIP perspective Roar Hagen CTO SIP/"— Presentation transcript:

1 Speech Coders – a VoIP perspective Roar Hagen CTO SIP/

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 QoS – status Industry’s perspective quality concerns unproven technology PSTN works fine too busy to switch not compelling economics percentage of respondents source: Forrester Research/AT&T (2000)

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

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 ? LAN 2G/2.5G WLAN Bluetooth 3G Vehicle Walk Fixed Mbps Mobility

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

11 Vertical (Top Down) Perspective Physical LinkMLPPP/FR/ATM AAL1 NetworkIP/WFQ/IP-prec TransportRTP/UDP/RSVP SessionSIP/H.323 PresentationSpeech Codecs/…

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 * M EAN O PINION S CORE C ONGESTED N ETWORK O VERPROVISIONED N ETWORK MOS = U SER E XPERIENCE “ F ALL O FF A C LIFF” shape of curve forces over provisioning “ F ALL O FF A C LIFF” shape of curve forces over provisioning

14 …congestion related VoIP QoS problems can be solved without over provisioning… * M EAN O PINION S CORE C ONGESTED N ETWORK O VERPROVISIONED N ETWORK MOS = U SER E XPERIENCE Operate A T and A BOVE congestion point without customer knowing

15 GIPS Ehanced G.711+ GIPS NetEQ™ G.711+GIPS NetEQ™ G.711+ITU PLC G.729A G.711+No PLC Matching PSTN Quality Telephony bandwidth speech test result S OURCE L OCKHEED M ARTIN GLOBAL T ELECOMMUNICATION (COMSAT) N ETWORK C ONDITION (% P ACKET L OSS) 0%5%30%10%15%25%20% MOS GIPS iPCM™-wb+ GIPS NetEQ™-wb G.722+ GIPS NetEQ™-wb G Source +no PLC Better Than PSTN Quality Wideband speech 0% 5% 10% 15% 20% 25% MOS N ETWORK C ONDITION (% P ACKET L OSS) narrow band sound quality equal to PSTN wide band sound quality

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

17 Delay gain with NetEQ™ approx ms compared to traditional jitter buffers Adaptive jitter bufferJitterFixed jitter bufferNetEQ™ Packet number Delay (ms)

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 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 –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 Free demo SIP client available, please request at: SIP/

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

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