Speech Coders a Vo IP perspective Roar

Speech Coders – a Vo. IP perspective Roar Hagen CTO SIP/email: roar. hagen@globalipsound. com

Agenda • Speech Coders – a Vo. IP perspective • Demo • Q&A

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

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

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

Packet Loss San Francisco – Hong Kong

Jitter San Francisco – Hong Kong

Homg Kong to China Vo. IP Call

2 G/2. 5 G Wireless Vo. IP – The Big Unknown ? 3 G Fixed Walk Vehicle Mobility WLAN Bluetooth 0. 1 1 10 100 Mbps

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

Vertical (Top Down) Perspective Presentation Speech Codecs/… Session SIP/H. 323 Transport RTP/UDP/RSVP Network IP/WFQ/IP-prec Link MLPPP/FR/ATM AAL 1 Physical

Vo. IP 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

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

MOS = USER EXPERIENCE …congestion related Vo. IP Qo. S problems can be solved without over provisioning… Operate AT and ABOVE congestion point without customer knowing OVERPROVISIONED NETWORK CONGESTED NETWORK * MEAN OPINION SCORE

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 3. 5 MOS 4. 0 3. 0 2. 5 GIPS Ehanced G. 711+ GIPS Net. EQ™ 2. 0 G. 711+GIPS Net. EQ™ G. 711+ITU PLC 1. 5 3. 0 2. 5 GIPS i. PCM™-wb+ GIPS Net. EQ™-wb 2. 0 G. 722+ GIPS Net. EQ™-wb G. 722. 1 1. 5 G. 729 A 1. 0 0% G. 711+No PLC 5% 10% 15% 20% 25% 30% NETWORK CONDITION (% PACKET LOSS) 1. 0 0% Source + no PLC 5% 10% 15% 20% 25% NETWORK CONDITION (% PACKET LOSS) SOURCE LOCKHEED MARTIN GLOBAL TELECOMMUNICATION (COMSAT)

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

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

The Next. Gen 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

i. LBC (internet Low Bitrate Codec) • Speech sampled at 8 k. HZ, • 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. 729 A • 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

MOS Results Source: Dynastat Inc.

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

Why i. LBC !? • Current low bit rate codecs: ITU G. 729, G. 723. 1, GSM-EFR, and 3 GPP-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. • i. LBC treats every packet individually, making it suitable for packet communications.

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

Summary • Current speech coding technology not suited for Vo. IP • Vo. IP 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 • i. LBC – internet Low Bit Rate Codec – Provide an open standard ”the Internet way” for coder

Demo