Wideband Codecs for Enhanced Voice Quality

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(No Transcript)
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Wideband Codecs for Enhanced Voice Quality

• Ensuring optimum wideband speech quality in
  converged VoIP/mobile applications/services

Claude Gravel VP Engineering VoiceAge Corporation
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Contents

• Introduction

• Why Wideband Speech?

• Deployment Challenges

• AMR-WB Alleviates These Challenges

• Market Momentum / Conclusions / Demo

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VoiceAge Corporation who are we?
Business Low bit rate audio compression technologies research, IPR licensing and optimized implementations development
Headquarters Montreal, Canada
Technologies AMR 3GPP, CableLabs narrowband voice codec AMR-WB 3GPP, ITU-T, CableLabs wideband voice codec VMR-WB 3GPP2, CableLabs wideband voice codec AMR-WB 3GPP, DVB-H audio codec
Achievements Won every international audio compression standard for which VoiceAge competed in the last 10 years at 3GPP, 3GPP2, ITU, ETSI, TIA, CableLabs
Implementations World Class optimized implementations and proprietary solutions on multiple O/S and processors/platforms (including TI- ARM-based systems)
Deployment More than 2B mobile phones and over 500M PCs currently use VoiceAges technologies
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International Standards Using ACELP
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Contents

• Introduction

• Why Wideband Speech?

• Deployment Challenges

• AMR-WB Alleviates These Challenges

• Market Momentum / Conclusions / Demo

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Speech Synthesis Model
Used in CELP/ACELP Speech Coding
air from lungs
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2
vocal chords (periodicity)
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vocal tract articulators (including jaw, lips,
tongue, velum)
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1
2
3
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Speech Signal

• Basically, same synthesis model for everyone
• So, speech has a universal structure or
  signature

1.25 sec
v o i ce a
ge
180 ms
45 ms

• Voiced fricative
• quasi periodic noise
• lower energy

70 ms
45 ms
45 ms

• Transient
• variable energy
• fast spectral evolution

• Purely Voiced
• quasi periodic
• high energy
• more low frequency energy
• strongly correlated

• Unvoiced
• non periodic
• low energy
• uncorrelated
• more high frequency energy

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What is Wideband Communication?

• Substantially increases captured speech
  information
• Delivers double the audio signal bandwidth
• Enables digital end-to-end packet-based services
  to deliver much better speech communication
  quality than traditional PSTN circuit-switched
  telephony
• VoIP quality differentiator

An Emerging Opportunity to Deliver Vastly
Improved Speech Quality
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Signal Bandwidth
Wideband Speech Below 200 Hz increased
naturalness, presence, and comfort. Above 3400
Hz increased intelligibility and fricative
differentiation
Voiced segment
Unvoiced segment
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Typical Speech Signal Acoustics
Improved voice quality intelligibility (e.g.,
s f differentiation)
Improved speech naturalness, presence and comfort
Everyone looked extremely confused about the
news
Wideband telephony covers much more speech signal
information
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Why Wideband Speech Now?

• Improved intelligibility, naturalness and
  presence
• Reduces listener fatigue
• Improved hands-free/speakerphone sound quality
• Improves speaker and speech recognition
• High-quality low-bit-rate wideband codecs
• G.722.2/AMR-WB at 724 kbps
• No need to increase network capacity to deliver
  better quality sound
• Wideband capable devices are available now
• Wideband audio microphones and device acoustics
  more affordable
• Rising user awareness of enhanced sound quality
• Wideband teleconferencing
• Wideband enterprise/ASP IP telephony
• Wireless/VoIP multimedia services

Speech Coding Technology, Network/Device
Capabilities and Market Demand are Converging
Towards Pervasive Wideband Communications
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Contents

• Introduction

• Why Wideband Speech?

• Deployment Challenges

• AMR-WB Alleviates These Challenges

• Market Momentum / Conclusions / Demo

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Voice Processing -- Key for Speech Quality
Control Management
Voice Processing (Digital Communications Domain)
Call Processing
Voice MIBs System MIBs
Speech Codec VAD CNG DTX PLC Variable-Multi Rate
Switching
PCM I/F
Echo Canceller
Echo Canceller
Packet De-Packet RTP
SNMP
Signaling Protocol
Noise Suppressor
Jitter Buffer
Analog Domain
Codec choice impacts network cost and
interoperability A major contributor to the
listener quality experience
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Speech Coding Attributes

• Bit rate
• As low as possible
• Delay
• As little as possible
• Quality
• As high as possible
• Complexity
• As algorithmically simple as possible to
  constrain platform processing and memory
  requirements and reduce battery consumption in
  mobile devices
• Robustness
• Effective operation under background noise and
  channel impairment conditions
• Standards compliance
• Open, tested and interoperable solutions

As required by specific applications
Difficult to attain all of these often divergent
objectives at the same time
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VoIP Speech Quality Challenges

• Missing packets
• Packet delay
• Transcoding
• Background noise

• Due to network congestion or transmission errors
• Wireless networks are more prone to losing
  packets

• Due to network congestion or transmission errors
• Real-time communication cant wait too long for
  packets or retransmission

• Needed when end-devices and network equipment
  support incompatible speech/audio coding
  technologies traversing diverse networks such
  as across fixed/mobile environments
• Increases system costs, adds delays and
  introduces audio quality impairments

• Reduces intelligibility and comfort level of
  conversations
• Ambient office/workplace/household noise
• Street/car noise in mobile applications

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Speech Processing Techniques for Improving VoIP
Voice Quality

• Missing packet impairments can be mitigated
  through
• Sending additional data to help preserve
  information
• FEC/Repetition of frames
• Works well for sporadic packet losses but not so
  well for bursts of lost packets
• Increases transmitted bit rate to send redundant
  information

frames
packets
time
A simple forward error correction scheme based on
repeating the previous frame in each packet
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Speech Processing Techniques for Improving VoIP
Voice Quality

• Missing packet impairments can be mitigated
  through (contd)
• Packet loss concealment (PLC)
• Techniques used by the decoder to estimate
  parameter values for missing frames based on the
  characteristics of preceding frames
• Can be improved by classifying frames and
  repeating or adjusting parameters based on
  heuristics driven by the classes of the frames
  preceding the missing frame(s)
• Extrapolate missing frame parameters as a
  function of the expected frame class (e.g.,
  voiced/unvoiced, stops, nasals, )
• E.g., for voiced frames, repeat the pitch
  parameters
• Objective limit abrupt changes in energy that
  can cause annoying clicks
• Late packet arrival processing can also be
  leveraged to benefit from some of the information
  in a packet that arrives too late
• Can benefit PLC methods as applied to subsequent
  delayed or lost packets

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Speech Processing Techniques for Improving VoIP
Voice Quality

• Missing packet impairments can be mitigated
  through(contd)
• Frame Interleaving
• Each packet contains non-contiguous frames to
  lower the overall impact on the reconstructed
  speech signal of a lost packet
• Introduces delays which may make it unsuitable
  for real-time speech communication
• Works well for audio streaming

frames
packet 1
packet 2
packet 3
time
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Speech Processing Techniques for Improving VoIP
Voice Quality

• Network congestion, which can lead to delayed or
  dropped packets, can be alleviated by lowering
  the average communication bit rate
• VAD/DTX/CNG
• Using Voice Activity Detection (VAD),
  Discontinuous Transmission (DTX) and Comfort
  Noise Generation (CNG) capabilities to limit
  consumed bandwidth during periods of silence
  during a conversation
• Adaptive codecs
• Source controlled
• Optimal selection of the bit rate and coding
  scheme based on active speech
• Network controlled
• Adapt the bit rate to make best use of varying
  available bandwidth

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Transcoder-Free Network Design for Fixed/Mobile
Convergence
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Improving VoIP Speech Quality

• Mitigating the main issues impacting VoIP speech
  quality
• Missing packets
• Delayed packets
• Transcoding
• Background noise

• Proper network engineering with integrated QoS
  mechanisms (in closed systems)
• Choosing the best speech coding/processing
  technology (adaptive, enhanced voice quality,
  robust and extensible)
• Improved packet loss concealment
• Late packet arrival processing
• Time scale modification
• Adaptive jitter buffering

• Transcoder-free network design to avoid increased
  system costs, delays and audio quality
  impairments
• Leverage seamlessly interoperable
  standards-proven codecs

• Choose codecs that can readily accommodate
  background noise suppression algorithms
• Proven noise suppression in standards selection
  characterization testing results

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Contents

• Introduction

• Why Wideband Speech?

• Deployment Challenges

• AMR-WB Alleviates These Challenges

• Market Momentum / Conclusions / Demo

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Why AMR-WB/G.722.2

• AMR-WB/G.722.2 is the right wideband codec for
  network convergence
• Very robust
• Supports dynamic adaptation to mobile network
  conditions
• Includes built-in efficient packet loss
  concealment
• Performs well even with high bit error rates
• Multi-rate codec delivers very good quality even
  at bit rates comparable to those of narrowband
  (12 kbps)
• No need for potentially costly and time-consuming
  network capacity upgrades
• Supports VAD/DTX/CNG for enhanced efficiency
• Low-complexity encoder and decoder
• Standardized in 3GPP, ITU-T CableLabs
  PacketCable 2.0
• Can interoperate transcoder free across mobile/IP
  networks
• Eliminates latency, impairments, costs

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Subjective NB-WB Quality Comparison
NB-WB Voice Quality as a Function of Bit Rate
Ericsson Review, No. 3, 2006
AMR-WB/G.722.2 Greatly Improves Perceived Voice
Quality
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AMR-WB Subjective Testing Results
5.0
Clean Condition Test (English Language) AMR-WB/G.7
22.2 Characterization Test
4.5
G.722 _at_ 64 kbps

4.0
G.722 _at_ 48 kbps
3.5
MOS
3.0
G.722.2 _at_ 8.85 kbps
G.722.2 _at_ 12.65 kbps
2.5
G.722.2 _at_ 18.25 kbps
2.0
G.722.2 _at_ 23.05 kbps
1.5
1.0
No Tandem -26 dBov
Self-Tandem -26 dBov

• AMR-WB/G.722.2 Delivers Excellent Wideband Speech
  Quality
• Even at Low Bit Rates (e.g., MOS at 8.85 kbps
  exceeds G.722 at 48 kbps)

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AMR-WB CPU efficiency

• AMR-WB/G.722.2 performance on widely deployed
  communications device processors show the codecs
  relatively low complexity

ModeBit rate (kbps) 06.6 18.85 212.65 314.25 415.85 518.25 619.85 723.05 823.85
ARM 9E (MHz) Encoder Decoder 3911 349 398 418 418 428 438 438 439
TI C55x (MIPS) Encoder Decoder 19.674.88 21.244.35 24.644.20 27.02 4.30 27.234.39 28.204.55 29.334.61 29.134.83 26.645.21
TI C64x (MIPS) Encoder Decoder 22.155.94 23.755.00 26.984.81 29.364.85 29.584.88 30.684.95 32.104.98 31.765.05 29.975.40
Supported by most commonly used communications
processors
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The Standard Solution Advantage

• Open, collaborative and competitive process
• Requirements specifically address target
  applications
• Published algorithms and source code
• Permits wider and more effective scrutiny
• Clearer intellectual property ownership
• Rigorous comparative testing under diverse
  conditions
• Background noise types and levels
• Spoken languages
• Speaker types
• Various network impairments

Interoperable, Open and Fully TestedEnsures that
the best technologies are chosen
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Interoperability between Fixed/Mobile Network
Services

• Transcoder-free Interoperability in Fixed/Mobile
  Convergence
• 3GPP Wi-Fi/WiMAX ITU-T interoperability
• AMR-WB / G.722.2 end-to-end across networks
• No need for transcoding at media gateways
• Improves on service quality end to end
• Reduces network delays and equipment complexity
• Lowers network costs (equipment costs and
  licensing)

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Contents

• Introduction

• Why Wideband Speech?

• Deployment Challenges

• AMR-WB Alleviates These Challenges

• Market Momentum / Conclusions / Demo

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Growing Market Momentum

• VoiceAge
• Others

• Ixia
• Tektronix
• GL Comms
• NetHawk
• Many others

• VeriSilicon
• Texas Inst.
• Freescale
• Renesas
• ST Micro

• Nokia
• Sony-Ericsson
• Motorola
• Samsung
• Panasonic
• NEC
• CounterPath
• Polycom
• Mobiles, Softphones, VoIP terminals, Conferencing
  terminals

• Nokia
• Ericsson
• AudioCodes
• Gateways, ATA/MTA, Softswitches,

• T-Mobile Trial
• Wireless Operators
• Cablecos
• VoIP ASPs

Accelerating Adoption of AMR-WB/G.722.2 leads to
Happy Consumers and a Wealthy Telecom Service
Value Chain
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Successful Ericsson/T-Mobile Trial
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Extremely Good
Good
Quite Good
Nice to Have
Ericsson Review, No. 3, 2006
Quite Bad

• 150 consumers participated for 4 weeks in
  Germany, April/May 2006 confirmed
  earlier lab MUSHRA tests
• More than 90 perceived better voice quality
  clarity
• Felt a greater sense of privacy, discretion
  comfort due to improved voice quality
  intelligibility
• Could more easily place complete calls in
  environments with high background noise
• Business users highly valued voice quality for
  improving communication, reducing expenses
  giving a positive impression
• Ericsson anticipates positive outcomes for
  operators
• More mobile traffic, i.e., more calls for longer
  durations
• Can offer enhanced services for conferencing,
  personalized ringback signals, automatic voice
  recognition, voice mail
• Can cut costs, e.g., by reducing cost of
  acquiring new subscribers, reducing helpdesk costs

Bad
Extremely Bad
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Wideband Speech Communications

• An Evolutionary Migration
• Wideband speech coding is consistent with
  narrowband codecs
• Bit rates comparable to narrowband codecs
• Similar robustness techniques to handle packet
  losses and delays can be used
• Low-complexity implementations available for all
  popular communications processor types
• While vastly improving perceived voice quality
• Strategically deploying wideband capability in
  terminal and network equipment enables evolution
  to wideband speech communications
• Compatible with existing network infrastructure
• No forklift replacements needed a graceful
  evolutionary migration, not a disruptive
  revolution

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Conclusions

• Speech communications are rapidly moving to
  end-to-end digital packets over all networks
  wired and wireless towards fixed/mobile
  convergence
• Provides an opportunity to vastly improve
  communications quality through widescale
  deployment of wideband speech
• Efficient codecs, devices with wideband acoustics
  and processing are already available
• Many benefits but also some challenges to
  consistently delivering high-quality voice end to
  end in real-world deployments
• Enhanced speech coding and processing techniques
  have been developed to help overcome these
  challenges
• The selection of standards-based advanced
  wideband speech coding technologies such as
  AMR-WB/G.722.2 is one of the fundamental steps
  towards improving voice quality between diverse
  devices and converging networks
• Adoption of AMR-WB/G.722.2 in the telecom service
  delivery value chain is growing wideband speech
  quality has been shown to be highly preferred by
  consumers

Are your devices, systems, solutions, services
ready?
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Hear the rich sound of wideband

• Wideband Demo

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Wideband Codecs for Enhanced Voice Quality

• Thank you!
• claude.gravel_at_voiceage.com
• www.voiceage.com
• Come and talk to VoiceAge at Booth 107