i phone presentation jan linden gips
TRANSCRIPT
VoIP on the iPhone –Imagine the Possibilities!Imagine the Possibilities!
Jan Linden, VP of Engineering
iPhone Developer Summit
20 October 2008
Evolution of IP Voice and Video ProcessingProcessing
Advanced Mobile and Multimedia Capabilities
Solutions Designed Specifically for VoIP
PSTN Solutions Adapted for VoIP
Mobile Market Trends
• Fixed Mobile Convergence– Mobile phone increasingly perceived as a computer
d d i h l ki hi• Advanced operating systems such as Apple OSX are making this a reality
– Users expect to access the same applications available across multiple platformsplatforms
• Increased accessibility and affordabilityk d d l– Network operators are introducing new pricing models to
encourage uptake of data driven services and applications• IP networks enable more cost effective transport
– Handset prices declining• iPhone 3G half the price of 1st Generation
Mobile Technology Trends
• Migration from legacy cellular to next‐gen networks– Allows for faster data connection
• Growth of Smartphone adoption– iPhone and other dual‐mode phones provide greater flexibility in
l bl kconnecting to available networks– All‐in‐one devices able to run multiple applications efficiently
• Consumers can place calls and receive data simultaneously
• Development of 3rd Party Applications– Operating systems, like the Apple OS X, more conducive to advanced
3rd party applications – VoIP over mobile in high demand
The iPhone as a VoIP Platform
• iPhone most VoIP friendly phone on market…– Open APIs for easy development– Sufficient CPU resources– Support of wideband codecs– Intuitive UI makes for simple navigation between applicationsp g pp– Demand for 3rd party apps is higher than other phones
• …but strengths present unique challenges– Running too many applications can drain resources– Usage scenarios can negatively impact voice quality
With the right voice processing software, developing VoIP applications is a cinch!
Technology Challenges – Network Connections
• IP NetworksL t– Latency
– Jitter – Packet loss
• Wireless connections– Low signal strength– Interference from users in
hbsame or neighboring frequencies
– Available bandwidth varies– Wi‐Fi access pointWi Fi access point
bottlenecks
Technology Challenges
• Device Limitations– Limited processing powerp g p– Battery life– Data intensive applications can
cause jitter
• Mobile Environments– Tend to have excessive
background noisebackground noise– Hands Free operation enhances
acoustic echo
Impact of IP Networks
Delay
Packet Loss
Network Jitter
Impact of IP Networks – Latency
• Major effect is “stepping on each other’s talk”
• Usage scenario affects annoyance factor – higher delay can be tolerated for mobile devices
• Long delays make echo more annoying
Sources of Latency
• Codec• Capture• Playout
A/DPre‐processing
Speech encoding
IP interfaceA/D
Pre‐Processing
Speech Encoding
IP InterfacePlayout
• Network delay• Jitter buffer
i i
g
Post‐Speech Jitter
IP Network
Post Speech Jitter
IP Network
• OS interaction• Transcoding
D/A processing
Speech decoding
Jitter bufferD/A
Post‐Processing
Speech Decoding
JitterButter
Impact of Latency on Voice Quality
4
ore
2
3
Mea
n O
pini
on S
co
10 250 500 750
One-w ay transmission time [ms]
Data from ITU‐T G.114
• ITU‐T (G.114) recommends:– Less than 150 ms one‐way delay for most applications (up to 400 ms
t bl i i l )acceptable in special cases)
• Users have got used to longer delays– Still, low delay very important for high quality
Impact of IP Networks – Packet Loss and JitterJitter
• Packet Loss– Occurs due to flushed buffers in network nodes– Same effect if packets are too late to be used– Smooth concealment necessary
• Network Jitter– Transmission time differs for each packetTransmission time differs for each packet– Jitter buffer necessary to ensure continuous playout– Trade‐off between delay and quality
Technology Challenges – Mobile Environments
• Acoustic Echo– Speakerphone operation common for iPhones– Microphone and speaker close– High delay in VoIP makes echo more prominent
• Background Noise– Environments inherently noisy– Usage scenarios can make
differentiating between speech and noise difficultnoise difficult
Technology Challenges – Devices
• Limited Resources– Size limits processing power– Battery life also limited
• VoIP Friendliness– Many smartphones limit access to
soundcard– Device buffers add latencyy– Clock drift
• Too much of a Good Thing– Running too many applications can drain– Running too many applications can drain
resources– Multiple applications accessing network
can result in jitter j
VoIP Design Considerations
Speech QualityQuality
CostTime to Market
Flexibility
Ease of Use
Cost
Signaling
InfrastructureyNetwork ImpairmentsPower C ti
Device Considerations
Features
Consumption
Mobile VoIP Design Considerations
Hardware Issues
Coping with Network
Hardware Issues (Processor, OS, Acoustics, etc.)
Speech Codec
Network
Codec
Hardware
VoIP DesignChallenges
Coping with Network Degredation Power Consumption
Echo Cancellation Echo PowerEcho Cancellation
Additional Voice Processing Components
Environment – Background Noise, Room Acoustics,
etc.
Echo
Voice Environmentg p Environment
Speech Codec
Packet‐loss RobustnessComplexityComplexity
• Many conflicting parametersaffect choice of codec
MemoryDelay
affect choice of codec
• Determines upper limit of quality
Speech Codec
Input Signal
q y
• Support of several codecs necessary
Sampling R
Bit‐rate
Quality
Bit‐rate Input Signal Robutness– Interoperability
– Usage scenarioRateQuality
• IPR issues a significant concern
Audio Bandwidth Effect on Quality
Quality
Std Wideband Speech
CD ‐Audio
GIPS Wideband Speech
GIPS Narrowband Speech
p(e.g. G.722.2)
Std Narrowband Speech Implementation (PSTN)
200 ‐ 3400 Hz
• Better than PSTN quality is achievable in VoIP
Frequency
4 kHz 6.4‐7.0 kHz3,4 22.1 kHz8 kHz
– Utilizing full 0 – 4 kHz band in narrowband– Wideband coding offers more natural and crispier voice
Recommendations
• IP NetworksN d f d di t d b d idth if l ti i l d hi h– No need for dedicated bandwidth if solution includes high performance:• Bandwidth management• Robust codec framework
– Low latency achieved by efficient jitter buffer
• AudioHi h lit di i i l– High quality audio is crucial • Users expect the same quality they experience on the PC
• Optimized Solutionsp– Efficiency for ARM processors on iPhones– Reduce CPU constraint and increase battery life
Recommendations
• Adaptive Jitter Buffer and PLC– Manage up to 30% packet loss– Manage up to 30% packet loss– Adapt to network busts and excessive mobile jitter
• Codecs Designed for IP Networksg– Work in tandem with jitter buffer to overcome packet loss– Can deliver Wideband experience– Robust and bit‐rate adaptive codecs necessary
• Efficient use of the total available bandwidth• Efficient use of the total available bandwidth• GIPS iLBC already in the iPhone, GIPS iSAC and other wideband codecs provide even better user experience
• Aggressive Voice Quality Enhancement– Detect and cancel background noise– Suppress acoustic echo
Recommendations
• VoiceEngine Mobile for iPhone– Comprehensive package of voice processing components
– Handles delay, jitter, packet loss and mobile environments
– Optimized for iPhone and Smartphones
– Efficient solution reduces CPU demandsEfficient solution reduces CPU demands
– Flexible and easy to integrate