WebRTCAudio Codec
Opus & Processing Requirements
April 2014
Tsahi
Levent-Levi
Codec Types
• Throw away things that are not perceived by the human ear and
eye
• Compress the hell out of the rest
• RTC ...
Media Codecs for WebRTC
No Mandatory To Implement (MTI) video codec yet
(but we don’t care about it in this session)
4/4/2...
General Codec Characteristics
4/4/2014 4
Complexity
CPU
Latency
ms
Resiliency
Packet loss
IPR
Royalty payments
Voice Codec “Features”
4/4/2014 5
Bitrate
kbps
Sampling rate
kHz
Channels
Mono, Stereo, …
Hz and Hearing Ranges
4/4/2014 6
cochlea.org
Narrow, Wide, Super & Full
4/4/2014 7
Opus vs. The World
• Requires a lot of processing power
• Optimized for mobile in Opus 1.1
4/4/2014 8
Opus is Different
1. SILK - low bitrate speech
2. CELT - music and high fidelity
4/4/2014 9
Hybrid what?
4/4/2014 10
SILK CELT
Guidelines
• SILK modified to fit CELT
• FEC inherent in SILK
• All flow control done in-band
• Support hybrid modes of op...
Mobile
Getting better on mobile, where the focus is
4/4/2014 12
Servers
No improvements on servers
4/4/2014 13
Where does that leave us?
Architectural decisions of where
to position Opus in our network
4/4/2014 14
Thank You!
Tsahi Levent-Levi
http://bloggeek.me
tsahil@bloggeek.me
4/4/2014 15
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WebRTC Audio Codec: Opus and processing requirements

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WebRTC's mandatory codecs are G.711 and Opus. What exactly Opus is, how does it stacks up versus other audio codecs and what challenges does it pose for developers?

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WebRTC Audio Codec: Opus and processing requirements

  1. 1. WebRTCAudio Codec Opus & Processing Requirements April 2014 Tsahi Levent-Levi
  2. 2. Codec Types • Throw away things that are not perceived by the human ear and eye • Compress the hell out of the rest • RTC = Low latency in encoding and decoding 4/4/2014 2
  3. 3. Media Codecs for WebRTC No Mandatory To Implement (MTI) video codec yet (but we don’t care about it in this session) 4/4/2014 3 Codec Use Status G.711 Narrow band, selected for PSTN and VoIP interworking MTI Opus New flexible audio codec. Narrow to wideband support; Support for Speech & Music MTI VP8 Google’s open source codec ? H.264 Video codec (MPEG-LA licensing) ?
  4. 4. General Codec Characteristics 4/4/2014 4 Complexity CPU Latency ms Resiliency Packet loss IPR Royalty payments
  5. 5. Voice Codec “Features” 4/4/2014 5 Bitrate kbps Sampling rate kHz Channels Mono, Stereo, …
  6. 6. Hz and Hearing Ranges 4/4/2014 6 cochlea.org
  7. 7. Narrow, Wide, Super & Full 4/4/2014 7
  8. 8. Opus vs. The World • Requires a lot of processing power • Optimized for mobile in Opus 1.1 4/4/2014 8
  9. 9. Opus is Different 1. SILK - low bitrate speech 2. CELT - music and high fidelity 4/4/2014 9
  10. 10. Hybrid what? 4/4/2014 10 SILK CELT
  11. 11. Guidelines • SILK modified to fit CELT • FEC inherent in SILK • All flow control done in-band • Support hybrid modes of operation 4/4/2014 11
  12. 12. Mobile Getting better on mobile, where the focus is 4/4/2014 12
  13. 13. Servers No improvements on servers 4/4/2014 13
  14. 14. Where does that leave us? Architectural decisions of where to position Opus in our network 4/4/2014 14
  15. 15. Thank You! Tsahi Levent-Levi http://bloggeek.me tsahil@bloggeek.me 4/4/2014 15
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