Jonathan Christensen's Presentation at eComm 2009

Who Cares About Codecs? Jonathan Christensen eComm 2009

80 – 14,000 Hz

400 – 3,400Hz

End to End Electronics

The Digital Era PCM – G.711 8kHz Samples (.125MS) Each Sample is ~13 bits Encoded to 8bits 3.4kHz of Bandwidth

Wideband Audio 16kHz Sample Rate ~8kHz Bandwidth Or 50 – 7000Hz.. New, Open Transport Layer

NEW! Super Wideband More Samples More Fidelity The Next Building Block Voice 2.0

;-)

;-(

;-) 50 – 12,000Hz

Demo

Female and Male speech

Each encoded 3 times

PSTN quality

Wideband

Super wideband

Recognize, Decipher, Enjoy

Recognize who is talking (esp. in a conference)

Decipher tricky sounds

Are we “failing” or “sailing”?

Hear through doubletalk

Decode background noise

Understand faint talkers

Its like being there…..

G.711, G.722, G.729, iSAC, iLBC, AMR-NB, VMR-WB, SPEEX, G.722.1, GSM Half Rate, AMR-WB G.718, G.719, G.722.2, G.723, G.723.1, G.728, GSM Enhanced Rate, HVXC, FS-1015, FS-1016, ADPCM, RTAudio, iPCM-WB, G.729a, GSM Full Rate, MELP, IMBE, RCELP, VSELP, CELT

Choices?

AMR-WB (3GPP for IMS)

Efficient, High Quality

Only 7kHz (Wideband-ish)

Royalty based licensing

SPEEX

OK quality, reasonable efficiency

Open source, free

RTAudio (Microsoft)

OK quality

Microsoft licensing

Announcement SILK Licensing Program Skype will offer SILK royalty free for license by third party developers. SILK is our primary / signature super-wideband audio codec. SILK is now the default audio codec for all Skype-to-Skype audio calls on Skype for Windows (Mac & Linux coming soon) Interested parties can get more information at: https://developer.skype.com/silk

About SILK

Designed and developed by Skype Audio team

State of the art internet speech coder

Scalable / variable bit rate from 6 – 40kbps

Portable (Fixed Point ANSI C)

Lightweight (Low- bit rate, delay, CPU, memory, code size)

Robust to jitter and packet loss

Flexible / multiple modes

8kHz Narrowband for PSTN gateways and low end devices

16kHz Wideband for PC applications and smart devices

24kHz Super-Wideband - a new standard for speech quality

Mean Opinion Score (MOS) Results MOS (Mean Opinion Score) listening test was performed by Dynastat, an independent 3 rd party laboratory. Confidence intervals (95%) are +/- 0.1 MOS. All bitrates are measured and averaged over frames containing active speech. All audio signals are Wideband. SILK and Speex were run in the highest complexity mode.

Robust to Jitter & Packet Loss MOS scores for Wideband speech signals at different packet loss rates. All codecs were operated at a bitrate of 18.25 kbps.

Supporting Partners

What bloggers are saying…

"The new, efficient Silk audio codec produces class-leading sound for video and voice, earning Skype our Editors' Choice for video calling."

http://www.pcmag.com/article2/0%2C2817%2C2341413%2C00.asp

Skype 4.0 is the best Skype yet, bar none…Perhaps the biggest improvement, though, is audio quality . We all thought that Skype audio was great, right? Skype’s internally developed SILK codec... A wideband codec that delivers the goods at half the bitrate of prior codecs, SILK makes talking on Skype a pure pleasure … The difference is noticeable, and worth the download alone.