Antti Kelloniemi Ergo Esken Kalle Koivuniemi Markus Vaalgamaa ETSI Workshop on Telecommunication Quality beyond 2015 Vienna, Austria, October 21st ‐ 22nd 2015 Who is this guy?

Antti Kelloniemi, D.Sc. (Tech.) Principal Program Manager, Device Call Quality , Who others contributed to this?

Ergo Esken, Senior Hardware Design Verification Engineer, Skype

Markus Vaalgamaa, Principal Applied Scientist, Skype

Kalle Koivuniemi, Senior Audio Engineer,

© 2015 Microsoft Corporation. All rights reserved. What is this guy talking about?

• Estimate: over 100 million VoIP calls per day made from and tablets • Over half of Skype calls on mobile have video on • 64% of video calls and 28% of audio calls are in speakerphone mode • Handsfree quality is crucial for any mobile user • Call quality MOS is lowest in Audio endpoints used in Skype calls in mobile devices speakerphone, highest in headset calls

© 2015 Microsoft Corporation. All rights reserved. What is this guy talking about?

Echo cancellation in handheld handsfree mode ‐ Challenging case for AEC processing due to strong acoustical coupling, compression, distortion, etc. ‐ 3GPP TS 26.131 and TS 26.132 define the test method and requirements for calls in GSM, 3G, LTE networks (NB to FB) ‐ Codec, processing, used microphone(s), etc. may be different for VoIP

© 2015 Microsoft Corporation. All rights reserved. What’s the test setup they used?

• Testing done with Head Acoustics ACQUA test operating system, in unrestricted (lossless) network conditions • Calls were done in speakerphone (hand‐held hands‐free) mode • GSM call test conducted between each phone and Rohde & Schwarz CMU 200 radio tester • Skype test conducted between each phone and Reference PC running Skype Win desktop • Phone was positioned on a table in anechoic room with artificial mouth and measurement microphone at reference 40 cm distance In / out acoustical © 2015 Microsoft Corporation. All rights reserved. In / out

Tested phones

• Apple iPhone 6 plus • G750 • Apple iPhone 6 • A788 • • mini • LG G3 • 3 • • Z1 Compact

• 640 XL • Mi4 • LTE GSM hand‐held hands‐free calls –NB and WB Good 80 70 (dB)

60 TCLw 50 40 30 attenuation

20 10 Echo 0 Bad

© 2015 Microsoft Corporation. All rights reserved. NB WB Skype hand‐held hands‐free calls ‐ WB Good 80 70 (dB)

60 TCLw 50 40 30 attenuation

20 10 Echo 0 Bad

© 2015 Microsoft Corporation. All rights reserved. NB WB Skype WB* *) using phone’s internal AEC processing What were the key findings?

• Echo cancellation performance in VoIP calls is not correlated to AEC in GSM calls • Even when TCLw results are good, short echo bursts may be audible in Skype calls • Latency is stable in GSM calls, unlike in IP communication

© 2015 Microsoft Corporation. All rights reserved. What are the proposals?

• Test and tune also VoIP audio path –in particular on speakerphone mode –as video calling apps are increasingly popular • In Android: MediaRecorder.AudioSource VOICE_COMMUNICATION • Enable both DRC and AEC in comm mode (VOICE_COMMUNICATION) and neither in raw mode (DEFAULT) to give VoIP apps a choice • Take into account the longer and more variable latency in IP networks, even in good conditions • Use robust algorithms to cope with packet loss and jitter happening in low quality networks • Test and tune the algorithms for all supported audio frequency bands

© 2015 Microsoft Corporation. All rights reserved.