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 Skype, Microsoft Who others contributed to this? Ergo Esken, Senior Hardware Design Verification Engineer, Skype Markus Vaalgamaa, Principal Applied Scientist, Skype Kalle Koivuniemi, Senior Audio Engineer, Microsoft Mobile © 2015 Microsoft Corporation. All rights reserved. What is this guy talking about? • Estimate: over 100 million VoIP calls per day made from smartphones 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 • Huawei G750 • Apple iPhone 6 • Lenovo A788 • Samsung Galaxy S6 • Samsung Galaxy S4 mini • LG G3 • Samsung Galaxy Ace 3 • Samsung Galaxy Fame • Sony Z1 Compact • Microsoft Lumia 640 XL • Xiaomi Mi4 • Microsoft Lumia 640 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. .