Best practices from billions of calls
summary
Reverse engineering of WhatsApp, FaceTime, Skype, Viber, Wire and Facebook Messenger reveals concrete practices: FaceTime uses H.264 (H.265 off on Wi‑Fi to save battery), SDP negotiates resolution, and global Akamai TURN distribution reduces latency; many apps adopt a relay-first candidate allocation to cut call setup time then switch to P2P; Wire and Messenger tune Opus aggressively—Opus tuned to 18–25 kbps on 2G/3G—while Skype dynamically adjusts sampling rate, packet frequency and bitrate; Wireshark alone proves insufficient so node‑pcap + Highcharts visualization is used.
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chapters (15)
- 0:00Intro
- 0:33AMAZON MAYDAY TRACE
- 0:58SHIFT TO MOBILE
- 1:38LESSONS LEARNED ADAPTION TO MOBILE PLATFORM CODEC TUNING ENCRYPTION ON HEAVY-LOSS NETWORKS
- 3:12H.264 NO H.265 ON WIFI
- 3:41USES TURN SERVERS
- 4:09WHATSAPP VOICE CALLS
- 5:18ALWAYS RELAYED FOR THE FIRST FEW SECONDS SWITCH TO P2P REDUCES CALL SETUP TIME
- 6:26SKYPE
- 6:41TESTING ON SINULATED 2G, 3G, 46 DYNAMICALLY ADAPTS SAMPLING FREQUENCY, PACKET RATE AND BITRATE RELAY SERVERS IN REDMOND
- 7:12WIRE AUDIO, TEXT AND PICTURES
- 7:23USES OPUS BROWSER INTEROP USING WEBRTC DTLS FOR ENCRYPTION
- 8:27HEAVILY TUNED FOR A GOOD AUDIO EXPERIENCE
- 9:52DTLS WHEN TALKING TO BROWSERS SDES BETWEEN APPS
- 10:30ADAPTION TO MOBILE PLATFORM NETWORKS WITH HIGH PACKET LOSS AND DELAY DEVICES WITH CONSTRAINTS ON CPU POWER AND BATTERY USAGE AUDIO MORE IMPORTANT THAN VIDEO
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