I often get disconnected on Signal after 20 minutes or so on a voice call, but I suspect that's due to the other end being behind a VPN with awful latency.
WhatsApp is, I agree, very good quality for what it is, but I would never trust it or FB with anything but social/personal calls. Social Media platforms are for other people to hand over their lives to. Let them subsidize my detachment from their usage, and I thank them for it. I'm sure there will come a day where you can't use WA without a FB account, at which point it is dead to me and my social contacts will be the first to know about it via WA.
"WhatsApp calls are also end-to-end encrypted When a WhatsApp user initiates a call: 1 The initiator builds an encrypted session with the recipient (as outlined in Section Initiating Session Setup), if one does not already exist 2 The initiator generates a random 32-byte SRTp master secret 3 The initiator transmits an encrypted message to the recipient that signals an incoming call, and contains the SRTp master secret 4 If the responder answers the call, a SRTp encrypted call ensues"
From wikipedia:
"Signal voice calls are encrypted with SRTP and the ZRTP key-agreement protocol, which was developed by Phil Zimmermann.[1][57]"
So from where I'm reading they seem to be doing more or less the same thing when it comes to encrypting voice calls.
https://www.whatsapp.com/security/WhatsApp-Security-Whitepap... https://en.wikipedia.org/wiki/Signal_(software)
Are you saying "maybe/maybe not"?
If they seem to be doing something that is "more or less" the same then my radar is triggered for them not actually declaring they are delivering totally encrypted (ie no backdoor tomfoolery) voice calls.
ZRTP makes negotiation possible, so a roll-out of opus should be possible without breaking older clients.
But no worries... there are a ton of moving parts in these protocols, and even though I've been working with them for a while, I still tend to forget details here and there, too.