Video Chat stutter (Threema and signal)

I experience a strange behaviour with my Fairphone 5. When I make a video call with somebody via Threema or Signal, the connection is stuttering every few seconds (the picture is not moving and a second of sound is missing). I did not experience the same problem with an iPhone or a Fairphone 3, so I think it is not network related. Also a video call using WhatsApp is working fine. The problem is also present, if I call somebody in the same room.
So far I tried every permutation of the trouble shooting settings within Threema, without solving the problem.
Did anybody experience a similar problem and found a solution?

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In the Signal app both parties should use the peer to peer setting for optimal performance. Settings → Privacy → Advanced → Make sure the call relay option is turned off for both clients.

Did the Signal setting suggestion help? It may also be a network issue, for that you can run this bufferbloat test:

Thanks for your input.
It took a while to confirm the settings of the signal app. Both devices have the routing over the signal servers disabled. So this should not be the problem.
But your second post might be on to something. I did the bufferbloat test and only reached a C rating. Ping is increasing a lot (from 20 to 200 ms) if the connection is under load. So this might be the problem. And I will look into it, if this can be solved or if I can test the video call on another WLAN.
The only thing I do not understand is, why other phones on the same network do not have the same problem (Fairphone 3 and iPhone 8 work both fine).

Maybe something is setup on your router to prioritize some network traffic. Or some other kind of QoS type of thing. Or maybe other apps use a better compression algorithm and thus it performs better. But by improving your network, you will benefit for sure. Do you also have the same issue on 5G?

I can confirm this behaviour in signal… I think I see a pattern, though. Do you per chance use bluetooth audio? Next time I’ll check with loudspeaker, if yes


I checked the call quality, when using a mobile data connection (only 4G in my case) and the stutter was gone. Thanks for the suggestion! This is at least a good workaround until I run out of data volume.
So this really seems to be a problem that happens with the WiFi connection. So far I could not test it with a different WiFi network, to find out if it is related to my home network (which now seems likely) or the Fairphone 5 beeping involved in some kind.

Still think it would be hell of a coincidence, if my WiFi network suddenly became bad when I switched the phone.

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Thanks for the suggestion.
I often use Bluetooth headphones, but not in video calls. And audio only calls without video worked fine so far, even with Bluetooth headphones and with all tested apps (Threema and Signal).

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As I mentioned before, I think it has to do with Signal. They probably don’t use the same level of compression as other messengers, like WhatsApp. Maybe that’s due to their privacy ethos. They use peer to peer and maybe that limits their bandwidth compression for some reason. So it seems very likely that it’s due to bufferbloat. You can check your WiFi settings and look for QoS (quality of service) or other prioritization settings.

I had the same issue, Teams and Jitsi worked fine, but Signal did not. Changing the QoS settings solved it for me.

Had time for some additional testing.
I reactivated my old iPhone 8 to do a comparison. I was calling a Fairphone 3 on my home WiFi, while all phones were in the same room. I only used Threema and not Signal.
iPhone 8 to FP3: video call was fine without any stutter
FP5 to FP3: instant stuttering every few seconds
Repeating iPhone 8 to FP3: video call was fine without any stutter

Then I tried to repeat the test with 4G
FP5 on 4G to iPhone 8 on WiFi: video call was fine without any stutter

Then I repeated the waveform bufferbloat test:
FP5: rating C with 20 ms without load, +40 during download and +180 during upload
iPhone 8: basically the same result with single digit differences

So I was wondering: same WiFi, same app, same waveform results. There must be a difference of the FP5 that triggers the problem. Then I finally realised, it might be the camera. FP5 features 50 MP camera while the iPhone only has 7 MP. Even with compression this might make a big difference on how much data is send during the video call. The higher data rate of the FP5 seems to trigger the bufferbloat while the lower resolution of the iPhone 8 does not trigger the problem.

So yes, you were right all along. Sorry for taking so long to understand how this can only happen on the Fairphone 5 and not affect the older phones.

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That’s indeed also a factor to consider, I didn’t think of that. Hopefully you’ll be able to improve the connection with some tweaks in your router.

I have exact the same issue with Facebook Messenger voice and video calls. I didn’t notice this on Discord and WhatsApp applications. I tried almost everything when I add all permissions, clear cache which doesn’t help. Only whats looks help on begin was uninstall Lucky Patcher, but after few days issue comes back O-o when I already closed support ticket on Fairphone…

Isn’t there a way to reduce the sent image quality? The FP5 is obviously not sending a 50MP image during video calls, instead the FP5 should reduce the image size already before the app handles and transfers it (and might reduce the image quality due to speed issues). 50MP is completely useless when the phone call stutters. I experience that on Telegram and Threema.