Question / Help Bitrate always drops when streaming but upload speed is stable

[Hitman89]

Hey,
i'm having a weird issue here and i really hope you guys can help me solve it.
I live in Tunisia (north africa) and i stream on twitch (Europe: France, Paris), the problem is whenever i stream, the bitrate just drops out of nowhere, i've only streamed around 10 times so far and i've had low bitrate issues at least 7 times.
I use a 4G connection (4G router connected to my pc via an Ethernet cable) cuz my dsl connection only has 1mb upload...
These are 2 upload speed tests:
Tunis server:

Paris server:

When i test my connection using the Twitch Bandwidth Test tool my bandwidth never drops under 3900kbps

I also regularly upload videos to youtube and i can see (through a tool called Net Traffic) that my upload speed never really drops so i don't understand why my bitrate always drops to 1000kbs ~ 1500kbs sometimes even lower almost everytime i stream so i have to change the bitrate midstream from 2500kbs to something like 1400kbs to stop those frames from dropping.

I really have no idea what to do so i can finally have a clean 720p 30fps 2500kbs stream and i hope you guys can help me out, thank you in advance!

 

[Hitman89]

Bump

 

[Narcogen]

Your ISP is likely seeing your streaming traffic and deliberately reducing the performance of that stream. That's why the problem only happens while you're actually streaming and doesn't necessarily show during short-term tests. In terms of measuring expected streaming performance, TwitchTest is a good one to use-- general speed testers like speedtest.net are of little practical use.

 

[Hitman89]

Your ISP is likely seeing your streaming traffic and deliberately reducing the performance of that stream. That's why the problem only happens while you're actually streaming and doesn't necessarily show during short-term tests. In terms of measuring expected streaming performance, TwitchTest is a good one to use-- general speed testers like speedtest.net are of little practical use.

Why would my ISP reduce my upload speed when i stream but not when i upload a youtube video (which takes over an hour with stable upload speed throughout the whole process) or when i have an hour long "bandwidth test mode" stream? (i attached a log file for this test stream i just ran in case it helps)

 

[Narcogen]

Youtube uploads don't have to be realtime. Bitrate can fluctuate without having a huge effect on the total time needed.

YouTube uploads aren't sent via RTMP. So a network router that knows RTMP should be prioritized would consider that traffic high priority. In order for the ISP to prioritize RTMP traffic it likes (say, corporate clients using Microsoft LYNC) they might well choose to drop or reset those sending to other destinations, like YouTube or Twitch.

You could try testing some of these assumptions by seeing if you experience similar drops if you stream while connected through a VPN.

 

[Hitman89]

Youtube uploads don't have to be realtime. Bitrate can fluctuate without having a huge effect on the total time needed.

YouTube uploads aren't sent via RTMP. So a network router that knows RTMP should be prioritized would consider that traffic high priority. In order for the ISP to prioritize RTMP traffic it likes (say, corporate clients using Microsoft LYNC) they might well choose to drop or reset those sending to other destinations, like YouTube or Twitch.

You could try testing some of these assumptions by seeing if you experience similar drops if you stream while connected through a VPN.

Thanks for the suggestion! I just gave it a shot the VPN option a shot and the Twitch Bandwidth Test tool results were good (same as without the vpn) but the stream test i ran was a lot worse, the bitrate dropped even faster than usual.
I dunno what to do apart from getting a different ISP and praying that the new connection works fine with obs & twitch...