Question / Help CBR with QuickSync fluctuates heavily in bitrate.

[PrinceVinc]

https://gist.github.com/1dc378099c8aaf9a15e0f92a187c028d

I am using Quicksync to stream and have a weird issue?

I set a CBR of 6506 (which becomes 6666 with Audio and is 2/3 of my upload speed)

Question being... the bitrate fluctuates pretty heavily!
From as low as 4000 as high as 9000 is that normal that it fluctuates this much/high?

It looks more like VBR than CBR

 

[Boildown]

That log doesn't show you actually streaming with Quicksync, you set it up but don't use it, then stream with NVEnc.

 

[PrinceVinc]

That log doesn't show you actually streaming with Quicksync, you set it up but don't use it, then stream with NVEnc.

Wait what does the log show than?

I stream with Quick Sync and Record with Nvenc.
CPU usage is to high on recent games so I have to use those, two.

I mean it clearly is not the CPU so it must use something xD

 

[Stiverson]

I use quicksync to stream, and i absolutely can confirm this. I use vbr and its a lot more stable. It looks a lot smoother, and twitch inspector/twitch have never had an issue. Not sure why.... but im streaming around the 2000 with a max brate of 2800 range, so it could be slightly different for you. Wish i could be more help to the route cause of this.

 

[PrinceVinc]

So it goes how much above 2800 for you?

 

[PrinceVinc]

Bump since this is still a present "issue"

 

[Boildown]

Post a log file of a stream of at least five minutes of high-action gameplay (not just standing around in-game). Make sure to close out of OBS after the stream session to force it to write the log file to disk from memory, so that the entire log file will be there when you post it.

 

[PrinceVinc]

Here you go https://hastebin.com/cofebifora fresh out of the Oven Fluctuated between 5000 and 8000 @Boildown

 

[Boildown]

15:20:39.004: rate_control: CQP
15:20:39.004: bitrate: 0
15:20:39.004: cqp: 30

This is a variable bitrate mode, not a constant bitrate mode, so of course the bitrate fluctuated.

 

[PrinceVinc]

Thats my Nvenc setting for recording, I have QuickSync set up for streaming.

I do both at the same time.

 

[Stiverson]

I had the same issue. Not sure how relevant it is because i stream around 1500, but vbr is much more stable. Ive never had a twitch issue and my test charts confirm.

 

[PrinceVinc]

so, still no answer to as to WHY it fluctuates so much? I set my Bitrate to 6506+160 for Sound which amounts to 6666 total, but it goes as high as 9000+ at times despite CBR set.

10000 is my Max Upload so somehow forcing it to not go beyond my set limit would be great and the very reason I use CBR in the first place.

 

[Boildown]

Constant bitrate video still varies its bitrate moment to moment according to video complexity, just to a lesser degree than variable bitrate video. Reduce the buffer size to reduce the amount it can vary.

 

[PrinceVinc]

Constant bitrate video still varies its bitrate moment to moment according to video complexity, just to a lesser degree than variable bitrate video. Reduce the buffer size to reduce the amount it can vary.

How do I reduce the buffer size? Ever since OBS Studio the Option "vanished". Guess I just have to hope that it won't cause Issues, which it thankfully never did except for a very few Dropped Frames.

 

[Boildown]

That's an excellent point, I only see the custom buffer size checkbox for x264 encoding, not NVEnc. My current computer doesn't have the Quicksync option (which is weird because it does have Quicksync available in OBS Classic) so I can't check if its on that one.

I previously noted this problem here: https://obsproject.com/forum/thread...d-to-20k-bitrate-for-month.80407/#post-338901
and here: https://obsproject.com/forum/threads/i-need-a-way-to-limit-my-bitrate-to-4000kbs.74636/#post-317425

R1CH says to use low latency mode in that last thread, so you might try that.