Question / Help CBR goes obove limit

[TheIcon]

I am using NVEnc and set the bitrate to 8mbps for streaming to Youtube. I notice that the bitrate a lot of times goes above that. Any idea why? Is it possible to stop it?

Thank you

 

[Boildown]

H.264's constant bitrate isn't actually constant, it can vary in accordance with the buffer size. To keep your bitrate "more constant" (it will always vary somewhat based on the complexity of the video), use a smaller buffer.

 

[TheIcon]

How small? Can you give an example for 8mbps?

 

[FerretBomb]

No. You'll need to test and see through trial and error. There will not be a "hard limit" though with any value, just a somewhat reduced variance.
This is why it is not advised to stream using more than 2/3 of your available throughput (or 1/2 if you are playing an online multiplayer game, to allow for game network overhead). That and normal network fluctuation.

 

[Boildown]

The normal recommendation for OBS (which was tweaked around Twitch, not YouTube) is to match your buffer to your bitrate. So if you stream at 8000kb/s, set 8000kb as your buffer.

However, I stream to Twitch at 3000kb/s with a 2000kb buffer, and I think it works really well. You might experiment with 8000kb/s stream and a 6000 or 5000 kb buffer. Or lower than that. The thing to be aware of is as the buffer gets smaller, your video quality will go down, especially in high-motion sequences. If all you're doing is playing Hearthstone, you can probably set the buffer to 4000kb and not notice much of a difference. If you're playing BF2, you'd see a difference though, right away (theoretically).

In the end, FerretBomb is right, you need to test it and figure it out for yourself through experimentation.