Question / Help Bitrate still fluctating even with CBR?

[Anonanon]

I thought CBR meant you are telling the encoder to use a flat bitrate number through the whole stream, but OBS studio, R1CH's analyzer and Twitch playback are all showing signs that the bitrate is fluctuating all the time. My video bitrate is 1550kbps and audio bitrate is 64kbps. Am I not able to make this graph a completely flat line on 1550kbps? I tried playing around with the buffer setting: no custom and 1550 both have fluctations and 0 spikes to 3000 and up which appears to be VBR behavior if anything.

 

[Harold]

Internet conditions make it impossible to actually get a perfectly flat bitrate line all the time.

 

[sam686]

Could reduce the buffer size down to 100 but the keyframe quality will suffer badly.

The old OBS have "Minimize network delay" option that makes the network send usage more stable, which reduce lag with online games, which i can't find on new OBS.

 

[Harold]

Numbers chasing like this won't actually improve quality, just as a heads up.

 

[Anonanon]

Numbers chasing like this won't actually improve quality, just as a heads up.

I feel like when I play high motion games like Quake Live or racing games, the spikes will occur much more often and top out at 3000kbps, possibly being an issue to some low bandwidth viewers (I'm not partnered for the quality switch). The following is an example of an extreme situation to make a point:

From my testing last night, I learned that a custom buffer size of "0" is not off, but rather auto. So I tried to see what would happen if I used 1kbps, and I got the keyframe pulsing issue sam686 described. Eventually I found a setting that would give me very minor fluctation, where it's effectively a flat line more or less but the keyframe pulsing effect has faded away. For a max bitrate of 1500kbps, the custom buffer would have to be on 300kbps.