Question / Help Media Foundation: Exceeding bitrate / CBR not working

[Se1pher]

Hello
Why OBS MP completely ignores max bitrate(cbr) settings?
For example if set 3000max sometimes it jumps to 4,500? And much important question - how to prevent from this?
(OBS MP ver. 0.12.3)

 

[raindeeers]

Make sure CBR (Constant Bit Rate) is enabled.

 

[Harold]

Are you using one of the media foundation encoders?

 

[Se1pher]

2raindeeers:
Enabled

2Harold:
Yes, something wrong with it?

 

[Harold]

those encoders don't actually support CBR properly. Blame microsoft.

 

[Se1pher]

So, what point of this encoder then?
There is no chance of fixing it in near future?

 

[Harold]

The media foundation encoders are going to be replaced with better ones in the near future.

It's still not recommended to stream with nvenc or vce regardless of that due to the quality per bitrate of those encoders.

 

[Se1pher]

2Harold:
"better ones" still will require high bitrate?

 

[Harold]

The better encoders will still require higher bitrate than x264, that part is a limitation of the encoding hardware.

 

[Jack0r]

In short: Hardware Encoders like QuickSync, NVenc and VCE need more bitrate to reach the same quality as the x264 cpu encoding (on the very fast preset). It can also depend on the generation of the encoder you use. Older chips might give you even worse results.

OBS-Studio currently uses "Media Foundation" to support the hardware encoders. In the future it is planned to replace Media Foundation with a native implementation of the different encoders directly into OBS-Studio at which point they will probably also support proper Constant Bitrate.

In general we recommend to use x264 for streaming and the hardware encoders for local recording to get the best result at normal streaming bitrates. You can of course use the hardware encoders for streaming too but you will have to accept a lower quality at normal streaming bitrates in most cases.