Question / Help Max Bitrate and Buffer Size help needed

[GlassHalfAwesome]

Hey,

Maybe I'm misunderstanding the Buffer Size feature but I'm streaming a game that 95% of the time runs fine at 1000kbps but can occasionally get some spikes of high motion/action and can use up to 2500mbps (maybe a little less.) I set the max bitrate to 1000 and the Buffer Size to 2500 but it doesn't seem to help at all. Here's an example:

960*640, 60 FPS, 1000kbps bitrate, 2500 buffer size

http://www.twitch.tv/testgha/b/469987606?t=11s

At ~17 seconds the lightning flashes and the video quality goes to hell. When I change the bitrate to 2500 or higher it remains smooth at all times:

960*640, 60 FPS, 2500kbps bitrate, custom buffer size disabled

http://www.twitch.tv/testgha/b/469988967?t=11s

At ~17 the video is perfect and quality never drops. The problem is that the bitrate is now almost 3x higher than it needs to be for 95% of the playthrough. Changing the bitrate to 1500 provides excellent quality during the slow sections and slightly better quality during high motion but I'd prefer to avoid that compromise.

Is there anything I can do? Am I misunderstanding how buffer size works?

Thanks for your time

 

[Krazy]

If you can stream at 2000 bitrate, that would probably be the best for your chosen resolution/FPS. Generally using custom buffer sizes doesn't actually help. It's fairly complicated and I don't even fully understand all of what using a custom buffer does, but it's almost always best to just leave it the same as your bitrate.

 

[GlassHalfAwesome]

I did some more testing and it looks like 1800kbps is the lowest I can get away with and keep everything looking good. Can anyone else offer an explanation as to what the customer buffer size actually does? I've read through the help documentation and it says it can be changed to a higher value for moments of high motion (at the cost of a fluctuating bit rate) but it doesn't seem to work

 

[dodgepong]

Are you using CBR?

 

[GlassHalfAwesome]

Are you using CBR?

Yes, it's enabled. I didn't know what it did because when I mouse over it there's no tooltip popup. I just read the help and I'm pretty sure this is what's wrong. I feel pretty dumb. I'm going to go test it out

edit: that did it! Thanks so much dodgepong :D I disabled CBR, quality is at 8 and bitrate is set to cap at 3000 (although I don't think I'll ever hit that.) Here are the results:

A Link to the Past GBA

Average: 600kbps
Max: 1700kbps

Pokemon Fire Red

Average: 500kbps
Max: 1300kbps

The Wind Waker

Average: 1400kbps
Max: 2500kbps

I have a bandwidth cap so it's nice not having to waste 2/3s of my stream data for the spikes that may happen. Thanks again!

 

[dodgepong]

Er, if you're streaming on Twitch, CBR is what they want you to use. CBR is better for viewers so that your bandwidth requirements aren't constantly changing.

 

[Engbob123]

I found this video to be very helpful and allows me to record locally and or stream in full 1080p. The Bitrate is explained quite well here:
https://www.youtube.com/watch?v=iOQm3H_qfeQ