Quicksync Encoder with B-Frames/Key Frame interval

[heyitskryptic]

Hello,

I recently switched to using Quicksync H.264 for my Twitch stream. I multistream, and use the NVIDIA HEVC encoder for my YT stream. I figured using Quicksync would take some load off of the GPU, and so far the results have been successful (I had previously been facing encoding overload running both streams from GPU).

The settings I am using for Quicksync are the following:

CBR
7500 Bitrate
Target usage: TU1
Profile: High
Keyframe: 1s
B Frames 0

I generally play high motion games, so the question I have is, what should I set my keyframe and b frames to in order to achieve maximum quality. I want to stress test, but want to set the "max" settings for those two in order to see how things respond...and lower as needed. With current settings I don't drop any frames and performance is good, I did notice minor blockiness/blur watching the VOD, so would adding b frames or adjusting keyframe help with this? Or is this the max setting. Thank you in advance (there is not much info out there regarding B Frames and Keyframe for Quicksync)

 

[qhobbes]

You should start with following the twitch Broadcasting Guidelines. 2 B and keyframes and 6000 bitrate.

Twitch Help Portal

help.twitch.tv

 

[heyitskryptic]

You should start with following the twitch Broadcasting Guidelines. 2 B and keyframes and 6000 bitrate.

Twitch Help Portal

help.twitch.tv

Appreciate the response, but that's not what I am asking. I am asking what the max quality setting would be for b frames and keyframe interval while using Quicksync.

The guidelines don't mention quicksync. The guidelines also aren't meant for "max" output...more of a "general" rule of thumb. For example, I achieve much better quality with NVENC while setting b frames to 0 vs setting it to 2 as it states. Secondly, Twitch will allow you to use 8000kbps as an affiliate...even though the guideline states 6k.

But yeah, I am hoping to find out what the max quality settings would be using Quicksync (without taking into account system limitations). I want to stress test on max and work my way down.

 

[Suslik V]

B-frames always worsens the quality. Saved bitrate will be spend in other places and may improve perceptual quality of the final footage. Frame by frame comparison almost always loses with more B-frames (original vs encoded comparison) no matter what encoder was used.

 

[heyitskryptic]

B-frames always worsens the quality. Saved bitrate will be spend in other places and may improve perceptual quality of the final footage. Frame by frame comparison almost always loses with more B-frames (original vs encoded comparison) no matter what encoder was used.

Thank you for confirming!

 

[koala]

Quicksync in general isn't able to produce as good quality as nvenc for bitrate-based rate controls. It needs more bitrate for the same quality. So it doesn't matter for using CQP/ICQ rate controls for recording. But for CBR/VBR for streaming it matters, since bitrate is constrained.
So if you encounter more "blockiness/blur" that's due to Nvenc simply being better than Quicksync. It's not a matter of settings, it's how the encoder works internally.

For streaming, I would say changing from Nvenc to Quicksync is a downgrade.

 

[heyitskryptic]

Quicksync in general isn't able to produce as good quality as nvenc for bitrate-based rate controls. It needs more bitrate for the same quality. So it doesn't matter for using CQP/ICQ rate controls for recording. But for CBR/VBR for streaming it matters, since bitrate is constrained.
So if you encounter more "blockiness/blur" that's due to Nvenc simply being better than Quicksync. It's not a matter of settings, it's how the encoder works internally.

For streaming, I would say changing from Nvenc to Quicksync is a downgrade.

Thank you. I had been using NVENC and HEVC together for the longest time for my multistream. But over the last few days, I started getting encoding overload, even though no settings had changed (weird because it worked flawlessly for months)...so that's why I explored the Quicksync option.