Starting at the top in the encoding tab, bitrate was increased from 3500 to 4000, this immediately provides a boost to quality going from 0.063bpp to 0.072bpp (bits per pixel). It should be noted here that you should never go above 3500 unless given permission from twitch. Non-partners should try not to go above 2000. Second in the encoding tab was changing the audio bit-rate from 128kb to 160kb, twitch supports a maximum AAC bit-rate of 160kb so we upped this for a slight increase in audio fidelity.
Next up in the video tab we changed from the Bi-linear downscale filter to Lanczos. The Lanczos filter uses 36 samples of the image to provide a smoother downscale at the cost of some performance which is this case is acceptable. This is important to things like text and other objects that alias easily when being downscaled.
Lastly we come to the advanced tab. This is where the most significant changes were made. Process priority class was increased to "above normal" from "normal". Generally on a 1 PC setup this is not advised, however on a 2 PC setup where one machine is dedicated to encoding, you want the encoder to be a higher priority process so it is not interrupted by background system processes. DON'T do this is you have a single PC setup as this will cause encoding to become higher priority than the game. Next x.264 CPU preset was changed from "Faster" to "Medium" this is a pretty big change if not the biggest. Given that cohh has a dedicated 6 Core CPU for encoding this is a nice upgrade to video fidelity without the need for increased bitrate. Even on a dedicated 6 Core machine this causes CPU usage to sit around 65-75% which is considerable; basically don't try this at home unless you know your system can handle it. Next the encoder profile was changed from "main" to "high". Again this change provides additional fidelity for the same bitrate with 1 major drawback. Some legacy mobile devices cannot decode this profile (sorry flip phone users). Without going to in too much detail High Profile enables additional feature in the encoder such as "8×8 vs. 4×4 transform adaptivity," and "Quantization scaling matrices," which in laymen terms equates to more efficiency in a lossy encoding format like x.264. While Twitch recommends that you use main in order to maintain compatibility with more devices, in practice there are very few devices these days that cannot decode the high profile. Last but not least we enabled CFR (Constant Frame Rate). This is not really necessary unless you plan on editing your videos for youtube (or similar). This basically forces the encoder to possibly duplicate a frame if necessary to ensure a constant framerate which makes editing much easier as tracking is now consistent by frame by frame (You're welcome RedEyeMonster).
That's it, I hope you found this useful! If you have any questions drop them in the comments and I'll be checking it here and there.
Cheers!
-izl
