Here was my command line with Staxrip on Windows:
"C:\Users\anon\Downloads\StaxRip-v2.44.4-x64\Apps\Support\avs2pipemod\avs2pipemod64.exe" -dll="C:\Users\anon\Downloads\StaxRip-v2.44.4-x64\Apps\FrameServer\AviSynth\AviSynth.dll" -y4mp "C:\Users\anon\Downloads\bootstrapper\『キャッ党忍伝てやんでえ』ビデオゲーム・アナウンストレーラー.webm_temp\『キャッ党忍伝てやんでえ』ビデオゲーム・アナウンストレーラー_new.avs" | "C:\Users\anon\Downloads\StaxRip-v2.44.4-x64\Apps\Encoders\SvtAv1EncApp\SvtAv1EncApp.exe" --input - --output "C:\Users\anon\Downloads\bootstrapper\『キャッ党忍伝てやんでえ』ビデオゲーム・アナウンストレーラー.webm_temp\『キャッ党忍伝てやんでえ』ビデオゲーム・アナウンストレーラー_new_out.ivf" --width 1920 --height 1080 --frames 6271 --rc 0 --crf 56 --progress 3 --preset 4 --fast-decode 2 --recode-loop 3 --keyint -1 --irefresh-type 1 --scd 1 --startup-mg-size 3 --enable-dlf 2 --noise-norm-strength 4 --psy-rd 0.5 --spy-rd 1 --color-primaries 1 --transfer-characteristics 1 --matrix-coefficients 1 --enable-tf 2
Generally speaking, with SVT-AV1-PSY you need to rely on specific programs like those in the webm thread
>>1072700, however, many of its features are set to be merged into mainline SVT-AV1.
https://gitlab.com/AOMediaCodec/SVT-AV1/-/releases/v3.0.0
Literally just announced.
So I think eventually you can do everything in FFMPEG when libsvtav1 is updated and don't have to hop through hoops with the SvtAv1EncApp binary accordingly. I just use Staxrip because it's very convenient and allows for frame-exact cutting and cropping, as seen with my 4:3 encode.
Nonstandard settings I use:
uses forward frames rather than keyframes for open GOP selection, however it tends to break seeking which users here don't like so feel free to use
and a 300-600 GOP for standard use. I just use forward frames because from my testing it reduces file size.
--noise-norm-strength 4
I cranked this up because the trailer seeks to replicate filmed cel-painted animation and noise needs to be retained, generally speaking for other use cases keep it at zero.
Refer to these articles for reference as they can explain AV1-PSY encoding better than I can.
https://wiki.x266.mov/docs/encoders/SVT-AV1-PSY
https://wiki.x266.mov/blog/av1-for-dummies
As a bonus, Illya and Miyu tush on the front page.