I’m using video download helper, an extension for firefox https://www.downloadhelper.net/ and it can download about every video from web site. At one time it was not able so it asked me to install a Companion App and with it was able to dl from anime site and all.
I worked in the media broadcasting, we had an internal lib to scale/convert whatever format in real time, and it went from basic operation, to SSE3, to AVX512, to CUDA, and yes crafting some functions/loops wit assembly can give an enormous boost.