I think it is worth posting Tom Vaughan [1]( Father of x265 )'s reply here. >FFMPEG is a media processing framework. It's great for simple media processing jobs (builds a graph, runs the graph). A build of "FFMPEG" includes that media processing framework plus dozens of open source libraries (filters) that do the actual work (x265, x265, libav, etc). >So "FFMPEG" gets a lot of well deserved credit (it's the framework…
The most well-known 3rd party libs provide a few (albeit commonly used) video encoders. Of course, having interfaces for these external libs is what allows media operations to be consolidated into a single process workflow. As standalone tools, x264/x265 would be more cumbersome to integrate into a pipeline.