You can get a free beta h.265/HEVC CLI encoder from the DIVX website. It's not optimized, and last I checked, it encoded about 15 times slower than x264 to output video about 40% smaller in file size than high profile x264. Quality is quite impressive for the file size, but is noticeably more lossy than well encoded h.264. It's not that it's bad - it's just slightly less accurate thus far. Detail and motion are fine, but the overall impression is of some loss in color vividness - but which you'd only know through direct A/B comparison.
If you want to try the DIVX h.265 beta encoder, search the DIVX site for just that. You don't need (& probably wouldn't want) any full DIVX package (or profiles) just to use the h.265 beta encoder. To convert directly from h.264, you don't need to first decompress the h.264. You can, instead, easily pipe from FFMPEG to the h.265 encoder (sample simple CLI syntax should be available from DIVX). It will only output raw .HEVC - but which you can then easily mux into an MP4 or MKV container using MP4Box or MKVToolnix. Playback is no problem if you have current versions of either VLC or LAV codecs. On Android devices, the MX player can play back h.265 - but not yet HD since there's not yet any hardware support.
Although I haven't checked this, I rather doubt that Youtube currently accepts h.265 encodes, and very much doubt that this will help with your problem of your HD videos not looking very good on Youtube. But if you need to fit something close to bluray quality video on a DVD, or 4K video on a bluray disk, and if the lengthy encoding time isn't a concern (maybe you have a spare computer otherwise sitting around doing nothing), then encoding to h.265 is a current viable option.