[fpiraneo@coder ~]$ ffmpeg -h encoder=libx265
ffmpeg version 4.0.2 Copyright (c) 2000-2018 the FFmpeg developers
  built with FreeBSD clang version 6.0.0 (tags/RELEASE_600/final 326565) (based on LLVM 6.0.0)
  configuration: --prefix=/usr/local --mandir=/usr/local/man --datadir=/usr/local/share/ffmpeg --pkgconfigdir=/usr/local/libdata/pkgconfig --enable-shared --enable-pic --enable-gpl --enable-postproc --enable-avfilter --enable-avresample --enable-pthreads --cc=cc --disable-alsa --disable-libopencore-amrnb --disable-libopencore-amrwb --disable-libass --enable-libbs2b --disable-libcaca --disable-libcdio --disable-libcelt --disable-chromaprint --enable-libcodec2 --disable-libdc1394 --disable-debug --enable-htmlpages --enable-libdrm --enable-libfdk-aac --disable-libflite --enable-fontconfig --enable-libfreetype --enable-frei0r --disable-libfribidi --disable-libgme --disable-libgsm --enable-iconv --disable-libilbc --disable-libjack --enable-libkvazaar --disable-ladspa --enable-libmp3lame --enable-libbluray --disable-librsvg --disable-libxml2 --disable-lv2 --enable-mmx --disable-libmodplug --disable-libmysofa --disable-openal --disable-opencl --enable-libopencv --disable-opengl --enable-libopenh264 --disable-libopenjpeg --enable-optimizations --enable-libopus --enable-libpulse --enable-runtime-cpudetect --disable-librubberband --disable-sdl2 --disable-libsmbclient --disable-libsnappy --disable-sndio --disable-libsoxr --disable-libspeex --enable-sse --disable-libssh --disable-libtesseract --enable-libtheora --disable-libtwolame --enable-libv4l2 --enable-vaapi --enable-vdpau --disable-libvidstab --enable-libvorbis --disable-libvo-amrwbenc --enable-libvpx --disable-libwavpack --disable-libwebp --enable-libx264 --enable-libx265 --disable-libxcb --enable-libxvid --disable-outdev=xv --disable-libzimg --disable-libzmq --disable-libzvbi --disable-gcrypt --enable-gmp --disable-librtmp --enable-gnutls --disable-openssl --enable-version3 --enable-nonfree --disable-libaom --disable-libsrt
  libavutil      56. 14.100 / 56. 14.100
  libavcodec     58. 18.100 / 58. 18.100
  libavformat    58. 12.100 / 58. 12.100
  libavdevice    58.  3.100 / 58.  3.100
  libavfilter     7. 16.100 /  7. 16.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  1.100 /  5.  1.100
  libswresample   3.  1.100 /  3.  1.100
  libpostproc    55.  1.100 / 55.  1.100
Encoder libx265 [libx265 H.265 / HEVC]:
    General capabilities: delay threads
    Threading capabilities: auto
    Supported pixel formats: yuv420p yuv422p yuv444p gbrp yuv420p10le yuv422p10le yuv444p10le gbrp10le yuv420p12le yuv422p12le yuv444p12le gbrp12le gray gray10le gray12le
libx265 AVOptions:
  -crf               <float>      E..V..... set the x265 crf (from -1 to FLT_MAX) (default -1)
  -forced-idr        <boolean>    E..V..... if forcing keyframes, force them as IDR frames (default false)
  -preset            <string>     E..V..... set the x265 preset
  -tune              <string>     E..V..... set the x265 tune parameter
  -profile           <string>     E..V..... set the x265 profile
  -x265-params       <string>     E..V..... set the x265 configuration using a :-separated list of key=value parameters