ERROR: libx265 version must be >= 17. If you think configure made a mistake, make sure you are using the latest version from Git. If the latest version fails, report the problem to the ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net. Include the log file "config.log" produced by configure as this will help solve the problem. ERROR: libx265 version must be >= 17.
*x265-1.2 (27 Jul 2014) 27 Jul 2014; Samuli Suominen <ssuominen@gentoo.org> +x265-1.2.ebuild, x265-9999.ebuild: Version bump; update SLOT to 0/25 based on new SONAME
+ 27 Jul 2014; Samuli Suominen <ssuominen@gentoo.org> ffmpeg-2.3.ebuild, + ffmpeg-9999.ebuild: + Update media-libs/x265 dependency from 1.0 to 1.2 wrt #518320 by "darkbasic"
From 1.2: $ grep X265_BUILD /usr/include/x265_config.h /* Incremented each time public API is changed, X265_BUILD is used as #define X265_BUILD 25