It was in the source :} Just disable asm for 32-bit arch if you are building 12- and 10-bit versions .. It will be dog slow (like 8 min for 1 min encode of 720x400 film clip! On 4x 3.9Ghz AMD machine) but it will work in cinelerra-5.1/thirdparty/x265_3.1.2 replace supplied configure with attached configure script, and multilib.sh inside x265_3.1.2/build/linux/ with attached version too. Then remove x265 and ffmpeg build-touch files in cinelerra-5.1/thridparty/build, it will trigger rebuild of both if you will do make in cinelerra-5.1 root dir. then, if everything was ok - cd cinelerra, make clean , cd ../ , make -j 5. resulted file in bin will be 10-bit hevc capable Cinelerra-GG root@slax:/dev/shm/tmp/cinelerra-goodguy-20191101/cinelerra-5.1/bin# ./cin Cinelerra Infinity - built: Nov 2 2019 03:08:05 git://git.cinelerra-gg.org/goodguy/cinelerra.git (c) 2006-2019 Heroine Virtual Ltd. by Adam Williams (c) 2007-2019 cin5 derivative by W.P. Morrow aka goodguy Cinelerra is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. There is absolutely no warranty for Cinelerra. x265 [info]: HEVC encoder version 3.1.2+1-76650bab70f9 x265 [info]: build info [Linux][GCC 5.5.0][32 bit][noasm] 10bit x265 [info]: using cpu capabilities: none! x265 [info]: Main 4:2:2 10 profile, Level-3 (Main tier) x265 [info]: Thread pool created using 4 threads x265 [info]: Slices : 1 x265 [info]: frame threads / pool features : 2 / wpp(7 rows) x265 [warning]: Source height < 720p; disabling lookahead-slices x265 [info]: Coding QT: max CU size, min CU size : 64 / 8 x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra x265 [info]: ME / range / subpel / merge : hex / 57 / 2 / 3 x265 [info]: Keyframe min / max / scenecut / bias: 3 / 30 / 40 / 5.00 x265 [info]: Lookahead / bframes / badapt : 20 / 4 / 2 x265 [info]: b-pyramid / weightp / weightb : 1 / 1 / 0 x265 [info]: References / ref-limit cu / depth : 3 / off / on x265 [info]: AQ: mode / str / qg-size / cu-tree : 2 / 1.0 / 32 / 1 x265 [info]: Rate Control / qCompress : CRF-28.0 / 0.60 x265 [info]: tools: rd=3 psy-rd=2.00 early-skip rskip signhide tmvp b-intra x265 [info]: tools: strong-intra-smoothing deblock sao x265 [info]: frame I: 73, Avg QP:26.28 kb/s: 2612.99 x265 [info]: frame P: 455, Avg QP:28.33 kb/s: 716.62 x265 [info]: frame B: 1383, Avg QP:34.19 kb/s: 139.91 x265 [info]: Weighted P-Frames: Y:1.1% UV:0.0% x265 [info]: consecutive B-frames: 5.1% 10.6% 1.9% 82.0% 0.4% encoded 1911 frames in 449.76s (4.25 fps), 371.69 kb/s, Avg QP:32.49 Render::render_single: Session finished. ** rendered 1911 frames in 449.855 secs, 4.248 fps audio0 pad 16 0 (16) note, for x86_64 you actually can re-enable asm in multilib.sh, I just have only 32-bit Slackware ATM . Note2: you should choose pixel format by hand - yuv422p10le - not just yuv422p10 as h265-10bit.mp4 suggest Mplayer seems to recognize this as 10 bit depth file: mplayer /dev/shm/hevc_10bit.mp4 MPlayer SVN-r38152-5.5.0 (C) 2000-2019 MPlayer Team 224 audio & 466 video codecs Playing /dev/shm/hevc_10bit.mp4. libavformat version 58.33.100 (internal) libavformat file format detected. [mov,mp4,m4a,3gp,3g2,mj2 @ 0x5755e9e0]Protocol name not provided, cannot determine if input is local or a network protocol, buffers and access patterns cannot be configured optimally without knowing the protocol [lavf] stream 0: video (hevc), -vid 0 [lavf] stream 1: audio (aac), -aid 0, -alang rus VIDEO: [HEVC] 720x400 24bpp 25.000 fps 372.5 kbps (45.5 kbyte/s) ========================================================================== Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family libavcodec version 58.59.102 (internal) Selected video codec: [ffhevc] vfm: ffmpeg (FFmpeg HEVC / H.265) ========================================================================== Clip info: major_brand: isom minor_version: 512 compatible_brands: isomiso2mp41 encoder: Lavf58.29.100 Load subtitles in /dev/shm/ ========================================================================== Forced audio codec: mad Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders [aac @ 0x576b67e0]Multiple frames in a packet. AUDIO: 48000 Hz, 2 ch, floatle, 128.5 kbit/4.18% (ratio: 16062->384000) Selected audio codec: [ffaac] afm: ffmpeg (FFmpeg AAC (MPEG-2/MPEG-4 Audio)) ========================================================================== AO: [alsa] 48000Hz 2ch floatle (4 bytes per sample) Starting playback... [aac @ 0x576b67e0]channel element 0.0 is not allocated Could not find matching colorspace - retrying with -vf scale... Opening video filter: [scale] Movie-Aspect is 1.80:1 - prescaling to correct movie aspect. [swscaler @ 0x577f2140]bicubic scaler, from yuv422p10le to yuv420p using MMXEXT VO: [vdpau] 720x400 => 720x400 Planar YV12 A: 61.3 V: 61.3 A-V: -0.023 ct: -0.048 0/ 0 7% 16% 0.6% 0 0 Exiting... (Quit) Happy hacking! PS: x265 [info]: HEVC encoder version 3.1.2+1-76650bab70f9 x265 [info]: build info [Linux][GCC 5.5.0][32 bit] 8bit+10bit+12bit x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX XOP FMA4 FMA3 BMI1 x265 [info]: Main profile, Level-3 (Main tier) x265 [info]: Thread pool created using 4 threads x265 [info]: Slices : 1 x265 [info]: frame threads / pool features : 2 / wpp(7 rows) x265 [warning]: Source height < 720p; disabling lookahead-slices x265 [info]: Coding QT: max CU size, min CU size : 64 / 8 x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra x265 [info]: ME / range / subpel / merge : hex / 57 / 2 / 3 x265 [info]: Keyframe min / max / scenecut / bias: 3 / 30 / 40 / 5.00 x265 [info]: Lookahead / bframes / badapt : 20 / 4 / 2 x265 [info]: b-pyramid / weightp / weightb : 1 / 1 / 0 x265 [info]: References / ref-limit cu / depth : 3 / off / on x265 [info]: AQ: mode / str / qg-size / cu-tree : 2 / 1.0 / 32 / 1 x265 [info]: Rate Control / qCompress : CRF-5.0 / 0.60 x265 [info]: tools: rd=3 psy-rd=2.00 early-skip rskip signhide tmvp b-intra x265 [info]: tools: strong-intra-smoothing deblock sao x265 [info]: frame I: 72, Avg QP:4.03 kb/s: 20900.03 x265 [info]: frame P: 458, Avg QP:5.11 kb/s: 11911.56 x265 [info]: frame B: 1381, Avg QP:10.12 kb/s: 3065.83 x265 [info]: Weighted P-Frames: Y:0.4% UV:0.0% x265 [info]: consecutive B-frames: 4.0% 13.0% 1.7% 81.1% 0.2% encoded 1911 frames in 220.58s (8.66 fps), 5857.77 kb/s, Avg QP:8.69 Render::render_single: Session finished. ** rendered 1911 frames in 220.697 secs, 8.659 fps as you can see 8-bit encoding still fast/asm'ed.