我错过了什么？ 我使用ffmpeg libx265传递-pix_fmt灰色编码旧的黑白电影剪辑。输出在vlc和mplayer（linux）中都无法播放，所以我想我错过了一些东西......
编码：
ffmpeg -i clip.mkv \
-c:v libx265 -preset slow -x265-params "crf=24" -pix_fmt gray \
-c:a libopus -b:a 64k \
-c:s copy \
out.mkv
vlc错误：
[00007f8a3ddfe328] blend blend error: no matching alpha blending routine (chroma: RGBA -> GREY)
[00007f8a3ddfe328] core blend error: blending RGBA to GREY failed
... repeated ...
mplayer错误：
Unexpected decoder output format Planar Y800
... repeated ...
ffmpeg编码输出：
ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.9.4 (Gentoo 4.9.4 p1.0, pie-0.6.4)
configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --docdir=/usr/share/doc/ffmpeg-3.2.4/html --mandir=/usr/share/man --enable-shared --cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++ --ar=x86_64-pc-linux-gnu-ar --optflags='-march=native -O2 -pipe' --disable-static --enable-avfilter --enable-avresample --disable-stripping --enable-nonfree --enable-version3 --disable-indev=oss --disable-indev=jack --disable-outdev=oss --enable-version3 --enable-bzlib --disable-runtime-cpudetect --disable-debug --disable-gcrypt --disable-gnutls --disable-gmp --enable-gpl --enable-hardcoded-tables --enable-iconv --enable-lzma --enable-network --enable-openssl --enable-postproc --disable-libsmbclient --enable-ffplay --enable-sdl2 --enable-vaapi --enable-vdpau --enable-xlib --enable-libxcb --enable-libxcb-shm --enable-libxcb-xfixes --enable-zlib --enable-libcdio --disable-libiec61883 --disable-libdc1394 --disable-libcaca --enable-openal --enable-opengl --enable-libv4l2 --disable-libpulse --enable-libopencore-amrwb --enable-libopencore-amrnb --disable-libfdk-aac --enable-libopenjpeg --enable-libbluray --enable-libcelt --disable-libgme --disable-libgsm --disable-mmal --enable-libmodplug --enable-libopus --disable-libilbc --disable-librtmp --enable-libssh --enable-libschroedinger --enable-libspeex --enable-libvorbis --enable-libvpx --disable-libzvbi --disable-libbs2b --disable-chromaprint --disable-libebur128 --disable-libflite --disable-frei0r --disable-libfribidi --enable-fontconfig --disable-ladspa --disable-libass --enable-libfreetype --disable-librubberband --disable-libzimg --enable-libsoxr --enable-pthreads --enable-libvo-amrwbenc --enable-libmp3lame --disable-libkvazaar --disable-nvenc --disable-libopenh264 --enable-libsnappy --enable-libtheora --enable-libtwolame --enable-libwavpack --disable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --disable-amd3dnow --disable-amd3dnowext --disable-fma4 --disable-xop --cpu=host --disable-doc --disable-htmlpages --enable-manpages
libavutil 55. 34.101 / 55. 34.101
libavcodec 57. 64.101 / 57. 64.101
libavformat 57. 56.101 / 57. 56.101
libavdevice 57. 1.100 / 57. 1.100
libavfilter 6. 65.100 / 6. 65.100
libavresample 3. 1. 0 / 3. 1. 0
libswscale 4. 2.100 / 4. 2.100
libswresample 2. 3.100 / 2. 3.100
libpostproc 54. 1.100 / 54. 1.100
x265 [info]: HEVC encoder version 2.2
x265 [info]: build info [Linux][GCC 4.9.4][64 bit] 8bit+10bit+12bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX AVX2 FMA3 LZCNT BMI2
x265 [info]: Unknown profile, Level-3.1 (Main tier)
x265 [warning]: No thread pool allocated, --wpp disabled
x265 [warning]: No thread pool allocated, --lookahead-slices disabled
x265 [info]: Slices : 1
x265 [info]: frame threads / pool features : 3 / none
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 : star / 57 / 3 / 3
x265 [info]: Keyframe min / max / scenecut / bias: 23 / 250 / 40 / 5.00
x265 [info]: Lookahead / bframes / badapt : 25 / 4 / 2
x265 [info]: b-pyramid / weightp / weightb : 1 / 1 / 0
x265 [info]: References / ref-limit cu / depth : 4 / on / on
x265 [info]: AQ: mode / str / qg-size / cu-tree : 1 / 1.0 / 32 / 1
x265 [info]: Rate Control / qCompress : CRF-24.0 / 0.60
x265 [info]: tools: rect limit-modes rd=4 psy-rd=2.00 rdoq=2 psy-rdoq=1.00
x265 [info]: tools: rskip signhide tmvp strong-intra-smoothing deblock sao
Output #0, matroska, to 'out.mkv':
Metadata:
encoder : Lavf57.56.101
Metadata:
Stream #0:0(eng): Video: hevc (libx265), gray, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 23.98 fps, 1k tbn, 23.98 tbc (default)
Metadata:
encoder : Lavc57.64.101 libx265
Stream #0:1(eng): Audio: opus (libopus) ([255][255][255][255] / 0xFFFFFFFF), 48000 Hz, stereo, flt, 64 kb/s (default)
Metadata:
encoder : Lavc57.64.101 libopus
Stream #0:2(eng): Subtitle: subrip (default)
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> hevc (libx265))
Stream #0:1 -> #0:1 (eac3 (native) -> opus (libopus))
Stream #0:3 -> #0:2 (copy)
Press [q] to stop, [?] for help
frame= 1439 fps=7.0 q=-0.0 Lsize= 5356kB time=00:01:00.01 bitrate= 731.1kbits/s speed=0.294x
video:4940kB audio:382kB subtitle:1kB other streams:0kB global headers:2kB muxing overhead: 0.629434%
x265 [info]: frame I: 9, Avg QP:22.27 kb/s: 6064.82
x265 [info]: frame P: 340, Avg QP:23.62 kb/s: 1950.21
x265 [info]: frame B: 1090, Avg QP:29.65 kb/s: 230.75
x265 [info]: Weighted P-Frames: Y:0.9% UV:0.0%
x265 [info]: consecutive B-frames: 2.9% 0.3% 1.4% 72.5% 22.9%