1、简述
使用FFmpeg对视频编码时，编码器格式AVCodecContext—>pix_fmt(类型 enum AVPixelFormat)不是什么格式都支持的。首先x264只支持YUV格式，不支持RGB格式。
2、像素格式列表
在FFmpeg（版本4.1）中编码h.264时，支持的像素格式pix_fmt列表如下：
AV_PIX_FMT_YUV420P、
AV_PIX_FMT_YUVJ420P、
AV_PIX_FMT_YUV422P、
AV_PIX_FMT_YUVJ422P、
AV_PIX_FMT_YUV444P、
AV_PIX_FMT_YUVJ444P、
AV_PIX_FMT_NV12、
AV_PIX_FMT_NV16、
AV_PIX_FMT_NV21
3、查看方法
执行命令：
ffmpeg -h encoder=libx264
在打印信息中可以看到支持的像素格式：
Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p nv12 nv16 nv21
4、完整打印信息如下
$ ffmpeg -h encoder=libx264
ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
Encoder libx264 [libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10]:
Threading capabilities: no
Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p nv12 nv16 nv21
libx264 AVOptions:
-preset <string> E..V.... Set the encoding preset (cf. x264 --fullhelp) (default "medium")
-tune <string> E..V.... Tune the encoding params (cf. x264 --fullhelp)
-profile <string> E..V.... Set profile restrictions (cf. x264 --fullhelp)
-fastfirstpass <int> E..V.... Use fast settings when encoding first pass (from 0 to 1) (default 1)
-level <string> E..V.... Specify level (as defined by Annex A)
-passlogfile <string> E..V.... Filename for 2 pass stats
-wpredp <string> E..V.... Weighted prediction for P-frames
-x264opts <string> E..V.... x264 options
-crf <float> E..V.... Select the quality for constant quality mode (from -1 to FLT_MAX) (default -1)
-crf_max <float> E..V.... In CRF mode, prevents VBV from lowering quality beyond this point. (from -1 to FLT_MAX) (default -1)
-qp <int> E..V.... Constant quantization parameter rate control method (from -1 to INT_MAX) (default -1)
-aq-mode <int> E..V.... AQ method (from -1 to INT_MAX) (default -1)
none E..V....
variance E..V.... Variance AQ (complexity mask)
autovariance E..V.... Auto-variance AQ
autovariance-biased E..V.... Auto-variance AQ with bias to dark scenes
-aq-strength <float> E..V.... AQ strength. Reduces blocking and blurring in flat and textured areas. (from -1 to FLT_MAX) (default -1)
-psy <int> E..V.... Use psychovisual optimizations. (from -1 to 1) (default -1)
-psy-rd <string> E..V.... Strength of psychovisual optimization, in <psy-rd>:<psy-trellis> format.
-rc-lookahead <int> E..V.... Number of frames to look ahead for frametype and ratecontrol (from -1 to INT_MAX) (default -1)
-weightb <int> E..V.... Weighted prediction for B-frames. (from -1 to 1) (default -1)
-weightp <int> E..V.... Weighted prediction analysis method. (from -1 to INT_MAX) (default -1)
none E..V....
simple E..V....
smart E..V....
-ssim <int> E..V.... Calculate and print SSIM stats. (from -1 to 1) (default -1)
-intra-refresh <int> E..V.... Use Periodic Intra Refresh instead of IDR frames. (from -1 to 1) (default -1)
-bluray-compat <int> E..V.... Bluray compatibility workarounds. (from -1 to 1) (default -1)
-b-bias <int> E..V.... Influences how often B-frames are used (from INT_MIN to INT_MAX) (default INT_MIN)
-b-pyramid <int> E..V.... Keep some B-frames as references. (from -1 to INT_MAX) (default -1)
none E..V....
strict E..V.... Strictly hierarchical pyramid
normal E..V.... Non-strict (not Blu-ray compatible)
-mixed-refs <int> E..V.... One reference per partition, as opposed to one reference per macroblock (from -1 to 1) (default -1)
-8x8dct <int> E..V.... High profile 8x8 transform. (from -1 to 1) (default -1)
-fast-pskip <int> E..V.... (from -1 to 1) (default -1)
-aud <int> E..V.... Use access unit delimiters. (from -1 to 1) (default -1)
-mbtree <int> E..V.... Use macroblock tree ratecontrol. (from -1 to 1) (default -1)
-deblock <string> E..V.... Loop filter parameters, in <alpha:beta> form.
-cplxblur <float> E..V.... Reduce fluctuations in QP (before curve compression) (from -1 to FLT_MAX) (default -1)
-partitions <string> E..V.... A comma-separated list of partitions to consider. Possible values: p8x8, p4x4, b8x8, i8x8, i4x4, none, all
-direct-pred <int> E..V.... Direct MV prediction mode (from -1 to INT_MAX) (default -1)
none E..V....
spatial E..V....
temporal E..V....
auto E..V....
-slice-max-size <int> E..V.... Limit the size of each slice in bytes (from -1 to INT_MAX) (default -1)
-stats <string> E..V.... Filename for 2 pass stats
-nal-hrd <int> E..V.... Signal HRD information (requires vbv-bufsize; cbr not allowed in .mp4) (from -1 to INT_MAX) (default -1)
none E..V....
vbr E..V....
cbr E..V....
-avcintra-class <int> E..V.... AVC-Intra class 50/100/200 (from -1 to 200) (default -1)
-motion-est <int> E..V.... Set motion estimation method (from -1 to 4) (default -1)
dia E..V....
hex E..V....
umh E..V....
esa E..V....
tesa E..V....
-forced-idr <int> E..V.... If forcing keyframes, force them as IDR frames. (from -1 to 1) (default -1)
-x264-params <string> E..V.... Override the x264 configuration using a :-separated list of key=value parameters
