ffmpeg libx264 h264_nvenc 编码参数解析

主要AVOptions

公有AVOptions

-preset

主要用来调节编码速度和质量的平衡，虽然libx264和h264_nvenc都有此参数，但是该参数的可选项却不完全相同：

preset是通过设置一系列编码参数来实现调节编码速度和质量的效果的，
e.g. -preset faster 是做了如下设置 --no-mixed-refs --rc-lookahead 20 --ref 2 --subme 4 --weightp 1

详细信息见文章最后一章的x264 encoding options。

libx264 有10个选项

速度由快到慢，速度越慢，质量越好，压缩比越大；默认是medium。

• ultrafast
• superfast
• veryfast
• faster
• fast
• medium
• slow
• slower
• veryslow
• placebo

h264_nvenc 有11个选项

默认是medium。

• slow
• medium
• fast
• hp
• hq
• bd
• ll
• llhq
• llhp
• lossless
• losslesshp

针对 libx264做过简单的各选项对比测试，结果如下图

-profile

用来设置画质级别， 默认级别为 high：

• Baseline Profile：基本画质。支持I/P 帧，只支持无交错（Progressive）和CAVLC；
• Main profile：主流画质。提供I/P/B 帧，支持无交错（Progressive）和交错（Interlaced）， 也支持CAVLC 和CABAC 的支持；
• High profile：高级画质。在main Profile 的基础上增加了8x8内部预测、自定义量化、 无损视频编码和更多的YUV 格式；

H.264 Baseline profile和Main profile都是针对8位样本数据、4:2:0格式(YUV)的视频序列。在相同配置情况下，High profile（HP）可以比Main profile（MP）降低10%的码率。 根据应用领域的不同，Baseline profile多应用于实时通信领域，Main profile多应用于流媒体领域，High profile则多应用于广电和存储领域。

除了这三项之外，high还衍生出了 high10、 high422、 high444、high444p 等参数。。。。。

该参数覆盖的用户设置项见文章最后一章的x264 encoding options。

-level

-crf -cq

crf可以根据视频的运动和静止动态的进行压缩。

与crf、cq、qp、vbr、cbr相关的解析可以参考：Understanding Rate Control Modes (x264, x265, vpx) 和 CRF Guide (Constant Rate Factor in x264 and x265)

libx264

-crf d Select the quality for constant quality mode (from -1 to FLT_MAX) (default -1)

h264_nvenc

-cq Set target quality level (0 to 51, 0 means automatic) for constant quality mode in VBR rate control (from 0 to 51) (default 0)

-qp

类似于crf,但相同比特率下质量更差，建议使用crf

libx264

Constant quantization parameter rate control method (from -1 to INT_MAX) (default -1)

h264_nvenc

Constant quantization parameter rate control method (from -1 to 51) (default -1)

libx264 专有参数

-tune

为特定类型的源或情况调整设置

主要参数有

• film （ 电影、真人类型）
• animation （动画）
• grain （需要保留大量的grain时用，高比特率编码）
• stillimage （静态图像编码时使用）
• psnr （为提高psnr做了优化的参数）
• ssim （为提高ssim做了优化的参数）
• fastdecode （可以快速解码的参数）
• zerolatency （零延迟，用在需要非常低的延迟的情况下，比如电视电话会议的编码）

详细 help 信息

libx264 AVOptions

查看指令ffmpeg -h encoder=libx264

ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1_1 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gpl --enable-libmp3lame --enable-libopus --enable-libsnappy --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-opencl --enable-videotoolbox
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Encoder libx264 [libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10]:
    General capabilities: delay threads
    Threading capabilities: auto
    Supported pixel formats: yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p nv12 nv16 nv21 yuv420p10le yuv422p10le yuv444p10le nv20le
libx264 AVOptions:
  -preset                 E..V..... Set the encoding preset (cf. x264 --fullhelp) (default "medium")
  -tune                   E..V..... Tune the encoding params (cf. x264 --fullhelp)
  -profile                E..V..... Set profile restrictions (cf. x264 --fullhelp)
  -fastfirstpass         E..V..... Use fast settings when encoding first pass (default true)
  -level                  E..V..... Specify level (as defined by Annex A)
  -passlogfile            E..V..... Filename for 2 pass stats
  -wpredp                 E..V..... Weighted prediction for P-frames
  -a53cc                 E..V..... Use A53 Closed Captions (if available) (default true)
  -x264opts               E..V..... x264 options
  -crf                     E..V..... Select the quality for constant quality mode (from -1 to FLT_MAX) (default -1)
  -crf_max                 E..V..... In CRF mode, prevents VBV from lowering quality beyond this point. (from -1 to FLT_MAX) (default -1)
  -qp                        E..V..... Constant quantization parameter rate control method (from -1 to INT_MAX) (default -1)
  -aq-mode                   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             E..V..... AQ strength. Reduces blocking and blurring in flat and textured areas. (from -1 to FLT_MAX) (default -1)
  -psy                   E..V..... Use psychovisual optimizations. (default auto)
  -psy-rd                 E..V..... Strength of psychovisual optimization, in : format.
  -rc-lookahead              E..V..... Number of frames to look ahead for frametype and ratecontrol (from -1 to INT_MAX) (default -1)
  -weightb               E..V..... Weighted prediction for B-frames. (default auto)
  -weightp                   E..V..... Weighted prediction analysis method. (from -1 to INT_MAX) (default -1)
     none                         E..V.....
     simple                       E..V.....
     smart                        E..V.....
  -ssim                  E..V..... Calculate and print SSIM stats. (default auto)
  -intra-refresh         E..V..... Use Periodic Intra Refresh instead of IDR frames. (default auto)
  -bluray-compat         E..V..... Bluray compatibility workarounds. (default auto)
  -b-bias                    E..V..... Influences how often B-frames are used (from INT_MIN to INT_MAX) (default INT_MIN)
  -b-pyramid                 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            E..V..... One reference per partition, as opposed to one reference per macroblock (default auto)
  -8x8dct                E..V..... High profile 8x8 transform. (default auto)
  -fast-pskip            E..V..... (default auto)
  -aud                   E..V..... Use access unit delimiters. (default auto)
  -mbtree                E..V..... Use macroblock tree ratecontrol. (default auto)
  -deblock                E..V..... Loop filter parameters, in  form.
  -cplxblur                E..V..... Reduce fluctuations in QP (before curve compression) (from -1 to FLT_MAX) (default -1)
  -partitions             E..V..... A comma-separated list of partitions to consider. Possible values: p8x8, p4x4, b8x8, i8x8, i4x4, none, all
  -direct-pred               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            E..V..... Limit the size of each slice in bytes (from -1 to INT_MAX) (default -1)
  -stats                  E..V..... Filename for 2 pass stats
  -nal-hrd                   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            E..V..... AVC-Intra class 50/100/200 (from -1 to 200) (default -1)
  -me_method                 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.....
  -motion-est                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            E..V..... If forcing keyframes, force them as IDR frames. (default false)
  -coder                     E..V..... Coder type (from -1 to 1) (default default)
     default                      E..V.....
     cavlc                        E..V.....
     cabac                        E..V.....
     vlc                          E..V.....
     ac                           E..V.....
  -b_strategy                E..V..... Strategy to choose between I/P/B-frames (from -1 to 2) (default -1)
  -chromaoffset              E..V..... QP difference between chroma and luma (from INT_MIN to INT_MAX) (default -1)
  -sc_threshold              E..V..... Scene change threshold (from INT_MIN to INT_MAX) (default -1)
  -noise_reduction           E..V..... Noise reduction (from INT_MIN to INT_MAX) (default -1)
  -x264-params            E..V..... Override the x264 configuration using a :-separated list of key=value parameters

h264_nvenc AVOptions

查看指令ffmpeg -h encoder=h264_nvenc

ffmpeg version 3.3.8 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-36)
  configuration: --prefix=/root/ffmpeg_build --pkg-config-flags=--static --extra-cflags='-I/root/ffmpeg_build/include -I/usr/local/cuda/include' --extra-ldflags='-L/root/ffmpeg_build/lib -L/usr/local/cuda/lib64' --extra-libs=-lpthread --extra-libs=-lm --bindir=/root/bin --enable-gpl --enable-libfdk_aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --enable-cuda --enable-cuvid --enable-nvenc --enable-libnpp
  libavutil      55. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100
  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100
Encoder h264_nvenc [NVIDIA NVENC H.264 encoder]:
    General capabilities: delay
    Threading capabilities: none
    Supported pixel formats: yuv420p nv12 p010le yuv444p yuv444p16le bgr0 rgb0 cuda
h264_nvenc AVOptions:
  -preset                    E..V.... Set the encoding preset (from 0 to 11) (default medium)
     default                      E..V....
     slow                         E..V.... hq 2 passes
     medium                       E..V.... hq 1 pass
     fast                         E..V.... hp 1 pass
     hp                           E..V....
     hq                           E..V....
     bd                           E..V....
     ll                           E..V.... low latency
     llhq                         E..V.... low latency hq
     llhp                         E..V.... low latency hp
     lossless                     E..V....
     losslesshp                   E..V....
  -profile                   E..V.... Set the encoding profile (from 0 to 3) (default main)
     baseline                     E..V....
     main                         E..V....
     high                         E..V....
     high444p                     E..V....
  -level                     E..V.... Set the encoding level restriction (from 0 to 51) (default auto)
     auto                         E..V....
     1                            E..V....
     1.0                          E..V....
     1b                           E..V....
     1.0b                         E..V....
     1.1                          E..V....
     1.2                          E..V....
     1.3                          E..V....
     2                            E..V....
     2.0                          E..V....
     2.1                          E..V....
     2.2                          E..V....
     3                            E..V....
     3.0                          E..V....
     3.1                          E..V....
     3.2                          E..V....
     4                            E..V....
     4.0                          E..V....
     4.1                          E..V....
     4.2                          E..V....
     5                            E..V....
     5.0                          E..V....
     5.1                          E..V....
  -rc                        E..V.... Override the preset rate-control (from -1 to INT_MAX) (default -1)
     constqp                      E..V.... Constant QP mode
     vbr                          E..V.... Variable bitrate mode
     cbr                          E..V.... Constant bitrate mode
     vbr_minqp                    E..V.... Variable bitrate mode with MinQP
     ll_2pass_quality              E..V.... Multi-pass optimized for image quality (only for low-latency presets)
     ll_2pass_size                E..V.... Multi-pass optimized for constant frame size (only for low-latency presets)
     vbr_2pass                    E..V.... Multi-pass variable bitrate mode
  -rc-lookahead              E..V.... Number of frames to look ahead for rate-control (from -1 to INT_MAX) (default -1)
  -surfaces                  E..V.... Number of concurrent surfaces (from 0 to 64) (default 32)
  -cbr                   E..V.... Use cbr encoding mode (default false)
  -2pass                 E..V.... Use 2pass encoding mode (default auto)
  -gpu                       E..V.... Selects which NVENC capable GPU to use. First GPU is 0, second is 1, and so on. (from -2 to INT_MAX) (default any)
     any                          E..V.... Pick the first device available
     list                         E..V.... List the available devices
  -delay                     E..V.... Delay frame output by the given amount of frames (from 0 to INT_MAX) (default INT_MAX)
  -no-scenecut           E..V.... When lookahead is enabled, set this to 1 to disable adaptive I-frame insertion at scene cuts (default false)
  -forced-idr            E..V.... If forcing keyframes, force them as IDR frames. (default false)
  -b_adapt               E..V.... When lookahead is enabled, set this to 0 to disable adaptive B-frame decision (default true)
  -spatial-aq            E..V.... set to 1 to enable Spatial AQ (default false)
  -temporal-aq           E..V.... set to 1 to enable Temporal AQ (default false)
  -zerolatency           E..V.... Set 1 to indicate zero latency operation (no reordering delay) (default false)
  -nonref_p              E..V.... Set this to 1 to enable automatic insertion of non-reference P-frames (default false)
  -strict_gop            E..V.... Set 1 to minimize GOP-to-GOP rate fluctuations (default false)
  -aq-strength               E..V.... When Spatial AQ is enabled, this field is used to specify AQ strength. AQ strength scale is from 1 (low) - 15 (aggressive) (from 1 to 15) (default 8)
  -cq                        E..V.... Set target quality level (0 to 51, 0 means automatic) for constant quality mode in VBR rate control (from 0 to 51) (default 0)
  -aud                   E..V.... Use access unit delimiters (default false)
  -bluray-compat         E..V.... Bluray compatibility workarounds (default false)
  -init_qpP                  E..V.... Initial QP value for P frame (from -1 to 51) (default -1)
  -init_qpB                  E..V.... Initial QP value for B frame (from -1 to 51) (default -1)
  -init_qpI                  E..V.... Initial QP value for I frame (from -1 to 51) (default -1)
  -qp                        E..V.... Constant quantization parameter rate control method (from -1 to 51) (default -1)

x264 encoding options

查看指令x264 --fullhelp

x264 core:155 r2917 0a84d98
Syntax: x264 [options] -o outfile infile

Infile can be raw (in which case resolution is required),
  or YUV4MPEG (*.y4m),
  or Avisynth if compiled with support (yes).
  or libav* formats if compiled with lavf support (no) or ffms support (no).
Outfile type is selected by filename:
 .264 -> Raw bytestream
 .mkv -> Matroska
 .flv -> Flash Video
 .mp4 -> MP4 if compiled with GPAC or L-SMASH support (no)
Output bit depth: 8/10
.
Options:

  -h, --help                  List basic options
      --longhelp              List more options
      --fullhelp              List all options

Example usage:

      Constant quality mode:
            x264 --crf 24 -o 
 

      Two-pass with a bitrate of 1000kbps:
            x264 --pass 1 --bitrate 1000 -o 
 
            x264 --pass 2 --bitrate 1000 -o 
 

      Lossless:
            x264 --qp 0 -o 
 

      Maximum PSNR at the cost of speed and visual quality:
            x264 --preset placebo --tune psnr -o 
 

      Constant bitrate at 1000kbps with a 2 second-buffer:
            x264 --vbv-bufsize 2000 --bitrate 1000 -o 
 

Presets:

      --profile       Force the limits of an H.264 profile
                                  Overrides all settings.
                                  - baseline:
                                    --no-8x8dct --bframes 0 --no-cabac
                                    --cqm flat --weightp 0
                                    No interlaced.
                                    No lossless.
                                  - main:
                                    --no-8x8dct --cqm flat
                                    No lossless.
                                  - high:
                                    No lossless.
                                  - high10:
                                    No lossless.
                                    Support for bit depth 8-10.
                                  - high422:
                                    No lossless.
                                    Support for bit depth 8-10.
                                    Support for 4:2:0/4:2:2 chroma subsampling.
                                  - high444:
                                    Support for bit depth 8-10.
                                    Support for 4:2:0/4:2:2/4:4:4 chroma subsampling.
      --preset        Use a preset to select encoding settings [medium]
                                  Overridden by user settings.
                                  - ultrafast:
                                    --no-8x8dct --aq-mode 0 --b-adapt 0
                                    --bframes 0 --no-cabac --no-deblock
                                    --no-mbtree --me dia --no-mixed-refs
                                    --partitions none --rc-lookahead 0 --ref 1
                                    --scenecut 0 --subme 0 --trellis 0
                                    --no-weightb --weightp 0
                                  - superfast:
                                    --no-mbtree --me dia --no-mixed-refs
                                    --partitions i8x8,i4x4 --rc-lookahead 0
                                    --ref 1 --subme 1 --trellis 0 --weightp 1
                                  - veryfast:
                                    --no-mixed-refs --rc-lookahead 10
                                    --ref 1 --subme 2 --trellis 0 --weightp 1
                                  - faster:
                                    --no-mixed-refs --rc-lookahead 20
                                    --ref 2 --subme 4 --weightp 1
                                  - fast:
                                    --rc-lookahead 30 --ref 2 --subme 6
                                    --weightp 1
                                  - medium:
                                    Default settings apply.
                                  - slow:
                                    --direct auto --rc-lookahead 50 --ref 5
                                    --subme 8 --trellis 2
                                  - slower:
                                    --b-adapt 2 --direct auto --me umh
                                    --partitions all --rc-lookahead 60
                                    --ref 8 --subme 9 --trellis 2
                                  - veryslow:
                                    --b-adapt 2 --bframes 8 --direct auto
                                    --me umh --merange 24 --partitions all
                                    --ref 16 --subme 10 --trellis 2
                                    --rc-lookahead 60
                                  - placebo:
                                    --bframes 16 --b-adapt 2 --direct auto
                                    --slow-firstpass --no-fast-pskip
                                    --me tesa --merange 24 --partitions all
                                    --rc-lookahead 60 --ref 16 --subme 11
                                    --trellis 2
      --tune          Tune the settings for a particular type of source
                              or situation
                                  Overridden by user settings.
                                  Multiple tunings are separated by commas.
                                  Only one psy tuning can be used at a time.
                                  - film (psy tuning):
                                    --deblock -1:-1 --psy-rd :0.15
                                  - animation (psy tuning):
                                    --bframes {+2} --deblock 1:1
                                    --psy-rd 0.4: --aq-strength 0.6
                                    --ref {Double if >1 else 1}
                                  - grain (psy tuning):
                                    --aq-strength 0.5 --no-dct-decimate
                                    --deadzone-inter 6 --deadzone-intra 6
                                    --deblock -2:-2 --ipratio 1.1
                                    --pbratio 1.1 --psy-rd :0.25
                                    --qcomp 0.8
                                  - stillimage (psy tuning):
                                    --aq-strength 1.2 --deblock -3:-3
                                    --psy-rd 2.0:0.7
                                  - psnr (psy tuning):
                                    --aq-mode 0 --no-psy
                                  - ssim (psy tuning):
                                    --aq-mode 2 --no-psy
                                  - fastdecode:
                                    --no-cabac --no-deblock --no-weightb
                                    --weightp 0
                                  - zerolatency:
                                    --bframes 0 --force-cfr --no-mbtree
                                    --sync-lookahead 0 --sliced-threads
                                    --rc-lookahead 0
      --slow-firstpass        Don't force these faster settings with --pass 1:
                                  --no-8x8dct --me dia --partitions none
                                  --ref 1 --subme {2 if >2 else unchanged}
                                  --trellis 0 --fast-pskip

Frame-type options:

  -I, --keyint  Maximum GOP size [250]
  -i, --min-keyint   Minimum GOP size [auto]
      --no-scenecut           Disable adaptive I-frame decision
      --scenecut     How aggressively to insert extra I-frames [40]
      --intra-refresh         Use Periodic Intra Refresh instead of IDR frames
  -b, --bframes      Number of B-frames between I and P [3]
      --b-adapt      Adaptive B-frame decision method [1]
                                  Higher values may lower threading efficiency.
                                  - 0: Disabled
                                  - 1: Fast
                                  - 2: Optimal (slow with high --bframes)
      --b-bias       Influences how often B-frames are used [0]
      --b-pyramid     Keep some B-frames as references [normal]
                                  - none: Disabled
                                  - strict: Strictly hierarchical pyramid
                                  - normal: Non-strict (not Blu-ray compatible)
      --open-gop              Use recovery points to close GOPs
                              Only available with b-frames
      --no-cabac              Disable CABAC
  -r, --ref          Number of reference frames [3]
      --no-deblock            Disable loop filter
  -f, --deblock   Loop filter parameters [0:0]
      --slices       Number of slices per frame; forces rectangular
                              slices and is overridden by other slicing options
      --slices-max   Absolute maximum slices per frame; overrides
                              slice-max-size/slice-max-mbs when necessary
      --slice-max-size  Limit the size of each slice in bytes
      --slice-max-mbs  Limit the size of each slice in macroblocks (max)
      --slice-min-mbs  Limit the size of each slice in macroblocks (min)
      --tff                   Enable interlaced mode (top field first)
      --bff                   Enable interlaced mode (bottom field first)
      --constrained-intra     Enable constrained intra prediction.
      --pulldown      Use soft pulldown to change frame rate
                                  - none, 22, 32, 64, double, triple, euro (requires cfr input)
      --fake-interlaced       Flag stream as interlaced but encode progressive.
                              Makes it possible to encode 25p and 30p Blu-Ray
                              streams. Ignored in interlaced mode.
      --frame-packing  For stereoscopic videos define frame arrangement
                                  - 0: checkerboard - pixels are alternatively from L and R
                                  - 1: column alternation - L and R are interlaced by column
                                  - 2: row alternation - L and R are interlaced by row
                                  - 3: side by side - L is on the left, R on the right
                                  - 4: top bottom - L is on top, R on bottom
                                  - 5: frame alternation - one view per frame
                                  - 6: mono - 2D frame without any frame packing
                                  - 7: tile format - L is on top-left, R split across

Ratecontrol:

  -q, --qp           Force constant QP (0-81, 0=lossless)
  -B, --bitrate      Set bitrate (kbit/s)
      --crf            Quality-based VBR (-12-51) [23.0]
      --rc-lookahead  Number of frames for frametype lookahead [40]
      --vbv-maxrate  Max local bitrate (kbit/s) [0]
      --vbv-bufsize  Set size of the VBV buffer (kbit) [0]
      --vbv-init       Initial VBV buffer occupancy [0.9]
      --crf-max        With CRF+VBV, limit RF to this value
                                  May cause VBV underflows!
      --qpmin        Set min QP [0]
      --qpmax        Set max QP [81]
      --qpstep       Set max QP step [4]
      --ratetol        Tolerance of ABR ratecontrol and VBV [1.0]
      --ipratio        QP factor between I and P [1.40]
      --pbratio        QP factor between P and B [1.30]
      --chroma-qp-offset   QP difference between chroma and luma [0]
      --aq-mode      AQ method [1]
                                  - 0: Disabled
                                  - 1: Variance AQ (complexity mask)
                                  - 2: Auto-variance AQ
                                  - 3: Auto-variance AQ with bias to dark scenes
      --aq-strength    Reduces blocking and blurring in flat and
                              textured areas. [1.0]

  -p, --pass         Enable multipass ratecontrol
                                  - 1: First pass, creates stats file
                                  - 2: Last pass, does not overwrite stats file
                                  - 3: Nth pass, overwrites stats file
      --stats         Filename for 2 pass stats ["x264_2pass.log"]
      --no-mbtree             Disable mb-tree ratecontrol.
      --qcomp          QP curve compression [0.60]
      --cplxblur       Reduce fluctuations in QP (before curve compression) [20.0]
      --qblur          Reduce fluctuations in QP (after curve compression) [0.5]
      --zones //...  Tweak the bitrate of regions of the video
                              Each zone is of the form
                                  ,,
                                  where  is either
                                      q= (force QP)
                                  or  b= (bitrate multiplier)
      --qpfile        Force frametypes and QPs for some or all frames
                              Format of each line: framenumber frametype QP
                              QP is optional (none lets x264 choose). Frametypes: I,i,K,P,B,b.
                                  K= depending on open-gop setting
                              QPs are restricted by qpmin/qpmax.

Analysis:

  -A, --partitions    Partitions to consider ["p8x8,b8x8,i8x8,i4x4"]
                                  - p8x8, p4x4, b8x8, i8x8, i4x4
                                  - none, all
                                  (p4x4 requires p8x8. i8x8 requires --8x8dct.)
      --direct        Direct MV prediction mode ["spatial"]
                                  - none, spatial, temporal, auto
      --no-weightb            Disable weighted prediction for B-frames
      --weightp      Weighted prediction for P-frames [2]
                                  - 0: Disabled
                                  - 1: Weighted refs
                                  - 2: Weighted refs + Duplicates
      --me            Integer pixel motion estimation method ["hex"]
                                  - dia: diamond search, radius 1 (fast)
                                  - hex: hexagonal search, radius 2
                                  - umh: uneven multi-hexagon search
                                  - esa: exhaustive search
                                  - tesa: hadamard exhaustive search (slow)
      --merange      Maximum motion vector search range [16]
      --mvrange      Maximum motion vector length [-1 (auto)]
      --mvrange-thread   Minimum buffer between threads [-1 (auto)]
  -m, --subme        Subpixel motion estimation and mode decision [7]
                                  - 0: fullpel only (not recommended)
                                  - 1: SAD mode decision, one qpel iteration
                                  - 2: SATD mode decision
                                  - 3-5: Progressively more qpel
                                  - 6: RD mode decision for I/P-frames
                                  - 7: RD mode decision for all frames
                                  - 8: RD refinement for I/P-frames
                                  - 9: RD refinement for all frames
                                  - 10: QP-RD - requires trellis=2, aq-mode>0
                                  - 11: Full RD: disable all early terminations
      --psy-rd   Strength of psychovisual optimization ["1.0:0.0"]
                                  #1: RD (requires subme>=6)
                                  #2: Trellis (requires trellis, experimental)
      --no-psy                Disable all visual optimizations that worsen
                              both PSNR and SSIM.
      --no-mixed-refs         Don't decide references on a per partition basis
      --no-chroma-me          Ignore chroma in motion estimation
      --no-8x8dct             Disable adaptive spatial transform size
  -t, --trellis      Trellis RD quantization. [1]
                                  - 0: disabled
                                  - 1: enabled only on the final encode of a MB
                                  - 2: enabled on all mode decisions
      --no-fast-pskip         Disables early SKIP detection on P-frames
      --no-dct-decimate       Disables coefficient thresholding on P-frames
      --nr           Noise reduction [0]

      --deadzone-inter   Set the size of the inter luma quantization deadzone [21]
      --deadzone-intra   Set the size of the intra luma quantization deadzone [11]
                                  Deadzones should be in the range 0 - 32.
      --cqm           Preset quant matrices ["flat"]
                                  - jvt, flat
      --cqmfile       Read custom quant matrices from a JM-compatible file
                                  Overrides any other --cqm* options.
      --cqm4            Set all 4x4 quant matrices
                                  Takes a comma-separated list of 16 integers.
      --cqm8            Set all 8x8 quant matrices
                                  Takes a comma-separated list of 64 integers.
      --cqm4i, --cqm4p, --cqm8i, --cqm8p 
                              Set both luma and chroma quant matrices
      --cqm4iy, --cqm4ic, --cqm4py, --cqm4pc 
                              Set individual quant matrices

Video Usability Info (Annex E):
The VUI settings are not used by the encoder but are merely suggestions to
the playback equipment. See doc/vui.txt for details. Use at your own risk.

      --overscan      Specify crop overscan setting ["undef"]
                                  - undef, show, crop
      --videoformat   Specify video format ["undef"]
                                  - component, pal, ntsc, secam, mac, undef
      --range         Specify color range ["auto"]
                                  - auto, tv, pc
      --colorprim     Specify color primaries ["undef"]
                                  - undef, bt709, bt470m, bt470bg, smpte170m,
                                    smpte240m, film, bt2020, smpte428,
                                    smpte431, smpte432
      --transfer      Specify transfer characteristics ["undef"]
                                  - undef, bt709, bt470m, bt470bg, smpte170m,
                                    smpte240m, linear, log100, log316,
                                    iec61966-2-4, bt1361e, iec61966-2-1,
                                    bt2020-10, bt2020-12, smpte2084, smpte428,
                                    arib-std-b67
      --colormatrix   Specify color matrix setting ["???"]
                                  - undef, bt709, fcc, bt470bg, smpte170m,
                                    smpte240m, GBR, YCgCo, bt2020nc, bt2020c,
                                    smpte2085, chroma-derived-nc,
                                    chroma-derived-c, ICtCp
      --chromaloc    Specify chroma sample location (0 to 5) [0]
      --alternative-transfer  Specify an alternative transfer
                              characteristics ["undef"]
                                  - same values as --transfer
      --nal-hrd       Signal HRD information (requires vbv-bufsize)
                                  - none, vbr, cbr (cbr not allowed in .mp4)
      --filler                Force hard-CBR and generate filler (implied by
                              --nal-hrd cbr)
      --pic-struct            Force pic_struct in Picture Timing SEI
      --crop-rect     Add 'left,top,right,bottom' to the bitstream-level
                              cropping rectangle

Input/Output:

  -o, --output        Specify output file
      --muxer         Specify output container format ["auto"]
                                  - auto, raw, mkv, flv
      --demuxer       Specify input container format ["auto"]
                                  - auto, raw, y4m, avs
      --input-fmt     Specify input file format (requires lavf support)
      --input-csp     Specify input colorspace format for raw input
                              - valid csps for `raw' demuxer:
                                i420, yv12, nv12, nv21, i422, yv16, nv16, yuyv,
                                uyvy, i444, yv24, bgr, bgra, rgb
      --output-csp    Specify output colorspace ["i420"]
                                  - i420, i422, i444, rgb
      --input-depth  Specify input bit depth for raw input
      --output-depth  Specify output bit depth
      --input-range   Specify input color range ["auto"]
                                  - auto, tv, pc
      --input-res    Specify input resolution (width x height)
      --index         Filename for input index file
      --sar width:height      Specify Sample Aspect Ratio
      --fps   Specify framerate
      --seek         First frame to encode
      --frames       Maximum number of frames to encode
      --level         Specify level (as defined by Annex A)
      --bluray-compat         Enable compatibility hacks for Blu-ray support
      --avcintra-class  Use compatibility hacks for AVC-Intra class
                                  - 50, 100, 200
      --stitchable            Don't optimize headers based on video content
                              Ensures ability to recombine a segmented encode

  -v, --verbose               Print stats for each frame
      --no-progress           Don't show the progress indicator while encoding
      --quiet                 Quiet Mode
      --log-level     Specify the maximum level of logging ["info"]
                                  - none, error, warning, info, debug
      --psnr                  Enable PSNR computation
      --ssim                  Enable SSIM computation
      --threads      Force a specific number of threads
      --lookahead-threads  Force a specific number of lookahead threads
      --sliced-threads        Low-latency but lower-efficiency threading
      --thread-input          Run Avisynth in its own thread
      --sync-lookahead  Number of buffer frames for threaded lookahead
      --non-deterministic     Slightly improve quality of SMP, at the cost of repeatability
      --cpu-independent       Ensure exact reproducibility across different cpus,
                                  as opposed to letting them select different algorithms
      --asm          Override CPU detection
      --no-asm                Disable all CPU optimizations
      --opencl                Enable use of OpenCL
      --opencl-clbin  Specify path of compiled OpenCL kernel cache
      --opencl-device  Specify OpenCL device ordinal
      --dump-yuv      Save reconstructed frames
      --sps-id       Set SPS and PPS id numbers [0]
      --aud                   Use access unit delimiters
      --force-cfr             Force constant framerate timestamp generation
      --tcfile-in     Force timestamp generation with timecode file
      --tcfile-out    Output timecode v2 file from input timestamps
      --timebase     Specify timebase numerator and denominator
                     Specify timebase numerator for input timecode file
                              or specify timebase denominator for other input
      --dts-compress          Eliminate initial delay with container DTS hack

Filtering:

      --vf, --video-filter //... Apply video filtering to the input file

      Filter options may be specified in := format.

      Available filters:
      crop:left,top,right,bottom
            removes pixels from the edges of the frame
      select_every:step,offset1[,...]
            apply a selection pattern to input frames
            step: the number of frames in the pattern
            offsets: the offset into the step to select a frame
            see: http://avisynth.nl/index.php/Select#SelectEvery