FFmpeg命令行工具-实用命令

参考

[1] ffmpeg.org/ffmpeg-all

1. help命令使用

首先我们要学会使用ffmpeg工具提供的最最基本的一个命令：ffmpeg -help。

有了他我们就可以更加愉快地学习使用ffmpeg的各种功能了。

执行ffmpeg -help后，在终端会打印下面的帮助信息：

ffmpeg version 3.4.2-1~16.04.york0 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.6) 20160609
  configuration: --prefix=/usr --extra-version='1~16.04.york0' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --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-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --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-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

Getting help:
    -h      -- print basic options
    -h long -- print more options
    -h full -- print all options (including all format and codec specific options, very long)
    -h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter
    See man ffmpeg for detailed description of the options.

Print help / information / capabilities:
-L                  show license
-h topic            show help
-? topic            show help
-help topic         show help
--help topic        show help
-version            show version
-buildconf          show build configuration
-formats            show available formats
-muxers             show available muxers
-demuxers           show available demuxers
-devices            show available devices
-codecs             show available codecs
-decoders           show available decoders
-encoders           show available encoders
-bsfs               show available bit stream filters
-protocols          show available protocols
-filters            show available filters
-pix_fmts           show available pixel formats
-layouts            show standard channel layouts
-sample_fmts        show available audio sample formats
-colors             show available color names
-sources device     list sources of the input device
-sinks device       list sinks of the output device
-hwaccels           show available HW acceleration methods

Global options (affect whole program instead of just one file:
-loglevel loglevel  set logging level
-v loglevel         set logging level
-report             generate a report
-max_alloc bytes    set maximum size of a single allocated block
-y                  overwrite output files
-n                  never overwrite output files
-ignore_unknown     Ignore unknown stream types
-filter_threads     number of non-complex filter threads
-filter_complex_threads  number of threads for -filter_complex
-stats              print progress report during encoding
-max_error_rate ratio of errors (0.0: no errors, 1.0: 100% error  maximum error rate
-bits_per_raw_sample number  set the number of bits per raw sample
-vol volume         change audio volume (256=normal)

Per-file main options:
-f fmt              force format
-c codec            codec name
-codec codec        codec name
-pre preset         preset name
-map_metadata outfile[,metadata]:infile[,metadata]  set metadata information of outfile from infile
-t duration         record or transcode "duration" seconds of audio/video
-to time_stop       record or transcode stop time
-fs limit_size      set the limit file size in bytes
-ss time_off        set the start time offset
-sseof time_off     set the start time offset relative to EOF
-seek_timestamp     enable/disable seeking by timestamp with -ss
-timestamp time     set the recording timestamp ('now' to set the current time)
-metadata string=string  add metadata
-program title=string:st=number...  add program with specified streams
-target type        specify target file type ("vcd", "svcd", "dvd", "dv" or "dv50" with optional prefixes "pal-", "ntsc-" or "film-")
-apad               audio pad
-frames number      set the number of frames to output
-filter filter_graph  set stream filtergraph
-filter_script filename  read stream filtergraph description from a file
-reinit_filter      reinit filtergraph on input parameter changes
-discard            discard
-disposition        disposition

Video options:
-vframes number     set the number of video frames to output
-r rate             set frame rate (Hz value, fraction or abbreviation)
-s size             set frame size (WxH or abbreviation)
-aspect aspect      set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
-bits_per_raw_sample number  set the number of bits per raw sample
-vn                 disable video
-vcodec codec       force video codec ('copy' to copy stream)
-timecode hh:mm:ss[:;.]ff  set initial TimeCode value.
-pass n             select the pass number (1 to 3)
-vf filter_graph    set video filters
-ab bitrate         audio bitrate (please use -b:a)
-b bitrate          video bitrate (please use -b:v)
-dn                 disable data

Audio options:
-aframes number     set the number of audio frames to output
-aq quality         set audio quality (codec-specific)
-ar rate            set audio sampling rate (in Hz)
-ac channels        set number of audio channels
-an                 disable audio
-acodec codec       force audio codec ('copy' to copy stream)
-vol volume         change audio volume (256=normal)
-af filter_graph    set audio filters

Subtitle options:
-s size             set frame size (WxH or abbreviation)
-sn                 disable subtitle
-scodec codec       force subtitle codec ('copy' to copy stream)
-stag fourcc/tag    force subtitle tag/fourcc
-fix_sub_duration   fix subtitles duration
-canvas_size size   set canvas size (WxH or abbreviation)
-spre preset        set the subtitle options to the indicated preset

最上面部分是ffmpeg的版本信息和各模块的版本信息。

1.1 ffmpeg命令的语法结构

usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

语法结构很简单。
中括号中的参数是可选项。
options是对输入和输出都有影响的选项。
[[infile options] -i infile]...指定输入选项和输入文件，...表示可以包含多个输入。
{[outfile options] outfile}...指定输出选项和输出文件，...表示可以包含多个输出。

1.2 获取详细的help信息

ffmpeg -help给出了基本的帮助信息，其中下面的信息说明了如何获得更全面的帮助信息。

Getting help:
    -h      -- print basic options
    -h long -- print more options
    -h full -- print all options (including all format and codec specific options, very long)
    -h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter
    See man ffmpeg for detailed description of the options.

-h long: 打印更多的选项参数。
-h full: 打印所有的选项参数，包括所有针对于format和codec的选项，信息特别的长。
-h type=name: 打印打印指定名称的decoder/encoder/demuxer/muxer/filter的所有选项信息。
man ffmpeg: 查看ffmpeg的帮助手册。

特别强调一下-h type=name这个命令，要经常去使用这个命令。比如查看libx264支持的参数，执行ffmpeg -h encoder=libx264，会打印libx264 encoder的使用说明：

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
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)
  -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

1.3 打印帮助或支持能力的信息

ffmpeg -help打印的下面部分的信息说明了如何获取一些help信息和各种格式支持的能力。

Print help / information / capabilities:
-L                  show license
-h topic            show help
-? topic            show help
-help topic         show help
--help topic        show help
-version            show version
-buildconf          show build configuration
-formats            show available formats
-muxers             show available muxers
-demuxers           show available demuxers
-devices            show available devices
-codecs             show available codecs
-decoders           show available decoders
-encoders           show available encoders
-bsfs               show available bit stream filters
-protocols          show available protocols
-filters            show available filters
-pix_fmts           show available pixel formats
-layouts            show standard channel layouts
-sample_fmts        show available audio sample formats
-colors             show available color names
-sources device     list sources of the input device
-sinks device       list sinks of the output device
-hwaccels           show available HW acceleration methods

1.4 全局选项

帮助信息的下面部分是全局选项的说明。

Global options (affect whole program instead of just one file:
-loglevel loglevel  set logging level
-v loglevel         set logging level
-report             generate a report
-max_alloc bytes    set maximum size of a single allocated block
-y                  overwrite output files
-n                  never overwrite output files
-ignore_unknown     Ignore unknown stream types
-filter_threads     number of non-complex filter threads
-filter_complex_threads  number of threads for -filter_complex
-stats              print progress report during encoding
-max_error_rate ratio of errors (0.0: no errors, 1.0: 100% error  maximum error rate
-bits_per_raw_sample number  set the number of bits per raw sample
-vol volume         change audio volume (256=normal)

很多选项都经常使用，比如-v, -y。

1.5 文件选项

帮助信息的下面部分是针对每个文件可以指定的选项。

Per-file main options:
-f fmt              force format
-c codec            codec name
-codec codec        codec name
-pre preset         preset name
-map_metadata outfile[,metadata]:infile[,metadata]  set metadata information of outfile from infile
-t duration         record or transcode "duration" seconds of audio/video
-to time_stop       record or transcode stop time
-fs limit_size      set the limit file size in bytes
-ss time_off        set the start time offset
-sseof time_off     set the start time offset relative to EOF
-seek_timestamp     enable/disable seeking by timestamp with -ss
-timestamp time     set the recording timestamp ('now' to set the current time)
-metadata string=string  add metadata
-program title=string:st=number...  add program with specified streams
-target type        specify target file type ("vcd", "svcd", "dvd", "dv" or "dv50" with optional prefixes "pal-", "ntsc-" or "film-")
-apad               audio pad
-frames number      set the number of frames to output
-filter filter_graph  set stream filtergraph
-filter_script filename  read stream filtergraph description from a file
-reinit_filter      reinit filtergraph on input parameter changes
-discard            discard
-disposition        disposition

比如-f fmt指定文件的格式。
-c, -t, -to, -ss这几个选项都比较常用。

1.6 视频/音频/字幕相关的选项

帮助信息的下面部分是针对视频/音频/字幕相关的选项。

Video options:
-vframes number     set the number of video frames to output
-r rate             set frame rate (Hz value, fraction or abbreviation)
-s size             set frame size (WxH or abbreviation)
-aspect aspect      set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
-bits_per_raw_sample number  set the number of bits per raw sample
-vn                 disable video
-vcodec codec       force video codec ('copy' to copy stream)
-timecode hh:mm:ss[:;.]ff  set initial TimeCode value.
-pass n             select the pass number (1 to 3)
-vf filter_graph    set video filters
-ab bitrate         audio bitrate (please use -b:a)
-b bitrate          video bitrate (please use -b:v)
-dn                 disable data

Audio options:
-aframes number     set the number of audio frames to output
-aq quality         set audio quality (codec-specific)
-ar rate            set audio sampling rate (in Hz)
-ac channels        set number of audio channels
-an                 disable audio
-acodec codec       force audio codec ('copy' to copy stream)
-vol volume         change audio volume (256=normal)
-af filter_graph    set audio filters

Subtitle options:
-s size             set frame size (WxH or abbreviation)
-sn                 disable subtitle
-scodec codec       force subtitle codec ('copy' to copy stream)
-stag fourcc/tag    force subtitle tag/fourcc
-fix_sub_duration   fix subtitles duration
-canvas_size size   set canvas size (WxH or abbreviation)
-spre preset        set the subtitle options to the indicated preset

上面列出的选项大多数都是经常会用到的。

2. 流选择选项

一些媒体格式如Mp4、AVI等可以包含多种类型的流。
FFmpeg可以识别5种流类型：音频audio (a), 附件attachment (t), 数据data (d), 字幕subtitle (s) 和视频video (v)。
可以通过-map选项来选择需要的流，语法格式如下：

file_number:stream_type[:stream_number]

file_number和stream_number分别表示文件索引和流索引。
有一些特别的流选择指令：
-map 0 ：选择所有的流类型和其中所有的流。
-map i:v ：选择文件i中的所有视频流； -map i:a 选择所有的音频流；-map i:s
选择所有的字幕流。

3. 视频封装解封装

3.1 视频格式转换

ffmpeg -i input.avi c:a copy c:v copy output.mp4 
ffmpeg -i input.mp4 output.ts

3.2 分离/合并视频音频流

ffmpeg -i input-video -vn -c:a copy output-audio //分离音频流
//-vn is no video.
//-acodec copy says use the same audio stream that's already in there.

ffmpeg -i input-video -c:v copy -an output-video //分离视频流
//-an is no audio.
//-vcodec copy says use the same video stream that's already in there.

ffmpeg -i input-video -c:v copy -an output-video -c:a -vn output-audio //同时分离音频和视频流

ffmpeg -i video_file -i audio_file -c:v copy -c:a copy output_file //合并视频音频流

3.3 截取视频片段

ffmpeg -ss 5 -i input.mp4 -t 10 -c:v copy -c:a copy output.mp4
//-ss 5指定从输入视频第5秒开始截取，-t 10指明最多截取10秒。
//而-c:v copy -c:a copy标示视频与音频的编码不发生改变，而是直接复制，这样会大大提升速度，因为这样就不需要完全解码视频。

3.4 视频转换为m3u8格式

ffmpeg -i yoona.mp4 -c copy -map 0 -f segment -segment_list yoona.m3u8 -segment_time 10 yoona-%04d.ts

Set segment duration to time, the value must be a duration specification. Default value is "2".
Note that splitting may not be accurate, unless you force the reference stream key-frames at the given time. See the introductory notice and the examples below.

3.5 把视频文件推送到rtmp服务器

ffmpeg -re -i jack.mp4 -c copy -f flv rtmp://host/live/test

4. 视频解码编码

4.1 视频截图

获取视频时间点01:23:45的截图

ffmpeg -ss 01:23:45 -i input -vframes 1 -q:v 2 output.jpg

-i input file           the path to the input file
-ss 01:23:45            seek the position to the specified timestamp
-vframes 1              only handle one video frame
-q:v 2                  to control output quality. Full range is a linear scale of 1-31 where a lower value results in a higher quality. 2-5 is a good range to try.
output.jpg              output filename, should have a well-known extension

4.2 视频/图片尺寸修改

ffmpeg -i sample.jpg -s w*h out.jpg

4.3 分离视频的YUV通道分量

ffmpeg -i jack.mp4 -filter_complex "extractplanes=y+u+v[y][u][v]" -map "[y]" jack_y.mp4 -map "[u]" jack_u.mp4 -map "[v]" jack_v.mp4

4.4 图片序列与视频的互相转换

ffmpeg -i %04d.jpg output.mp4
ffmpeg -i input.mp4 %04d.jpg
\\第一行命令是把0001.jpg、0002.jpg、0003.jpg等编码成output.mp4，
\\第二行则是相反把input.mp4变成0001.jpg……。
\\%04d.jpg表示从1开始用0补全的4位整数为文件名的jpg文件序列。

5. 视频filter

5.1 视频加水印

ffmpeg -i xizong.mp4 -i fleight.jpg -filter_complex "overlay=W-w-5:5" -codec:a copy xizong_fleight.mp4
//在右上角加水印，边距为5像素。

5.2 视频旋转transpose

顺时针翻转90度

ffmpeg -i input -vf transpose=1 output

翻转180度

ffmpeg -i in.mp4 -vf "transpose=1,transpose=1" out.mp4

5.3 调色3DLutFilter

应用颜色查找表Lut，有‘nearest’、‘trilinear’、‘tetrahedral’三种插值算法，命令行调用如下：

ffmpeg -i log.mp4 -vf lut3d="file=DK79.cube"  out.mp4

5.4 图像/视频转换成黑白的

图像转换成黑白的

ffmpeg -i sample.png -vf hue=s=0 output.png

//把视频转换为黑白的
ffmpeg -i julin_5s.mp4 -vf hue=s=0 -c:a copy julin_monochrome.mp4

5.5 裁剪视频crop

使用-crop选项，语法如下：

crop=ow[:oh[:x[:y[:keep_aspect]]]]

ow、oh表示裁减之后输出视频的宽和高，
x、y表示在输入视频上开始裁减的横坐标和纵坐标，
keep_aspect: 1表示保持裁剪后输出的纵横比与输入一致，0表示不保持。

裁剪输入视频的左三分之一，中间三分之一，右三分之一:
ffmpeg -i input -vf crop=iw/3:ih :0:0 output
ffmpeg -i input -vf crop=iw/3:ih :iw/3:0 output
ffmpeg -i input -vf crop=iw/3:ih :iw/3*2:0 output

裁剪中间一半区域：
ffmpeg -i input -vf crop=iw/2:ih/2 output

5.6 视频尺寸缩放scale

将输入的1920x1080缩小到960x540输出

ffmpeg -i input.mp4 -vf scale=960:540 output.mp4 
//ps: 如果540不写，写成-1，即scale=960:-1, 那也是可以的，ffmpeg会通知缩放滤镜在输出时保持原始的宽高比。

5.7 视频中去水印delogo

使用delogo filter
它对logo周围像素的简单插值来实现。只需设置一个覆盖logo的矩形。在每个方向上，紧靠矩形外的下一个像素的值将用于计算矩形内的插值像素值。

语法：-vf delogo=x:y:w:h[:t[:show]] 
x:y 离左上角的坐标 
w:h logo的宽和高 
show：默认值0，若设置为1，指定区域的边界会绘制一个绿色的矩形框用于找到合适的x、y、w、h参数。

示例

ffmpeg -i input.mp4 -vf delogo=x=0:y=0:w=100:h=60 output.mp4

5.8 给视频或图像加上黑边pad

比如一个输入视频尺寸是1280x534的源，想要加上黑边变成1280x720，使用下面的命令可以实现。

ffmpeg -i input.mp4 -vf pad=1280:720:0:93:black output.mp4

按照从左到右的顺序依次为：“宽”、“高”、“X坐标”和“Y坐标”，宽和高指的是输入视频尺寸（包含加黑边的尺寸），X、Y指的是视频所在位置。
默认是加黑色的边，black可以不写。
上面的命令中93是根据(720-534) / 2计算得到。

如果视频原始1920x800的话，完整的语法应该是：

   -vf 'scale=1280:534,pad=1280:720:0:93:black'

先将视频缩小到1280x534，然后在加入黑边变成1280x720，将1280x534的视频放置在x=0，y=93的地方。

5.9 计算psnr/ssim

分析 psnr 主要是针对转码前的视频和转码后的视频的对比；如果转码是降分辨率，对比的时候，还需要对源视频加 -s widthxhigh;保证分辨率一致再做 psnr 和 ssim 的计算；

psnr

ffmpeg -i src.mp4  -i dst.mp4  -lavfi psnr="stats_file=psnr.log" -f null -

ssim

ffmpeg -i src.mp4  -i dst.mp4  -lavfi ssim="stats_file=ssim.log" -f null -

同时计算psnr和ssim

ffmpeg -i main.mpg -i ref.mpg -lavfi  "ssim;[0:v][1:v]psnr" -f null -

6. 音频解码编码

6.1 PCM原始数据和WAV格式转换

wav格式转换为PCM裸流

ffmpeg -i xizong.wav -f f32le -ar 44100 -acodec pcm_f32le output_f32le.raw

参数说明：
-f f32le … 浮点数32为小字端的采样格式
-ar 44100 … 采样频率
-ac 2 … 声道数量

PCM裸流转wav格式

ffmpeg -f f32le -ar 44100 -ac 2 -acodec pcm_f32le -i xizong_f32le.raw xizong_f32le.wav

说明需要先使用ffprobe查看wav中音频的采样格式，以上例子是使用的f32le采样格式的数据。

7. 音频filter

7.1 倍速atempo

速度减半

ffmpeg -i input.mp3 -af atempo=0.5 output.mp3

2倍速率

ffmpeg -i input.mp3 -af atempo=2 output.mp3

8. 字幕相关

8.1 字幕文件转换

字幕文件有很多种，常见的有 .srt , .ass 文件等。

//将.srt文件转换成.ass文件
ffmpeg -i subtitle.srt subtitle.ass

将.ass文件转换成.srt文件
ffmpeg -i subtitle.ass subtitle.srt

8.2 集成字幕到视频文件

ffmpeg -i input.mp4 -i subtitles.srt -c:s mov_text -c:v copy -c:a copy output.mp4

9. ffplay命令

9.1 ffplay播放yuv视频数据

ffplay -f <文件格式> -pix_fmt <像素格式> -video_size <视频尺寸> <文件名>
示例：
ffplay -f rawvideo -pix_fmt yuv420p -video_size 848x480 yuv_video

9.2 ffplay播放PCM音频数据

ffplay -f <格式名> -ac <声道数> -ar <采样率> <文件名>
示例：
ffplay -f f32le -ac 1 -ar 48000 pcm_audio

10. 其他

10.1 ffprobe查看媒体文件的信息

ffprobe target.mp4 -show_format -show_streams -print_format json -loglevel fatal

示例输出：

root@smallest:/home/video# ffprobe jack.mp4 -show_format -show_streams -print_format json -loglevel fatal
{
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "High",
            "codec_type": "video",
            "codec_time_base": "1/50",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 848,
            "height": 480,
            "coded_width": 848,
            "coded_height": 480,
            "has_b_frames": 1,
            "sample_aspect_ratio": "1:1",
            "display_aspect_ratio": "53:30",
            "pix_fmt": "yuv420p",
            "level": 30,
            "chroma_location": "left",
            "refs": 1,
            "is_avc": "true",
            "nal_length_size": "4",
            "r_frame_rate": "25/1",
            "avg_frame_rate": "25/1",
            "time_base": "1/25000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 39754000,
            "duration": "1590.160000",
            "bit_rate": "449785",
            "bits_per_raw_sample": "8",
            "nb_frames": "7499",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "creation_time": "2016-09-14T08:14:35.000000Z",
                "language": "und",
                "handler_name": "TrackHandler"
            }
        },
        {
            "index": 1,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "HE-AAC",
            "codec_type": "audio",
            "codec_time_base": "1/48000",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "48000",
            "channels": 2,
            "channel_layout": "stereo",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/24000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 7199744,
            "duration": "299.989333",
            "bit_rate": "48030",
            "max_bit_rate": "56888",
            "nb_frames": "7031",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "creation_time": "2016-09-14T08:11:52.000000Z",
                "language": "und",
                "handler_name": "Sound Media Handler"
            }
        }
    ],
    "format": {
        "filename": "jack.mp4",
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
        "format_long_name": "QuickTime / MOV",
        "start_time": "0.000000",
        "duration": "299.988333",
        "size": "18813764",
        "bit_rate": "501719",
        "probe_score": 100,
        "tags": {
            "major_brand": "mp42",
            "minor_version": "0",
            "compatible_brands": "isomavc1mp42",
            "creation_time": "2016-09-14T08:14:35.000000Z"
        }
    }
}

-print_format json: 结果以json格式呈现
-show_format: 打印封装格式信息，在format节点中。
-show_streams: 打印流信息，在streams节点中。

10.2 ffmpeg或ffplay 打开 DEBUG 日志输出。

$ ffplay -v debug $URL

API中开启debug日志

av_log_set_level(AV_LOG_DEBUG);

10.3 FFmpeg命令日志输出到文件

执行ffmpeg或者ffprobe输出重定向到文件的时候发现文件是空的。
可以采用下面的方式。

ffprobe xxx > file 2>&1

shell输出分好多种，0表示键盘输出，1表示屏幕输出，2表示错误输出。 cmd > file，只是把屏幕输出重定向到文件中。
调用ffmpeg相关命令，打印信息都被终端认为是错误输出，但是一般情况下这种信息也会输出到屏幕上,所以我们可以在屏幕上看到它。但是，当我们想重定向到文件中，却被系统认为是错误输出而忽略。
2>&1表示错误输出重定向到屏幕输出。&标明其后面跟的是一个文件描述符，而不是一个文件名。

10.4 打印支持DirectShow的设备列表

打印支持DirectShow的设备列表

ffmpeg -list_devices true -f dshow -i dummy

打开名称为“Lenovo EasyCamera”的摄像头

ffmpeg -f dshow -i video="Lenovo EasyCamera"