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视音频技术-FFmpeg命令行基础

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1、FFmpeg命令行基础

FFmpeg官网：

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http://ffmpeg.org/

FFmpeg程序下载：包括Windows、MacOS、Linux等操作系统，包括FFmpeg、FFprobe、FFplay、FFserver等程序。

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http://ffmpeg.org/download.html

FFmpeg命令行文档：

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http://ffmpeg.org/ffmpeg.html

FFplay命令行文档：

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http://ffmpeg.org/ffplay.html

2、配置FFmpeg环境变量

MacOS上配置FFmpeg环境变量：

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vi ~/.bash_profile

按I键编辑文本：

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export PATH=${PATH}:/Users/zhangchaozhou/Documents/Software/ffmpeg-4.4

按ESC停止编辑，并按:wq键保存退出编辑。
更新配置：

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source ~/.bash_profile

如果环境变量PATH被修改，需在命令行执行：

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export PATH=/bin:/usr/bin:$PATH

执行FFmpeg：

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TeochewZhang:video zhangchaozhou$ ffmpeg -hide_banner -help
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/bsf/protocol
    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 maximum error rate  ratio of decoding errors (0.0: no errors, 1.0: 100% errors) above which ffmpeg returns an error instead of success.
-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)
-fpsmax rate        set max 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

3、常用命令

3.1、获取文件信息

使用-i参数。

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$ ffmpeg -i input.mp4

加上-hide_banner参数，可以只显示元信息，去除冗余信息。

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$ ffmpeg -i input.mp4 -hide_banner

示例：

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TeochewZhang:video zhangchaozhou$ ffmpeg -i 那些年，我们一起追的女孩.mp4 -hide_banner
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '那些年，我们一起追的女孩.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.19.100
  Duration: 00:00:30.32, start: 0.000000, bitrate: 397 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x208 [SAR 16:15 DAR 32:13], 261 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]

3.2、转换编码格式/transcoding

将视频文件从一种编码转成另一种编码。比如转成 H.264 编码，一般使用编码器libx264，所以只需指定输出文件的视频编码器即可。

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$ ffmpeg -i [input.file] -c:v libx264 output.mp4

示例：

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TeochewZhang:video zhangchaozhou$ ffmpeg -i Forrest_Gump_IMAX.mp4 -c:v libx264 output.mp4 -hide_banner
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Forrest_Gump_IMAX.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.19.100
  Duration: 00:00:31.21, start: 0.000000, bitrate: 878 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x352, 748 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7fcc4e803e00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7fcc4e803e00] profile High, level 3.0, 4:2:0, 8-bit
[libx264 @ 0x7fcc4e803e00] 264 - core 161 r3048 b86ae3c - H.264/MPEG-4 AVC codec - Copyleft 2003-2021 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=11 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=23 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.76.100
  Stream #0:0(und): Video: h264 (avc1 / 0x31637661), yuv420p(progressive), 640x352, q=2-31, 23.98 fps, 24k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc58.134.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc58.134.100 aac
frame=  744 fps=297 q=-1.0 Lsize=    3080kB time=00:00:31.18 bitrate= 809.1kbits/s speed=12.4x    
video:2595kB audio:460kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.800888%
[libx264 @ 0x7fcc4e803e00] frame I:20    Avg QP:17.34  size: 24048
[libx264 @ 0x7fcc4e803e00] frame P:245   Avg QP:22.46  size:  6089
[libx264 @ 0x7fcc4e803e00] frame B:479   Avg QP:24.79  size:  1428
[libx264 @ 0x7fcc4e803e00] consecutive B-frames:  7.0% 18.8%  8.1% 66.1%
[libx264 @ 0x7fcc4e803e00] mb I  I16..4: 34.0% 22.0% 44.0%
[libx264 @ 0x7fcc4e803e00] mb P  I16..4:  5.4%  8.7%  3.1%  P16..4: 30.5% 12.4%  7.2%  0.0%  0.0%    skip:32.7%
[libx264 @ 0x7fcc4e803e00] mb B  I16..4:  0.7%  0.6%  0.4%  B16..8: 30.4%  4.7%  1.6%  direct: 2.1%  skip:59.5%  L0:45.2% L1:43.1% BI:11.7%
[libx264 @ 0x7fcc4e803e00] 8x8 transform intra:40.6% inter:46.7%
[libx264 @ 0x7fcc4e803e00] coded y,uvDC,uvAC intra: 45.5% 49.2% 16.2% inter: 12.0% 10.6% 0.5%
[libx264 @ 0x7fcc4e803e00] i16 v,h,dc,p: 39% 35% 13% 13%
[libx264 @ 0x7fcc4e803e00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 15% 34% 20%  3%  5%  5%  6%  4%  6%
[libx264 @ 0x7fcc4e803e00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 15% 30% 13%  5%  7%  7%  8%  6%  8%
[libx264 @ 0x7fcc4e803e00] i8c dc,h,v,p: 53% 31% 11%  5%
[libx264 @ 0x7fcc4e803e00] Weighted P-Frames: Y:24.9% UV:20.4%
[libx264 @ 0x7fcc4e803e00] ref P L0: 62.2% 20.9% 13.6%  3.0%  0.3%
[libx264 @ 0x7fcc4e803e00] ref B L0: 89.2%  9.0%  1.7%
[libx264 @ 0x7fcc4e803e00] ref B L1: 98.3%  1.7%
[libx264 @ 0x7fcc4e803e00] kb/s:684.96
[aac @ 0x7fcc4e805600] Qavg: 4577.948

3.3、转换容器格式/transmuxing

将视频文件从一种容器转到另一种容器。
内部的编码格式不变，使用-c copy指定直接拷贝，不经过转码。

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$ ffmpeg -i input.mp4 -c copy output.webm

3.4、调整码率/transrating

改变编码的比特率，一般用来将视频文件的体积变小。
指定码率最小为964K，最大为3856K，缓冲区大小为 2000K。

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$ ffmpeg \
-i input.mp4 \
-minrate 964K -maxrate 3856K -bufsize 2000K \
output.mp4

3.5、改变分辨率/transsizing

从 1080p 转为 480p 。

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$ ffmpeg \
-i input.mp4 \
-vf scale=480:-1 \
output.mp4

3.6、提取音频/demuxing

从视频里面提取音频，-vn表示去掉视频，-c:a copy表示不改变音频编码，直接拷贝。

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$ ffmpeg \
-i input.mp4 \
-vn -c:a copy \
output.aac

3.7、添加音轨/muxing

将外部音频加入视频，比如添加背景音乐或旁白。

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$ ffmpeg \
-i input.aac -i input.mp4 \
output.mp4

3.8、截图

从指定时间开始，连续对1秒钟的视频进行截图。

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$ ffmpeg \
-y \
-i input.mp4 \
-ss 00:01:24 -t 00:00:01 \
output_%3d.jpg

指定只截取一，-vframes 1指定只截取一帧，-q:v 2表示输出的图片质量，一般是1到5之间（1 为质量最高）。

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

3.9、裁剪/cutting

截取原始视频里面的一个片段，输出为一个新视频。可以指定开始时间（start）和持续时间（duration），也可以指定结束时间（end）。
-c copy表示不改变音频和视频的编码格式，直接拷贝。

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$ ffmpeg -ss [start] -i [input] -t [duration] -c copy [output]
$ ffmpeg -ss [start] -i [input] -to [end] -c copy [output]
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$ ffmpeg -ss 00:01:50 -i [input] -t 10.5 -c copy [output]
$ ffmpeg -ss 2.5 -i [input] -to 10 -c copy [output]

3.10、为音频添加封面

有些视频网站只允许上传视频文件。如果要上传音频文件，必须为音频添加封面，将其转为视频，然后上传。
将音频文件，转为带封面的视频文件。

-loop 1参数表示图片无限循环，-shortest参数表示音频文件结束，输出视频就结束。

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$ ffmpeg \
-loop 1 \
-i cover.jpg -i input.mp3 \
-c:v libx264 -c:a aac -b:a 192k -shortest \
output.mp4