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1 FFmpeg是什么

  ffmpeg是一套用来记录、转换数字音频、视频，并能将其转化为流的开源计算机程序。采用LGPL或GPL许可证。它包含了非常先进的音频/视频编解码库libavcodec，提供了录制、转换以及流化音视频的完整解决方案。

  许多FFmpeg的开发人员都来自MPlayer项目，而且当前FFmpeg也是放在MPlayer项目组的服务器上。项目名称来自MPEG视频编码标准，前面的"FF"代表"Fast Forward"，即Fast forword mpeg，音视频转换器。

github地址
https://github.com/FFmpeg/FFmpeg

2 FFmpeg能做什么

1 色彩转换、缩放视频尺寸、视频抽帧、去噪、模糊、压缩、剪切、转码、截图、旋转、添加/去除水印、播放速度、封面、转换3D的VR视频、 图片转视频

2 音频转码、剪切、拼接、各类音效、音量、抽象音频、音乐频谱波形图

3 安装FFmpeg

	//mac
	brew search ffmpeg
	brew install ffmpeg
	
	//linux
	yum install ffmpeg
	sudo apt install ffmpeg

验证安装

tom@bogon ~ % ffmpeg -version
ffmpeg version 6.0 Copyright (c) 2000-2023 the FFmpeg developers
built with Apple clang version 14.0.0 (clang-1400.0.29.202)
configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/6.0 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-neon
libavutil      58.  2.100 / 58.  2.100
libavcodec     60.  3.100 / 60.  3.100
libavformat    60.  3.100 / 60.  3.100
libavdevice    60.  1.100 / 60.  1.100
libavfilter     9.  3.100 /  9.  3.100
libswscale      7.  1.100 /  7.  1.100
libswresample   4. 10.100 /  4. 10.100
libpostproc    57.  1.100 / 57.  1.100

版本信息里有ffmpeg的版本6.0，平台apple，配置configuration以及核心模块

4 核心模块

名称	说明
libavutil	工具库，比如算数运算、字符操作等
libavcodec	音视频编解码核心库
libavformat	I/O操作和封装格式(muxer/demuxer)处理
libavdevice	各种设备的输入输出
libavfilter	滤镜特效处理
libswscale	视频像素处理，包括缩放图像尺寸、色彩映射转换、像素颜色空间转换等
libswresample	音频重采样，格式转换和混音
libpostproc	后期效果处理，如图像的去块效应

一般转码过程

5 常见参数说明

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)
-display_rotation angle  set pure counter-clockwise rotation in degrees for stream(s)
-display_hflip      set display horizontal flip for stream(s) (overrides any display rotation if it is not set)
-display_vflip      set display vertical flip for stream(s) (overrides any display rotation if it is not set)
-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
-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)
-ab bitrate         audio bitrate (please use -b:a)
-af filter_graph    set audio filters

6 简单Demo

6.1 图片生成视频

ffmpeg -r 25 -f image2 -i ./xuanmu/activity_%d.png -vcodec libx265 -vtag hvc1 -crf 25  -pix_fmt yuv420p out.mp4 -y

6.2 视频旋转90度

ffmpeg -i out.mp4 -vf transpose=1 test.mp4

6.3 视频翻转

ffmpeg -i input.mp4 -vf reverse -an output.mp4

6.4 视频截图

ffmpeg -ss 0 -i input.mp4 -f image2 -vframes 1 -an screenshot.jpg

6.5 视频水印

ffmpeg -i qd.mp4 -i 46x46.png -filter_complex overlay=10:20 watermark.mp4

6.6 转换3D的VR视频

ffmpeg -i qd.mp4 -filter_complex stereo3d=sbsl:arbg stereo3d.mp4 -y

6.7 音频混音

ffmpeg -i 1.mp3 -i 2.mp3 -filter_complex amix=inputs=2:duration=first -vn mix.mp3

6.8 空灵音效（没太听出来效果）

ffmpeg -i input.mp3 -af aecho=0.8:0.8:1000:0.5 echo.mp3

6.9 搞笑音效

ffmpeg -i 1.mp3 -filter_complex atempo=2 atempo.mp3

6.10 音乐频谱波形图（安河桥）

ffmpeg -i 1.mp3 -filter_complex showwavespic=s=1280x720 waveform.png

6.11 音频拼接

ffmpeg -i concat:"1.mp3|2.mp3" -acodec copy -vn concat.mp3

6.12 视频自定义宽高

ffmpeg -i qd.mp4 -s 720x480  -threads 4 -c:a copy target.mp4 -y

参考文档

1 https://trac.ffmpeg.org/wiki/TitleIndex
2 https://zhuanlan.zhihu.com/p/37516093
3 ffmpeg official document
4 https://blog.csdn.net/u011686167/article/details/120879467
5 https://blog.csdn.net/u011686167/article/details/120879467