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📽️FFmpeg

#FFmpeg202
AI-generated summary
FFmpeg is a versatile tool for recording, converting, and streaming audio and video. It consists of three command line tools: ffmpeg, ffplay, and ffprobe. This note focuses on the usage of FFmpeg. To install FFmpeg on Windows, you can download the release build from the official site and add it to the system path. On Ubuntu, you can easily install FFmpeg using the apt command. FFmpeg can be used to edit videos with simple commands. You can obtain basic information about a video using the -i command. Transcoding allows you to convert video files from one encoding to another, while transmuxing transfers video files from one container format to another. Transrating adjusts the bit rate of a file, and transsizing changes the video resolution.

ffmepg

FFmpeg is a complete, cross-platform solution to record, convert and stream audio and video. This is my FFmpeg learning notes. Using ffmpeg as video editor and converter. Change the fps and convert .mp4 file to .gif and other formats.

Overview#

FFmpeg is short for "Fast Forward Moving Pictures Experts Group". It is a huge project and it provides 3 command line tools as follow

  • fmpeg: video and audio converter.
  • ffplay: media player.
  • ffprobe: gathers information from multimedia streams.

This note mainly review some of the usages of FFmpeg, which is most useful. The documentation of ffplay and ffprobe is available in Internet and it's convenient to check.

Install#

Windows#

Enter the official site of FFmpeg and choose CODEX FFMPEG @ gyan.dev, find the "release build" section, download ffmpeg-release-full.7z file, then unpack the compressed package locally, and finally add ffmpeg to the system path, then type in your powershell and get logs like this

$ ffmpeg -version
ffmpeg version 5.0-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 11.2.0 (Rev5, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil      57. 17.100 / 57. 17.100
libavcodec     59. 18.100 / 59. 18.100
libavformat    59. 16.100 / 59. 16.100
libavdevice    59.  4.100 / 59.  4.100
libavfilter     8. 24.100 /  8. 24.100
libswscale      6.  4.100 /  6.  4.100
libswresample   4.  3.100 /  4.  3.100
libpostproc    56.  3.100 / 56.  3.100

And that means you have completely install the FFmpeg.

If there are previous versions of FFmpeg, we need to delete them.

Ubuntu#

It's quite easy to install FFmpeg on Ubuntu compared with Windows, just use apt for installing

sudo apt install ffmpeg

Usage#

It's convenient to edit videos using ffmpeg with simple commands.

Information#

We can print the basic information of a video using command below

ffmpeg -i <input file>

If you want to hide the redundant1 info, add -hide_banner

ffmpeg -i <input file> -hide_banner

Transcoding#

Transcoding means converting video files from one encoding to another, like from H.264 encoding to H.265, usually we use encoder libx265, so the command goes like

ffmpeg -i <input file> -c:v libx265 <output file>

If you want to reverse from H.265 to H.264, just change the encoder to libx264.

Transmuxing#

Transmuxing means transfer video files from one container to another. Notice that transfering container does not change encoding, so it's pretty fast. Here is an example from .mp4 to .webm

ffmpeg -i <input file>.mp4 -c copy <output file>.webm

In the command above, -c copy means copy directly, without transcoding.

Transrating#

Transrating means adjusting bit rate, often used to reduce the size of a file. We can set the maximum rate, minimum rate and the buffer, like 3856K for maximum rate, 964K for minimum rate and 2000K for buffer size. Command like

ffmpeg -i <input file> -minrate <minimum rate> -maxrate <maximum rate> -bufsize <buffer> <output file>

Transsizing#

Transsizing means changing video resolution2, also called scale3 Control.

If the video is a high definition file, and we want to scale it down to reduce the size, then we can use the scale control commands.

ffmpeg -i <input file> -vf scale=<width>:<height>:flags=lanczos <output file>

lanczos is the algorithm of zoom, and if we want to set the width of the output file to half the width of the source video and the height to scale proportionally4, we will set the scale like this

ffmpeg -i <input file> -vf scale=iw/2:-1 :flags=lanczos <output file>

The iw means video width, obviously ih means video height, and -1means zoom proportionally. And we can also set the pixels of width and height. If we wnat to get a 480p video, just set the width to 480.

ffmpeg -i <input file> -vf scale=480:-1 <output file>

Demuxing#

Demuxing means extracting audio from video. It goes like this

ffmpeg -i <input file>.mp4 -vn -c:a copy <output file>.aac

In the command above, -vn means removing video, -c:a copy indicates that the audio encoding is not changed, and is copied directly.

Muxing#

Muxing means adding external audio to the video, such as adding background music or narration5.

ffmpeg -i <input file>.aac -i <input file>.mp4 <output file>.mp4

There are 2 input files, one audio and one video, and FFmpeg combine them as one.

Screenshots#

Screenshots need a start time and a last time, and it means from the start time, get sreenshots continuosly till last time ends.

ffmpeg -y -i <input file> -ss <start time> -t <last time> <output file>_%3d.png

And if you only need a frame of screenshot, it's also available

ffmpeg -ss <cut time> -i <input file> -vframes 1 -q:v 2 <output>.png

In the above command, -vframes 1 specifies that only one frame is to be captured, and -q:v 2 indicates the output image quality, which is generally between 1 and 5 (1 is the highest quality).

Cutting#

Usually we only need a part of video, so we can cut it with start time and last time or end time

ffmpeg -ss <start time> -i <input file> -t <last time> -c copy <output file>
ffmpeg -ss <start time> -i <input file> -to <end time> -c copy <output file>

Time unit is second, and we can also use format like 00:00:00.000, which represents hours:minutes:seconds.points. -c copy means do not change the encoding format of audio and video, copy directly, which will be much faster.

Loop#

If we convert to .gif file or other animation pictures, we can set the loop times, basically 1 for once, and 0 for infinity.

ffmpeg -i <input file> -loop <loop times> <output file>

Adjusting#

FFmpeg allows you to adjust video playback speed. To increase the video playback speed, just run

ffmpeg -i <input file> -vf "setpts=0.5*PTS" <output file>

This command will double the speed of the video. To slow down your video you need to use a parameter greater than 1, like

ffmpeg -i <input file> -vf "setpts=4.0*PTS" <output file>

Compressing#

GIF#

It's direct to convert videos like .mp4 files to .gif animations, just use commands below

ffmpeg -i <input>.mp4 <output>.gif

The default conversion is medium quality mode, to convert high quality gif, you can modify the bit rate

ffmpeg -i <input>.mp4 -b 2048k <output>.gif
ffmpeg -i <input>.mp4 -lossless 1 <output>.gi

We can also convert gif file to other formats

ffmpeg -f gif -i <input>.gif <output file

WEBP#

The following command line can convert the file named <input.mp4> into a lossless, loop played file named <output.webp> with size 800:600 and default persentation.

ffmpeg -i <input>.mp4 -vcodec libwebp -filter:v fps=fps=20 -lossless 1 -loop 0 -preset default -an -vsync 0 -s 800:600 <output>.webp

If you want the exported output.webp animation to be played only once, it is lossy, the compression level is 3 (0-6, the default is 4, the higher the better the effect), the quality is 70 (0-100, the default is 75, the higher The better the effect), rendering6 as a picture.

ffmpeg -i <input>.mp4 -vcodec libwebp -filter:v fps=fps=20 -lossless 0 -compression_level 3 -q:v 70 -loop 1 -preset picture -an -vsync 0 -s 800:600 <output>.webp

Reference#

参考#

Footnotes#

  1. adi. 冗余的；多余的 ↩

  2. n. 分辨率 ↩

  3. n. 规模；范围；程度；等级；级别；vt. 攀登；改变... 的大小 ↩

  4. adv. 按比例的 ↩

  5. n. 旁白 ↩

  6. v. 渲染 ↩

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