SVA-CS2-24

Command Line Tools for Artists

Here are three useful tools and some tips on getting started.

ImageMagick - command line image manipulation

FFmpeg - everything audio/video related

Youtube DL - streaming video extractor!

If you get stuck with something, you can always look at the help manual for any command using the -h flag. For example, ffmpeg -h, will show you the options when running the ffmpeg command.

Imagemagick

Imagemagick is a powerful command line image editor that can do a lot of the functions that you probably use Photoshop for.

Installation

On a mac, type brew install imagemagick

On windows, use the binary to install: Imagemagick - Windows Binary Release

Anatomy of a Command

convert inputName.ext -some_command options outputName.ext

On Windows, use magick to run a command instead of convert

Useful Commands

Convert Filetypes

• convert file.jpg file.png - convert a single jpg to a png, changing the output name will change the file name
• convert '*.jpg' -set filename:out "%[basename]" '%[filename:out].png' - convert all jpg to pngs

Gif Magick!

• convert *.jpg -loop 0 test.gif - creates a gif from any jpeg that is in a folder

Resize and convert!

• convert input.jpg -resize 900x900 test.png - larger dimension resized to 900px, the small dimension is auto scaled, aspect ratio is maintained
• convert input.jpg -resize 900 test.png - set width, auto set height, aspect ratio is maintained
• convert input.jpg -resize x900 test.png - set height, auto set width, aspect ratio is maintained
• convert input.jpg -resize 200% test.png - both dimensions scaled by 200%, aspect ratio is maintained
• convert input.jpg -resize 200x50% test.png - width is scaled by 200%, height is scaled to 50%, aspect ratio is lost.
• convert '*.jpg' -resize 200 -set filename:out '%[basename]' './thumbs/thumbs-%[filename:out].png' - resize all images to 200px width, save to a folder ‘thumbs’ with a new filename thumbs + original filename.

Trim and Crop

• convert image.jpg -crop 200x200 - creates 200px by 200px tiles of any image automatically
• convert image.jpg -crop 200x200+100+200 cropped.jpg - creates a single image, 200px by 200px, 100 is the x offset and 200 the y offset
• convert image.jpg -trim new.jpg - auto crop! Removes any unwanted empty space around an image.

Batch with mogrify

Warning, mogrify overwrites file by default! Can do permanent damage if you don’t have it write to a new file!

• mogrify -format jpg *.png - This is safe! Changes all png files to jpg, writes new files perserving originals
• mogrify -resize 20x20 *.jpg - Danger! Overwrites all images resized to 20 by 20px.

Resources

• Commands
• Mogrify - inline batch processing
• Example Gallery

FFmpeg

FFmpeg is a command line tool for audio/video. It is used a lot in other conversion tools.

Installation

On a mac, type brew install ffmpeg

On a PC, use this link to download an build from source. link

Anatomy of a Command

ffmpeg -i input.xyz options output.xyz

Useful Commands

Convert between Formats and Codecs

ffmpeg -i input.xyz output.xyz

See the list of formats + codecs:

• ffmpeg -formats
• ffmpeg -codecs
• ffmpeg -i myfile.mp4 -vcodec libx265 myfile_265.mp4 - applies a specific codec when converting

Movie to GIF

ffmpeg -i input.mp4 -f gif output.gif - convert a movie file to a gif

You can lower the frame rate by adding -r 10 changing the frame rate to 10. Similarly, adding -r 320x240 will change the image size.

Too Big? Try using imagemagick to optimize the gif convert -layers Optimize output.gif output_optimized.gif

Trim

ffmpeg -ss 10 -i input.mp4 -c copy -t 15 output.mp4 - trim a video without re-encoding

Explainer:

• ffmpeg - launches FFmpeg
• -ss ## - start from __ in sec
• -i input.mp4 - input file
• -c copy - use existing codec (instant, no re-encoding)
• -t ## - duration for new clip in sec (use -to ## for time in clip)
• output.mp4 - name/path for new output file

Extract frames

Use the -vf flag to output video frames.

Make a directory for the frames mkdir frames

Set input file, frames per second for output, file path/type: ffmpeg -i input.mp4 -vf fps=1 frames/out_%04d.png

Explainer:

• -vf fps=1 exports # frames per second
• %04d specify how you want the frames to be numbered, this uses 4 padded digits (0000, 0001, …)

Extract Audio

ffmpeg -i in.mp4 -vn -ac 2 out.mp3 - Extract audio and convert to mp3 (or other format):

Merge Audio + Video

Merge an audio and video, uses the shortest one as the file length ffmpeg -i input.mov -i input.mp3 -c:v copy -map 0:v:0 -map 1:a:0 -shortest output.mov

Video from directory

Create a movie from a directory of images! ffmpeg -framerate 30 -pattern_type glob -i '*.png' \ -c:v libx264 -pix_fmt yuv420p out.mp4

Explainer:

• -framerate 30 sets number of frames per second
• *.png searches for PNGs (or use *.jpg)

Speed

Useful to speed up long screen-recordings: ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" output.mp4

Explainer:

• -filter:v "setpts=0.5*PTS" 0.5 = faster, 1.0 = normal, 1.5 = slower

Playback

FFmpeg ships with a minimal audio/video player ffplay that you can launch from the terminal.
ffplay input.mp4

Useful shortcuts:

• q/ESC (quit)
• f (toggle fullscreen)
• p / SPACEBAR (toggle pause)
• m (toggle mute)
• left/right (seek backward/forward 10 seconds)
• up/down (seek backward/forward 1 minute)

Loop endless at fullscreen: ffplay -fs -loop 0 *input.mp4

View audio waveform: ffplay -showmode 1 *input.mp4

View audio frequency (FFT) spectrogram: ffplay -showmode 2 input.mp4

View debug Motion Vectors: ffplay -flags2 +export_mvs -vf codecview=mv=pf+bf+bb input.mp4

Export Motion Vectors only: ffmpeg -flags2 +export_mvs -i input.mp4 -vf "split[src],codecview=mv=pf+bf+bb[vex],[vex][src]blend=all_mode=difference128,eq=contrast=7:brightness=-1:gamma=1.5" -c:v libx264 output.mp4

Additional Links

• FFmpeg CLI guide
• Rick Companje - FFMpeg Tips
• Complete list of ffmpeg flags / commands
• Werner Robitza FFmpeg guide
• 20 FFmpeg commands for beginners
• Fancy (ffplay) Filtering Examples
• More tips for converting images to video
• Ludwig Zeller FFmpeg Cheatsheet
• Giphy Engineering FFmpeg Guide

youtube-dl

youtube-dl is an online media extractor.
The ultimate tool for downloading and archiving media files from almost any website.
Lately, there’s been more activity and updates on a fork, youtube-dlp, so might be better to use this one.

Install

On a mac, type brew install yt-dlp for the forked version that works with more sites and has more options.

For Windows, download the .exe from here

Anatomy of a command

cd into the directory where you want to save the video.

yt-dlp *some url**

Formats

Most hosted videos have multiple files to stream depending on connection speed / quality.

List formats: yt-dlp *VIDEO_URL* -F

It will return a long list of available formats, starting with an ID.
Then download the one you prefer: yt-dlp *VIDEO_URL* -f ##

Or download the best mp4 or similar format: yt-dlp -f 'bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best' *VIDEO_URL*

Or download the best m4a or audio format: yt-dlp -f 'bestaudio[ext=m4a]' *VIDEO_URL*

After using yt-dlp you can use ffmpeg to trim video, make it a gif, or perform other tasks!

Additional Links

• yt-dlp options, laundry list of features to use
• youtube-dlg, a GUI approach for yt-dl(p)