A quick guide to using FFmpeg to create cross-device web videos.

ffmpeg-web-video-guide.md

Video conversion with FFmpeg

Command basics

Most basic conversion using Terminal: ffmpeg -i input.mov output.webm.

Strip audio

Flag: -an.

Scale video

Example flag: -vf scale=1280:-2.

-1 for the width or height will keep it in ratio to the other specified dimension.

-2 will keep it in ratio to the other specified dimension, but, to ensure it is divisible by 2 (a requirement for certain encodings such as yuv420p) the width or height will be adjusted if necessary.

Docs here.

Faster processing

Flag: -threads 0.

Allow your CPU to use an optimal number of threads.

Convert to WebM

Guide here.

Audio example

ffmpeg -i input.mov -c:v libvpx -qmin 0 -qmax 25 -crf 4 -b:v 1M -vf scale=1280:-2 -c:a libvorbis -threads 0 output.webm

Mute example

ffmpeg -i input.mov -c:v libvpx -qmin 0 -qmax 25 -crf 4 -b:v 1M -vf scale=1280:-2 -an -threads 0 output.webm

Convert to MP4

Guide here.

QuickTime compatibility

Flag: -pix_fmt yuv420p.

Note: Requires dimensions to be divisible by 2.

All device compatibility

Flag: -profile:v baseline -level 3.0.

Android in particular doesn't support higher profiles.

Quality

Example flag: -crf 20.

0 is lossless, 23 is default, and 51 is worst possible. 18-28 is a sane range.

Fast start

Flag: -movflags +faststart.

Moves some data to the beginning of the file, allowing the video to be played before it is completely downloaded.

Audio example

ffmpeg -i input.mov -c:v libx264 -pix_fmt yuv420p -profile:v baseline -level 3.0 -crf 22 -preset veryslow -vf scale=1280:-2 -c:a aac -strict experimental -movflags +faststart -threads 0 output.mp4

Mute example

ffmpeg -i input.mov -c:v libx264 -pix_fmt yuv420p -profile:v baseline -level 3.0 -crf 22 -preset veryslow -vf scale=1280:-2 -an -movflags +faststart -threads 0 output.mp4

Bash script

1. In a folder, make sure your master videos are named how you want your exports to be named.
2. Save the bash script below as video4web.sh in the folder.
3. In Terminal, cd to the folder.
4. Run chmod +x video4web.sh.
5. Run the script using the parameters documented. E.g. ./video4web.sh mov 1280.

#!/bin/bash

# Generates a cover image along with mute web-ready WebM and MP4 files for each master video in a folder.
# See: https://gist.github.com/jaydenseric/220c785d6289bcfd7366 
# and msis fork: https://gist.github.com/msis/e8ab636071aefa1c1c5e19214571fbe2

# Parameter 1: Input video format (e.g. "mov").
# Parameter 2: Output width in pixels (e.g. "1280").
# Parameter 3: Path of source videos
# Parameter 4: Output path 
# Example use: "./video4web.sh mov 1280 ./src/ ./output/".

for i in $3/*.$1
do
  # Generate WebM
  ffmpeg -i $i -c:v libvpx -qmin 0 -qmax 25 -crf 4 -b:v 1M -vf scale=$2:-2 -an -threads 0 $4/${i%$1}webm
  # Generate MP4
  ffmpeg -i $i -c:v libx264 -pix_fmt yuv420p -profile:v baseline -level 3.0 -crf 22 -preset veryslow -vf scale=$2:-2 -an -movflags +faststart -threads 0 $4/${i%$1}mp4
done