Encode mp4, webm and gif using ffmpeg (2.6 or above). Audio is discarded on all of these!

gifenc.sh

#!/bin/sh

# sh gifenc.sh input.mp4 output.gif
# Optionally accepts width / height (one or both).

palette="/tmp/palette.png"
filters="fps=15"
if [ -n "$3" ]; then
  if [ -n "$4" ]; then
    filters="$filters,scale=$3:$4"
  else
    filters="$filters,scale=$3:-1"
  fi
  filters="$filters:flags=lanczos"
fi

ffmpeg -v warning -i "$1" -vf "$filters,palettegen" -y $palette
ffmpeg -v warning -i "$1" -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y "$2"

mp4enc.sh

#!/bin/sh

# sh mp4enc.sh input.mp4 output.mp4 [quality]
# Optionally accepts a "quality" parameter (defaults to 640).
# https://www.virag.si/2012/01/web-video-encoding-tutorial-with-ffmpeg-0-9

quality="640k"
if [ -n "$3" ]; then
  quality="$3k"
fi
options="-c:v libx264 -b:v $quality -maxrate $quality -bufsize 1000k -profile:v high -preset veryslow -tune film -movflags +faststart -threads 1"

ffmpeg -y -i "$1" $options -pass 1 -an -f rawvideo /dev/null && ffmpeg -i "$1" $options -pass 2 -an "$2"

webmenc.sh

#!/bin/sh

# sh wemenc.sh input.mp4 output.webm [quality]
# Optionally accepts a "quality" parameter (defaults to 700).
# https://www.virag.si/2012/01/webm-web-video-encoding-tutorial-with-ffmpeg-0-9

quality="700k"
if [ -n "$3" ]; then
  quality="$3k"
fi
options="-c:v libvpx -b:v $quality -maxrate $quality -bufsize 1000k -preset veryslow -tune film -movflags +faststart -threads 1"

ffmpeg -y -i "$1" $options -pass 1 -an -f rawvideo /dev/null && ffmpeg -i "$1" $options -pass 2 -an "$2"

May I add an improvement to gifenc.sh? It's better to encase $1 and $2 in double quotes, this allows for filenames to have spaces in their names.

Last line of your script would be:

ffmpeg -v warning -i "$1" -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y "$2"

Love your script. Been working on this today. This now accepts parameters from the command line and sets up defaults in case they are not present. Essentially only the input file is needed as parameter, everything else is automated. https://gist.github.com/Zettt/30b0b3b52f33a2cbcb55

Cheers!

@Zettt Apologies for the multi-year delay here, I missed your comments before! I've applied your suggestion, we certainly don't want word splitting.