Use FFmpeg to resize and generate .mp4 & .webm videos from any source video.

convert-videos-for-web.sh

#!/bin/bash

#Scaling
#- Scale can be used as is which will set the height to 560 but keep aspect ratio for width.
#- Other options include setting both with & height
#- Watch out for sizing errors when not divisible by 2

if [[ ! "$1" || ! "$2" || ! "$3" ]] || [[ "$1" = '--help' ]]; then
	if [[ "$1" = '--help' ]]; then
		echo " "
		echo "Converts input video files for the web, with several parameters to ease the process and replicate across projects:"
		echo " "
	else
		echo " "
		echo "Please provide all the necessary parameters"
		echo " "
	fi
	echo "Usage: video-convert <input file> <scale factor> <scale amount> <#thumbnail frame> <#output name> // # means not required"
	echo "Example: video-convert video.mov width 720 // Converts video and scales it aspectly based on a width of 720"
	echo "Example: video-convert video.mov height 560 25 // Converts video and scales it aspectly based on a height of 560 and exports thumbnail at 25 seconds in"
	echo "Example: video-convert video.mov height 560 25 myvideo // Converts video and scales it aspectly based on a height of 560 and exports thumbnail at 25 seconds in, and exports videos to myvideo.extension.  Default name is the input file name with a different extension"
		echo " "
else
	input="$1"
	factor="$2"
	even=$(( $3 - ($3 % 2) )) # Makes scale amount even just incase an odd number is given
	scale="$even"
	if [[ ! "$4" ]]; then
		frame="1"
	else
		frame="$4"
	fi
	if [[ ! "$5" ]]; then
		output="${input%.*}"
	else
		output="$5"
	fi
	echo "input is $input, output is $output"
	echo "scale factor is $2, scale amount is $scale"
	echo "thumbnail frame is $frame"
	if [ "$factor" = 'height' ]; then
		#MP4 1st pass
		ffmpeg -i "$input" -vcodec libx264 -vprofile high -preset veryslow -b:v 225k -maxrate 300k -bufsize 1000k -vf scale="trunc(oh*a/2)*2:$scale" -threads 2 -pass 1 -y -an -f mp4 /dev/null
		#MP4 with audio 2nd pass
		ffmpeg -i "$input" -vcodec libx264 -vprofile high -preset veryslow -b:v 225k -maxrate 300k -bufsize 1000k -vf scale="trunc(oh*a/2)*2:$scale" -threads 2 -pass 2 -acodec mp3 -b:a 128k -f mp4 "$output.mp4"
		#webm 1st pass
		ffmpeg -i "$input" -codec:v libvpx -quality good -cpu-used 0 -b:v 225k -qmin 10 -qmax 42 -maxrate 300k -bufsize 1000k -threads 2 -vf scale="trunc(oh*a/2)*2:$scale" -y -an -pass 1 -f webm /dev/null
		#webm 2st pass with audio
		ffmpeg -i "$input" -codec:v libvpx -quality good -cpu-used 0 -b:v 225k -qmin 10 -qmax 42 -maxrate 300k -bufsize 1000k -threads 2 -vf scale="trunc(oh*a/2)*2:$scale" -codec:a libvorbis -b:a 128k -pass 2 -f webm "$output.webm"
		#Generate single image from selected frame of video (default is 1), scale and save as jpg
		ffmpeg -i "$input" -ss $frame -vframes 1 -vf scale="trunc(oh*a/2)*2:$scale" "$output.jpg"
	elif [ "$factor" = 'width' ]; then
		#MP4 1st pass
		ffmpeg -i "$input" -vcodec libx264 -vprofile high -preset veryslow -b:v 225k -maxrate 300k -bufsize 1000k -vf scale="$scale:trunc(ow/a/2)*2" -threads 2 -pass 1 -y -an -f mp4 /dev/null
		#MP4 with audio 2nd pass
		ffmpeg -i "$input" -vcodec libx264 -vprofile high -preset veryslow -b:v 225k -maxrate 300k -bufsize 1000k -vf scale="$scale:trunc(ow/a/2)*2" -threads 2 -pass 2 -acodec mp3 -b:a 128k -f mp4 "$output.mp4"
		#webm 1st pass
		ffmpeg -i "$input" -codec:v libvpx -quality good -cpu-used 0 -b:v 225k -qmin 10 -qmax 42 -maxrate 300k -bufsize 1000k -threads 2 -vf scale="$scale:trunc(ow/a/2)*2" -y -an -pass 1 -f webm /dev/null
		#webm 2st pass with audio
		ffmpeg -i "$input" -codec:v libvpx -quality good -cpu-used 0 -b:v 225k -qmin 10 -qmax 42 -maxrate 300k -bufsize 1000k -threads 2 -vf scale="$scale:trunc(ow/a/2)*2" -codec:a libvorbis -b:a 128k -pass 2 -f webm "$output.webm"
		#Generate single image from selected frame of video (default is 1), scale and save as jpg
		ffmpeg -i "$input" -ss $frame -vframes 1 -vf scale="$scale:trunc(ow/a/2)*2" "$output.jpg"
	else
		echo "Scale factor not recognized.  Permissable options are <height> or <width>"
	fi
fi

Its been updated to avoid sizing errors by rounding the size for you. Its also been scripted to take parameters to automate the conversion based on parameters. Switched mp4 audio codec to mp3.