webmize.sh

#!/bin/bash
# save this as webmize.sh and make it executable. Put it somewhere in $PATH, such as in /usr/local/bin
# syntax: webmize.sh /path/to/sourcefile.mkv /path/to/targetfile.webm
sourcefile=$1
targetfile=$2
echo -e "Webmize v. 0.1. \n Start time? Format: xx:xx:xx"
read start
echo "End time? Format: 00:00:00"
read end
startsec=$(date -u -d "$start" +"%s")
endsec=$(date -u -d "$end" +"%s")
duration=$(date -u -d "0 $endsec sec - $startsec sec" +"%H:%M:%S")
durationsec=$(($endsec-$startsec))
echo "Audio? [Y/n]"
read audio
echo "Target size in MB?"
read targetsize
if [ -a $targetsize ]; then
        bitrate=1
    else
        # tweak the coefficient up or down from 10 to tune this until you get output files as close as possible to your target size. 10 tends to lowball a bit, which makes it easier to avoid hitting the filesize limit.
        bitrate=$(echo "scale=2; ($targetsize/$durationsec)*10" | bc)
fi
echo "$bitrate"M
if [ "$audio" == "n" ]; then
        echo "Encoding without audio"
ffmpeg -i "$sourcefile" -qmin 0 -qmax 50 -threads 4 -c:v libvpx -crf 8 -b:v "$bitrate"M -ss "$start" -an -sn -t "$duration" "$targetfile"
    else
        echo "Encoding with audio."
ffmpeg -i "$sourcefile" -qmin 0 -qmax 50 -threads 4 -c:v libvpx -crf 8 -b:v "$bitrate"M -ss "$start" -sn -t "$duration" "$targetfile"
fi
exit