Tag Archives: video size

Reducing size of video files via CLI.

Published / by Andrew

(TL;DR: Conversion script is at the end of this post.)

When it comes to video entertainment, I much prefer local media to streaming services, because I like being able to manage as much as I can using Kodi. (I used to use Kodi with an Android TV box, but now I have a laptop hooked up to my TV, but that’s a story for another day.)

But, using local media presents a problem– Space management. Unless I want to keep getting more and bigger hard drives (and I don’t), I have to figure out how to shrink down the video files without losing so much quality that I render them unwatchable. I also want to make these conversions via CLI so that I can do it over SSH.

I developed a small script that converts all files in a directory (not recursively, just because I didn’t want to do it that way) into smaller files. It uses BASH (with which I have a love/hate relationship) and FFMPEG (with which I have a hate/hate relationship). This changes the constant rate factor, changes the video and audio codecs, and reduces the resolution to 540×360 for widescreen and 540xWhatever for 4:3 (too lazy to math right now). I also toyed with changing the framerate, but reducing that made a pretty small change in filesize with a big change in video quality, though it may be worth it if you have a 60fps video.

As it currently stands, this reduces filesize by half for my current files, but that will depend on the source files.

This uses the version of FFMPEG that comes with Ubuntu 16.04 (I haven’t upgraded to 18.04 yet).

Some useful commands when checking the results are:

du -sh filepath     # Shows amount of space a directory or file
mediainfo filepath  # Shows information about a media file, but requires
                    # installing mediainfo from repos.

I’d kind of like to source where I found all of this information, but the script below is a Frankenstein’s monster using organs scattered all across the web.

You’ll want to update the inputDir and newDir variables whenever you run this, or you can modify to use ${1} and ${2}, which I may do for myself in the near future. You do not need to escape spaces, though. (And be aware that this will take awhile if you’re running it on a large directory.) You’ll also want to put this script one directory above the directory that you want to convert, and make an empty directory for the target directory.

newDir="Jontron Reduced" # Make sure this exists in the same directory as inputDir.

cd "${inputDir}"

shopt -s globstar # I have no idea what this does, but the script doesn't work if it's not run.

for file in **/*; do
    ffmpeg -i "$file" -c:v libx264 -crf 24 -b:v 1M -c:a aac -filter:v scale=540:-1 ../"${newDir}"/"${file}"