Downgrading Files for a Road Trip

Published: 2023-12-23 10:00 AM

Category: Technology | Tags: videos, files, dvd, movies

We have a trip to Kentucky coming up and for the first time in a while, we don't have a general-purpose iPad to use for some in-car entertainment. My wife and I used to say that we wouldn't rely on movies to get through trips because "we didn't do that growing up." But, people also used to take three weeks to ride across the country on horses and now we have airplanes.

I have a small collection of movies on flash drive, so we went to the local library (I love our library) and grabbed an in-car DVD player from their wonderful Library of Things which also had an option for SD or USB playback. I eagerly grabbed my flash drive and was met with "encoding not readable."

Turns out that this particular device only accepts MPEG1, MPEG2, or DivX. h.264 encodings would not work because it's old-ish. I also learned that most DVDs are encoded in MPEG2, so it makes sense that storage media would need to be in the same format.

It might be once or twice a year that I really need FFMpeg and it never fails to come through. It also seems that this is a common question and there are pages and pages of debate about what bitrate is best for which format - this turned into a three-hour deep dive and semi-live toot thread while I wrestled not only with encoding and wrapper formats but also max resolution (this particular device exptected a max of 720x576 pixels).

In the end I landed on this command:

ffmpeg -i file.mp4 -c:v libxvid -q:v 2 -q:a 2 -vf scale=720:-1 out.avi

This line does 4 things:

1. Take the input mp4 and convert it to the DivX encoding
2. Drop video and audio quality just a bit
3. Scale the video to a max of 720 pixels wide while keeping the height in proportion
4. Spit out a .avi file container the player can read

I'm running this all on a Chromebook, so encoding takes about the same amount of time it takes to watch the movie, so I'm pretty much keeping the computer open and running while we do other things around the house to get ready.

I am also acutely aware that I could run to the thrift store and get the same movies on DVD for $1 each and be set. But that's a much less interesting blog post.