How Codecs Work (Video)

Codecs don’t need to be hard. No, really, they don’t.

By the end of this article, you will be able to pick the best codec for you on each project. My goal is to empower you to make your own informed decisions about codecs, instead of relying on what worked for someone else.

I’m going to walk you through every step in the process of making a video. Click on a heading to jump to that section. I’ll cover:

At each stage, I’ll explain which factors you should be considering as you choose a codec, and I’ll give you some examples of the most commonly-used codecs for that stage.

Along the way, we’ll cover why low-end codecs and high-end codecs can each slow down your editing, the reasons for a proxy/offline edit, a real-world project walkthrough, some storage-saving strategies, and an explanation for why transcoding cannot improve your image quality.

The benefits of optimizing your codecs can be huge. The right codec will preserve your images in the highest quality, help you work faster, and it will also enable you to take the best advantage of your computer and storage. You’ll be able to work faster on a laptop than many can on a high-end tower.

What a Codec Does

A codec is a method for making video files smaller, usually by carefully throwing away data that we probably don’t really need, and they’re pretty smart about how they do that. A few years ago, I created a video that covers the main compression techniques that many codecs use. It’s not required viewing to understand this article, but it certainly won’t hurt.

If you’re skipping the video, here are some very basic explanations:

  • Chroma subsampling: Throws away some color data (4:4:4 is no chroma sampling. 4:2:2 is some chroma subsampling.4:2:0 is lots of chroma subsampling). Bad if you’re doing color-correction. Really bad if you’re doing green screen or VFX work.
  • Macro-Blocking: Finds blocks (varying size) of similar colors and makes them all the same color. Bad for VFX and color-correction. Almost all codecs use this to some degree, and the amount tends to vary with the bitrate.
  • Temporal compression: Uses previous frames (and sometimes following frames) to calculate the current frame. Bad for editing.
  • Bit depth: The number of possible colors. Deeper bit-depth (larger numbers) is good for color-correction and VFX.