What is a codec? Audio and video codecs, explained

Vittorio is a long time video hacker and member of several multimedia open source communities. He has always been interested in video quality preservation and color conversion, and has shared this knowledge in several conferences around the world. His work as Lead of Video Encoding at Vimeo ensures videos are encoded at the best possible quality.
Vittorio Giovara
What the heck is a codec, anyway? Vimeo’s video encoding lead Vittorio Giovara answers all of your burning questions.

As we all spend more and more of our time online (and you know, watching videos), it’s crucial that the videos you upload and stream are the highest quality they can be. We’re passionate about bringing the best tech to our users and their audiences around the world. That's why we’re rolling out a new audio codec called Opus to improve the audio quality of your videos.

Over the years, Vimeo has adopted many new codecs in the name of getting you the best audio-visual experience. But what exactly is a codec and why do they matter? Our video encoding team lead Vittorio Giovara is here to break it down.

What does “codec” mean?

“Codec is short for COder-DEcoder. It’s the set of rules that define how images or sounds are converted into data, compressed to take as little space as possible, and vice versa.

The process that compresses data is called an 'encoder.' They usually work by finding similarly repeating patterns of a video or audio stream and compressing them away.

On the other end of the pipes, a 'decoder' works to decode data. (Shocker!) A decoder just applies the opposite process that receives data and produces audible or visible content. These need to be fast and make sure that all data is rendered correctly.

A recent Staff Pick video actually explains codecs better than I ever could. (And it’s already playing with Opus audio!)”

Why are codecs important?

“Codecs have become a vital and central element of internet streaming and broadcasting because they are the only way for users to access content online. Over the years, they’ve become more and more powerful, allowing us to deliver higher quality at a lower bandwidth.

But they've also become more complex to produce and deploy. When choosing a 'next-generation codec,' one needs to take into consideration that it will be hard to change that decision in the future.”

What codecs does Vimeo support now?

Video codecs:

“For video, we use the H264 codec. Every upload on Vimeo receives a complete set of profiles with this codec to guarantee maximum compatibility with any device at a reasonably high quality.

Then, in order to serve HDR content, we use HEVC (which stands for High-Efficiency Video Coding) to make sure your video looks its best and is compatible with HDR devices. Finally, we support the very fancy AV1. We pioneered AV1 in the summer of 2019 to encode our Staff Picks with.”

Audio codecs:

"We use AAC (Advanced Audio Codec), which is also one of the most supported codecs on the web. And, of course, Opus.”

What is an example of a codec?

A "codec" is short for "coder-decoder" and is a set of rules that define how images or sounds are converted to digital. Codecs like AV1 and Opus are high-quality, open codecs that are royalty-free and allow the best experience for our users.

So what is Opus, exactly?

"Opus is a recently developed audio codec that blows every other audio codec out of the water. While it’s not the first open and free audio codec, it is the first one with wide adoption and enough performance to warrant its use.

It was originally developed by the Xiph Foundation and several other companies, combining two different algorithms called CELT and SILK that work well in different scenarios. (You can learn more about the technical work and the history behind this codec here.)”

Why does Vimeo use AV1 and Opus codecs?

“On the open web, we need to ensure compatibility with millions of devices. That includes making sure that users can actually consume the content without strings attached, at the best possible quality.

Because of this, we favor open codecs like AV1 and Opus. Users deserve accessible, inclusive, highly performant means of communication. These royalty-free codecs level the field and allow everybody to build great experiences and services on Vimeo.”

If you are a creator yourself, you may want to explore how Vimeo can help you make, share, and manage videos. Learn more about features like video hosting, our text-based video editor, timeline editor, video graphics, image to video converter, and more.

Your Vimeo viewing experience just got a major boost, no user action required."
Vittorio Giovara, Vimeo's video encoding team lead

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