Video Compression Terminology Explained

ErminiaFiorino
Monday, November 25, 2019 08:10

Video Compression Terminology Explained

It’s easy to get bogged down in all the technical terminology when it comes to chatting about the wizardry behind the lenses of TV shows and movies. Lossy this, frame rate that — after a while, trying to understand the differences can be confusing, especially if you’re new to the industry.  When applied to video compression, that terminology gets even more complicated. If you’re one of those people scratching your head at the technical terms, we’ve got you covered.

Below is a glossary breaking down basic video compression phrases, so next time you can hop into those technical discussions with ease.

Video Compression Terminology Explained

Video Compression Terminology Explained

It’s easy to get bogged down in all the technical terminology when it comes to chatting about the wizardry behind the lenses of TV shows and movies. Lossy this, frame rate that — after a while, trying to understand the differences can be confusing, especially if you’re new to the industry.  When applied to video compression, that terminology gets even more complicated. If you’re one of those people scratching your head at the technical terms, we’ve got you covered.

Below is a glossary breaking down basic video compression phrases, so next time you can hop into those technical discussions with ease.

Video Compression Terminology Explained

Codec

With the advent of ultra-high-def and wide-color-gamut, video file sizes are much larger than ever before. To offer faster transportation of data and a seamless playback experience, file types must be made smaller. That’s where codecs come in.

The word “codec” is a combination of two terms: coder and decoder (co/dec). It refers to a device or software that encodes data (usually compressing it for storage), then decodes (or decompresses) that data for playback or editing.

There are several different types of codecs in the industry — some are royalty-free, while others require licensing. The most common types of codecs are:

HEVC
AV1
VVC
VP9

Each has pros and cons, so the ultimate determining factor on which one to use depends on what’s needed for a specific project.

Containers

Containers, also known as “formats,” refer to how something is stored (not how something is coded). They contain all the compressed metadata — audio and video — that was encoded using a codec, and are represented by different file extensions (i.e. .MP4, .MOV, etc).

To help put it into perspective, an article by api.video offers a great analogy:

Imagine a shipping container filled with packages of many types. In this analogy, the shipping container is the format, and the codec is the tool that creates the packages and places them in the container.

Containers are responsible for the “packaging, transport, and presentation” of the information.

Frame Rate

The frame rate is the number of video frames displayed in a single second. The more frames shown per second — or the higher the number — the more realistic the visual quality is. High frame rates look best with sporting events or action-based visuals. On the other hand, the lower the number, the more “cinematic” a video feels.

Bit Rate

Generally measured in kilobits per second (Kbps) or megabits per second (Mbps), the bit rate is the amount of data a file uses per second to store audio-visual information. A higher bit rate contains more data, which means it takes more power to process and requires a faster internet connection for playback. In general, a higher bit rate also means better quality files.

Lossy Compression

Lossy compression is one of two main types of compression formats. It reduces file sizes by permanently deleting unnoticeable data — usually redundant information. This process allows for increased storage space for additional file types, however, once done the data cannot be restored in its original form.

Lossless Compression

Lossless compression is the other main type of compression format. With lossless compression, the technique minimizes the file size without losing quality — data is “rewritten in the same manner as the original file.” While the file size reduction is less than lossy, original data can be recovered if necessary.

While there are many terms out there, understanding these basic phrases will help lay the foundation for the more complicated industry jargon to come.

Interested in diving deeper into all things video compression? Take a look at the November/December SMPTE Motion Imaging Journal!