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Understanding Codecs – And Why They Are Important

A Codec (Compressor/Decompressor) is a mathematical algorithm that converts reality (sound and light) into binary numbers that can be stored in a computer; that’s the “Compressor” part. Then, it converts all those binary numbers back into images and sound that we can see and hear; that’s the “Decompressor” part.

Codecs exist for still images, audio and video files. Popular still image codecs include:

  • TIFF
  • PNG
  • JPG/JPEG
  • GIF

Popular audio codecs include:

  • WAV
  • AIF/AIFF
  • MP3
  • AAC

Popular video codecs include:

  • ProRes (in all its formats)
  • DNxHD (in all its formats)
  • CineForm (yup, in all its formats, too)
  • R3D
  • H.264/H.265

NOTE: Some formats, like QuickTime, MXF and MPEG-4, are not actual codecs, but containers that hold a variety of different codecs. For example, a QuickTime movie can hold a video file using the H.264 codec and an audio file using the AIF format.

In the past, I used to enjoy keeping track of how many audio and video codecs there were. But, frankly, I gave up when the number shot past 400. While the industry is not generating as many codecs as it was in the heyday of converting from SD to HD, not a month goes by that some manufacturer or developer is not announcing some new codec.

It is safe to say that there are “a lot!”

NOTE: As a sidelight, codecs are often divided into “lossy” and “lossless.” A lossless codec preserves all the original image quality so that when an image is restored it is indistinguishable from the original. RAW high-bit-depth files are examples of a mostly “lossless” codec. (I don’t think there is a perfectly lossless video codec; the files are just too big.)

A lossy codec “throws out” visual information as part of the compression process, which means that the compressed image does not have the original quality of the source. Virtually all video codecs are lossy to some degree, however the amount of loss varies by codec.

ONE MORE CORE CONCEPT

This one is really important: All media, in order to be stored on a digital device, must use a codec. Even more important, all media stored on a digital device must be compressed.

Some video, like that shot on an iPhone is significantly compressed. Other video, like that shot on a RED or high-end Arri camera is compressed, but not to the same degree.

The reason for all this compression is that video files are HUGE and engineers are always looking for ways to make them smaller without sacrificing too much quality. For example, a single 1080p frame in a theoretical “uncompressed” format can, depending upon bit depth, exceed 100 MB! This would require 3 GB PER SECOND to play back a 30 fps sequence!! As resolutions expand, these numbers only get worse.

Without compression, we could not edit video on our computers.

By Larry

Read more at larryjordan.com

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