- COmpression/DECompression or Write/Read
A Codec is a language of efficiency
This is much like a language. A computer must “learn” the language before it can read or write it.
some languages or codecs, much like shorthand, can write more efficently and therefore maintain quality while keeping the size lower.
Bit rate decribes how much information there is per second in a stream of data. The important thing to understand is that the higher the bit rate, the more information, and thus the more effort it takes to decode that information, and the more space the file requires.
Bit rate is measured in how many bits(computer data) is delevired per second. Often this will be measure in Megabit per second.
Files with specific codecs will have a specific bit rate. Typically the higher the bit rate the highter the quaility wil be. These charts can be found online for the specific codecs.
A video shot in ProRes 422 1920*1080 at 24 fps has a bit rate of 117 Mbps.
Most people in the U.S have internet connections which can only handle up to 15-35 Mbps. Therefore video has to be compressed for the internet.
The goal of compression is to get the file size as small as possible while retaining visual and audio quality.
Psychoacoustic Audio Compression: All forms of compressed audio use powerfull algorithems to discard audio information that we can can’t hear.
Psychovisual Video compression: P.V. compression is similar to its audio counterpart. Instead of discarding audio that we can’t hear, psychovisual models discard data that our eys don’t need.
Changes to video and/or audio: Encoding (or compressing): Making a file smaller by removing(hopefully) redundant information (such as color).
Transcoding: Converting a file from one codec to another.
Styles of Compression:
I-Frame (or Intra-frame): A method of compression where each frame is compressed indvidually. Yields excellent image quality. Very Large file sizes. Best format for editing. ProRes and DNX are I-Frame Codex.
GOP( or Inter-frame): A method of compression where groups of frames are compressed together. Yields good image quality with very small file sizes. Best for Web Videos. H.264 & AVC are GOP Codecs.