Transform coding
Transform coding changes data into a form where important and less-important detail can be handled separately.
What it is
Transform coding is a compression approach where a signal is converted from one representation to another. For media, that often means moving from samples or pixels into frequency-like components.
Why transform?
Raw samples are not always the easiest way to compress sound or images. A transform can concentrate energy into fewer values and reveal parts that are less important to human perception.
How media codecs use it
Audio codecs use frequency-domain ideas to decide which sounds are easier to mask or less important to keep. Image and video codecs use block transforms and prediction so that visual detail can be stored more efficiently.
Why it helps lossy compression
Lossy codecs usually do not delete random data. They try to spend bits where humans are more likely to notice. Transform coding helps separate detail into components, making that decision more practical.