Human visual system model: Difference between revisions

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A '''human visual system model''' (HVS model) is used by [[image processing]], [[video processing]] and [[computer vision]] experts to deal with biological and psychological processes that are not yet fully understood. Such a model is used to simplify the behaviours of what is a very [[complex system]]. As our knowledge of the true [[visual system]] improves, the model is updated.

'''Psychovisual''' involvesstudy is the study of the psychology of vision.

The human visual system model can be used to produce desired effects in perception and vision. Examples of using an HVS model include [[color television]], [[lossy compression]], and [[Cathode-ray tube]] (CRT) television.

It is common to think of "taking advantage" of the HVS model to produce desired effects. Examples of taking advantage of an HVS model include colour television. Originally it was thought that colour television required too high a bandwidth for the then available technology. Then it was noticed that the colour resolution of the HVS was much lower than the brightness resolution; this allowed colour to be squeezed into the signal by [[chroma subsampling]]. Another example is image compression, like [[JPEG]]. Our HVS model says that we cannot see high frequency detail so in JPEG we can quantise these components without a perceptible loss of quality. Similar concepts are applied in [[Data compression#Lossy audio compression|audio compression]], where sound frequencies inaudible to humans are bandstop filtered.

Originally it was thought that colour television required too high a bandwidth for the then available technology. Then it was noticed that the colour resolution of the HVS was much lower than the brightness resolution; this allowed colour to be squeezed into the signal by [[chroma subsampling]].

It is common to think of "taking advantage" of the HVS model to produce desired effects. Examples of taking advantage of an HVS model include colour television. Originally it was thought that colour television required too high a bandwidth for the then available technology. Then it was noticed that the colour resolution of the HVS was much lower than the brightness resolution; this allowed colour to be squeezed into the signal by [[chroma subsampling]]. Another example is lossy image compression, like [[JPEG]]. Our HVS model says that we cannot see high frequency detail so in JPEG we can quantise these components without a perceptible loss of quality. Similar concepts are applied in [[Data compression#Lossy audio compression|audio compression]], where sound frequencies inaudible to humans are bandstop filtered.

Several HVS features are derived from evolution, when we needed to defend ourselves or hunt for food. We often see demonstrations of HVS features when we are looking at optical illusions.