Video denoising is the process of removing noise from a video signal. Video denoising methods can be divided into:
- Spatial video denoising methods, where image noise reduction is applied to each frame individually.
- Temporal video denoising methods, where noise between frames is reduced. Motion compensation may be used to avoid ghosting artifacts when blending together pixels from several frames.
- Spatial-temporal video denoising methods use a combination of spatial and temporal denoising. This is often referred to as 3D denoising.[1]
It is done in two areas:
They are chroma and luminance, chroma noise is where one see color fluctuations and luminance is where one see light/dark fluctuations. Generally, the luminance noise looks more like film grain while chroma noise looks more unnatural or digital like.[2]
Video denoising methods are designed and tuned for specific types of noise.
Typical video noise types are following:
- Analog noise
- Radio channel artifacts
- High frequency interference (dots, short horizontal color lines, etc.)
- Brightness and color channel interference (problems with antenna)
- Video reduplication – false contouring appearance
- VHS artifacts
- Color-specific degradation
- Brightness and color channel interference (specific type for VHS)
- Chaotic line shift at the end of frame (lines resync signal misalignment)
- Wide horizontal noise strips (old VHS or obstruction of magnetic heads)
- Film artifacts (see also Film preservation)
- Digital noise
- Blocking – low bitrate artifacts
- Ringing – low and medium bitrates artifact especially on animated cartoons
- Blocks (slices) damage in case of losses in digital transmission channel or disk injury (scratches on DVD)
Different suppression methods are used to remove all these artifacts from video.