Video denoising

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Video denoising is the process of removing noise from a video signal. Video denoising methods are divided into:

Spatial video denoising methods, when only one frame is used for noise suppression. Such methods are close to image noise reduction.
Temporal video denoising methods, when only temporal information is used. Such method can be divided into:
- Motion adaptive methods - some analysis of pixel motion detection is used. If there is no motion in some pixels - serious averaging with previous pixels are used. In case of motion more accurate averaging required to avoid "ghosting" artifacts.
- Motion compensative methods use motion estimation to predict and consider right pixel values from correct place from previous frame(s). This methods require bigger time, but produce better results.
Spatial-Temporal video denoising methods use a combination of spatial and temporal denoising.

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 channels interference (problems with antenna)
  - Video reduplication - false contouring appearance
- VHS artifacts
  - Colors specific degradation
  - Brightness and color channels interference (specific type for VHS)
  - Lines chaotic shift at the end of frame (lines recync signal disalignment)
  - Wide horizontal noise strips (old VHS or obstruction of magnetic heads)
- Film artifacts (see also Film preservation)
  - Dust, dirt, spray
  - Scratches
  - Curling (emulsion exfoliation)
  - Fingerprints
Digital noise
- Blocking - low bitrates artifact
- 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 disk)

Different suppression methods are used to remove all this artifacts from video.

See also