Video denoising is the process of removing noise

Noise

In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

 from a video

Video

Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...

 signal. Video denoising methods can be divided into:

• Spatial video denoising methods, where image noise reduction is applied to each frame
  Film frame
  In filmmaking, video production, animation, and related fields, a film frame or video frame is one of the many still images which compose the complete moving picture...
  
   individually.
• Temporal video denoising methods, where noise between frames is reduced. Motion compensation
  Motion compensation
  Motion compensation is an algorithmic technique employed in the encoding of video data for video compression, for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture...
  
   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.

Video denoising methods are designed and tuned for specific types of noise.
Typical video noise types are following:

• Analog
  Analog signal
  An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
  
   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
    VHS
    The Video Home System is a consumer-level analog recording videocassette standard developed by Victor Company of Japan ....
    
     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
    Film preservation
    thumb|300px|Stacked containers filled with reels of [[film stock]]The film preservation, or film restoration, movement is an ongoing project among film historians, archivists, museums, cinematheques, and non-profit organizations to rescue decaying film stock and preserve the images which they contain...
    
    )
    • Dust, dirt, spray
    • Scratch
      Scratch
      Scratch may refer to:* A mark or indentation on a surface: Abrasion It may also refer to:- Recordings :* Scratch , by Kaela Kimura* Scratch , the soundtrack to the 2001 documentary Scratch...
      
      es
    • Curling (emulsion exfoliation)
    • Fingerprint
      Fingerprint
      A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human hand. A print from the foot can also leave an impression of friction ridges...
      
      s
• Digital
  Digital
  A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
  
   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.