A video filter is a
software
Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications.
The history of software is closely tied to the development of digital comput ...
component that performs some operation on a multimedia
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...
.
Multiple filters can be used in a chain, known as a ''
filter graph'', in which each filter receives
input from its
upstream filter,
processes the input and outputs the processed video to its
downstream filter.
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With regards to
video encoding three categories of filters can be distinguished:
* prefilters: used before
encoding
In communications and Data processing, information processing, code is a system of rules to convert information—such as a letter (alphabet), letter, word, sound, image, or gesture—into another form, sometimes data compression, shortened or ...
* intrafilters: used while encoding (and are thus an integral part of a
video codec
A video codec is software or Computer hardware, hardware that data compression, compresses and Uncompressed video, decompresses digital video. In the context of video compression, ''codec'' is a portmanteau of ''encoder'' and ''decoder'', while ...
)
* postfilters: used after
decoding
Prefilters
Common ''prefilters'' include:
*
denoising
* resizing (
upsampling,
downsampling)
*
contrast enhancement
*
deinterlacing
Deinterlacing is the process of converting interlaced video into a non-interlaced or Progressive scan, progressive form. Interlaced video signals are commonly found in analog television, VHS, Laserdisc, digital television (HDTV) when in the 1080 ...
(used to convert
interlaced video
Interlaced video (also known as interlaced scan) is a technique for doubling the perceived frame rate of a video display without consuming extra Bandwidth (signal processing), bandwidth. The interlaced signal contains two field (video), fields ...
to
progressive video)
*
deflicking
Intrafilters
Common ''intrafilters'' include:
*
deblocking
Postfilters
Common ''postfilters'' include:
*
deinterlacing
Deinterlacing is the process of converting interlaced video into a non-interlaced or Progressive scan, progressive form. Interlaced video signals are commonly found in analog television, VHS, Laserdisc, digital television (HDTV) when in the 1080 ...
*
deblocking
*
deringing
See also
*
Filter graph
Notes
References
* Bovik, Al (ed.). ''Handbook of Image and Video Processing''. San Diego: Academic Press, 2000. .
*
Wang, Yao, Jörn Ostermann, and Ya-Qin Zhang. ''Video Processing and Communications''. Signal Processing Series. Upper Saddle River, N.J.: Prentice Hall, 2002. .
Video processing
Video signal
Television terminology
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