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The term post-processing (or postproc for short) is used in the video/film business for quality-improvement
image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimension ...
(specifically digital image processing) methods used in video playback devices, such as stand-alone DVD-Video players; video playing software; and transcoding software. It is also commonly used in real-time
3D rendering 3D rendering is the 3D computer graphics process of converting 3D models into 2D images on a computer. 3D renders may include photorealistic effects or non-photorealistic styles. Rendering methods Rendering is the final process of creati ...
(such as in video games) to add additional effects.


Uses in video production

Video post-processing is the process of changing the perceived quality of a video on playback (done after the decoding process). Image scaling routines such as linear interpolation,
bilinear interpolation In mathematics, bilinear interpolation is a method for interpolating functions of two variables (e.g., ''x'' and ''y'') using repeated linear interpolation. It is usually applied to functions sampled on a 2D rectilinear grid, though it can be ge ...
, or
cubic interpolation In numerical analysis, a cubic Hermite spline or cubic Hermite interpolator is a spline where each piece is a third-degree polynomial specified in Hermite form, that is, by its values and first derivatives at the end points of the correspondin ...
can for example be performed when increasing the size of images; this involves either subsampling (reducing or shrinking an image) or zooming (enlarging an image). This helps reduce or hide image artifacts and flaws in the original film material. It is important to understand that post-processing always involves a trade-off between speed, smoothness and sharpness. * Image scaling and
multivariate interpolation In numerical analysis, multivariate interpolation is interpolation on functions of more than one variable; when the variates are spatial coordinates, it is also known as spatial interpolation. The function to be interpolated is known at given po ...
: **
Nearest-neighbor interpolation Nearest-neighbor interpolation (also known as proximal interpolation or, in some contexts, point sampling) is a simple method of multivariate interpolation in one or more dimensions. Interpolation is the problem of approximating the value of ...
** linear interpolation **
bilinear interpolation In mathematics, bilinear interpolation is a method for interpolating functions of two variables (e.g., ''x'' and ''y'') using repeated linear interpolation. It is usually applied to functions sampled on a 2D rectilinear grid, though it can be ge ...
**
cubic interpolation In numerical analysis, a cubic Hermite spline or cubic Hermite interpolator is a spline where each piece is a third-degree polynomial specified in Hermite form, that is, by its values and first derivatives at the end points of the correspondin ...
**
bicubic interpolation In mathematics, bicubic interpolation is an extension of cubic interpolation (not to be confused with cubic spline interpolation, a method of applying cubic interpolation to a data set) for interpolating data points on a two-dimensional regula ...
**
Bézier surface Bézier surfaces are a species of mathematical spline used in computer graphics, computer-aided design, and finite element modeling. As with Bézier curves, a Bézier surface is defined by a set of control points. Similar to interpolation in m ...
**
Lanczos resampling filtering and Lanczos resampling are two applications of a mathematical formula. It can be used as a low-pass filter or used to smoothly interpolate the value of a digital signal between its samples. In the latter case it maps each sample of t ...
**
trilinear interpolation Trilinear interpolation is a method of multivariate interpolation on a 3-dimensional regular grid. It approximates the value of a function at an intermediate point (x, y, z) within the local axial rectangular prism linearly, using function data ...
** Tricubic interpolation * SPP (Statistical-Post-Processing) *
Deblocking A deblocking filter is a video filter applied to decoded compressed video to improve visual quality and prediction performance by smoothing the sharp edges which can form between macroblocks when block coding techniques are used. The filter aim ...
* Deringing * Sharpen / Unsharpen (often referred to as "soften") * Requantization * Luminance alterations * Blurring /
denoising Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an und ...
* Deinterlacing **weave deinterlace method **bob deinterlace method **linear deinterlace method **yadif deinterlace method * Deflicking * 2:3 pull-down /
ivtc Telecine ( or ) is the process of transferring film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process. Telecine enables a motion picture, captured originally on ...
( inverse telecine) for conversion from 24 frames/s and 23.976 frames/s to 30 frames/s and 29.97 frames/s * 3:2 pull-up ( telecine conversion) for conversion from 30 frames/s and 29.97 frames/s to 24 frames/s and 23.976 frames/s


Uses in 3D rendering

Additionally, post-processing is commonly used in
3D rendering 3D rendering is the 3D computer graphics process of converting 3D models into 2D images on a computer. 3D renders may include photorealistic effects or non-photorealistic styles. Rendering methods Rendering is the final process of creati ...
, especially for video games. Instead of rendering 3D objects directly to the display, the scene is first rendered to a buffer in the memory of the
video card A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer mon ...
.
Pixel shaders In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the rendering of a 3D scene - a process known as '' shading''. Shaders have evolved to perform a variety of ...
and optionally vertex shaders are then used to apply post-processing filters to the image buffer before displaying it to the screen. Some post-processing effects also require multiple-passes, gamma inputs, vertex manipulation, and depth buffer access. Post-processing allows effects to be used that require awareness of the entire image (since normally each 3D object is rendered in isolation). Such effects include: *
Ambient occlusion In 3D computer graphics, modeling, and animation, ambient occlusion is a shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting. For example, the interior of a tube is typically more occluded ...
(HBAO, Screen space ambient occlusion (SSAO, reflections), etc. * Anaglyph *
Anti-aliasing Anti-aliasing may refer to any of a number of techniques to combat the problems of aliasing in a sampled signal such as a digital image or digital audio recording. Specific topics in anti-aliasing include: * Anti-aliasing filter, a filter used be ...
(
FXAA Fast approximate anti-aliasing (FXAA) is a screen-space anti-aliasing algorithm created by Timothy Lottes at Nvidia. FXAA 3 is released under a public domain license. A later version, FXAA 3.11, is released under a 3-clause BSD license. Algor ...
, AGAA, SMAA,
MLAA Morphological antialiasing (MLAA) is a technique for minimizing the distortion artifacts known as aliasing when representing a high-resolution image at a lower resolution. Contrary to multisample anti-aliasing (MSAA), which does not work for def ...
, and custom anti-aliasing methods—not sample-size AA like MSAA and SSAA) * Bloom * Blur (
depth of field The depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera. Factors affecting depth of field For cameras that can only focus on one object dis ...
, motion blur, smart) * Bloodlust effect (red vignetting with particles, etc.) *
Bokeh In photography, bokeh ( or ; ) is the aesthetic quality of the blur produced in out-of-focus parts of an image. Bokeh has also been defined as "the way the lens renders out-of-focus points of light". Differences in lens aberrations and ...
*
Bump mapping Bump mapping is a texture mapping technique in computer graphics for simulating bumps and wrinkles on the surface of an object. This is achieved by perturbing the surface normals of the object and using the perturbed normal during lighting calcul ...
*
Cel shading Cel shading or toon shading is a type of non-photorealistic rendering designed to make 3-D computer graphics appear to be flat by using less shading color instead of a shade gradient or tints and shades. A cel shader is often used to mimic ...
*
Chromatic aberration In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wav ...
*
Color correction Color correction is a process used in stage lighting, photography, television, cinematography, and other disciplines, which uses color gels, or filters, to alter the overall color of the light. Typically the light color is measured on a scale kno ...
*
Color grading Color grading is a post-production process common to filmmaking and video editing of altering the appearance of an image for presentation in different environments on different devices. Various attributes of an image such as contrast, color, s ...
* Contrast adjustment ** Dynamic contrast *
Crepuscular rays Crepuscular rays are sunbeams that originate when the Sun is just below the horizon, during the twilight period. Crepuscular rays are noticeable when the contrast between light and dark is most obvious. Crepuscular comes from the Latin word , ...
* Digital camera light compensation *
Dithering Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often ...
(including subpixel) * Eye adaptation * Film grain * Filmic scene tone mapping * Fog/ mist * Gamma correction *
Global illumination Global illumination (GI), or indirect illumination, is a group of algorithms used in 3D computer graphics that are meant to add more realistic lighting to 3D scenes. Such algorithms take into account not only the light that comes directly from ...
* Glow * Grayscale * Haze (depth, heat) * High-dynamic-range rendering * Image distortion * Infrared * Lens flare (cubic lens distortion flare, pseudo lens flare) * Light scattering *
Nightvision Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vi ...
*
Outlines Outline or outlining may refer to: * Outline (list), a document summary, in hierarchical list format * Code folding, a method of hiding or collapsing code or text to see content in outline form * Outline drawing, a sketch depicting the outer edg ...
* Particle effects * Pixel vibrance * Point light
attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable at ...
*
Posterization Posterization or posterisation of an image is the conversion of a continuous gradation of tone to several regions of fewer tones, causing abrupt changes from one tone to another. This was originally done with photographic processes to create p ...
and deposterization *
Scanline A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube (CRT) display of a television set or computer monitor. On CRT screens the horizontal scan lines are visually discernible, ...
* Screen borders * Screen rotation * Shading (ink, paint, sketch) * Shadow mapping * Sepia tone * Sharpen/unsharpen (texture unsharp mask, LumaSharpen, sharpen, sharpen complex 1/2, adaptive-sharpen) *
Sobel operator The Sobel operator, sometimes called the Sobel–Feldman operator or Sobel filter, is used in image processing and computer vision, particularly within edge detection algorithms where it creates an image emphasising edges. It is named after I ...
*
Split screen Split screen may refer to: * Split screen (computing), dividing graphics into adjacent parts * Split screen (video production), the visible division of the screen * ''Split Screen'' (TV series), 1997–2001 * Split-Screen Level, a bug in the vid ...
* Upscaling (i.e. xBR, Super xBR, SuperRes) *
Texture filtering In computer graphics, texture filtering or texture smoothing is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels (pixels of the texture). There are two main categories of texture filterin ...
(point, linear, bilinear, trilinear, anisotropic, and custom algorithms) *
Vignette Vignette may refer to: * Vignette (entertainment), a sketch in a sketch comedy * Vignette (graphic design), decorative designs in books (originally in the form of leaves and vines) to separate sections or chapters * Vignette (literature), short, ...


See also

* Post-production * Pixel-art scaling algorithms


References


External links


Videotranscoding Wiki
-(documentation on server-side usage of MPlayer for transcoding) {{VideoProcessing Video processing