The term post-processing (or postproc for short) is used in the video/film business for quality-improvement image processing (specifically

digital image processing Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allo ...

) methods used in video playback devices, such as stand-alone DVD-Video players; video playing software; and

transcoding Transcoding is the direct digital-to-digital conversion of one encoding to another, such as for video data files, audio files (e.g., MP3, WAV), or character encoding (e.g., UTF-8, ISO/IEC 8859). This is usually done in cases where a target d ...

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 game Video games, also known as computer games, are electronic games that involves interaction with a user interface or input device such as a joystick, controller, keyboard, or motion sensing device to generate visual feedback. This fee ...

s) 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 In computer graphics and digital imaging, image scaling refers to the resizing of a digital image. In video technology, the magnification of digital material is known as upscaling or resolution enhancement. When scaling a vector graphic image ...

routines such as

linear interpolation In mathematics, linear interpolation is a method of curve fitting using linear polynomials to construct new data points within the range of a discrete set of known data points. Linear interpolation between two known points If the two known poi ...

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 ...

, or cubic interpolation 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. *

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 poi ...

: ** Nearest-neighbor interpolation **

** cubic interpolation ** bicubic interpolation **

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 man ...

** Lanczos resampling **

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 * Deringing * Sharpen / Unsharpen (often referred to as "soften") * Requantization * Luminance alterations * Blurring / denoising *

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, digital television (HDTV) when in the 1080i format, some D ...

**weave deinterlace method **bob deinterlace method **linear deinterlace method **yadif deinterlace method * Deflicking * 2:3 pull-down / ivtc (

inverse telecine 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 fi ...

) 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 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 fi ...

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

, 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 mo ...

. Pixel shaders 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 Spatial anti-aliasing, 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 ...

, 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,

motion blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...

, 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 cal ...

* Cel shading *

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 w ...

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 * 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 Film grain or granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain i ...

* Filmic scene tone mapping * Fog/ mist *

Gamma correction Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression: : V_\tex ...

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 fro ...

* Glow *

Grayscale In digital photography, computer-generated imagery, and colorimetry, a grayscale image is one in which the value of each pixel is a single sample representing only an ''amount'' of light; that is, it carries only intensity information. Graysc ...

* Haze (depth,

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

) *

High-dynamic-range rendering High-dynamic-range rendering (HDRR or HDR rendering), also known as high-dynamic-range lighting, is the rendering of computer graphics scenes by using lighting calculations done in high dynamic range (HDR). This allows preservation of details tha ...

Image distortion In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image. It is a form of optical aberration. Radial distortion Although distortion can be irreg ...

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

Lens flare A lens flare happens when light is scattered or flared in a lens system, often in response to a bright light, producing a sometimes undesirable artifact in the image. This happens through light scattered by the imaging mechanism itself, for ex ...

(cubic lens distortion flare, pseudo lens flare) *

Light scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...

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 v ...

* Outlines *

Particle effects A particle system is a technique in game physics, motion graphics, and computer graphics that uses many minute sprites, 3D models, or other graphic objects to simulate certain kinds of "fuzzy" phenomena, which are otherwise very hard to repro ...

* 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 variabl ...

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 Shading refers to the depiction of depth perception in 3D models (within the field of 3D computer graphics) or illustrations (in visual art) by varying the level of darkness. Shading tries to approximate local behavior of light on the ob ...

(ink, paint, sketch) *

Shadow mapping Shadow mapping or shadowing projection is a process by which shadows are added to 3D computer graphics. This concept was introduced by Lance Williams in 1978, in a paper entitled "Casting curved shadows on curved surfaces." Since then, it has b ...

Sepia tone In photography, toning is a method of altering the color of black-and-white photographs. In analog photography, it is a chemical process carried out on metal salt-based prints, such as silver prints, iron-based prints (cyanotype or Van Dyke br ...

* Sharpen/unsharpen (texture unsharp mask, LumaSharpen, sharpen, sharpen complex 1/2, adaptive-sharpen) * Sobel operator * Split screen * 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 filtering ...

(point, linear, bilinear, trilinear, anisotropic, and custom algorithms) * Vignette

References

External links

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

Uses in video production

Uses in 3D rendering

See also

References

External links