The term post-processing (or postproc for short) is used in the video and film industry for quality-improvement

image processing An image or picture is a visual representation. An image can be two-dimensional, such as a drawing, painting, or photograph, or three-dimensional, such as a carving or sculpture. Images may be displayed through other media, including a pr ...

(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 DVD-Video is a consumer video format used to store digital video on DVDs. DVD-Video was the dominant consumer home video format in most of the world in the 2000s. As of 2024, it competes with the high-definition Blu-ray Disc, while both rece ...

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 ...

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 A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...

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 po ...

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. Post-processing always involves a trade-off between speed, smoothness and sharpness. *

and

multivariate interpolation In numerical analysis, multivariate interpolation or multidimensional interpolation is interpolation on ''multivariate functions'', having more than one variable or defined over a multi-dimensional domain. A common special case is bivariate inter ...

: ** Nearest-neighbor interpolation **

bicubic interpolation In mathematics, bicubic interpolation is an extension of cubic spline interpolation (a method of applying cubic interpolation to a data set) for interpolating data points on a two-dimensional regular grid. The interpolated surface (meaning the k ...

Bézier surface Bézier surfaces are a type 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 many ...

Lanczos resampling Lanczos filtering and Lanczos resampling are two applications of a certain 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 ...

trilinear interpolation Trilinear interpolation is a method of multivariate interpolation on a Three dimensional space, 3-dimensional regular grid. It approximates the value of a function at an intermediate point (x, y, z) within the local axial rectangular prism (geo ...

Tricubic interpolation In the mathematical subfield numerical analysis, tricubic interpolation is a method for obtaining values at arbitrary points in Three-dimensional space, 3D space of a function defined on a regular grid. The approach involves approximating the fun ...

* 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, VHS, Laserdisc, digital television (HDTV) when in the 1080 ...

** weave deinterlace method ** bob deinterlace method ** linear deinterlace method ** yadif deinterlace method * Deflicking * 2:3 pull-down / ivtc ( 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 Telecine ( or ), or TK, 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 this post-production process. Telecine enables a motion picture, captured origi ...

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 accelerator, graphics adapter, VGA card/VGA, video adapter, display adapter, or colloquially GPU) is a computer expansion card that generates a feed of graphics output to a displa ...

. 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 (HBAO, Screen space ambient occlusion (SSAO, reflections), etc. * Anaglyph * Anti-aliasing ( FXAA, AGAA, SMAA, MLAA, 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 farthest objects that are in acceptably sharp focus (optics), focus in an image captured with a camera. See also the closely related depth of focus. Factors affecting depth ...

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 l ...

, smart) * Bloodlust effect (red vignetting with particles, etc.) * Bokeh * Bump mapping * Cel shading *

Chromatic aberration In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the ...

* Color correction *

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 (vision), ...

* Contrast adjustment ** Dynamic contrast * Crepuscular rays * Digital camera light compensation * Dithering (including subpixel) * Eye adaptation * Film grain * Filmic scene tone mapping * Fog/

mist Mist is a phenomenon caused by small droplets of water suspended in the cold air, usually by condensation. Physically, it is an example of a Dispersion (chemistry), dispersion. It is most commonly seen where water vapor in warm, moist air meets ...

Gamma correction Gamma correction or gamma is a Nonlinearity, nonlinear operation used to encode and decode Relative luminance, luminance or CIE 1931 color space#Tristimulus values, tristimulus values in video or still image systems. Gamma correction is, in the s ...

* Global illumination * Glow *

Grayscale In digital photography, computer-generated imagery, and colorimetry, a greyscale (more common in Commonwealth English) or grayscale (more common in American English) image is one in which the value of each pixel is a single sample (signal), s ...

* Haze (depth,

heat In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by such mechanisms as thermal conduction, electromagnetic radiation, and friction, which are microscopic in nature, involving sub-atomic, ato ...

) * High-dynamic-range rendering * Image distortion *

Infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

* Lens flare (cubic lens distortion flare, pseudo lens flare) *

Light scattering In physics, scattering is 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 particles and radia ...

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 luminous intensity, intensity range. Humans h ...

* Outlines * Particle effects * Pixel vibrance * Point-light

attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a Transmission medium, medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and ...

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 ...

and deposterization * Scanline * Screen borders * Screen rotation * Shading (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 ...

* 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 mapping, texture mapped pixel, using the colors of nearby Texel (graphics), texels (ie. pixels of the 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