• Source: Video post-processing

The term post-processing (or postproc for short) is used in the video and film industry for quality-improvement image processing (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 (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, 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. Post-processing always involves a trade-off between speed, smoothness and sharpness.

Image scaling and multivariate interpolation:
Nearest-neighbor interpolation
linear interpolation
bilinear interpolation
cubic interpolation
bicubic interpolation
Bézier surface
Lanczos resampling
trilinear interpolation
Tricubic interpolation
SPP (Statistical-Post-Processing)
Deblocking
Deringing
Sharpen / Unsharpen (often referred to as "soften")
Requantization
Luminance alterations
Blurring / denoising
Deinterlacing
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 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, 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. 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, motion blur, smart)
Bloodlust effect (red vignetting with particles, etc.)
Bokeh
Bump mapping
Cel shading
Chromatic aberration
Color correction
Color grading
Contrast adjustment
Dynamic contrast
Crepuscular rays
Digital camera light compensation
Dithering (including subpixel)
Eye adaptation
Film grain
Filmic scene tone mapping
Fog/mist
Gamma correction
Global illumination
Glow
Grayscale
Haze (depth, heat)
High-dynamic-range rendering
Image distortion
Infrared
Lens flare (cubic lens distortion flare, pseudo lens flare)
Light scattering
Nightvision
Outlines
Particle effects
Pixel vibrance
Point-light attenuation
Posterization and deposterization
Scanline
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
Split screen
Upscaling (i.e. xBR, Super xBR, SuperRes)
Texture filtering (point, linear, bilinear, trilinear, anisotropic, and custom algorithms)
Vignette




See also


Post-production
Pixel-art scaling algorithms




References






External links


Videotranscoding Wiki -(documentation on server-side usage of MPlayer for transcoding)

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