science

Video post-processing

Video post-processing is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Video post-processing rather than just read about it. In short: 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.

Key takeaways

Video post-processing belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Video post-processing to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Video post-processing from memory before moving on to harder problems.

Reference excerpt

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)

Worked examples

Example 1 — a first encounter with Video post-processing

Start with the simplest possible case. Write down what Video post-processing claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Video post-processing before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Video post-processing ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Video post-processing

In research: Video post-processing appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Video post-processing in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Video post-processing is common in secondary-school and first-year university syllabi. It links to neighbouring topics Video processing, so understanding it makes those chapters shorter.
In everyday life: Look for Video post-processing outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Video post-processing in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Video post-processing means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Video post-processing out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Video post-processing in simple terms?

Why does Video post-processing matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Video post-processing?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Video post-processing.