Reference

Video encoding glossary

194 terms with definitions, aliases, and cross-references to deep-dive articles. Search by name, filter by chapter, or jump straight to a letter.

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Inter-prediction

Predicting a block from blocks in previously decoded reference frames, exploiting temporal redundancy via motion vectors.

I

Intra-only coding

Coding where every frame is intra — like a sequence of still images. High bitrate, but each frame is independently editable.

I



Intra-prediction

Predicting a block from neighbouring already-decoded blocks in the same frame, exploiting spatial redundancy.

I

Judder

Visible motion jerkiness caused by mismatched frame rates between source and display (e.g. 24 fps cinema on a 60 Hz TV without pulldown).

J

kbps / Mbps

Units of bitrate — thousands and millions of bits per second. 1080p H.264 streaming sits around 4–8 Mbps; 4K HDR around 15–25 Mbps.

K

Keyframe

Informal term for an I-frame or IDR — a frame at which playback can start.

K

Lagrangian cost

J = D + λ·R — combined cost of distortion D and rate R, weighted by λ. The standard objective minimised by RDO.

L

LCEVC

Enhancement layer that sits on top of any base codec (H.264/HEVC/AV1), adding residual detail at higher resolution. Improves quality without changing the base bitstream.

L

Level

A named upper bound on resolution/bitrate/buffer that a decoder must support — e.g. H.264 Level 4.1 = 1080p30 @ ~10 Mbps.

L

libaom

The AOMedia reference AV1 encoder. Highest quality on slow presets, slowest of the AV1 encoders; benchmark baseline.

L

libvpx

Google's reference VP8/VP9 encoder. Was the YouTube workhorse for years; still common in WebRTC pipelines.

L

Lossless compression

Reconstructs the input bit-for-bit. Used in mastering and archive (FFV1, AVC-Intra). Compression ratios typically 2–4:1 — too low for streaming.

L



Lossy compression

Discards information the eye is unlikely to notice. All practical video delivery codecs (H.264, HEVC, AV1) are lossy.

L

Luma (Y')

The brightness component of a YCbCr pixel. Gamma-corrected (hence the prime). Carries most of the perceptual information.

L

Macroblock (MB)

The 16×16 coding unit of H.264 and earlier codecs. HEVC replaced it with the variable-sized CTU, AV1 with the superblock.

M

Main 10 profile

HEVC profile supporting 4:2:0 video up to 10-bit. Mandatory for HDR HEVC delivery and the default modern profile for streaming.

M

Masking (psychovisual)

The visual system's reduced sensitivity to errors in busy or moving regions. Used by encoders to allocate fewer bits there.

M

Mbps

Megabits per second. Standard unit for video bitrate at HD/UHD scale.

M

MKV / Matroska

Open and flexible container, popular for high-quality private libraries. Supports virtually any codec and many subtitle/audio tracks.

M

Mode decision

Selecting which prediction mode and block partition to use for each region of the frame — driven by RDO.

M

Moiré

An interference pattern produced when a fine repetitive pattern (fabric, fence) clashes with the pixel grid — a classic aliasing artifact.

M

MOS

Average subjective quality score (typically 1–5) given by a panel of viewers. The ground truth that every objective metric tries to approximate.

M

Motion blur

Smear of moving objects within one frame, caused by the camera shutter being open while the object moves. Critical to cinematic look.

M



Motion estimation

The encoder's search for the best-matching block in a reference frame. By far the most expensive step in encoding.

M



Motion vector

A 2D offset (often at sub-pixel precision) saying "this block looks like that block in the reference frame, shifted by (Δx, Δy)".

M

MOV

Apple's QuickTime container, the historical ancestor of MP4. Common in production pipelines (ProRes, DNxHR).

M



MP4

The dominant delivery container, built on ISO Base Media File Format. Used everywhere on the web; carries H.264/HEVC/AV1.

M



MPEG-2

1995 codec, the foundation of digital TV, DVB, ATSC and DVD. Replaced for delivery by H.264 but still alive in broadcast and DVB legacy.

M

MPEG-TS

Transport Stream container, originally for broadcast — small, packet-based, recoverable from packet loss. The legacy segment format for HLS.

M

MSE

Mean of squared per-pixel differences between source and encoded video. PSNR is just a logarithmic transform of MSE.

M

MS-SSIM

Multi-scale extension of SSIM, evaluating quality at several spatial resolutions. Standard in modern codec benchmarks.

M

Neural codec

A codec whose entire compression pipeline is a neural network, trained end-to-end. Promising on perceptual metrics; not yet practical for general delivery.

N

NVENC

NVIDIA's hardware video encoder, on every modern GeForce/Quadro/Tesla. Encodes H.264, HEVC and AV1 at multi-stream realtime speeds.

N

Nyquist–Shannon theorem

To represent a signal of bandwidth B without loss, sample it at ≥ 2B. Violating it causes aliasing — the root cause of moiré and stairstep artifacts.

N

Open GOP

GOP whose final B-frames reference the next GOP's I-frame. Slightly smaller; awkward for ABR segment boundaries.

O

Parallel encoding

Splitting encoding work across CPU cores, GPUs or machines — via tiles, slices, frame-parallel or chunked encoding.

P

Perceptual quantization

Adjusting quantization per region/frequency based on visual perception — quantize harder where the viewer won't notice (textures, motion).

P

Per-scene encoding

A more granular extension of per-title — different scenes inside one title get different bitrate/QP. Even bigger savings.

P

Per-title encoding

Custom bitrate ladder per video, based on its complexity. Pioneered by Netflix; saves 20–35 % bitrate at the same quality.

P



P-frame

A frame predicted from one or more previous frames. Much smaller than an I-frame, the workhorse of compression.

P



Pixel

The smallest addressable element of a digital image. Each pixel stores intensity and color, usually as three or four numeric components.

P

Pixel aspect ratio (PAR)

The shape of an individual pixel — square (1:1, default for most modern video) or non-square (legacy NTSC/PAL, anamorphic capture).

P

PlayReady

Microsoft's DRM, used on Edge, Xbox, smart TVs and many set-top boxes.

P



PQ (SMPTE ST 2084)

Absolute-luminance HDR transfer function up to 10 000 cd/m². Used by HDR10, HDR10+ and Dolby Vision. Display-referred, requires metadata.

P

Prediction

General term for "encoder's best guess for a block before coding the residual" — comes in intra and inter flavours.

P

Profile

A named subset of codec features required by a decoder, e.g. H.264 Baseline / Main / High, HEVC Main / Main10.

P



Progressive scan

Modern scan mode where each frame is transmitted as one complete image. Default for streaming, web, gaming and most production.

P

ProRes

Apple's intra-only production codec. High bitrate, fast decode, great for editing — not for delivery.

P