Video encoding glossary — 194 terms with definitions

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DASH

MPEG's HTTP-based adaptive streaming protocol. Codec-agnostic; deeper coverage in the Streaming KB.

DCI-P3

Wide-gamut color space designed for digital cinema. Wider than BT.709 but narrower than BT.2020; also used by Apple displays.

DCT

Transform that concentrates a block's energy into a few low-frequency coefficients, making compression dramatically more efficient.

Deblocking filter

In-loop filter that smooths block boundaries to hide blocking artifacts introduced by quantization.

Decoder

Software or hardware that reconstructs frames from an encoded bitstream. Compliant decoders are deterministic; quality variation lives on the encoder side.

Deinterlacing

The process of converting interlaced fields back into progressive frames, often using motion-adaptive or motion-compensated algorithms.

Digital video

A sequence of still images (frames) captured and stored as discrete pixel values, displayed fast enough to produce the illusion of motion.

Distortion

A measure of how much the encoded signal differs from the source. The "D" in rate-distortion theory.

Dithering

Adding controlled noise to a low-bit-depth signal to break visible banding into less objectionable noise. Used both at encode and decode time.

DNxHR / DNxHD

Avid's intra-only production codec family — counterpart to ProRes, common in broadcast and Avid Media Composer workflows.

Dolby Vision

Dolby's HDR system with dynamic per-frame/per-scene metadata and up to 12-bit signal. Licensed; ubiquitous on premium streaming (Netflix, Apple TV+, Disney+).

DPB (Decoded Picture Buffer)

The set of reference frames the decoder keeps in memory for future prediction. Profiles cap the DPB size.

DRM

A system that controls who can play what and how. In streaming, three big providers — Widevine (Google), FairPlay (Apple), PlayReady (Microsoft).

DSCQS

A subjective-testing protocol where viewers compare reference and test clips side by side on a continuous scale.

Dynamic HDR metadata

Tone-mapping instructions that change per scene or per frame, enabling brighter/darker scenes to be re-mapped optimally for each display.

Encoder

Software or hardware that turns raw video into a compliant bitstream of a chosen codec. Different encoders for the same codec vary widely in speed and quality.

End-to-end learned compression

Joint optimisation of analysis, transform, quantization and entropy steps by gradient descent. The research frontier of video coding.

Enhancement layer

An extra coded stream that augments a base layer with more detail or resolution. LCEVC is the canonical example.

Entropy coding

Lossless final coding stage — turns the stream of quantized coefficients and syntax elements into the smallest possible bit sequence.

Entropy (information)

A measure of the average information content of a source — the lower bound any lossless coder can reach.

EOTF

The display-side transfer function — maps code values to emitted light. PQ EOTF defines how HDR code 1023 becomes 10 000 cd/m².

FairPlay

Apple's DRM, used on iOS, tvOS and Safari. Mandatory for HEVC content on Apple devices.

FFmpeg

The de-facto Swiss-army-knife CLI/library for everything video — decode, filter, encode, mux. Every encoding pipeline touches it.

FFV1

Open-source lossless intra-only codec, used for digital film preservation (FIAF) and broadcast archives.

Field (interlaced)

Half a frame in interlaced video — either the odd or the even scan lines, captured at slightly different moments in time.

Fragmented MP4 (fMP4)

MP4 split into independent fragments — the foundation of CMAF and modern HLS/DASH streaming.

Frame

A single still image inside a video sequence. Modern delivery is progressive, so one frame is one complete image.

Frame rate

How many frames per second a video plays at. Common values 24 (cinema), 25/50 (PAL), 30/60 (NTSC/streaming), 120 (high-end).

Frames per second (fps)

Unit of frame rate. "60 fps" means 60 images are shown each second. Affects motion smoothness, bandwidth and encoder choice.

Gamma

A power-law transfer function (typically 2.2–2.4) historically used for SDR display. Reflects CRT physics; tuned to fit human luminance perception.

GOP

A repeating block of frames starting with an I- (or IDR-) frame followed by P/B frames. Defines the seek granularity and resilience to errors.

H.264 / AVC

2003 codec, the workhorse of the internet. Universally decoded by browsers, phones and TVs. Defines the baseline against which newer codecs are measured.

H.265 / HEVC

2013 codec, ~50 % more efficient than H.264 at the same quality. Dominates Apple ecosystem and 4K/HDR delivery; complicated by patent licensing.

H.266 / VVC

2020 successor to HEVC, ~50 % gain over it. Technically excellent but adoption has been slow due to patent uncertainty and AV1 competition.

Hardware acceleration

Encoding/decoding on dedicated silicon (GPU, VPU, ASIC) instead of CPU. Trades a small quality loss for huge speed and density gains.

HDR

Wider luminance range, wider color gamut and 10-bit-plus depth, delivering deeper blacks, brighter highlights and richer color. Multiple standards exist.

HDR10

The baseline open HDR standard — PQ, BT.2020, 10-bit, static metadata (MaxCLL/MaxFALL). Supported by virtually every HDR TV and streaming service.

HDR10+

HDR10 with per-scene dynamic metadata (Samsung-led). Royalty-free alternative to Dolby Vision; supported by Amazon Prime Video, Samsung, Panasonic.

HLG (Hybrid Log-Gamma)

Scene-referred HDR transfer function jointly designed by BBC and NHK for live broadcast. Backwards-compatible with SDR; no per-scene metadata.

HLS

Apple's HTTP-based adaptive streaming protocol — segments + manifest. Dominant on Apple devices; deeper coverage in the Streaming KB.

Huffman coding

Variable-length entropy code where common symbols get short codewords. Simple and fast; used by JPEG, MPEG-1/2 and inside CAVLC.

Hybrid codec

A codec architecture that combines prediction (intra/inter) with transform coding of the residual. All modern codecs from H.261 onwards are hybrid.

IDR frame

A special I-frame that flushes the decoder's reference list. A true clean random-access point — segment boundaries in HLS/DASH start at IDRs.

I-frame

A frame coded only with intra-prediction — decodable on its own. The starting point for any random access.

In-loop filter

Filter applied during decoding before the frame is stored as a reference. Improves both visual quality and the quality of subsequent predictions.

Integer transform

An approximation of the DCT using integer arithmetic only — bit-exact across implementations, making compliant decoding deterministic.

Intel Quick Sync

Intel's integrated-GPU video acceleration. Cheap and ubiquitous; mature support for H.264/HEVC and increasingly AV1.

Interlaced scan

Legacy scan where each frame is split into two fields (odd and even lines) transmitted sequentially to halve bandwidth. Causes combing artifacts.