Picture & sound reference

The active image area is the portion of a video frame containing the intended scene rather than padding or embedded bars. It can be smaller than the full encoded frame dimensions.

Audio bit depth describes the number of bits used to represent each sample value in a relevant digital representation. It relates to quantisation precision, not directly to the loudness setting or the number of speakers.

Audio clipping occurs when a signal exceeds the range a processing or reproduction stage can represent cleanly, flattening peaks and potentially introducing distortion. It is separate from ordinary data compression and from a quiet overall programme level.

Audio description provides narration of important visual information, such as actions, scene changes and meaningful on-screen text. It supports understanding of content that ordinary dialogue or sound alone may not explain.

An audio downmix combines a presentation with more channels into one with fewer channels, such as converting a multichannel mix for stereo speakers. Correct handling should account for dialogue and other important information.

Audio dynamic range concerns the difference between quieter and louder parts of a signal or presentation. It is separate from data bitrate and from the position of the television’s volume control.

Audio passthrough sends supported encoded sound onward for another device to decode rather than decoding it in the player first. The receiving equipment and transport route must understand the format being sent.

Audio sample rate counts how many waveform samples are represented each second, commonly expressed in kilohertz. It is different from compressed bitrate, volume and the number of speaker channels.

Black level concerns the reproduction of the darkest signal region and, in display discussions, how dark black appears. A television control with that name may affect signal interpretation rather than simply increasing panel light output.

Blooming is visible glow around a bright object in an otherwise darker area, often associated with backlight zones larger than the object. It is a display interaction rather than automatic evidence of damaged video data.

Chroma carries colour-related information in video systems that separate it from a brightness-related component. It helps represent how colours differ while allowing the encoder to allocate detail differently across components.

Chroma subsampling reduces the spatial sampling of colour components relative to brightness-related information. Formats commonly described as 4:2:0,4:2:2 and 4:4:4 represent different sampling arrangements rather than universal picture-quality scores.

Closed captions are a selectable timed-text presentation intended to convey dialogue and relevant sound information. They can include speaker identification, music cues and other audio details needed to understand the programme without relying on sound.

A codec level defines a set of limits or constraints associated with a coding standard. It helps describe the demands a stream can place on a decoder, rather than assigning an artistic picture-quality score.

A codec profile identifies a defined set of coding features within a codec family. A device can support the family name while implementing only particular profiles or configurations of that family.

Colour banding is the visible separation of a smooth tonal or colour gradient into steps. It is often easiest to notice in skies, fog, dim walls and other areas that should change gradually.

Colour gamut is the range of colours a system can represent or reproduce under specified conditions. It is separate from the strength of a saturation slider and from the spatial resolution of the picture.

Colour temperature is a way to describe the appearance of a white reference along a temperature-related scale. Television warm and cool controls use the idea to offer different overall white-balance presentations.

Colour volume considers colour reproduction across brightness levels rather than describing only a two-dimensional gamut boundary. It helps distinguish the ability to show saturated colours at different luminances from a simple list of reachable colour coordinates.

A compression artefact is an unwanted visible or audible effect introduced when media is represented with reduced data or processed through a coding pipeline. It can include blocks, ringing, smearing or unstable texture.

Constant bitrate aims to maintain a specified data rate over a defined interval or delivery model. It can make capacity planning more predictable, but the exact behaviour depends on the encoding and transport implementation.

Contrast ratio compares bright and dark output under defined conditions. It is a display characteristic with measurement-dependent meaning, not a streaming bitrate or a direct score for the quality of an individual programme.

Deinterlacing converts field-based interlaced material into a presentation suitable for a progressive display. It must account for the fact that alternating fields can represent different moments, especially in moving scenes.

A descriptive transcript presents spoken information and important visual content as readable text. It can support reading at one’s own pace, searching a discussion or understanding material outside the original audiovisual presentation.

Display aspect ratio is the intended overall width-to-height shape of the visible picture. It is commonly written as 16:9,4:3 or a decimal ratio for wider film compositions.

Dithering introduces a controlled pattern or noise to make quantisation steps less conspicuous. It changes how limited precision is perceived rather than recovering the exact original values removed earlier.

Edge enhancement increases contrast around image boundaries to create a stronger impression of sharpness. It is a processing effect rather than a recovery of missing camera or encoder detail.

Field order specifies the temporal sequence of fields in interlaced video. Correct interpretation matters because the fields can represent different moments, and reversing their order can make movement appear unstable.

Film grain is texture associated with photographic film and can also be simulated as an artistic treatment. It is not automatically a sign of a poor stream, although compression can represent it badly.

Forced subtitles present selected translations or text needed for understanding, rather than captioning every spoken line. They may cover foreign-language dialogue, signs or written messages within a programme whose main audio already matches the viewer’s language.

Frame cadence is the pattern used to present source frames over time, including repetitions needed to fit a display’s refresh timing. An even cadence can preserve consistent motion, while uneven repetition can introduce visible judder.

Gamma commonly describes a tonal relationship used when mapping intermediate signal levels in an SDR picture. A television’s gamma control can alter how light or heavy midtones appear without changing the pixel dimensions.

A group of pictures, or GOP, is an organised sequence of coded pictures with a reference structure. Its design affects compression efficiency, random access and aspects of startup or seeking behaviour.

Image scaling maps one pixel grid into another, enlarging or reducing a picture to fit a display or output mode. It is a normal part of showing sources with different dimensions on a fixed-pixel screen.

Inter-frame prediction compresses video by describing relationships between pictures over time. Instead of independently storing every frame, the encoder can reuse information from reference pictures and encode the remaining differences.

Intra-frame coding represents a picture using information within that picture rather than depending on other pictures in time. It is one building block used by modern video coding systems.

Judder is a perception of uneven motion, often associated with frame cadence or low temporal sampling. It differs from a complete buffering pause, although viewers sometimes use the same word for several kinds of hesitation.

A keyframe is a picture or access point that supports independent entry into a compressed video sequence, subject to the codec and stream structure. It helps a decoder begin or recover without relying on an unlimited chain of earlier pictures.

Letterboxing preserves a wide image inside a narrower display shape by leaving space above and below. The bars may be added by the player or encoded as black pixels within the source frame.

Lip synchronisation is the timing relationship between the picture and matching sound. A constant early or late offset differs from drift that grows over the course of playback and may require a different investigation.

Local dimming adjusts the light output of separate backlight regions in a compatible display. It can improve the relationship between bright and dark areas, but each zone may cover many image pixels.

The low-frequency effects channel, often represented by the .1 in a conventional 5.1 layout, carries designated low-frequency effects information. It is not simply a promise that all bass in the programme belongs to one channel.

Luma is a brightness-related component used in common video colour representations. It is derived from colour components and should not be treated as identical to a direct measurement of physical light from the screen.

Macroblocking describes conspicuous block-like regions in a compressed picture, often noticeable when fine detail or motion is difficult to encode. The visible blocks are an artefact rather than the screen’s ordinary physical pixel grid.

A media container organises compressed tracks, timing and metadata into a file or presentation structure. It can hold video, audio, subtitles and other information, depending on the format and implementation.

Motion interpolation estimates intermediate pictures between source frames to make movement appear smoother. It is a display or playback process, not additional original footage captured by the camera.

A motion vector describes an estimated displacement used in motion-compensated video prediction. It helps an encoder and decoder relate regions across pictures rather than storing every new image entirely from scratch.

Native display resolution is the fixed pixel grid of a digital panel. It describes the display’s physical sampling structure, rather than the dimensions of every programme shown on it.

Overscan enlarges an incoming image slightly so its outer edges fall beyond the visible screen. It can hide unwanted borders in some sources but can also crop useful modern interface and programme information.

PCM, or pulse-code modulation, represents a sampled audio waveform using discrete values. In playback settings, PCM commonly indicates that audio has been decoded before being sent to the next device.

Peak luminance describes a display’s maximum light output under specified measurement conditions. It is relevant to bright highlights, but the number alone does not describe sustained brightness, black levels, colour accuracy or complete HDR performance.

Pillarboxing places unused areas at the left and right when a narrower picture is shown on a wider screen without distortion. Older 4:3 television material commonly produces this presentation on a 16:9 display.

Pixel aspect ratio describes the intended width-to-height shape of one stored image sample. A ratio of one to one means square pixels; other ratios require appropriate display scaling.

Pixel density expresses how many display pixels occupy a physical distance, commonly stated as pixels per inch. It connects resolution with screen size rather than describing the source programme’s encoding.

Quantisation maps a range of values into a limited set of representable steps. In video processing and compression, those choices influence how much precision is retained and how visible errors become.

Ringing is an oscillating light or dark pattern near a sharp image boundary. It can arise from compression or image processing and may appear as outlines or ripples around text and high-contrast objects.

A sample-and-hold display keeps an image visible for a substantial part of each refresh interval. The interaction between that persistence and eye movement can influence perceived motion blur, even when individual pixels respond quickly.

Spatial resolution concerns how finely an image represents detail across width and height. In common video specifications it is expressed using frame dimensions, such as 1920 × 1080 pixels.

SubRip, commonly associated with the .srt extension, is a widely used subtitle text format containing numbered cues and timing information. Player support, character encoding and styling behaviour can vary across implementations.

Temporal resolution describes how finely changes over time are represented. For ordinary video, frame rate is a key part of it: more distinct captured frames can describe movement in smaller time steps.

A timed-text cue is a unit of text associated with a start and end time in a caption or subtitle presentation. It may also carry placement or styling information where the format and player support it.

Tone mapping adapts a source’s tonal range to a display’s available capabilities. In HDR viewing it helps determine how highlights, midtones and shadows are fitted when the screen cannot reproduce the source range directly.

A transfer function defines a relationship between signal values and a represented light-related quantity. It is part of how video systems encode and reproduce tones, rather than a simple resolution or colour-strength setting.

Variable bitrate allocates different amounts of compressed data over time rather than maintaining one exact rate for every moment. An encoder can spend more on difficult scenes and less on simpler ones.

Video bit depth describes how many binary digits represent a component value. Eight bits provide 256 possible values per component, while ten bits provide 1024, before considering the system’s particular coding conventions.

Video bitrate is the amount of compressed video data used over time, usually expressed in kilobits or megabits per second. It is separate from resolution, frame rate and the total internet capacity of a household.

A video codec defines methods for encoding and decoding compressed moving images. H.264, HEVC and AV1 are examples of codec families, while MP4 and Matroska describe containers that can carry compressed tracks.

Viewing angle describes how a display’s appearance changes when seen away from a reference position, commonly straight on. Contrast, colour and brightness can vary across seats depending on the panel and optical design.

WebVTT is a timed-text format used with web media. It can carry caption or subtitle cues and associated presentation information for a compatible browser or player to display alongside video.

White point describes the chromaticity chosen to represent neutral white in an imaging system. It influences the overall colour balance of a display rather than the number of pixels or frames being shown.