Home Theater Technical Reference

Black Frame Insertion is a motion-clarity technique that inserts brief dark frames between lit ones — or strobes the LCD backlight — to shorten how long each frame is visible to the eye. The goal is to emulate the impulse-driven behavior of CRT displays, where each frame illuminates briefly and then goes dark, reducing the persistence-based smear that sample-and-hold panels otherwise produce.

BT.2020 is the ITU-R standard that defines the system colorimetry for ultra-high-definition television, specifying a wide-color-gamut RGB primary set covering about 75.8% of the CIE 1931 chromaticity area. In practice, virtually all current HDR content is color-graded inside a P3-D65 sub-gamut and carried in the BT.2020 container, because no consumer mastering monitor or TV can faithfully reproduce true BT.2020 primaries.

Chroma subsampling is a bandwidth-saving technique that retains full per-pixel luminance resolution while encoding the two chrominance components at lower spatial resolution. The J:a:b notation describes a J-pixel-wide by 2-pixel-tall sample window where J is the luma reference, 'a' is the count of chroma samples in the first row, and 'b' is the number of chroma sample changes between rows. Every consumer video delivery format — UHD Blu-ray, broadcast, cable, and streaming services like Netflix, Disney+, and Apple TV+ — ships at 4:2:0.

Color gamut is a 2D construct — the area of chromaticity coordinates a display can reproduce, drawn as a triangle on the CIE 1931 diagram with luminance ignored. Color volume extends that into a 3D solid by adding luminance, describing which colors are reproducible at every brightness level rather than only at one reference luminance. For HDR, where colors must hold at high luminance, the 3D figure is the more meaningful number.

DCI-P3 is the wide-gamut RGB color space released in 2005 by Digital Cinema Initiatives, LLC for theatrical digital projection and formalized in SMPTE RP 431-2. It is larger than BT.709/sRGB but smaller than ITU-R BT.2020. On consumer TV and monitor spec sheets, 'DCI-P3' almost always means P3-D65 — the same P3 primaries with a D65 white point rather than the green-tinted ~6300 K cinema white.

MLA is a microscopic lens layer added on top of WOLED pixels that redirects light emitted at oblique angles back toward the viewer. It raises peak HDR brightness by roughly 60 to 70 percent over a non-MLA panel of the same OLED chemistry, without changing the underlying emitter material or driving scheme.

QD-OLED is an OLED panel architecture that uses a blue OLED emission layer combined with quantum-dot color-conversion films for red and green, instead of the white OLED plus color-filter approach used by traditional WOLED. The conversion approach produces wider color volume and higher saturation at full luminance than WOLED of the same generation.

Tandem OLED is a stacked-emitter OLED panel architecture in which red, green, and blue emission layers are vertically laminated within a single panel, distributing drive current across multiple emission stacks rather than overdriving a single one. LG Display's TV implementation, formally branded Tandem WOLED, debuted on the 2025 LG G5 and Panasonic Z95B as Primary RGB Tandem and was upgraded to Primary RGB Tandem 2.0 on the 2026 LG G6, W6, and the 77-inch and 83-inch C6H sizes. Panel-spec peak brightness claims (4,000 nits in 2025; 4,500 nits in 2026) describe the panel's theoretical maximum, not the calibrated TV-mode output reviewers measure, which lands at roughly half the panel-spec figure.

Tone mapping is the process of fitting an HDR master's luminance range into the actual brightness, black-level, and color-volume capability of the output device. ITU-R BT.2390 defines the reference behavior for HDR-to-HDR display mapping and BT.2408 covers HDR-to-SDR conversion guidance, while HGiG specifies a game-side variant that pre-maps the signal so the display can pass it through.

WOLED is a panel architecture that pairs a white-light OLED emitter with a four-sub-pixel color-filter array of red, green, blue, and unfiltered white. It is manufactured exclusively by LG Display and supplied to brands including LG Electronics, Sony, Panasonic, Philips, Loewe, JVC, Hisense, and Konka.

An all-channels-driven (ACD) power rating is the continuous per-channel power an amplifier can deliver while every channel is driven into its rated load at the same time, for the full rated bandwidth and distortion. It is almost always lower than the headline 1-channel- or 2-channel-driven number, because that number is measured with the unused channels idle.

Bass management is the AVR or preamp function that routes low-frequency content from any channel to the loudspeakers actually capable of reproducing it — typically a subwoofer — based on each channel's Small/Large setting and a configured crossover frequency. It is distinct from the discrete LFE (.1) channel, which is a separately encoded effects track in the source program. The subwoofer output is the sum of the LFE channel and the bass redirected from any channel set to Small.

Bi-wiring runs two separate cables from one amplifier output to a speaker's HF and LF binding posts, with the speaker's internal passive crossover unchanged. Passive bi-amping uses two amplifier channels per speaker but still routes the full-range signal through that same internal passive crossover. Active bi-amping splits the signal with an electronic crossover ahead of the amplifiers and bypasses the speaker's passive crossover entirely.

Class AB and Class D are the two amplifier topologies that dominate home audio. Class AB runs its output transistors in a continuously-conducting linear mode biased to overlap the push and pull devices, while Class D runs them as switches that are either fully on or fully off, with a passive LC filter reconstructing the audio waveform from a high-frequency pulse train.

Crossover slope is the steepness of a filter's rolloff outside its passband, expressed in decibels per octave. The Linkwitz-Riley 4th-order alignment (LR4, 24 dB/oct) is the de facto standard topology in modern audio crossovers and the alignment used by THX-style bass management on the subwoofer feed. Each additional filter order adds another 6 dB/octave of rolloff.

Damping factor is the ratio of the nominal loudspeaker load impedance (typically 8 Ω) to the amplifier's source (output) impedance — a dimensionless number. It quantifies how strongly the amplifier short-circuits the speaker terminals and, by extension, how much the amplifier resists the back-EMF a moving voice coil generates at driver resonance.

Speaker impedance is the AC opposition to current flow at a given frequency, measured in ohms; it is a curve across the audible band, not a single static number. The label printed on the box — "8 ohms," "4 ohms," "6 ohms" — is a nominal impedance, defined under IEC 60268-5 such that the rated value is no more than 1.25 times the impedance minimum inside the rated band. The single-number rating is shorthand for the whole curve.

Reference level is the SMPTE/Dolby cinema calibration target where dialogue averages 85 dB SPL (C-weighted, slow) at the listening position, with each main channel capable of 105 dB SPL peaks and the LFE/subwoofer capable of 115 dB SPL peaks. The acoustic scale is anchored to the digital scale so that 0 dBFS — the highest sample value a digital container can represent — corresponds to a 105 dB SPL peak on a main channel after calibration. On AVRs that follow the Dolby/THX convention, '0.0 dB' Master Volume is the reference position; negative numbers indicate attenuation below it.

Sensitivity is the sound pressure level a loudspeaker produces at one meter for a defined electrical input. It is published in two conventions: a power reference of dB SPL at 1 watt / 1 meter, and a voltage reference of dB SPL at 2.83 V / 1 meter. The two numbers are identical for an 8-ohm load and diverge for any other impedance.

SINAD (Signal-to-Noise And Distortion) is a single-figure audio-quality metric that ratios the test-tone power against everything else in the band — noise plus all distortion components — and reports the result in decibels. The canonical measurement is a 1 kHz sine-wave stimulus, and Audio Science Review popularized SINAD as the headline benchmark for DACs and amplifiers in consumer audio.

THD+N is the ratio of all non-fundamental energy at a device's output — harmonic distortion products plus noise, hum, and interference — to the fundamental test signal, expressed as a percentage or in dB. The canonical stimulus is a sine wave (1 kHz under IEC 60268 for analog systems, 997 Hz under AES17 for digital systems) measured over a defined audio bandwidth, conventionally 20 Hz to 20 kHz.

Bass traps are low-frequency acoustic absorbers used to control room modes and decay time in the bass region — typically below ~250 Hz, and often below ~100 Hz where standing-wave problems concentrate. The canonical taxonomy splits them into porous (resistive, broadband) absorbers and resonant absorbers, with the resonant family further subdivided into panel/membrane absorbers (moderately tuned) and Helmholtz resonators (sharply tuned to a single frequency).

Critical distance is the distance from a sound source at which the direct-sound level equals the reverberant-sound level in a room. Listeners closer than this are in the direct-dominated zone; listeners farther away are in the reverberant-dominated zone. It is a property of the source and the room together, not of the speaker alone.

First-reflection points are the geometric locations on the side walls, ceiling, and floor where the direct sound from a loudspeaker bounces once before arriving at the listening position. Each speaker has its own set of these points, and the standard way to find them is the mirror trick: any spot where you can see the tweeter reflected in a flat mirror held against a surface is a first-reflection point for that speaker.

A room mode is a low-frequency resonance that builds up at a specific frequency inside an enclosed room because the wavelength fits an integer number of times between parallel boundary surfaces. Mode frequencies are determined by the room's three internal dimensions, and modes dominate audible bass quality below the Schroeder transition (roughly 200–300 Hz in domestic rooms).

RT60 is the time, in seconds, for a sound's energy to decay by 60 decibels after the source stops. It quantifies how reverberant a room is and is the primary single-number descriptor of room acoustics in the standards used for listening rooms (ITU-R BS.1116) and recording studios.

The Sabine equation, RT60 = 0.161 × V / A (V in m³, A in metric Sabines), predicts the reverberation time of a room from its volume and total absorption. It was derived empirically by Wallace Clement Sabine, a 30-year-old Harvard assistant professor of physics, on 29 October 1898 after three years diagnosing the unintelligible Fogg Art Museum lecture room. The result is the foundation of modern architectural acoustics.

SBIR is a frequency-response notch caused by sound reflecting off a nearby wall, floor, or ceiling and arriving out of phase with the direct sound at the listening position. The cancellation lands at the frequency whose quarter-wavelength equals the boundary distance, producing a measured dip of 6 to 15 dB.

The Schroeder frequency marks the cross-over between a room's low-frequency region (where individually identifiable modes dominate) and the high-frequency region (where dense modal overlap produces a statistically diffuse sound field). It is defined as the frequency at which the average half-power bandwidth of room modes equals roughly three times the average mode spacing — a 3-fold modal overlap criterion.

A standing wave is the stationary pressure pattern formed when an incident wave and its reflection of the same frequency superpose at a boundary, producing fixed nodes (minima) and antinodes (maxima) instead of a wave that propagates. Inside a bounded space these patterns only exist at frequencies where an integer number of half-wavelengths fits between the reflecting boundaries. The set of those supported configurations inside a room is what acousticians call the room's modes.

Auto Low Latency Mode (ALLM) is an HDMI feature that lets a source device — a console, PC, or streamer — automatically signal a display to switch into its lowest-latency picture mode for gaming, then revert when the source no longer requests it. Introduced in HDMI 2.1, it removes the manual menu trip into Game Mode that traditionally had to be done before each play session. ALLM is optional in the spec and backward-compatible with HDMI 2.0 ports.

ARC is an HDMI 1.4 feature, introduced in 2009, that lets a TV send audio back to a connected AVR or soundbar over the same HDMI cable that carries video into the TV. Its audio link is capped at roughly 1 Mbps, which is enough headroom for stereo PCM and the lossy 5.1 codecs (Dolby Digital, DTS, Dolby Digital Plus) but not for lossless TrueHD or DTS-HD Master Audio. It has been superseded by eARC for lossless audio and lossless Dolby Atmos passthrough.

Dolby Atmos FlexConnect makes a compatible TV the central Atmos object renderer for a set of wirelessly-paired accessory speakers that can be placed anywhere in the room. Built-in TV microphones run an acoustic-mapping calibration that locates each speaker and adapts the object scene to whatever non-canonical layout it finds. The technology was unveiled by Dolby on 28 August 2023 ahead of IFA 2023 and shipped first on TCL's 2024 TV lineup.

eARC is an HDMI feature, introduced in the HDMI 2.1 specification, that returns lossless and uncompressed audio (Dolby TrueHD with Atmos, DTS-HD Master Audio, multichannel PCM up to 8 channels at 24-bit/192 kHz) from a TV to an AVR or soundbar over a single HDMI cable. It replaces the bandwidth-limited legacy ARC (Audio Return Channel) and resolves the long-standing issue of streaming-app and built-in-tuner audio being downgraded before it reaches a connected sound system.

HDCP 2.3 is the current revision of High-bandwidth Digital Content Protection, the link-layer encryption applied across HDMI, DisplayPort, MHL, USB-C, and several wireless interfaces to keep digital audio and video from being copied between source and display. Published by Digital Content Protection LLC on February 28, 2018, it is an incremental security-hardening of HDCP 2.2 rather than a new architecture, and the two revisions interoperate in both directions.

HDMI 2.1 is the version of the HDMI specification released by the HDMI Forum on November 28, 2017, raising maximum link bandwidth to 48 Gbps via a new packet-based signaling scheme called Fixed Rate Link (FRL). It introduces support for 4K at 120 Hz, 8K at 60 Hz, resolutions up to 10K, and a set of optional gaming and audio features including VRR, ALLM, QFT, and eARC.

HDMI 2.2 is the next major HDMI specification released by the HDMI Forum on June 25, 2025 (announced January 6, 2025). It doubles the maximum transmission capacity to 96 Gbit/s, up from HDMI 2.1's 48 Gbit/s, carried over the new Ultra96 HDMI Cable. The spec also adds the Latency Indication Protocol (LIP) for improved audio-video synchronization.

HDMI-CEC (Consumer Electronics Control) is an HDMI feature that lets a single remote command and coordinate up to 15 CEC-enabled devices connected over HDMI. It has been part of the HDMI standard since the original HDMI 1.0 specification, released by the HDMI Founders on December 9, 2002.

HDMI Variable Refresh Rate (VRR) is a feature of the HDMI 2.1 specification that lets a gaming source — a console or PC — deliver each frame to the display the moment it is rendered, instead of on the display's fixed refresh interval. The HDMI Forum's stated benefit is that VRR reduces or eliminates lag, judder and frame tearing for more fluid gameplay. It is the cross-vendor analogue to NVIDIA G-SYNC and AMD FreeSync, sharing the VESA Adaptive-Sync lineage with G-SYNC Compatible.

AirPlay 2, Google Cast, Spotify Connect, and Tidal Connect are the four major Wi-Fi-based protocols for sending audio to networked endpoints — speakers, AVRs, and smart displays — over the local IP network. All four support multi-room scenarios and run over Wi-Fi, which makes them fundamentally distinct from Bluetooth's point-to-point radio link.

WiSA is a cross-vendor wireless multichannel speaker protocol for sending uncompressed surround audio from a source to certified speakers from any participating brand. The standard now spans three transports: WiSA HD (5 GHz dedicated radio, lossless), WiSA Discovery (entry-level 2.4 GHz), and WiSA E (embedded software running over standard Wi-Fi chipsets). Its defining feature is multi-brand interoperability — a transmitter from one vendor pairs with speakers from another.

DD+ JOC is the lossy transport that streaming services use to deliver Dolby Atmos. It combines a conventional Dolby Digital Plus channel bed (5.1 or 7.1) with a Joint Object Coding side-data payload that lets the decoder reconstruct the Atmos object scene from that downmix. It is what you are almost always hearing when an app says 'Dolby Atmos' over the internet rather than off a disc.

Dolby Atmos is an object-based immersive audio format from Dolby Laboratories that authors individual sounds as positioned audio objects in 3D space rather than as fixed channel feeds. The renderer in your AVR or soundbar then maps those objects onto whatever speaker layout you have, from headphones to a 24.1.10 home theater.

Dolby TrueHD is a lossless, multi-channel audio codec built on the Meridian Lossless Packing (MLP) compression layer, used principally in Blu-ray Disc and UHD Blu-ray. On UHD Blu-ray it serves as the carrier for Dolby Atmos object metadata. No major streaming service delivers TrueHD — streaming Atmos uses lossy Dolby Digital Plus instead.

Dolby Vision is Dolby Laboratories' proprietary HDR format, introduced in 2014, that augments a base video stream with dynamic per-scene or per-frame metadata standardized as SMPTE ST 2094-10. It is mastered with up to 12-bit per-channel color and a 10,000-nit reference ceiling, and it is delivered through a small set of distribution profiles that differ in base codec, color space, and backward compatibility.

DTS:X is DTS's object-based immersive audio codec, designed to place sounds where they would occur naturally in space rather than locking them to fixed channels. On UHD Blu-ray it rides inside a lossless DTS-HD Master Audio bitstream; for streaming, a separate lossy DTS:X variant delivers the format at roughly 448 kbps. Unlike Dolby Atmos, the consumer codec is explicitly speaker-layout-agnostic, with the renderer mapping objects to whatever speakers the listener actually has.

HDR10 is an open high-dynamic-range video standard announced on 27 August 2015 by the Consumer Electronics Association (now CTA), built on the ITU BT.2100 family. It pairs 10-bit color, the BT.2020 wide color gamut, and the SMPTE ST 2084 Perceptual Quantizer transfer function with a single set of static metadata that travels with the title.

HDR10+ is a royalty-free, open dynamic-metadata HDR format announced on 20 April 2017 by Samsung Electronics and Amazon Video, then formalized as the HDR10+ Technologies, LLC joint venture by Samsung, 20th Century Fox, and Panasonic at IFA 2017. It is standardized as SMPTE ST 2094-40 and sits on top of the HDR10 base layer, adding per-scene or per-frame statistical metadata so a display can apply scene-by-scene tone mapping rather than HDR10's single static curve.

HGiG (HDR Gaming Interest Group) is a volunteer cross-industry group that publishes best-practice guidelines for HDR gaming, organized by Microsoft Corporation and Sony Interactive Entertainment Inc. It is explicitly not a standards body — it does not write specifications, run compliance testing, license trademarks, or operate a certification program.

HLG (Hybrid Log-Gamma) is a broadcast-oriented HDR transfer function jointly developed by the BBC and NHK and standardized in ITU-R BT.2100 alongside PQ. It is scene-referred and carries no metadata, and the lower half of its signal range uses a conventional gamma curve so the same stream remains watchable on legacy SDR displays.

LPCM is uncompressed multichannel digital audio in which amplitude is sampled at a fixed clock rate and quantized onto evenly spaced steps. Its bit-rate is simply sample rate multiplied by bit depth multiplied by channel count, which is what determines whether a given LPCM payload fits down an HDMI or eARC link.

PQ (Perceptual Quantizer) is the HDR transfer function published by SMPTE as ST 2084 in 2014, titled "High Dynamic Range Electro-Optical Transfer Function of Mastering Reference Displays." It replaces the gamma curve used in SDR and maps a normalized 0–1 signal to absolute luminance from 0 to 10,000 nits. PQ is the EOTF underneath HDR10, HDR10+, and Dolby Vision.