Common concepts & terminology in Media Technology. A resource for navigating media technology solutions, content management and video technology.
Glossary
Audio Mapping
Also called: Audio channel mapping, channel mapping, audio routing, audio configuration
Audio mapping is the process of defining how input audio tracks and channels feed the tracks and channels of an output media file. An audio map can copy or reorder channels, combine or split signals, attach external audio, and set properties such as channel layout, codec and language so that the output meets its delivery specification.
Detailed definition
What is audio mapping?
Audio mapping controls where audio goes when a media file is processed, transcoded, packaged or delivered. It connects selected audio from a source file or auxiliary file to specific tracks and channels in the output.
A track and a channel are not necessarily the same thing. An audio track is a stored sequence of audio data and may contain one channel, such as mono, or several channels, such as stereo or 5.1 surround sound. Audio mapping therefore operates at two related levels:
Track mapping: Selecting which input tracks become which output tracks.
Channel mapping: Assigning individual input channels, such as front left or centre, to positions in an output channel layout.
For example, a source master might contain a 5.1 programme mix, a stereo mix, an audio-description track and several dubbed-language tracks. Audio mapping determines which of these elements appear in each deliverable, in what order and with which technical labels.
How does audio mapping work?
An audio mapping configuration usually defines:
The source track, channel or external audio file to use.
The destination track and channel for each selected signal.
Whether a signal is copied, reordered, duplicated or mixed with other signals.
The required number and arrangement of output channels.
Output properties such as codec, bitrate, sample rate and language metadata.
Any gain values used when several input channels are combined.
Some mappings simply move audio without changing its content. Others use a mixing matrix to calculate each output channel from several inputs. A 5.1-to-stereo downmix, for example, normally combines the centre and surround channels with the left and right channels at defined gain levels.
Why is audio mapping important?
Broadcasters, streaming services and distribution partners may require different audio arrangements for the same programme. A technically valid file can still be rejected, played incorrectly or deliver the wrong language if its audio tracks are mapped in the wrong order.
Examples where Audio Mapping is needed
Produce stereo, surround and multi-language deliverables from the same master.
Match a broadcaster’s or platform’s required track allocation.
Keep dialogue, music and effects, audio description and dubbed versions correctly separated.
Maintain the relationship between audio content and metadata.
Automate repeatable transcoding and delivery workflows.
Converting 5.1 surround sound to stereo
Combining the left and right signals as a single mono track
Audio mapping compared with related processes
Audio mapping vs Audio mixing: Mapping determines the relationship between inputs and outputs. Mixing adjusts or combines signals to create a particular balance. A mapping can include mixing, but many maps only copy or reorder channels.
Audio mapping vs Downmixing: Downmixing is a specific type of audio mapping that combines a larger channel layout into fewer channels, such as 5.1 to stereo.
Audio mapping vs Channel layout: A channel layout describes the channels and their intended positions. Audio mapping determines how source channels are assigned to that layout.
Audio mapping vs Transcoding: Transcoding converts media into another encoding format or profile. Audio mapping is one part of a transcoding configuration.
In Knox Media Hub, Audio Mapping is a transcoding capability for creating custom output audio tracks. Configurations can join mono tracks, incorporate audio from auxiliary files, edit output-track properties and be saved as reusable presets.
💡 Media Tech Insights
Automated Quality Control
Also called: Automated QC, AQC, AutoQC or Automatic QC.
Quality control (QC) in media is the inspection of audio and video assets to identify technical, structural or content-related problems. Common issues include invalid formats, incorrect audio loudness, black or frozen frames, audio silence and missing or inconsistent metadata.
Automated quality control (AQC or AutoQC) is the software-based inspection of media files against predefined technical rules. An automated QC engine analyses a file using a configurable template of requirements, limits and tolerances. It then produces a report that helps media teams determine whether the asset is ready for broadcast, streaming, archiving or delivery.
Cloud QC is automated quality control performed using remotely hosted, cloud-based processing resources rather than dedicated QC hardware installed on premises. Cloud QC services can access media in cloud storage, process files on demand and return results to a media management or workflow orchestration platform. This approach is particularly useful when workloads fluctuate or large volumes of content must be checked in parallel.
Detailed definition
How does automated quality control work?
An automated QC workflow begins by applying a QC template to a media file. The template specifies which checks to perform and the acceptable values or tolerances for the intended destination.
The QC engine analyses the file, its encoded audio and video streams, its container or wrapper, and relevant technical metadata. It may return pass, warning or fail results, often with timecodes identifying where individual problems occur.
The results can then trigger further workflow actions. A compliant file might continue automatically to transcoding, packaging or delivery, while a failed file may be stopped, sent for manual review, returned to its supplier or replaced.
What does automated QC check?
The exact tests depend on the media format, destination and configured template. Common checks include:
File and format: Container, codec, resolution, frame rate, aspect ratio, bitrate, duration and file readability.
Video: Black or frozen frames, colour bars, blanking errors, luminance or colour-gamut violations, flashes and other signal anomalies.
Audio: Silence, clipping, excessive peaks, phase problems, incorrect channel count or layout, and programme loudness.
Metadata and structure: Missing or inconsistent identifiers, timecode, track labels, language codes and other required technical metadata.
Specification compliance: Whether measured values fall within the thresholds set by a broadcaster, platform, archive or delivery partner.
Audio loudness tests may use measurements based on standards such as ITU-R BS.1770, but the acceptable target and tolerance must still be defined by the relevant delivery specification.
Automated QC does not necessarily use artificial intelligence. Many important checks are deterministic measurements of signal values, file structures and conformance rules. However, newer tools improve these tests with machine learning for more subjective or content-aware analysis.
Where is automated QC used?
Automated QC can be placed at several points in a media supply chain:
At ingest: Check that incoming masters are readable, complete and compatible with the receiving system.
After transcoding: Confirm that conversion has not introduced errors and that the output matches the selected profile.
Before delivery: Validate a programme against a broadcaster’s, streaming service’s or client’s delivery specification.
During archive migration: Identify corrupt, incomplete or non-conforming material before or after files are moved.
In localization workflows: Check language tracks, channel layouts, subtitles and version-specific technical requirements.
Different destinations can require different QC templates. A file that passes an internal archive profile may still fail a broadcaster or streaming platform’s delivery specification.
Automated QC versus Manual QC
Automated QC is fast, repeatable and suitable for large file volumes, but it cannot determine every aspect of programme quality. A technically compliant file may still contain an incorrect edit, a mistranslated subtitle, poor creative sound mixing or the wrong programme version.
Manual QC uses a trained operator to evaluate technical, editorial and perceptual quality. In many professional workflows, automation identifies measurable errors and directs reviewers to likely problem areas, while people assess context and subjective quality.
Automated QC should also be distinguished from quality assurance (QA). QC examines individual outputs for defects or non-compliance; QA covers the wider processes, controls and practices intended to prevent those defects.
💡 Media Tech Insights
AV
Also called: Audiovisual, Audio-visual, AudioVisual, A/V
AV (audiovisual) refers to content, technology or systems that work with sound, visual media or both. In media technology, AV includes the equipment, software and infrastructure used to capture, process, store, manage, transmit and present audio and images.
Detailed definition
What does AV mean?
AV is the standard abbreviation for audiovisual. The term has two closely related meanings:
Audiovisual content: Time-based media containing images and sound, such as television programmes, films, streamed video, recorded presentations and social media videos. The International Telecommunication Union (ITU) defines audiovisual content as time-based content consisting of images and sounds.
AV technology or systems: The hardware, software, networks and operational processes used to create, process, transport, manage or reproduce audio and visual information.
AV is therefore an umbrella term, not a particular file format, connector or technical standard. A conference-room AV system, for example, serves a different purpose from a television production facility, even though both may use cameras, microphones, displays, speakers, signal processing and network infrastructure.
How does an AV system work?
An AV system moves audio and visual information through a signal or content chain. A typical workflow includes:
Capture or source: Cameras, microphones, media players, computers or stored media files provide pictures and sound.
Processing: Mixers, production switchers, encoders, digital signal processors, editing software or cloud services modify, combine or convert the signals.
Transport: Cables, broadcast infrastructure or Internet Protocol (IP) networks carry the audio, video and related data.
Management and storage: Media Asset Management (MAM) platforms, storage systems and metadata services organise and track audiovisual assets.
Presentation or distribution: Displays, projectors, speakers, broadcast channels, streaming services or digital platforms deliver the result to an audience.
Control and monitoring: Software and control systems route sources, operate devices, monitor quality and automate repeatable processes.
AV vs. Video vs. Broadcast vs. IT
AV and video are not synonymous. Video principally concerns moving images, although a video file commonly contains one or more audio tracks. AV explicitly covers the wider relationship between audio and visual elements and the systems that handle them.
AV is broader than broadcast. Broadcast technology is designed for producing and distributing television or radio services to audiences. Professional AV also includes corporate communications, education, live events, venues, control rooms, digital signage and collaboration systems.
AV increasingly converges with IT. Network switches, IP addressing, cloud services, software-defined processing, cybersecurity and APIs now play important roles in many AV environments.
AV is not necessarily a single combined signal. In some professional systems, audio, video and data travel separately and are synchronised at another point in the workflow.
AVOD
Also called: Ad-supported Video On Demand, advertising-funded, advertising-supported, advertising-based or ad-based video on demand.
AVOD (Ad-supported Video On Demand) is a streaming model in which viewers select video content from an on-demand catalogue and advertising funds some or all of the service. Ads may appear before, during or after the selected programme and can be delivered dynamically. AVOD services commonly provide free access, although some combine advertising with a subscription fee.
Detailed definition
What does AVOD mean?
AVOD stands for advertising-based video on demand, also described as advertising-funded or ad-supported video on demand.
In an AVOD service, viewers decide what to watch and when to watch it, while the provider generates revenue by placing advertisements around or within the content.
Many AVOD services are free to viewers (e.g: Youtube). However, free access is not an absolute requirement in every industry definition. Some organisations use AVOD broadly enough to include lower-cost subscription tiers that also show advertising. Other frameworks classify services combining subscription payments and advertising as hybrid video on demand (HVOD).
How does AVOD work?
A typical AVOD session follows this process:
The viewer selects content. Unlike a scheduled channel, the viewer chooses a film, episode, clip, user-generated content or programme from a catalogue.
The platform identifies advertising opportunities. Ad markers or playback rules determine where advertisements can appear, such as before, during or after the programme.
An ad decision is made. An ad server may choose an advertisement using information such as the content category, device, location, campaign rules or consented audience data.
The advertisement is inserted. Client-side ad insertion requests ads through the viewer’s application, while server-side ad insertion can combine advertising and programme content into a more continuous stream.
Playback and measurement data are recorded. The platform may report impressions, completed views, errors and other events used for campaign measurement and revenue calculation.
Is AVOD always free?
AVOD is commonly free to viewers, but the term is also used for services that combine advertising and subscription revenue.
For clarity, a paid service with advertisements can be described as an ad-supported subscription tier or a hybrid subscription-and-advertising model.
AVOD compared with other viewing models
| Model | How viewers access content | How it is funded |
|---|---|---|
| AVOD — Advertising-funded video on demand | Viewers select a title and start playback when they choose. | Advertising, sometimes combined with subscription fees. |
| SVOD — Subscription video on demand | Viewers access an on-demand catalogue through a subscription. | Recurring subscription fees; some tiers also carry advertising. |
| TVOD — Transactional video on demand | Viewers rent or purchase individual titles. | Payments for each title or transaction. |
| FAST — Free ad-supported streaming television | Viewers tune into scheduled linear streaming channels. | Advertising, with no subscription charge for channel access. |
What is the difference between AVOD and FAST?
AVOD and free ad-supported streaming television (FAST) both use advertising, but they describe different viewing experiences:
AVOD is on demand: The viewer chooses a particular title and starts it when desired.
FAST is linear: The viewer joins a scheduled channel and watches whatever is currently playing.
AVOD and the tech stack
Launching and operating an AVOD service requires more than inserting advertisements. Media teams must prepare and manage content, metadata and advertising opportunities across the full distribution workflow.
Typical operational requirements include:
Ingesting and cataloguing programme assets.
Confirming territorial, platform and advertising rights.
Creating streaming renditions for different devices and connection speeds.
Preparing clean masters and, where necessary, versions containing ad markers.
Managing captions, subtitles, audio descriptions and localized versions.
Associating titles with accurate editorial and advertising metadata.
Applying content and advertising compliance rules.
Packaging and delivering content to an OTT platform.
Checking programme and advertisement playback through automated and manual QC.
Monitoring availability windows, failures and delivery status.
A Media Asset Management (MAM) or media supply chain platform can support these processes by connecting content, metadata, processing tools and distribution destinations. However, a MAM does not automatically constitute an AVOD service: the consumer application, video player, content delivery infrastructure and advertising technology are also required.
External references
Amazon Ads: AVOD, SVOD and TVOD explained — viewing models and AVOD versus FAST.
IAB UK: Advertiser VOD — definition and hybrid funding models.
Examples: Tubi: Why are there ads? and Pluto TV.
Related terms
VOD (Video on demand): The broader viewing model in which viewers choose when to start content.
FAST (Free ad-supported streaming television): Scheduled, advertising-funded streaming channels.
SVOD (Subscription video on demand): Subscription-based access to an on-demand catalogue.
TVOD (Transactional video on demand): Rental or purchase of individual titles.
OTT (Over-the-top): Internet delivery of video; AVOD is one funding model used by OTT services.