# What is Video Compression?

Video compression reduces the data needed to represent moving images by removing spatial, temporal, or perceptually insignificant information. A codec defines how an encoder represents frames and a decoder reconstructs them.

Video + audio tracks

Video processing

Playable derivative

Video processing decodes timed tracks, transforms them, and encodes a deliverable for a target player. This diagram shows video broadly, not specifically Video Compression.

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## How Video Compression works

Modern encoders exploit similarity within a frame and across neighboring frames, then quantize transformed prediction errors and entropy-code the result. Intra pictures provide self-contained reference points, while predicted pictures reduce size by depending on other decoded images. Lossless modes preserve sample values; delivery formats generally use controlled loss to reach practical rates. Compression runs between acquisition or editing masters and storage or distribution, with decompression required at playback and many analysis stages.

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## Key facts

1. 1Long prediction groups can improve compression efficiency, but they increase random-access work and allow corruption from a damaged reference picture to affect later frames.
2. 2Rate control may target a fixed quality, an average rate, or a constrained transmission rate; each mode distributes bits differently across simple and complex scenes.
3. 3Repeated lossy encodes compound quantization damage, especially around text, grain, and sharp edges, so derivatives should be generated from a retained master rather than one another.

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## When Video Compression matters

Choose codec settings by balancing visual quality, bitrate, encoding cost, and decoder support. Aggressive lossy compression saves bandwidth but can introduce artifacts that later re-encoding amplifies.

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## Common use cases for video

These examples cover video broadly, not specifically Video Compression.

* Preparing uploaded video for web, mobile, connected-TV, social, or editorial playback.
* Creating clips, thumbnails, captions, alternate aspect ratios, and adaptive renditions.
* Normalizing camera, screen-recording, and user-generated files into predictable outputs.

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## Working with video

This guidance covers video broadly, not just Video Compression.

A demuxer separates tracks from the container, decoders turn compressed streams into frames or samples, and filters apply spatial or temporal changes. Encoders compress the transformed tracks before a muxer writes the chosen output container.

Video compatibility is the product of codec, container, profile, level, frame rate, color, audio, and subtitles. Validate the complete output on target devices because a playable file on one decoder may fail or look different on another.

### What you gain

* Standardized derivatives make diverse source files playable on target devices.
* A retained master can feed many resolutions, aspect ratios, codecs, and channels.
* Automated inspection and transformation make large upload volumes consistent.

### What it costs

* More efficient codecs can lower bitrate at similar quality but usually cost more compute and may have narrower support.
* Higher resolutions and frame rates preserve more detail and motion while increasing processing and delivery requirements.
* Fast encoding settings improve throughput but can produce larger files or lower quality than slower analysis.

### Before production

1. 1Inspect codec, container, dimensions, frame rate, color, audio, and subtitle tracks.
2. 2Test visual quality and playback support across the slowest and oldest target devices.
3. 3Preserve a suitable master before applying lossy, destructive, or delivery-specific changes.

[← Video Compositing](/glossary/video-compositing.md)[Video Content Management System →](/glossary/video-content-management-system.md)

More in video

* [Video Color Space](/glossary/video-color-space.md)
* [Video Completion Rate](/glossary/video-completion-rate.md)
* [Video Compositing](/glossary/video-compositing.md)
* [Video Controls](/glossary/video-controls.md)
* [Video Decoding](/glossary/video-decoding.md)
* [Video Embed](/glossary/video-embed.md)

[All 505 terms](/glossary.md)

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