Core Video is the video processing model employed by

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

. It links the process of decompressing frames from a video source to the rest of the Quartz technologies for image rendering and composition. Both QuickTime X and QuickTime 7 depend on Core Video.

Overview

Core Video provides both a buffering model and a playback synchronization solution within its processing pipeline. A video source provides a decompressed data stream to be rendered as images within a visual context in Quartz 2D. Core Video can be thought of as the link between this video source and its display context. Rendered images can be further processed by

Core Image Core Image is a pixel-accurate, near-realtime, non-destructive image processing technology in Mac OS X. Implemented as part of the QuartzCore framework of Mac OS X 10.4 and later, Core Image provides a plugin-based architecture for applying fil ...

before being composed into a final scene with

Quartz Compositor Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other ren ...

. As part of the composition process, Core Video maintains a ''frame buffer'', keeping a pool of rendered, composed frames ready for playback. To ensure smooth playback, Core Video uses a high-priority thread to maintain its frame buffer. This ''display link'' runs independently from the application which invokes video playback, and it compensates for different display refresh rates and latency. Because QuickTime 7 employed Core Video, it was the first version of QuickTime to implement the rendering capability of Quartz. Previous versions of QuickTime used

QuickDraw A quickdraw (also known as an extender) is a piece of climbing equipment used by rock and ice climbers to allow the climbing rope to run freely through protection such as a bolt anchors or other traditional gear while leading. A quickdr ...

for rendering. Although Core Video typically interacts with QuickTime, it can interact with any video source. Core Video benefits from graphics processor (GPU) rendering and composition provided by Quartz GL, Core Image, and

Quartz Extreme Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other render ...

, since final playback is composed on an OpenGL surface.

History

Although Core Video was introduced with the release of

Mac OS X v10.4 Mac OS X Tiger (version 10.4) is the 5th major release of macOS, Apple's desktop and server operating system for Mac computers. Tiger was released to the public on April 29, 2005 for US$129.95 as the successor to Mac OS X 10.3 Panther. Som ...

, it is included in the installation of QuickTime 7 on Mac OS X; thus, Core Video is available for Mac OS X 10.3.9 with QuickTime 7 installed as well. In Mac OS X 10.4, Core Video is implemented as part of the QuartzCore framework; in Mac OS X 10.5 and later, it resides in its own framework.

References

{{macOS macOS APIs QuickTime