Core Video
Encyclopedia
Core Video is the video processing model employed by Mac OS X
. 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.
. 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
before being composed into a final scene with Quartz Compositor
. 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
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, since final playback is composed on an OpenGL surface.
, 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.
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
. It links the process of decompressing frames from a video source to the rest of the Quartz technologies
Quartz (graphics layer)
Quartz specifically refers to a pair of Mac OS X technologies, each part of the Core Graphics framework: Quartz 2D and Quartz Compositor. It includes both a 2D renderer in Core Graphics and the composition engine that sends instructions to the graphics card...
for image rendering and composition. Both QuickTime X and QuickTime 7
QuickTime
QuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
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 2DQuartz 2D
Quartz 2D is the primary two-dimensional graphics rendering API for Mac OS X, part of the Core Graphics framework.-Overview:Quartz 2D is available to all Mac OS X application environments, and provides resolution-independent and device-independent rendering of bitmap graphics, text, and vectors...
. 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
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 filters and effects within the Quartz graphics rendering...
before being composed into a final scene with Quartz Compositor
Quartz Compositor
Quartz Compositor is the windowing system in Mac OS X. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other renderers in the Quartz technologies family...
. 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
QuickDraw
QuickDraw is the 2D graphics library and associated Application Programming Interface which is a core part of the classic Apple Macintosh operating system. It was initially written by Bill Atkinson and Andy Hertzfeld. QuickDraw still exists as part of the libraries of Mac OS X, but has been...
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, since final playback is composed on an OpenGL surface.
History
Although Core Video was introduced with the release of Mac OS X v10.4Mac OS X v10.4
Mac OS X v10.4 Tiger is the fifth major release of Mac OS X, Apple's desktop and server operating system for Macintosh computers. Tiger was released to the public on 29 April 2005 for US$129.95 as the successor to Mac OS X Panther , which had been released 18 months earlier...
, 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.