O

object

A single, run-time instance of a system-defined object type. Objects visible in user mode include process, thread, section, file, event, semaphore, key, timer, port, object directory, symbolic link, I/O completion port, and token objects.

Many user-mode objects are implemented through the use of a corresponding kernel-mode object, including processes, threads, events, semaphores, and timers.

Kernel-mode-only objects include APC, DPC, device queue, interrupt, mutex, driver, device, adapter, controller, and stream file objects.

See also object type and opaque.

object directory object

A type defined by the Object Manager and used to implement hierarchical object names.

Note that file system directories are implemented as file objects, not as object directory objects.

object type

An opaque data structure that defines a protected entity implemented and manipulated by the operating system. For example, the system service that reads a file operates on an open file object.

Every user-visible object has:

• A type (whose name must be unique).
• Two parts:

A header that is operated on by the Object Manager

A body that is operated on by type-specific system services

• A set of standardized rules for object creation, deletion, protection, access, management, and naming

User-visible objects can be implemented using kernel-mode objects.

Kernel-mode objects are visible to (and, except for certain fields in driver and device objects, directly accessible only by) the executive component that defined a given object type. They are indirectly accessible to other kernel-mode code through the type-specific support routines exported by the defining component. For example, KeInitializeDeviceQueue operates on device queue objects.

See also opaque.

OBMC

Overlapped Block Motion Compensation. An algorithm in H.263 that obtains motion vectors from blocks next to the current macroblock and uses them with the current macroblock to achieve a more accurate predication and a smaller bitstream.

off-host IDCT

In DirectX® VA IDCT is performed on the accelerator with the host decoder passing macroblocks of inverse transform coefficients to the accelerator.

See also IDCT

off-screen memory

Video memory whose contents do not appear on the video display. Off-screen memory can be used for double buffering, a technique in which a complex graphics image that requires numerous graphics operations can be completely rendered before it is displayed. After each image has been displayed, another image can be constructed in the same way, providing an effective way to achieve animation.

OLE

Object linking and embedding. A way to transfer and share information among applications. OLE is based on the COM programming model and binary standard.

OnNow

A computer industry initiative to make computers more power efficient, reducing startup time and adding the ability to shut off idle devices.

opaque

Pertains to any data structure, including a system-defined object, that is defined with a deliberately hidden internal structure known only to the executive component that defined the type. However, the defining component supplies system services and, usually, kernel-mode support routines to manipulate opaque objects. User-mode data types also can be opaque.