VLGETNODE(3dm)VLGETNODE(3dm)NAME
vlGetNode, vlAddNode, vlRemoveNode - VL node handling routines
SYNOPSIS
#include <dmedia/vl.h>
VLNode vlGetNode(VLServer svr, int type, int class, int number);
int vlAddNode(VLServer svr, VLPath path, VLNode node);
int vlRemoveNode(VLServer svr, VLPath path, VLNode node);
DESCRIPTIONvlGetNode returns a handle to a VL node with the specified
characteristics. The node handle can be used in subsequent calls to
vlCreatePath(3dm) or vlSetControl(3dm). Nodes are used to construct
paths which tell the system how to interconnect video data streams. The
source and drain of a video stream, as well as intermediate filters
affecting data flowing between them, are types of nodes. A path may have
multiple drain nodes, and in some cases, multiple source nodes. Nodes
have various controls associated with them which may change the behavior
of the node or any path containing that node.
vlAddNode adds node to a path which has been created with
vlCreatePath(3dm) but not yet instantiated by vlSetupPaths(3dm).
vlAddNode can be called multiple times for a given path until
vlSetupPaths is called. Adding multiple nodes of type VL_SRC to a path
implies that blending is desired, however no blending will take place
unless a VL_BLENDER node is added to the path. If multiple VL_DRN nodes
are added to the path, they will all receive the same output.
vlRemoveNode removes the specified node from the given path.
Adding a VL_DEVICE node to a path gives that path access to global device
controls which may affect all paths on the device.
A node is specified by three parameters, the type, class, and number.
The type parameter specifies the function of the node in a path. There
are four types of nodes:
VL_SRC the source from which a video stream will originate.
VL_DRN the destination, or drain, where video will be sent.
VL_INTERNAL a mid-stream filter such as a blender.
VL_DEVICE a special node used to manipulate controls which are
global to the video device and shared by all paths.
The class parameter identifies the type of system resource associated
with the node. There are five classes of nodes:
VL_VIDEO a hardware video port. If the type is VL_DRN then the
node specifies a video output. If the type is VL_SRC
then the node specifies a video input. All video
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VLGETNODE(3dm)VLGETNODE(3dm)
devices have at least one of these.
VL_GFX specifies a direct connection between a video device
and a graphics frame buffer. Video data may be
manipulated in the frame buffer using standard graphics
operations. This class of node is only available with
the Sirius Video option.
VL_MEM a memory buffer which can be used to send or receive
video data.
VL_SCREEN specifies a direct connection between a video device
and a graphics display device. This differs from
VL_GFX in that the video data does not interact
directly with the graphics frame buffer and can not be
affected with standard graphics routines. This class
of node is available with the Galileo/IndyVideo or
Impact Video options.
VL_TEXTURE specifies graphics hardware which can transfer video
data directly to or from a texture buffer. This class
of node is available with the Sirius or Impact Video
options.
VL_BLENDER a filter that can affect data flowing between the
source and drain. Internal nodes are available on some
devices to control blending multiple sources. The type
of a blend node should be specified as VL_INTERNAL.
VL_CSC a realtime colorspace converter which can be used to
convert the video data if the destination requires a
different colorspace than the source. Note that source
and drain nodes may support some conversions directly,
in which case a VL_CSC node may not be necessary in the
path. The type of a colorspace converter should be
specified as VL_INTERNAL. This class of node is only
available with the Impact Video option.
VL_FB a frame buffer which can be inserted in the path to
freeze the video data. Note that some nodes have an
inherent freeze capability, in which case a frame
buffer node may not be necessary on the path. The type
of a frame buffer node should be specified as
VL_INTERNAL. This class of node is only available with
the Impact Video option.
The number parameter is used to differentiate among multiple instances of
the same class and type a particular device might support. The value
usually corresponds to the numbering of video connectors on the board. If
VL_ANY is specified for number, the selection will be based on the
default for that node, which may be changed using videopanel(1).
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VLGETNODE(3dm)VLGETNODE(3dm)
Not all classes of nodes are available on all video devices. The
complete set of nodes available for a particular device may be determined
using vlGetDeviceList(3dm).
RETURN VALUE
Upon successful completion, vlGetNode returns a node handle and vlAddNode
and vlRemoveNode return VLSuccess. Otherwise, a value of -1 is returned
and vlErrno is set to indicate the error.
SEE ALSOvlCreatePath(3dm), vlRemoveNode(3dm), vlSetControl(3dm),
vlGetControl(3dm), vlCreateBuffer(3dm), vlGetControlInfo(3dm),
vlGetDeviceList(3dm)
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