Indigo2 IMPACT workstation video capabilities are provided by the Video Library and Indigo2 Video option board for Indigo2 IMPACT. The board provides video input and output for Indigo2 workstations equipped with IMPACT graphics.
This chapter introduces
Video Library capabilities
VL system software architecture
VL architectural model of video devices
VL programming model
Indigo2 Video formats
For an introduction to video, see Appendix A, "Video Basics."
The Video Library provides a software interface to the Indigo2 Video board for Indigo2 IMPACT, enabling applications to
display live video in a window
capture live video to system memory
encode graphics to video in real time
produce high-quality single-frame video output
The Video Library (VL) is a collection of device-independent and device-dependent C language calls for Silicon Graphics workstations equipped with video options. The VL provides generic video tools, including simple tools for importing and exporting digital data to and from Silicon Graphics systems, as well as to and from third-party video devices that adhere to the Silicon Graphics architectural model for video devices. Video tools are described in the Media Control Panels User's Guide, which you can view using the IRIS® InSight[tm] viewer; similar applications are supplied in source-code form as examples in the 4Dgifts directory (/usr/people/4Dgifts/examples/dmedia/video/vl and /usr/people/4Dgifts/OpenGL).
The VL works with other Silicon Graphics libraries, such as the OpenGL® and IRIS Graphics Library[tm] (GL). The VL does not depend on the X Window System[tm], but you can use X Window System libraries or toolkits to create a windowing interface.
The VL allows programs to get events 60 times per second on a quiescent system; it also enables programs to share resources or to gain exclusive use of resources. It supports input and output of video data to or from locked-down memory at the nominal frame rate. The VL provides an API that enables applications to
The software for the Indigo2 Video board for Indigo2 IMPACT includes a graphical user interface that makes it convenient to access VL capabilities. Features of this panel, /usr/sbin/vcp, are referred to in the course of this guide.
This section describes features of these VL system components and tools:
video daemon
generic video tools
library and header files
Figure 1-1 diagrams the interaction between the VL, the video daemon, the kernel, the hardware, and the X Window System server.
The VL communicates with the IRIX kernel for device initialization, vertical retrace, setup, and maintenance of any device-supported direct memory access (DMA).
Besides these components, the VL includes a collection of applications that support device configuration and control setting and retrieval, generic tools that display video on a workstation, and video control panels.
The video daemon, /usr/etc/videod, which has device-dependent and device-independent portions, handles video device management and status information.
Management that the video daemon performs includes:
Multiple client access to multiple devices
The library supports connections from multiple client applications and manages their access to a limited number of video devices.
Dispatching events
As events are handled and noted by devices, the daemon notifies applications that have expressed interest in those events.
Handling events
As events are generated by the various devices, the daemon initiates any action required by an event before it hands the event off to interested applications.
Maintaining exclusive use
Types of data or control usage for video clients in a Video Library application are Done Using, Read-only, Lock, and Shared. These usage levels apply only to write access on controls, not read access. Any application can open and read the control's values at any time.
Client cleanup on exit
When a client exits or is terminated abnormally, its connection to the daemon is broken; the daemon performs any cleanup required of the system. Any exclusive-use modes that have been set are cleared; interested clients are notified that the device is no longer in exclusive use. Controls set by the client might persist, but are not guaranteed to remain after the client closes the connection.
Status information for which the video daemon is responsible includes:
System status of video devices
The video devices installed in a system can be queried as to availability and control status.
Video positioning (offset) information
Control setting and retrieval
Device-independent and device-dependent controls are set and retrieved through the video daemon.
The generic video tools include:
The vlinfo, vidtomem, and memtovid tools are command-line tools. In addition to their reference pages, these tools have explanations in the Media Control Panels User's Guide, which you can view using the IRIS InSight viewer. Similar applications are supplied in source-code form as examples in the 4Dgifts directory (/usr/people/4Dgifts/examples/dmedia/video/vl and /usr/people/4Dgifts/examples/OpenGL).
The two central concepts for VL are:
VL routines explained in this chapter enable you to build a fully connected topology of sources and drains.
A path defines the useful connections between video sources and video drains. Figure 1-2 shows a simple path in which a frame from a videotape is displayed in a workstation window.
Figure 1-3 shows a more complex path with two video sources: a frame from a videotape and a computer-generated image are blended and output to a workstation window. This path is set up in stages.
The VL recognizes five classes of objects:
controls, or parameters, that modify how data flows through nodes; for example:
video device parameters, such as blanking width, gamma value, horizontal phase, sync source
video data capture parameters
blending parameters
buffers, for sending frame data to and receiving frame data from host memory; the VL buffers are implemented as ring buffers containing a number of blocks; each maintains a pointer, a size, and pointers to the head (oldest) and tail (newest) valid data
Data transfers fall into two categories:
transfers involving memory (video to memory, memory to video), which require setting up a ring buffer
transfers not involving memory (such as video to screen and graphics to video), which do not require a ring buffer
Syntax elements are as follows:
VL types and constants begin with uppercase VL; for example, VLServer
VL functions begin with lowercase vl; for example, vlOpenVideo()
For the two categories of data transfer, based on the VL programming model, the process of creating a VL application consists of these steps:
Open a connection to the video daemon (vlOpenVideo()); if necessary, determining which device the application will use (vlGetDevice(), vlGetDeviceList()).
Specify nodes on the data path (vlGetNode()).
Create the path (vlCreatePath()).
(Optional step) Add more connections to a path (vlAddNode()).
Set up the hardware for the path (vlSetupPaths()).
Specify path-related events to be captured (vlSelectEvents()).
Set input and output parameters (controls) for the nodes on the path (vlSetControl()).
For transfers involving memory, create va ring buffer to hold data for memory transfers (vlGetTransferSize(), vlCreateBuffer()).
For transfers involving memory, register the buffer (vlRegisterBuffer()).
Start the data transfer (vlBeginTransfer()).
For transfers involving memory, get the data (vlGetNextValid() or vlGetLatestValid(), vlGetActiveRegion(), vlPutFree()) to manipulate frame data.
Clean up (vlEndTransfer(), vlDeregisterBuffer(), vlDestroyPath(), vlDestroyBuffer(), vlCloseVideo()).
Table 1-1 lists calls explained in this chapter.
Table 1-1. Video Library Calls for Data Transfer
All Transfers | Transfers Involving Memory | Setting Controls |
|---|---|---|
vlOpenVideo() | vlGetTransferSize() | vlSetControl() |
The Indigo2 Video board for Indigo2 IMPACT translates video signals into a form usable by the Indigo2 workstation. It also does the reverse, translating graphics from the workstation display into video signals. This section describes the Indigo2 Video board's I/O interface.
The Indigo2 Video board's native video format is YUV 4:2:2. The board also supports 32-bit RGB video data. Data coming from or going to the Indigo2 Video board for Indigo2 IMPACT is always ordered top to bottom. The Indigo2 workstation, on the other hand, commonly stores image data with lines ordered bottom to top. Both the Indigo2 workstation and the Indigo2 Video board for Indigo2 IMPACT store pixels from left to right within lines.
The Indigo2 Video board for Indigo2 IMPACT uses 32-bit RGB format for single frame output, and it is produced by some of the video capture convenience routines. The format of these pixels is shown in Figure 1-4.
In Figure 1-4, the bits are numbered from right to left, with the least significant (rightmost) bit numbered zero.
You can use the capabilities of the Indigo2 Video board to record video signals in composite or S-Video format. For information on the requirements for recording to and from video, see the Indigo2 Video Owner's Guide. For information on videotape formats, see "Videotape Formats" in Appendix A.