This chapter contains an overview of Video Server Toolkit (VST), which is a software product used by application developers and systems integrators to enable a SGI Origin server or O2 workstation to be used as a video server. VST provides real-time, frame-accurate recording and playback of broadcast-quality digital media data.
 | Note: The term Origin in this document refers to Origin200, Origin2000, and Onyx2 servers. Where there is a distinction, the pertinent product name is used. |
The following topics are discussed in this chapter:
Digital media data is brought into VST by recording it from a live feed or a videotape deck, retrieving it from a StudioCentral 2.0 archive system, or copying it from a file. The data can then be played out to a broadcast system, a video port, or a videotape deck; sent to an MPEG-2 decoder for playout; or transferred to a StudioCentral 2.0 archive system for storage and distribution.
VST can be automatically controlled by an application or through the use of a broadcast system automation controller, which can control video servers using serial control protocols, such as the Louth VDCP or Odetics VDR protocols, or an edit controller that can control a VTR using the Sony RS-422 VTR protocol.
VST can also be manually controlled by using the VST graphical user interface or can be controlled by an application using the Multiple-Unit Video Computer Protocol (MVCP).
This functionality is shown in Figure 2-1.
The graphical user interface (GUI), which is used to control VST, was designed as both a demonstration of the capability of VST and a beginning point from which broader graphical applications can be developed. The GUI consists of screens that are used to record and play digital data, determine status information, and manage digital media data stored in VST.
The GUI screen that is used to record and play digital media data is the VST Media Control Panel (mcpanel), which is shown in Figure 2-2. The control panel is similar in function to a standard videotape player or recorder. For example, there are buttons in the control panel to cue the video, play it, stop the playback, and so on.
The graphical user interface is described in Chapter 3, “Using the Video Server Toolkit GUIs.” The MVCP protocol, which was used to implement the VST GUI, is described in Appendix A.
The VST software provides scalability and maximum flexibility, while enabling real-time, frame-accurate control of digital media. The software includes the following:
Core software, which provides the basic VST functionality for playback and recording of digital data.
Control interface modules, which provide device-dependent code. For example, there is a control interface module that contains the code that is specific to a Louth automation controller.
Media device interface modules, which contain format-dependent code that provides access to the ports over which media is played and recorded. For example, there is a media device interface module that contains the code that supports the Vela Research SCSI-attached MPEG-2 decoder.
Format interface modules, which provide handlers for accessing specific digital media storage formats. For example, there are format interface modules for the VST variable-frame format, the MPEG-2 stream-based format, and the DVCPRO Data Interchange Format (DIF).
Figure 2-3 shows the primary software components in VST.
The remainder of this section discusses the software components shown in Figure 2-3.
Digital media data that Video Server Toolkit (VST) processes for playout and recording is stored in one or more clip caches. Each unit of data that is stored in a clip cache (for example, a movie) is called a clip.
Clips can be added to the cache by:
Using VST to record the clip
Generating the clips elsewhere and adding them to the cache
Transferring clips from a StudioCentral 2.0 archive system
Clips can be transferred from the clip cache into a StudioCentral 2.0 archive system for storage.
The core software provides the basic VST functionality for playback and recording of digital data. It utilizes the IRIX operating system as well as portions of the SGI Digital Media Libraries.
The core software provides the following basic functionality:
Archive management, which oversees the transferring of assets into and out of a StudioCentral 2.0 archive system
Clip cache management, which maintains persistent information about the media that is either stored in the clip cache or is in the process of being transferred into or out of it
Controller management, which links one or more external control protocol modules (for example, Louth) to the internal VST processing logic
Configuration management, which automatically configures the VST software according to the hardware capabilities of the system on which it runs
VST provides a core library that supports external interface modules, dynamic shared objects (DSOs) that contain the code specific to a given external entity. When VST is started, the VST software loads and initializes all external interface modules it locates so that the modules can be used.
VST has an archive interface that enables VST to retrieve clips from, and store them in an archive asset repository. VST transfers the media to and from an archive system using the Asset Transfer Service (or ATS), communicating with ATS using the FTP-like ATS protocol.
Archive interface modules contain the code that is specific to a StudioCentral 2.0 archive system. These modules provide the support that is needed to locate a given clip in the StudioCentral 2.0 archive system and bring it into VST, and to store a clip from VST in the StudioCentral 2.0 archive system.
Control interface modules allow various automation controllers and digital media applications to control the use of VST. These modules translate to and from external control protocols.
The following control interface modules are provided:
The Louth Video Disk Communications Protocol defined by Louth Automation. This control protocol provides control of VST over RS-232, RS-422, or TCP/IP. The VST's Louth interface module supports back-to-back play and record (subject to restrictions imposed by the video I/O port capabilities) and archive management.
The Sony RS-422 VTR (also called, 9-pin or P2) protocol. VST supports this protocol through a full-featured VTR deck-emulation mode that includes frame-accurate insert editing and variable-speed shuttle.
Multiple-Unit Video Computer Protocol (MVCP) defined by SGI. This control protocol provides full-featured control of VST through TCP/IP. This control interface module supports archive management, multiple-unit control, and event monitoring, and provides access to advanced features of SGI devices.
The Odetics protocol is a Video Disk Control Protocol similar in purpose to the Louth VDCP. Unlike Louth, it is built upon the foundation of the Legacy Sony RS422 VTR Control Protocol, with which it shares many commands and features. Odetics adds to the Sony protocol commands specific to Video Disk Recorders, such as back-to-back playout and recording and clip management operations.
Storage device interface modules provide access to the storage systems on which the clip cache resides. Currently, there is a storage device interface module for the IRIX XFS filesystem.
Format interface modules provide handlers for accessing specific digital media storage formats. VST currently provides format interface modules that support the following:
Media device interface modules provide access to the ports over which the media is played and recorded (that is, the media ports). Each type of I/O port typically has its own media device interface module.
VST has media device interface modules for the following:
SGI Video Library. This media device interface module supports the Digital Video Option (DIVO) on Origin servers and the video port on O2 workstations.
DIVO enables broadcast-quality video and embedded audio, and is used for the recording and playback of uncompressed and Rice compression formats.
DVC/DIVO is the DVCPRO version of the DIVO card. It performs all the functions of the DIVO card and DVCPRO.
DVB-ASI (Digital Video Broadcast Asynchronous Serial Interface) protocol
The O2 video port is used for playback and recording of the motion JPEG format, and is suitable for a test or development environment.
Note: The O2 video port is usually referred to as mvp (multiport video processor) or O2Video.
Vela Research four-port analog decoders. This media device interface module enables the playback of MPEG-2 format data on Origin servers and O2 workstations.
V-LAN transmitters. This media device interface module enables frame-accurate capture from, and lay-down to, videotape decks.
Diaquest. Direct Sony 422 control of videotape decks; used in the same way as V-LAN.
The Viewgraphics MediaPump is a PCI-based, DVB-compliant adaptor board. It multiplexes MPEG 2 transport streams and transmits them over coaxial cables using the DVB-ASI (Digital Video Broadcast Asynchronous Serial Interface) protocol.
For more information, see the Video Server Toolkit Installation and Administration Guide .
The DVCPRO compression algorithm compresses four video frames into one frame. This compression format is useful for transporting video data across networks, such as between video decks. DVCPRO-compressed frames in 1 times mode can be displayed normally. The following section describes how to display DVCPRO-compressed frames in 4 times mode
The Serial Digital Transport Interface (SDTI) is a video networking protocol that allows arbitrary data to be packeted and transmitted over the SMPTE-259M Serial Digital Interface (SDI). VST supports playback and recording of DVCPRO (DIF) over SDTI at 1 times and 4 times normal speed. When recording SDTI/DVCPRO using DIVO-DVC, the incoming signal can be looped to the output (EE mode) in either 1x or 4x mode.
Logical units enable media ports to play and record clips. Each VST unit can be thought of as a logical videotape recorder (VTR) transport that is capable of loading, cueing, playing, and recording clips using a specific media port.
Logical units are created automatically by VST when the VST GUI or an automation controller is used. When the MVCP protocol is used, a command requests that a unit be created or that a unit created by another control connection be used.
There is normally a one-to-one relationship between a control connection to VST and a VST logical unit, and between a logical unit and a media port. This is shown in Figure 2-4.
A single unit can also be controlled by multiple control ports. For example, two tightly integrated applications might control a single unit, where each application would have its own control port. This is shown in Figure 2-5.
A media port can be controlled by multiple logical units. For example, an application with one control connection and two units could be cueing one clip while playing out another, enabling back-to-back playout of clips when allowed by the media format. This example is shown in Figure 2-6.
If a media port supports multiple logical units, the sharing is subject to the device-sharing characteristics of that port.
A VST hardware configuration consists of the following components:
| VST Server | O2, O200 with GIGAchannel, O2000 | |
| Storage | Internal ultraSCSIs or external CIPRICO 7000 RAIDS | |
| Internal Devices |
| |
| External Devices |
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A typical hardware configuration is shown in Figure 2-7.
The Video Server Toolkit (VST) server can be an Origin200 or Origin2000 Scalable Symmetric Multi-Processing (S2MP) server, or an O2 workstation.
The Origin servers provide massive processing, storage, and throughput capabilities to satisfy even the largest production requirements. They are built from a scalable node architecture, enabling small configurations that can be incrementally upgraded to the larger configurations. Each Origin server can be configured as a single module or as multiple modules with a single system image.
The Origin servers provide:
Playback and recording of uncompressed and Rice compression video data with the Digital Video Option (DIVO) card.
DVCPRO, Data Interchange Format (DIF), a compression algorithm that compresses four video frames into one frame. This compression format is useful for transporting video data across networks, such as between video decks.
Playback of MPEG-2 (system and transport streams) data with the Vela Research SCSI-attached decoder.
GIGAchannel expansion box for the O200, which allows the addition of up to five DIVO boards.
DVB-ASI is a PCI-based, DVB-compliant adaptor board. It multiplexes MPEG 2 transport streams and transmits them over coaxial cables using the DVB-ASI (Digital Video Broadcast Asynchronous Serial Interface) protocol.
The O2 workstation provides a low-cost, entry-level video server platform that supports some but not all of the features supported by the Origin platform.
The O2 workstation provides:
The VST disk storage holds the XFS real-time filesystems that contain the movies, trailers, commercials, and other digital media data stored in the clip cache. The descriptive information about VST clips, for example, clip names, duration, edit points, and so on, are also stored on these filesystems.
The VST storage system supports the use of scalable storage to enable the total disk space to range from only a few gigabytes to hundreds of terabytes or more. The type of disk storage that is used depends upon several factors, including the number and size of stored clips, the use of RAID, and the required availability (uptime) of the system.
Three different types of disk storage are available:
Normal XFS filesystems residing on a single disk drive. This type of disk storage does not provide redundancy.
Standard disk storage, sometimes called RAID-0, in which several disk drives are striped into XLV logical volumes. This type of disk storage does not provide redundancy but it does provide higher bandwidth than XFS on a single disk drive.
RAID storage, such as RAID-3 and RAID-5, which provides high-availability, redundant digital storage.
VST supports the use of the following external devices:
Vela Research 4-port MPEG-2 decoders, used for the playback of MPEG-2 format data. Vela decoders are connected to the VST server through a SCSI connection.
V-LAN transmitters, used to control a videotape deck for frame-accurate capture and lay-down. A V-LAN transmitter is connected to a VST server through an RS-422 serial port connection.
Broadcast system automation controllers that use, among others, the Odetics and Louth Video Disk Communications Protocol, defined by Louth Automation. Automation controllers are connected to the VST server through an RS-422 serial connection or a TCP/IP Ethernet connection.
DVB-ASI, from Viewgraphics, is a PCI-based, DVB-compliant adaptor board. It multiplexes MPEG 2 transport streams and transmits them over coaxial cables using the DVB-ASI (Digital Video Broadcast Asynchronous Serial Interface) protocol. For more information, see Chapter 8, “Installing the DVB-ASI Adapter Board,” in the Video Server Toolkit Installation and Administration Guide .
Edit controllers, including Panasonic AJ-A850, Buf VTC4000/RM4000, and the edit control portion of the Sony DVW 500 digital Betacam deck.
For more information about installing these devices for use with VST, see the Video Server Toolkit Installation and Administration Guide .
For a complete list of external devices that interface with VST, see the release notes.
Video Server Toolkit supports the use of the following internal devices:
DIVO, a CCIR 601 format digital video board that provides two sets of incoming and outgoing video/audio signals and lossless 2:1 compression using the Rice format. DIVO enables you to choose square or rectangular pixels, and compatibility with PAL and NTSC.
DIVO plus DVCPRO,. which compress four video frames into one frame using cosine compression.
MVP, which provides standard, uncompressed, analog or CCIR 601 audio/video using RCA jacks, S-Video jacks, stereo input and output audio, the choice of using square or rectangular pixels, and compatibility with PAL and NTSC.