Supported Hardware


Windows XP Professional supports a broad range of hardware, including system buses such as Universal Serial Bus (USB) and Institute of Electrical and Electronics Engineers (IEEE) 1394. Other system buses are also supported, in addition to devices such as network adapters and other internal adapters, modems, digital audio devices, DVD, Human Interface Devices (HID), still-image devices, smart cards, and video-capture devices.

Universal Serial Bus

Universal Serial Bus (USB) is a standards-based, external serial bus for the computer. USB is universal in that many types of peripheral devices can be connected to a computer by plugging them into USB ports, using standard USB cables, connectors, and sockets. USB fully supports Plug and Play, which means peripheral devices can be plugged in and unplugged while the computer is running. The operating system immediately detects a device that is plugged in and tries to load device drivers for the device.

USB hubs can be used to connect several devices to one computer. A hub provides multiple USB ports for Plug and Play devices. The hub is then plugged into the computer, directly or through another hub, using a single USB cable.

Windows XP Professional has built-in support for many USB devices (see USB Devices later in this chapter). When a user plugs in a USB device for which Windows XP Professional does not have built-in support, a dialog box is displayed that allows the user to manually point the Plug and Play subsystem to the location of the device drivers for that device (typically independent hardware vendor (IHV)-provided drivers on a floppy disk or CD ROM).

USB has the following advantages:

  • All USB devices connect to the computer using either the standard USB port or an A connector.

  • A USB controller supports up to 127 devices. Hubs are used to obtain ports in addition to those supported by the root hub.

  • USB supports hot plugging plugging in or unplugging a USB device while the computer is running.

  • USB supports the selective suspend feature, which allows USB device drivers to selectively shut down their devices when they detect that the devices are idle. When the device is put back in use, such as a user moving a USB mouse, the driver turns the device back on. This is particularly important for power management of mobile computers.

USB Topology

As illustrated in Figure 9-2, USB uses a tiered topology, so you can simultaneously attach up to 127 devices to the bus. USB supports up to seven tiers, including the root tier and five non-root hubs. The lowest tier supports only a single non-hub device. Under the USB specification, each device can be located up to 5 meters from the hub or port it is connected to.

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Figure 9-2: USB tiered topology

There are three types of USB components:

  • Host controller. Also known as the root, the root tier, or the root hub, the host controller can be built into the motherboard of the computer or installed as an add-in CardBus or PCI card in the computer to gain additional ports and bandwidth. The host controller controls all traffic on the bus and also functions as a hub.

  • Hub. Provides multiple ports, for attaching devices to the USB bus. Hubs are also responsible for detecting devices that are plugged in or unplugged, and for providing power for attached devices. Hubs are either bus-powered, drawing power directly from the USB bus, or self-powered, drawing power from an external AC adapter. Bus-powered hubs are capable of providing 100 milliamperes (mA) of power per port for attached devices, and can provide a maximum of four ports for devices to be plugged into. Self-powered hubs, on the other hand, typically provide 500 mA of power per port, and can provide more than four ports. Hubs can be stand-alone devices, or they can be integrated into other devices such as keyboards and monitors.

  • Device. A USB device, which is attached to the bus through a port. A USB device can be any kind of peripheral device, such as a keyboard, mouse, game controller, printer, and so forth. Certain USB input devices such as keyboards and mice require only 100 mA of power to function. Thus, they can be plugged into both bus-powered and self-powered hubs, in addition to being plugged directly into a root port. Other devices such as printers, scanners, storage devices, and video-conferencing cameras might require 500 mA of power to function. These kinds of devices can only be plugged into root ports or self-powered hubs. If the device requires more than 500 mA of power, it includes a wall plug provided by the vendor for power.

USB Devices

A USB device typically implements a single function, for example, as a keyboard or mouse does. However, a USB device can also implement multiple functions, such as scanning, printing, and faxing. When such a multi-function device, or USB composite device, is plugged in, the operating system enumerates all the functions in the device, and loads device drivers for each function.

A USB device might also include a built-in hub, to enable additional devices to be plugged into it. Such a device is known as a USB compound device.

Each USB device contains configuration information that describes its capabilities and resource requirements. This information is read from the device by the operating system during the enumeration process.

USB devices are recognized, initialized, and ready for use when plugged in. No additional installation or configuration steps are necessary.

Windows XP Professional features built-in support for USB device types such as:

  • Hubs

  • Uninterruptible power supply (UPS) devices

  • Input devices, such as keyboards, mice, and other pointing devices

  • Game controllers, such as joysticks and game pads

  • Printers

  • Storage devices such as hard disk drives, CD ROM drives, high-density disk drives, and compact flash readers

  • Speakers and microphones

  • Scanners

  • Still image cameras

  • Video-conferencing cameras (also known as webcam cameras)

  • Modems

  • USB-to-Ethernet network adapters

Windows XP Professional supports only devices that are compliant with applicable USB device class specifications as developed and published by the USB Implementers Forum. For more information about USB specifications, see the USB link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

The only exception to this rule is USB-to-Ethernet adapters, which must be compliant with the Microsoft Remote Network Driver Interface Specification (NDIS) in order to benefit from built-in support in Windows XP Professional. For more information about Remote NDIS, see the Remote NDIS link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

Data Transfer Types and Rates Supported by USB

USB supports two different data transfer modes: isochronous and asynchronous modes. Asynchronous mode uses three asynchronous data transfer types: interrupt, control, and bulk. Isochronous mode uses the isochronous transfer type.

The USB host controller determines the data transfer rate and the priority assigned to a data stream. USB supports the following maximum data transfer rates, depending on the amount of bus bandwidth a device requires:

Asynchronous transfer mode

An asynchronous transfer employs a handshake system and allows data streams to be broken at random intervals. The three asynchronous data transfer types are described below.

Interrupt

Interrupt transfers reserve bandwidth and are guaranteed access to transfer data at the established rate. They are used when a device transfers unsolicited data to a host.

Control

Control transfers are used to service devices and to handle specific requests. They are typically used during device configuration.

Bulk

Bulk transfers are used to transfer large blocks of data that have no periodic or transfer rate requirement. Printers and storage devices typically deploy bulk transfers.

Isochronous transfer mode

An isochronous transfer requires a constant bandwidth within certain time constraints. Constant bandwidth is required to support the demands of streaming multimedia devices such as speakers or video cameras. Unlike asynchronous transfers, no handshaking occurs and data delivery is not guaranteed.

USB Support for Plug and Play

Windows XP Professional supports Plug and Play configuration of USB devices by using the following USB features:

Hot plug-in capability

You can plug a USB device into the system at any time. The USB driver stack enumerates the device and notifies the system that the device is present.

Persistent addressing

USB devices use descriptors to identify the device, its capabilities, and the protocols it uses. A device descriptor contains a Vendor ID (VID), a Product ID (PID), and a version number that tell the computer exactly which drivers to load. An optional serial number differentiates one device from another of the same type.

Power options

USB supports three power modes: On, Suspend, and Off.

User Interfaces for USB Device Properties

Windows XP Professional provides user interfaces to display relevant information about the status of USB devices. The information provided by the USB user interface in Device Manager provides the advanced user with property sheets for hubs and controllers that give specific USB power and bandwidth information.

In addition, an event-driven interface allows error detection and correction by notifying the user about a problem on the bus. The interface provides details about the error and suggests solutions. For information about the USB troubleshooting user interface, see Troubleshooting a Universal Serial Bus Device later in this chapter.

For more information about using Device Manager to display device properties, see Device Manager earlier in this chapter.

USB Root Hub Power Properties

The Power Management tab in the USB Root Hub Properties dialog box displays information about power usage on that hub. The Hub information box indicates the hub type and the amount of power available from each port (determined by hub type).

The Attached devices box lists devices attached to the hub s ports and the power each device requires to function. If a device requires more power to function properly than the hub s ports supply, a message notifies the user. The user can view the Device Manager property dialog box for the hub by double-clicking the device. Clicking Refresh updates the information in the dialog box, which shows devices that are attached or removed.

USB Host Controller Advanced Properties

The USB Host Controller dialog box displays information about bandwidth usage on the USB host controller and gives the user the option of turning off USB error detection. The Advanced tab in the USB Universal Host Controller Properties dialog box shows the bandwidth allocation page. The Bandwidth section of the dialog box describes USB bandwidth and how it pertains to what the user sees displayed on the property page. The list box displays all devices attached to the controller that consume isochronous bandwidth (typically, USB video cameras and USB speakers), along with the bandwidth each takes. To maintain bandwidth for control transfers, the amount of bandwidth reserved by the System Reserved device listing will change, depending on what devices are installed or removed. For every device that consumes one percent or more of the controller s bandwidth, there is a corresponding section in the Bandwidth Used column, which displays cumulative bandwidth usage. However, HID-compliant devices do not display here, although they do cause an increase in the System Reserved percentage.

Checking the Don t tell me about USB errors check box and clicking OK disables the display of the USB error detection and correction messages. For more information, see USB User Interface Error Detection later in this chapter. The default state for this button is unchecked.

IEEE 1394

Windows XP Professional supports the Institute of Electrical and Electronics Engineers (IEEE) 1394 bus, which is designed for high-bandwidth devices, such as digital camcorders, digital cameras, digital VCRs, and various storage devices. The IEEE 1394 bus is a digital, peer-to-peer interface that supports data transport speeds from 100 to 400 Mbps. It provides a high-speed Plug and Play capable bus that reduces the amount of power that peripheral devices require and provides support for isochronous data transfer.

IEEE 1394 can connect up to 63 devices to one IEEE 1394 bus and link up to 1023 buses to form a network of more than 64,000 devices. Each device can have up to 256 terabytes of memory available over the bus. A built-in mechanism ensures that all devices have equal access to the bus.

Windows XP Professional supports three protocol standards for data transport over the IEEE 1394 bus:

Windows XP Professional supports IEEE 1394 by allowing IEEE 1394 device drivers to communicate with the IEEE 1394 bus class driver. In compliance with the Open Host Controller Interface (OHCI) 1.0 standard, Windows XP Professional includes the IEEE 1394 bus class driver with hardware-specific minidriver extensions for add-on and motherboard-based host controllers.

IEEE 1394 Bus Connector and Cable

The IEEE 1394 specification defines a standard connector and socket, which includes three interfaces: a 6-pin connector and cable, a 4-pin connector and cable, and a 6-pin-to-4-pin connector and cable. The 6-pin cables can supply power to a device over the bus, while a 4-pin cable can only carry data. An IEEE 1394 bus cable contains two pairs of twisted-pair cabling to accommodate the serial bus.

Data Transfer Rates Supported by IEEE 1394

IEEE 1394 supports both isochronous and asynchronous data transfer protocols. The IEEE 1394 specification currently supports the following bus transfer rates:

You can link devices with different data rates; communication takes place at the highest rate supported by the lowest-rate device.

Support for Plug and Play and Other Devices

Windows XP Professional provides additional support for the IEEE 1394 bus in use with the following specifications and devices.

Plug and Play

Windows XP Professional supports hot plugging of devices that use the IEEE 1394 bus. All IEEE 1394 devices can be plugged in while the computer is on, and the device is detected and configured. For more information about Plug and Play, see Plug and Play Overview earlier in this chapter.

A/V Devices

Windows XP Professional supports streaming digital video and transfer of MPEG-2 data to and from IEEE 1394 devices. An application of this is video editing, where the data is retrieved from a digital camera, edited, and then written back to the camera, to a digital VCR, or to a storage device.

Storage and Other Devices

Support for IEEE 1394 storage devices, printers, and scanners is implemented by using the SBP-2 protocol. For example, SCSI class drivers can use SBP-2 to connect and use IEEE 1394 devices. Devices that use the SBP-2 protocol must be OHCI compliant.

Other Bus Support

Most buses supported by previous versions of Windows function under Windows XP Professional. The buses that are supported include PCI, AGP, PC Card, CardBus, SCSI, ISA and EISA buses.

Note 

Windows XP Professional does not support the Micro Channel bus. Micro Channel architecture is found mainly in older IBM PS/2 computers.

PCI Bus

The Peripheral Component Interconnect (PCI) bus, included in all computers, is used for transferring data between the CPU and hardware devices, adapters, or non-PCI bus-circuit boards. PCI is a local bus system that allows up to 10 PCI-compliant expansion cards to be installed in the computer. The PCI bus system requires the presence of a PCI controller card, which can exchange data with the system s CPU either 32 bits or 64 bits at a time, depending on the implementation, and controls data transfers between main memory and all the other devices on the PCI bus. Because of its high bandwidth, the PCI bus is capable of high-speed data transfers.

The PCI specification allows for multiplexing, a technique that permits more than one electrical signal to be present on the bus at one time. The PCI controller also allows intelligent, PCI-compliant adapters to perform tasks concurrently with the CPU using a technique called bus mastering. This improves performance in tasks, because it frees the CPU for other work by enabling devices to take temporary control of the PCI bus for data transfer.

AGP Bus

The Accelerated Graphics Port (AGP) bus is a dedicated video bus that provides fast, high-speed data transfers from system memory to the display adapter. For more information about AGP, see Managing Digital Media in this book.

PC Card and CardBus

Windows XP Professional supports the features of products designed for the PC Card standard. The 16-bit version of the PC Card is also known as PCMCIA. These products include multifunction cards, 3.3-V cards, and 32-bit PC Cards. Major advantages of PC Cards are small size, low power consumption, and Plug and Play support.

Windows XP Professional supports CardBus (also called PC Card 32), which is a combination of PC Card 16 and PCI. CardBus brings the advantages of 32-bit performance and the PCI bus to the PC Card architecture.

CardBus allows portable computers to perform high-bandwidth functions such as capturing video. For more information about PC Cards and CardBus in portable computers, see Supporting Mobile Users in this book.

SCSI Bus

The Small Computer Standard Interface (SCSI) standard defines a high-speed parallel bus that carries data and control signals from SCSI devices to a SCSI controller. It is an intelligent bus most often used for high-performance hard disks on multi-user systems. It is also flexible and can be used with lower throughput device such as CD ROMs, tape drives, or scanners.

ISA Bus

The Industry Standard Architecture (ISA) bus is based on a design specification introduced for the IBM PC/AT. The specification allows components to be added as cards plugged into standard expansion slots, and has a 16-bit data path. Plug and Play ISA devices can be used on existing computers, because Plug and Play does not require any change to ISA buses. Windows XP Professional does not support non Plug and Play ISA devices, although they work if manually configured.

EISA Bus

The Enhanced Industry Standard Architecture (EISA) bus is based on a design specification for x86-based computers introduced by an industry consortium. EISA maintains compatibility with ISA, but provides additional features. These include a 32-bit data path, and the use of connectors that can accept cards made for both EISA and ISA buses.

Other Hardware Support

In addition to USB and IEEE 1394 bus devices, Windows XP Professional supports standards for a number of other hardware devices ranging from network adapters to digital media devices.

Network and Other Internal Adapters

An adapter is a printed circuit board that allows a computer to use a peripheral device for which it does not already have connections or circuit boards. For example, a network adapter provides the physical interface (connector) and the hardware (circuitry) to connect a node or host to a local area network. A network adapter is also called an adapter card, a card, or a network adapter.

For information about troubleshooting network and other internal adapters, see Troubleshooting Network and Other Internal Adapters later in this chapter.

For more information about networks, see Connecting Clients to Windows Networks in this book.

Modems

A modem is a communications device that enables a computer to transmit information over a standard telephone line. Modems convert a digital signal from a computer to an analog signal on the telephone line, and vice versa.

Modems fall into two distinct categories, standard and controller-less modems. Although both types offer similar functions and features, the back-end hardware and the drivers used in their implementation differ significantly.

Human Interface Devices

Windows XP Professional supports devices that are compliant with the Human Interface Device (HID) firmware specification. HID devices are those devices used by humans to control the operation of computer systems. Examples of HID devices include keyboards and pointing devices such as mouse devices and touch screens; panel controls such as knobs, switches, and buttons; consumer appliance devices such as audio/video appliances and remote controls; and devices that might not require human interaction but provide data in a similar format, such as bar code readers or voltmeters.

The HID specification was developed by the USB Implementers Forum and is mainly implemented in devices connected by USB. However, Windows XP Professional includes HID support for devices connected by using other ports or buses. For example, HID devices connected by IEEE 1394 can be developed and supplied by vendors but are not common.

An HID device is Plug and Play compliant if its underlying bus is Plug and Play compliant, and it indicates its class and HID information when plugged into the host system. Plug and Play HID devices do not require installation of additional software drivers, but non Plug and Play HID devices might. The use of Windows Driver Model (WDM) compliant drivers provides operating system support. Windows XP Professional supplies the HID class driver, the HID minidriver for the HID USB miniport, and the HID parser. Support for Plug and Play and power management for USB/HID devices takes place within the USB driver stack that is part of the WDM-based architecture.

From the perspective of a computer program, any HID device can be accessed either through HID application programming interfaces (APIs), or through DirectInput Component Object Model (COM) methods. DirectInput, which is part of DirectX digital media architecture, provides an input device API to support HID devices.

For more information about the USB Implementers Forum and HID usage, see the USB link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

For more information about Input and HID Devices, see the Input and HID Devices link at http://www.microsoft.com/windows/reskits/webresources

For more information about developing minidrivers and filter drivers, see the Driver Development Kits link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

DVD

DVD (digital video disc) is an optical disc storage technology that can hold video, high-quality CD audio, and computer data in a single digital format. DVD devices can read multiple, digitally stored data streams concurrently for playback of digital media applications and full-length motion pictures. Two major compression technologies, MPEG-2 and AC-3 (also called Dolby Digital), are used to store from 4.7 gigabytes (GB) to 17 GB of data on a single DVD disc.

DVDs also offers copy and distribution protection. This is accomplished by encrypting the content on a disc, and by restricting playback of discs to specified geographical regions. For more information about copy and distribution protection offered by DVD, see Managing Digital Media in this book.

Windows XP Professional supports DVD in the following ways.

DVD video and audio playback

If the proper decoding hardware or software is present, Windows XP Professional supports playback of DVD video. This support is important for entertainment computers and any digital media platform intended to play movies. Windows XP Professional support includes the same interactivity and high-quality playback found on a standard DVD video player. DVD devices can also play most audio CDs.

DVD as a storage device

You can use DVD as a storage device on most computers that support DVD. DVD-ROM discs and devices provide cost-effective storage for large data files. The UDF file format is used to store data on most DVDs.

In Windows XP Professional, different types of DVD drives have differing capabilities, as follows:

For more information about DVD, see Managing Digital Media in this book.

For more information about the UDF and FAT32 file formats, see File Systems in this book.

Digital Audio Devices

Windows XP Professional uses the Windows Driver Model (WDM) audio architecture to support digital audio devices. The operating system can manage multiple audio streams, and two or more applications can play sounds simultaneously. For example, if you are listening to music on your computer, you can also hear the notification that a message has arrived. The WDM audio architecture performs audio processing in kernel mode, which significantly reduces latency, the time required for a signal to travel from one point to another.

Windows XP Professional also supports the Audio Codec 97 (AC 97) specification for digital audio, which defines a widely adopted audio architecture. The AC 97 controller that is typically integrated into the chipset handles the digital aspects of audio, while the AC 97 codec handles the analog aspects of audio. The AC 97 specification describes the architecture of the codec and the digital interface between the controller and the codec. Windows XP Professional includes AC 97 audio drivers to support the integrated AC 97 controllers from four major computer chipset manufacturers. As a general rule, these AC 97 audio drivers support any manufacturer s AC 97 controller when paired with any codec that is AC 97 compliant.

Because digital audio is processed by the operating system, a separate sound card is not required to process digital audio. Digital audio is supported on several bus types, including PCI, ISA, and PCMCIA, and on external digital audio devices connected with USB and IEEE 1394.

Windows XP Professional supports the following digital audio features and devices:

Windows XP Professional also supports DRM technology that allows content providers such as artists and record companies to protect proprietary music or other data by encrypting digital content and attaching usage rules to it. These rules determine restrictions such as the number of times content plays and the types of devices that play it. Using Windows XP Professional, you can ensure that a device or driver is trusted not to violate usage rules or allow a user to circumvent security. Trusted drivers are only relevant to DRM content that requires this security.

Driver modules that handle audio content must include a DRM signature before they can render protected content that requires a trusted audio device. Windows XP Professional uses a DRM signature in the driver s catalog files to identify a trusted device. This is not the same as the signature required for Windows drivers. To play DRM-encrypted content requiring a trusted audio device, WDM audio drivers and any associated filter components must be DRM compliant.

Still Image Devices

Windows XP Professional supports still-image devices through Windows Image Acquisition (WIA), which uses the WDM architecture. WIA provides robust communication between applications and image-capture devices, allowing you to capture images efficiently and transfer them to your computer for editing and use.

WIA supports SCSI, IEEE 1394, USB, and serial digital still image devices. Support for infrared, parallel, and serial still image devices, which are connected to standard COM ports, is provided by standard infrared, parallel, and serial interfaces. Image scanners and digital cameras are examples of WIA devices. WIA also supports Microsoft DirectShow -based webcams and digital video (DV) camcorders to capture frames from video.

WIA supports a camera class driver that is based on Picture Transfer Protocol (PTP), a standard that enables digital cameras to communicate with each other, with printers and with computers. WIA automatically recognizes all PTP digital still cameras that support the PTP class ID and provides all of the basic still image functionality as with any other WIA device. PTP cameras that do not support the PTP class ID can also be recognized by means of a third-party .inf file that maps the device Plug and Play identifier to the WIA PTP class driver.

WIA provides a driver model for manufacturers to write drivers for cameras with proprietary protocols. When such a WIA driver is installed, all WIA features are available to this camera.

WIA also provides Mass Storage Class (MSC) device support. The storage on MSC cameras can be accessed using a drive letter that appears in My Computer If the camera uses the MSC driver provided with the operating system, the AutoPlay dialog box is displayed when it is connected to the computer, which allows the user to select the Scanner and Camera wizard.

Support for Microsoft DirectShow-based webcams and digital video camcorders is provided by a generic DirectShow filter, which identifies itself as a source of images.

WIA Architecture

WIA architecture describes both an API and a device driver interface (DDI). The WIA architecture includes components provided by the software and hardware vendor, in addition to Microsoft. Figure 9-3 illustrates the WIA architecture.

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Figure 9-3: Components of WIA architecture

Windows Explorer user interface

Windows Explorer extensions such as My Computer and My Pictures, as well as Scanners and Cameras in Control Panel provide a user interface by which users can access WIA devices. For example, an icon for each installed WIA device appears in the My Computer folder. If a still image camera is installed, clicking the camera icon opens an interface that shows thumbnail pictures, controls for saving pictures, and a live preview that you can capture if the camera is a supported webcam or Digital Video (DV) camcorder.

The My Pictures folder includes thumbnails of images, a link to the WIA Scanner and Camera wizard, a built-in slide show, an enhanced preview window called the Windows Picture and Fax Viewer, and the option to print pictures from the preview window.

Microsoft Paint also supports WIA. When a WIA device is present, From Scanner or Camera is enabled on the File menu, and users can retrieve pictures from WIA devices.

Class Installer

The imaging class installer supports easy removal and installation of WIA devices. The installer also supports Plug and Play devices for USB, SCSI, IEEE 1394 buses, and serial-based digital still cameras.

Scanner and Camera wizard

Using the Scanner and Camera Wizard, users can retrieve images from any of the supported devices installed on the system. The Wizard provides a preview page where the user can select from several scanning options and adjust image settings. It is opened by default when WIA-enabled scanners are activated (a scan event ) and when Plug and Play still digital cameras are connected (a connect event ). By using the AutoPlay dialog, the Wizard can also be opened when media, such as flash memory cards, that contain image files are inserted into the computer (a media-insertion event ). Note, however, that the Wizard is not opened by default for video cameras.

Using the Wizard for a digital still camera, the user can select one or more pictures, rotate them, and view information such as picture size and resolution.

With a video camera, the user can select previously captured still images, rotate them, view picture information, and even see live video and capture still images. The user can also name the pictures, save them in the My Pictures folder, categorize pictures by using sub-folders, and publish them on the Web.

For non Plug and Play devices, the user can start the wizard from the Accessories menu.

Note 

The WIA driver for DirectShow-supported webcams and digital video camcorders stores captured pictures in a temporary file. As a result, when you capture pictures with a webcam or DV camcorder, be sure to save the pictures you want to keep to the My Pictures folder or some other location on the PC. This ensures that the pictures are not deleted from the drive when clearing out the Temp folder, either manually or using the Disk Cleanup utility.

Visual Basic and other scripting languages

WIA includes a scripting model, which allows advanced users and IT professionals to develop WIA applications by using Microsoft Visual Basic and other scripting languages. For more information about developing WIA applications, see the Software Development Kit (SDK) information in the MSDN Library link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

WIA applications

Users can start image acquisition and manipulate images by using either the WIA wizard or another application. Two primary types of WIA applications use still images:

TWAIN Data Source Manager

The TWAIN Data Source Manager (DSM) is an industry-standard software library used to abstract TWAIN applications from still image devices. WIA uses the TWAIN DSM implementation in Microsoft Windows XP together with the TWAIN compatibility driver to provide a compatibility layer for applications that support TWAIN version 1.7 or later, but don t yet support WIA.

WIA common system dialogs

All scanner and camera device drivers that ship in Windows XP Professional use the WIA common system dialogs. There are four system dialogs that are used in WIA imaging applications to access WIA-enabled scanners and cameras. The dialog that displays is tailored to the device type used. For example, when scanning an image into Paint using a WIA-enabled scanner, Paint displays a WIA dialog that allows you to preview the scanned image, crop the image, set the color, contrast and brightness, and so on. Specific dialogs for still camera and video camera display when those devices are accessed. The device selection dialog displays when more than one WIA device is active on the system.

Device object

When the WIA device driver is started, it creates a device object that allows the application to communicate with the hardware. There are four types of device objects: full WIA minidriver, WIA flatbed scanner microdriver, WIA generic PTP camera driver, and WIA video camera driver.

WIA Device Manager object

When an application first communicates with a device, the WIA Device Manager detects all the devices, creates the device objects, establishes the link between the application and the device object, and retrieves and sets device properties.

WIA Event Model

As discussed above, Still Image devices can generate various events. Some devices, such as scanners, can support multiple events, which are traditionally mapped to the buttons on the scanner itself. The most common event for scanners is Scan, which is normally mapped to the scan button.

By default, the Scanner and Camera Wizard is associated with the Scan event (for scanners) and the Connect event (for still digital cameras). Consequently, when the scan button is pressed on a WIA scanner that uses a driver supplied with Windows XP Professional, the Scanner and Camera wizard appears.

The WIA event model includes a set of pre-defined events that can be associated by means of WIA device drivers or .inf files. At the same time, these pre-defined events are available to applications so they can automatically start when the event takes place.

An application can register itself to be the default event handler by calling the WIA APIs documented on the SDK. The application has 3 handler options global, device-specific, and device or event specific.

When an application registers as a global or device-specific event handler, a dialog appears when the event takes place. This dialog prompts the user to choose which application is to be the default event handler. The Scanner and Camera Wizard is presented as one of the options.

When an application registers as a combination device or event handler, the dialog does not appear.

When multiple applications are registered for the same event, a user can manually switch between them by using the Events tab on the device Properties page, which can be accessed by right clicking the device icon from My Computer and selecting Properties.

Image Color Management 2.0

Because colors can vary by monitor or printer, Image Color Management (ICM) version 2.0 ensures that images have accurate colors by storing standard, objective color characteristics for each output device that produces an image. As a result, a photograph taken by a digital camera looks the same on the monitor as when it was captured. In turn, the printed version of the same image accurately represents the image and colors seen through the camera and on the monitor.

Software for color management uses profiles, which are data about how each device represents color. These profiles provide the information that allows the color management software to prepare an accurate color reproduction.

ICM is based on the industry standard ICC profile, the standardized Color Management Module (CMM), and the default Standard RGB (red, green, blue) color space. Although this flexible system allows the use of any CMM, ICM uses LinoColor CMM by default. This makes Windows applications that use ICM 2.0 compatible with other platforms with respect to color management.

ICM 2.0 on Windows XP Professional is set up to run transparently for printing, which benefits users who do not need advanced color configuration options for devices. However, ICM provides full manual control with a selection of alternative color profiles a benefit to users who need color consistency on devices and platforms that might otherwise be incompatible.

ICM supports sRGB, which complements current color management strategies by enabling a default method of handling color in the operating system and on the Internet. It efficiently provides good quality color representation and backward compatibility. Standard RGB (sRGB) is the default color space in Windows XP Professional for all color images that do not have another embedded profile, or are not specifically tagged with other color information. If a specific color profile is assigned to an image or a device, that color profile is used. If no color profile is assigned, then the default sRGB profile is assumed.

Video Capture

Video Capture under Windows XP Professional is based on the WDM streaming-class driver. Windows XP Professional provides minidrivers for USB and IEEE 1394 cameras, as well as PCI and videoport analog video devices. Support includes DirectShow filters for WDM video capture interfaces and a Video for Windows (VFW) to WDM mapper for compatibility with previous interface versions. The mapper, also called the VFWWDM mapper, allows WDM video capture devices to take advantage of existing 32-bit VFW applications.

Capturing video with WDM has the following advantages:

Capture applications are available that use both DirectShow and VFW. The DirectX version 8.1 Software Development Kit (SDK) provides four sample video capture applications. These include AMCap, PlayCap, StillCap, and DVApp. For more information about the sample video capture applications, see the Windows XP Professional Software Development Kits link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

Video Capture provides real-time and step-frame modes for capturing video sequences.

Real-time capture

Real-time capture of video images demands a fast computer and hard disk. A video source for real-time capture (such as a video camera or videodisc) provides an uninterrupted stream of information to the capture hardware. The capture hardware copies each frame of the video sequence and the audio portion and transfers it to the hard disk before the next frame of data enters the capture hardware. Each video frame contains one image. If the system lags during capture, frames of video data are lost.

Step-frame capture

Step-frame capture collects video frames from a video sequence in a series of steps, capturing frames one at a time, typically from a paused video device. Step-frame capture causes the video source to pause as it collects each image. If an audio source is also selected, the capture mode rewinds the media in the video source and collects audio data as the video source plays a second time. You can perform step-frame capture manually, advancing the video source by using the controls on the video device. Windows XP Professional Video Capture also provides automatic step-frame capture for video devices that support the Media Control Interface. With this method, Video Capture issues frame-advance commands to the source device and captures the sequence frame-by-frame. When Video Capture finishes capturing the current frame, it advances the video source to the next capture point.

Step-frame capture provides an alternative for systems that cannot process a video sequence in real time due to a slow I/O subsystem. Because the system can fully process a video frame before contending with the next frame, you can use larger frame sizes and color formats, and you can compress the video sequence during capture.

Step-frame capture is also available by using WIA technology. For more information about WIA, see Still Image Devices earlier in this chapter.

Smart Cards

Smart Card technology is fully integrated into Windows XP Professional, and is an important component of the operating system s public-key infrastructure (PKI) security feature. A smart card is a small electronic device, often the size of a credit card, which contains an embedded integrated circuit. The smart card serves as a secure store for public and private keys and as a cryptographic engine for performing a digital signature or key-exchange operation. Smart card technology allows Windows XP Professional to authenticate users by using the private and public key information stored on a card.

Smart cards provide the following benefits:

The Smart Card subsystem on Windows XP Professional supports industry standard Personal Computer/Smart Card (PC/SC) compliant cards and readers, and provides drivers for commercially available Plug and Play smart card readers. Smart card readers attach to standard peripheral interfaces, such as RS-232, PS/2, PCMCIA, and USB. Windows XP Professional detects Plug and Play compliant smart card readers and installs them using the Add Hardware wizard.

To install a smart card reader driver, follow the directions in the Add Hardware wizard for installing device driver software. The process requires that you use either the Windows XP Professional CD or media from the smart card reader manufacturer that contains the appropriate device driver.

Note 

Microsoft does not support or recommend using non Plug and Play smart card readers. If you use a non Plug and Play reader, you must obtain installation instructions and associated device driver software directly from the manufacturer of the smart card reader.

For information about Windows XP Professional compatiblesmart card readers see the Windows Hardware Compatibility List link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources

Before using a smart card to log on, a user must be enrolled to do so by a user who has the privilege to enroll other users. This is required because enrollment for a smart card certificate is a controlled procedure in the same manner that employee badges are controlled for identification and physical access purposes. Enrollment provides the user with the public encryption key and certificate that is required for authentication and secure exchange of information. The user also needs a Personal Identification Number (PIN) to complete the logon process. Usually the user sets the PIN during enrollment, or is given a default PIN and is instructed to change it as soon as possible.

Using a smart card to log on to Windows XP Professional requires at least one service provider so that applications can access card-based services. A cryptographic service provider (CSP) makes available the cryptographic services of the smart card, such as key generation, digital signature, and key exchange. A Smart Card Service Provider (SCSP) makes the noncryptographic services of a smart card available to an application.

For more information about installing a smart card reader and smart card certificate enrollment, see Windows XP Professional Help and Support Center.

For more information about using Smart Cards for logon and authentication, see Logon and Authentication in this book.




Microsoft Windows XP Professional Resource Kit 2003
Microsoft Windows XP Professional Resource Kit 2003
ISBN: N/A
EAN: N/A
Year: 2005
Pages: 338
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