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ADC Definition

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ADC Definition

ADC Definition

Stands for “Analog-to-Digital Converter.” Since computers only process digital information, they require digital input. Therefore, if an analog input is sent to a computer, an analog-to-digital converter (ADC) is required. This device can take an analog signal, such as an electrical current, and digitize it into a binary format that the computer can understand.

A common use for an ADC is to convert analog video to a digital format. For example, video recorded on 8mm film or a VHS tape is stored in an analog format. In order to transfer the video to a computer, the video must be converted to a digital format. This can be done using an ADC video conversion box, which typically has composite video inputs and a Firewire output. Some digital camcorders that have analog inputs can also be used to convert video from analog to digital.

ADCs may also be used to convert analog audio streams. For example, if you want to record sounds from a microphone, the audio must be converted from the microphone’s analog signal into a digital signal that the computer can understand. This is why all sound cards that have an analog audio input also require an ADC that converts the incoming audio signal to a digital format. The accuracy of the audio conversion depends on the sampling rate used in the conversion process. Higher sampling rates provide a better estimation of the analog signal, and therefore produce a higher-quality sound.

While ADCs convert analog inputs into a digital format that computers can recognize, sometimes a computer must output an analog signal. For this type of conversion, a digital-to-analog converter (DAC) is used.

NOTE: ADC can also stand for “Apple Display Connector,” which was a proprietary video connector developed by Apple. It combined DVI, USB, and AC power into a single cable. Apple stopped producing computers with ADC ports in 2004 in favor of the standard DVI connection.

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I/O Definition

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I/O Definition

I/O Definition
I/O Definition

Stands for “Input/Output” and is pronounced simply “eye-oh.” Computers are based on the fundamental idea that every input results in an output. For example, if you are running a word processor program and type a sentence on your keyboard, the text will appear on the screen. The keyboard is an input device and the screen is an output device. You might also print the text using a printer, which is another output device. The computer’s CPU handles all the I/O operations, sending the data it receives to the correct path. The path may be to the video card, to the hard drive, or to the RAM, just to name a few.

The ports on the outside of a computer are commonly referred to as “I/O ports” because they are what connect input and output devices to the computer. Software developers use I/O to describe how a program will function, depending on what a user enters. For example, if the user presses the space bar key in a game, say “Super Jumper Man,” the character on the screen will jump. Multiply that by several thousand other scenarios of user input and you have yourself a computer game.

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RFID Definition

by BlogsAdmin

RFID Definition

rfid-definition

Stands for “Radio-Frequency Identification.” RFID is a system used to track objects, people, or animals using tags that respond to radio waves. RFID tags are integrated circuits that include a small antenna. The are typically small enough that they are not easily noticeable and therefore can be placed on many types of objects.

Like UPC labels, RFID tags are often used to uniquely identify the object they are attached to. However, unlike UPCs, RFID tags don’t need to be scanned directly with a laser scanner. Instead, they can be recorded by simply placing the tag within the range of an RFID radio transmitter. This makes it possible to quickly scan several items or to locate a specific product surrounded by many other items.

RFID tags have many different uses. Some examples include:

  • Merchandise tags – These tags are attached to clothing, electronics, and other products to prevent theft from retail stores. These tags are typically deactivated at the place of checkout. Tags that have not been deactivated will sound the alarm system near the store’s exit.
  • Inventory management – Products stored in warehouses may be given RFID tags so they can be located more easily.
  • Airplane luggage – RFID tags may be placed on checked bags so they can be easily tracked and located.
  • Toll booth passes – E-ZPass and I-Pass receivers may be placed in automobiles, allowing cars and trucks to pass through toll booths without needing to stop. This enables drivers to make toll payments automatically.
  • Credit cards – Some credit cards have built-in RFIDs so they can be “waved” rather than “swiped” near compatible readers. The SpeedPass wand is an example of an RFID-only payment device.
  • Animal tags – RFID tags can be placed pet collars to make help identify pets if they are lost. Tags may also be placed on birds and other animals to help track them for research purposes.

The above list includes just a few of the applications of radio-frequency identification. There are many other existing and potential applications for RFID tags as well.

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Network Definition

by BlogsAdmin

Network Definition

Network Definition

Network Definition: A network consists of multiple devices that communicate with one another. It can be as small as two computers or as large as billions of devices. While a traditional network is comprised of desktop computers, modern networks may include laptops, tablets, smartphones, televisions, gaming consoles, smart appliances, and other electronics.

Many types of networks exist, but they fall under two primary categories: LANs and WANs.

LAN (Local Area Network)

A local area network is limited to a specific area, such as a home, office, or campus. A home network may have a single router that offers both wired and wireless connections. For example, a computer may connect to the router via Ethernet, while smartphones and tablets connect to the router via Wi-Fi. All devices connected to the router share the same network and often the same Internet connection.

A larger network, such as the network of an educational institution, may be comprised of many switches, hubs, and Ethernet cables. It may also include multiple wireless access points and wireless repeaters that provide wireless access to the network. While this type of network is much more complex than a home network, it is still considered a LAN since it is limited to a specific location.

WAN (Wide Area Network)

A wide area network is not limited to a single area, but spans multiple locations. WANs are often comprised of multiple LANs that are connected over the Internet. A company WAN, for example, may extend from the headquarters to other offices around the world. Access to WANs may be limited using authentication, firewalls, and other security measures. The Internet itself is the largest WAN since it encompasses all locations connected to the Internet.

Wiki

Windows Media Video

by BlogsAdmin

Windows Media Video

Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. It is part of the Windows Media framework. WMV consists of three distinct codecs: The original video compression technology known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other compression technologies, WMV Screen and WMV Image, cater for specialized content. After standardization by the Society of Motion Picture and Television Engineers (SMPTE),[1][2] WMV version 9 was adapted for physical-delivery formats such as HD DVD and Blu-ray Disc and became known as VC-1.[3][4] Microsoft also developed a digital container format called Advanced Systems Format to store video encoded by Windows Media Video.

History[edit]

In 2003, Microsoft drafted a video compression specification based on its WMV 9 format and submitted it to SMPTE for standardization. The standard was officially approved in March 2006 as SMPTE 421M, better known as VC-1, thus making the WMV 9 format an open standard. VC-1 became one of the three video formats for the Blu-ray video disc, along with H.262/MPEG-2 Part 2 and H.264/MPEG-4 AVC.[3][4]

Container format[edit]

Main article: Advanced Systems Format

A WMV file uses the Advanced Systems Format (ASF) container format to encapsulate the encoded multimedia content. While the ASF can encapsulate multimedia in other encodings than those the WMV file standard specifies, those ASF files should use the .asf file extension and not the .wmv file extension.[5][failed verification]

The ASF container can optionally support digital rights management using a combination of elliptic curve cryptography key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA-1 hashing function.

Although WMV is generally packed into the ASF container format, it can also be put into the Matroska[6] container format (with file extension .mkv), or AVI container format (extension .avi). One common way to store WMV in an AVI file is to use the WMV 9 Video Compression Manager (VCM) codec implementation.[7][8]

Video compression formats[edit]

Windows Media Video[edit]

Diagram illustrating the relative frame sizes of several common video resolutions targeted by Windows Media Video 9 Professional, starting with 480p.

Windows Media Video (WMV) is the most recognized video compression format within the WMV family. Usage of the term WMV often refers to the Microsoft Windows Media Video format only. Its main competitors are MPEG-4 AVC, AVS, RealVideo, and MPEG-4 ASP. The first version of the format, WMV 7, was introduced in 1999, and was built upon Microsoft’s implementation of MPEG-4 Part 2.[9] Continued proprietary development led to newer versions of the format, but the bit stream syntax was not frozen until WMV 9.[10] While all versions of WMV support variable bit rate, average bit rate, and constant bit rate, WMV 9 introduced several important features including native support for interlaced video, non-square pixels, and frame interpolation.[11] WMV 9 also introduced a new profile titled Windows Media Video 9 Professional,[12] which is activated automatically whenever the video resolution exceeds 300,000 pixels (e.g., 528 px × 576 px, 640 px × 480 px or 768 px × 432 px and beyond) and the bitrate 1000 kbit/s[citation needed]. It is targeted towards high-definition video content, at resolutions such as 720p and 1080p.

The Simple and Main profile levels in WMV 9 are compliant with the same profile levels in the VC-1 specification.[13] The Advanced Profile in VC-1 is implemented in a new WMV format called Windows Media Video 9 Advanced Profile. It improves compression efficiency for interlaced content and is made transport-independent, making it able to be encapsulated in an MPEG transport stream or RTP packet format. The format is not compatible with previous WMV 9 formats, however.[14]

WMV is a mandatory video format for PlaysForSure-certified online stores and devices, as well as Portable Media Center devices. The Microsoft Zune, Xbox 360, Windows Mobile-powered devices with Windows Media Player, as well as many uncertified devices, support the format.[15] WMV HD mandates the use of WMV 9 for its certification program, at quality levels specified by Microsoft.[16] WMV used to be the only supported video format for the Microsoft Silverlight platform, but the H.264 format is now also supported starting with version 3.[17]

Windows Media Video Screen[edit]

Windows Media Video Screen (WMV Screen) are video formats that specialise in screencast content. They can capture live screen content, or convert video from third-party screen-capture programs into WMV 9 Screen files. They work best when the source material is mainly static and contains a small color palette.[18]

One of the uses for the format is computer step-by-step demonstration videos. The first version of the format was WMV 7 Screen. The second version, WMV 9 Screen, supports VBR encoding in addition to CBR.[18] Additionally there is MSA1 (aka “MS ATC Screen codec” or “MSS3”) which is used in Live Meeting 2007. FourCCs for the formats are MSS1, MSS2 and MSA1.[19]

Windows Media Video Image[edit]

Windows Media Video Image (WMV Image) is a video slideshow format. The format works by applying timing, panning and transition effects to a series of images during playback.[20] The codec achieves a higher compression ratio and image quality than WMV 9 for still images as files encoded with WMV Image store static images rather than full-motion video.

Since the format relies on the decoder (player) to generate video frames in real-time, playing WMV Image files even at moderate resolutions (e.g. 30 frames per second at 1024 px × 768 px resolution) requires heavy computer processing. The latest version of the format, WMV 9.1 Image, used by Photo Story 3, features additional transformation effects, but is not compatible with the original WMV 9 Image format.[20]

Hardware support for WMV Image is available from Portable Media Centers, Windows Mobile-powered devices with Windows Media Player 10 Mobile.[15]

Since no known domestic DVD player supports this format, users of Photo Story 3 wishing to generate material capable of being played in a DVD player will first have to convert to MPEG-2 before burning a DVD (average file sizes in MPEG-2 are 5 to 6 times the .wmv file).

Versions[edit]

Public Name FourCC Description
Microsoft MPEG-4 version 1 MPG4 Video for Windows-based codec. Non-standard MPEG-4 codec incompatible with the later standardized version of MPEG-4 Part 2.
Microsoft MPEG-4 version 2 MP42 VfW-based codec. Non-compliant with finalized MPEG-4 part 2 standard.
Microsoft MPEG-4 version 3 MP43 VfW-based codec. Non-compliant with finalized MPEG-4 part 2 standard. Eventually locked for encoding only with ASF files (build 3688 and earlier could also encode to AVI).[21]
Microsoft ISO MPEG-4 version 1 MP4S DirectX Media Objects (DMO)-based codec. MPEG-4 Simple Profile compliant.
Microsoft ISO MPEG-4 version 1.1 M4S2 MPEG-4 Advanced Simple Profile compliant.[22]
Windows Media Video 7 WMV1 DMO-based codec.
Windows Media Screen 7 MSS1 DMO-based codec. Optimized for low-bitrate sequential screen captures or screencasts. Deprecated in favor of Windows Media 9 Screen codec.
Windows Media Video 8 WMV2 DMO-based codec.
Windows Media Video 9 WMV3 DMO-based codec. Video for Windows (VfW/VCM) version also available. [1]
Windows Media Video 9 Screen MSS2 DMO-based codec. Optimized for low-bitrate sequential screen captures or screencasts.
Windows Media Video 9.1 Image WMVP DMO-based codec. Optimized for encoding video from sequential bitmap images. Used, for instance, by Photo Story.
Windows Media Video 9.1 Image V2 WVP2 DMO-based codec. Optimized for encoding video from sequential bitmap images. Used, for instance, by Photo Story.
Windows Media Video 9 Advanced Profile WMVA DMO-based codec. Deprecated as non-VC-1-compliant.
Windows Media Video 9 Advanced Profile WVC1 DMO-based codec. VC-1 compliant format.

Audio compression formats[edit]

The audio format used in conjunction with Windows Media Video is typically some version of Windows Media Audio, or in rarer cases, the deprecated Sipro ACELP.net audio format. Microsoft recommends that ASF files containing non-Windows Media formats use the generic .ASF file extension.

Players[edit]

Software that can play WMV files includes Windows Media Player, RealPlayer, MPlayer, Media Player Classic, VLC Media Player and K-Multimedia Player. The Microsoft Zune media management software supports the WMV format, but uses a Zune-specific variation of Windows Media DRM which is used by PlaysForSure. Many third-party players exist for various platforms such as Linux that use the FFmpeg implementation of the WMV format.

On the Macintosh platform, Microsoft released a PowerPC version of Windows Media Player for Mac OS X in 2003,[23] but further development of the software has ceased. Microsoft currently endorses the 3rd party Flip4Mac WMV, a QuickTime Component which allows Macintosh users to play WMV files in any player that uses the QuickTime framework, free of charge to view files but chargeable to convert formats.[24] The WMV installer is bundled with Microsoft Silverlight by default, installation without Silverlight can be accomplished with a “Custom” install. According to the Flip4Mac website, WMV files with DRM encryption are not compatible with the component.

Encoders[edit]

Many programs can export video in WMV format; a few examples are Windows Movie Maker, Windows Media Encoder, Microsoft Expression Encoder, Sorenson Squeeze,[25] Sony Vegas Pro,[26] AVS Video Editor, VSDC Free Video Editor, Telestream Episode, and Telestream FlipFactory.[27][28]

Programs that encode using the WMV Image format include Windows Media Encoder, AVS Video Editor, and Photo Story.

Digital rights management[edit]

Main article: Windows Media DRM

While none of the WMV formats themselves contain any digital rights management facilities, the ASF container format, in which a WMV stream may be encapsulated, can. Windows Media DRM, which can be used in conjunction with WMV, supports time-limited subscription video services such as those offered by CinemaNow.[29] Windows Media DRM, a component of PlaysForSure and Windows Media Connect, is supported on many modern portable video devices and streaming media clients such as the Xbox 360.

Criticism[edit]

WMV has been the subject of numerous complaints from users and the press. Users dislike the digital rights management system which is sometimes attached to WMV files.[30] The loss of the ability to restore licenses for WMV files in the Windows Media Player 11 was not positively received.[30] The Microsoft Zune does not support the standard Windows Media DRM system, so that protected WMV files cannot be played.[31]

See also[edit]

  • JPEG XR / HDHD, an image file format and format developed by Microsoft