- Video processing expansion card
A Video processing expansion card is a computer
expansion cardthat allows a computer to receive television signals, record video, and/or playback video content. cite web
publisher=ATI TECHNOLOGIES INC.
Video capturecards are a class of video capture devices designed to plug directly into expansion slots in personal computers and servers. Models from many manufacturers are available; all comply with one of the popular host bus standards including PCI, newer PCI Express (PCIe) or AGP bus interfaces.
These cards typically include one or more
software drivers to expose the cards' features, via various operating systems, to software applications that further process the video for specific purposes. As a class, the cards are used to capture baseband analog composite video, S-Video, and, in models equipped with tuners, RF modulated video. Some specialized cards support digital video via digital video delivery standards including Serial Digital Interface(SDI) and, more recently, the emerging HDMIstandard. These digital models often support both standard definition (SD) and high definition (HD) variants.
While most PCI and PCI-Express capture devices are dedicated to that purpose, AGP capture devices are usually included with the graphics adapted on the board as an all-in-one package. Unlike
video editingcards, these cards tend to not have dedicated hardware for processing video beyond the analog-to-digital conversion. Most, but not all, video capture cards also support one or more channels of audio.
There are many applications for video capture cards including converting a live analog source into some type of analog or digital media, (such as a
VHStape to a DVD), archiving, video editing, scheduled recording (such as a DVR), television tuning, or video surveillance. The cards may have significantly different designs to optimally support each of these functions.
One of the most popular applications for video capture cards is to capture video and audio for live Internet video streaming. The live stream can also be simultaneously archived and formatted for playable-on-demand video (VOD). The capture cards used for this purpose are typically purchased, installed, and configured in host PC systems by hobbyists or systems integrators. Some care is required to select suitable host systems for video encoding, particularly HD applications which are more affected by
CPUperformance, number of CPU cores, and certain motherboardcharacteristics that heavily influence capture performance.
System-level products are also available preconfigured for these applications; these are typically called video encoders or media encoders and include a complement of relevant application software.
Once a video source is digitally encoded in the computer, it can be edited with a variety of software tools available for the given computer platform. However, some capture cards are designed with this specifically in mind. These cards often have dedicated
hardwarefor the express purpose of handling the rendering of video streams (instead of the CPU). Some of these cards even offer real-time video editing, or a specialized monitor connection which only displays the output of a video being edited as it would appear on a TV (sometimes an actual TV is used).
Editing cards also assist in the of sound on video clips, adding new sounds, synchronization of sound with video clip (e.g. lip movements are perfectly matched with dialogues), and other common post-production tasks like title generation.
External Capture Device
While external devices operate outside the PC chassis in most cases, their functionality is largely the same, in some cases identical silicon. Instead of using a PCI or AGP interface, an external device would use
USB, FireWire, or a PC cardto interface with the computer. These devices are more commonly associated with mobile or laptopcomputing because of their small sizes or portability.
MiniDVand Digital8camcorders, primarily those by Sony, have analog inputs that can transcodeto DV digital video and simultaneously output same via FireWire to a computer - these could also be recognized as video capture devices.
TV tuner card
* [http://linuxtv.org/v4lwiki/index.php/Main_Page Index of video capture hardware, from Video4Linux Wiki]
* [http://linuxtv.org/v4lwiki/index.php/List_survey_of_cards_in_use_now List of video capture cards]
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