Video capture
{{Short description|Process of converting analog signal to digital}}
{{about|analog video capture|digital video screen capture|Screencast}}
Video capture is the process of converting an analog video signal—such as that produced by a video camera, DVD player, or television tuner—to digital video and sending it to local storage or to external circuitry. The resulting digital data are referred to as a digital video stream, or more often, simply video stream. Depending on the application, a video stream may be recorded as computer files, or sent to a video display, or both.
Early 16-bit ISA capture cards emerged in the early 90s. These cards were supported by VIDCAP as part of the Video for Windows package. One early card was a sandwich of two cards as early processors needed more logic to even get up to 15 frames per second.
PCI capture cards offered 30 frames per second. These cards could also handle capturing VHS tapes etc. but VHS image quality was poor so many adopted new video cameras until eventually digital cameras surfaced. Capturing video from digital cameras delivered excellent results above DVD quality.
Devices
{{About|electronic devices|the music video by Weezer|Video Capture Device (Weezer)|section=yes}}
Special electronic circuitry is required to capture video from analog video sources. At the system level this function is typically performed by a dedicated video capture device, colloquially called a capture card.{{cite book | last=Underdahl | first=Keith | title=Digital Video For Dummies | publisher=Wiley | year=2003 | isbn=978-0-7645-5899-3 | page=113}} Such devices typically employ integrated circuit video decoders to convert incoming video signals to a standard digital video format, and additional circuitry to convey the resulting digital video to local storage or to circuitry outside the video capture device, or both. Depending on the device, the resulting video stream may be conveyed to external circuitry via a computer bus (e.g., PCI/104 or PCIe) or a communication interface such as USB, Ethernet or Wi-Fi, or stored in mass-storage memory in the device itself (e.g., digital video recorder).
Decklink DSCF4439 (16425904428).jpg|A dual link 3 Gb/s SDI video capture card for PCIe (Blackmagic Design DeckLink HD Extreme 3D)
Datapath VisionRGB-E2s Dual Port Capture Card.jpg|A PCIe 2-port HDMI video capture card (Datapath VisionRGB-E2s)
ISA-Framegrabberkarte.jpg|ISA analog video capture card
8-channel uncompressed video+audio capture device.jpg|A Mini PCIe card that simultaneously captures 8 video and 8 audio signals (Sensoray 1012)
Reddo Videosieppari.JPG|A low-cost, consumer-grade USB audio/video capture device (Reddo Videosieppari)
See also
- TV tuner cards, which employ video capture circuitry to capture broadcast television
- Frame grabber
- Uncompressed video
- Dazzle (video recorder)
References
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- Convergence Culture. Where Old and New Media Collide, Buying Into American Idol, Henry Jenkins, 2006 New York University Press.
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