|
A frame grabber is an electronic device that captures (i.e., "grabs") individual, digital still frames from an analog video signal or a digital video stream. It is usually employed as a component of a computer vision system, in which video frames are captured in digital form and then displayed, stored or transmitted. Early frame grabbers typically had only enough memory to store a single digitized video frame, hence the singular "frame" in the device name, whereas modern frame grabbers often can store multiple frames. Historically, frame grabber expansion cards were the predominant way to interface cameras to PC's. Other interface methods have emerged since then, with frame grabbers (and in many case, cameras themselves) connecting to computers via interfaces such as USB, Ethernet and IEEE 1394 ("FireWire"). Modern frame grabber devices often perform functions beyond capturing a single video input. For example, some devices can capture audio in addition to video, and some provide multiple video inputs that are captured concurrently. Other operations may be performed as well, such as deinterlacing, text or graphics overlay, image transformations (e.g., resizing, rotation, mirroring), and real time compression using algorithms such as MPEG2 and JPEG. Also, technological demands in fields such as radar acquisition, manufacturing and remote guidance have led to the development of frame grabbers that can capture images at high frame rates and resolutions. ==Circuitry== Analog frame grabbers, which accept and process analog video signals, include these circuits: * Input signal conditioner that buffers the analog video input signal to protect downstream circuitry * Video decoder that converts analog video (e.g., NTSC/SECAM/PAL) to a digital format Digital frame grabbers, which accept and process digital video streams, include these circuits: * Digital video decoder that interfaces to and converts a specific type of digital video source, such as Camera Link, CoaXPress, DVI, GigE Vision, LVDS, RS-422, or SDI Circuitry common to both analog and digital frame grabbers: * Memory for storing the acquired image (i.e., a frame buffer) * A bus interface through which a processor can control the acquisition and access the data * General purpose I/O for triggering image acquisition or controlling external equipment 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Frame grabber」の詳細全文を読む スポンサード リンク
|