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By PURPLELEC | 14 September 2023 | 0 Comments

Introduction to common knowledge about video capture cards

  video source
  The main function of the video capture card is to capture the video source signal into the computer, so it is very important to understand the video source. First, you need to provide the video source for capture or compression.
  The video source can be: VCD player, existing video tape, camcorder, LD video disk, CCD camera, monitor video output, etc.
  Video collection
  Currently, there are soft compression capture cards and hard compression capture cards on the market. As software performance continues to increase and computer configurations continue to improve, soft compression cards have become the mainstream in the modern video industry. Video capture is the conversion of video into a digital format that can be used by a PC. Microvision professional image capture card converts the video signal to the memory and video memory in real time through the PCI bus after AD conversion.
  During the acquisition process, because the capture card uses the PCI Master Burst method to transmit data, the image transmission speed is as high as 33MB/S, which can realize reliable real-time transmission of camera images to computer memory and takes up almost no CPU time, leaving more CPU time. Time to do image calculations and processing.
  The capture function is the basic function of various video cards. By expanding it, it can form various levels of video processing cards: from simple video capture cards to professional image capture cards and non-linear editing systems.
video capture card
  Programmable video control chip
  Due to the improved performance of the enhanced VGA display controller and display card, PCs have a higher display resolution, which can directly process video information. At the same time, the emergence of various programmable video control chips makes the video signal and graphics Stacking becomes very easy. These chips effectively solve the digital phase locking and decoding technology of multi-standard color full TV signals, as well as the window control of video signals and graphics signals, thus making the input/output of video signals simple and easy to design and debug. The video cards launched using these chips realize the superposition of VGA graphics and video signals.
  In addition, such cards generally have sound input/output functions, so there is no need to configure a separate sound card. This period was the most rapid development stage of multimedia video hardware. The solution to the problem of graphics and image overlay made the image system truly usable for multimedia systems. Various capture cards, subtitle overlay cards, compression/decompression cards, movie cards, and TV cards emerge in endlessly.
  Image rate and acquisition calculation formula
  Frame image size (Image Size): W×H (length×width)---You must first understand: What size of image needs to be collected?
  Color depth: d (number of bits)---the color of the image you want to collect (8Bit grayscale image? Or 16/24/32Bit true color?)
  Frame rate: f ---The standard PAL system is of course 25 frames, but it may not be the standard. 500-1000 frames are possible.
  Data volume: Q(MB) ---The data volume of the image signal.
  Sampling rate: A(MB) ---The sampling rate of the capture card can be known from its product manual. Calculation formula: Q=W×H×f×d/8.
  Judgment criteria: If A>Q×1.2, then the capture card is capable of the collection work.

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