By PURPLELEC | 22 July 2024 | 0 Comments
Working Principle of HD Video Capture Card
The HD video capture card converts analog signals into digital signals after A/D sampling, writes them into SDRAM as cache through FPGA, and then reads the collected and compressed data from SDRAM through FPGA and transmits them to the host computer through PCI bus, and the host computer transmits and processes the data. The signal is collected in real time to support synchronous recording of sound, and the display screen can be stretched or full screen at will. The format after recording is avi, which ensures that it can adapt to various players. Non-linear editing, deletion or addition of relevant content can be performed in the post-recording stage. The color and clarity of the display screen can be adjusted, and the recording frame rate and bit rate can be adjusted.
The working principle of the HD video capture card mainly involves the conversion of analog signals to digital signals, signal caching and processing, and the final data transmission.
I. Signal conversion
Analog signal input: The HD video capture card first receives analog signals from the video source. These signals can be video signals in VGA, HDMI, DVI and other formats.
A/D sampling: The analog signal is converted into a digital signal through the A/D (analog to digital) sampler. This step is the key to video acquisition, which determines the quality and accuracy of the acquired video signal.
2. Signal Cache and Processing
Cache: The converted digital signal is written to SDRAM (Synchronous Dynamic Random Access Memory) or other types of cache. This step is to provide a stable data stream in subsequent processing and reduce data loss caused by mismatched processing speeds.
FPGA processing: FPGA (Field Programmable Gate Array) plays an important role in the acquisition card. It is responsible for reading data from the cache and performing necessary processing, such as data compression, format conversion, etc. The high flexibility and parallel processing capabilities of FPGA make it very suitable for the real-time processing needs of video acquisition cards.
3. Data Transmission
PCI bus transmission: The data processed by FPGA is transmitted to the host computer (usually a computer) through the PCI (Peripheral Component Interconnect) bus or other high-speed interfaces (such as PCIe). The PCI bus has the characteristics of high speed and stability, which can ensure the real-time transmission of video data.
Host computer processing: After receiving the data, the host computer can perform further processing, such as video decoding, editing, storage, etc. At the same time, the host computer can also control and configure the acquisition card through software to achieve more flexible video acquisition functions.
4. Other functions
Synchronous recording: HD video capture cards usually support synchronous recording of sound to ensure the synchronization of video and audio.
Display and editing: The captured video can be displayed in real time on the host computer and supports multiple display modes (such as full screen, stretch, etc.). At the same time, users can also perform post-editing on the video, such as deleting or adding content, adjusting the color and clarity of the picture, etc.
Compatibility: HD video capture cards usually have good compatibility and can support multiple video sources and formats, as well as different operating systems and platforms.
HD video capture cards achieve real-time acquisition and processing of HD video signals through the steps of analog signal to digital signal conversion, signal caching and processing, and final data transmission. In this process, key technical links such as A/D sampling, FPGA processing, and PCI bus transmission jointly ensure the quality and efficiency of video acquisition.
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