By PURPLELEC | 24 June 2024 | 0 Comments
PCI-E bus dual-channel VGA capture card based on FPGA
The working principle of VGA high-definition video capture card is that RGB analog signal is converted into digital signal after A/D sampling, written into SDRAM as cache through FPGA, and then read out the collected and compressed data from SDRAM through FPGA and transmit it to the host computer through PCI bus, and the host computer transmits and processes the data.
Images can be directly collected to VGA display memory or host system memory through high-speed PCI-E bus. In addition, VGA signal acquisition card can not only make images directly collected to VGA to realize single-screen working mode, but also use the scalability of PC memory to realize the required number of sequence images frame by frame continuous acquisition, and perform sequence image processing and analysis. If the VGA data of a PC is displayed on another PC and the VGA signal is collected, the traditional method is to convert the VGA signal into a video signal through the video converter VGA-VIDEO, and then display and collect it on another PC through the video capture card.
Video image acquisition is the process of converting the analog signal of the video source into a digital signal (i.e. 0 and 1) through processing, and storing these digital information on the computer hard disk. This analog/digital conversion is performed by the acquisition chip on the video capture card.
First, the PC sends a start acquisition command and waits for interrupts. Then the VGA acquisition card detects the start of field synchronization and starts to acquire a picture (based on line field blanking and size). After the acquisition is completed, the PC is notified through the PCI interrupt. After receiving the interrupt, the PC immediately starts DMA to read the data of the VGA acquisition card (only the memory address and the read size need to be prepared). Once the reading is completed, the acquisition is completed.
The video acquisition chip converts the analog signal into a digital signal, and then transmits it to the temporary memory on the board. Then the video compression chip on the card executes the compression algorithm to compress the huge video signal. Finally, these compressed signals enter the PCI directly or through the PCI bridge chip and are stored on the hard disk.
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