Video capture card is also called video capture card. It can obtain digital video information, store and play it. Many video capture cards can obtain audio while capturing video information, so that the audio and video parts are saved and played simultaneously when they are digitized.
There are several basic types of video capture cards:
Soft and hard compression cards
A soft compression card, also called a video capture card, is mainly composed of one or more video capture chips, peripheral components, and circuits. The circuit structure is simpler than hard compression. This card is only responsible for capturing video, and video compression, decompression, and other video processing are implemented by CPU operations.
Basic principle of soft compression video capture card: The camera analog video signal is input to the DVR card. The video capture chip converts the analog signal into a digital signal, and then enters the PCI directly or through the PCI bridge chip, and then transmits it to the memory. The video card is executed by the CPU. The compression algorithm in the DVR software compresses huge video signals and stores them on the hard disk. Hard compression card, also known as video capture compression card. The difference between this circuit board and soft compression card is that there are some circuit structures for video compression and decompression. Video compression is not given to the computer CPU for processing, but to the DSP chip. To deal with.
Basic principle of hard compression video capture card: the camera analog video signal is input to the DVR card, the video capture chip converts the analog signal into a digital signal, and then transfers it to the temporary memory that comes with the card, and then the video compression chip on the card The compression algorithm is executed to compress the huge video signal into smaller ones. Finally, these compressed data are directly or directly inserted into the PCI bridge chip and stored on the hard disk.
In terms of video compression capabilities, hard compression is better than soft compression. Because soft compression card uses CPU compression and consumes computer resources, rationally configuring the computer is the key to long-term stable operation of soft compression DVR.
There are many types of video capture cards, but for those amateurs who are not a large number of commercial video capture processing, a cheap video capture card without hardware compression function, or a TV card and 3D image card with capture function, Completely competent. As long as you work hard on the software, you can completely obtain the processing results equivalent to those of high-end and expensive video capture cards. Of course, in the post-production process of film and television files, it will take you more time. The video capture software that comes with those cheap or integrated cards is usually too simple, especially in the real-time file saving engine. The results of directly using these simple capture software for video capture processing are usually difficult to satisfy.
Analog capture card and digital capture card
According to the interface of the video signal source and the capture card, the video capture card is divided into two categories: one is an analog capture card, and the other is a digital capture card.
The analog capture card collects analog video signals into the PC through the AV or S terminal, so that the analog signals are converted into digital signals. The video signal source can come from analog cameras, TV signals, analog video recorders, etc.
Digital capture card digitally captures digital video signals to the PC in a digital-to-digital format through the IEEE1394 digital interface. Its video signal source is mainly from DV (digital video camera) and other digital equipment.
An important difference between analog capture cards and digital capture cards is that with digital capture cards, there is no loss of video signals during the capture process, which can guarantee the same results as the original video source, while using analog capture cards will have a certain degree of video signals. Loss. Someone has made an analogy: analog capture is similar to using a video recorder to rip a video tape. The ripping sub-band is always less clear than the master tape. If you use the sub-band ripping, the effect will be worse; and digital collection is like copying with a computer. The data file is the same, no matter how many times it is copied, the copied file is exactly the same as the original file, without any difference. Two-in-one capture card refers to digital analog capture card, AV + DV capture card. Digital input and output, analog interface input (DV / AV / S-video), full interface board.
External capture box and built-in capture card
External USB video capture card and built-in PCI interface video receiving card.
These two kinds of things have their own advantages and disadvantages. If you don't have enough funds, it is recommended that you use the built-in PCI video receiving card. Card interface card is recommended to choose PCI interface. At the same time, it also has the following advantages: first, it must be much cheaper than the external one, and second, it does not take up external desktop space. Now there are too many peripherals on the computer desk. This is an annoying thing. Third, the built-in video card does not require an external power supply, which not only eliminates the location of a power plug, but also reduces the situation of clutter caused by too many power cables, and also avoids the mains voltage. The video quality degradation caused by instability occurs; Fourth, most of the built-in video receiving cards can achieve multi-tasking under Windows system: built-in video card weaknesses; susceptible to electromagnetic interference from internal components of the computer The playback quality is reduced; it is more troublesome to install the card than an external one. The chassis must be disassembled before installation. It is also easy to conflict with other computer equipment when installing drivers or software. The advantages of external capture cards are Obviously, the external performance is more stable than the built-in video receiving card. It requires an external power supply and a parallel port on the computer. This will cause a lot of inconvenience to friends who have connected more peripherals.