What is a Video Capture Card?

Acasis Blog What is Capture Card
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Examples of Obstacles in Streaming and Recording
About Capture and Loop-out
What is Dual Computer Live Streaming
The New Revolution in Streaming Media - Capture Cards
Complementary: USB Capture Card vs PCIE Capture Card


Examples of Obstacles in Streaming and Recording

What is a capture card?
When do we need a capture card?

Let's start with a WINDOWS system installation tutorial (there's no way to run screen recording software on a computer without a system installed). When it comes to tutorials we first mind screen recording, and then it is not difficult to realize that we need to meet two conditions to record video on the computer:
(1)The device must be normal to boot into the system.
(2)Must open the screen recording software in the system.

In the system installation tutorials, it needs to enter the BIOS and PE, the whole process of the installation video can not be recorded. So what should we do? The easiest way is to use the camera to take the video of the screen about installation, but this is very ineffective and the quality of the instructional video is low.

Another example is that many gamer anchors will broadcast some console games such as XBOX, PS4, and SWITCH. Because their system is not WINDOWS and can't run OBS, there is no way to use OBS to push the stream of this kind of game. So if you want to capture the screen of these consoles to use as a live broadcast, there is an HDMI capture card for you.

Or,I want to use a camera such as a Canon DSLR to do live broadcasting, the camera captures the picture in real-time to push the live broadcast, but the DSLR camera itself can not run the live broadcasting software, then there is no way to realize the real-time streaming DSLR camera real-time picture.

Acasis 4K60 HDR External Capture Card for Camera Live Broadcast


About Capture and Loop-out

Definition of video capture card:

Summarizing these examples, we find the common points.
Computers, consoles, or cameras all have a video output signal. For these video signals to be displayed, the computer needs to be connected to a monitor; the game host needs to be connected to a monitor; and the camera needs also to be connected to an external monitor.
Acasis Blog What is Capture Card

Now, let us truncate the signal output to the monitor, copy a copy, one of the outputs as usual to the original display device, another copy through some special means, and then re-encode this copy of the video signal into a video, output to the machine used to capture data. After completing the above steps, we can still record or capture the signal in real-time when we can't use the screen recording software to push the stream. The thing used to intercept capture copy and re-encode the video signal is the video capture card.
Acasis Blog What is Capture Card

Basic Features: Video Signal Capturing from the Hardware Level

Use software to record the screen to capture the screen. Essentially, the data is acquired from the software level. Video capture card is to directly capture the signal of the hardware video output interface, from the hardware level to obtain the video signal. Then the video signal is back to the system to generate video files.


Example Explanation and Loop-out:

To give the reader a better understanding of this entire process, let's go over another example.
Suppose there is a game console, an XBOX, connected to a TV in the living room, running Game A. The screen of Game A is output to the TV via an HDMI video cable.

To capture the Xbox's game’s screen, We put the HDMI cable once connected to the monitor connected to the capture card's video input interface. Then pull an HDMI cable from the capture card's output to the monitor before access. So that the XBOX game video signal will be from the output of the XBOX into the capture card, and then the capture card copy a copy of the video signal transcribed into a video file output to the computer and then sends the original video signal to the monitor for normal display.
Acasis Blog What is Capture Card

This capture card in the capture of encoded video signals at the same time outputs a video signal to the display of the operation we call the loop out. The loop out is almost no delay.

This can be done to capture the footage of the game console. The captured gameplay can be recorded as a video file on the one hand, and used for live streaming or push streaming on the other. Similarly, if you change your XBOX to PS4 or SWITCH or camera or another computer, you can also capture the video signal on the hardware side.

Of course, you can go ahead and use a capture card to capture the signal from your own computer's video, but if your computer can run the system, then why don't you just use the software to record the screen?

What is Dual Computer Live Streaming

In addition to being used for those who can't use recording software, capture cards can also be used for dual-computer live streaming.

Acasis Blog What is Capture Card

Why do you need two computers for live streaming?

We all know that screen recording software such as OBS or live streaming software consumes a lot of system performance when encoding. So it will rob the computer performance of the game you are live streaming, resulting in your game lagging or dropping frames. If you use a dual-computer live broadcast, computer A is only responsible for playing the game, and computer B is equipped with a capture card to capture the video signal of computer A. Then it is encoded and pushed directly on computer B. The computer performance consumed by encoding and streaming on computer B will not affect computer A which is running the game at all. this is the advantage of dual-computer live streaming.

However, dual-camera live streaming may also lead to audio and video desynchronization if the computer configuration is not good. In addition, the cost is also higher, so you need to choose carefully according to your actual needs.

 ACASIS 1080p HD Capture Card for Dual-camera Live Streaming


The New Revolution in Streaming Media - Capture Cards

From the very beginning of reading here, I believe that you have already understood the core point.
When using a capture card there have to be two devices, one is the device that the video signal is being captured, which is what we call the source, used to provide the video signal. The other is the computer with the capture card installed, which is what we call the receptor, and is used to capture copy re-encode the video signal.

Of course, in addition to streaming media, capture cards have more specialized uses. Medical imaging, security monitoring, and other industries also need capture cards to provide signal capture solutions.
We try to specialize in this kind of thing because we want to give you a better streaming solution.


Complementary: USB Capture Card vs PCIE Capture Card

Two major types of video capture cards: built-in video capture cards and external video capture cards, that is what we often talk about PCIE capture cards and USB capture cards, The most essential difference about them is the interface.

How to choose a PCIE or USB capture card?

(1).Need our computer equipment is desktop or laptop, the desktop can choose a PCI-E capture card or USB capture card. Laptops can only choose a USB interface capture card.
(2).Whether we need it to be flexible and convenient. If the use environment is relatively fixed, you can choose a PCIE built-in card. If the usage environment changes frequently, you need to choose a USB capture card.
(3).Refer to our needs for capture effects.
USB capture card = bandwidth of the computer interface + capture card parameters + output signal parameters of the captured device.
PCIE capture card = the performance of the computer itself + the parameters of the capture card the output signal parameters of the captured device.

To summarize, for stability and professionalism PCIE is the better choice, while it's also more expensive to build. In contrast, USB capture cards are more portable and more universal because of their price. So novice or amateur players are generally recommended USB capture cards and the ashes of players or ultra-professional players are usually recommended PCI-E capture cards. The two options are not superior or inferior, we need to choose according to our actual needs.