Question / Help Is a capture card same as an HDMI to usb adapter?

divine123

New Member
Hi I was just wondering as this is not really being talked about on the internet. So I'm looking into buying a capture card like elgato camlink. Now looking at it physically, you connect an HDMI cable from your camera to the "elgato" and it will be detected as a webcam choosing the elgato device. Physically speaking it is the same thing where a female HDMI to USB male adapter that is not labeled as a capture card looks like. The reason why I'm asking is because the price of the adapter is way cheaper that the capture card.

Would this do the same thing? Detect your camera as a webcam?
 

koala

Active Member
A hdmi connection is unidirectional. It's meant to output video data from a video source (such as a graphics card) to a display device (such as a monitor). A capture card acts as monitor from the hdmi point of view, but instead of displaying the video data on a screen, it digitizes the data stream and sends it via usb (external cards, cheaper devices) or pcie-express bus (internal cards, more expensive devices) to the computer, where it is available as a video capture device.

I don't know which "female HDMI to USB male adapter" you speak of, but there are many USB "graphics card" devices that appear as additional graphics card to the computer. This is an output device - it receives data from the computer and sends video data via hdmi to a monitor. You cannot use this as input device - not possible to feed this with data through hdmi and receive a video stream with the computer.
 

Skillzore

New Member
A hdmi connection is unidirectional. It's meant to output video data from a video source (such as a graphics card) to a display device (such as a monitor). A capture card acts as monitor from the hdmi point of view, but instead of displaying the video data on a screen, it digitizes the data stream and sends it via usb (external cards, cheaper devices) or pcie-express bus (internal cards, more expensive devices) to the computer, where it is available as a video capture device.

I don't know which "female HDMI to USB male adapter" you speak of, but there are many USB "graphics card" devices that appear as additional graphics card to the computer. This is an output device - it receives data from the computer and sends video data via hdmi to a monitor. You cannot use this as input device - not possible to feed this with data through hdmi and receive a video stream with the computer.

How does the Hdmi cabel determine which is the source and which is the display?

Let's say I hook up my DSLR camera with an mini HDMI to HDMI cable, the I use an HDMI to USB-C adapter to hook it up to my PC. What triggers the PC to be the source and the camera to be the display and not the other way around?

If we can get it to trigger the other way around, a compatible software on the PC could read the signal and digitize it. Right?
 

koala

Active Member
A hdmi cable is just a piece of wire. There is no "direction" to choose in a hdmi connection. The circuit within a device defines what it is capable of, and the circuit has only this role. Not the complementary role. It's one way. It's like a light bulb. You can feed it energy and it lights up, but you cannot switch and feed it light and it outputs energy. The output from a GPU is always an output and an output only. The input on a monitor is always an input and an input only.
If you want to capture some hdmi signal, you need a hdmi capture device.
 

Skillzore

New Member
A hdmi cable is just a piece of wire. There is no "direction" to choose in a hdmi connection. The circuit within a device defines what it is capable of, and the circuit has only this role. Not the complementary role. It's one way. It's like a light bulb. You can feed it energy and it lights up, but you cannot switch and feed it light and it outputs energy. The output from a GPU is always an output and an output only. The input on a monitor is always an input and an input only.
If you want to capture some hdmi signal, you need a hdmi capture device.
Well, that is just the thing. USB-C is not strictly input or output. It works both ways. So why can't I feed an HDMI signal into it without a capture device? Why isn't that another feature of the circuit with a software switch?
 

koala

Active Member
USB-C is an interface. It only passes data. It does not do anything with the data. If you don't understand my example with the light bulb, you might understand an example with a printer. The printer is connected via USB, a bidirectional wire, but you cannot use a printer as scanner, unless the printer also has a scanner unit built in. The equivalent of the scanner unit is the capture device. The capture device scans the hdmi signal and produces a digital video data stream understandable by other software.
 

Skillzore

New Member
USB-C is an interface. It only passes data. It does not do anything with the data. If you don't understand my example with the light bulb, you might understand an example with a printer. The printer is connected via USB, a bidirectional wire, but you cannot use a printer as scanner, unless the printer also has a scanner unit built in. The equivalent of the scanner unit is the capture device. The capture device scans the hdmi signal and produces a digital video data stream understandable by other software.

Oh, no, I understand. What I am questioning is why we don't yet have an "elgato cam link" built into our PC. Sorry if that was unclear. With how small the solutions are today, and how popular streaming and capturing video is, I feel we should be seeing these built into PC's by now.
 

FerretBomb

Active Member
Oh, no, I understand. What I am questioning is why we don't yet have an "elgato cam link" built into our PC. Sorry if that was unclear. With how small the solutions are today, and how popular streaming and capturing video is, I feel we should be seeing these built into PC's by now.
Because there isn't much general demand for it. There ARE computers out there with them built in, but they're extremely niche machines. Streaming and capturing video is only just becoming popular. We may start to see systems in the future with a capture card integrated, but it adds a few hundred dollars to the price point, and the vast majority of people are going to go for a laptop that's in all other respects identical, but $200 cheaper as it doesn't have a capture card built in.

Personally, I wouldn't want one. There are a CRAP-TON of absolutely terrible capture devices on the market that aren't worth their price as slag (like Hauppage). Manufacturers already cheap out as hard as possible as-is. There's almost no way that would end well.

Fortunately, for those of us who need it, it's quite easy to add one and there are a ton of options. So there's really no need to have one built in.
 
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