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To fully understand the how it works: you pick any device with HDMI output (let's say GoPro to reduce the variations) and you'll need a capture card for retreaving the data as multimedia signal. Please correct me where I'm wrong:

  • a digital signal is coming from the GoPro, why can't you process that signal completely trough software? What's the hardware for?
  • is the hardware purely for transcoding (and providing an input connector) or there is something else that I'm missing?
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EVERY place the computer CPU connects to the rest of the world requires an interface (hardware and software) of some kind. There is a very complex interface to get the data out of the computer and on to the screen where you are reading these words. And another interface to capture the key-strokes and convert them into characters entering the computer. And another interface for the speakers and for the microphone, and for the mouse, and for the WiFi and for the Ethernet and for the hard drive, etc. etc. etc.

So it should be no surprise that it takes some kind of interface to get the digital video stream of ones and zeros and gets them into the computer, also. Back years ago, the screen interface was a separate card, and the audio (speaker and microphone) was a separate card. And the USB to the mouse and keyboard was a separate card. But modern computers have integrated all of those INTO the computer which apparently makes you think that they don't exist.

But those interfaces are all required to get things in and out of the computer, and video is just another kind of signal that needs an interface (both hardware and software). But since most people don't need to ingest video, few (if any?) computers include a video input interface, so you must use a separate (internal or external) gadget to import video into your computer.

Yes, the hardware is to provide a place to plug in the video signal, but there is a requirement for software also. To "bundle" the video data into a form that the operating system and the video application can understand.

  • Thank you @Richard for the comprehensive description, we are looking for a much deeper, more exact answer. We're building livestream apps and working with hardware and SDKs. We are looking for a very deep understanding of the issue. Some hardvare can be replaced by software but would need too much resource, sometimes a specific chip is handling a specific task that would be way more complicated via software. Sometimes software is not enough. This is what we're looking for, a deep understanding of what we shouldn't even try because "....". – Yatko Nov 12 '16 at 23:23
  • E.g. transcoding, done by hardvare, can be done purely by software unless you need optimization. Did anyone succeed with capturing the stream with only the input as hardware and the rest is software? – Yatko Nov 12 '16 at 23:31
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If you are creating software which takes a video stream as input then you have two major options:

  1. Design your own hardware and software from scratch, standalone and make/keep it compatible with your choice of platforms Windows/Mac/Linux. This is a MAJOR challenge and from the tone of your questions you don't have the resources for this. You would have to hire/contract a hardware/software developer. Expect to pay a premium price for a project of this sophistication.
  2. Use the built-in API functions from Win/Mac/Linux for video input and output. Let the operating system take care of the driver/hardware interface and use hardware which is readily available to your customers. This is the only reasonable option, IMHO.

I know of NO computer of any type with built-in video (SDI or HDMI) input. So you have no option but to use some kind of layered hardware, either an internal PCIe card (eg: BLackmagic DeckLink) or an external converter box which connects to the compupter via USB3 or Thunderbolt or USB-C. (eg: Blackmagic Intensity) There are many vendors of these hardware products, both internal and external. I am using the Blackmagic products only as an example of what I am talking about.

  • Yes, exactly this is what we're doing and that's why I must know if besides providing the input (and optional transcoding) there is something that has to be present in such hardware/software combo, need very deep understanding of this matter. At the moment, we can work fine with Blackmagic and it's SDK but still no luck with Elgato. Someone here may know more and that's the info I am hoping to find. – Yatko Nov 14 '16 at 1:20
  • If you are having problems with Elgato SDK, then that is what you should have asked. The question you asked implied that you didn't even know what a video interface was for. So this has essentially been a waste of everyone's time. Please ask proper questions. – Richard Crowley Nov 14 '16 at 3:01

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