A capture card is a device that allows your computer to send and/or receive video and audio signals to/from other devices. As an Aximmetry user, you will mostly need it to capture the video coming from your camera. From the perspective of virtual productions, it is one of the two most important pieces of hardware in your computer, next to the GPU.
We can distinguish mainly two types of capture devices: Internal and External.
Internal cards: are the ones that get installed inside your computer. They are connected to the PCI-E slot of your computer's motherboard, and they have various ports exposed at their back.
External Capture Devices: They connect to a computer with a USB port. Typically, these offer lower port selection compared to internal cards, as for example, it is very unlikely that you will be able to find an external capture card with 4 SDI ports or 4 HDMI ports. Please note that USB capture devices typically offer lower quality and frame consistency compared to their internal counterparts.
How to choose a Capture Card?
Before purchasing a capture card, we need to ask ourselves a few questions to figure out the right one to pick.
The most important questions are:
- How many cameras do I want to use?
- How many outputs do I need?
- How do I want to connect the cameras to the computer?
- What resolution and frame rate do I want to use for my video input?
- Do I want to sync my setup?
SDI or HDMI?
SDI connections can be found on high-end equipment. SDI cables lock into place and carry data over longer distances, while HDMI is much cheaper and has the same capabilities but it is restricted to shorter distances.
SDI has several types that offer different capabilities, including the maximum resolution and frame rate they can handle. Also, it has several standards and modes that need to be considered. Please refer to the SDI document for more details.
HDMI connections in a professional environment are mostly used for outputting video to monitors and LED processors. They don't lock into place and can reliably carry data only for short distances.
HDMI has several types as well, make sure to choose the appropriate gear depending on what resolution and frame rate you plan to use. You can check out the HDMI document for more details.
We need to see if our camera's (or cameras') output(s) is an HDMI or an SDI one. Even though there are such devices called Converters that allow us to convert an HDMI signal to an SDI one and vice-versa, this approach will add more complexity to your configuration as these devices have a few limitations when it comes to resolution, frame rate, color depth, etc...
How many and what type of ports do we need?
This question is answered based on how many cameras and how many outputs you need. An additional factor that plays an important role is the video resolution and frame rate you plan on using for your input and output.
Input or Output port?
Capture Cards vary in many ways. Some Capture Card can only be used for recording purposes. Such cards offer only input ports and they cannot be used for output purposes. Likewise, there are cards that can only output and cannot input video signals. In the world of Virtual Production, the most frequently chosen cards are equipped with I/O ports, in other words with ports that can operate both as input OR output ports. Please note that no Capture Card port can act as an input AND output port at the same time.
The Capture Card ports also vary based on the maximum data speed they are capable of processing. This determines the maximum video resolution and frame rate the ports can handle.
SDI ports are categorized based on how many gigabits of data they can transfer. The options here are limited: 1.5G (max: FHDp30), 3G (max: FHDp60), 6G (max: 4Kp30), 12G (max: 4Kp60). Some SDI Capture Cards can even use multiple SDI ports to transfer a single video stream.
HDMI ports are categorized based on the version of HDMI they support. The current highest version \ capacity is called HDMI 2.1a, and it is capable of transferring 4Kp120 or 8Kp60 video streams.
Depending on the type of port your Capture Card offers (SDI or HDMI) you will find different standards to describe this information (e.g.: 12G SDI, HDMI 2.1a).
Sync \ Genlock
You can learn more about this with our article about Syncing and Genlock.
Please note that Capture Cards that support receiving a Genlock signal usually offer a designated 'Ref input' SDI port that can only be used for syncing.
Nvidia offers Quadro Sync cards. These cards support genlocking and can be used to genlock compatible Nvidia Quadro GPUs.
Supported Capture Card brands:
Aximmetry has full support for the drivers of these manufacturers, so unless one of their cards has a special driver or a deprecated driver(which is rarely the case) all of their cards work with Aximmetry.
- Blackmagic Design
We typically upgrade the SDKs used in every new release of Aximmetry, so installing the latest drivers is always recommended. We indicate if an update to the drivers is needed on our software version history page, so please take a look at it when a new release is out.
Bluefish444: All cards released before the 23rd of June 2020 are supported (the KRONOS K8 and Epoch range of video cards) provided you have the Bluefish444 v6.5.0 SDK installed.
Deltacast: All cards are supported provided you have installed the latest driver (v6.20 currently).
There are plenty of other manufacturers that make more mainstream capture cards such as Elgato and AVerMedia. Their capture cards use the DirectShow API that Aximmetry fully supports. In simple terms, anywhere you see a device recognized as a DirectShow device (even a simple webcam) Aximmetry can also use it. Though, keep in mind that typically this type of device suffers from reduced image quality and frame rate consistency compared to the professional cards.