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Streaming Media
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June 2019
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Choosing a Capture Card for Multicamera Live Production

To choose the best capture card for mixing live events with PC-based software, you should pursue multi-part analysis. In this article, I'll get you up to speed on what features to look for, but you're going to have to carry the load on the critical subjective items.

You’ve decided to create your own station for mixing live events with a software program like Telestream Wirecast, Livestream Studio, StudioCoast vMix, CombiTech VidBlaster or Splitmedia Labs XSplit. You’ve selected the mixing software you plan to use, you’ve spec’d out the computer, and now you need a capture device to input the feeds for mixing.

To choose the best card, you should pursue multi-part analysis. First, you should make sure that all candidate capture devices work well with your mixing software, which sounds simple, but has multiple layers and some subtleties. Then, you should identify the features that you absolutely require, such as the number of input channels and their formats, or the availability of ISO recording, and eliminate any candidates that don’t supply them. Then you need to focus on more quality and performance features, such as onboard scaling and deinterlacing, and identify preference items, such as whether you want a breakout box to conveniently access all of your connectors.

Finally, you need to scrutinize the message boards of the mixing software vendor that you’ve selected and the capture card vendor to identify compatibility, stability, or similar issues, and to gauge vendor responsiveness to problems or feature requests. Plus you need to scan reviews on sites such as B&H and Amazon to get the opinions of actual buyers. In this article, I’ll get you up to speed on what features to look for, but you’re going to have to carry the load on the critical subjective items.

Does It Work With Your Mixing Software?

The first step is to check the website of your mixing software provider to identify supported capture products. Most vendors support the widest possible range of products, but there’s often a hierarchy. For example, Telestream keeps a list of Wirecast-compatible capture cards that their technical staff supports, and a separate list where the manufacturers have tested compatibility; obviously, you’ll be better support with a board in the first class.

Beyond this, try to learn which capture products are used by turnkey system designers who build systems around the same software. For example, 1 Beyond produces portable Wirecast systems usually built around the Matrox VS4. Livestream builds all of its systems around Blackmagic Design hardware, while vMix seems to favor AJA capture gear. If I were buying a capture device to run these programs, such integrations would carry a lot of weight.

Does it Run on Your Operating System?

Nothing exotic here; just including the point for completeness. Of course, if you’re considering mixing with a system that uses Windows 10, make sure your capture device supports the new before buying (Figure 1, below).

Figure 1. The Blackmagic DeckLink 4K Extreme 12G supports Blackmagic 4K cameras, with an inexpensive adapter for supporting Quad-SDI input.

Does it Support Your Required Inputs?

This is the point where you sit down and list all formats that you need the capture device to support. For some buyers, that’s simple: Perhaps you’re buying a system to support a single set of consistent inputs, such as four HD-SDI or HDMI cameras. For others, it’s more complex: Either you’re building a general-purpose system to work with multiple camera types, or you need compatibility with a range of inputs, not simply cameras, such as DVI or VGA for lecture capture. Or, perhaps you need a capture card that will support 4K input as well as HD-SDI. List all the formats your system needs to support and buy capture hardware that supports them.

There are multiple fine points to consider for many of these inputs. For example, if you need the ability to customize the input resolution of your DVI sources, make sure that your capture device lets you apply custom extended display identification data (EDID) profiles, a feature of several Epiphan capture devices. If you need support for a range of consumer formats, consider a product such as the AverMedia DarkCrystal 750, an external USB-based capture box that supports HDMI input and component input.

If you’re buying a card for 4K capture, note that there are multiple standards in play. Some 4K cameras support Quad-Link HD-SDI output, which transmits the 4K signal as four 1080p HD-SDI signals over four cables, allowing many boards with four HD-SDI inputs, such as the AJA Kona 4 or the Ospret 845e (Figure 2, below), to also capture 4K input. Some cameras output via HDMI 1.4, which can be captured with less expensive cards, such as the Magewell XI100DE-HDMI-4K, though the slower speed of HDMI 1.4 may limit capture frame rate or color depth.

Figure 2. The Osprey 845e has 4 HD-SDI inputs, with ProcAmp controls and onboard scaling and deinterlacing.

Blackmagic Design cameras output in 6G or 12G, which is primarily supported by Blackmagic Design capture cards, such as the DeckLink 4K Extreme 12G, to which you can add Quad Link capture via the DeckLink 4K Extreme 12G-Quad SD adapter card. The 4K market is far from standardized, so if you’re buying a card for 4K production, spend extra time on message boards and product forums to find known-compatible products.

Be sure to include audio on your list. If all of your audio will be input with the video, that’s easy; if you need to support inputs from other sources, you may need to buy an audio capture board as well. Some vendors, such as Osprey and Epiphan, have separate products or adapters that enable extra audio inputs, which obviously should work well with their respective capture cards. Others focus solely on video capture, and recommend third-party cards for audio capture. In the latter case, you should perform extra due diligence to find cards that function well with your video capture board.

While on the subject of input, check whether a capture card can auto-sense the video input or whether you have to set it manually. Unless you consistently work with the same input formats and configurations, auto-sense is much more convenient and will save you time and frustration each time you try to set up the system. If you’ll be working with different inputs from different cameras, make sure the capture board can handle this; some require the same incoming format for all inputs.

If you currently have HDMI or analog gear, but plan on upgrading to HD-SDI in the near term, consider buying an HD-SDI capture card and separate devices to convert these inputs to HD-SDI. Both AJA and Blackmagic Design have full lines of converter boxes for this and other similar conversions.

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