AV Gear Guide: HDMI/SDI Video Converters & Scalers

SDI & HDMI are two very popular video standards. HDMI is often used by domestic video equipment & prosumer cameras, whereas SDI is used in professional video applications where reliability and long cable runs are necessary. A HDMI/SDI converter allows you to switch video formats, to interconnect gear. This article compares the best HDMI/SDI Converters, and helps you find the one with the features you need.

Not all SDI to HDMI and HDMI to SDI converters are made equal. There is a big difference in functionality and build quality.

What is SDI?

SDI stands for Serial Digital Interface. SDI allows for transmission of digital video across a coaxial cable, such as RG6 and RG59 – with 75 ohm BNC connectors on each end. Depending on the cable quality and video resolution, SDI cable can run long distances, generally up to 100m.

Various SDI standards include HD-SDI (max 1080i60), 3G-SDI (max 1080p60), 6G-SDI (max 2160p30) and even 12G-SDI (max 2160p60).

SDI allows the transmission of up to 16 channels of linear 48kHz 24-bit audio within one cable, embedded within the SDI video signal itself. Some applications use the last two channels for talkback, whereas others sometimes use it for various signalling needs.

SDI does not support HDCP, which is one disadvantage of SDI over other standards such as HDMI and HD-baseT.

SDI is a very popular and robust standard for broadcast & event production.

What is HDMI?

HDMI stands for High Definition Multimedia Interface. It allows for transmission of HD and 4K video over a specialised cable and connector. It is only suitable for short cable runs, sometimes bootable to slightly longer distances with active converters and cable.

HDMI is popular with consumer equipment, such as TVs, cameras, computers, etc.

How do I convert SDI to HDMI, and back again?

The short answer is: you need a special box.

The slightly longer answer is that these boxes are called ‘SDI to HDMI Converters’ and ‘HDMI to SDI Converters’.

You can connect your SDI BNC on one side, and the HDMI connector on the other side, and it will perform the conversion for you.

Unless the box has a scaler, the conversion will not change the resolution or frame rate.

Most Popular SDI/HDMI Converters

There are a number of great SDI and HDMI converters on the market. These are from brands such as Blackmagic Design, AJA, and Decimator. There are also a number of ‘generic’ options, which may be suitable in limited circumstances.

What is the difference between a Scaler & Converter?

A converter switches the physical connection of the video signal (e.g. between HDMI and SDI connectors).

A scaler performs some sort of transformation on the signal, such as changing the resolution, changing the frame rate, adjusting the aspect ratio, etc.

A scaler is necessary when you cannot get the output resolution and frame rate of your source material (e.g. a computer or camera) into the correct resolution and frame rate for the rest of your video system.

A scaler is usually the case when using video switchers & routers without scalers in-built.

I highly recommend the Decimator MD-HX as a general-purpose video scaler. It’s solved more problems than I care to admit, and its screen with input signal details is very helpful for troubleshooting.

Which Converter or Scaler Should I Buy?

There are a number of aspects you should consider before choosing a model:

• Format support – does the unit support he resolution and frame rate of your source material?
• Build quality – is this unit likely to last over the long haul? If you use the converter a lot, consider choosing units better at heat dissipation (not the Blackmagic Micro converters – they run very hot)
• Scaling – do you need to scale? If so, pick the Decimator MD-HX
• Bidirectionality – If you need both directions in the one location, pick a bidirectional unit.
• Redundancy – If you need two SDI inputs with automatic failover, pick the Blackmagic Mini SDI to HDMI.

I’ve found the Decimator MD-HX and MD-LX to be the best value for money & robust design. These would be my personal recommendation for general event & install purposes.

Other Types of SDI and HDMI Converters

There are many other types of converters available, for example:

• Fiber converters – useful for long cable runs
• Audio converters – embed and de-embed audio from your video signal
• Analog converters – connect to legacy composite video equipment
• And many more!

HDMI/SDI Price Comparison

I’ve compiled a price comparison so you can see pricing on all these converters and scalers from a number of online retailers. These prices are accurate as of 2nd November, and based on the lowest price found on a new item. On sites such as eBay and Amazon, you may be able to save money by purchasing 2nd hand.