By John Gonzalez of the LEIGHTRONIX Technical Support Team
Your computer at home has an HDMI (High-Definition Multimedia Interface) port, so does your television. Your mobile devices and cameras can have versions of HDMI ports as well. Walking into a broadcast studio, however, you’re more likely to run into HD-SDI (High-Definition Serial Digital Interface) connections on every piece of major video equipment.
Anyone coming from a personal media background that moves into the broadcast world may find the use of HD-SDI inputs over HDMI surprising. For the personal user, HDMI connections offer a simple, widely supported, and effective way to connect electronic devices and transmit audio and video.
With that said, despite the many positives of HDMI connections, there are unique difficulties and needs in a broadcast environment. Some of the aspects that make HDMI cables desirable can be hindrances to the typical broadcast workflow. Other factors, such as scope of the system and cost of cables come into play, particularly when the size of the operation grows.
One of the biggest reasons why HDMI is so popular on the consumer level is the content protection system that runs alongside of it. Content protection is mandated by the content providers, as such, standards force the user of HDMI connections to utilize protection. Known as HDCP (High-Bandwidth Digital Content Protection), this method of security prevents unauthorized copying of audio and video files as they move from connection to connection. This is great at the personal level, but for a professional workflow, with large amounts of data moving through connections, the extra layer of processes can slow things down when switching between sources as the content protection scheme is “negotiated” when an output device is connected to a receiving device. HD-SDI connections, on the other hand, allow limited restraints on the flow of data, making switching much smoother.
The connectors themselves are a big draw to HD-SDI. HDMI uses its own proprietary connectors, which in practice don’t hold up very well to constant connection and disconnection. HD-SDI, on the other hand, uses more common BNC connectors that are more rugged and include a native locking mechanism preventing unintended dislodging of connections (which can be pretty disastrous).
A professional broadcast studio can be a web of cables. For this reason, keeping signals strong over a significant length is important. HDMI cables are limited to about 30 feet of length before signal degradation begins. HD-SDI, on the other hand can easily push hundreds of feet without the need of a signal amplifier.
Side note: When purchasing cable for HD-SDI video, make sure to choose HD-SDI rated cabling. Since HD-SDI cables use common BNC connectors, they can look a lot like a number of different cables out there. Save yourself any intermittent video issues by purchasing the right cable for the job.
Though HDMI is an immensely useful and widespread connector, it just isn’t ideal for professional broadcast workflows. LEIGHTRONIX customers expect the most reliable and functional solution possible for their needs. With this in mind, all of our hardware with HD playout and recording uses HD-SDI connections, such as the IncodeX Vier®, LABvault-HD™, UltraNEXUS-HD™, and more. From the framework, to the chassis, all the way down to the connectors, our LEIGHTRONIX engineers strive to make the best possible decisions about product designs for customers.
John manages the daily operations of the LEIGHTRONIX Technical Support team and coordinates software and firmware testing and releases. He also troubleshoots analog and digital video systems, provides software support, and handles TCP/IP networking.
For more information on Leightronix products visit their page at NSCCOM.com.