HDMI versus HD-SDI: What Wikipedia won’t tell you.

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The Pros and Cons of HDMI versus HD-SDI, Part One

It is generally accepted that the quality of HDMI as a cabling method is adequate for most applications. While we here at Hi-Tech sell certain Stream Breeze Video Streaming systems that utilize HDMI inputs for camera connections, it is not always the best connection method for many applications. That is why we also offer HD-SDI connections as an optional upgrade.

There are multiple reasons for choosing HD-SDI over HDMI as a signal transmission conduit.

You may think that there is not much difference between HDMI and HD-SDI, after all they both carry a high-definition video signal (as well as multi-channel audio) over a single cable and are both established industry standards at this point. But HDMI is primarily a consumer level standard while HD-SDI is most definitely a professional level standard. In addition, HDMI carries up to 7.1 channels of audio (surround sound) while HD-SDI can carry up to 16 channels of audio! But there are important differences between them that make one superior over the other.

The first difference is mechanical

The standard HDMI and Mini-HDMI ports have no locking mechanism to keep the connector in place; if the cable has stress on it or it is pulled on at all, it may simply disengage from the port it was plugged into at the very least. If there is a lot of stress or the cable gets yanked around it may actually break the connector port where the cable is plugged into the device. This is much more likely to happen with the Mini HDMI connection as it is a fraction of the size of the standard HDMI connector and is not as robust. In our view, a port without a locking mechanism is an accident waiting to happen.

HDMI versus HD-SDI


The reason HD-SDI is Superior

HD-SDI connections do not suffer from the troublesome connector problem. They generally have a BNC video connector which uses a bayonet-style locking mechanism to attach the cable to the device. This type of connection is much more robust and will not come apart without the connector being rotated to uncouple the connector from the port. This virtually cannot happen by accident, it takes a deliberate action to disconnect the cable. This feature alone makes HD-SDI a better choice for professional applications where continuity of signal is of paramount importance.

HDMI versus HD-SDI

Another issue is losing the connection electronically.

When HDMI equipment is connected and powered up the two devices communicate with each other; this “handshake” is necessary as it is part of the HDCP protocol for copy protection. The two devices report to each other whether or not they are each HDCP compliant. This is usually the failure point of HDMI. If the signal from the camera to the receiving device even momentarily drops below the expected level for whatever reason the two devices will likely need to re-establish the connection again in order for the signal to get through.

The only way for this to happen is that one or both devices may need to be restarted in order for the devices to “handshake” again to allow the signal to pass. This is virtually impossible in a live event scenario as it would likely require halting the broadcast – a nightmare scenario to be sure.

So this handshaking requirement is somewhat of a problem. Luckily HD-SDI does not have a comparable copy protection “handshake” protocol, making it a more robust connector for many professional applications.

At Stream Breeze, we offer systems with HDMI connections as well as systems with HD-SDI connectors. Because we offer customization, however, we can ensure that your system has the type of connections you prefer. If you purchase a Stream Breeze Flex, for example, it normally ships with HDMI inputs but can easily be upgraded to HD-SDI connections instead. And all of our robotic PTZ cameras offer BOTH HDMI AND HD-SDI outputs SIMULTANEOUSLY so you have your choice of either one depending upon your needs and inputs.

You can find out more about our Stream Breeze systems on our website. For pricing on our Stream Breeze Multi-Camera Live Event Switcher and Streaming systems as well as our robotic cameras click here.

In part two of this post we will discuss cable length issues with HDMI versus HD-SDI.

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