How do you output audio and video signals to a streaming device from a video source? There are a lot of ways to do that. The most common method, though, is the use of either SDI or HDMI. The question is, ‘which one should you use?’ In this SDI vs. HDMI post, you will find out the differences between these two connections.
SDI vs. HDMI
HDMI stands for High Definition Multimedia Interface. It’s a video standard used most often in consumer and prosumer environments. One of the things that distinguish this connection is the fact it carries uncompressed video alongside embedded audio signals. It can send these signals to any device capable of displaying or encoding video.
Image Source: by Md Rony
HDMI signals usually run up to 50 feet. Any more than that, you will need an amplifier to boost the HDMI signal, allowing it to run longer. For additional signal length, using converters is necessary. They will enable the transmission of an HDMI signal over a Cat5e or a CAT6 cable up to 390 feet.
With HDMI, there are different cable types. There is a standard cable, high speed, automotive, and others. There is also what you call a Mini and a Micro. Mini is often used in DSLR and mini camcorders, while GoPros and action cams use Micro. As one of the newest connector types today, HDMI has various advantages in terms of video quality.
Next, we have SDI, which stands for Serial Digital Interface. It is a professional video signal preferable in production environments. The reason is that SDI has a longer range of up to 300 feet and is much more reliable. After all, SDI often comes with BNC cabling – specialized connectors – to lock the cable into the devices.
In places where the cable may be tripped over or unplugged, it is best to use SDI connections compared to HDMI. Among the common standards of SDI include HD-SDI, 3G-DI, 6G-SDI, 12G-SDI, Dual-Link HDI-SDI, and Quad Link SDI. Basically, you would want the SDI connector when you need a longer range, while HDMI is ideal for shorter distances.
Other Differences between SDI and HDMI
Besides the range, there are other differences between SDI and HDMI. You will want to know of them to be sure about which connector is best to use for your needs. On that note, below are some of the things to consider regarding HDMI and SDI. But before that, let us talk about how these connections were developed.
Electronic companies and movie producers developed HDMI. When they created it, they did not intend to use it solely for transmitting audio and video signal from source to destination in a single cable. For them, the primary concern was how they could protect data when they use the HDCP standard.
HDCP or High-bandwidth Digital Content Protection was the precedent for HDMI’s authentication feature. With HDCP, there is a security key generated to set up a connection from the source to the destination. 0n the other hand, the broadcasting industry created HD-SDI when they were looking for the best method of transmitting HD video. Thus it doesn’t use an HDCP.
Besides these, below are other differences between HDMI and SDI:
Connector
SDI and HDMI both use different connectors. The biggest difference is that SDI connectors use BNC connectors, which allows it to be locked into the device. It means no chance of it being unplugged in case you accidentally tripped over it. Meanwhile, HDMI’s connectors are a lot like a USB.
Because of that, there is no way to keep the connection in place. HDMI is easily unplugged, especially if in an exposed site. The type of connector each of them uses is one of the reasons why SDI is better suited for production environments. With the number of cables and wires all around during production, you can’t have them getting unplugged quickly.
Time Code
HDMI does not transmit a Time Code with the video signals. SDI does.
Connection Speed
You will like SDI better compared to HDMI in terms of connection speed. The reason for this is that HDCP slows down how quickly the input is sent to the output. SDI responds quicker and smoother while the video is twitching. It is all because HDMI has a delay, given that the source and destination must handshake first.
Cost
HDMI is more expensive than SDI because the latter uses standard coax cable or RG-6. This cable is much cheaper since it is readily available. Therefore, you can save more on costs in using SDI for connection.
Cable Length
As mentioned before, SDI can be as long as 300 feet, while HDMI’s maximum length is only 30 feet. With that, SDI is practical to use in digital video broadcasting and similar projects where devices are going to be set up more than 30 feet apart. Also mentioned before, you will need repeaters or amplifiers to boost the signal of HDMI if you want to use it.
Compatibility
One of the many great things about SDI is its backward compatibility. HDMI does not have backward compatibility, which means you need an HDMI to VGA converter for the security key. This way, you can create a connection from the source to the destination. The reason for this is HDCP.
So, which connection should you use? It depends on what you need the cables for – a wide-scale video production or just to connect your laptop to a TV. If it’s the former, then SDI is the best option. If it’s the latter, then a simple HDMI connector is okay.
SDI is genuinely much better compared to HDMI, but no need to get it if you only plan to connect devices in short distances. You can invest in this SDI if you need to send audio and video signals over long distances.
SDI Signals and Their Differences
Now that you have an idea of the differences between SDI and HDMI, then you might be interested to know more about them. For instance, you might want to know the differences in various SDI signals and types of HDMI.
Image Source: by Jonathan Lang
In that case, let’s start with SDI signals.
The different types of SDI signals, as mentioned, are the 3G, 6G, 12G, Green G, Blue G, etc. What do all these mean? The answer is simple – the numbers you find before each G is the bitrates of video. So, for the 3G-SDI, the transfer of video per second is about 3 gigs. For 6G-SDI, it is 6 gigs of video data and 12 gigs for 12G-SDI.
The importance of how many gigs are allowed to transfer is crucial when it comes to video quality. How come? The higher the quality of the video, the stronger the signal it needs. With that, a connection that can transfer more video data is necessary. So, when you choose which SDI signal, consider the video quality you want.
For 4k videos, the best choices are 6G and 12G SDI. For 1080p videos, 3G-SDI is enough. Besides 6G-SDI and 12G-SDI, the other option you have for streaming 4k video is Quad Link SDI. Considered to be a monster SDI signal type, it allows you to take four 3G SDI signals. You can then bond those together, which equals to 12G.
HDMI Cables Explained
Next, we have different types of HDMI cable. Not all of them are equal, which means knowing them will help you pick the right connector. For the HDMI cables, there are five different types created for a specific application.
They are not like converters, which uses an HDMI plug on one end and a USB on the other. Converters, or adapters, give a computer, TV, or any device without HDMI port to have an output. With that, your gadgets can be used in various applications.
Here are the different types of HDMI cables:
Standard
This cable type is used in most home theatre applications such as LCD and LED TV monitors. You can use it reliably for transmitting 720p or 1080i videos. You can also use it for plush surround sound, connecting it from a device with HDMI output or is compatible with HDMI.
Standard with Ethernet
This cable is the same as standard HDMI cables in terms of compatibility. However, it has an added dedicated Ethernet channel. With the Ethernet, you can also provide your devices with an Internet connection. It is useful when streaming video using HDMI.
Standard Automotive
It is the standard cable’s automotive version. It comes with the same connectivity but has tougher outer cable insulation. Thanks to that, the cable has improved damage protection against pinching.
High Speed
This cable is for a more exacting specification. High-speed HDMI cables provide a connection for 1080p, 4k, 3D TV, as well as deep color. The downside is its ability to send more intensive signals will degrade over long distances.
High Speed with Internet
This cable is the same as the high-speed ones. They have the same configuration for 1080p, 4k, deep color, and 3D TV. However, it comes with the added feature of Ethernet connectivity for an Internet connection.
Conclusion
Comparing SDI vs. HDMI, you see that they are two vastly different connections. In terms of cost, type of connector, connection speed, cable length, and even compatibility, SDI seems better. But if you are only going to need to send audio and video signals in a home setting, an HDMI cable is more than enough.
See more: HDMI to SDI Converter
