SDI vs. HDMI: What are their Differences

There are numerous ways of sending audio and output signals to a PTZ streaming camera, but the most common methods are with SDI and HDMI cables. However, till date, there is still a debate about which is best between these two distinctive methods. So, in this post, we will be discussing the differences between SDI and HDMI connections to know which is better.

What is SDI?

Serial Digital Interface
Source: Shutterstock
SDI is an acronym for Serial Digital Interface. It is a standard for digital audio and video transmission over coaxial cables. The SDI is a professional video connection that is preferred in production environments because of its outstanding properties, such as its length. It has a length range of 300 feet, which makes it suitable for production and outdoor environments. Also, it comes with a BNC cabling, a strong mechanical structure that ensures that the SDI remains connected despite tough turbulence. This helps to avoid disconnection during live stream broadcasts.

History of SDI

The development of the first SDI professional video standard can be dated back to 1989. This was done by the Society of Motion Picture and Television Engineers (SMPTE). After that, some updates have been made. Below are the SDI versions in the production order.

Standard Definition SDI (SD-SDI): It was first developed in 1989. It transmits video and embedded audio at bit rates ranging from 177 Mbps and 270 Mbps. It is mostly used for 480i and 576i video formats.

High Definition SDI (HD-SDI): It was first developed in 1998. It transmits video and embedded audio at a rate of 1.5Gbps and is mostly applied for 720p and 1080i video formats.

Enhanced Definition SDI (ED-SDI): It was first developed in 2000. It transmits video and embedded audio at the rate of 540 Mbps. It is mostly applied for 480p and 576p video formats.

Dual Link HD-SDI: It was first developed in 2002. It transmits video and embedded audio at a combined rate of two 1.5 Gbps, making a total of 3 Gbps. It is mostly applied for 1080p videos.

3 Gbps SDI: It was first developed in 2006. It transmits video and embedded audio at 3 Gbps bit rate. It is mostly used for 1080p videos.

6 Gbps SDI: It was first developed in 2015. It transmits video and embedded audio at 6 Gbps bit rate. It is mostly used for 1080p video formats at 60 frames per second and 2160p video formats at 30 frames per second.

12 Gbps SDI: It was first developed in 2015. It transmits video and embedded audio at a bit rate of 12 Gbps. It is generally used for 2160p video formats at 60 frames per second.

Different Types of SDI Signals

The most common types of SDI signals are 3G, 6G, 12G, and quad link SDI. The numbers in front of the Gs are the bitrates of the video. In a simpler form:

3G: The transfer of video per second is 3 gigs.

6G: The transfer of video per second is 6 gigs.

12G: The transfer of video per second is 12 gigs

Quad link SDI: Some people call this the “monster SDI signal.” This is because it enables you to take four 3G SDI signals at once. When you add them together, you will get 12G.

To stream 4K videos, the best SDI signals to use are 6G, 12G, and the quad link SDI.

What is HDMI?

High Definition Multimedia Interface
Source: Shutterstock

HDMI is an acronym for High definition Multimedia Interface. It’s a video standard that’s used to transmit uncompressed video and embedded audio signals to any device that is capable of displaying or encoding videos. HDMIs are popularly used in consumer and prosumer environments. It is a highly favored connection cable because it is compatible with both consumer and professional devices. However, it is limited in length. It can only run up to 30 feet. For a longer range, you will need an amplifier.

History of HDMI

Unlike SDI which was developed by a broadcasting industry to be the best method to transmit videos, HDMI was developed by a myriad of consumer electronics companies, cable providers, and movie producers.

 

Initially, the intention of these companies was not to develop a cable that can transmit both audio and video signals over a single connection. All they needed was a means to protect their content so that they won’t be plagiarized. In doing so, they standardized the use of HDCP (High-bandwidth Digital Content Protection) across all of their components. It’s a security standard that requires that the source device, such as a BlueRay player generates a security key so that the TV will be able to display your content. This is a tight protection that necessitates a handshake between the source device and the output device. This is the reason why most TVs won’t show an HDMI input on their source list if nothing is plugged in.

Different Types of HDMI Signals

There are different types of PTZ cameras with HDMI output. This means that knowing them will help you while choosing the right one for your use.

Here are the different types of HDMI signals:

Standard HDMI: You will find this in most home theater applications, like LCD and LED TV monitors. It can be used to send 720p or 1080i videos. Also, you can use it to get high-quality sound by connecting it to a device that has HDMI output or is HDMI compatible.

Full HDMI: This is a cable that’s designed for a more exacting specification. It provides a connection for high-resolution videos as well as deep colors. It also comes with an Ethernet feature for internet connection purposes.

HDMI with Ethernet: In terms of compatibility, this cable is identical to the standard HDMI. It does, however, have a dedicated Ethernet channel. It can also be used to provide an internet connection for your gadgets, as well as perform highly when streaming video using HDMI.

Mini HDMI: This is a smaller, slimmed-down version of the standard HDMI. It’s commonly found on several types of portable equipment, such as DSLR cameras, large tablets, and camcorders. It shares the same functionality as the standard HDMI, but in a compact package.

Micro HDMI: It’s smaller than both the standard and mini HDMI, but it retains the same functionality. The micro HDMI is specifically designed for small, highly portable devices like mobile phones.

How to Choose HDMI Types for Your Use

The main factor to consider when choosing the best HDMI type for you is your need and available device. Are you using it for professional purposes, like home theater, or is it for personal use on a mobile phone? The answer to this will help you choose the right type of HDMI.

What are the Differences between SDI and HDMI?

A lot of cameras, including Telycam webcams and PTZ cameras, are manufactured with SDI and HDMI connection interfaces. These two connection interfaces are quite different and so are their applications. In the next series of paragraphs, we will highlight the major differences between SDI and HDMI.
SDI ptz camera 1
Source: telycam

Advantages

SDI cables are preferred because of their simple and reliable design. Also, they are very durable and easy to repair in the event of damage. However, the major advantage that makes SDIs stand out is the strong locking mechanism provided by the BNC cabling. This prevents the cable from disconnecting no matter how harsh it’s controlled. This is why it is used in broadcasts and outdoor environments where the subject and camera are moving frequently.

 

On the other hand, HDMI cables are preferred because of their popularity and simplicity. They are mostly used by consumers which makes them more familiar. Also, HDMI is usually used for different applications in homes.

Disadvantages

While the SDI cable seems to be taking all the credit, there is a risk attached to its strong locking mechanism. When there is an accident, they will remain attached to the connected devices, which will cause mass damage. This can happen to even well-structured establishments like this.

 

The biggest drawback of the HDMI is the weakness of the locking mechanism. The connection is very fragile and any accidental bump can bring your live stream to a stop. This occurrence can make your audiences lose interest in your program and go for other alternatives. Also, the disconnection can cause great damage to your expensive equipment and this is not even to mention how difficult and expensive it is to repair HDMI cables.

Application

SDI cables are mostly applied in situations where you cannot risk interruption or disconnection of your live stream like crowded events or outdoor venues with wildfire and harsh weather. The tight locking mechanism guarantees that the connection stays strong. In fact, some professionals don’t risk having HDMI cables in indoor venues, so they use an SDI cable. Also, they are applied in large spaces because of their long length.

 

On the other hand, HDMI cables are quite short in length, so they are commonly used in small rooms with clear pathways and controlled movement because of the flimsiness of their locking mechanism.

Quality of Video

SDI was developed by a broadcasting company with the main aim of providing the best video quality, which they achieved. SDI is a one-way, multiplexed standard developed to transmit the highest quality of video over a coaxial cable. The video quality produced by SDI is flawless.

 

HDMI, on the other hand, was primarily developed by movie producers, electronics companies, and cable providers to safeguard their content. Their intention was not to produce high-quality videos, hence HDMI cables fall short of transmitting ultra high-resolution videos like 4K videos.

Maximum Cable Length

SDI cables can be as long as 300 feet, while the maximum length that an HDMI cable can be is 30 feet. This makes SDI more applicable in digital video broadcasting and familiar applications where connected devices will be separated more than 30 feet away. However, HDMI length can be increased by using amplifiers or repeaters.

Bandwidth Used

The bandwidth varies according to the type of SDI and the type of HDMI. However, generally speaking, the SDI comes at the top for this section. You can have an SDI cable that supports as much as 12Gbps, but HDMI only supports as much as 5Gbps.

Cable Capacities

As earlier stated, SDI cables have BNC connectors that ensure that the connection is not pulled out. In fact, it is very strong that it has to be rotated to uncouple the connector from the port. This definitely cannot be done by accident; it must be deliberate. But HDMI doesn’t have this. At the sight of any turbulence or wind, they can be disconnected.

Cost

SDI cables are made up of standard coax cable (RG-6), which is readily available and relatively cheaper than the proprietary cable used for HDMI. SDI allows you to reduce costs and save more.

Speed of Video Transmission

The security system of the HDCP protocol used in developing HDMI mandates that when an HDMI device is connected and powered to the camera, the two devices must communicate with each other. This is called a “handshake.” This is compulsory as it is part of the protection standards of the HDCP protocol. The two devices report to each other to check if they are compatible or not.

 

Well, this is a problem because if the signal going from the camera to the device drops below the expected level, the two devices will need to start another connection establishment. And this delay cannot be tolerated in a live event as it will stop the broadcast.

 

Luckily, SDI is not developed with HDCP, hence it doesn’t need to go through all these steps to secure a strong connection. This is why it is preferred for live stream events.

Connection Speed

This is similar to the point above. HDMI only responds after it has complied with the standards of the HDCP. The several HDCP protocols slow down the connection speed of the HDMI. But SDI responds quicker and smoother while it is even switching videos.

Compatibility

Another thing SDI boasts of is its backward compatibility. HDMI, on the other hand, does not have backward compatibility. For the HDMI to be compatible backward, you need a VGA or HDMI converter to get the security key. With this, you can establish a connection from the source to the receiving device. This is another effect of the HDCP.

Time Code

HDMI does not support time code, while SDI transmits video signal and time in one single cable.

Connector difference

HDMI connectors are similar to a USB that can be easily unplugged intentionally or not. They don’t have a tight lock which makes them very easy to remove. SDI, on the other hand, has strong connectors that are held in place by BNC cabling. HDMI cannot be used in places where there are a lot of connected wires. This is because while trying to remove another wire, the HDMI connector can be affected.

HDMI vs. HD SDI: What are their Differences

Shortly, we will consider the differences between HDMI and HD SDI PTZ. There are quite a lot of things that separate these two connection cables, but we will focus on 5 major factors that encompass all other factors.
3G SDI
Source: pinterest

Pros

HDMI, even though it was not created with the intention of transmitting data, one of its salient benefits is that it helps to secure personal content. Due to the protection provided by the HDCP, there is a hard wall separating your content from plagiarizers.

 

HD-SDI was created with the intention of providing the best way of transmitting high-quality data quickly from the camera to the receiving device. The cable was designed with all preciseness to carry out its function perfectly, and it works in situations where HDMI will falter.

Cons

HDMI’s primary disadvantage is that it can be easily disconnected due to some unintentional touches, thereby causing a stop in the live stream. Another disadvantage is that it’s limited by length. You can use it for a large room unless you add amplifiers or repeaters to it. One other drawback is that it cannot really be trusted with very high-quality data as it is very slow in transmission and won’t produce the desired quality.

 

The major drawback of the HD-SDI is that if it’s going to get damaged, it takes other connected devices with itself.

Mechanical (Connector)

HDMI has a different mechanical design. The connectors used for HDMI cables are less-reliable to SDI. HDMI connections can be likened to USBs; they are flimsy and can’t be locked in place. They will definitely get disconnected due to a little pressure.

 

SDI, on the other hand, is made with a stronger and more reliable cable. It is locked by BNC connectors that guarantee continual connection no matter the pressure it’s faced with.

Quality of Video

A major reason why HDMI is used by consumers and not professionals is that it cannot produce the desired quality. HDMI produces a lesser video quality when compared to SDI. It cannot be trusted with high-resolution videos.

Bandwidth Used

Once again, SDI comes top. The bandwidth used by HDMI is lower than SDI’s. This means that SDI transmits more data rate per second when compared to HDMI. SDI can transmit as much as 12G per second, but HDMI can only handle 5G per second.

When to Use SDI

SDI is ideal for a venue that’s filled with people like concerts and sporting events. Also, it is suitable for outdoor venues with wildlife and strong wind as you wouldn’t want your broadcast to be interrupted by the disconnection of your connection cable. This is also why they are used for important broadcasts like emergency declarations.

When to Use HDMI

HDMI should be used only for indoor events where you know that you can control the crowd and restrict people from interfering with your connections. If they are used in other applications, there is a high risk that your connection will be mistakenly interrupted, which will upset your audience.

Is SDI Better than HDMI

Neither SDI or HDMI are better than each other. In this context, the definition of better will be determined by your streaming application. If you need a connection cable for outdoor venues streaming, then SDI is better. But if all you need is a connection cable for a small indoor event, you can go with HDMI.

Reliable PTZ Camera Manufacturer for Your SDI and HDMI Productions

telycam logo
Source: Telycam

To have the best SDI and HDMI productions, you need to partner with one of the best PTZ camera manufacturers that know the in-and-out of video outputs, connection interfaces, and live streaming. Telycam does not just provide PTZ cameras, but also offers high-quality wholesale webcams that are compatible with different types of connection cables, including SDI and HDMI. If you are in need of the best SDI and HDMI cables for your production, reach out to them.

Other Questions

What is the Difference between SDI and DVI

SDI (Serial Digital Interface) and DVI (Digital Video Interface) are both related, however, the difference that exists between them is that DVI can only transmit videos, while SDI can transmit videos and audios. Another difference is that DVI supports the use of HDCP (High Definition Content Protection). Movie producers who want to protect their content usually use this against unauthorized copying.

What is the Difference between ASI vs. SDI

ASI (Asynchronous Serial Interface) is a cable that is capable of transmitting COMPRESSED data that include multiple programs. SDI, on the other hand, is capable of carrying UNCOMPRESSED data that consist of a single program.

Both of them are compatible with BNC connectors, but they cannot be used interchangeably.

What is the Difference between DVI and HDMI

DVI and HDMI are very similar in the sense that they both support the use of HDCP for protecting people’s content from plagiarism. However, despite DVI backward compatibility with HDMI, it cannot transmit audio data. DVI is primarily designed for video data.

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