How to Extend Video

Written by Terry Doner, July 23 2019. Updated on December 4 2020.

A commonly asked question goes something like this. “I have a computer at Front-of-House (FoH) and I need to run a signal to a projector that is 35 metres away. What do I need?”.

The source is usually an HDMI source and the first thing to note about standard HDMI is that it maxes out around 10m, for best reliability limit hdmi runs to 2m.

There are several basic choices for how to solve this.

1. Long-run HDMI cables

2. Convert to SDI

3. Convert to HDBaseT

4. Category Cables with HDMI Transmitter/Receiver

5. Network Solution / NDI

6. Wireless Video

7. ATSC

One key driver to your decision is what else you might need to accommodate in you long term plan. Is this the only thing you will ever want to do or will you want to do other things in the future. These other things might influence the flexibility you design into this choice.

Examples:

Do you ever plan on adding a video matrix switcher?
Do you plan on replacing your projection equipment which might have built-in support for SDI or HDBaseT?
Do you plan on adding a video mixer which might have built-in support for SDI?

When I went through this process for myself, I knew I would want all of that. I chose SDI for cameras to video mixer. HDBaseT for long haul video distribution and HDMI plus SDI for short haul around the FoH position (depending on the native support for the devices).

1. Long-run HDMI cables

These cables are good up to about 30 metres. Although it could be a valid choice, it is trying to make something happen that is outside of spec. I feel it could leave you vulnerable to some change that renders the solution inoperative. There are reports of this solution working fine, and others which failed. I have heard good reports about hdmi-optical solutions such as the “Kramer Electronics Active Optical HDMI Plenum Cable”.

I don’t have direct experience with any of these products. I suggest you google "long hdmi cables” and go from there.

Read this whitepaper: https://res.cloudinary.com/avd/image/upload/v1617813563/Resources/C2G/Cables%20and%20Connectivity/Literature%20and%20Reference/210190-C2G-HDMI_AOC_Extension-Whitepaper_2_1.pdf

2. Convert to SDI

SDI is a broadly used standard for video transport. For 1080p60 content look for “3G-SDI” rated gear and cables. The standard cable is RG-6 cable and is good for about 100m. Belden 1694A and 1694F are examples of the cable. For distance above that you can use fibre and it can run pretty much unlimited.

“Consider a product like "Blackmagic Design Micro Converter HDMI to SDI (with Power Supply) “ and its companion product " Blackmagic Design Micro Converter SDI to HDMI - CONVCMIC/SH”

This is a good reference for picking cables. BTW, there is a guide for all of that here: https://www.joelwsmith.com/sdi-cables .

Want to make your own cables: https://youtu.be/BfLjYFq6vCI

SDI can also be run over fibre. I didn’t cover fiber optics this article, but here is a good video on the topic:

3. Convert to HDBaseT

HDBaseT is much newer than SDI. https://en.wikipedia.org/wiki/HDBaseT . It can use category 5e or higher cable; this cable is sometimes called ethernet cable because it is commonly used for ethernet networking, but HDBaseT is not ethernet.

The length limit is about 100m.

HDBaseT makes the most sense if the equipment you are buying has it already built-in as many Pro level projectors do. Also HDBaseT is makes sense if you need to support HDCP video.

Products:

Kramer TP-580T and TP-580R

4. Category Cables with HDMI Transmitter/Receiver

These solutions are all proprietary. Don’t plan on using mixing up transmitters and receivers from different manufacturers.

The length limit varies by the specific products and range between 30m and 100m.

I don’t have specific gear to recommend for this. Take a look at things like "Kanexpro HDMI Extender over Cat6"

5. Network Solution / NDI

There are several video-over-network solutions (NDI, NDI-HX, rtmp, Dante AV, ST2110 or ST2022-6 and a few others), as of 2019 for general distribution in smaller venues the only practical choice for this application is NDI. To make this work you need conversion boxes at each end and a robust network. A gigabit switch is recommended, if you are sharing this switch with other workloads or want to do multicast, you might consider a managed switch. You need about 100 Mb/s per video link. Some boxes are Power-over-Ethernet cable (PoE) but in this application it might not be beneficial.

Your ethernet cables have a maximum limit of 100 metres, but 80 metres is a safer choice. You could hop through a second switch to gain extra distance (tradeoff for a little more latency).

One advantage of the NDI approach is the ability to transmit the video stream to multiple endpoints without a splitter or matrix.

Computers can be both the source and destination of an NDI signal.

See the NDI Overview , also on this site, for further details on NDI implementation, included a list of supporting hardware and software.

An example of a managed ethernet switch:

Cisco SG350-10 10-Port Gigabit Managed Switch

6. Wireless Video

The main factors in making a choice are: range, latency, resolution, and cost. This is a sample of some gear. Details for most these can be found at https://www.bhphotovideo.com/

The Hollyland models are popular budget choices, one feature on some of their models is the ability to monitor the signal from a tablet of the iphone. Another detail that may matter to you is that some of the Hollyland units convert frame rates to a subset, which may be a problem if you are using some ATEM models which require all inputs to be on the same frame rate. More specifically if you set your camera at 29.97, the Hollyland with convert that to 30 fps.

Wireless Video Gear

Further Information

Some videos for more details :

7. ATSC

I haven't much to say about ATSC signal distribution yet. In summary, ATCS modulators are devices that let you become your own cable TV broadcaster. The appealing part of this approach is that all of the consumer TVs that you would buy today already have ATSC decoders built into them.

Here is an example of one such device. This one is a two-channel system so you could distribute two different 'channels' of video over a single cable.