Beginner’s Guide to Syphon

Syphon is a powerful technology that enables you to share ProPresenter’s features and functionality with other applications on the same computer, but often the documentation assumes you already know what it is. This is a basic overview of Syphon, and how to use it in ProPresenter.

Syphon Overview

Syphon is the best way of sharing live video between software on a macOS computer. It’s Mac-only, and similar to NDI in that they are both available for use as displays that are “virtual” (meaning there is no physical hardware attached). However, Syphon works internally on the Mac, without needing to send video signals over a network. Syphon can handle alpha channel, meaning it can handle transparency, and can work at any resolution desired (up to the limits of the computer’s graphics capabilities), not just common resolutions like 1920×1080.

As an example, Syphon may be useful if you’re using ProPresenter to generate lower thirds overlays, hashtag props, or lyrics to PVP3 on the same computer.

How to use Syphon

Syphon doesn’t need a special app or installed drivers. Instead, Syphon functionality is built into a video software by the developers. Under the hood, what Syphon does is allows the images created in the graphics card of one application to be shared directly by another application.

There are 2 parts: the Syphon Server which sends video, and the Syphon Client which receives it. ProPresenter has both of these built in, so it can send or receive Syphon signals.
Syphon is very easy to use. So easy, there’s not much info about it, so it can be a bit mysterious. In ProPresenter, open Screen Configuration, add a new screen, pick Syphon, and set the resolution. That’s it. Now if you open up a different app that can receive Syphon, like Simple Syphon Client, you’ll see the Syphon feed from ProPresenter.

What’s the difference between Syphon and NDI?

Syphon is different. Instead of being processed by the CPU, it’s processed in the GPU, and the actual whiteboard is shared by the Syphon Server to the Syphon Client. One software draws video frames on the whiteboard, while the other software is reading them at the same time. This means that Syphon has no perceivable latency, minimal CPU overhead, and doesn’t add much processing to the GPU.

Newtek’s NDI has become an incredibly popular way to send video over a network, between computers, cameras, and video switchers. It can also send video between software on the same computer, but there’s some benefits to using Syphon instead. NDI’s output is compressed and utilizes more of the computer’s resources to create a video stream. Further, NDI adds some latency (around 1 frame, or 16ms), and the compression means video quality isn’t quite up to par with Syphon.

Syphon video signals, by contrast, never leave the GPU. Images generated in the GPU by one application are automatically available to other applications. One app draws video frames, while the other is reading them. This means that Syphon signal has no perceived latency, is high quality, and uses minimal computer overhead.

Anything else to know?

• The Syphon website has a list of major apps with Syphon built into them.
• Syphon doesn’t support audio, only video.
• Syphon is a Mac-only framework, on Windows we recommend using NDI for virtual outputs.

Other Syphon Tools

Syphon Server/Client. Useful for testing, if you want to make sure you did something right.

AirServer. AirServer can receive AirPlay and Chromecast from tons of devices, and has a Syphon server built in. It’s an easy way to get an iPad or MacBook into ProPresenter.

Syphoner. Works like NDI’s Scan Converter/Screen Capture, but with more tools for cropping.

Syphon Webcam. Created by Troikatronix using OBS code, it’s the easiest way to turn Syphon into a webcam, so you can plug ProPresenter into Zoom or Skype meetings.

VLCSyphon. VLC with a Syphon server built-in. It’s old, but should still work on Intel-based Macs. If you have a new Mac with Apple Silicon, we’d love to hear your experience!

BlackSyphon. Send Syphon directly to Blackmagic Design outputs, like DeckLink cards and UltraStudio hardware.

ISF Editor. A Swiss army knife for modifying Syphon video live, including creating your own GLSL shaders.

NDISyphon. Converts video signal from Syphon to NDI and vice-versa.

Symon. A simple Syphon client, but with a couple extra features, like the ability to full screen. It’s useful if you want Syphon to completely take over a screen connected to your computer.