In my last post I talked about some of the decision process I used when exploring which video platform to use a series of online office hours for ecommerce. In this post I focus on some of the underlying technologies. It was interesting to see how the complexity can blow out pretty quickly. There are lots of interesting things you can do, but they don’t always all work together as you plan.

Aug 09, 2010 Idk about the streaming portion. Bootcamp is a great alternative, but so is VMWare Fusion or parallels. It allows you to run an instance of windows, while inside of Mac OSX.

Find and compare Live Streaming Software for Mac. Free, interactive tool to quickly narrow your choices and contact multiple vendors.
Once you have decided on the broadcasting software and had a chance to get things rolling you can expand on your broadcast capabilities with the following sites that provide various services and tools. Once again we recommend taking some time to research and making a decision based on what you need.

Input and Output Streams

It may be obvious to most, but it took me a moment to realize that applications can read from the microphone or camera, and can send output to the speakers or screen, but that does not mean you can do a UNIX pipe command between them. That is, on Mac and WIndows you cannot just hook the audio/video output of program 1 to the input of program 2.

Xbox Streaming App For Mac

There are some 3rd party utilities around that make this possible, such as “Virtual Cable”. BlackHole and Soundflower are example applications on Mac that can connect the audio output of one program to the microphone of another, if you can tell the application to use different “speakers”. (BlackHole etc appears alongside speakers and headphones as the output device. You select that and the audio output goes to BlackHole. The second application then selects a Microphone called BlackHole from which it gets the audio stream.)

Similarly there are programs that can do this with video, such as CamTwist on the Mac. They can create a virtual camera for other applications to use as an input video stream. This allows, for example, the output of CamTwist to be fed into the camera for Google Meet, Skype, etc. The application thinks its just using a different video camera.

There is also OBS Studio (and others) that can watch a part of the screen and capture that, turning it into a video feed. This is useful for example when streaming game play by streaming directly to YouTube, Twitch, etc. But they can also be used to generate a camera source.

I am not trying to exhaustively list such tools, just be aware that they exist. There any many options out there and I would suggest reading some knowledgeable reviews before selecting one. Also be aware that cameras and microphones are separate devices, so you may need to connect up video and audio separately.

Audio Processing

One example of wanting to stream audio through another application is to improve audio quality. Using applications such as Audacity (free) or Adobe Audition (paid) you can apply various audio processing techniques like filtering and noise reduction. This can improve the quality of the sound coming from your microphone (e.g. to remove fan noise, or adjust bass and treble levels). There is some skill to doing this, so it is better to do whatever you can to avoid the noise in the first place.

There are lots of instructions out there on how to do sound processing. For example I watched a really interesting one on removing hum. It used a notch filter where you could control the frequency of what to amplify or silence. It showed by amplifying the notch first you could drag the frequency up and down the frequency range and it would amplify the hum when you found the frequency it was at. You then drag that point down so instead of amplifying it quietened that frequency. Once explained it was pretty easy to do. There are lots of people out there sharing their knowledge like this if you look.

NDI

As I hobby I play with Adobe Character Animator, animation software for simple cartoons. It’s a bit of fun. But it also introduced me to NDI. Character Animator on Windows has the ability to generate a live video stream in NDI format. Other tools can there convert NDI into a camera source (e.g. using the NDI utility “Virtual Input” from NewTek).

On the Mac, there is standard for video streaming called Syphon, but it is not cross machine. Character Animator 3.2 (at least) can output Syphon directly on Mac, so running Character Animator and the video conferencing software on the same machine does not require NDI. If run on different machines, then NDI can be used to stream the video between the two machines.

There is also a useful tool for Mac called “NDI Syphon” which can listen to a NDI stream and convert it to a Syphon stream. The reason I explored Syphon was CamTwist can read a Syphon stream and turn it into a virtual camera, allowing most software using cameras read the stream as if it was a physical camera. For example, it allows me to feed the Character Animator video stream into a camera to use on a call (Character Animator -> NDI Syphon -> CamTwist -> Skype).

NDI is also supported by Skype. Skype on the Mac supports NDI streaming – you can turn a flag on and generate a good quality video stream for other programs to read from. (I believe this produces better quality than using something like OBS to do screen capture of the Skype window.) On windows you need to make sure you get the “Skype for Content Creators” edition as the default version does not include NDI Support.

NDI Discovery

One of the nice (and painful) things about NDI is it uses mDNS (multi-cast DNS, aka Bonjour on Mac) to allow NDI streams to broadcast their existence and have other machines on the same network learn and automatically display them in lists of NDI sources. Just start a NDI Test Pattern application on your Windows laptop and other programs on your Mac (on the same subnet) can just see it appear (after a few seconds).

If you need cross subnet support, you can still do it, but you start needing to manually register IP addresses of other hosts, or have a directory server permanently running. This can be useful for more serious video processing shops, like a TV station.

And this is where I hit a blocker for longer than I care to remember in trying to make it work from my office hours.

MacOS NDI Streams Not Discoverable !?#?#!

My problem was I could start applications generating NDI streams on Windows and they would be visible on my Mac and Windows laptops. However, when I created NDI streams on my Mac it seemed to work one day, then a day or two later it stopped working.

One useful utility to debug the problem was “Discovery” which displayed the contents of the local mDNS server. (The application is available for Windows and iOS as well.) I discovered using this that the Mac programs where creating an entry in mDNS, but the entry seemed to be empty! The Windows entries included the host and post to read the NDI stream from.

Why the strange “AJK=MAC” hostname? That was a typo by myself. My work laptop was including a long domain name including names like “roam” in the domain name. This name however did not exist in DNS servers or /etc/hosts. It was just a name given to my laptop. (Hostname was set to a fully qualified domain name, which is generally not recommended, so I tried the above trick of shortening the domain name).

My final solution that started working was to change the hostname to “ajk-mac.local” and then manually enter that with the IP address allocated by my wifi in my /etc/hosts file. (There might be a better option, but this worked for me.)

My theory is the code tried to resolve the host/domain name into an IP address but failed. As a result the mDNS entry was incomplete and sources on my Mac would not be discoverable.

Latency

Of course using all these tools adds no CPU overhead or lag to your streams.

Scratch that!!! It can actually be very painful using these programs as it almost seems to work, except now the audio and video do not quite line up any more. This is where OBS Stud

Streaming Tool For Mac