‘Like a mighty stream’ part 2: External video and audio

7 minute read

Part of a series on live-streaming

  1. Your first stream
  2. Cutting in recorded video and audio
  3. Microphones and sound
  4. Cameras
  5. Streaming platforms and scheduling
  6. Text overlays and countdowns
  7. OBS settings for improving quality
  8. Embedding your video in your website
  9. ???

In my last blog, we created our first live-stream. Today I want to work on the biggest thing that using OBS allows you to do, which is to cut in external video and audio sources into your stream. This will allow you to bring in other people’s voices, such as bringing in an external preacher or an external reader. For an example, have a look at what we did at Bourne Street for the Easter Vigil.

We had our preacher by audio and video. We had the lighting of the candle pre-recorded outside on a previous day, because there was no way we could do it on the go. We had the vigil readings and chants cut in, with the external audio laid over our live video feed. And, lastly, have a look at a Sunday live-stream, when we cut a recorded video of the statue of Our Lady in, but use the live audio from church for the Regina Coeli (from 50:20). All three options are useful at different points.

Let’s start with the concept of scenes. In the bottom left of the OBS window, you have a ‘Scenes’ box. This allows you to prepare sections of your stream, so you can just click on them and the appropriate stuff all happens at once. Each scene is made up of one or more ‘sources’, which are shown in the next box over. Sources are video or audio (plus occasionally things like text and images). You can add new scenes by clicking the ➕ button and rename existing scenes by right-clicking on them and choosing ‘rename’. We added a ‘webcam’ source in back in the last blog.

The "Scenes" and "Sources" menus

But let’s start with something counter-intuitive: we’re going to disable the existing audio feed. This is because it is ‘global’: that means it is always on, no matter what scene we are on. This is not useful behaviour for what we’re doing, becuase you would still be able to hear the microphone input over your stream, even when you’re playing a video. To disable it, just click the ‘mute’ icon next to the ‘Mic/Aux’ option in the audio monitor. You should do the same thing for ‘Desktop audio’: this is what allows you to stream the sounds that are coming out over the speakers on your computer: I can’t think of a situation where it’s appropriate in a church stream.

The audio mixer with some sources silent

When you’re on a scene where you want the microphone audio, you can add it back in. Click the ➕ and go to ‘Audio Input Capture’. You should then be able to choose ‘Default’ and click ‘OK’ and the audio feed will work as before. If you have any trouble – or if you have a more complex audio setup, as we’ll discuss in part 3 – you might need to try the various different options here to see which is the right one.

Now let’s say we want to include some external video. We click the ➕ icon like we did before and choose ‘Media Source’. As before, we can give it a name. (One odd behaviour of OBS: you can’t give the same name both to the scene and the source.) You will then see this dialogue box:

The media source menu

Here you can choose which file you want to include. Click ‘Browse’ and find the video file on your computer. There are two key settings here. The first is ‘Restart playback when source becomes active’: this means that you will always start from the beginning of the video when you start the scene, rather than picking it up where you left off last time you opened it. The other is ‘Close file when inactive’. This means that your computer will take the video out of its memory when you’re not watching the video. It might make it take a tiny bit longer in starting, but it will mean the rest of the time you have more resources available. On a fast computer you can get away with this off, but on a slower one it makes a big, big difference.

Now we click ‘OK’ and the source will appear on our screen. You might need to resize it to fit: the quick way is to click on it and then do Ctrl+F, which ‘fits’ it to the screen. (If you’re reducing the image size, that’s fine; if you’re stretching it, you will see a noticeable reduction in quality.)

The video will immediately start playing. You can adjust the volume with the volume slider in the audio settings, just as you can with the microphone.

You might end up with a source panel that looks like this:

The media source menu

You can see we have the video, on top of the webcam feed, with the computer’s microphone part of the mix as well. We don’t want the microphone or the webcam feed while this video is playing, so we can remove the two sources we don’t want with the ➖ button.

So that’s what we do when we want to cut an external video into the feed.

One last important thing to do is to turn on ‘monitoring’ so you can hear what’s happening on the feed. Hopefully you’ll be able to see the computer while the external source is playing, but it’s still useful to have the audio feed audible. Click on Edit and then ‘Advanced Audio Properties’. There you need to find the source that you want to be audible and change it from ‘Monitor off’ to ‘Monitor and output’. This means that the sound goes out to the world (‘output’) and also gets played on your computer (‘monitor’).

It is really important that you muted the Mic/Aux and Desktop audio sources earlier, or you will end up with horrible feedback!

If you want a video to be played but no audio heard, you do exactly the same as before, but click the little mute icon by your video source in the audio mixer and add your microphone source back in.

If you want to import external audio but not video, you can import a MP3, AAC, OGG or WAV file. You cannot import an M4A file, which is what iPhones record. To use those, you have two options. Either you can convert the audio file (probably to MP3), or you can install the VLC media player, which will then appear as an option in the sources list and which supports M4A files. (You can ignore the fact that it talks about being a ‘video’ source: it can do audio files too.)

Finally, you can very easily add still images to your feed by doing ➕ and choosing ‘Image’. I use these for before the service starts and after it ends, so the stream has a gentle beginning and end.

With all these things, you can build up any number of sources at any given time in any scene, though I’d caution against trying to mix recorded audio sources live – the audio sources will not reliably sync up. When the time comes in your live stream, just click the scene you need and it will start.

When I am streaming, my ‘scenes’ list looks like this:

The media source menu

You can see a ‘Video’ scene: this is my main camera, with the normal audio. This covers 95% of the feed. ‘Spiritual Communion’ has a text overlay on top of this, which I’ll cover in a later blog, as I will the ‘Countdown’ concept. The ‘Image (silent)’ source is for the end of mass: it’s just a plain image with no audio sources selected and is also what I click on if everything has suddenly fallen to pieces. ‘Black (with sound)’ has a plain black screen with the main audio feed playing: I use this occasionally if I want to move the camera during mass because it looks horrible to move it live. Finally, ‘Mary’, as discussed before, has the video file of Mary (set to mute) and the main audio source to go with it.

I think that’s the basics of bringing external sources in: it really isn’t very difficult, but you can do a lot of things.

Let me know how you get on – if you use any of what I’ve written about in your streams, I really want to see them!

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