Programmare dal vivo

The :sound_in synth as described in the previous section provides a very flexible and familiar method for working with input audio. However, as also discussed it has a few issues when working with a single input of audio as a single instrument (such as a voice or guitar). By far the best approach to working with a single continuous stream of audio is to use live_audio.

A Named Audio Input

live_audio shares a couple of core design constraints with live_loop (hence the similar name). Firstly it must have a unique name and secondly only one live_audio stream with that name may exist at any one time. Let’s take a look:

live_audio :foo

This code will act in a similar fashion to synth :sound_in with some key differences: it runs forever (until you explicitly stop it) and you can move it to new FX contexts dynamically.

Working with FX

On initial triggering live_audio works exactly as you might expect it to work with FX. For example, to start a live audio stream with added reverb simply use a :reverb FX block:

with_fx :reverb do
  live_audio :foo
end

However, given that live_audio runs forever (at least until you stop it) it would be pretty limiting if, like typical synths, the live audio was bound within the :reverb FX for its entire existence. Luckily this is not the case and it was designed to be easy to move between different FX. Let’s try it. Run the code above to hear live audio coming directly from the first input of your sound card. Note, if you’re using a laptop, this will typically be out of your built-in microphone, so it’s recommended to use headphones to stop feedback.

reverb,

with_fx :echo do
  live_audio :foo
end

Now, hit Run, and you’ll immediately hear the audio played through the echo FX and no longer through reverb. If you wanted them both, just edit the code again and hit Run:

with_fx :reverb do
  with_fx :echo do
    live_audio :foo
  end
end

foo

Stopping live audio

Unlike standard synths, as live_audio has no envelope, it will continue running forever (even if you delete the code, just like a function is still defined in memory if you delete the code in the editor). To stop it, you need to use the :stop arg:

live_audio :foo, :stop

It can easily be restarted by calling it without the :stop arg again:

live_audio :foo

Additionally all running live audio synths are stopped when you hit the global Stop button (as with all other running synths and FX).

Stereo input

With respect to audio channels, by default live_audio acts similarly to the :sound_in synth in that it takes a single mono input stream of audio and converts it to a stereo stream using the specified panning. However, just like :sound_in_stereo it’s also possible to tell live_audio to read two consecutive audio inputs and treat them as the left and right channels directly. This is achieved via the :stereo opt. For example, to treat input 2 as the left signal and input 3 as the right signal, you need to configure the input: opt to 2 and enable stereo mode as follows:

live_audio :foo, stereo: true, input: 2

Note that once you have started a live audio stream in stereo mode, you cannot change it to mono without stopping and starting. Similarly, if you start it in the default mono mode, you can’t switch to stereo without starting and stopping the stream.