>An event, implementing the AudioProcessingEvent interface, is sent to the object each time the input buffer contains new data, and the event handler terminates when it has filled the output buffer with data.
Events just fire like mad until you put stuff in the output buffer. Couldn't get it to work like I needed it to.
MediaRecorder works the same way (but for MediaStreamSources, not BufferSources).
the idea is that audio buffers are processed in chunks- an event fires for each chunk that is processed. the act of "recording" is just reassembling these chunks into a single ArrayBuffer.
edit: seems like Recorderjs works exactly this way (but implements features more than just recording, like exporting as WAV).
capturing the chunks: https://github.com/mattdiamond/Recorderjs/blob/master/src/re...
reassembling the chunks: https://github.com/mattdiamond/Recorderjs/blob/master/src/re...
This is the key I was missing in my implementation. Another challenge is wiring this up to multiple OscillatorNodes - the docs say a ScriptProcessorNode can only have one input. In my implementation I create a new OscillatorNode whenever you press a key.
If you do it that way, you just need to attach the recorder to the master output of the mixer.
it's also decent practice to send your oscillators into a mixer anyway so that they can be rerouted at large.
for instance, say you have 4 oscillators, 2 fx buses and an output. you route (4 oscillators) -> mixer -> fx bus 1 -> output. then if you want to switch the fx bus for your oscillators, you can just reroute the mixer instead of each oscillator individually.
in the case of a recorder, you'd want the end of your entire graph to look like this: mixer -> recorder -> output. this way your recorder is capturing all audio (oscillators, effects, etc). (and, as noted above, you have the option to reroute the mixer directly to the output when it's not recording).
You could have it as simple as 1 gain node for each channel which you use for input and output to the mixer master gain. This would make it difficult to add fx later though.