Web Audio- Chaining buffers that are being dynamically written

Question

This is sort of expanding on my previous question Web Audio API- onended event scope, but I felt it was a separate enough issue to warrant a new thread.

I'm basically trying to do double buffering using the web audio API in order to get audio to play with low latency. The basic idea is we have 2 buffers. Each is written to while the other one plays, and they keep playing back and forth to form continuous audio.

The solution in the previous thread works well enough as long as the buffer size is large enough, but latency takes a bit of a hit, as the smallest buffer I ended up being able to use was about 4000 samples long, which at my chosen sample rate of 44.1k would be about 90ms of latency.

I understand that from the previous answer that the issue is in the use of the onended event, and it has been suggested that a ScriptProcessorNode might be of better use. However, it's my understanding that a ScriptProcessorNode has its own buffer of a certain size that is built-in which you access whenever the node receives audio and which you determine in the constructor:

var scriptNode = context.createScriptProcessor(4096, 2, 2); // buffer size, channels in, channels out

I had been using two alternating source buffers initially. Is there a way to access those from a ScriptProcessorNode, or do I need to change my approach?

Answer 1

No, there's no way to use other buffers in a scriptprocessor. Today, your best approach would be to use a scriptprocessor and write the samples directly into there.

Note that the way AudioBuffers work, you're not guaranteed in your previous approach to not be copying and creating new buffers anyway - you can't simultaneously be accessing a buffer from the audio thread and the main thread.

In the future, using an audio worker will be a bit better - it will avoid some of the thread-hopping - but if you're (e.g.) streaming buffers down from a network source, you won't be able to avoid copying. (It's not that expensively, actually.) If you're generating the audio buffer, you should generate it in the onaudioprocess.