Sure, you could pre-calculate your filter coefficients and use a bandpass for each frequency band then do the math in Javascript however it's slower, and more involved. Also, unless you're going to be using WAVs, there's going to be some overhead for the decoding of the sound. Also, the filter won't be very high order since you're going to be doing at least n*44100 operations per second (at the standard sampling rate). (Web Audio API filter nodes are only 2nd order but you can cascade them.) Do you have examples of the above working in Firefox? I'd be curious to see the implementation.
It's slower, but... does it matter if it's not just "slow"? Slower than "so fast" is still "fast".
> and more involved
That's right.
> Also, unless you're going to be using WAVs, there's going to be some overhead for the decoding of the sound.
If I recall correctly, Firefox's Audio Data API does the decoding for you and provides the final PCM samples even when loading non-WAV formats.
> Also, the filter won't be very high order since you're going to be doing at least n 44100 operations per second
If the effect computation is a problem, you can pre-render it in a buffer.
Anyways, n*44100 operations per second is not that much. You actually operate on buffers, which makes caching useful for the slow part (memory access). Summing, multiplying, etc. is a piece of cake for your CPU in JIT-compiled code.
Check this JSFiddle I threw in a couple minutes: http://jsfiddle.net/9LpKd/2/ (please mind the awful effect and the fact that it's not audio... I'm not very experienced with Audio Data API and that would take me a bit more to fiddle with!)
44000 pixel updates, up to 60 times a second, with pretty expensive operations (sines, cosines and even square roots!), updating DOM values... JavaScript is fast enough for this.
I can see the problem in mobile devices though, but I'm not even sure Firefox provides Audio Data API in mobile devices.
>Do you have examples of the above working in Firefox? I'd be curious to see the implementation.
The only web implementing it that I can remember is http://websdr.ewi.utwente.nl:8901/ (you have to check the HTML5 audio radio button).
Unfortunately the code is minified and it takes a bit to make sense of it after Beautifying.
