have you seen this? I am not an expert in ffts so maybe it could be improved but it is impressively fast in my experience (also very readable) : https://github.com/corbanbrook/dsp.js/blob/master/dsp.js
42 karma · joined June 17, 2014
Differential Steering: https://www.youtube.com/watch?v=yYAw79386WI
Turbo Encabulator: https://www.youtube.com/watch?v=rLDgQg6bq7o
GL does have the capability to handle linear color space buffers correctly, but you have to enable SRGB, and initialize the framebuffer correctly with SRGB color space, and I'm not sure if GLES (WebGL) can do this.
More info : http://http.developer.nvidia.com/GPUGems3/gpugems3_ch24.html