Thanks. I picked a fixed number of horizontal pixels per second for an internally cached image. I think it was 30 pixels/second so that scrolling at 1x playback

Thanks. I picked a fixed number of horizontal pixels per second for an internally cached image. I think it was 30 pixels/second so that scrolling at 1x playback rate would be smooth on 60/90/120Hz screens. So it can't zoom into the waveform like yours, but I don't need it to zoom. There are two parts: first the C++/wasm that analyses the audio and generates a bitmap that has width 30*duration and not very high. It effectively draws a line from each audio sample to the next, with alpha, but this can be optimised like crazy to a point where the time it takes is unnoticeable. The second part is the WebGL that the bitmap (aka texture) and renders to the canvas. In principle this could be rotated, spun in 3d, mapped to a sphere or any other crazy GPU manipulations. WebGL isn't too painful and works everywhere I tried including the Android webview in my Bungee Timewarp app.