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User:David.humphrey/Audio Data API 2: Difference between revisions
→Complete Example: Visualizing Audio Spectrum
| Line 109: | Line 109: | ||
var canvas = document.getElementById('fft'), | var canvas = document.getElementById('fft'), | ||
ctx = canvas.getContext('2d'), | ctx = canvas.getContext('2d'), | ||
fft; | fft; | ||
function loadedMetadata(event) { | function loadedMetadata(event) { | ||
channels = event.mozChannels | var channels = event.mozChannels, | ||
rate = event.mozRate, | |||
fft = new FFT( | frameBufferLength = event.mozFrameBufferLength; | ||
fft = new FFT(frameBufferLength / channels, rate), | |||
} | } | ||
| Line 126: | Line 125: | ||
for (var i = 0, fbl = fb.length / 2; i < fbl; i++ ) { | for (var i = 0, fbl = fb.length / 2; i < fbl; i++ ) { | ||
// Assuming interlaced stereo channels, need to split and merge into a stero-mix mono signal | // Assuming interlaced stereo channels, | ||
// need to split and merge into a stero-mix mono signal | |||
signal[i] = (fb[2*i] + fb[2*i+1]) / 2; | signal[i] = (fb[2*i] + fb[2*i+1]) / 2; | ||
} | } | ||
| Line 136: | Line 136: | ||
for (var i = 0; i < fft.spectrum.length; i++ ) { | for (var i = 0; i < fft.spectrum.length; i++ ) { | ||
magnitude = fft.spectrum[i] * 4000; | // multiply spectrum by a zoom value | ||
magnitude = fft.spectrum[i] * 4000; | |||
// Draw rectangle bars for each frequency bin | // Draw rectangle bars for each frequency bin | ||