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optimizing filters, work in progress

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This commit is contained in:
Andy Sloane 2015-10-25 09:00:21 -07:00
commit f8a278f456
1 changed files with 15 additions and 18 deletions
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33
xm.js
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@ -74,6 +74,8 @@ function FilterCoeffs(f_c) {
return [gain, 2*c, -c*c - s*s];
}
popfilter = FilterCoeffs(200.0 / 44100.0);
function Filter(x, coef, state) {
var y = coef[0] * (x + state[0]) + coef[1]*state[1] + coef[2]*state[2];
state[0] = x;
@ -290,20 +292,12 @@ function audio_cb(e) {
var dk = ch.doff;
// console.log(j, offset, ch);
for (var i = offset; i < offset+tickduration; i++) {
var kk = k|0;
var si = samp[kk];
/*
// bilinear filtering
var sj = si;
if (kk < sample_end-1)
sj = samp[kk+1];
var t = k - kk;
si = t * sj + (1 - t) * si;
*/
vl = Filter(volL, ch.popfilter, ch.popfilterstate[0]);
vr = Filter(volR, ch.popfilter, ch.popfilterstate[1]);
dataL[i] += Filter(vl * si, ch.filter, ch.filterstate[0]);
dataR[i] += Filter(vr * si, ch.filter, ch.filterstate[1]);
var si = samp[k|0];
si = Filter(si, ch.filter, ch.filterstate);
var vl = Filter(volL, popfilter, ch.popfilterstate[0]);
var vr = Filter(volR, popfilter, ch.popfilterstate[1]);
dataL[i] += vl * si;
dataR[i] += vr * si;
k += dk;
if (k >= sample_end) { // TODO: implement pingpong looping
if (loop) {
@ -311,10 +305,13 @@ function audio_cb(e) {
} else {
// kill sample
ch.inst = undefined;
for (i++; i < offset+tickduration; i++) {
// ramp down with the pop filter
var rampend = Math.min(offset+tickduration, i+200);
for (i++; i < rampend; i++) {
// fill rest of buffer with filtered silence to avoid a pop
dataL[i] += Filter(0, ch.popfilter, ch.filterstate[0]);
dataR[i] += Filter(0, ch.popfilter, ch.filterstate[1]);
var s = Filter(0, popfilter, ch.filterstate);
dataL[i] += vl * s;
dataR[i] += vr * s;
}
break;
}
@ -370,7 +367,7 @@ function playXM(arrayBuf) {
bpm = dv.getUint16(0x4e, true);
for (var i = 0; i < nchan; i++) {
channelinfo.push({
filterstate: [new Float32Array(3), new Float32Array(3)],
filterstate: new Float32Array(3),
popfilter: FilterCoeffs(200.0 / 44100.0),
popfilterstate: [new Float32Array(3), new Float32Array(3)],
vol: 0,