refactored mixing code a bit
removed all doubt about handling note-end pops
This commit is contained in:
Andy Sloane
parent
343da0f3e9
commit
c2fe03797e
1 changed files with 87 additions and 80 deletions
167
xm.js
167
xm.js
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@ -261,6 +261,90 @@ function next_tick() {
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}
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}
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}
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}
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// This function gradually brings the channel back down to zero if it isn't
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// already to avoid clicks and pops when samples end.
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function MixSilenceIntoBuf(ch, start, end, dataL, dataR) {
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var s = ch.filterstate[1];
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for (var i = start; i < end; i++) {
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if (Math.abs(s) < 1.526e-5) // == 1/65536.0
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break;
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dataL[i] += s * ch.vL;
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dataR[i] += s * ch.vR;
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s *= popfilter_alpha;
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}
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ch.filterstate[1] = s;
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ch.filterstate[2] = s;
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return 0;
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}
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function MixChannelIntoBuf(ch, start, end, dataL, dataR) {
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var inst = ch.inst;
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var samp, sample_end;
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var loop = false;
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var looplen = 0;
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// nothing on this channel, just filter the last dc offset back down to zero
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if (inst === undefined || ch.mute) {
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return MixSilenceIntoBuf(ch, start, end, dataL, dataR);
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}
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samp = inst.sampledata;
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sample_end = inst.len;
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if ((inst.type & 3) == 1) { // todo: support pingpong
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loop = true;
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looplen = inst.looplen;
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sample_end = looplen + inst.loop;
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}
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var samplen = inst.len;
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var volE = ch.volE / 64.0;
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var panE = (ch.panE - 32);
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var p = panE + ch.pan - 128;
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var volL = volE * (128 - p) * ch.vol / 8192.0;
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var volR = volE * (128 + p) * ch.vol / 8192.0;
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if (volL < 0) volL = 0;
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if (volR < 0) volR = 0;
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if (volR == 0 && volL == 0)
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return;
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var k = ch.off;
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var dk = ch.doff;
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var Vrms = 0;
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for (var i = start; i < end; i++) {
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var s = samp[k|0];
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// we low-pass filter here since we are resampling some arbitrary
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// frequency to f_smp; this is an anti-aliasing filter and is
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// implemented as an IIR butterworth filter (usually we'd use an FIR
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// brick wall filter, but this is much simpler computationally and
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// sounds fine)
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var si = ch.filter[0] * (s + ch.filterstate[0]) +
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ch.filter[1]*ch.filterstate[1] + ch.filter[2]*ch.filterstate[2];
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ch.filterstate[2] = ch.filterstate[1];
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ch.filterstate[1] = si; ch.filterstate[0] = s;
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// we also low-pass filter volume changes with a simple one-zero,
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// one-pole filter to avoid pops and clicks when volume changes.
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ch.vL = popfilter_alpha * ch.vL + (1 - popfilter_alpha) * (volL + ch.vLprev) * 0.5;
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ch.vR = popfilter_alpha * ch.vR + (1 - popfilter_alpha) * (volR + ch.vRprev) * 0.5;
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ch.vLprev = volL;
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ch.vRprev = volR;
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dataL[i] += ch.vL * si;
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dataR[i] += ch.vR * si;
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Vrms += ch.vL * ch.vR * si * si;
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k += dk;
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if (k >= sample_end) { // TODO: implement pingpong looping
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if (loop) {
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k -= looplen;
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} else {
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// kill sample
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ch.inst = undefined;
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// fill rest of buf with filtered dc offset using loop above
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return Vrms + MixSilenceIntoBuf(ch, i+1, end, dataL, dataR);
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}
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}
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}
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ch.off = k;
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ch.doff = dk;
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return Vrms;
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}
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function audio_cb(e) {
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function audio_cb(e) {
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f_smp = audioctx.sampleRate;
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f_smp = audioctx.sampleRate;
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var buflen = e.outputBuffer.length;
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var buflen = e.outputBuffer.length;
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@ -289,86 +373,8 @@ function audio_cb(e) {
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}
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}
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var tickduration = Math.min(buflen, ticklen - cur_ticksamp);
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var tickduration = Math.min(buflen, ticklen - cur_ticksamp);
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for (var j = 0; j < nchan; j++) {
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for (var j = 0; j < nchan; j++) {
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var ch = channelinfo[j];
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VU[j] += MixChannelIntoBuf(
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var inst = ch.inst;
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channelinfo[j], offset, offset + tickduration, dataL, dataR);
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var samp, sample_end;
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var loop = false;
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var looplen = 0;
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if (inst === undefined) {
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continue;
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}
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samp = inst.sampledata;
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sample_end = inst.len;
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if ((inst.type & 3) == 1) { // todo: support pingpong
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loop = true;
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looplen = inst.looplen;
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sample_end = looplen + inst.loop;
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}
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var samplen = inst.len;
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var volE = ch.volE / 64.0;
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var panE = (ch.panE - 32);
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var p = panE + ch.pan - 128;
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var volL = volE * (128 - p) * ch.vol / 8192.0;
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var volR = volE * (128 + p) * ch.vol / 8192.0;
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if (volL < 0) volL = 0;
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if (volR < 0) volR = 0;
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if (volR == 0 && volL == 0)
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continue;
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var k = ch.off;
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var dk = ch.doff;
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var Vrms = 0;
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// console.log(j, offset, ch);
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for (var i = offset; i < offset+tickduration; i++) {
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if (ch.mute) break;
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var s = samp[k|0];
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// we low-pass filter here since we are resampling some arbitrary
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// frequency to f_smp; this is an anti-aliasing filter and is
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// implemented as an IIR butterworth filter (usually we'd use an FIR
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// brick wall filter, but this is much simpler computationally and
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// sounds fine)
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var si = ch.filter[0] * (s + ch.filterstate[0]) +
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ch.filter[1]*ch.filterstate[1] + ch.filter[2]*ch.filterstate[2];
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ch.filterstate[2] = ch.filterstate[1];
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ch.filterstate[1] = si; ch.filterstate[0] = s;
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// we also low-pass filter volume changes with a simple one-zero,
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// one-pole filter to avoid pops and clicks when volume changes.
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ch.vL = popfilter_alpha * ch.vL + (1 - popfilter_alpha) * (volL + ch.vLprev) * 0.5;
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ch.vR = popfilter_alpha * ch.vR + (1 - popfilter_alpha) * (volR + ch.vRprev) * 0.5;
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ch.vLprev = volL;
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ch.vRprev = volR;
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dataL[i] += ch.vL * si;
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dataR[i] += ch.vR * si;
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Vrms += ch.vL * ch.vR * si * si;
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k += dk;
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if (k >= sample_end) { // TODO: implement pingpong looping
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if (loop) {
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k -= looplen;
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} else {
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// kill sample
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ch.inst = undefined;
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// ramp down to zero with the pop filter
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// if the sample ends right before the end of the tick (or the end
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// of the buffer), we could still get a pop but *usually* it's
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// hidden behind other changes in the tick... there's only so much
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// we can do here, anyway. i guess we could hold the dc offset...
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var rampend = Math.min(offset+tickduration, i+200);
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for (i++; i < rampend; i++) {
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// fill rest of buffer with filtered silence to avoid a pop
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var si = popfilter[0] * (ch.filterstate[0]) +
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popfilter[1]*ch.filterstate[1] +
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popfilter[2]*ch.filterstate[2];
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ch.filterstate[2] = ch.filterstate[1];
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ch.filterstate[1] = si; ch.filterstate[0] = 0;
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dataL[i] += ch.vL * si;
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dataR[i] += ch.vR * si;
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}
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break;
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}
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}
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}
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ch.off = k;
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ch.doff = dk;
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VU[j] += Vrms;
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}
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}
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offset += tickduration;
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offset += tickduration;
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cur_ticksamp += tickduration;
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cur_ticksamp += tickduration;
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@ -568,6 +574,7 @@ function playXM(arrayBuf) {
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vL: 0, vR: 0, // left right volume envelope followers (changes per sample)
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vL: 0, vR: 0, // left right volume envelope followers (changes per sample)
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vLprev: 0, vRprev: 0,
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vLprev: 0, vRprev: 0,
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mute: 0,
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mute: 0,
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volE: 0, panE: 0
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})
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})
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}
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}
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console.log("header len " + hlen);
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console.log("header len " + hlen);
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