added streaming resampler

resampler.hh

@@ -49,5 +49,54 @@ public:
 	}
 };
 
+template <typename TYPE, typename IO, int TAPS, int OVER>
+class Resampler2
+{
+	typedef DSP::UniformNaturalCubicSpline<TAPS * OVER, TYPE, TYPE> spline_type;
+	spline_type lpf;
+	TYPE rate;
+	TYPE dpos;
+	IO buf[TAPS];
+public:
+	Resampler2(TYPE rate, TYPE cutoff, TYPE alpha) : rate(rate), dpos(0)
+	{
+		TYPE tmp[TAPS * OVER];
+		DSP::Kaiser<TYPE> window(alpha);
+		for (int n = 0; n < TAPS * OVER; ++n) {
+			TYPE x = TYPE(n) / TYPE(OVER) - TYPE(TAPS - 1) / TYPE(2);
+			TYPE y = TYPE(2) * cutoff / rate * sinc(TYPE(2) * cutoff / rate * x);
+			tmp[n] = y * window(n, TAPS * OVER);
+		}
+		lpf = spline_type(tmp, 0, 1.0 / OVER);
+		for (int i = 0; i < TAPS; ++i)
+			buf[i] = 0;
+	}
+	int operator ()(IO *output, IO input, TYPE diff)
+	{
+		for (int i = 0; i < TAPS-1; ++i)
+			buf[i] = buf[i+1];
+		buf[TAPS-1] = input;
+		if (dpos < TYPE(-0.5)) {
+			dpos += TYPE(1);
+			return 0;
+		}
+		TYPE delta = diff / rate;
+		int samples = 0;
+		again:
+		IO sum = 0;
+		for (int s = 0; s < TAPS; ++s) {
+			TYPE k = s + dpos;
+			sum += lpf(k) * buf[s];
+		}
+		output[samples++] = sum;
+		dpos += delta;
+		if (dpos > TYPE(0.5)) {
+			dpos -= TYPE(1);
+			goto again;
+		}
+		return samples;
+	}
+};
+
 }