Tim Goetze wrote on Tue, 23-Mar-2004:
> pleased to announce the new DSP package 'pvoc'. at its core, it
> features the CARL phase vocoder.
>
> there are three LADSPA units in this package (Exaggerate, Transpose,
> Accumulate) plus a commandline utility for time compression and
> expansion of n-channel audio data streams.
>
> compilation of this package will probably be an even rougher ride than
> with the initial release of caps (pvoc depends on FFTW3 and sndfile)
> but i'll be happy to help should you run into problems.
The stretch program was not properly clamping the output from
-1.0 -> 1.0 yielding to terrible cracks upon writing as 16bit
wave files when the output is clipped. The fact that non-clipping
(but very close to) input yielded clipping output is another issue,
but not crucial.
I've attached a patch that fixes the problem.
Other than that, this sounds pretty darn good compared to soundtouch
(a time domain algorithm) at more extreme stretch factors.
jlc
--- pvoc-0.1.4/stretch.cc 2004-03-24 12:14:35.000000000 -0500
+++ pvoc-0.1.4.new/stretch.cc 2004-03-24 14:46:22.000000000 -0500
@@ -453,7 +453,7 @@
f = interleaved + i;
for (int j = 0; j < decfac.out; ++j, f += channels)
- *f = buffer[j];
+ *f = f_clamp (buffer[j], -1.0f, 1.0f);
}
if (write)
--- pvoc-0.1.4/basics.h 2004-03-24 12:12:00.000000000 -0500
+++ pvoc-0.1.4.new/basics.h 2004-03-24 14:52:58.000000000 -0500
@@ -133,4 +133,18 @@
return (float) random() / (float) RAND_MAX;
}
+static inline float f_clamp(float x, float a, float b)
+{
+ const float x1 = fabs(x - a);
+ const float x2 = fabs(x - b);
+
+ x = x1 + a + b;
+ x -= x2;
+ x *= 0.5;
+
+ return x;
+}
+
+
+
#endif /* _BASICS_H_ */
