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Changes by Sjoerd (reformatted). 

add(): better handling of overflow (substitute maxval instead of
throwing away higher order bits).

ratecv(): some bugfixes, Sjoerd says.
This commit is contained in:
Guido van Rossum 1997-02-14 16:14:03 +00:00
parent 6fb6f10a96
commit 1851a67695
1 changed files with 106 additions and 95 deletions
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59
Modules/audioop.c
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@ -781,7 +781,7 @@ audioop_add(self, args)
PyObject *args;
{
signed char *cp1, *cp2, *ncp;
int len1, len2, size, val1 = 0, val2 = 0;
int len1, len2, size, val1 = 0, val2 = 0, maxval, newval;
PyObject *rv;
int i;
@ -794,7 +794,10 @@ audioop_add(self, args)
return 0;
}
if ( size != 1 && size != 2 && size != 4) {
if ( size == 1 ) maxval = 0x7f;
else if ( size == 2 ) maxval = 0x7fff;
else if ( size == 4 ) maxval = 0x7fffffff;
else {
PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
return 0;
}
@ -804,7 +807,6 @@ audioop_add(self, args)
return 0;
ncp = (signed char *)PyString_AsString(rv);
for ( i=0; i < len1; i += size ) {
if ( size == 1 ) val1 = (int)*CHARP(cp1, i);
else if ( size == 2 ) val1 = (int)*SHORTP(cp1, i);
@ -814,9 +816,16 @@ audioop_add(self, args)
else if ( size == 2 ) val2 = (int)*SHORTP(cp2, i);
else if ( size == 4 ) val2 = (int)*LONGP(cp2, i);
if ( size == 1 ) *CHARP(ncp, i) = (signed char)(val1+val2);
else if ( size == 2 ) *SHORTP(ncp, i) = (short)(val1+val2);
else if ( size == 4 ) *LONGP(ncp, i) = (long)(val1+val2);
newval = val1 + val2;
/* truncate in case of overflow */
if (newval > maxval) newval = maxval;
else if (newval < -maxval) newval = -maxval;
else if (size == 4 && (newval^val1) < 0 && (newval^val2) < 0)
newval = val1 > 0 ? maxval : - maxval;
if ( size == 1 ) *CHARP(ncp, i) = (signed char)newval;
else if ( size == 2 ) *SHORTP(ncp, i) = (short)newval;
else if ( size == 4 ) *LONGP(ncp, i) = (long)newval;
}
return rv;
}
@ -941,11 +950,11 @@ audioop_ratecv(self, args)
PyObject *self;
PyObject *args;
{
signed char *cp;
unsigned char *ncp;
char *cp, *ncp;
int len, size, nchannels, inrate, outrate, weightA, weightB;
int chan, d, *prev_i, *cur_i, cur_o;
PyObject *state, *samps, *str, *rv;
weightA = 1;
weightB = 0;
if (!PyArg_ParseTuple(args, "s#iiiiO|ii", &cp, &len, &size, &nchannels,
@ -964,9 +973,13 @@ audioop_ratecv(self, args)
"weightA should be >= 1, weightB should be >= 0");
return NULL;
}
if (len % (size * nchannels) != 0) {
PyErr_SetString(AudioopError, "not a whole number of frames");
return NULL;
}
prev_i = malloc(nchannels * sizeof(int));
cur_i = malloc(nchannels * sizeof(int));
len = len / size; /* # of frames */
len /= size * nchannels; /* # of frames */
if (state == Py_None) {
d = -outrate;
@ -988,8 +1001,8 @@ audioop_ratecv(self, args)
return NULL;
}
}
str = PyString_FromStringAndSize(NULL,
size * (len * outrate + inrate - 1) / inrate);
str = PyString_FromStringAndSize(
NULL, size * nchannels * (len * outrate + inrate - 1) / inrate);
if (str == NULL)
return NULL;
ncp = PyString_AsString(str);
@ -1006,8 +1019,7 @@ audioop_ratecv(self, args)
if (PyErr_Occurred())
return NULL;
if (_PyString_Resize(&str,
ncp - (unsigned char *)
PyString_AsString(str)) < 0)
ncp - PyString_AsString(str)) < 0)
return NULL;
rv = Py_BuildValue("(O(iO))", str, d, samps);
Py_DECREF(samps);
@ -1017,29 +1029,28 @@ audioop_ratecv(self, args)
for (chan = 0; chan < nchannels; chan++) {
prev_i[chan] = cur_i[chan];
if (size == 1)
cur_i[chan] =
((int)*CHARP(cp, 0)) << 8;
cur_i[chan] = ((int)*CHARP(cp, 0)) << 8;
else if (size == 2)
cur_i[chan] = (int)*SHORTP(cp, 0);
else if (size == 4)
cur_i[chan] =
((int)*LONGP(cp, 0)) >> 16;
cur_i[chan] = ((int)*LONGP(cp, 0)) >> 16;
cp += size;
/* implements a simple digital filter */
cur_i[chan] = (weightA * cur_i[chan] +
weightB * prev_i[chan])
/ (weightA + weightB);
cur_i[chan] =
(weightA * cur_i[chan] +
weightB * prev_i[chan]) /
(weightA + weightB);
}
len--;
d += outrate;
}
while (d >= 0) {
for (chan = 0; chan < nchannels; chan++) {
cur_o = (prev_i[chan] * d + cur_i[chan]
* (outrate - d)) / outrate;
cur_o = (prev_i[chan] * d +
cur_i[chan] * (outrate - d)) /
outrate;
if (size == 1)
*CHARP(ncp, 0) =
(signed char)(cur_o >> 8);
*CHARP(ncp, 0) = (signed char)(cur_o >> 8);
else if (size == 2)
*SHORTP(ncp, 0) = (short)(cur_o);
else if (size == 4)