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python3.2  3.2.2
Defines | Typedefs | Functions | Variables
audioop.c File Reference
#include "Python.h"

Go to the source code of this file.

Defines

#define PY_SSIZE_T_CLEAN
#define BIAS   0x84 /* define the add-in bias for 16 bit samples */
#define CLIP   32635
#define SIGN_BIT   (0x80) /* Sign bit for a A-law byte. */
#define QUANT_MASK   (0xf) /* Quantization field mask. */
#define SEG_SHIFT   (4) /* Left shift for segment number. */
#define SEG_MASK   (0x70) /* Segment field mask. */
#define st_ulaw2linear16(uc)   (_st_ulaw2linear16[uc])
#define st_alaw2linear16(uc)   (_st_alaw2linear16[uc])
#define CHARP(cp, i)   ((signed char *)(cp+i))
#define SHORTP(cp, i)   ((short *)(cp+i))
#define LONGP(cp, i)   ((Py_Int32 *)(cp+i))

Typedefs

typedef short PyInt16

Functions

static PyInt16 search (PyInt16 val, PyInt16 *table, int size)
static unsigned char st_14linear2ulaw (PyInt16 pcm_val)
static unsigned char st_linear2alaw (PyInt16 pcm_val)
static int audioop_check_size (int size)
static int audioop_check_parameters (Py_ssize_t len, int size)
static PyObjectaudioop_getsample (PyObject *self, PyObject *args)
static PyObjectaudioop_max (PyObject *self, PyObject *args)
static PyObjectaudioop_minmax (PyObject *self, PyObject *args)
static PyObjectaudioop_avg (PyObject *self, PyObject *args)
static PyObjectaudioop_rms (PyObject *self, PyObject *args)
static double _sum2 (short *a, short *b, Py_ssize_t len)
static PyObjectaudioop_findfit (PyObject *self, PyObject *args)
static PyObjectaudioop_findfactor (PyObject *self, PyObject *args)
static PyObjectaudioop_findmax (PyObject *self, PyObject *args)
static PyObjectaudioop_avgpp (PyObject *self, PyObject *args)
static PyObjectaudioop_maxpp (PyObject *self, PyObject *args)
static PyObjectaudioop_cross (PyObject *self, PyObject *args)
static PyObjectaudioop_mul (PyObject *self, PyObject *args)
static PyObjectaudioop_tomono (PyObject *self, PyObject *args)
static PyObjectaudioop_tostereo (PyObject *self, PyObject *args)
static PyObjectaudioop_add (PyObject *self, PyObject *args)
static PyObjectaudioop_bias (PyObject *self, PyObject *args)
static PyObjectaudioop_reverse (PyObject *self, PyObject *args)
static PyObjectaudioop_lin2lin (PyObject *self, PyObject *args)
static int gcd (int a, int b)
static PyObjectaudioop_ratecv (PyObject *self, PyObject *args)
static PyObjectaudioop_lin2ulaw (PyObject *self, PyObject *args)
static PyObjectaudioop_ulaw2lin (PyObject *self, PyObject *args)
static PyObjectaudioop_lin2alaw (PyObject *self, PyObject *args)
static PyObjectaudioop_alaw2lin (PyObject *self, PyObject *args)
static PyObjectaudioop_lin2adpcm (PyObject *self, PyObject *args)
static PyObjectaudioop_adpcm2lin (PyObject *self, PyObject *args)
PyMODINIT_FUNC PyInit_audioop (void)

Variables

static PyInt16 seg_aend [8]
static PyInt16 seg_uend [8]
static PyInt16 _st_ulaw2linear16 [256]
static PyInt16 _st_alaw2linear16 [256]
static int indexTable [16]
static int stepsizeTable [89]
static PyObjectAudioopError
static PyMethodDef audioop_methods []
static struct PyModuleDef

Define Documentation

#define BIAS   0x84 /* define the add-in bias for 16 bit samples */

Definition at line 43 of file audioop.c.

#define CHARP (   cp,
  i 
)    ((signed char *)(cp+i))

Definition at line 292 of file audioop.c.

#define CLIP   32635

Definition at line 44 of file audioop.c.

#define LONGP (   cp,
  i 
)    ((Py_Int32 *)(cp+i))

Definition at line 294 of file audioop.c.

Definition at line 4 of file audioop.c.

#define QUANT_MASK   (0xf) /* Quantization field mask. */

Definition at line 46 of file audioop.c.

#define SEG_MASK   (0x70) /* Segment field mask. */

Definition at line 48 of file audioop.c.

#define SEG_SHIFT   (4) /* Left shift for segment number. */

Definition at line 47 of file audioop.c.

#define SHORTP (   cp,
  i 
)    ((short *)(cp+i))

Definition at line 293 of file audioop.c.

#define SIGN_BIT   (0x80) /* Sign bit for a A-law byte. */

Definition at line 45 of file audioop.c.

#define st_alaw2linear16 (   uc)    (_st_alaw2linear16[uc])

Definition at line 67 of file audioop.c.

#define st_ulaw2linear16 (   uc)    (_st_ulaw2linear16[uc])

Definition at line 66 of file audioop.c.


Typedef Documentation

typedef short PyInt16

Definition at line 20 of file audioop.c.


Function Documentation

static double _sum2 ( short *  a,
short *  b,
Py_ssize_t  len 
) [static]

Definition at line 438 of file audioop.c.

{
    Py_ssize_t i;
    double sum = 0.0;

    for( i=0; i<len; i++) {
        sum = sum + (double)a[i]*(double)b[i];
    }
    return sum;
}

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static PyObject* audioop_add ( PyObject self,
PyObject args 
) [static]

Definition at line 918 of file audioop.c.

{
    signed char *cp1, *cp2, *ncp;
    Py_ssize_t len1, len2, i;
    int size, val1 = 0, val2 = 0, maxval, newval;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#s#i:add",
                      &cp1, &len1, &cp2, &len2, &size ) )
        return 0;
    if (!audioop_check_parameters(len1, size))
        return NULL;
    if ( len1 != len2 ) {
        PyErr_SetString(AudioopError, "Lengths should be the same");
        return 0;
    }

    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;
    }

    rv = PyBytes_FromStringAndSize(NULL, len1);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_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);
        else if ( size == 4 ) val1 = (int)*LONGP(cp1, i);

        if ( size == 1 )      val2 = (int)*CHARP(cp2, i);
        else if ( size == 2 ) val2 = (int)*SHORTP(cp2, i);
        else if ( size == 4 ) val2 = (int)*LONGP(cp2, i);

        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) = (Py_Int32)newval;
    }
    return rv;
}

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static PyObject* audioop_adpcm2lin ( PyObject self,
PyObject args 
) [static]

Definition at line 1517 of file audioop.c.

{
    signed char *cp;
    signed char *ncp;
    Py_ssize_t len, i;
    int size, valpred, step, delta, index, sign, vpdiff;
    PyObject *rv, *str, *state;
    int inputbuffer = 0, bufferstep;

    if ( !PyArg_ParseTuple(args, "s#iO:adpcm2lin",
                           &cp, &len, &size, &state) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    /* Decode state, should have (value, step) */
    if ( state == Py_None ) {
        /* First time, it seems. Set defaults */
        valpred = 0;
        step = 7;
        index = 0;
    } else if ( !PyArg_ParseTuple(state, "ii", &valpred, &index) )
        return 0;

    if (len > (PY_SSIZE_T_MAX/2)/size) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }
    str = PyBytes_FromStringAndSize(NULL, len*size*2);
    if ( str == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(str);

    step = stepsizeTable[index];
    bufferstep = 0;

    for ( i=0; i < len*size*2; i += size ) {
        /* Step 1 - get the delta value and compute next index */
        if ( bufferstep ) {
            delta = inputbuffer & 0xf;
        } else {
            inputbuffer = *cp++;
            delta = (inputbuffer >> 4) & 0xf;
        }

        bufferstep = !bufferstep;

        /* Step 2 - Find new index value (for later) */
        index += indexTable[delta];
        if ( index < 0 ) index = 0;
        if ( index > 88 ) index = 88;

        /* Step 3 - Separate sign and magnitude */
        sign = delta & 8;
        delta = delta & 7;

        /* Step 4 - Compute difference and new predicted value */
        /*
        ** Computes 'vpdiff = (delta+0.5)*step/4', but see comment
        ** in adpcm_coder.
        */
        vpdiff = step >> 3;
        if ( delta & 4 ) vpdiff += step;
        if ( delta & 2 ) vpdiff += step>>1;
        if ( delta & 1 ) vpdiff += step>>2;

        if ( sign )
            valpred -= vpdiff;
        else
            valpred += vpdiff;

        /* Step 5 - clamp output value */
        if ( valpred > 32767 )
            valpred = 32767;
        else if ( valpred < -32768 )
            valpred = -32768;

        /* Step 6 - Update step value */
        step = stepsizeTable[index];

        /* Step 6 - Output value */
        if ( size == 1 ) *CHARP(ncp, i) = (signed char)(valpred >> 8);
        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(valpred);
        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(valpred<<16);
    }

    rv = Py_BuildValue("(O(ii))", str, valpred, index);
    Py_DECREF(str);
    return rv;
}

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static PyObject* audioop_alaw2lin ( PyObject self,
PyObject args 
) [static]

Definition at line 1372 of file audioop.c.

{
    unsigned char *cp;
    unsigned char cval;
    signed char *ncp;
    Py_ssize_t len, i;
    int size, val;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#i:alaw2lin",
                           &cp, &len, &size) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    if (len > PY_SSIZE_T_MAX/size) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }
    rv = PyBytes_FromStringAndSize(NULL, len*size);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(rv);

    for ( i=0; i < len*size; i += size ) {
        cval = *cp++;
        val = st_alaw2linear16(cval);

        if ( size == 1 )      *CHARP(ncp, i) = (signed char)(val >> 8);
        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(val);
        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(val<<16);
    }
    return rv;
}

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static PyObject* audioop_avg ( PyObject self,
PyObject args 
) [static]

Definition at line 389 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;
    double avg = 0.0;

    if ( !PyArg_ParseTuple(args, "s#i:avg", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    for ( i=0; i<len; i+= size) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        avg += val;
    }
    if ( len == 0 )
        val = 0;
    else
        val = (int)(avg / (double)(len/size));
    return PyLong_FromLong(val);
}

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static PyObject* audioop_avgpp ( PyObject self,
PyObject args 
) [static]

Definition at line 621 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0, prevval = 0, prevextremevalid = 0,
        prevextreme = 0;
    double avg = 0.0;
    int diff, prevdiff, extremediff, nextreme = 0;

    if ( !PyArg_ParseTuple(args, "s#i:avgpp", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    /* Compute first delta value ahead. Also automatically makes us
    ** skip the first extreme value
    */
    if ( size == 1 )      prevval = (int)*CHARP(cp, 0);
    else if ( size == 2 ) prevval = (int)*SHORTP(cp, 0);
    else if ( size == 4 ) prevval = (int)*LONGP(cp, 0);
    if ( size == 1 )      val = (int)*CHARP(cp, size);
    else if ( size == 2 ) val = (int)*SHORTP(cp, size);
    else if ( size == 4 ) val = (int)*LONGP(cp, size);
    prevdiff = val - prevval;

    for ( i=size; i<len; i+= size) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        diff = val - prevval;
        if ( diff*prevdiff < 0 ) {
            /* Derivative changed sign. Compute difference to last
            ** extreme value and remember.
            */
            if ( prevextremevalid ) {
                extremediff = prevval - prevextreme;
                if ( extremediff < 0 )
                    extremediff = -extremediff;
                avg += extremediff;
                nextreme++;
            }
            prevextremevalid = 1;
            prevextreme = prevval;
        }
        prevval = val;
        if ( diff != 0 )
            prevdiff = diff;
    }
    if ( nextreme == 0 )
        val = 0;
    else
        val = (int)(avg / (double)nextreme);
    return PyLong_FromLong(val);
}

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static PyObject* audioop_bias ( PyObject self,
PyObject args 
) [static]

Definition at line 972 of file audioop.c.

{
    signed char *cp, *ncp;
    Py_ssize_t len, i;
    int size, val = 0;
    PyObject *rv;
    int bias;

    if ( !PyArg_ParseTuple(args, "s#ii:bias",
                      &cp, &len, &size , &bias) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, len);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(rv);


    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);

        if ( size == 1 )      *CHARP(ncp, i) = (signed char)(val+bias);
        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(val+bias);
        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(val+bias);
    }
    return rv;
}

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static int audioop_check_parameters ( Py_ssize_t  len,
int  size 
) [static]

Definition at line 312 of file audioop.c.

{
    if (!audioop_check_size(size))
        return 0;
    if (len % size != 0) {
        PyErr_SetString(AudioopError, "not a whole number of frames");
        return 0;
    }
    return 1;
}

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static int audioop_check_size ( int  size) [static]

Definition at line 301 of file audioop.c.

{
    if (size != 1 && size != 2 && size != 4) {
        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
        return 0;
    }
    else
        return 1;
}

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static PyObject* audioop_cross ( PyObject self,
PyObject args 
) [static]

Definition at line 727 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;
    int prevval;
    Py_ssize_t ncross;

    if ( !PyArg_ParseTuple(args, "s#i:cross", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    ncross = -1;
    prevval = 17; /* Anything <> 0,1 */
    for ( i=0; i<len; i+= size) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) >> 7;
        else if ( size == 2 ) val = ((int)*SHORTP(cp, i)) >> 15;
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 31;
        val = val & 1;
        if ( val != prevval ) ncross++;
        prevval = val;
    }
    return PyLong_FromSsize_t(ncross);
}

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static PyObject* audioop_findfactor ( PyObject self,
PyObject args 
) [static]

Definition at line 545 of file audioop.c.

{
    short *cp1, *cp2;
    Py_ssize_t len1, len2;
    double sum_ri_2, sum_aij_ri, result;

    if ( !PyArg_ParseTuple(args, "s#s#:findfactor",
                           (char**)&cp1, &len1, (char**)&cp2, &len2) )
        return 0;
    if ( len1 & 1 || len2 & 1 ) {
        PyErr_SetString(AudioopError, "Strings should be even-sized");
        return 0;
    }
    if ( len1 != len2 ) {
        PyErr_SetString(AudioopError, "Samples should be same size");
        return 0;
    }
    len2 >>= 1;
    sum_ri_2 = _sum2(cp2, cp2, len2);
    sum_aij_ri = _sum2(cp1, cp2, len2);

    result = sum_aij_ri / sum_ri_2;

    return PyFloat_FromDouble(result);
}

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static PyObject* audioop_findfit ( PyObject self,
PyObject args 
) [static]

Definition at line 482 of file audioop.c.

{
    short *cp1, *cp2;
    Py_ssize_t len1, len2;
    Py_ssize_t j, best_j;
    double aj_m1, aj_lm1;
    double sum_ri_2, sum_aij_2, sum_aij_ri, result, best_result, factor;

    /* Passing a short** for an 's' argument is correct only
       if the string contents is aligned for interpretation
       as short[]. Due to the definition of PyBytesObject,
       this is currently (Python 2.6) the case. */
    if ( !PyArg_ParseTuple(args, "s#s#:findfit",
                           (char**)&cp1, &len1, (char**)&cp2, &len2) )
        return 0;
    if ( len1 & 1 || len2 & 1 ) {
        PyErr_SetString(AudioopError, "Strings should be even-sized");
        return 0;
    }
    len1 >>= 1;
    len2 >>= 1;

    if ( len1 < len2 ) {
        PyErr_SetString(AudioopError, "First sample should be longer");
        return 0;
    }
    sum_ri_2 = _sum2(cp2, cp2, len2);
    sum_aij_2 = _sum2(cp1, cp1, len2);
    sum_aij_ri = _sum2(cp1, cp2, len2);

    result = (sum_ri_2*sum_aij_2 - sum_aij_ri*sum_aij_ri) / sum_aij_2;

    best_result = result;
    best_j = 0;
    j = 0;

    for ( j=1; j<=len1-len2; j++) {
        aj_m1 = (double)cp1[j-1];
        aj_lm1 = (double)cp1[j+len2-1];

        sum_aij_2 = sum_aij_2 + aj_lm1*aj_lm1 - aj_m1*aj_m1;
        sum_aij_ri = _sum2(cp1+j, cp2, len2);

        result = (sum_ri_2*sum_aij_2 - sum_aij_ri*sum_aij_ri)
            / sum_aij_2;

        if ( result < best_result ) {
            best_result = result;
            best_j = j;
        }

    }

    factor = _sum2(cp1+best_j, cp2, len2) / sum_ri_2;

    return Py_BuildValue("(nf)", best_j, factor);
}

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static PyObject* audioop_findmax ( PyObject self,
PyObject args 
) [static]

Definition at line 576 of file audioop.c.

{
    short *cp1;
    Py_ssize_t len1, len2;
    Py_ssize_t j, best_j;
    double aj_m1, aj_lm1;
    double result, best_result;

    if ( !PyArg_ParseTuple(args, "s#n:findmax",
                           (char**)&cp1, &len1, &len2) )
        return 0;
    if ( len1 & 1 ) {
        PyErr_SetString(AudioopError, "Strings should be even-sized");
        return 0;
    }
    len1 >>= 1;

    if ( len2 < 0 || len1 < len2 ) {
        PyErr_SetString(AudioopError, "Input sample should be longer");
        return 0;
    }

    result = _sum2(cp1, cp1, len2);

    best_result = result;
    best_j = 0;
    j = 0;

    for ( j=1; j<=len1-len2; j++) {
        aj_m1 = (double)cp1[j-1];
        aj_lm1 = (double)cp1[j+len2-1];

        result = result + aj_lm1*aj_lm1 - aj_m1*aj_m1;

        if ( result > best_result ) {
            best_result = result;
            best_j = j;
        }

    }

    return PyLong_FromSsize_t(best_j);
}

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static PyObject* audioop_getsample ( PyObject self,
PyObject args 
) [static]

Definition at line 324 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;

    if ( !PyArg_ParseTuple(args, "s#in:getsample", &cp, &len, &size, &i) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    if ( i < 0 || i >= len/size ) {
        PyErr_SetString(AudioopError, "Index out of range");
        return 0;
    }
    if ( size == 1 )      val = (int)*CHARP(cp, i);
    else if ( size == 2 ) val = (int)*SHORTP(cp, i*2);
    else if ( size == 4 ) val = (int)*LONGP(cp, i*4);
    return PyLong_FromLong(val);
}

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static PyObject* audioop_lin2adpcm ( PyObject self,
PyObject args 
) [static]

Definition at line 1410 of file audioop.c.

{
    signed char *cp;
    signed char *ncp;
    Py_ssize_t len, i;
    int size, val = 0, step, valpred, delta,
        index, sign, vpdiff, diff;
    PyObject *rv, *state, *str;
    int outputbuffer = 0, bufferstep;

    if ( !PyArg_ParseTuple(args, "s#iO:lin2adpcm",
                           &cp, &len, &size, &state) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    str = PyBytes_FromStringAndSize(NULL, len/(size*2));
    if ( str == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(str);

    /* Decode state, should have (value, step) */
    if ( state == Py_None ) {
        /* First time, it seems. Set defaults */
        valpred = 0;
        step = 7;
        index = 0;
    } else if ( !PyArg_ParseTuple(state, "ii", &valpred, &index) )
        return 0;

    step = stepsizeTable[index];
    bufferstep = 1;

    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;

        /* Step 1 - compute difference with previous value */
        diff = val - valpred;
        sign = (diff < 0) ? 8 : 0;
        if ( sign ) diff = (-diff);

        /* Step 2 - Divide and clamp */
        /* Note:
        ** This code *approximately* computes:
        **    delta = diff*4/step;
        **    vpdiff = (delta+0.5)*step/4;
        ** but in shift step bits are dropped. The net result of this
        ** is that even if you have fast mul/div hardware you cannot
        ** put it to good use since the fixup would be too expensive.
        */
        delta = 0;
        vpdiff = (step >> 3);

        if ( diff >= step ) {
            delta = 4;
            diff -= step;
            vpdiff += step;
        }
        step >>= 1;
        if ( diff >= step  ) {
            delta |= 2;
            diff -= step;
            vpdiff += step;
        }
        step >>= 1;
        if ( diff >= step ) {
            delta |= 1;
            vpdiff += step;
        }

        /* Step 3 - Update previous value */
        if ( sign )
            valpred -= vpdiff;
        else
            valpred += vpdiff;

        /* Step 4 - Clamp previous value to 16 bits */
        if ( valpred > 32767 )
            valpred = 32767;
        else if ( valpred < -32768 )
            valpred = -32768;

        /* Step 5 - Assemble value, update index and step values */
        delta |= sign;

        index += indexTable[delta];
        if ( index < 0 ) index = 0;
        if ( index > 88 ) index = 88;
        step = stepsizeTable[index];

        /* Step 6 - Output value */
        if ( bufferstep ) {
            outputbuffer = (delta << 4) & 0xf0;
        } else {
            *ncp++ = (delta & 0x0f) | outputbuffer;
        }
        bufferstep = !bufferstep;
    }
    rv = Py_BuildValue("(O(ii))", str, valpred, index);
    Py_DECREF(str);
    return rv;
}

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static PyObject* audioop_lin2alaw ( PyObject self,
PyObject args 
) [static]

Definition at line 1341 of file audioop.c.

{
    signed char *cp;
    unsigned char *ncp;
    Py_ssize_t len, i;
    int size, val = 0;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#i:lin2alaw",
                           &cp, &len, &size) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, len/size);
    if ( rv == 0 )
        return 0;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;

        *ncp++ = st_linear2alaw(val);
    }
    return rv;
}

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static PyObject* audioop_lin2lin ( PyObject self,
PyObject args 
) [static]

Definition at line 1041 of file audioop.c.

{
    signed char *cp;
    unsigned char *ncp;
    Py_ssize_t len, i, j;
    int size, size2, val = 0;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#ii:lin2lin",
                      &cp, &len, &size, &size2) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;
    if (!audioop_check_size(size2))
        return NULL;

    if (len/size > PY_SSIZE_T_MAX/size2) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }
    rv = PyBytes_FromStringAndSize(NULL, (len/size)*size2);
    if ( rv == 0 )
        return 0;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for ( i=0, j=0; i < len; i += size, j += size2 ) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;

        if ( size2 == 1 )  *CHARP(ncp, j) = (signed char)(val >> 8);
        else if ( size2 == 2 ) *SHORTP(ncp, j) = (short)(val);
        else if ( size2 == 4 ) *LONGP(ncp, j) = (Py_Int32)(val<<16);
    }
    return rv;
}

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static PyObject* audioop_lin2ulaw ( PyObject self,
PyObject args 
) [static]

Definition at line 1272 of file audioop.c.

{
    signed char *cp;
    unsigned char *ncp;
    Py_ssize_t len, i;
    int size, val = 0;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#i:lin2ulaw",
                           &cp, &len, &size) )
        return 0 ;

    if (!audioop_check_parameters(len, size))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, len/size);
    if ( rv == 0 )
        return 0;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;

        *ncp++ = st_14linear2ulaw(val);
    }
    return rv;
}

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static PyObject* audioop_max ( PyObject self,
PyObject args 
) [static]

Definition at line 345 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;
    int max = 0;

    if ( !PyArg_ParseTuple(args, "s#i:max", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    for ( i=0; i<len; i+= size) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        if ( val < 0 ) val = (-val);
        if ( val > max ) max = val;
    }
    return PyLong_FromLong(max);
}

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static PyObject* audioop_maxpp ( PyObject self,
PyObject args 
) [static]

Definition at line 676 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0, prevval = 0, prevextremevalid = 0,
        prevextreme = 0;
    int max = 0;
    int diff, prevdiff, extremediff;

    if ( !PyArg_ParseTuple(args, "s#i:maxpp", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    /* Compute first delta value ahead. Also automatically makes us
    ** skip the first extreme value
    */
    if ( size == 1 )      prevval = (int)*CHARP(cp, 0);
    else if ( size == 2 ) prevval = (int)*SHORTP(cp, 0);
    else if ( size == 4 ) prevval = (int)*LONGP(cp, 0);
    if ( size == 1 )      val = (int)*CHARP(cp, size);
    else if ( size == 2 ) val = (int)*SHORTP(cp, size);
    else if ( size == 4 ) val = (int)*LONGP(cp, size);
    prevdiff = val - prevval;

    for ( i=size; i<len; i+= size) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        diff = val - prevval;
        if ( diff*prevdiff < 0 ) {
            /* Derivative changed sign. Compute difference to
            ** last extreme value and remember.
            */
            if ( prevextremevalid ) {
                extremediff = prevval - prevextreme;
                if ( extremediff < 0 )
                    extremediff = -extremediff;
                if ( extremediff > max )
                    max = extremediff;
            }
            prevextremevalid = 1;
            prevextreme = prevval;
        }
        prevval = val;
        if ( diff != 0 )
            prevdiff = diff;
    }
    return PyLong_FromLong(max);
}

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static PyObject* audioop_minmax ( PyObject self,
PyObject args 
) [static]

Definition at line 367 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;
    int min = 0x7fffffff, max = -0x7fffffff;

    if (!PyArg_ParseTuple(args, "s#i:minmax", &cp, &len, &size))
        return NULL;
    if (!audioop_check_parameters(len, size))
        return NULL;
    for (i = 0; i < len; i += size) {
        if (size == 1) val = (int) *CHARP(cp, i);
        else if (size == 2) val = (int) *SHORTP(cp, i);
        else if (size == 4) val = (int) *LONGP(cp, i);
        if (val > max) max = val;
        if (val < min) min = val;
    }
    return Py_BuildValue("(ii)", min, max);
}

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static PyObject* audioop_mul ( PyObject self,
PyObject args 
) [static]

Definition at line 753 of file audioop.c.

{
    signed char *cp, *ncp;
    Py_ssize_t len, i;
    int size, val = 0;
    double factor, fval, maxval;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#id:mul", &cp, &len, &size, &factor ) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;

    if ( size == 1 ) maxval = (double) 0x7f;
    else if ( size == 2 ) maxval = (double) 0x7fff;
    else if ( size == 4 ) maxval = (double) 0x7fffffff;
    else {
        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
        return 0;
    }

    rv = PyBytes_FromStringAndSize(NULL, len);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(rv);


    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        fval = (double)val*factor;
        if ( fval > maxval ) fval = maxval;
        else if ( fval < -maxval ) fval = -maxval;
        val = (int)fval;
        if ( size == 1 )      *CHARP(ncp, i) = (signed char)val;
        else if ( size == 2 ) *SHORTP(ncp, i) = (short)val;
        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)val;
    }
    return rv;
}

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static PyObject* audioop_ratecv ( PyObject self,
PyObject args 
) [static]

Definition at line 1092 of file audioop.c.

{
    char *cp, *ncp;
    Py_ssize_t len;
    int size, nchannels, inrate, outrate, weightA, weightB;
    int chan, d, *prev_i, *cur_i, cur_o;
    PyObject *state, *samps, *str, *rv = NULL;
    int bytes_per_frame;

    weightA = 1;
    weightB = 0;
    if (!PyArg_ParseTuple(args, "s#iiiiO|ii:ratecv", &cp, &len, &size,
                          &nchannels, &inrate, &outrate, &state,
                          &weightA, &weightB))
        return NULL;
    if (!audioop_check_size(size))
        return NULL;
    if (nchannels < 1) {
        PyErr_SetString(AudioopError, "# of channels should be >= 1");
        return NULL;
    }
    bytes_per_frame = size * nchannels;
    if (bytes_per_frame / nchannels != size) {
        /* This overflow test is rigorously correct because
           both multiplicands are >= 1.  Use the argument names
           from the docs for the error msg. */
        PyErr_SetString(PyExc_OverflowError,
                        "width * nchannels too big for a C int");
        return NULL;
    }
    if (weightA < 1 || weightB < 0) {
        PyErr_SetString(AudioopError,
            "weightA should be >= 1, weightB should be >= 0");
        return NULL;
    }
    if (len % bytes_per_frame != 0) {
        PyErr_SetString(AudioopError, "not a whole number of frames");
        return NULL;
    }
    if (inrate <= 0 || outrate <= 0) {
        PyErr_SetString(AudioopError, "sampling rate not > 0");
        return NULL;
    }
    /* divide inrate and outrate by their greatest common divisor */
    d = gcd(inrate, outrate);
    inrate /= d;
    outrate /= d;

    if ((size_t)nchannels > PY_SIZE_MAX/sizeof(int)) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }
    prev_i = (int *) malloc(nchannels * sizeof(int));
    cur_i = (int *) malloc(nchannels * sizeof(int));
    if (prev_i == NULL || cur_i == NULL) {
        (void) PyErr_NoMemory();
        goto exit;
    }

    len /= bytes_per_frame; /* # of frames */

    if (state == Py_None) {
        d = -outrate;
        for (chan = 0; chan < nchannels; chan++)
            prev_i[chan] = cur_i[chan] = 0;
    }
    else {
        if (!PyArg_ParseTuple(state,
                        "iO!;audioop.ratecv: illegal state argument",
                        &d, &PyTuple_Type, &samps))
            goto exit;
        if (PyTuple_Size(samps) != nchannels) {
            PyErr_SetString(AudioopError,
                            "illegal state argument");
            goto exit;
        }
        for (chan = 0; chan < nchannels; chan++) {
            if (!PyArg_ParseTuple(PyTuple_GetItem(samps, chan),
                                  "ii:ratecv", &prev_i[chan],
                                               &cur_i[chan]))
                goto exit;
        }
    }

    /* str <- Space for the output buffer. */
    {
        /* There are len input frames, so we need (mathematically)
           ceiling(len*outrate/inrate) output frames, and each frame
           requires bytes_per_frame bytes.  Computing this
           without spurious overflow is the challenge; we can
           settle for a reasonable upper bound, though, in this
           case ceiling(len/inrate) * outrate. */

        /* compute ceiling(len/inrate) without overflow */
        Py_ssize_t q = len > 0 ? 1 + (len - 1) / inrate : 0;
        if (outrate > PY_SSIZE_T_MAX / q / bytes_per_frame)
            str = NULL;
        else
            str = PyBytes_FromStringAndSize(NULL,
                                            q * outrate * bytes_per_frame);

        if (str == NULL) {
            PyErr_SetString(PyExc_MemoryError,
                "not enough memory for output buffer");
            goto exit;
        }
    }
    ncp = PyBytes_AsString(str);

    for (;;) {
        while (d < 0) {
            if (len == 0) {
                samps = PyTuple_New(nchannels);
                if (samps == NULL)
                    goto exit;
                for (chan = 0; chan < nchannels; chan++)
                    PyTuple_SetItem(samps, chan,
                        Py_BuildValue("(ii)",
                                      prev_i[chan],
                                      cur_i[chan]));
                if (PyErr_Occurred())
                    goto exit;
                /* We have checked before that the length
                 * of the string fits into int. */
                len = (Py_ssize_t)(ncp - PyBytes_AsString(str));
                rv = PyBytes_FromStringAndSize
                    (PyBytes_AsString(str), len);
                Py_DECREF(str);
                str = rv;
                if (str == NULL)
                    goto exit;
                rv = Py_BuildValue("(O(iO))", str, d, samps);
                Py_DECREF(samps);
                Py_DECREF(str);
                goto exit; /* return rv */
            }
            for (chan = 0; chan < nchannels; chan++) {
                prev_i[chan] = cur_i[chan];
                if (size == 1)
                    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;
                cp += size;
                /* implements a simple digital filter */
                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;
                if (size == 1)
                    *CHARP(ncp, 0) = (signed char)(cur_o >> 8);
                else if (size == 2)
                    *SHORTP(ncp, 0) = (short)(cur_o);
                else if (size == 4)
                    *LONGP(ncp, 0) = (Py_Int32)(cur_o<<16);
                ncp += size;
            }
            d -= inrate;
        }
    }
  exit:
    if (prev_i != NULL)
        free(prev_i);
    if (cur_i != NULL)
        free(cur_i);
    return rv;
}

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static PyObject* audioop_reverse ( PyObject self,
PyObject args 
) [static]

Definition at line 1006 of file audioop.c.

{
    signed char *cp;
    unsigned char *ncp;
    Py_ssize_t len, i, j;
    int size, val = 0;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#i:reverse",
                      &cp, &len, &size) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, len);
    if ( rv == 0 )
        return 0;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;

        j = len - i - size;

        if ( size == 1 )      *CHARP(ncp, j) = (signed char)(val >> 8);
        else if ( size == 2 ) *SHORTP(ncp, j) = (short)(val);
        else if ( size == 4 ) *LONGP(ncp, j) = (Py_Int32)(val<<16);
    }
    return rv;
}

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static PyObject* audioop_rms ( PyObject self,
PyObject args 
) [static]

Definition at line 414 of file audioop.c.

{
    signed char *cp;
    Py_ssize_t len, i;
    int size, val = 0;
    double sum_squares = 0.0;

    if ( !PyArg_ParseTuple(args, "s#i:rms", &cp, &len, &size) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;
    for ( i=0; i<len; i+= size) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);
        sum_squares += (double)val*(double)val;
    }
    if ( len == 0 )
        val = 0;
    else
        val = (int)sqrt(sum_squares / (double)(len/size));
    return PyLong_FromLong(val);
}

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static PyObject* audioop_tomono ( PyObject self,
PyObject args 
) [static]

Definition at line 796 of file audioop.c.

{
    Py_buffer pcp;
    signed char *cp, *ncp;
    Py_ssize_t len, i;
    int size, val1 = 0, val2 = 0;
    double fac1, fac2, fval, maxval;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s*idd:tomono",
                           &pcp, &size, &fac1, &fac2 ) )
        return 0;
    cp = pcp.buf;
    len = pcp.len;
    if (!audioop_check_parameters(len, size)) {
        PyBuffer_Release(&pcp);
        return NULL;
    }
    if (((len / size) & 1) != 0) {
        PyErr_SetString(AudioopError, "not a whole number of frames");
        PyBuffer_Release(&pcp);
        return NULL;
    }

    if ( size == 1 ) maxval = (double) 0x7f;
    else if ( size == 2 ) maxval = (double) 0x7fff;
    else if ( size == 4 ) maxval = (double) 0x7fffffff;
    else {
        PyBuffer_Release(&pcp);
        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
        return 0;
    }

    rv = PyBytes_FromStringAndSize(NULL, len/2);
    if ( rv == 0 ) {
        PyBuffer_Release(&pcp);
        return 0;
    }
    ncp = (signed char *)PyBytes_AsString(rv);


    for ( i=0; i < len; i += size*2 ) {
        if ( size == 1 )      val1 = (int)*CHARP(cp, i);
        else if ( size == 2 ) val1 = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val1 = (int)*LONGP(cp, i);
        if ( size == 1 )      val2 = (int)*CHARP(cp, i+1);
        else if ( size == 2 ) val2 = (int)*SHORTP(cp, i+2);
        else if ( size == 4 ) val2 = (int)*LONGP(cp, i+4);
        fval = (double)val1*fac1 + (double)val2*fac2;
        if ( fval > maxval ) fval = maxval;
        else if ( fval < -maxval ) fval = -maxval;
        val1 = (int)fval;
        if ( size == 1 )      *CHARP(ncp, i/2) = (signed char)val1;
        else if ( size == 2 ) *SHORTP(ncp, i/2) = (short)val1;
        else if ( size == 4 ) *LONGP(ncp, i/2)= (Py_Int32)val1;
    }
    PyBuffer_Release(&pcp);
    return rv;
}

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static PyObject* audioop_tostereo ( PyObject self,
PyObject args 
) [static]

Definition at line 857 of file audioop.c.

{
    signed char *cp, *ncp;
    Py_ssize_t len, i;
    int size, val1, val2, val = 0;
    double fac1, fac2, fval, maxval;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#idd:tostereo",
                           &cp, &len, &size, &fac1, &fac2 ) )
        return 0;
    if (!audioop_check_parameters(len, size))
        return NULL;

    if ( size == 1 ) maxval = (double) 0x7f;
    else if ( size == 2 ) maxval = (double) 0x7fff;
    else if ( size == 4 ) maxval = (double) 0x7fffffff;
    else {
        PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
        return 0;
    }

    if (len > PY_SSIZE_T_MAX/2) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }

    rv = PyBytes_FromStringAndSize(NULL, len*2);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(rv);


    for ( i=0; i < len; i += size ) {
        if ( size == 1 )      val = (int)*CHARP(cp, i);
        else if ( size == 2 ) val = (int)*SHORTP(cp, i);
        else if ( size == 4 ) val = (int)*LONGP(cp, i);

        fval = (double)val*fac1;
        if ( fval > maxval ) fval = maxval;
        else if ( fval < -maxval ) fval = -maxval;
        val1 = (int)fval;

        fval = (double)val*fac2;
        if ( fval > maxval ) fval = maxval;
        else if ( fval < -maxval ) fval = -maxval;
        val2 = (int)fval;

        if ( size == 1 )      *CHARP(ncp, i*2) = (signed char)val1;
        else if ( size == 2 ) *SHORTP(ncp, i*2) = (short)val1;
        else if ( size == 4 ) *LONGP(ncp, i*2) = (Py_Int32)val1;

        if ( size == 1 )      *CHARP(ncp, i*2+1) = (signed char)val2;
        else if ( size == 2 ) *SHORTP(ncp, i*2+2) = (short)val2;
        else if ( size == 4 ) *LONGP(ncp, i*2+4) = (Py_Int32)val2;
    }
    return rv;
}

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static PyObject* audioop_ulaw2lin ( PyObject self,
PyObject args 
) [static]

Definition at line 1303 of file audioop.c.

{
    unsigned char *cp;
    unsigned char cval;
    signed char *ncp;
    Py_ssize_t len, i;
    int size, val;
    PyObject *rv;

    if ( !PyArg_ParseTuple(args, "s#i:ulaw2lin",
                           &cp, &len, &size) )
        return 0;

    if (!audioop_check_parameters(len, size))
        return NULL;

    if (len > PY_SSIZE_T_MAX/size) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return 0;
    }
    rv = PyBytes_FromStringAndSize(NULL, len*size);
    if ( rv == 0 )
        return 0;
    ncp = (signed char *)PyBytes_AsString(rv);

    for ( i=0; i < len*size; i += size ) {
        cval = *cp++;
        val = st_ulaw2linear16(cval);

        if ( size == 1 )      *CHARP(ncp, i) = (signed char)(val >> 8);
        else if ( size == 2 ) *SHORTP(ncp, i) = (short)(val);
        else if ( size == 4 ) *LONGP(ncp, i) = (Py_Int32)(val<<16);
    }
    return rv;
}

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static int gcd ( int  a,
int  b 
) [static]

Definition at line 1081 of file audioop.c.

{
    while (b > 0) {
        int tmp = a % b;
        a = b;
        b = tmp;
    }
    return a;
}

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Definition at line 1653 of file audioop.c.

{
    PyObject *m, *d;
    m = PyModule_Create(&audioopmodule);
    if (m == NULL)
        return NULL;
    d = PyModule_GetDict(m);
    if (d == NULL)
        return NULL;
    AudioopError = PyErr_NewException("audioop.error", NULL, NULL);
    if (AudioopError != NULL)
         PyDict_SetItemString(d,"error",AudioopError);
    return m;
}

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static PyInt16 search ( PyInt16  val,
PyInt16 table,
int  size 
) [static]

Definition at line 56 of file audioop.c.

{
    int i;

    for (i = 0; i < size; i++) {
        if (val <= *table++)
            return (i);
    }
    return (size);
}

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static unsigned char st_14linear2ulaw ( PyInt16  pcm_val) [static]

Definition at line 142 of file audioop.c.

{
    PyInt16         mask;
    PyInt16         seg;
    unsigned char   uval;

    /* The original sox code does this in the calling function, not here */
    pcm_val = pcm_val >> 2;

    /* u-law inverts all bits */
    /* Get the sign and the magnitude of the value. */
    if (pcm_val < 0) {
        pcm_val = -pcm_val;
        mask = 0x7F;
    } else {
        mask = 0xFF;
    }
    if ( pcm_val > CLIP ) pcm_val = CLIP;           /* clip the magnitude */
    pcm_val += (BIAS >> 2);

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_uend, 8);

    /*
     * Combine the sign, segment, quantization bits;
     * and complement the code word.
     */
    if (seg >= 8)           /* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {
        uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
        return (uval ^ mask);
    }

}

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static unsigned char st_linear2alaw ( PyInt16  pcm_val) [static]

Definition at line 239 of file audioop.c.

{
    PyInt16         mask;
    short           seg;
    unsigned char   aval;

    /* The original sox code does this in the calling function, not here */
    pcm_val = pcm_val >> 3;

    /* A-law using even bit inversion */
    if (pcm_val >= 0) {
        mask = 0xD5;            /* sign (7th) bit = 1 */
    } else {
        mask = 0x55;            /* sign bit = 0 */
        pcm_val = -pcm_val - 1;
    }

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_aend, 8);

    /* Combine the sign, segment, and quantization bits. */

    if (seg >= 8)           /* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {
        aval = (unsigned char) seg << SEG_SHIFT;
        if (seg < 2)
            aval |= (pcm_val >> 1) & QUANT_MASK;
        else
            aval |= (pcm_val >> seg) & QUANT_MASK;
        return (aval ^ mask);
    }
}

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Variable Documentation

PyInt16 _st_alaw2linear16[256] [static]

Definition at line 178 of file audioop.c.

PyInt16 _st_ulaw2linear16[256] [static]

Definition at line 69 of file audioop.c.

Initial value:
 {
    { "max", audioop_max, METH_VARARGS },
    { "minmax", audioop_minmax, METH_VARARGS },
    { "avg", audioop_avg, METH_VARARGS },
    { "maxpp", audioop_maxpp, METH_VARARGS },
    { "avgpp", audioop_avgpp, METH_VARARGS },
    { "rms", audioop_rms, METH_VARARGS },
    { "findfit", audioop_findfit, METH_VARARGS },
    { "findmax", audioop_findmax, METH_VARARGS },
    { "findfactor", audioop_findfactor, METH_VARARGS },
    { "cross", audioop_cross, METH_VARARGS },
    { "mul", audioop_mul, METH_VARARGS },
    { "add", audioop_add, METH_VARARGS },
    { "bias", audioop_bias, METH_VARARGS },
    { "ulaw2lin", audioop_ulaw2lin, METH_VARARGS },
    { "lin2ulaw", audioop_lin2ulaw, METH_VARARGS },
    { "alaw2lin", audioop_alaw2lin, METH_VARARGS },
    { "lin2alaw", audioop_lin2alaw, METH_VARARGS },
    { "lin2lin", audioop_lin2lin, METH_VARARGS },
    { "adpcm2lin", audioop_adpcm2lin, METH_VARARGS },
    { "lin2adpcm", audioop_lin2adpcm, METH_VARARGS },
    { "tomono", audioop_tomono, METH_VARARGS },
    { "tostereo", audioop_tostereo, METH_VARARGS },
    { "getsample", audioop_getsample, METH_VARARGS },
    { "reverse", audioop_reverse, METH_VARARGS },
    { "ratecv", audioop_ratecv, METH_VARARGS },
    { 0,          0 }
}

Definition at line 1610 of file audioop.c.

Definition at line 298 of file audioop.c.

int indexTable[16] [static]
Initial value:
 {
    -1, -1, -1, -1, 2, 4, 6, 8,
    -1, -1, -1, -1, 2, 4, 6, 8,
}

Definition at line 275 of file audioop.c.

struct PyModuleDef [static]
Initial value:
 {
    PyModuleDef_HEAD_INIT,
    "audioop",
    NULL,
    -1,
    audioop_methods,
    NULL,
    NULL,
    NULL,
    NULL
}

Definition at line 1640 of file audioop.c.

PyInt16 seg_aend[8] [static]
Initial value:
 {0x1F, 0x3F, 0x7F, 0xFF,
                              0x1FF, 0x3FF, 0x7FF, 0xFFF}

Definition at line 50 of file audioop.c.

PyInt16 seg_uend[8] [static]
Initial value:
 {0x3F, 0x7F, 0xFF, 0x1FF,
                              0x3FF, 0x7FF, 0xFFF, 0x1FFF}

Definition at line 52 of file audioop.c.

int stepsizeTable[89] [static]
Initial value:
 {
    7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
    19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
    50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
    130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
    337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
    876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
    2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
    5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
}

Definition at line 280 of file audioop.c.