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SF [ 1231053 ] audioop - alaw encoding/decoding added, code updated 

This patch adds a-LAW encoding to audioop and replaces the old
u-LAW encoding/decoding code with the current code from sox.

Possible issues: the code from sox uses int16_t.

Code by Lars Immisch
This commit is contained in:
Anthony Baxter 2006-03-20 05:21:58 +00:00
parent d1e0ef68fb
commit fa86907aae
4 changed files with 349 additions and 98 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
Doc/lib/libaudioop.tex
View File

@ -12,9 +12,10 @@ is the same format as used by the \refmodule{al} and \refmodule{sunaudiodev}
modules. All scalar items are integers, unless specified otherwise.
% This para is mostly here to provide an excuse for the index entries...
This module provides support for u-LAW and Intel/DVI ADPCM encodings.
This module provides support for a-LAW, u-LAW and Intel/DVI ADPCM encodings.
\index{Intel/DVI ADPCM}
\index{ADPCM, Intel/DVI}
\index{a-LAW}
\index{u-LAW}
A few of the more complicated operations only take 16-bit samples,
@ -42,6 +43,13 @@ Return a tuple \code{(\var{sample}, \var{newstate})} where the sample
has the width specified in \var{width}.
\end{funcdesc}
\begin{funcdesc}{alaw2lin}{fragment, width}
Convert sound fragments in a-LAW encoding to linearly encoded sound
fragments. a-LAW encoding always uses 8 bits samples, so \var{width}
refers only to the sample width of the output fragment here.
\versionadded{2.5}
\end{funcdesc}
\begin{funcdesc}{avg}{fragment, width}
Return the average over all samples in the fragment.
\end{funcdesc}
@ -98,10 +106,6 @@ The routine takes time proportional to \code{len(\var{fragment})}.
Return the value of sample \var{index} from the fragment.
\end{funcdesc}
\begin{funcdesc}{lin2lin}{fragment, width, newwidth}
Convert samples between 1-, 2- and 4-byte formats.
\end{funcdesc}
\begin{funcdesc}{lin2adpcm}{fragment, width, state}
Convert samples to 4 bit Intel/DVI ADPCM encoding. ADPCM coding is an
adaptive coding scheme, whereby each 4 bit number is the difference
@ -117,6 +121,18 @@ passed as the state. \var{adpcmfrag} is the ADPCM coded fragment
packed 2 4-bit values per byte.
\end{funcdesc}
\begin{funcdesc}{lin2alaw}{fragment, width}
Convert samples in the audio fragment to a-LAW encoding and return
this as a Python string. a-LAW is an audio encoding format whereby
you get a dynamic range of about 13 bits using only 8 bit samples. It
is used by the Sun audio hardware, among others.
\versionadded{2.5}
\end{funcdesc}
\begin{funcdesc}{lin2lin}{fragment, width, newwidth}
Convert samples between 1-, 2- and 4-byte formats.
\end{funcdesc}
\begin{funcdesc}{lin2ulaw}{fragment, width}
Convert samples in the audio fragment to u-LAW encoding and return
this as a Python string. u-LAW is an audio encoding format whereby

24
Lib/test/test_audioop.py
View File

@ -136,12 +136,30 @@ def testlin2adpcm(data):
return 0
return 1
def testlin2alaw(data):
if verbose:
print 'lin2alaw'
if audioop.lin2alaw(data[0], 1) != '\xd5\xc5\xf5' or \
audioop.lin2alaw(data[1], 2) != '\xd5\xd5\xd5' or \
audioop.lin2alaw(data[2], 4) != '\xd5\xd5\xd5':
return 0
return 1
def testalaw2lin(data):
if verbose:
print 'alaw2lin'
# Cursory
d = audioop.lin2alaw(data[0], 1)
if audioop.alaw2lin(d, 1) != data[0]:
return 0
return 1
def testlin2ulaw(data):
if verbose:
print 'lin2ulaw'
if audioop.lin2ulaw(data[0], 1) != '\377\347\333' or \
audioop.lin2ulaw(data[1], 2) != '\377\377\377' or \
audioop.lin2ulaw(data[2], 4) != '\377\377\377':
if audioop.lin2ulaw(data[0], 1) != '\xff\xe7\xdb' or \
audioop.lin2ulaw(data[1], 2) != '\xff\xff\xff' or \
audioop.lin2ulaw(data[2], 4) != '\xff\xff\xff':
return 0
return 1

3
Misc/NEWS
View File

@ -295,6 +295,9 @@ Core and builtins
Extension Modules
-----------------
- Patch #1231053: The audioop module now supports encoding/decoding of alaw.
In addition, the existing ulaw code was updated.
- RFE #567972: Socket objects' family, type and proto properties are
now exposed via new get...() methods.

394
Modules/audioop.c
View File

@ -22,103 +22,247 @@ typedef unsigned long Py_UInt32;
#endif
#endif
/* Code shamelessly stolen from sox,
/* Code shamelessly stolen from sox, 12.17.7, g711.c
** (c) Craig Reese, Joe Campbell and Jeff Poskanzer 1989 */
#define MINLIN -32768
#define MAXLIN 32767
#define LINCLIP(x) do { if ( x < MINLIN ) x = MINLIN ; \
else if ( x > MAXLIN ) x = MAXLIN; \
} while ( 0 )
static unsigned char st_linear_to_ulaw(int sample);
/*
** This macro converts from ulaw to 16 bit linear, faster.
**
** Jef Poskanzer
** 23 October 1989
**
** Input: 8 bit ulaw sample
** Output: signed 16 bit linear sample
*/
#define st_ulaw_to_linear(ulawbyte) ulaw_table[ulawbyte]
static int ulaw_table[256] = {
-32124, -31100, -30076, -29052, -28028, -27004, -25980, -24956,
-23932, -22908, -21884, -20860, -19836, -18812, -17788, -16764,
-15996, -15484, -14972, -14460, -13948, -13436, -12924, -12412,
-11900, -11388, -10876, -10364, -9852, -9340, -8828, -8316,
-7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140,
-5884, -5628, -5372, -5116, -4860, -4604, -4348, -4092,
-3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004,
-2876, -2748, -2620, -2492, -2364, -2236, -2108, -1980,
-1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436,
-1372, -1308, -1244, -1180, -1116, -1052, -988, -924,
-876, -844, -812, -780, -748, -716, -684, -652,
-620, -588, -556, -524, -492, -460, -428, -396,
-372, -356, -340, -324, -308, -292, -276, -260,
-244, -228, -212, -196, -180, -164, -148, -132,
-120, -112, -104, -96, -88, -80, -72, -64,
-56, -48, -40, -32, -24, -16, -8, 0,
32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956,
23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764,
15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412,
11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316,
7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140,
5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092,
3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004,
2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980,
1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436,
1372, 1308, 1244, 1180, 1116, 1052, 988, 924,
876, 844, 812, 780, 748, 716, 684, 652,
620, 588, 556, 524, 492, 460, 428, 396,
372, 356, 340, 324, 308, 292, 276, 260,
244, 228, 212, 196, 180, 164, 148, 132,
120, 112, 104, 96, 88, 80, 72, 64,
56, 48, 40, 32, 24, 16, 8, 0 };
/* #define ZEROTRAP */ /* turn on the trap as per the MIL-STD */
/* From g711.c:
*
* December 30, 1994:
* Functions linear2alaw, linear2ulaw have been updated to correctly
* convert unquantized 16 bit values.
* Tables for direct u- to A-law and A- to u-law conversions have been
* corrected.
* Borge Lindberg, Center for PersonKommunikation, Aalborg University.
* bli@cpk.auc.dk
*
*/
#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. */
static unsigned char
st_linear_to_ulaw(int sample)
static int16_t seg_aend[8] = {0x1F, 0x3F, 0x7F, 0xFF,
0x1FF, 0x3FF, 0x7FF, 0xFFF};
static int16_t seg_uend[8] = {0x3F, 0x7F, 0xFF, 0x1FF,
0x3FF, 0x7FF, 0xFFF, 0x1FFF};
static int16_t search(int16_t val, int16_t *table, int size)
{
static int exp_lut[256] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};
int sign, exponent, mantissa;
unsigned char ulawbyte;
int i;
/* Get the sample into sign-magnitude. */
sign = (sample >> 8) & 0x80; /* set aside the sign */
if ( sign != 0 ) sample = -sample; /* get magnitude */
if ( sample > CLIP ) sample = CLIP; /* clip the magnitude */
for (i = 0; i < size; i++) {
if (val <= *table++)
return (i);
}
return (size);
}
#define st_ulaw2linear16(uc) (_st_ulaw2linear16[uc])
#define st_alaw2linear16(uc) (_st_alaw2linear16[uc])
/* Convert from 16 bit linear to ulaw. */
sample = sample + BIAS;
exponent = exp_lut[( sample >> 7 ) & 0xFF];
mantissa = ( sample >> ( exponent + 3 ) ) & 0x0F;
ulawbyte = ~ ( sign | ( exponent << 4 ) | mantissa );
#ifdef ZEROTRAP
if ( ulawbyte == 0 ) ulawbyte = 0x02; /* optional CCITT trap */
#endif
int16_t _st_ulaw2linear16[256] = {
-32124, -31100, -30076, -29052, -28028, -27004, -25980,
-24956, -23932, -22908, -21884, -20860, -19836, -18812,
-17788, -16764, -15996, -15484, -14972, -14460, -13948,
-13436, -12924, -12412, -11900, -11388, -10876, -10364,
-9852, -9340, -8828, -8316, -7932, -7676, -7420,
-7164, -6908, -6652, -6396, -6140, -5884, -5628,
-5372, -5116, -4860, -4604, -4348, -4092, -3900,
-3772, -3644, -3516, -3388, -3260, -3132, -3004,
-2876, -2748, -2620, -2492, -2364, -2236, -2108,
-1980, -1884, -1820, -1756, -1692, -1628, -1564,
-1500, -1436, -1372, -1308, -1244, -1180, -1116,
-1052, -988, -924, -876, -844, -812, -780,
-748, -716, -684, -652, -620, -588, -556,
-524, -492, -460, -428, -396, -372, -356,
-340, -324, -308, -292, -276, -260, -244,
-228, -212, -196, -180, -164, -148, -132,
-120, -112, -104, -96, -88, -80, -72,
-64, -56, -48, -40, -32, -24, -16,
-8, 0, 32124, 31100, 30076, 29052, 28028,
27004, 25980, 24956, 23932, 22908, 21884, 20860,
19836, 18812, 17788, 16764, 15996, 15484, 14972,
14460, 13948, 13436, 12924, 12412, 11900, 11388,
10876, 10364, 9852, 9340, 8828, 8316, 7932,
7676, 7420, 7164, 6908, 6652, 6396, 6140,
5884, 5628, 5372, 5116, 4860, 4604, 4348,
4092, 3900, 3772, 3644, 3516, 3388, 3260,
3132, 3004, 2876, 2748, 2620, 2492, 2364,
2236, 2108, 1980, 1884, 1820, 1756, 1692,
1628, 1564, 1500, 1436, 1372, 1308, 1244,
1180, 1116, 1052, 988, 924, 876, 844,
812, 780, 748, 716, 684, 652, 620,
588, 556, 524, 492, 460, 428, 396,
372, 356, 340, 324, 308, 292, 276,
260, 244, 228, 212, 196, 180, 164,
148, 132, 120, 112, 104, 96, 88,
80, 72, 64, 56, 48, 40, 32,
24, 16, 8, 0
};
return ulawbyte;
/*
* linear2ulaw() accepts a 14-bit signed integer and encodes it as u-law data
* stored in a unsigned char. This function should only be called with
* the data shifted such that it only contains information in the lower
* 14-bits.
*
* In order to simplify the encoding process, the original linear magnitude
* is biased by adding 33 which shifts the encoding range from (0 - 8158) to
* (33 - 8191). The result can be seen in the following encoding table:
*
* Biased Linear Input Code Compressed Code
* ------------------------ ---------------
* 00000001wxyza 000wxyz
* 0000001wxyzab 001wxyz
* 000001wxyzabc 010wxyz
* 00001wxyzabcd 011wxyz
* 0001wxyzabcde 100wxyz
* 001wxyzabcdef 101wxyz
* 01wxyzabcdefg 110wxyz
* 1wxyzabcdefgh 111wxyz
*
* Each biased linear code has a leading 1 which identifies the segment
* number. The value of the segment number is equal to 7 minus the number
* of leading 0's. The quantization interval is directly available as the
* four bits wxyz. * The trailing bits (a - h) are ignored.
*
* Ordinarily the complement of the resulting code word is used for
* transmission, and so the code word is complemented before it is returned.
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
unsigned char st_14linear2ulaw(
int16_t pcm_val) /* 2's complement (14-bit range) */
{
int16_t mask;
int16_t 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);
}
}
int16_t _st_alaw2linear16[256] = {
-5504, -5248, -6016, -5760, -4480, -4224, -4992,
-4736, -7552, -7296, -8064, -7808, -6528, -6272,
-7040, -6784, -2752, -2624, -3008, -2880, -2240,
-2112, -2496, -2368, -3776, -3648, -4032, -3904,
-3264, -3136, -3520, -3392, -22016, -20992, -24064,
-23040, -17920, -16896, -19968, -18944, -30208, -29184,
-32256, -31232, -26112, -25088, -28160, -27136, -11008,
-10496, -12032, -11520, -8960, -8448, -9984, -9472,
-15104, -14592, -16128, -15616, -13056, -12544, -14080,
-13568, -344, -328, -376, -360, -280, -264,
-312, -296, -472, -456, -504, -488, -408,
-392, -440, -424, -88, -72, -120, -104,
-24, -8, -56, -40, -216, -200, -248,
-232, -152, -136, -184, -168, -1376, -1312,
-1504, -1440, -1120, -1056, -1248, -1184, -1888,
-1824, -2016, -1952, -1632, -1568, -1760, -1696,
-688, -656, -752, -720, -560, -528, -624,
-592, -944, -912, -1008, -976, -816, -784,
-880, -848, 5504, 5248, 6016, 5760, 4480,
4224, 4992, 4736, 7552, 7296, 8064, 7808,
6528, 6272, 7040, 6784, 2752, 2624, 3008,
2880, 2240, 2112, 2496, 2368, 3776, 3648,
4032, 3904, 3264, 3136, 3520, 3392, 22016,
20992, 24064, 23040, 17920, 16896, 19968, 18944,
30208, 29184, 32256, 31232, 26112, 25088, 28160,
27136, 11008, 10496, 12032, 11520, 8960, 8448,
9984, 9472, 15104, 14592, 16128, 15616, 13056,
12544, 14080, 13568, 344, 328, 376, 360,
280, 264, 312, 296, 472, 456, 504,
488, 408, 392, 440, 424, 88, 72,
120, 104, 24, 8, 56, 40, 216,
200, 248, 232, 152, 136, 184, 168,
1376, 1312, 1504, 1440, 1120, 1056, 1248,
1184, 1888, 1824, 2016, 1952, 1632, 1568,
1760, 1696, 688, 656, 752, 720, 560,
528, 624, 592, 944, 912, 1008, 976,
816, 784, 880, 848
};
/*
* linear2alaw() accepts an 13-bit signed integer and encodes it as A-law data
* stored in a unsigned char. This function should only be called with
* the data shifted such that it only contains information in the lower
* 13-bits.
*
* Linear Input Code Compressed Code
* ------------------------ ---------------
* 0000000wxyza 000wxyz
* 0000001wxyza 001wxyz
* 000001wxyzab 010wxyz
* 00001wxyzabc 011wxyz
* 0001wxyzabcd 100wxyz
* 001wxyzabcde 101wxyz
* 01wxyzabcdef 110wxyz
* 1wxyzabcdefg 111wxyz
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
unsigned char st_linear2alaw(
int16_t pcm_val) /* 2's complement (13-bit range) */
{
int16_t 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);
}
}
/* End of code taken from sox */
@ -1107,7 +1251,7 @@ audioop_lin2ulaw(PyObject *self, PyObject *args)
else if ( size == 2 ) val = (int)*SHORTP(cp, i);
else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;
*ncp++ = st_linear_to_ulaw(val);
*ncp++ = st_14linear2ulaw(val);
}
return rv;
}
@ -1138,7 +1282,75 @@ audioop_ulaw2lin(PyObject *self, PyObject *args)
for ( i=0; i < len*size; i += size ) {
cval = *cp++;
val = st_ulaw_to_linear(cval);
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;
}
static PyObject *
audioop_lin2alaw(PyObject *self, PyObject *args)
{
signed char *cp;
unsigned char *ncp;
int len, size, val = 0;
PyObject *rv;
int i;
if ( !PyArg_Parse(args, "(s#i)",
&cp, &len, &size) )
return 0;
if ( size != 1 && size != 2 && size != 4) {
PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
return 0;
}
rv = PyString_FromStringAndSize(NULL, len/size);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_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;
}
static PyObject *
audioop_alaw2lin(PyObject *self, PyObject *args)
{
unsigned char *cp;
unsigned char cval;
signed char *ncp;
int len, size, val;
PyObject *rv;
int i;
if ( !PyArg_Parse(args, "(s#i)",
&cp, &len, &size) )
return 0;
if ( size != 1 && size != 2 && size != 4) {
PyErr_SetString(AudioopError, "Size should be 1, 2 or 4");
return 0;
}
rv = PyString_FromStringAndSize(NULL, len*size);
if ( rv == 0 )
return 0;
ncp = (signed char *)PyString_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);
@ -1362,6 +1574,8 @@ static PyMethodDef audioop_methods[] = {
{ "bias", audioop_bias, METH_OLDARGS },
{ "ulaw2lin", audioop_ulaw2lin, METH_OLDARGS },
{ "lin2ulaw", audioop_lin2ulaw, METH_OLDARGS },
{ "alaw2lin", audioop_alaw2lin, METH_OLDARGS },
{ "lin2alaw", audioop_lin2alaw, METH_OLDARGS },
{ "lin2lin", audioop_lin2lin, METH_OLDARGS },
{ "adpcm2lin", audioop_adpcm2lin, METH_OLDARGS },
{ "lin2adpcm", audioop_lin2adpcm, METH_OLDARGS },