2021-07-12 06:17:47 +00:00
|
|
|
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
|
|
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
|
|
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
|
|
|
│ Copyright 2021 Justine Alexandra Roberts Tunney │
|
|
|
|
│ │
|
|
|
|
│ Permission to use, copy, modify, and/or distribute this software for │
|
|
|
|
│ any purpose with or without fee is hereby granted, provided that the │
|
|
|
|
│ above copyright notice and this permission notice appear in all copies. │
|
|
|
|
│ │
|
|
|
|
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
|
|
|
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
|
|
|
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
|
|
|
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
|
|
|
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
|
|
|
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
|
|
|
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
|
|
|
│ PERFORMANCE OF THIS SOFTWARE. │
|
|
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
2021-09-28 05:58:51 +00:00
|
|
|
#include "dsp/core/core.h"
|
2021-07-12 06:17:47 +00:00
|
|
|
|
2021-09-28 05:58:51 +00:00
|
|
|
/**
|
|
|
|
* Compresses 16-bit signed linear audio sample with μ-Law.
|
|
|
|
*
|
|
|
|
* @param x is clamped to 16-bits of which the top 14 are considered
|
|
|
|
* @return coded number in range [0..255]
|
|
|
|
* @see ITU G.711
|
|
|
|
*/
|
|
|
|
int mulaw(int x) {
|
|
|
|
int b, i, a, s, l, h;
|
|
|
|
a = x < 0 ? (~x >> 2) + 33 : (x >> 2) + 33;
|
|
|
|
if (a > 8191) a = 8191;
|
|
|
|
i = a >> 6;
|
|
|
|
s = i ? (__builtin_clz(i) ^ 31) + 2 : 1;
|
|
|
|
h = 8 - s;
|
|
|
|
l = (a >> s) & 15;
|
|
|
|
l = 15 - l;
|
|
|
|
b = (h << 4) | l;
|
|
|
|
if (x >= 0) b |= 128;
|
|
|
|
return b;
|
2021-07-12 06:17:47 +00:00
|
|
|
}
|