/* libSoX earwax - makes listening to headphones easier     November 9, 2000 * * Copyright (c) 2000 Edward Beingessner And Sundry Contributors. * This source code is freely redistributable and may be used for any purpose. * This copyright notice must be maintained.  Edward Beingessner And Sundry * Contributors are not responsible for the consequences of using this * software. * * This effect takes a 44.1kHz stereo (CD format) signal that is meant to be * listened to on headphones, and adds audio cues to move the soundstage from * inside your head (standard for headphones) to outside and in front of the * listener (standard for speakers). This makes the sound much easier to listen * to on headphones. */ #include "sox_i.h"#include <string.h> static const sox_sample_t filt[32 * 2] = {/* 30°  330° */    4,   -6,     /* 32 tap stereo FIR filter. */    4,  -11,     /* One side filters as if the */   -1,   -5,     /* signal was from 30 degrees */    3,    3,     /* from the ear, the other as */   -2,    5,     /* if 330 degrees. */   -5,    0,    9,    1,    6,    3,     /*                         Input                         */   -4,   -1,     /*                   Left         Right                  */   -5,   -3,     /*                __________   __________                */   -2,   -5,     /*               |          | |          |               */   -7,    1,     /*           .---|  Hh,0(f) | |  Hh,0(f) |---.           */    6,   -7,     /*          /    |__________| |__________|    \          */   30,  -29,     /*         /                \ /                \         */   12,   -3,     /*        /                  X                  \        */  -11,    4,     /*       /                  / \                  \       */   -3,    7,     /*  ____V_____   __________V   V__________   _____V____  */  -20,   23,     /* |          | |          |   |          | |          | */    2,    0,     /* | Hh,30(f) | | Hh,330(f)|   | Hh,330(f)| | Hh,30(f) | */    1,   -6,     /* |__________| |__________|   |__________| |__________| */  -14,   -5,     /*      \     ___      /           \      ___     /      */   15,  -18,     /*       \   /   \    /    _____    \    /   \   /       */    6,    7,     /*        `->| + |<--'    /     \    `-->| + |<-'        */   15,  -10,     /*           \___/      _/       \_      \___/           */  -14,   22,     /*               \     / \       / \     /               */   -7,   -2,     /*                `--->| |       | |<---'                */   -4,    9,     /*                     \_/       \_/                     */    6,  -12,     /*                                                       */    6,   -6,     /*                       Headphones                      */    0,  -11,    0,   -5,    4,    0}; #define NUMTAPS array_length(filt)typedef struct {sox_sample_t tap[NUMTAPS];} priv_t; /* FIR filter z^-1 delays */ static int start(sox_effect_t * effp){  priv_t * p = (priv_t *)effp->priv;  if (effp->in_signal.rate != 44100 || effp->in_signal.channels != 2) {    lsx_fail("works only with stereo audio sampled at 44100Hz (i.e. CDDA)");    return SOX_EOF;  }  memset(p->tap, 0, NUMTAPS * sizeof(*p->tap)); /* zero tap memory */  if (effp->in_signal.mult)    *effp->in_signal.mult *= dB_to_linear(-4.4);  return SOX_SUCCESS;} static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,                sox_sample_t * obuf, size_t * isamp, size_t * osamp){  priv_t * p = (priv_t *)effp->priv;  size_t i, len = *isamp = *osamp = min(*isamp, *osamp);   while (len--) {       /* update taps and calculate output */    double output = 0;     for (i = NUMTAPS - 1; i; --i) {      p->tap[i] = p->tap[i - 1];      output += p->tap[i] * filt[i];    }    p->tap[0] = *ibuf++ / 64; /* scale output */    output += p->tap[0] * filt[0];    *obuf++ = SOX_ROUND_CLIP_COUNT(output, effp->clips);  }  return SOX_SUCCESS;} /* No drain: preserve audio file length; it's only 32 samples anyway. */ sox_effect_handler_t const *lsx_earwax_effect_fn(void){  static sox_effect_handler_t handler = {"earwax", NULL, SOX_EFF_MCHAN,    NULL, start, flow, NULL, NULL, NULL, sizeof(priv_t)};  return &handler;}