ref: 671f0330ac07dac46c5800005c2ef9590dfdf43e
dir: /src/earwax.c/
/* 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; }