ref: 7ecafdb3d70342eaf7e5299cb2989bf1967f1e64
dir: /src/dcshift.c/
/* * dcshift.c * (c) 2000.04.15 Chris Ausbrooks <weed@bucket.pp.ualr.edu> * * based on vol.c which is * (c) 20/03/2000 Fabien COELHO <fabien@coelho.net> for sox. * * DC shift a sound file, with basic linear amplitude formula. * Beware of saturations! clipping is checked and reported. * Cannot handle different number of channels. * Cannot handle rate change. */ #include "st_i.h" #include <math.h> /* exp(), sqrt() */ static st_effect_t st_dcshift_effect; /* type used for computations. */ #ifndef DCSHIFT_FLOAT #define DCSHIFT_FLOAT float #define DCSHIFT_FLOAT_SCAN "%f" #endif /* constants */ #define ZERO ((DCSHIFT_FLOAT)(0.0e0)) #define LOG_10_20 ((DCSHIFT_FLOAT)(0.1151292546497022842009e0)) #define ONE ((DCSHIFT_FLOAT)(1.0e0)) #define TWENTY ((DCSHIFT_FLOAT)(20.0e0)) typedef struct { DCSHIFT_FLOAT dcshift; /* DC shift. */ int uselimiter; /* boolean: are we using the limiter? */ DCSHIFT_FLOAT limiterthreshhold; DCSHIFT_FLOAT limitergain; /* limiter gain. */ int limited; /* number of limited values to report. */ int totalprocessed; int clipped; /* number of clipped values to report. */ } * dcs_t; /* * Process options: dcshift (float) type (amplitude, power, dB) */ int st_dcshift_getopts(eff_t effp, int n, char **argv) { dcs_t dcs = (dcs_t) effp->priv; dcs->dcshift = ONE; /* default is no change */ dcs->uselimiter = 0; /* default is no limiter */ if (n < 1) { st_fail(st_dcshift_effect.usage); return ST_EOF; } if (n && (!sscanf(argv[0], DCSHIFT_FLOAT_SCAN, &dcs->dcshift))) { st_fail(st_dcshift_effect.usage); return ST_EOF; } if (n>1) { if (!sscanf(argv[1], DCSHIFT_FLOAT_SCAN, &dcs->limitergain)) { st_fail(st_dcshift_effect.usage); return ST_EOF; } dcs->uselimiter = 1; /* ok, we'll use it */ /* The following equation is derived so that there is no * discontinuity in output amplitudes */ /* and a ST_SAMPLE_MAX input always maps to a ST_SAMPLE_MAX output * when the limiter is activated. */ /* (NOTE: There **WILL** be a discontinuity in the slope of the * output amplitudes when using the limiter.) */ dcs->limiterthreshhold = ST_SAMPLE_MAX * (ONE - (fabs(dcs->dcshift) - dcs->limitergain)); } return ST_SUCCESS; } /* * Start processing */ int st_dcshift_start(eff_t effp) { dcs_t dcs = (dcs_t) effp->priv; if (effp->outinfo.channels != effp->ininfo.channels) { st_warn("DCSHIFT cannot handle different channels (in=%d, out=%d)" " use avg or pan", effp->ininfo.channels, effp->outinfo.channels); } if (effp->outinfo.rate != effp->ininfo.rate) { st_fail("DCSHIFT cannot handle different rates (in=%ld, out=%ld)" " use resample or rate", effp->ininfo.rate, effp->outinfo.rate); return ST_EOF; } dcs->clipped = 0; dcs->limited = 0; dcs->totalprocessed = 0; return ST_SUCCESS; } /* * Process data. */ int st_dcshift_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf, st_size_t *isamp, st_size_t *osamp) { dcs_t dcs = (dcs_t) effp->priv; register DCSHIFT_FLOAT dcshift = dcs->dcshift; register DCSHIFT_FLOAT limitergain = dcs->limitergain; register DCSHIFT_FLOAT limiterthreshhold = dcs->limiterthreshhold; register DCSHIFT_FLOAT sample; register st_size_t len; len = min(*osamp, *isamp); /* report back dealt with amount. */ *isamp = len; *osamp = len; if (dcs->uselimiter) { dcs->totalprocessed += len; for (;len>0; len--) { sample = *ibuf++; if (sample > limiterthreshhold && dcshift > 0) { sample = (sample - limiterthreshhold) * limitergain / (ST_SAMPLE_MAX - limiterthreshhold) + limiterthreshhold + dcshift; dcs->limited++; } else if (sample < -limiterthreshhold && dcshift < 0) { /* Note this should really be ST_SAMPLE_MIN but * the clip() below will take care of the overflow. */ sample = (sample + limiterthreshhold) * limitergain / (ST_SAMPLE_MAX - limiterthreshhold) - limiterthreshhold + dcshift; dcs->limited++; } else { /* Note this should consider ST_SAMPLE_MIN but * the clip() below will take care of the overflow. */ sample = dcshift * ST_SAMPLE_MAX + sample; } ST_SAMPLE_CLIP_COUNT(sample, dcs->clipped); *obuf++ = sample; } } else { /* quite basic, with clipping */ for (;len>0; len--) { float f; f = dcshift * ST_SAMPLE_MAX + *ibuf++; ST_SAMPLE_CLIP_COUNT(f, dcs->clipped); *obuf++ = f; } } return ST_SUCCESS; } /* * Do anything required when you stop reading samples. * Don't close input file! */ int st_dcshift_stop(eff_t effp) { dcs_t dcs = (dcs_t) effp->priv; if (dcs->limited) { st_warn("DCSHIFT limited %d values (%d percent).", dcs->limited, (int) (dcs->limited * 100.0 / dcs->totalprocessed)); } if (dcs->clipped) { if (dcs->dcshift > 0) { st_warn("DCSHIFT clipped %d values, dcshift=%f too high...", dcs->clipped, dcs->dcshift); } else { st_warn("DCSHIFT clipped %d values, dcshift=%f too low...", dcs->clipped, dcs->dcshift); } } return ST_SUCCESS; } static st_effect_t st_dcshift_effect = { "dcshift", "Usage: dcshift shift [ limitergain ]\n" " The peak limiter has a gain much less than 1.0 (ie 0.05 or 0.02) which is only\n" " used on peaks to prevent clipping. (default is no limiter)", ST_EFF_MCHAN, st_dcshift_getopts, st_dcshift_start, st_dcshift_flow, st_effect_nothing_drain, st_dcshift_stop }; const st_effect_t *st_dcshift_effect_fn(void) { return &st_dcshift_effect; }