ref: a5b327cd4e11cb97cd0d78763df2e56be3ec00d0
dir: /src/pan.c/
/* * (c) 20/03/2000 Fabien COELHO <fabien@coelho.net> for sox. * * Same copyright as SOX. See Sox (and Sun?;-) * * Change panorama of sound file with basic linear volume interpolation. * The human ear is not sensible to phases? What about delay? too short? * * Volume is kept constant (?). * Beware of saturations! * Operations are carried out on floats. * Can handle different number of channels. * Cannot handle rate change. * * Initially based on avg effect. * pan 0.0 basically behaves as avg. */ #include "st_i.h" /* type for computations. float mantissa is okay for 8 or 16 bits signals. maybe a little bit short for 24 bits. switch to double if you're not happy. */ #ifndef PAN_FLOAT #define PAN_FLOAT float /* float or double */ #define PAN_FLOAT_SCAN "%f" /* "%f" or "%lf" */ #endif /* constants */ #define TWO ((PAN_FLOAT)(2.0e0)) #define ONEHALF ((PAN_FLOAT)(1.5e0)) #define ONE ((PAN_FLOAT)(1.0e0)) #define MONE ((PAN_FLOAT)(-1.0e0)) #define HALF ((PAN_FLOAT)(0.5e0)) #define QUARTER ((PAN_FLOAT)(0.25e0)) #define ZERO ((PAN_FLOAT)(0.0e0)) /* error message */ #define PAN_USAGE "Usage: pan direction (in [-1.0 .. 1.0])" /* structure to hold pan parameter */ typedef struct { /* pan option */ PAN_FLOAT dir; /* direction, from left (-1.0) to right (1.0) */ /* local data */ int clipped; /* number of clipped values */ } * pan_t; /* * Process options */ int st_pan_getopts(eff_t effp, int n, char **argv) { pan_t pan = (pan_t) effp->priv; pan->dir = ZERO; /* default is no change */ pan->clipped = 0; if (n && (!sscanf(argv[0], PAN_FLOAT_SCAN, &pan->dir) || pan->dir < MONE || pan->dir > ONE)) { st_fail(PAN_USAGE); return ST_EOF; } return ST_SUCCESS; } /* * Start processing */ int st_pan_start(eff_t effp) { if (effp->outinfo.channels==1) st_warn("PAN onto a mono channel..."); if (effp->outinfo.rate != effp->ininfo.rate) { st_fail("PAN cannot handle different rates (in=%ld, out=%ld)" " use resample or rate", effp->ininfo.rate, effp->outinfo.rate); return ST_EOF; } return ST_SUCCESS; } /* clip value if necessary. see comments about such a function in vol.c * Okay, it might be quite slow to have such a function for so small * a task. Hopefully the function can be inlined by the compiler? */ static st_sample_t clip(pan_t pan, PAN_FLOAT value) { if (value < ST_SAMPLE_MIN) { pan->clipped++; return ST_SAMPLE_MIN; } else if (value > ST_SAMPLE_MAX) { pan->clipped++; return ST_SAMPLE_MAX; } /* else */ return (st_sample_t) value; } #ifndef MIN #define MIN(s1,s2) ((s1)<(s2)?(s1):(s2)) #endif #define UNEXPECTED_CHANNELS \ st_fail("unexpected number of channels (in=%d, out=%d)", ich, och); \ return ST_EOF /* * Process either isamp or osamp samples, whichever is smaller. */ int st_pan_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf, st_size_t *isamp, st_size_t *osamp) { pan_t pan = (pan_t) effp->priv; register st_size_t len; st_size_t done; char ich, och; register PAN_FLOAT left, right, dir, hdir; dir = pan->dir; /* -1 <= dir <= 1 */ hdir = HALF * dir; /* -0.5 <= hdir <= 0.5 */ left = HALF - hdir; /* 0 <= left <= 1 */ right = HALF + hdir; /* 0 <= right <= 1 */ ich = effp->ininfo.channels; och = effp->outinfo.channels; len = MIN(*osamp/och,*isamp/ich); /* report back how much is processed. */ *isamp = len*ich; *osamp = len*och; /* 9 different cases to handle: (1,2,4) X (1,2,4) */ switch (och) { case 1: /* pan on mono channel... not much sense. just avg. */ switch (ich) { case 1: /* simple copy */ for (done=0; done<len; done++) *obuf++ = *ibuf++; break; case 2: /* average 2 */ for (done=0; done<len; done++) *obuf++ = clip(pan, HALF*ibuf[0] + HALF*ibuf[1]), ibuf += 2; break; case 4: /* average 4 */ for (done=0; done<len; done++) *obuf++ = clip(pan, QUARTER*ibuf[0] + QUARTER*ibuf[1] + QUARTER*ibuf[2] + QUARTER*ibuf[3]), ibuf += 4; break; default: UNEXPECTED_CHANNELS; break; } /* end first switch in channel */ break; case 2: switch (ich) { case 1: /* linear */ for (done=0; done<len; done++) { obuf[0] = clip(pan, left * ibuf[0]); obuf[1] = clip(pan, right * ibuf[0]); obuf += 2; ibuf++; } break; case 2: /* linear panorama. * I'm not sure this is the right way to do it. */ if (dir <= ZERO) /* to the left */ { register PAN_FLOAT volume, cll, clr, cr; volume = ONE - HALF*dir; cll = volume*(ONEHALF-left); clr = volume*(left-HALF); cr = volume*(ONE+dir); for (done=0; done<len; done++) { obuf[0] = clip(pan, cll * ibuf[0] + clr * ibuf[1]); obuf[1] = clip(pan, cr * ibuf[1]); obuf += 2; ibuf += 2; } } else /* to the right */ { register PAN_FLOAT volume, cl, crl, crr; volume = ONE + HALF*dir; cl = volume*(ONE-dir); crl = volume*(right-HALF); crr = volume*(ONEHALF-right); for (done=0; done<len; done++) { obuf[0] = clip(pan, cl * ibuf[0]); obuf[1] = clip(pan, crl * ibuf[0] + crr * ibuf[1]); obuf += 2; ibuf += 2; } } break; case 4: if (dir <= ZERO) /* to the left */ { register PAN_FLOAT volume, cll, clr, cr; volume = ONE - HALF*dir; cll = volume*(ONEHALF-left); clr = volume*(left-HALF); cr = volume*(ONE+dir); for (done=0; done<len; done++) { register PAN_FLOAT ibuf0, ibuf1; /* build stereo signal */ ibuf0 = HALF*ibuf[0] + HALF*ibuf[2]; ibuf1 = HALF*ibuf[1] + HALF*ibuf[3]; /* pan it */ obuf[0] = clip(pan, cll * ibuf0 + clr * ibuf1); obuf[1] = clip(pan, cr * ibuf1); obuf += 2; ibuf += 4; } } else /* to the right */ { register PAN_FLOAT volume, cl, crl, crr; volume = ONE + HALF*dir; cl = volume*(ONE-dir); crl = volume*(right-HALF); crr = volume*(ONEHALF-right); for (done=0; done<len; done++) { register PAN_FLOAT ibuf0, ibuf1; ibuf0 = HALF*ibuf[0] + HALF*ibuf[2]; ibuf1 = HALF*ibuf[1] + HALF*ibuf[3]; obuf[0] = clip(pan, cl * ibuf0); obuf[1] = clip(pan, crl * ibuf0 + crr * ibuf1); obuf += 2; ibuf += 4; } } break; default: UNEXPECTED_CHANNELS; break; } /* end second switch in channel */ break; case 4: switch (ich) { case 1: /* linear */ { register PAN_FLOAT cr, cl; cl = HALF*left; cr = HALF*right; for (done=0; done<len; done++) { obuf[0] = clip(pan, cl * ibuf[0]); obuf[2] = obuf[0]; obuf[1] = clip(pan, cr * ibuf[0]); ibuf[3] = obuf[1]; obuf += 4; ibuf++; } } break; case 2: /* simple linear panorama */ if (dir <= ZERO) /* to the left */ { register PAN_FLOAT volume, cll, clr, cr; volume = HALF - QUARTER*dir; cll = volume * (ONEHALF-left); clr = volume * (left-HALF); cr = volume * (ONE+dir); for (done=0; done<len; done++) { obuf[0] = clip(pan, cll * ibuf[0] + clr * ibuf[1]); obuf[2] = obuf[0]; obuf[1] = clip(pan, cr * ibuf[1]); ibuf[3] = obuf[1]; obuf += 4; ibuf += 2; } } else /* to the right */ { register PAN_FLOAT volume, cl, crl, crr; volume = HALF + QUARTER*dir; cl = volume * (ONE-dir); crl = volume * (right-HALF); crr = volume * (ONEHALF-right); for (done=0; done<len; done++) { obuf[0] = clip(pan, cl * ibuf[0]); obuf[2] = obuf[0]; obuf[1] = clip(pan, crl * ibuf[0] + crr * ibuf[1]); ibuf[3] = obuf[1]; obuf += 4; ibuf += 2; } } break; case 4: /* maybe I could improve the formula to reverse... also, turn only by quarters. */ if (dir <= ZERO) /* to the left */ { register PAN_FLOAT cown, cright; cright = -dir; cown = ONE + dir; for (done=0; done<len; done++) { obuf[0] = clip(pan, cown*ibuf[0] + cright*ibuf[1]); obuf[1] = clip(pan, cown*ibuf[1] + cright*ibuf[3]); obuf[2] = clip(pan, cown*ibuf[2] + cright*ibuf[0]); obuf[3] = clip(pan, cown*ibuf[3] + cright*ibuf[2]); obuf += 4; ibuf += 4; } } else /* to the right */ { register PAN_FLOAT cleft, cown; cleft = dir; cown = ONE - dir; for (done=0; done<len; done++) { obuf[0] = clip(pan, cleft*ibuf[2] + cown*ibuf[0]); obuf[1] = clip(pan, cleft*ibuf[0] + cown*ibuf[1]); obuf[2] = clip(pan, cleft*ibuf[3] + cown*ibuf[2]); obuf[3] = clip(pan, cleft*ibuf[1] + cown*ibuf[3]); obuf += 4; ibuf += 4; } } break; default: UNEXPECTED_CHANNELS; break; } /* end third switch in channel */ break; default: UNEXPECTED_CHANNELS; break; } /* end switch out channel */ return ST_SUCCESS; } /* * Do anything required when you stop reading samples. * Don't close input file! * * Should have statistics on right, left, and output amplitudes. */ int st_pan_stop(eff_t effp) { pan_t pan = (pan_t) effp->priv; if (pan->clipped) { st_warn("PAN clipped %d values, maybe adjust volume?", pan->clipped); } return ST_SUCCESS; }