149 lines
4.2 KiB
C
149 lines
4.2 KiB
C
/*
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ntom.c: N->M down/up sampling; the setup code.
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copyright 1995-2023 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Michael Hipp
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*/
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#define SAFE_NTOM /* Do not depend on int64_t*int64_t with big values still being in the range... */
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#include "mpg123lib_intern.h"
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#include "debug.h"
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int INT123_synth_ntom_set_step(mpg123_handle *fr)
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{
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long m,n;
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m = INT123_frame_freq(fr);
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n = fr->af.rate;
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if(VERBOSE2)
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fprintf(stderr,"Init rate converter: %ld->%ld\n",m,n);
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if(n > NTOM_MAX_FREQ || m > NTOM_MAX_FREQ || m <= 0 || n <= 0) {
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if(NOQUIET) error("NtoM converter: illegal rates");
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fr->err = MPG123_BAD_RATE;
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return -1;
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}
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n *= NTOM_MUL;
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fr->ntom_step = (unsigned long) n / m;
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if(fr->ntom_step > (unsigned long)NTOM_MAX*NTOM_MUL) {
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if(NOQUIET) error3("max. 1:%i conversion allowed (%lu vs %lu)!", NTOM_MAX, fr->ntom_step, (unsigned long)8*NTOM_MUL);
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fr->err = MPG123_BAD_RATE;
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return -1;
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}
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fr->INT123_ntom_val[0] = fr->INT123_ntom_val[1] = INT123_ntom_val(fr, fr->num);
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return 0;
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}
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/*
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The SAFE_NTOM does iterative loops instead of straight multiplication.
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The safety is not just about the algorithm closely mimicking the decoder instead of applying some formula,
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it is more about avoiding multiplication of possibly big sample offsets (a 32bit int64_t could overflow too easily).
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*/
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unsigned long INT123_ntom_val(mpg123_handle *fr, int64_t frame)
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{
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int64_t ntm;
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#ifdef SAFE_NTOM /* Carry out the loop, without the threatening integer overflow. */
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int64_t f;
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ntm = NTOM_MUL>>1; /* for frame 0 */
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for(f=0; f<frame; ++f) /* for frame > 0 */
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{
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ntm += fr->spf*fr->ntom_step;
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ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
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}
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#else /* Just make one computation with overall sample offset. */
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ntm = (NTOM_MUL>>1) + fr->spf*frame*fr->ntom_step;
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ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
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#endif
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return (unsigned long) ntm;
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}
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/* Set the ntom value for next expected frame to be decoded.
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This is for keeping output consistent across seeks. */
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void INT123_ntom_set_ntom(mpg123_handle *fr, int64_t num)
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{
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fr->INT123_ntom_val[1] = fr->INT123_ntom_val[0] = INT123_ntom_val(fr, num);
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}
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/* Carry out the ntom sample count operation for this one frame.
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No fear of integer overflow here. */
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int64_t INT123_ntom_frame_outsamples(mpg123_handle *fr)
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{
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/* The do this before decoding the separate channels, so there is only one common ntom value. */
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int ntm = fr->INT123_ntom_val[0];
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ntm += fr->spf*fr->ntom_step;
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return ntm/NTOM_MUL;
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}
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/* Convert frame offset to unadjusted output sample offset. */
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int64_t INT123_ntom_frmouts(mpg123_handle *fr, int64_t frame)
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{
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#ifdef SAFE_NTOM
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int64_t f;
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#endif
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int64_t soff = 0;
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int64_t ntm = INT123_ntom_val(fr,0);
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#ifdef SAFE_NTOM
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if(frame <= 0) return 0;
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for(f=0; f<frame; ++f)
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{
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ntm += fr->spf*fr->ntom_step;
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soff += ntm/NTOM_MUL;
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ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
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}
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#else
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soff = (ntm + frame*(int64_t)fr->spf*(int64_t)fr->ntom_step)/(int64_t)NTOM_MUL;
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#endif
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return soff;
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}
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/* Convert input samples to unadjusted output samples. */
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int64_t INT123_ntom_ins2outs(mpg123_handle *fr, int64_t ins)
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{
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int64_t soff = 0;
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int64_t ntm = INT123_ntom_val(fr,0);
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#ifdef SAFE_NTOM
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{
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int64_t block = fr->spf;
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if(ins <= 0) return 0;
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do
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{
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int64_t nowblock = ins > block ? block : ins;
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ntm += nowblock*fr->ntom_step;
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soff += ntm/NTOM_MUL;
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ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
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ins -= nowblock;
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} while(ins > 0);
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}
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#else
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/* Beware of overflows: when int64_t is 32bits, the multiplication blows too easily.
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Of course, it blows for 64bits, too, in theory, but that's for _really_ large files. */
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soff = ((int64_t)ntm + (int64_t)ins*(int64_t)fr->ntom_step)/(int64_t)NTOM_MUL;
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#endif
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return soff;
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}
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/* Determine frame offset from unadjusted output sample offset. */
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int64_t INT123_ntom_frameoff(mpg123_handle *fr, int64_t soff)
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{
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int64_t ioff = 0; /* frames or samples */
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int64_t ntm = INT123_ntom_val(fr,0);
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#ifdef SAFE_NTOM
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if(soff <= 0) return 0;
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for(ioff=0; 1; ++ioff)
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{
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ntm += fr->spf*fr->ntom_step;
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if(ntm/NTOM_MUL > soff) break;
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soff -= ntm/NTOM_MUL;
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ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
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}
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return ioff;
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#else
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ioff = (soff*(int64_t)NTOM_MUL-ntm)/(int64_t)fr->ntom_step;
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return ioff/(int64_t)fr->spf;
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#endif
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}
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