ReactOS 0.4.15-dev-8227-g32d615f
ntom.c
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1/*
2 ntom.c: N->M down/up sampling; the setup code.
3
4 copyright 1995-2008 by the mpg123 project - free software under the terms of the LGPL 2.1
5 see COPYING and AUTHORS files in distribution or http://mpg123.org
6 initially written by Michael Hipp
7*/
8
9#define SAFE_NTOM /* Do not depend on off_t*off_t with big values still being in the range... */
10#include "mpg123lib_intern.h"
11#include "debug.h"
12
14{
15 long m,n;
16 m = frame_freq(fr);
17 n = fr->af.rate;
18 if(VERBOSE2)
19 fprintf(stderr,"Init rate converter: %ld->%ld\n",m,n);
20
21 if(n > NTOM_MAX_FREQ || m > NTOM_MAX_FREQ || m <= 0 || n <= 0) {
22 if(NOQUIET) error("NtoM converter: illegal rates");
23 fr->err = MPG123_BAD_RATE;
24 return -1;
25 }
26
27 n *= NTOM_MUL;
28 fr->ntom_step = (unsigned long) n / m;
29
30 if(fr->ntom_step > (unsigned long)NTOM_MAX*NTOM_MUL) {
31 if(NOQUIET) error3("max. 1:%i conversion allowed (%lu vs %lu)!", NTOM_MAX, fr->ntom_step, (unsigned long)8*NTOM_MUL);
32 fr->err = MPG123_BAD_RATE;
33 return -1;
34 }
35
36 fr->ntom_val[0] = fr->ntom_val[1] = ntom_val(fr, fr->num);
37 return 0;
38}
39
40/*
41 The SAFE_NTOM does iterative loops instead of straight multiplication.
42 The safety is not just about the algorithm closely mimicking the decoder instead of applying some formula,
43 it is more about avoiding multiplication of possibly big sample offsets (a 32bit off_t could overflow too easily).
44*/
45
46unsigned long ntom_val(mpg123_handle *fr, off_t frame)
47{
48 off_t ntm;
49#ifdef SAFE_NTOM /* Carry out the loop, without the threatening integer overflow. */
50 off_t f;
51 ntm = NTOM_MUL>>1; /* for frame 0 */
52 for(f=0; f<frame; ++f) /* for frame > 0 */
53 {
54 ntm += fr->spf*fr->ntom_step;
55 ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
56 }
57#else /* Just make one computation with overall sample offset. */
58 ntm = (NTOM_MUL>>1) + fr->spf*frame*fr->ntom_step;
59 ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
60#endif
61 return (unsigned long) ntm;
62}
63
64/* Set the ntom value for next expected frame to be decoded.
65 This is for keeping output consistent across seeks. */
67{
68 fr->ntom_val[1] = fr->ntom_val[0] = ntom_val(fr, num);
69}
70
71/* Carry out the ntom sample count operation for this one frame.
72 No fear of integer overflow here. */
74{
75 /* The do this before decoding the separate channels, so there is only one common ntom value. */
76 int ntm = fr->ntom_val[0];
77 ntm += fr->spf*fr->ntom_step;
78 return ntm/NTOM_MUL;
79}
80
81/* Convert frame offset to unadjusted output sample offset. */
83{
84#ifdef SAFE_NTOM
85 off_t f;
86#endif
87 off_t soff = 0;
88 off_t ntm = ntom_val(fr,0);
89#ifdef SAFE_NTOM
90 if(frame <= 0) return 0;
91 for(f=0; f<frame; ++f)
92 {
93 ntm += fr->spf*fr->ntom_step;
94 soff += ntm/NTOM_MUL;
95 ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
96 }
97#else
98 soff = (ntm + frame*(off_t)fr->spf*(off_t)fr->ntom_step)/(off_t)NTOM_MUL;
99#endif
100 return soff;
101}
102
103/* Convert input samples to unadjusted output samples. */
105{
106 off_t soff = 0;
107 off_t ntm = ntom_val(fr,0);
108#ifdef SAFE_NTOM
109 {
110 off_t block = fr->spf;
111 if(ins <= 0) return 0;
112 do
113 {
114 off_t nowblock = ins > block ? block : ins;
115 ntm += nowblock*fr->ntom_step;
116 soff += ntm/NTOM_MUL;
117 ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
118 ins -= nowblock;
119 } while(ins > 0);
120 }
121#else
122 /* Beware of overflows: when off_t is 32bits, the multiplication blows too easily.
123 Of course, it blows for 64bits, too, in theory, but that's for _really_ large files. */
124 soff = ((off_t)ntm + (off_t)ins*(off_t)fr->ntom_step)/(off_t)NTOM_MUL;
125#endif
126 return soff;
127}
128
129/* Determine frame offset from unadjusted output sample offset. */
131{
132 off_t ioff = 0; /* frames or samples */
133 off_t ntm = ntom_val(fr,0);
134#ifdef SAFE_NTOM
135 if(soff <= 0) return 0;
136 for(ioff=0; 1; ++ioff)
137 {
138 ntm += fr->spf*fr->ntom_step;
139 if(ntm/NTOM_MUL > soff) break;
140 soff -= ntm/NTOM_MUL;
141 ntm -= (ntm/NTOM_MUL)*NTOM_MUL;
142 }
143 return ioff;
144#else
145 ioff = (soff*(off_t)NTOM_MUL-ntm)/(off_t)fr->ntom_step;
146 return ioff/(off_t)fr->spf;
147#endif
148}
#define NTOM_MAX_FREQ
Definition: decode.h:31
#define NTOM_MUL
Definition: decode.h:32
#define NTOM_MAX
Definition: decode.h:30
#define off_t
Definition: dosfsck.h:5
__kernel_off_t off_t
Definition: linux.h:201
GLdouble n
Definition: glext.h:7729
GLfloat f
Definition: glext.h:7540
GLuint GLuint num
Definition: glext.h:9618
const GLfloat * m
Definition: glext.h:10848
@ MPG123_BAD_RATE
Definition: mpg123.h:386
#define stderr
Definition: stdio.h:100
_Check_return_opt_ _CRTIMP int __cdecl fprintf(_Inout_ FILE *_File, _In_z_ _Printf_format_string_ const char *_Format,...)
#define frame_freq
Definition: intsym.h:239
#define ntom_set_ntom
Definition: intsym.h:32
#define ntom_ins2outs
Definition: intsym.h:158
#define ntom_frame_outsamples
Definition: intsym.h:156
#define ntom_frameoff
Definition: intsym.h:159
#define ntom_val
Definition: intsym.h:155
#define ntom_frmouts
Definition: intsym.h:157
#define synth_ntom_set_step
Definition: intsym.h:154
#define f
Definition: ke_i.h:83
#define error(str)
Definition: mkdosfs.c:1605
#define VERBOSE2
#define NOQUIET
#define long
Definition: qsort.c:33
#define error3(s, a, b, c)
Definition: debug.h:127
unsigned long ntom_step
Definition: frame.h:150
unsigned long ntom_val[2]
Definition: frame.h:149
struct audioformat af
Definition: frame.h:268
static unsigned int block
Definition: xmlmemory.c:101