/
SDL_audiocvt.c
594 lines (500 loc) · 18.4 KB
/
SDL_audiocvt.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
/*
Simple DirectMedia Layer
Copyright (C) 1997-2017 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../SDL_internal.h"
/* Functions for audio drivers to perform runtime conversion of audio format */
#include "SDL_audio.h"
#include "SDL_audio_c.h"
#include "SDL_assert.h"
/* Effectively mix right and left channels into a single channel */
static void SDLCALL
SDL_ConvertMono(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
LOG_DEBUG_CONVERT("stereo", "mono");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / 8; i; --i, src += 2) {
*(dst++) = (float) ((((double) src[0]) + ((double) src[1])) * 0.5);
}
cvt->len_cvt /= 2;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
/* Discard top 4 channels */
static void SDLCALL
SDL_ConvertStrip(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
LOG_DEBUG_CONVERT("6 channels", "stereo");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / (sizeof (float) * 6); i; --i, src += 6, dst += 2) {
dst[0] = src[0];
dst[1] = src[1];
}
cvt->len_cvt /= 3;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
/* Discard top 2 channels of 6 */
static void SDLCALL
SDL_ConvertStrip_2(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
float *dst = (float *) cvt->buf;
const float *src = dst;
int i;
LOG_DEBUG_CONVERT("6 channels", "quad");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / (sizeof (float) * 6); i; --i, src += 6, dst += 4) {
dst[0] = src[0];
dst[1] = src[1];
dst[2] = src[2];
dst[3] = src[3];
}
cvt->len_cvt /= 6;
cvt->len_cvt *= 4;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
/* Duplicate a mono channel to both stereo channels */
static void SDLCALL
SDL_ConvertStereo(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
const float *src = (const float *) (cvt->buf + cvt->len_cvt);
float *dst = (float *) (cvt->buf + cvt->len_cvt * 2);
int i;
LOG_DEBUG_CONVERT("mono", "stereo");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / sizeof (float); i; --i) {
src--;
dst -= 2;
dst[0] = dst[1] = *src;
}
cvt->len_cvt *= 2;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
/* Duplicate a stereo channel to a pseudo-5.1 stream */
static void SDLCALL
SDL_ConvertSurround(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
int i;
float lf, rf, ce;
const float *src = (const float *) (cvt->buf + cvt->len_cvt);
float *dst = (float *) (cvt->buf + cvt->len_cvt * 3);
LOG_DEBUG_CONVERT("stereo", "5.1");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / 8; i; --i) {
dst -= 6;
src -= 2;
lf = src[0];
rf = src[1];
ce = (lf * 0.5f) + (rf * 0.5f);
dst[0] = src[0];
dst[1] = src[1];
dst[2] = lf - ce;
dst[3] = rf - ce;
dst[4] = dst[5] = ce;
}
cvt->len_cvt *= 3;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
/* Duplicate a stereo channel to a pseudo-4.0 stream */
static void SDLCALL
SDL_ConvertSurround_4(SDL_AudioCVT * cvt, SDL_AudioFormat format)
{
const float *src = (const float *) (cvt->buf + cvt->len_cvt);
float *dst = (float *) (cvt->buf + cvt->len_cvt * 2);
float lf, rf, ce;
int i;
LOG_DEBUG_CONVERT("stereo", "quad");
SDL_assert(format == AUDIO_F32SYS);
for (i = cvt->len_cvt / 8; i; --i) {
dst -= 4;
src -= 2;
lf = src[0];
rf = src[1];
ce = (lf / 2) + (rf / 2);
dst[0] = src[0];
dst[1] = src[1];
dst[2] = lf - ce;
dst[3] = rf - ce;
}
cvt->len_cvt *= 2;
if (cvt->filters[++cvt->filter_index]) {
cvt->filters[cvt->filter_index] (cvt, format);
}
}
int
SDL_ConvertAudio(SDL_AudioCVT * cvt)
{
/* !!! FIXME: (cvt) should be const; stack-copy it here. */
/* !!! FIXME: (actually, we can't...len_cvt needs to be updated. Grr.) */
/* Make sure there's data to convert */
if (cvt->buf == NULL) {
return SDL_SetError("No buffer allocated for conversion");
}
/* Return okay if no conversion is necessary */
cvt->len_cvt = cvt->len;
if (cvt->filters[0] == NULL) {
return 0;
}
/* Set up the conversion and go! */
cvt->filter_index = 0;
cvt->filters[0] (cvt, cvt->src_format);
return 0;
}
static void SDLCALL
SDL_Convert_Byteswap(SDL_AudioCVT *cvt, SDL_AudioFormat format)
{
#if DEBUG_CONVERT
printf("Converting byte order\n");
#endif
switch (SDL_AUDIO_BITSIZE(format)) {
#define CASESWAP(b) \
case b: { \
Uint##b *ptr = (Uint##b *) cvt->buf; \
int i; \
for (i = cvt->len_cvt / sizeof (*ptr); i; --i, ++ptr) { \
*ptr = SDL_Swap##b(*ptr); \
} \
break; \
}
CASESWAP(16);
CASESWAP(32);
CASESWAP(64);
#undef CASESWAP
default: SDL_assert(!"unhandled byteswap datatype!"); break;
}
if (cvt->filters[++cvt->filter_index]) {
/* flip endian flag for data. */
if (format & SDL_AUDIO_MASK_ENDIAN) {
format &= ~SDL_AUDIO_MASK_ENDIAN;
} else {
format |= SDL_AUDIO_MASK_ENDIAN;
}
cvt->filters[cvt->filter_index](cvt, format);
}
}
static int
SDL_BuildAudioTypeCVTToFloat(SDL_AudioCVT *cvt, const SDL_AudioFormat src_fmt)
{
int retval = 0; /* 0 == no conversion necessary. */
if ((SDL_AUDIO_ISBIGENDIAN(src_fmt) != 0) == (SDL_BYTEORDER == SDL_LIL_ENDIAN)) {
cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;
retval = 1; /* added a converter. */
}
if (!SDL_AUDIO_ISFLOAT(src_fmt)) {
const Uint16 src_bitsize = SDL_AUDIO_BITSIZE(src_fmt);
const Uint16 dst_bitsize = 32;
SDL_AudioFilter filter = NULL;
switch (src_fmt & ~SDL_AUDIO_MASK_ENDIAN) {
case AUDIO_S8: filter = SDL_Convert_S8_to_F32; break;
case AUDIO_U8: filter = SDL_Convert_U8_to_F32; break;
case AUDIO_S16: filter = SDL_Convert_S16_to_F32; break;
case AUDIO_U16: filter = SDL_Convert_U16_to_F32; break;
case AUDIO_S32: filter = SDL_Convert_S32_to_F32; break;
default: SDL_assert(!"Unexpected audio format!"); break;
}
if (!filter) {
return SDL_SetError("No conversion available for these formats");
}
cvt->filters[cvt->filter_index++] = filter;
if (src_bitsize < dst_bitsize) {
const int mult = (dst_bitsize / src_bitsize);
cvt->len_mult *= mult;
cvt->len_ratio *= mult;
} else if (src_bitsize > dst_bitsize) {
cvt->len_ratio /= (src_bitsize / dst_bitsize);
}
retval = 1; /* added a converter. */
}
return retval;
}
static int
SDL_BuildAudioTypeCVTFromFloat(SDL_AudioCVT *cvt, const SDL_AudioFormat dst_fmt)
{
int retval = 0; /* 0 == no conversion necessary. */
if (!SDL_AUDIO_ISFLOAT(dst_fmt)) {
const Uint16 dst_bitsize = SDL_AUDIO_BITSIZE(dst_fmt);
const Uint16 src_bitsize = 32;
SDL_AudioFilter filter = NULL;
switch (dst_fmt & ~SDL_AUDIO_MASK_ENDIAN) {
case AUDIO_S8: filter = SDL_Convert_F32_to_S8; break;
case AUDIO_U8: filter = SDL_Convert_F32_to_U8; break;
case AUDIO_S16: filter = SDL_Convert_F32_to_S16; break;
case AUDIO_U16: filter = SDL_Convert_F32_to_U16; break;
case AUDIO_S32: filter = SDL_Convert_F32_to_S32; break;
default: SDL_assert(!"Unexpected audio format!"); break;
}
if (!filter) {
return SDL_SetError("No conversion available for these formats");
}
cvt->filters[cvt->filter_index++] = filter;
if (src_bitsize < dst_bitsize) {
const int mult = (dst_bitsize / src_bitsize);
cvt->len_mult *= mult;
cvt->len_ratio *= mult;
} else if (src_bitsize > dst_bitsize) {
cvt->len_ratio /= (src_bitsize / dst_bitsize);
}
retval = 1; /* added a converter. */
}
if ((SDL_AUDIO_ISBIGENDIAN(dst_fmt) != 0) == (SDL_BYTEORDER == SDL_LIL_ENDIAN)) {
cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;
retval = 1; /* added a converter. */
}
return retval;
}
/* !!! FIXME: We only have this macro salsa because SDL_AudioCVT doesn't store
!!! FIXME: channel info or integer sample rates, so we have to have
!!! FIXME: function entry points for each supported channel count and
!!! FIXME: multiple vs arbitrary. When we rev the ABI, remove this. */
#define RESAMPLER_FUNCS(chans) \
static void SDLCALL \
SDL_Upsample_Multiple_c##chans(SDL_AudioCVT *cvt, SDL_AudioFormat format) { \
SDL_assert(format == AUDIO_F32SYS); \
SDL_Upsample_Multiple(cvt, chans); \
} \
static void SDLCALL \
SDL_Upsample_Arbitrary_c##chans(SDL_AudioCVT *cvt, SDL_AudioFormat format) { \
SDL_assert(format == AUDIO_F32SYS); \
SDL_Upsample_Arbitrary(cvt, chans); \
}\
static void SDLCALL \
SDL_Downsample_Multiple_c##chans(SDL_AudioCVT *cvt, SDL_AudioFormat format) { \
SDL_assert(format == AUDIO_F32SYS); \
SDL_Downsample_Multiple(cvt, chans); \
} \
static void SDLCALL \
SDL_Downsample_Arbitrary_c##chans(SDL_AudioCVT *cvt, SDL_AudioFormat format) { \
SDL_assert(format == AUDIO_F32SYS); \
SDL_Downsample_Arbitrary(cvt, chans); \
}
RESAMPLER_FUNCS(1)
RESAMPLER_FUNCS(2)
RESAMPLER_FUNCS(4)
RESAMPLER_FUNCS(6)
RESAMPLER_FUNCS(8)
#undef RESAMPLER_FUNCS
static int
SDL_FindFrequencyMultiple(const int src_rate, const int dst_rate)
{
int lo, hi;
SDL_assert(src_rate != 0);
SDL_assert(dst_rate != 0);
SDL_assert(src_rate != dst_rate);
if (src_rate < dst_rate) {
lo = src_rate;
hi = dst_rate;
} else {
lo = dst_rate;
hi = src_rate;
}
if ((hi % lo) != 0)
return 0; /* not a multiple. */
return hi / lo;
}
static SDL_AudioFilter
ChooseResampler(const int dst_channels, const int src_rate, const int dst_rate)
{
const int upsample = (src_rate < dst_rate) ? 1 : 0;
const int multiple = SDL_FindFrequencyMultiple(src_rate, dst_rate);
SDL_AudioFilter filter = NULL;
#define PICK_CHANNEL_FILTER(upordown, resampler) switch (dst_channels) { \
case 1: filter = SDL_##upordown##_##resampler##_c1; break; \
case 2: filter = SDL_##upordown##_##resampler##_c2; break; \
case 4: filter = SDL_##upordown##_##resampler##_c4; break; \
case 6: filter = SDL_##upordown##_##resampler##_c6; break; \
case 8: filter = SDL_##upordown##_##resampler##_c8; break; \
default: break; \
}
if (upsample) {
if (multiple) {
PICK_CHANNEL_FILTER(Upsample, Multiple);
} else {
PICK_CHANNEL_FILTER(Upsample, Arbitrary);
}
} else {
if (multiple) {
PICK_CHANNEL_FILTER(Downsample, Multiple);
} else {
PICK_CHANNEL_FILTER(Downsample, Arbitrary);
}
}
#undef PICK_CHANNEL_FILTER
return filter;
}
static int
SDL_BuildAudioResampleCVT(SDL_AudioCVT * cvt, const int dst_channels,
const int src_rate, const int dst_rate)
{
SDL_AudioFilter filter;
if (src_rate == dst_rate) {
return 0; /* no conversion necessary. */
}
filter = ChooseResampler(dst_channels, src_rate, dst_rate);
if (filter == NULL) {
return SDL_SetError("No conversion available for these rates");
}
/* Update (cvt) with filter details... */
cvt->filters[cvt->filter_index++] = filter;
if (src_rate < dst_rate) {
const double mult = ((double) dst_rate) / ((double) src_rate);
cvt->len_mult *= (int) SDL_ceil(mult);
cvt->len_ratio *= mult;
} else {
cvt->len_ratio /= ((double) src_rate) / ((double) dst_rate);
}
return 1; /* added a converter. */
}
/* Creates a set of audio filters to convert from one format to another.
Returns -1 if the format conversion is not supported, 0 if there's
no conversion needed, or 1 if the audio filter is set up.
*/
int
SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
SDL_AudioFormat src_fmt, Uint8 src_channels, int src_rate,
SDL_AudioFormat dst_fmt, Uint8 dst_channels, int dst_rate)
{
/* Sanity check target pointer */
if (cvt == NULL) {
return SDL_InvalidParamError("cvt");
}
/* there are no unsigned types over 16 bits, so catch this up front. */
if ((SDL_AUDIO_BITSIZE(src_fmt) > 16) && (!SDL_AUDIO_ISSIGNED(src_fmt))) {
return SDL_SetError("Invalid source format");
}
if ((SDL_AUDIO_BITSIZE(dst_fmt) > 16) && (!SDL_AUDIO_ISSIGNED(dst_fmt))) {
return SDL_SetError("Invalid destination format");
}
/* prevent possible divisions by zero, etc. */
if ((src_channels == 0) || (dst_channels == 0)) {
return SDL_SetError("Source or destination channels is zero");
}
if ((src_rate == 0) || (dst_rate == 0)) {
return SDL_SetError("Source or destination rate is zero");
}
#if DEBUG_CONVERT
printf("Build format %04x->%04x, channels %u->%u, rate %d->%d\n",
src_fmt, dst_fmt, src_channels, dst_channels, src_rate, dst_rate);
#endif
/* Start off with no conversion necessary */
SDL_zerop(cvt);
cvt->src_format = src_fmt;
cvt->dst_format = dst_fmt;
cvt->needed = 0;
cvt->filter_index = 0;
cvt->filters[0] = NULL;
cvt->len_mult = 1;
cvt->len_ratio = 1.0;
cvt->rate_incr = ((double) dst_rate) / ((double) src_rate);
/* Type conversion goes like this now:
- byteswap to CPU native format first if necessary.
- convert to native Float32 if necessary.
- resample and change channel count if necessary.
- convert back to native format.
- byteswap back to foreign format if necessary.
The expectation is we can process data faster in float32
(possibly with SIMD), and making several passes over the same
buffer is likely to be CPU cache-friendly, avoiding the
biggest performance hit in modern times. Previously we had
(script-generated) custom converters for every data type and
it was a bloat on SDL compile times and final library size. */
/* see if we can skip float conversion entirely (just a byteswap needed). */
if ((src_rate == dst_rate) && (src_channels == dst_channels) &&
((src_fmt != dst_fmt) &&
((src_fmt & ~SDL_AUDIO_MASK_ENDIAN) == (dst_fmt & ~SDL_AUDIO_MASK_ENDIAN)))) {
cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;
cvt->needed = 1;
return 1;
}
/* Convert data types, if necessary. Updates (cvt). */
if (SDL_BuildAudioTypeCVTToFloat(cvt, src_fmt) == -1) {
return -1; /* shouldn't happen, but just in case... */
}
/* Channel conversion */
if (src_channels != dst_channels) {
if ((src_channels == 1) && (dst_channels > 1)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertStereo;
cvt->len_mult *= 2;
src_channels = 2;
cvt->len_ratio *= 2;
}
if ((src_channels == 2) && (dst_channels == 6)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertSurround;
src_channels = 6;
cvt->len_mult *= 3;
cvt->len_ratio *= 3;
}
if ((src_channels == 2) && (dst_channels == 4)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertSurround_4;
src_channels = 4;
cvt->len_mult *= 2;
cvt->len_ratio *= 2;
}
while ((src_channels * 2) <= dst_channels) {
cvt->filters[cvt->filter_index++] = SDL_ConvertStereo;
cvt->len_mult *= 2;
src_channels *= 2;
cvt->len_ratio *= 2;
}
if ((src_channels == 6) && (dst_channels <= 2)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertStrip;
src_channels = 2;
cvt->len_ratio /= 3;
}
if ((src_channels == 6) && (dst_channels == 4)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertStrip_2;
src_channels = 4;
cvt->len_ratio /= 2;
}
/* This assumes that 4 channel audio is in the format:
Left {front/back} + Right {front/back}
so converting to L/R stereo works properly.
*/
while (((src_channels % 2) == 0) &&
((src_channels / 2) >= dst_channels)) {
cvt->filters[cvt->filter_index++] = SDL_ConvertMono;
src_channels /= 2;
cvt->len_ratio /= 2;
}
if (src_channels != dst_channels) {
/* Uh oh.. */ ;
}
}
/* Do rate conversion, if necessary. Updates (cvt). */
if (SDL_BuildAudioResampleCVT(cvt, dst_channels, src_rate, dst_rate) == -1) {
return -1; /* shouldn't happen, but just in case... */
}
/* Move to final data type. */
if (SDL_BuildAudioTypeCVTFromFloat(cvt, dst_fmt) == -1) {
return -1; /* shouldn't happen, but just in case... */
}
cvt->needed = (cvt->filter_index != 0);
return (cvt->needed);
}
/* vi: set ts=4 sw=4 expandtab: */