summaryrefslogtreecommitdiffstats
path: root/apps/pcmbuf.c
blob: e23f6d0fb62210ffeca10c88948e001bc006e68e (plain)
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
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2005 by Miika Pekkarinen
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include <stdio.h>
#include "config.h"
#include "system.h"
#include "debug.h"
#include <kernel.h>
#include "pcmbuf.h"
#include "pcm.h"
#include "logf.h"
#ifndef SIMULATOR
#include "cpu.h"
#endif
#include <string.h>
#include "buffer.h"
#include "settings.h"
#include "audio.h"
#include "voice_thread.h"
#include "dsp.h"
#include "thread.h"

/* Clip sample to signed 16 bit range */
static inline int32_t clip_sample_16(int32_t sample)
{
    if ((int16_t)sample != sample)
        sample = 0x7fff ^ (sample >> 31);
    return sample;
}

#if MEMORYSIZE > 2
/* Keep watermark high for iPods at least (2s) */
#define PCMBUF_WATERMARK     (NATIVE_FREQUENCY * 4 * 2)
#else
#define PCMBUF_WATERMARK     (NATIVE_FREQUENCY * 1) /* 0.25 seconds */
#endif

/* Structure we can use to queue pcm chunks in memory to be played
 * by the driver code. */
struct pcmbufdesc
{
    void *addr;
    size_t size;
    struct pcmbufdesc* link;
    /* Call this when the buffer has been played */
    void (*callback)(void);
};

#define PCMBUF_DESCS(bufsize) \
    ((bufsize) / PCMBUF_MINAVG_CHUNK)
#define PCMBUF_DESCS_SIZE(bufsize) \
    (PCMBUF_DESCS(bufsize)*sizeof(struct pcmbufdesc))

/* Size of the PCM buffer. */
static size_t pcmbuf_size IDATA_ATTR = 0;
static char *pcmbuf_bufend IDATA_ATTR;
static char *audiobuffer IDATA_ATTR;
/* Current audio buffer write index. */
static size_t audiobuffer_pos IDATA_ATTR;
/* Amount audiobuffer_pos will be increased.*/
static size_t audiobuffer_fillpos IDATA_ATTR;
static char *fadebuf IDATA_ATTR;
static char *voicebuf IDATA_ATTR;

static void (*pcmbuf_event_handler)(void) IDATA_ATTR;
static void (*position_callback)(size_t size) IDATA_ATTR;

/* Crossfade related state */
static bool crossfade_enabled;
static bool crossfade_enabled_pending;
static bool crossfade_mixmode;
static bool crossfade_active IDATA_ATTR;
static bool crossfade_init IDATA_ATTR;

/* Track the current location for processing crossfade */
static struct pcmbufdesc *crossfade_chunk IDATA_ATTR;
#ifdef HAVE_CROSSFADE
static size_t crossfade_sample IDATA_ATTR;

/* Counters for fading in new data */
static size_t crossfade_fade_in_total IDATA_ATTR;
static size_t crossfade_fade_in_rem IDATA_ATTR;
#endif

static struct pcmbufdesc *pcmbuf_read IDATA_ATTR;
static struct pcmbufdesc *pcmbuf_read_end IDATA_ATTR;
static struct pcmbufdesc *pcmbuf_write IDATA_ATTR;
static struct pcmbufdesc *pcmbuf_write_end IDATA_ATTR;
static size_t last_chunksize IDATA_ATTR;

static size_t pcmbuf_unplayed_bytes IDATA_ATTR;
static size_t pcmbuf_watermark IDATA_ATTR;

static struct pcmbufdesc *pcmbuf_mix_chunk IDATA_ATTR;
static size_t pcmbuf_mix_sample IDATA_ATTR;

static bool low_latency_mode = false;
static bool pcmbuf_flush;

#ifdef HAVE_PRIORITY_SCHEDULING
static int codec_thread_priority = PRIORITY_PLAYBACK;
#endif

extern unsigned int codec_thread_id;

/* Helpful macros for use in conditionals this assumes some of the above
 * static variable names */
#define NEED_FLUSH(position) \
    (audiobuffer_fillpos > PCMBUF_TARGET_CHUNK || position >= pcmbuf_size)
#define LOW_DATA(quarter_secs) \
    (pcmbuf_unplayed_bytes < NATIVE_FREQUENCY * quarter_secs)

static bool prepare_insert(size_t length);
static void pcmbuf_under_watermark(bool under);
static bool pcmbuf_flush_fillpos(void);

#define CALL_IF_EXISTS(function, args...) if (function) function(args)
/* This function has 2 major logical parts (separated by brackets both for
 * readability and variable scoping).  The first part performs the
 * operastions related to finishing off the last buffer we fed to the DMA.
 * The second part performs the operations involved in sending a new buffer
 * to the DMA.  Finally the function checks the status of the buffer and
 * boosts if necessary */
static void pcmbuf_callback(unsigned char** start, size_t* size) ICODE_ATTR;
static void pcmbuf_callback(unsigned char** start, size_t* size)
{
    {
        struct pcmbufdesc *pcmbuf_current = pcmbuf_read;
        /* Take the finished buffer out of circulation */
        pcmbuf_read = pcmbuf_current->link;

        /* The buffer is finished, call the callback functions */
        CALL_IF_EXISTS(position_callback, last_chunksize);
        CALL_IF_EXISTS(pcmbuf_current->callback);

        /* Put the finished buffer back into circulation */
        pcmbuf_write_end->link = pcmbuf_current;
        pcmbuf_write_end = pcmbuf_current;

        /* If we've read over the mix chunk while it's still mixing there */
        if (pcmbuf_current == pcmbuf_mix_chunk)
            pcmbuf_mix_chunk = NULL;
        /* If we've read over the crossfade chunk while it's still fading */
        if (pcmbuf_current == crossfade_chunk)
            crossfade_chunk = pcmbuf_read;
    }

    {
        /* Send the new buffer to the pcm */
        struct pcmbufdesc *pcmbuf_new = pcmbuf_read;
        size_t *realsize = size;
        unsigned char** realstart = start;
        if(pcmbuf_new)
        {
            size_t current_size = pcmbuf_new->size;

            pcmbuf_unplayed_bytes -= current_size;
            last_chunksize = current_size;
            *realsize = current_size;
            *realstart = pcmbuf_new->addr;
        }
        else
        {
            /* No more buffers */
            last_chunksize = 0;
            *realsize = 0;
            *realstart = NULL;
            CALL_IF_EXISTS(pcmbuf_event_handler);
        }
    }
}

void pcmbuf_set_position_callback(void (*callback)(size_t size))
{
    position_callback = callback;
}

static void pcmbuf_set_watermark_bytes(void)
{
    pcmbuf_watermark = (crossfade_enabled && pcmbuf_size) ?
        /* If crossfading, try to keep the buffer full other than 1 second */
        (pcmbuf_size - (NATIVE_FREQUENCY * 4 * 1)) :
        /* Otherwise, just use the default */
        PCMBUF_WATERMARK;
}

/* This is really just part of pcmbuf_flush_fillpos, but is easier to keep
 * in a separate function for the moment */
static inline void pcmbuf_add_chunk(void)
{
    register size_t size = audiobuffer_fillpos;
    /* Grab the next description to write, and change the write pointer */
    register struct pcmbufdesc *pcmbuf_current = pcmbuf_write;
    pcmbuf_write = pcmbuf_current->link;
    /* Fill in the values in the new buffer chunk */
    pcmbuf_current->addr = &audiobuffer[audiobuffer_pos];
    pcmbuf_current->size = size;
    pcmbuf_current->callback = pcmbuf_event_handler;
    pcmbuf_current->link = NULL;
    /* This is single use only */
    pcmbuf_event_handler = NULL;
    if (pcmbuf_read != NULL) {
        if (pcmbuf_flush)
        {
            pcmbuf_write_end->link = pcmbuf_read->link;
            pcmbuf_read->link = pcmbuf_current;
            while (pcmbuf_write_end->link)
            {
                pcmbuf_write_end = pcmbuf_write_end->link;
                pcmbuf_unplayed_bytes -= pcmbuf_write_end->size;
            }
            pcmbuf_flush = false;
        }
        /* If there is already a read buffer setup, add to it */
        else
            pcmbuf_read_end->link = pcmbuf_current;
    } else {
        /* Otherwise create the buffer */
        pcmbuf_read = pcmbuf_current;
    }
    /* This is now the last buffer to read */
    pcmbuf_read_end = pcmbuf_current;

    /* Update bytes counters */
    pcmbuf_unplayed_bytes += size;

    audiobuffer_pos += size;
    if (audiobuffer_pos >= pcmbuf_size)
        audiobuffer_pos -= pcmbuf_size;

    audiobuffer_fillpos = 0;
}

#ifdef HAVE_PRIORITY_SCHEDULING
static void boost_codec_thread(bool boost)
{
    /* Keep voice and codec threads at the same priority or else voice
     * will starve if the codec thread's priority is boosted. */
    if (boost)
    {
        int priority = (PRIORITY_PLAYBACK - PRIORITY_PLAYBACK_MAX)*pcmbuf_unplayed_bytes
                          / (2*NATIVE_FREQUENCY) + PRIORITY_PLAYBACK_MAX;

        if (priority != codec_thread_priority)
        {
            codec_thread_priority = priority;
            thread_set_priority(codec_thread_id, priority);
            voice_thread_set_priority(priority);
        }
    }
    else if (codec_thread_priority != PRIORITY_PLAYBACK)
    {
        thread_set_priority(codec_thread_id, PRIORITY_PLAYBACK);
        voice_thread_set_priority(PRIORITY_PLAYBACK);
        codec_thread_priority = PRIORITY_PLAYBACK;
    }
}
#endif /* HAVE_PRIORITY_SCHEDULING */

static void pcmbuf_under_watermark(bool under)
{
    /* Only codec thread initiates boost - voice boosts the cpu when playing
       a clip */
#ifndef SIMULATOR
    if (thread_get_current() == codec_thread_id)
#endif /* SIMULATOR */
    {
        if (under)
        {
            /* Fill audio buffer by boosting cpu */
            trigger_cpu_boost();
#ifdef HAVE_PRIORITY_SCHEDULING
            /* If buffer is critically low, override UI priority, else
               set back to the original priority. */
            boost_codec_thread(LOW_DATA(2) && pcm_is_playing());
#endif
        }
        else
        {
#ifdef HAVE_PRIORITY_SCHEDULING
            boost_codec_thread(false);
#endif
        }
    }

    /* Disable crossfade if < .5s of audio */
    if (LOW_DATA(2))
    {
        crossfade_active = false;
    }
}

void pcmbuf_set_event_handler(void (*event_handler)(void))
{
    pcmbuf_event_handler = event_handler;
}

unsigned int pcmbuf_get_latency(void)
{
    /* Be careful how this calculation is rearranged, it's easy to overflow */
    size_t bytes = pcmbuf_unplayed_bytes + pcm_get_bytes_waiting();
    return bytes / 4 / (NATIVE_FREQUENCY/1000);
}

void pcmbuf_set_low_latency(bool state)
{
    low_latency_mode = state;
}

bool pcmbuf_is_lowdata(void)
{
    if (!pcm_is_playing() || pcm_is_paused() ||
            crossfade_init || crossfade_active)
        return false;

#if MEMORYSIZE > 2
    /* 1 seconds of buffer is low data */
    return LOW_DATA(4);
#else
    /* under watermark is low data */
    return (pcmbuf_unplayed_bytes < pcmbuf_watermark);
#endif
}

/* Amount of bytes left in the buffer. */
inline size_t pcmbuf_free(void)
{
    if (pcmbuf_read != NULL)
    {
        void *read = pcmbuf_read->addr;
        void *write = &audiobuffer[audiobuffer_pos + audiobuffer_fillpos];
        if (read < write)
            return (size_t)(read - write) + pcmbuf_size;
        else
            return (size_t) (read - write);
    }
    return pcmbuf_size;
}

bool pcmbuf_crossfade_init(bool manual_skip)
{
    /* Can't do two crossfades at once and, no fade if pcm is off now */
    if (crossfade_init || crossfade_active || !pcm_is_playing())
    {
        pcmbuf_play_stop();
        return false;
    }

    trigger_cpu_boost();

    /* Not enough data, or crossfade disabled, flush the old data instead */
    if (LOW_DATA(2) || !pcmbuf_is_crossfade_enabled() || low_latency_mode)
    {
        pcmbuf_flush_fillpos();
        pcmbuf_flush = true;
        return false;
    }

    /* Don't enable mix mode when skipping tracks manually. */
    if (manual_skip)
        crossfade_mixmode = false;
    else
        crossfade_mixmode = global_settings.crossfade_fade_out_mixmode;

    crossfade_init = true;

    return true;

}

void pcmbuf_play_stop(void)
{
    pcm_play_stop();

    pcmbuf_unplayed_bytes = 0;
    pcmbuf_mix_chunk = NULL;
    if (pcmbuf_read) {
        pcmbuf_write_end->link = pcmbuf_read;
        pcmbuf_write_end = pcmbuf_read_end;
        pcmbuf_read = pcmbuf_read_end = NULL;
    }
    audiobuffer_pos = 0;
    audiobuffer_fillpos = 0;
    crossfade_init = false;
    crossfade_active = false;
    pcmbuf_flush = false;

#ifdef HAVE_PRIORITY_SCHEDULING
    /* Can unboost the codec thread here no matter who's calling */
    boost_codec_thread(false);
#endif
}

int pcmbuf_used_descs(void)
{
    struct pcmbufdesc *pcmbuf_temp = pcmbuf_read;
    unsigned int i = 0;
    while (pcmbuf_temp) {
        pcmbuf_temp = pcmbuf_temp->link;
        i++;
    }
    return i;
}

int pcmbuf_descs(void)
{
    return PCMBUF_DESCS(pcmbuf_size);
}

static void pcmbuf_init_pcmbuffers(void)
{
    struct pcmbufdesc *next = pcmbuf_write;
    next++;
    pcmbuf_write_end = pcmbuf_write;
    while ((void *)next < (void *)pcmbuf_bufend) {
        pcmbuf_write_end->link=next;
        pcmbuf_write_end=next;
        next++;
    }
}

static size_t pcmbuf_get_next_required_pcmbuf_size(void)
{
    size_t seconds = 1;

    if (crossfade_enabled_pending)
        seconds += global_settings.crossfade_fade_out_delay
                   + global_settings.crossfade_fade_out_duration;

#if MEMORYSIZE > 2
    /* Buffer has to be at least 2s long. */
    seconds += 2;
#endif
    logf("pcmbuf len: %ld", seconds);
    return seconds * (NATIVE_FREQUENCY*4); /* 2 channels + 2 bytes/sample */
}

static char *pcmbuf_calc_audiobuffer_ptr(size_t bufsize)
{
    return pcmbuf_bufend - (bufsize + PCMBUF_MIX_CHUNK * 2 +
               PCMBUF_DESCS_SIZE(bufsize));
}

bool pcmbuf_is_same_size(void)
{
    if (audiobuffer == NULL)
        return true; /* Not set up yet even once so always */

    size_t bufsize = pcmbuf_get_next_required_pcmbuf_size();
    return pcmbuf_calc_audiobuffer_ptr(bufsize) == audiobuffer;
}

/* Initialize the pcmbuffer the structure looks like this:
 * ...|---------PCMBUF---------|FADEBUF|VOICEBUF|DESCS|... */
size_t pcmbuf_init(unsigned char *bufend)
{
    pcmbuf_bufend = bufend;
    pcmbuf_size = pcmbuf_get_next_required_pcmbuf_size();
    audiobuffer = pcmbuf_calc_audiobuffer_ptr(pcmbuf_size);
    fadebuf = &audiobuffer[pcmbuf_size];
    voicebuf = &fadebuf[PCMBUF_MIX_CHUNK];
    pcmbuf_write = (struct pcmbufdesc *)&voicebuf[PCMBUF_MIX_CHUNK];

    pcmbuf_init_pcmbuffers();

    position_callback = NULL;
    pcmbuf_event_handler = NULL;

    pcmbuf_crossfade_enable_finished();

    pcmbuf_play_stop();

    return pcmbuf_bufend - audiobuffer;
}

size_t pcmbuf_get_bufsize(void)
{
    return pcmbuf_size;
}

#ifdef ROCKBOX_HAS_LOGF
unsigned char * pcmbuf_get_meminfo(size_t *length)
{
    *length = pcmbuf_bufend - audiobuffer;
    return audiobuffer;
}
#endif

void pcmbuf_pause(bool pause)
{
    if (pcm_is_playing())
        pcm_play_pause(!pause);
    else if (!pause)
        pcmbuf_play_start();
}

/* Force playback. */
void pcmbuf_play_start(void)
{
    if (!pcm_is_playing() && pcmbuf_unplayed_bytes && pcmbuf_read != NULL)
    {
        last_chunksize = pcmbuf_read->size;
        pcmbuf_unplayed_bytes -= last_chunksize;
        pcm_play_data(pcmbuf_callback,
            (unsigned char *)pcmbuf_read->addr, last_chunksize);
    }
}

/**
 * Commit samples waiting to the pcm buffer.
 */
static bool pcmbuf_flush_fillpos(void)
{
    if (audiobuffer_fillpos) {
        /* Never use the last buffer descriptor */
        while (pcmbuf_write == pcmbuf_write_end) {
            /* If this happens, something is being stupid */
            if (!pcm_is_playing()) {
                logf("pcmbuf_flush_fillpos error");
                pcmbuf_play_start();
            }
            /* Let approximately one chunk of data playback */
            sleep(HZ*PCMBUF_TARGET_CHUNK/(NATIVE_FREQUENCY*4));
        }
        pcmbuf_add_chunk();
        return true;
    }
    return false;
}

/** 
 * Low memory targets don't have crossfade, so don't compile crossfade
 * specific code in order to save some memory.                         */

#ifdef HAVE_CROSSFADE
/**
 * Completely process the crossfade fade out effect with current pcm buffer.
 */
static void crossfade_process_buffer(size_t fade_in_delay,
        size_t fade_out_delay, size_t fade_out_rem)
{
    if (!crossfade_mixmode)
    {
        /* Fade out the specified amount of the already processed audio */
        size_t total_fade_out = fade_out_rem;
        size_t fade_out_sample;
        struct pcmbufdesc *fade_out_chunk = crossfade_chunk;

        /* Find the right chunk to start fading out */
        fade_out_delay += crossfade_sample * 2;
        while (fade_out_delay != 0 && fade_out_delay >= fade_out_chunk->size)
        {
            fade_out_delay -= fade_out_chunk->size;
            fade_out_chunk = fade_out_chunk->link;
        }
        /* The start sample within the chunk */
        fade_out_sample = fade_out_delay / 2;

        while (fade_out_rem > 0)
        {
            /* Each 1/10 second of audio will have the same fade applied */
            size_t block_rem = MIN(NATIVE_FREQUENCY * 4 / 10, fade_out_rem);
            int factor = (fade_out_rem << 8) / total_fade_out;

            fade_out_rem -= block_rem;

            /* Fade this block */
            while (block_rem > 0 && fade_out_chunk != NULL)
            {
                /* Fade one sample */
                int16_t *buf = (int16_t *)fade_out_chunk->addr;
                int32_t sample = buf[fade_out_sample];
                buf[fade_out_sample++] = (sample * factor) >> 8;

                block_rem -= 2;
                /* Move to the next chunk as needed */
                if (fade_out_sample * 2 >= fade_out_chunk->size)
                {
                    fade_out_chunk = fade_out_chunk->link;
                    fade_out_sample = 0;
                }
            }
        }
    }

    /* Find the right chunk and sample to start fading in */
    fade_in_delay += crossfade_sample * 2;
    while (fade_in_delay != 0 && fade_in_delay >= crossfade_chunk->size)
    {
        fade_in_delay -= crossfade_chunk->size;
        crossfade_chunk = crossfade_chunk->link;
    }
    crossfade_sample = fade_in_delay / 2;
    logf("process done!");
}

/* Initializes crossfader, calculates all necessary parameters and
 * performs fade-out with the pcm buffer.  */
static void crossfade_start(void)
{
    size_t crossfade_rem;
    size_t crossfade_need;
    size_t fade_out_rem;
    size_t fade_out_delay;
    size_t fade_in_delay;

    crossfade_init = false;
    /* Reject crossfade if less than .5s of data */
    if (LOW_DATA(2)) {
        logf("crossfade rejected");
        pcmbuf_play_stop();
        return ;
    }

    logf("crossfade_start");
    pcmbuf_flush_fillpos();
    crossfade_active = true;

    /* Initialize the crossfade buffer size to all of the buffered data that
     * has not yet been sent to the DMA */
    crossfade_rem = pcmbuf_unplayed_bytes;
    crossfade_chunk = pcmbuf_read->link;
    crossfade_sample = 0;

    /* Get fade out delay from settings. */
    fade_out_delay =
        NATIVE_FREQUENCY * global_settings.crossfade_fade_out_delay * 4;

    /* Get fade out duration from settings. */
    fade_out_rem =
        NATIVE_FREQUENCY * global_settings.crossfade_fade_out_duration * 4;

    crossfade_need = fade_out_delay + fade_out_rem;
    /* We want only to modify the last part of the buffer. */
    if (crossfade_rem > crossfade_need)
    {
        size_t crossfade_extra = crossfade_rem - crossfade_need;
        while (crossfade_extra > crossfade_chunk->size)
        {
            crossfade_extra -= crossfade_chunk->size;
            crossfade_chunk = crossfade_chunk->link;
        }
        crossfade_sample = crossfade_extra / 2;
    }
    /* Truncate fade out duration if necessary. */
    else if (crossfade_rem < crossfade_need)
    {
        size_t crossfade_short = crossfade_need - crossfade_rem;
        if (fade_out_rem >= crossfade_short)
            fade_out_rem -= crossfade_short;
        else
        {
            fade_out_delay -= crossfade_short - fade_out_rem;
            fade_out_rem = 0;
        }
    }

    /* Get also fade in duration and delays from settings. */
    crossfade_fade_in_total =
        NATIVE_FREQUENCY * global_settings.crossfade_fade_in_duration * 4;
    crossfade_fade_in_rem = crossfade_fade_in_total;

    fade_in_delay =
        NATIVE_FREQUENCY * global_settings.crossfade_fade_in_delay * 4;

    crossfade_process_buffer(fade_in_delay, fade_out_delay, fade_out_rem);
}

/* Returns the number of bytes _NOT_ mixed */
static size_t crossfade_fade_mix(int factor, const char *buf, size_t fade_rem)
{
    const int16_t *input_buf = (const int16_t *)buf;
    int16_t *output_buf = (int16_t *)(crossfade_chunk->addr);
    int16_t *chunk_end = SKIPBYTES(output_buf, crossfade_chunk->size);
    output_buf = &output_buf[crossfade_sample];
    int32_t sample;

    while (fade_rem)
    {
        /* fade left and right channel at once to keep buffer alignment */
        sample = *input_buf++;
        sample = ((sample * factor) >> 8) + *output_buf;
        *output_buf++ = clip_sample_16(sample);

        sample = *input_buf++;
        sample = ((sample * factor) >> 8) + *output_buf;
        *output_buf++ = clip_sample_16(sample);

        fade_rem -= 4; /* 2 samples, each 16 bit -> 4 bytes */

        if (output_buf >= chunk_end)
        {
            crossfade_chunk = crossfade_chunk->link;
            if (!crossfade_chunk)
                return fade_rem;
            output_buf = (int16_t *)crossfade_chunk->addr;
            chunk_end = SKIPBYTES(output_buf, crossfade_chunk->size);
        }
    }
    crossfade_sample = output_buf - (int16_t *)crossfade_chunk->addr;
    return 0;
}

/* Returns the number of bytes _NOT_ mixed */
static size_t crossfade_mix(const char *buf, size_t length)
{
    const int16_t *input_buf = (const int16_t *)buf;
    int16_t *output_buf = (int16_t *)crossfade_chunk->addr;
    int16_t *chunk_end = SKIPBYTES(output_buf, crossfade_chunk->size);
    output_buf = &output_buf[crossfade_sample];
    int32_t sample;

    while (length)
    {
        /* fade left and right channel at once to keep buffer alignment */
        sample = *input_buf++ + *output_buf;
        *output_buf++ = clip_sample_16(sample);

        sample = *input_buf++ + *output_buf;
        *output_buf++ = clip_sample_16(sample);

        length -= 4; /* 2 samples, each 16 bit -> 4 bytes */

        if (output_buf >= chunk_end)
        {
            crossfade_chunk = crossfade_chunk->link;
            if (!crossfade_chunk)
                return length;

            output_buf = (int16_t *)crossfade_chunk->addr;
            chunk_end = SKIPBYTES(output_buf, crossfade_chunk->size);
        }
    }
    crossfade_sample = output_buf - (int16_t *)crossfade_chunk->addr;
    return 0;
}

static void pcmbuf_flush_buffer(const char *buf, size_t length)
{
    size_t copy_n;
    while (length > 0) {
        size_t audiobuffer_index = audiobuffer_pos + audiobuffer_fillpos;
        if (NEED_FLUSH(audiobuffer_index))
        {
            pcmbuf_flush_fillpos();
            audiobuffer_index = audiobuffer_pos + audiobuffer_fillpos;
        }
        copy_n = MIN(length, pcmbuf_size - audiobuffer_index);
        memcpy(&audiobuffer[audiobuffer_index], buf, copy_n);
        buf += copy_n;
        audiobuffer_fillpos += copy_n;
        length -= copy_n;
    }
}

static void flush_crossfade(char *buf, size_t length)
{
    if (length)
    {
        if (crossfade_fade_in_rem)
        {
            size_t samples;
            int16_t *input_buf;

            /* Fade factor for this packet */
            int factor =
                ((crossfade_fade_in_total - crossfade_fade_in_rem) << 8) /
                crossfade_fade_in_total;
            /* Bytes to fade */
            size_t fade_rem = MIN(length, crossfade_fade_in_rem);

            /* We _will_ fade this many bytes */
            crossfade_fade_in_rem -= fade_rem;

            if (crossfade_chunk)
            {
                /* Mix the data */
                size_t fade_total = fade_rem;
                fade_rem = crossfade_fade_mix(factor, buf, fade_rem);
                length -= fade_total - fade_rem;
                buf += fade_total - fade_rem;
                if (!length)
                    return;
                if (!fade_rem)
                    goto fade_done;
            }

            samples = fade_rem / 2;
            input_buf = (int16_t *)buf;
            /* Fade remaining samples in place */
            while (samples)
            {
                int32_t sample = *input_buf;
                *input_buf++ = (sample * factor) >> 8;
                samples--;
            }
        }

fade_done:
        if (crossfade_chunk)
        {
            /* Mix the data */
            size_t mix_total = length;
            length = crossfade_mix(buf, length);
            buf += mix_total - length;
            if (!length)
                return;
        }

        /* Flush samples to the buffer */
        while (!prepare_insert(length))
            sleep(1);
        pcmbuf_flush_buffer(buf, length);
    }

}
#endif

static bool prepare_insert(size_t length)
{
    if (low_latency_mode)
    {
        /* 1/4s latency. */
        if (!LOW_DATA(1) && pcm_is_playing())
            return false;
    }

    /* Need to save PCMBUF_MIN_CHUNK to prevent wrapping overwriting */
    if (pcmbuf_free() < length + PCMBUF_MIN_CHUNK)
        return false;

    if (!pcm_is_playing())
    {
        trigger_cpu_boost();

        /* Pre-buffer up to watermark */
#if MEMORYSIZE > 2
        if (!LOW_DATA(4))
#else
        if (pcmbuf_unplayed_bytes > pcmbuf_watermark)
#endif
        {
            logf("pcm starting");
            if (!(audio_status() & AUDIO_STATUS_PAUSE))
                pcmbuf_play_start();
        }
    }
    else
        pcmbuf_under_watermark(pcmbuf_unplayed_bytes <= pcmbuf_watermark);

    return true;
}

void* pcmbuf_request_buffer(int *count)
{
#ifdef HAVE_CROSSFADE
    if (crossfade_init)
        crossfade_start();
#endif

    if (crossfade_active) {
        *count = MIN(*count, PCMBUF_MIX_CHUNK/4);
        return fadebuf;
    }
    else
    {
        if(prepare_insert(*count << 2))
        {
            size_t audiobuffer_index = audiobuffer_pos + audiobuffer_fillpos;
            if (pcmbuf_size - audiobuffer_index >= PCMBUF_MIN_CHUNK)
            {
                /* Usual case, there's space here */
                return &audiobuffer[audiobuffer_index];
            }
            else
            {
                /* Flush and wrap the buffer */
                pcmbuf_flush_fillpos();
                audiobuffer_pos = 0;
                return &audiobuffer[0];
            }
        }
        else
        {
            return NULL;
        }
    }
}

void * pcmbuf_request_voice_buffer(int *count)
{
    /* A get-it-to-work-for-now hack (audio status could change by
       completion) */
    if (audio_status() & AUDIO_STATUS_PLAY)
    {
        if (pcmbuf_read == NULL)
        {
            return NULL;
        }
        else if (pcmbuf_usage() >= 10 && pcmbuf_mix_free() >= 30 &&
                 (pcmbuf_mix_chunk || pcmbuf_read->link))
        {
            *count = MIN(*count, PCMBUF_MIX_CHUNK/4);
            return voicebuf;
        }
        else
        {
            return NULL;
        }
    }
    else
    {
        return pcmbuf_request_buffer(count);
    }
}

bool pcmbuf_is_crossfade_active(void)
{
    return crossfade_active || crossfade_init;
}

void pcmbuf_write_complete(int count)
{
    size_t length = (size_t)(unsigned int)count << 2;
#ifdef HAVE_CROSSFADE
    if (crossfade_active)
    {
        flush_crossfade(fadebuf, length);
        if (!(crossfade_fade_in_rem || crossfade_chunk))
            crossfade_active = false;
    }
    else
#endif    
    {
        audiobuffer_fillpos += length;

        if (NEED_FLUSH(audiobuffer_pos + audiobuffer_fillpos))
            pcmbuf_flush_fillpos();
    }
}

#if 0
bool pcmbuf_insert_buffer(char *buf, int count)
{
    size_t length = (size_t)(unsigned int)count << 2;

    if (crossfade_active)
    {
        flush_crossfade(buf, length);
        if (!(crossfade_fade_in_rem || crossfade_chunk))
            crossfade_active = false;
    }
    else
    {
        if (!prepare_insert(length))
            return false;
        pcmbuf_flush_buffer(buf, length);
    }
    return true;
}
#endif

#ifndef HAVE_HARDWARE_BEEP
#define MINIBUF_SAMPLES (NATIVE_FREQUENCY / 1000 * KEYCLICK_DURATION)
#define MINIBUF_SIZE (MINIBUF_SAMPLES*4)

/* Generates a constant square wave sound with a given frequency
   in Hertz for a duration in milliseconds. */
void pcmbuf_beep(unsigned int frequency, size_t duration, int amplitude)
{
    unsigned int step = 0xffffffffu / NATIVE_FREQUENCY * frequency;
    int32_t phase = 0;
    int16_t *bufptr, *bufstart, *bufend;
    int32_t sample;
    int nsamples = NATIVE_FREQUENCY / 1000 * duration;
    bool mix = pcmbuf_read != NULL && pcmbuf_read->link != NULL;
    int i;

    bufend = SKIPBYTES((int16_t *)audiobuffer, pcmbuf_size);

    /* Find the insertion point and set bufstart to the start of it */
    if (mix)
    {
        /* Get the currently playing chunk at the current position. */
        bufstart = (int16_t *)pcm_play_dma_get_peak_buffer(&i);

        /* If above isn't implemented or pcm is stopped, no beepeth. */
        if (!bufstart || !pcm_is_playing())
            return;

        /* Give 5ms clearance. */    
        bufstart += NATIVE_FREQUENCY * 4 / 200;

#ifdef HAVE_PCM_DMA_ADDRESS
        /* Returned peak addresses are DMA addresses */
        bufend = pcm_dma_addr(bufend);
#endif

        /* Wrapped above? */
        if (bufstart >= bufend)
            bufstart -= pcmbuf_size;

        /* NOTE: On some targets using hardware DMA, cache range flushing may
         * be required or the writes may not be picked up by the controller.
         * An incremental flush should be done periodically during the mixdown. */
    }
    else if (nsamples <= MINIBUF_SAMPLES)
    {
        static int16_t minibuf[MINIBUF_SAMPLES*2] __attribute__((aligned(4)));
        /* Use mini buffer */
        bufstart = minibuf;
        bufend = SKIPBYTES(bufstart, MINIBUF_SIZE);
    }
    else if (audio_buffer_state() != AUDIOBUF_STATE_TRASHED)
    {
        /* Use audiobuffer */
        bufstart = (int16_t *)audiobuffer;
    }
    else
    {
        /* No place */
        return;
    }

    bufptr = bufstart;

    /* Mix square wave into buffer */
    for (i = 0; i < nsamples; ++i)
    {
        int32_t amp = (phase >> 31) ^ (int32_t)amplitude;
        sample = mix ? *bufptr : 0;
        *bufptr++ = clip_sample_16(sample + amp);
        if (bufptr >= bufend)
            bufptr = (int16_t *)audiobuffer;
        sample = mix ? *bufptr : 0;
        *bufptr++ = clip_sample_16(sample + amp);
        if (bufptr >= bufend)
            bufptr = (int16_t *)audiobuffer;

        phase += step;
    }

    pcm_play_lock();
#ifdef HAVE_RECORDING
    pcm_rec_lock();
#endif

    /* Kick off playback if required and it won't interfere */
    if (!pcm_is_playing()
#ifdef HAVE_RECORDING
        && !pcm_is_recording()
#endif
        )
    {
        pcm_play_data(NULL, (unsigned char *)bufstart, nsamples * 4);
    }

    pcm_play_unlock();
#ifdef HAVE_RECORDING
    pcm_rec_unlock();
#endif
}
#endif /* HAVE_HARDWARE_BEEP */

/* Returns pcm buffer usage in percents (0 to 100). */
int pcmbuf_usage(void)
{
    return pcmbuf_unplayed_bytes * 100 / pcmbuf_size;
}

int pcmbuf_mix_free(void)
{
    if (pcmbuf_mix_chunk)
    {
        size_t my_mix_end =
            (size_t)&((int16_t *)pcmbuf_mix_chunk->addr)[pcmbuf_mix_sample];
        size_t my_write_pos = (size_t)&audiobuffer[audiobuffer_pos];
        if (my_write_pos < my_mix_end)
            my_write_pos += pcmbuf_size;
        return (my_write_pos - my_mix_end) * 100 / pcmbuf_unplayed_bytes;
    }
    return 100;
}

void pcmbuf_write_voice_complete(int count)
{
    /* A get-it-to-work-for-now hack (audio status could have changed) */
    if (!(audio_status() & AUDIO_STATUS_PLAY))
    {
        pcmbuf_write_complete(count);
        return;
    }

    int16_t *ibuf = (int16_t *)voicebuf;
    int16_t *obuf;
    size_t chunk_samples;

    if (pcmbuf_mix_chunk == NULL && pcmbuf_read != NULL)
    {
        pcmbuf_mix_chunk = pcmbuf_read->link;
        /* Start 1/8s into the next chunk */
        pcmbuf_mix_sample = NATIVE_FREQUENCY * 4 / 16;
    }

    if (!pcmbuf_mix_chunk)
        return;

    obuf = (int16_t *)pcmbuf_mix_chunk->addr;
    chunk_samples = pcmbuf_mix_chunk->size / sizeof (int16_t);

    count <<= 1;

    while (count-- > 0)
    {
        int32_t sample = *ibuf++;

        if (pcmbuf_mix_sample >= chunk_samples)
        {
            pcmbuf_mix_chunk = pcmbuf_mix_chunk->link;
            if (!pcmbuf_mix_chunk)
                return;
            pcmbuf_mix_sample = 0;
            obuf = pcmbuf_mix_chunk->addr;
            chunk_samples = pcmbuf_mix_chunk->size / 2;
        }
        sample += obuf[pcmbuf_mix_sample] >> 2;
        obuf[pcmbuf_mix_sample++] = clip_sample_16(sample);
    }
}

void pcmbuf_crossfade_enable(bool on_off)
{
    /* Next setting to be used, not applied now */
    crossfade_enabled_pending = on_off;
}

void pcmbuf_crossfade_enable_finished(void)
{
    /* Copy the pending setting over now */
    crossfade_enabled = crossfade_enabled_pending;
    pcmbuf_set_watermark_bytes();
}

bool pcmbuf_is_crossfade_enabled(void)
{
    if (global_settings.crossfade == CROSSFADE_ENABLE_SHUFFLE)
        return global_settings.playlist_shuffle;

    return crossfade_enabled;
}

void pcmbuf_play_remainder(void)
{
    if (audiobuffer_fillpos)
        pcmbuf_flush_fillpos();
}