aboutsummaryrefslogblamecommitdiffstats
path: root/us_maker_edition/src/media/UAudioDecoder_FFmpeg.pas
blob: 7ca988856625bd0d4d2b66fa8c95db163f7b4146 (plain) (tree)
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





























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                                                             
{* UltraStar Deluxe - Karaoke Game
 *
 * UltraStar Deluxe is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING. If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 * $URL$
 * $Id$
 *}

unit UAudioDecoder_FFmpeg;

(*******************************************************************************
 *
 * This unit is primarily based upon -
 *   http://www.dranger.com/ffmpeg/ffmpegtutorial_all.html
 *
 *   and tutorial03.c
 *
 *   http://www.inb.uni-luebeck.de/~boehme/using_libavcodec.html
 *
 *******************************************************************************)

interface

{$IFDEF FPC}
  {$MODE Delphi}
{$ENDIF}

{$I switches.inc}

// show FFmpeg specific debug output
{.$DEFINE DebugFFmpegDecode}

// FFmpeg is very verbose and shows a bunch of errors.
// Those errors (they can be considered as warnings by us) can be ignored
// as they do not give any useful information.
// There is no solution to fix this except for turning them off.
{.$DEFINE EnableFFmpegErrorOutput}

implementation

uses
  SDL, // SDL redefines some base types -> include before SysUtils to ignore them
  Classes,
  Math,
  SysUtils,
  avcodec,
  avformat,
  avutil,
  avio,
  mathematics, // used for av_rescale_q
  rational,
  UMusic,
  UIni,
  UMain,
  UMediaCore_FFmpeg,
  ULog,
  UCommon,
  UConfig,
  UPath;

const
  MAX_AUDIOQ_SIZE = (5 * 16 * 1024);

const
  // TODO: The factor 3/2 might not be necessary as we do not need extra
  // space for synchronizing as in the tutorial.
  AUDIO_BUFFER_SIZE = (AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) div 2;

type
  TFFmpegDecodeStream = class(TAudioDecodeStream)
    private
      StateLock:   PSDL_Mutex;

      EOFState:   boolean; // end-of-stream flag (locked by StateLock)
      ErrorState: boolean; // error flag (locked by StateLock)

      QuitRequest: boolean; // (locked by StateLock)
      ParserIdleCond: PSDL_Cond;

      // parser pause/resume data
      ParserLocked:            boolean;
      ParserPauseRequestCount: integer;
      ParserUnlockedCond:      PSDL_Cond;
      ParserResumeCond:        PSDL_Cond;

      SeekRequest: boolean; // (locked by StateLock)
      SeekFlags:   integer; // (locked by StateLock)
      SeekPos:     double;    // stream position to seek for (in secs) (locked by StateLock)
      SeekFlush:   boolean;   // true if the buffers should be flushed after seeking (locked by StateLock)
      SeekFinishedCond: PSDL_Cond;

      Loop: boolean; // (locked by StateLock)

      ParseThread: PSDL_Thread;
      PacketQueue: TPacketQueue;

      FormatInfo: TAudioFormatInfo;

      // FFmpeg specific data
      FormatCtx: PAVFormatContext;
      CodecCtx:  PAVCodecContext;
      Codec:     PAVCodec;

      AudioStreamIndex: integer;
      AudioStream: PAVStream;
      AudioStreamPos: double; // stream position in seconds (locked by DecoderLock)

      // decoder pause/resume data
      DecoderLocked:            boolean;
      DecoderPauseRequestCount: integer;
      DecoderUnlockedCond:      PSDL_Cond;
      DecoderResumeCond:        PSDL_Cond;

      // state-vars for DecodeFrame (locked by DecoderLock)
      AudioPaket:        TAVPacket;
      AudioPaketData:    PByteArray;
      AudioPaketSize:    integer;
      AudioPaketSilence: integer; // number of bytes of silence to return

      // state-vars for AudioCallback (locked by DecoderLock)
      AudioBufferPos:  integer;
      AudioBufferSize: integer;
      AudioBuffer:     PByteArray;

      Filename: IPath;

      procedure SetPositionIntern(Time: real; Flush: boolean; Blocking: boolean);
      procedure SetEOF(State: boolean);   {$IFDEF HasInline}inline;{$ENDIF}
      procedure SetError(State: boolean); {$IFDEF HasInline}inline;{$ENDIF}
      function IsSeeking(): boolean;
      function IsQuit(): boolean;

      procedure Reset();

      procedure Parse();
      function ParseLoop(): boolean;
      procedure PauseParser();
      procedure ResumeParser();

      function DecodeFrame(Buffer: PByteArray; BufferSize: integer): integer;
      procedure FlushCodecBuffers();
      procedure PauseDecoder();
      procedure ResumeDecoder();
    public
      constructor Create();
      destructor Destroy(); override;

      function Open(const Filename: IPath): boolean;
      procedure Close();                     override;

      function GetLength(): real;            override;
      function GetAudioFormatInfo(): TAudioFormatInfo; override;
      function GetPosition: real;            override;
      procedure SetPosition(Time: real);     override;
      function GetLoop(): boolean;           override;
      procedure SetLoop(Enabled: boolean);   override;
      function IsEOF(): boolean;             override;
      function IsError(): boolean;           override;

      function ReadData(Buffer: PByteArray; BufferSize: integer): integer; override;
  end;

type
  TAudioDecoder_FFmpeg = class(TInterfacedObject, IAudioDecoder)
    public
      function GetName: string;

      function InitializeDecoder(): boolean;
      function FinalizeDecoder(): boolean;
      function Open(const Filename: IPath): TAudioDecodeStream;
  end;

var
  FFmpegCore: TMediaCore_FFmpeg;

function ParseThreadMain(Data: Pointer): integer; cdecl; forward;


{ TFFmpegDecodeStream }

constructor TFFmpegDecodeStream.Create();
begin
  inherited Create();

  StateLock := SDL_CreateMutex();
  ParserUnlockedCond := SDL_CreateCond();
  ParserResumeCond := SDL_CreateCond();
  ParserIdleCond := SDL_CreateCond();
  SeekFinishedCond := SDL_CreateCond();
  DecoderUnlockedCond := SDL_CreateCond();
  DecoderResumeCond := SDL_CreateCond();

  // according to the documentation of avcodec_decode_audio(2), sample-data
  // should be aligned on a 16 byte boundary. Otherwise internal calls
  // (e.g. to SSE or Altivec operations) might fail or lack performance on some
  // CPUs. Although GetMem() in Delphi and FPC seems to use a 16 byte or higher
  // alignment for buffers of this size (alignment depends on the size of the
  // requested buffer), we will set the alignment explicitly as the minimum
  // alignment used by Delphi and FPC is on an 8 byte boundary.
  // 
  // Note: AudioBuffer was previously defined as a field of type TAudioBuffer
  // (array[0..AUDIO_BUFFER_SIZE-1] of byte) and hence statically allocated.
  // Fields of records are aligned different to memory allocated with GetMem(),
  // aligning depending on the type but will be at least 2 bytes.
  // AudioBuffer was not aligned to a 16 byte boundary. The {$ALIGN x} directive
  // was not applicable as Delphi in contrast to FPC provides at most 8 byte
  // alignment ({$ALIGN 16} is not supported) by this directive.
  AudioBuffer := GetAlignedMem(AUDIO_BUFFER_SIZE, 16);

  Reset();
end;

procedure TFFmpegDecodeStream.Reset();
begin
  ParseThread := nil;

  EOFState := false;
  ErrorState := false;
  Loop := false;
  QuitRequest := false;

  AudioPaketData := nil;
  AudioPaketSize := 0;
  AudioPaketSilence := 0;

  AudioBufferPos := 0;
  AudioBufferSize := 0;

  ParserLocked := false;
  ParserPauseRequestCount := 0;
  DecoderLocked := false;
  DecoderPauseRequestCount := 0;

  FillChar(AudioPaket, SizeOf(TAVPacket), 0);
end;

{*
 * Frees the decode-stream data.
 *}
destructor TFFmpegDecodeStream.Destroy();
begin
  Close();

  SDL_DestroyMutex(StateLock);
  SDL_DestroyCond(ParserUnlockedCond);
  SDL_DestroyCond(ParserResumeCond);
  SDL_DestroyCond(ParserIdleCond);
  SDL_DestroyCond(SeekFinishedCond);
  SDL_DestroyCond(DecoderUnlockedCond);
  SDL_DestroyCond(DecoderResumeCond);

  FreeAlignedMem(AudioBuffer);

  inherited;
end;

function TFFmpegDecodeStream.Open(const Filename: IPath): boolean;
var
  SampleFormat: TAudioSampleFormat;
  AVResult: integer;
begin
  Result := false;

  Close();
  Reset();

  if (not Filename.IsFile) then
  begin
    Log.LogError('Audio-file does not exist: "' + Filename.ToNative + '"', 'UAudio_FFmpeg');
    Exit;
  end;

  Self.Filename := Filename;

  // use custom 'ufile' protocol for UTF-8 support
  if (av_open_input_file(FormatCtx, PAnsiChar('ufile:'+FileName.ToUTF8), nil, 0, nil) <> 0) then
  begin
    Log.LogError('av_open_input_file failed: "' + Filename.ToNative + '"', 'UAudio_FFmpeg');
    Exit;
  end;

  // generate PTS values if they do not exist
  FormatCtx^.flags := FormatCtx^.flags or AVFMT_FLAG_GENPTS;

  // retrieve stream information
  if (av_find_stream_info(FormatCtx) < 0) then
  begin
    Log.LogError('av_find_stream_info failed: "' + Filename.ToNative + '"', 'UAudio_FFmpeg');
    Close();
    Exit;
  end;

  // FIXME: hack used by ffplay. Maybe should not use url_feof() to test for the end
  FormatCtx^.pb.eof_reached := 0;

  {$IFDEF DebugFFmpegDecode}
  dump_format(FormatCtx, 0, PAnsiChar(Filename.ToNative), 0);
  {$ENDIF}

  AudioStreamIndex := FFmpegCore.FindAudioStreamIndex(FormatCtx);
  if (AudioStreamIndex < 0) then
  begin
    Log.LogError('FindAudioStreamIndex: No Audio-stream found "' + Filename.ToNative + '"', 'UAudio_FFmpeg');
    Close();
    Exit;
  end;

  //Log.LogStatus('AudioStreamIndex is: '+ inttostr(ffmpegStreamID), 'UAudio_FFmpeg');

  AudioStream := FormatCtx.streams[AudioStreamIndex];
  AudioStreamPos := 0;
  CodecCtx := AudioStream^.codec;

  // TODO: should we use this or not? Should we allow 5.1 channel audio?
  (*
  {$IF LIBAVCODEC_VERSION >= 51042000}
  if (CodecCtx^.channels > 0) then
    CodecCtx^.request_channels := Min(2, CodecCtx^.channels)
  else
    CodecCtx^.request_channels := 2;
  {$IFEND}
  *)

  Codec := avcodec_find_decoder(CodecCtx^.codec_id);
  if (Codec = nil) then
  begin
    Log.LogError('Unsupported codec!', 'UAudio_FFmpeg');
    CodecCtx := nil;
    Close();
    Exit;
  end;

  // set debug options
  CodecCtx^.debug_mv := 0;
  CodecCtx^.debug := 0;

  // detect bug-workarounds automatically
  CodecCtx^.workaround_bugs := FF_BUG_AUTODETECT;
  // error resilience strategy (careful/compliant/agressive/very_aggressive)
  //CodecCtx^.error_resilience := FF_ER_CAREFUL; //FF_ER_COMPLIANT;
  // allow non spec compliant speedup tricks.
  //CodecCtx^.flags2 := CodecCtx^.flags2 or CODEC_FLAG2_FAST;

  // Note: avcodec_open() and avcodec_close() are not thread-safe and will
  // fail if called concurrently by different threads.
  FFmpegCore.LockAVCodec();
  try
    AVResult := avcodec_open(CodecCtx, Codec);
  finally
    FFmpegCore.UnlockAVCodec();
  end;
  if (AVResult < 0) then
  begin
    Log.LogError('avcodec_open failed!', 'UAudio_FFmpeg');
    Close();
    Exit;
  end;

  // now initialize the audio-format

  if (not FFmpegCore.ConvertFFmpegToAudioFormat(CodecCtx^.sample_fmt, SampleFormat)) then
  begin
    // try standard format
    SampleFormat := asfS16;
  end;
  if CodecCtx^.channels > 255 then
    Log.LogStatus('Error: CodecCtx^.channels > 255', 'TFFmpegDecodeStream.Open');
  FormatInfo := TAudioFormatInfo.Create(
    byte(CodecCtx^.channels),
    CodecCtx^.sample_rate,
    SampleFormat
  );

  PacketQueue := TPacketQueue.Create();

  // finally start the decode thread
  ParseThread := SDL_CreateThread(@ParseThreadMain, Self);

  Result := true;
end;

procedure TFFmpegDecodeStream.Close();
var
  ThreadResult: integer;
begin
  // wake threads waiting for packet-queue data
  // Note: normally, there are no waiting threads. If there were waiting
  // ones, they would block the audio-callback thread.
  if (assigned(PacketQueue)) then
    PacketQueue.Abort();

  // send quit request (to parse-thread etc)
  SDL_mutexP(StateLock);
  QuitRequest := true;
  SDL_CondBroadcast(ParserIdleCond);
  SDL_mutexV(StateLock);

  // abort parse-thread
  if (ParseThread <> nil) then
  begin
    // and wait until it terminates
    SDL_WaitThread(ParseThread, ThreadResult);
    ParseThread := nil;
  end;

  // Close the codec
  if (CodecCtx <> nil) then
  begin
    // avcodec_close() is not thread-safe
    FFmpegCore.LockAVCodec();
    try
      avcodec_close(CodecCtx);
    finally
      FFmpegCore.UnlockAVCodec();
    end;
    CodecCtx := nil;
  end;

  // Close the video file
  if (FormatCtx <> nil) then
  begin
    av_close_input_file(FormatCtx);
    FormatCtx := nil;
  end;

  PerformOnClose();
  
  FreeAndNil(PacketQueue);
  FreeAndNil(FormatInfo);
end;

function TFFmpegDecodeStream.GetLength(): real;
begin
  // do not forget to consider the start_time value here
  // there is a type size mismatch warnign because start_time and duration are cint64.
  // So, in principle there could be an overflow when doing the sum.
  Result := (FormatCtx^.start_time + FormatCtx^.duration) / AV_TIME_BASE;
end;

function TFFmpegDecodeStream.GetAudioFormatInfo(): TAudioFormatInfo;
begin
  Result := FormatInfo;
end;

function TFFmpegDecodeStream.IsEOF(): boolean;
begin
  SDL_mutexP(StateLock);
  Result := EOFState;
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.SetEOF(State: boolean);
begin
  SDL_mutexP(StateLock);
  EOFState := State;
  SDL_mutexV(StateLock);
end;

function TFFmpegDecodeStream.IsError(): boolean;
begin
  SDL_mutexP(StateLock);
  Result := ErrorState;
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.SetError(State: boolean);
begin
  SDL_mutexP(StateLock);
  ErrorState := State;
  SDL_mutexV(StateLock);
end;

function TFFmpegDecodeStream.IsSeeking(): boolean;
begin
  SDL_mutexP(StateLock);
  Result := SeekRequest;
  SDL_mutexV(StateLock);
end;

function TFFmpegDecodeStream.IsQuit(): boolean;
begin
  SDL_mutexP(StateLock);
  Result := QuitRequest;
  SDL_mutexV(StateLock);
end;

function TFFmpegDecodeStream.GetPosition(): real;
var
  BufferSizeSec: double;
begin
  PauseDecoder();

  // ReadData() does not return all of the buffer retrieved by DecodeFrame().
  // Determine the size of the unused part of the decode-buffer.
  BufferSizeSec := (AudioBufferSize - AudioBufferPos) /
                   FormatInfo.BytesPerSec;

  // subtract the size of unused buffer-data from the audio clock.
  Result := AudioStreamPos - BufferSizeSec;

  ResumeDecoder();
end;

procedure TFFmpegDecodeStream.SetPosition(Time: real);
begin
  SetPositionIntern(Time, true, true);
end;

function TFFmpegDecodeStream.GetLoop(): boolean;
begin
  SDL_mutexP(StateLock);
  Result := Loop;
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.SetLoop(Enabled: boolean);
begin
  SDL_mutexP(StateLock);
  Loop := Enabled;
  SDL_mutexV(StateLock);
end;


(********************************************
 * Parser section
 ********************************************)

procedure TFFmpegDecodeStream.PauseParser();
begin
  if (SDL_ThreadID() = ParseThread.threadid) then
    Exit;
    
  SDL_mutexP(StateLock);
  Inc(ParserPauseRequestCount);
  while (ParserLocked) do
    SDL_CondWait(ParserUnlockedCond, StateLock);
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.ResumeParser();
begin
  if (SDL_ThreadID() = ParseThread.threadid) then
    Exit;

  SDL_mutexP(StateLock);
  Dec(ParserPauseRequestCount);
  SDL_CondSignal(ParserResumeCond);
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.SetPositionIntern(Time: real; Flush: boolean; Blocking: boolean);
begin
  // - Pause the parser first to prevent it from putting obsolete packages
  //   into the queue after the queue was flushed and before seeking is done.
  //   Otherwise we will hear fragments of old data, if the stream was seeked
  //   in stopped mode and resumed afterwards (applies to non-blocking mode only).
  // - Pause the decoder to avoid race-condition that might occur otherwise.
  // - Last lock the state lock because we are manipulating some shared state-vars.
  PauseParser();
  PauseDecoder();
  SDL_mutexP(StateLock);
  try
    EOFState := false;
    ErrorState := false;

    // do not seek if we are already at the correct position.
    // This is important especially for seeking to position 0 if we already are
    // at the beginning. Although seeking with AVSEEK_FLAG_BACKWARD for pos 0 works,
    // it is still a bit choppy (although much better than w/o AVSEEK_FLAG_BACKWARD).
    if (Time = AudioStreamPos) then
      Exit;    

    // configure seek parameters
    SeekPos := Time;
    SeekFlush := Flush;
    SeekFlags := AVSEEK_FLAG_ANY;
    SeekRequest := true;

    // Note: the BACKWARD-flag seeks to the first position <= the position
    // searched for. Otherwise e.g. position 0 might not be seeked correct.
    // For some reason ffmpeg sometimes doesn't use position 0 but the key-frame
    // following. In streams with few key-frames (like many flv-files) the next
    // key-frame after 0 might be 5secs ahead.
    if (Time <= AudioStreamPos) then
      SeekFlags := SeekFlags or AVSEEK_FLAG_BACKWARD;

    // send a reuse signal in case the parser was stopped (e.g. because of an EOF)
    SDL_CondSignal(ParserIdleCond);
  finally
    SDL_mutexV(StateLock);
    ResumeDecoder();
    ResumeParser();
  end;

  // in blocking mode, wait until seeking is done
  if (Blocking) then
  begin
    SDL_mutexP(StateLock);
    while (SeekRequest) do
      SDL_CondWait(SeekFinishedCond, StateLock);
    SDL_mutexV(StateLock);
  end;
end;

function ParseThreadMain(Data: Pointer): integer; cdecl;
var
  Stream: TFFmpegDecodeStream;
begin
  Stream := TFFmpegDecodeStream(Data);
  if (Stream <> nil) then
    Stream.Parse();
  Result := 0;
end;

procedure TFFmpegDecodeStream.Parse();
begin
  // reuse thread as long as the stream is not terminated
  while (ParseLoop()) do
  begin
    // wait for reuse or destruction of stream
    SDL_mutexP(StateLock);
    while (not (SeekRequest or QuitRequest)) do
      SDL_CondWait(ParserIdleCond, StateLock);
    SDL_mutexV(StateLock);
  end;
end;

(**
 * Parser main loop.
 * Will not return until parsing of the stream is finished.
 * Reasons for the parser to return are:
 * - the end-of-file is reached
 * - an error occured
 * - the stream was quited (received a quit-request)
 * Returns true if the stream can be resumed or false if the stream has to
 * be terminated.
 *)
function TFFmpegDecodeStream.ParseLoop(): boolean;
var
  Packet: TAVPacket;
  SeekTarget: int64;
  ByteIOCtx: PByteIOContext;
  ErrorCode: integer;
  StartSilence: double;       // duration of silence at start of stream
  StartSilencePtr: PDouble;  // pointer for the EMPTY status packet 

  // Note: pthreads wakes threads waiting on a mutex in the order of their
  // priority and not in FIFO order. SDL does not provide any option to
  // control priorities. This might (and already did) starve threads waiting
  // on the mutex (e.g. SetPosition) making usdx look like it was froozen.
  // Instead of simply locking the critical section we set a ParserLocked flag
  // instead and give priority to the threads requesting the parser to pause.
  procedure LockParser();
  begin
    SDL_mutexP(StateLock);
    while (ParserPauseRequestCount > 0) do
      SDL_CondWait(ParserResumeCond, StateLock);
    ParserLocked := true;
    SDL_mutexV(StateLock);
  end;

  procedure UnlockParser();
  begin
    SDL_mutexP(StateLock);
    ParserLocked := false;
    SDL_CondBroadcast(ParserUnlockedCond);
    SDL_mutexV(StateLock);
  end;

begin
  Result := true;

  while (true) do
  begin
    LockParser();
    try

      if (IsQuit()) then
      begin
        Result := false;
        Exit;
      end;

      // handle seek-request (Note: no need to lock SeekRequest here)
      if (SeekRequest) then
      begin
        // first try: seek on the audio stream
        SeekTarget := Round(SeekPos / av_q2d(AudioStream^.time_base));
        StartSilence := 0;
        if (SeekTarget < AudioStream^.start_time) then
          StartSilence := (AudioStream^.start_time - SeekTarget) * av_q2d(AudioStream^.time_base);
        ErrorCode := av_seek_frame(FormatCtx, AudioStreamIndex, SeekTarget, SeekFlags);

        if (ErrorCode < 0) then
        begin
          // second try: seek on the default stream (necessary for flv-videos and some ogg-files)
          SeekTarget := Round(SeekPos * AV_TIME_BASE);
          StartSilence := 0;
          if (SeekTarget < FormatCtx^.start_time) then
            StartSilence := (FormatCtx^.start_time - SeekTarget) / AV_TIME_BASE;
          ErrorCode := av_seek_frame(FormatCtx, -1, SeekTarget, SeekFlags);
        end;

        // pause decoder and lock state (keep the lock-order to avoid deadlocks).
        // Note that the decoder does not block in the packet-queue in seeking state,
        // so locking the decoder here does not cause a dead-lock.
        PauseDecoder();
        SDL_mutexP(StateLock);
        try
          if (ErrorCode < 0) then
          begin
            // seeking failed
            ErrorState := true;
            Log.LogStatus('Seek Error in "'+FormatCtx^.filename+'"', 'UAudioDecoder_FFmpeg');
          end
          else
          begin
            if (SeekFlush) then
            begin
              // flush queue (we will send a Flush-Packet when seeking is finished)
              PacketQueue.Flush();

              // flush the decode buffers
              AudioBufferSize := 0;
              AudioBufferPos := 0;
              AudioPaketSize := 0;
              AudioPaketSilence := 0;
              FlushCodecBuffers();
              
              // Set preliminary stream position. The position will be set to
              // the correct value as soon as the first packet is decoded.
              AudioStreamPos := SeekPos;
            end
            else
            begin
              // request avcodec buffer flush
              PacketQueue.PutStatus(PKT_STATUS_FLAG_FLUSH, nil);
            end;

            // fill the gap between position 0 and start_time with silence
            // but not if we are in loop mode
            if ((StartSilence > 0) and (not Loop)) then
            begin
              GetMem(StartSilencePtr, SizeOf(StartSilence));
              StartSilencePtr^ := StartSilence;
              PacketQueue.PutStatus(PKT_STATUS_FLAG_EMPTY, StartSilencePtr);
            end;
          end;

          SeekRequest := false;
          SDL_CondBroadcast(SeekFinishedCond);
        finally
          SDL_mutexV(StateLock);
          ResumeDecoder();
        end;
      end;

      if (PacketQueue.GetSize() > MAX_AUDIOQ_SIZE) then
      begin
        SDL_Delay(10);
        Continue;
      end;

      if (av_read_frame(FormatCtx, Packet) < 0) then
      begin
        // failed to read a frame, check reason
        {$IF (LIBAVFORMAT_VERSION_MAJOR >= 52)}
        ByteIOCtx := FormatCtx^.pb;
        {$ELSE}
        ByteIOCtx := @FormatCtx^.pb;
        {$IFEND}

        // check for end-of-file (eof is not an error)
        if (url_feof(ByteIOCtx) <> 0) then
        begin
          if (GetLoop()) then
          begin
            // rewind stream (but do not flush)
            SetPositionIntern(0, false, false);
            Continue;
          end
          else
          begin
            // signal end-of-file
            PacketQueue.PutStatus(PKT_STATUS_FLAG_EOF, nil);
            Exit;
          end;
        end;

        // check for errors
        if (url_ferror(ByteIOCtx) <> 0) then
        begin
          // an error occured -> abort and wait for repositioning or termination
          PacketQueue.PutStatus(PKT_STATUS_FLAG_ERROR, nil);
          Exit;
        end;

        // no error -> wait for user input
        SDL_Delay(100);
        Continue;
      end;

      if (Packet.stream_index = AudioStreamIndex) then
        PacketQueue.Put(@Packet)
      else
        av_free_packet(@Packet);

    finally
      UnlockParser();
    end;
  end;
end;


(********************************************
 * Decoder section
 ********************************************)

procedure TFFmpegDecodeStream.PauseDecoder();
begin
  SDL_mutexP(StateLock);
  Inc(DecoderPauseRequestCount);
  while (DecoderLocked) do
    SDL_CondWait(DecoderUnlockedCond, StateLock);
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.ResumeDecoder();
begin
  SDL_mutexP(StateLock);
  Dec(DecoderPauseRequestCount);
  SDL_CondSignal(DecoderResumeCond);
  SDL_mutexV(StateLock);
end;

procedure TFFmpegDecodeStream.FlushCodecBuffers();
begin
  // if no flush operation is specified, avcodec_flush_buffers will not do anything.
  if (@CodecCtx.codec.flush <> nil) then
  begin
    // flush buffers used by avcodec_decode_audio, etc.
    avcodec_flush_buffers(CodecCtx);
  end
  else
  begin
    // we need a Workaround to avoid plopping noise with ogg-vorbis and
    // mp3 (in older versions of FFmpeg).
    // We will just reopen the codec.
    FFmpegCore.LockAVCodec();
    try
      avcodec_close(CodecCtx);
      avcodec_open(CodecCtx, Codec);
    finally
      FFmpegCore.UnlockAVCodec();
    end;
  end;
end;

function TFFmpegDecodeStream.DecodeFrame(Buffer: PByteArray; BufferSize: integer): integer;
var
  PaketDecodedSize: integer; // size of packet data used for decoding
  DataSize: integer;         // size of output data decoded by FFmpeg
  BlockQueue: boolean;
  SilenceDuration: double;
  {$IFDEF DebugFFmpegDecode}
  TmpPos: double;
  {$ENDIF}
begin
  Result := -1;

  if (EOF) then
    Exit;

  while(true) do
  begin
    // for titles with start_time > 0 we have to generate silence
    // until we reach the pts of the first data packet.
    if (AudioPaketSilence > 0) then
    begin
      DataSize := Min(AudioPaketSilence, BufferSize);
      FillChar(Buffer[0], DataSize, 0);
      Dec(AudioPaketSilence, DataSize);
      AudioStreamPos := AudioStreamPos + DataSize / FormatInfo.BytesPerSec; 
      Result := DataSize;
      Exit;
    end;

    // read packet data
    while (AudioPaketSize > 0) do
    begin
      DataSize := BufferSize;

      {$IF LIBAVCODEC_VERSION >= 51030000} // 51.30.0
      PaketDecodedSize := avcodec_decode_audio2(CodecCtx, PSmallint(Buffer),
                  DataSize, AudioPaketData, AudioPaketSize);
      {$ELSE}
      PaketDecodedSize := avcodec_decode_audio(CodecCtx, PSmallint(Buffer),
                  DataSize, AudioPaketData, AudioPaketSize);
      {$IFEND}

      if(PaketDecodedSize < 0) then
      begin
        // if error, skip frame
        {$IFDEF DebugFFmpegDecode}
        DebugWriteln('Skip audio frame');
        {$ENDIF}
        AudioPaketSize := 0;
        Break;
      end;

      Inc(AudioPaketData, PaketDecodedSize);
      Dec(AudioPaketSize, PaketDecodedSize);

      // check if avcodec_decode_audio returned data, otherwise fetch more frames
      if (DataSize <= 0) then
        Continue;

      // update stream position by the amount of fetched data
      AudioStreamPos := AudioStreamPos + DataSize / FormatInfo.BytesPerSec;
      
      // we have data, return it and come back for more later
      Result := DataSize;
      Exit;
    end;

    // free old packet data
    if (AudioPaket.data <> nil) then
      av_free_packet(@AudioPaket);

    // do not block queue on seeking (to avoid deadlocks on the DecoderLock)
    if (IsSeeking()) then
      BlockQueue := false
    else
      BlockQueue := true;

    // request a new packet and block if none available.
    // If this fails, the queue was aborted.
    if (PacketQueue.Get(AudioPaket, BlockQueue) <= 0) then
      Exit;

    // handle Status-packet
    if (PAnsiChar(AudioPaket.data) = STATUS_PACKET) then
    begin
      AudioPaket.data := nil;
      AudioPaketData := nil;
      AudioPaketSize := 0;

      case (AudioPaket.flags) of
        PKT_STATUS_FLAG_FLUSH:
        begin
          // just used if SetPositionIntern was called without the flush flag.
          FlushCodecBuffers;
        end;
        PKT_STATUS_FLAG_EOF: // end-of-file
        begin
          // ignore EOF while seeking
          if (not IsSeeking()) then
            SetEOF(true);
          // buffer contains no data -> result = -1
          Exit;
        end;
        PKT_STATUS_FLAG_ERROR:
        begin
          SetError(true);
          Log.LogStatus('I/O Error', 'TFFmpegDecodeStream.DecodeFrame');
          Exit;
        end;
        PKT_STATUS_FLAG_EMPTY:
        begin
          SilenceDuration := PDouble(PacketQueue.GetStatusInfo(AudioPaket))^;
          AudioPaketSilence := Round(SilenceDuration * FormatInfo.SampleRate) * FormatInfo.FrameSize;
          PacketQueue.FreeStatusInfo(AudioPaket);
        end
        else
        begin
          Log.LogStatus('Unknown status', 'TFFmpegDecodeStream.DecodeFrame');
        end;
      end;

      Continue;
    end;

    AudioPaketData := AudioPaket.data;
    AudioPaketSize := AudioPaket.size;

    // if available, update the stream position to the presentation time of this package
    if(AudioPaket.pts <> AV_NOPTS_VALUE) then
    begin
      {$IFDEF DebugFFmpegDecode}
      TmpPos := AudioStreamPos;
      {$ENDIF}
      AudioStreamPos := av_q2d(AudioStream^.time_base) * AudioPaket.pts;
      {$IFDEF DebugFFmpegDecode}
      DebugWriteln('Timestamp: ' + floattostrf(AudioStreamPos, ffFixed, 15, 3) + ' ' +
                   '(Calc: ' + floattostrf(TmpPos, ffFixed, 15, 3) + '), ' +
                   'Diff: ' + floattostrf(AudioStreamPos-TmpPos, ffFixed, 15, 3));
      {$ENDIF}
    end;
  end;
end;

function TFFmpegDecodeStream.ReadData(Buffer: PByteArray; BufferSize: integer): integer;
var
  CopyByteCount:   integer; // number of bytes to copy
  RemainByteCount: integer; // number of bytes left (remain) to read
  BufferPos: integer;

  // prioritize pause requests
  procedure LockDecoder();
  begin
    SDL_mutexP(StateLock);
    while (DecoderPauseRequestCount > 0) do
      SDL_CondWait(DecoderResumeCond, StateLock);
    DecoderLocked := true;
    SDL_mutexV(StateLock);
  end;

  procedure UnlockDecoder();
  begin
    SDL_mutexP(StateLock);
    DecoderLocked := false;
    SDL_CondBroadcast(DecoderUnlockedCond);
    SDL_mutexV(StateLock);
  end;

begin
  Result := -1;

  // set number of bytes to copy to the output buffer
  BufferPos := 0;

  LockDecoder();
  try
    // leave if end-of-file is reached
    if (EOF) then
      Exit;

    // copy data to output buffer
    while (BufferPos < BufferSize) do
    begin
      // check if we need more data
      if (AudioBufferPos >= AudioBufferSize) then
      begin
        AudioBufferPos := 0;

        // we have already sent all our data; get more
        AudioBufferSize := DecodeFrame(AudioBuffer, AUDIO_BUFFER_SIZE);

        // check for errors or EOF
        if(AudioBufferSize < 0) then
        begin
          Result := BufferPos;
          Exit;
        end;
      end;

      // calc number of new bytes in the decode-buffer
      CopyByteCount := AudioBufferSize - AudioBufferPos;
      // resize copy-count if more bytes available than needed (remaining bytes are used the next time)
      RemainByteCount := BufferSize - BufferPos;
      if (CopyByteCount > RemainByteCount) then
        CopyByteCount := RemainByteCount;

      Move(AudioBuffer[AudioBufferPos], Buffer[BufferPos], CopyByteCount);

      Inc(BufferPos,      CopyByteCount);
      Inc(AudioBufferPos, CopyByteCount);
    end;
  finally
    UnlockDecoder();
  end;

  Result := BufferSize;
end;


{ TAudioDecoder_FFmpeg }

function TAudioDecoder_FFmpeg.GetName: String;
begin
  Result := 'FFmpeg_Decoder';
end;

function TAudioDecoder_FFmpeg.InitializeDecoder: boolean;
begin
  //Log.LogStatus('InitializeDecoder', 'UAudioDecoder_FFmpeg');
  FFmpegCore := TMediaCore_FFmpeg.GetInstance();
  av_register_all();

  // Do not show uninformative error messages by default.
  // FFmpeg prints all error-infos on the console by default what
  // is very confusing as the playback of the files is correct.
  // We consider these errors to be internal to FFMpeg. They can be fixed
  // by the FFmpeg guys only and do not provide any useful information in
  // respect to USDX.
  {$IFNDEF EnableFFmpegErrorOutput}
    {$IF LIBAVUTIL_VERSION_MAJOR >= 50}
    av_log_set_level(AV_LOG_FATAL);
    {$ELSE}
    // FATAL and ERROR share one log-level, so we have to use QUIET
    av_log_set_level(AV_LOG_QUIET);
    {$IFEND}
  {$ENDIF}

  Result := true;
end;

function TAudioDecoder_FFmpeg.FinalizeDecoder(): boolean;
begin
  Result := true;
end;

function TAudioDecoder_FFmpeg.Open(const Filename: IPath): TAudioDecodeStream;
var
  Stream: TFFmpegDecodeStream;
begin
  Result := nil;

  Stream := TFFmpegDecodeStream.Create();
  if (not Stream.Open(Filename)) then
  begin
    Stream.Free;
    Exit;
  end;

  Result := Stream;
end;


initialization
  MediaManager.Add(TAudioDecoder_FFmpeg.Create);

end.