aboutsummaryrefslogblamecommitdiffstats
path: root/cmake/src/media/UVideo.pas
blob: 35f8ab4dd415dc89f1f0d139b79e3b30a8c7d0e6 (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

























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                                                              
{* 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 UVideo;

{*
 * based on 'An ffmpeg and SDL Tutorial' (http://www.dranger.com/ffmpeg/)
 *}

// uncomment if you want to see the debug stuff
{.$define DebugDisplay}
{.$define DebugFrames}
{.$define VideoBenchmark}
{.$define Info}

interface

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

{$I switches.inc}

// use BGR-format for accelerated colorspace conversion with swscale
{$IFDEF UseSWScale}
  {$DEFINE PIXEL_FMT_BGR}
{$ENDIF}

type
  {**
   * vacStretch: Stretch to screen width and height
   *   - ignores aspect
   *   + no borders
   *   + no image data loss
   * vacCrop: Stretch to screen width or height, crop the other dimension
   *   + keeps aspect
   *   + no borders
   *   - frame borders are cropped (image data loss)
   * vacLetterBox: Stretch to screen width, add bars at or crop top and bottom
   *   + keeps aspect
   *   - borders at top and bottom
   *   o top/bottom is cropped if width < height (unusual)
   *}
  TAspectCorrection = (acoStretch, acoCrop, acoLetterBox);


implementation

uses
  SDL,
  textgl,
  avcodec,
  avformat,
  avutil,
  avio,
  rational,
  {$IFDEF UseSWScale}
  swscale,
  {$ENDIF}
  UMediaCore_FFmpeg,
  math,
  gl,
  glext,
  SysUtils,
  UCommon,
  UConfig,
  ULog,
  UMusic,
  UGraphicClasses,
  UGraphic;

const
{$IFDEF PIXEL_FMT_BGR}
  PIXEL_FMT_OPENGL = GL_BGR;
  PIXEL_FMT_FFMPEG = PIX_FMT_BGR24;
{$ELSE}
  PIXEL_FMT_OPENGL = GL_RGB;
  PIXEL_FMT_FFMPEG = PIX_FMT_RGB24;
{$ENDIF}

type
  TRectCoords = record
    Left, Right:  double;
    Upper, Lower: double;
  end;

  TVideoPlayback_FFmpeg = class( TInterfacedObject, IVideoPlayback )
  private
    fOpened: boolean;     //**< stream successfully opened
    fPaused: boolean;     //**< stream paused
    fInitialized: boolean;
    fEOF: boolean;        //**< end-of-file state

    fLoop: boolean;       //**< looping enabled

    fStream:        PAVStream;
    fStreamIndex :  integer;
    fFormatContext: PAVFormatContext;
    fCodecContext:  PAVCodecContext;
    fCodec:         PAVCodec;

    fAVFrame:     PAVFrame;
    fAVFrameRGB:  PAVFrame;

    fFrameBuffer: PByte;  //**< stores a FFmpeg video frame
    fFrameTex:    GLuint; //**< OpenGL texture for FrameBuffer
    fFrameTexValid: boolean; //**< if true, fFrameTex contains the current frame
    fTexWidth, fTexHeight: cardinal;

    {$IFDEF UseSWScale}
    fSwScaleContext: PSwsContext;
    {$ENDIF}

    fAspect: real;        //**< width/height ratio
    fAspectCorrection: TAspectCorrection;
    
    fTimeBase: extended;  //**< FFmpeg time base per time unit
    fTime:     extended;  //**< video time position (absolute)
    fLoopTime: extended;  //**< start time of the current loop

    procedure Reset();
    function DecodeFrame(): boolean;
    procedure SynchronizeTime(Frame: PAVFrame; var pts: double);

    procedure GetVideoRect(var ScreenRect, TexRect: TRectCoords);
    
    procedure ShowDebugInfo();

  public
    function    GetName: String;

    function    Init(): boolean;
    function    Finalize: boolean;

    function    Open(const aFileName : string): boolean; // true if succeed
    procedure   Close;

    procedure   Play;
    procedure   Pause;
    procedure   Stop;

    procedure   SetPosition(Time: real);
    function    GetPosition: real;

    procedure   GetFrame(Time: Extended);
    procedure   DrawGL(Screen: integer);
  end;

var
  FFmpegCore: TMediaCore_FFmpeg;

  
// These are called whenever we allocate a frame buffer.
// We use this to store the global_pts in a frame at the time it is allocated.
function PtsGetBuffer(CodecCtx: PAVCodecContext; Frame: PAVFrame): integer; cdecl;
var
  pts: Pint64;
  VideoPktPts: Pint64;
begin
  Result := avcodec_default_get_buffer(CodecCtx, Frame);
  VideoPktPts := CodecCtx^.opaque;
  if (VideoPktPts <> nil) then
  begin
    // Note: we must copy the pts instead of passing a pointer, because the packet
    // (and with it the pts) might change before a frame is returned by av_decode_video.
    pts := av_malloc(sizeof(int64));
    pts^ := VideoPktPts^;
    Frame^.opaque := pts;
  end;
end;

procedure PtsReleaseBuffer(CodecCtx: PAVCodecContext; Frame: PAVFrame); cdecl;
begin
  if (Frame <> nil) then
    av_freep(@Frame^.opaque);
  avcodec_default_release_buffer(CodecCtx, Frame);
end;


{*------------------------------------------------------------------------------
 * TVideoPlayback_ffmpeg
 *------------------------------------------------------------------------------}

function  TVideoPlayback_FFmpeg.GetName: String;
begin
  result := 'FFmpeg_Video';
end;

function TVideoPlayback_FFmpeg.Init(): boolean;
begin
  Result := true;

  if (fInitialized) then
    Exit;
  fInitialized := true;

  FFmpegCore := TMediaCore_FFmpeg.GetInstance();

  Reset();
  av_register_all();
  glGenTextures(1, PGLuint(@fFrameTex));
end;

function TVideoPlayback_FFmpeg.Finalize(): boolean;
begin
  Close();
  glDeleteTextures(1, PGLuint(@fFrameTex));
  Result := true;
end;

procedure TVideoPlayback_FFmpeg.Reset();
begin
  // close previously opened video
  Close();

  fOpened       := False;
  fPaused       := False;
  fTimeBase      := 0;
  fTime          := 0;
  fStream := nil;
  fStreamIndex := -1;
  fFrameTexValid := false;

  fEOF := false;

  // TODO: do we really want this by default?
  fLoop := true;
  fLoopTime := 0;
  
  fAspectCorrection := acoCrop;
end;

function TVideoPlayback_FFmpeg.Open(const aFileName : string): boolean; // true if succeed
var
  errnum: Integer;
  AudioStreamIndex: integer;
begin
  Result := false;

  Reset();

  errnum := av_open_input_file(fFormatContext, PChar(aFileName), nil, 0, nil);
  if (errnum <> 0) then
  begin
    Log.LogError('Failed to open file "'+aFileName+'" ('+FFmpegCore.GetErrorString(errnum)+')');
    Exit;
  end;

  // update video info
  if (av_find_stream_info(fFormatContext) < 0) then
  begin
    Log.LogError('No stream info found', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;
  Log.LogInfo('VideoStreamIndex : ' + inttostr(fStreamIndex), 'TVideoPlayback_ffmpeg.Open');

  // find video stream
  FFmpegCore.FindStreamIDs(fFormatContext, fStreamIndex, AudioStreamIndex);
  if (fStreamIndex < 0) then
  begin
    Log.LogError('No video stream found', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;

  fStream := fFormatContext^.streams[fStreamIndex];
  fCodecContext := fStream^.codec;

  fCodec := avcodec_find_decoder(fCodecContext^.codec_id);
  if (fCodec = nil) then
  begin
    Log.LogError('No matching codec found', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;

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

  // detect bug-workarounds automatically
  fCodecContext^.workaround_bugs := FF_BUG_AUTODETECT;
  // error resilience strategy (careful/compliant/agressive/very_aggressive)
  //fCodecContext^.error_resilience := FF_ER_CAREFUL; //FF_ER_COMPLIANT;
  // allow non spec compliant speedup tricks.
  //fCodecContext^.flags2 := fCodecContext^.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
    errnum := avcodec_open(fCodecContext, fCodec);
  finally
    FFmpegCore.UnlockAVCodec();
  end;
  if (errnum < 0) then
  begin
    Log.LogError('No matching codec found', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;

  // register custom callbacks for pts-determination
  fCodecContext^.get_buffer := PtsGetBuffer;
  fCodecContext^.release_buffer := PtsReleaseBuffer;

  {$ifdef DebugDisplay}
  DebugWriteln('Found a matching Codec: '+ fCodecContext^.Codec.Name + sLineBreak +
    sLineBreak +
    '  Width = '+inttostr(fCodecContext^.width) +
    ', Height='+inttostr(fCodecContext^.height) + sLineBreak +
    '  Aspect    : '+inttostr(fCodecContext^.sample_aspect_ratio.num) + '/' +
                     inttostr(fCodecContext^.sample_aspect_ratio.den) + sLineBreak +
    '  Framerate : '+inttostr(fCodecContext^.time_base.num) + '/' +
                     inttostr(fCodecContext^.time_base.den));
  {$endif}

  // allocate space for decoded frame and rgb frame
  fAVFrame := avcodec_alloc_frame();
  fAVFrameRGB := avcodec_alloc_frame();
  fFrameBuffer := av_malloc(avpicture_get_size(PIXEL_FMT_FFMPEG,
      fCodecContext^.width, fCodecContext^.height));

  if ((fAVFrame = nil) or (fAVFrameRGB = nil) or (fFrameBuffer = nil)) then
  begin
    Log.LogError('Failed to allocate buffers', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;

  // TODO: pad data for OpenGL to GL_UNPACK_ALIGNMENT
  // (otherwise video will be distorted if width/height is not a multiple of the alignment)
  errnum := avpicture_fill(PAVPicture(fAVFrameRGB), fFrameBuffer, PIXEL_FMT_FFMPEG,
      fCodecContext^.width, fCodecContext^.height);
  if (errnum < 0) then
  begin
    Log.LogError('avpicture_fill failed: ' + FFmpegCore.GetErrorString(errnum), 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;

  // calculate some information for video display
  fAspect := av_q2d(fCodecContext^.sample_aspect_ratio);
  if (fAspect = 0) then
    fAspect := fCodecContext^.width /
               fCodecContext^.height
  else
    fAspect := fAspect * fCodecContext^.width /
                         fCodecContext^.height;

  fTimeBase := 1/av_q2d(fStream^.r_frame_rate);

  // hack to get reasonable timebase (for divx and others)
  if (fTimeBase < 0.02) then // 0.02 <-> 50 fps
  begin
    fTimeBase := av_q2d(fStream^.r_frame_rate);
    while (fTimeBase > 50) do
      fTimeBase := fTimeBase/10;
    fTimeBase := 1/fTimeBase;
  end;

  Log.LogInfo('VideoTimeBase: ' + floattostr(fTimeBase), 'TVideoPlayback_ffmpeg.Open');
  Log.LogInfo('Framerate: '+inttostr(floor(1/fTimeBase))+'fps', 'TVideoPlayback_ffmpeg.Open');

  {$IFDEF UseSWScale}
  // if available get a SWScale-context -> faster than the deprecated img_convert().
  // SWScale has accelerated support for PIX_FMT_RGB32/PIX_FMT_BGR24/PIX_FMT_BGR565/PIX_FMT_BGR555.
  // Note: PIX_FMT_RGB32 is a BGR- and not an RGB-format (maybe a bug)!!!
  // The BGR565-formats (GL_UNSIGNED_SHORT_5_6_5) is way too slow because of its
  // bad OpenGL support. The BGR formats have MMX(2) implementations but no speed-up
  // could be observed in comparison to the RGB versions.
  fSwScaleContext := sws_getContext(
      fCodecContext^.width, fCodecContext^.height,
      fCodecContext^.pix_fmt,
      fCodecContext^.width, fCodecContext^.height,
      PIXEL_FMT_FFMPEG,
      SWS_FAST_BILINEAR, nil, nil, nil);
  if (fSwScaleContext = nil) then
  begin
    Log.LogError('Failed to get swscale context', 'TVideoPlayback_ffmpeg.Open');
    Close();
    Exit;
  end;
  {$ENDIF}

  fTexWidth   := Round(Power(2, Ceil(Log2(fCodecContext^.width))));
  fTexHeight  := Round(Power(2, Ceil(Log2(fCodecContext^.height))));

  // we retrieve a texture just once with glTexImage2D and update it with glTexSubImage2D later.
  // Benefits: glTexSubImage2D is faster and supports non-power-of-two widths/height.
  glBindTexture(GL_TEXTURE_2D, fFrameTex);
  glTexEnvi(GL_TEXTURE_2D, GL_TEXTURE_ENV_MODE, GL_REPLACE);
  glTexImage2D(GL_TEXTURE_2D, 0, 3, fTexWidth, fTexHeight, 0,
      PIXEL_FMT_OPENGL, GL_UNSIGNED_BYTE, nil);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

  fOpened := True;
  Result := true;
end;

procedure TVideoPlayback_FFmpeg.Close;
begin
  if (fFrameBuffer <> nil) then
    av_free(fFrameBuffer);
  if (fAVFrameRGB <> nil) then
    av_free(fAVFrameRGB);
  if (fAVFrame <> nil) then
    av_free(fAVFrame);

  fAVFrame     := nil;
  fAVFrameRGB  := nil;
  fFrameBuffer := nil;
    
  if (fCodecContext <> nil) then
  begin
    // avcodec_close() is not thread-safe
    FFmpegCore.LockAVCodec();
    try
      avcodec_close(fCodecContext);
    finally
      FFmpegCore.UnlockAVCodec();
    end;
  end;

  if (fFormatContext <> nil) then
    av_close_input_file(fFormatContext);

  fCodecContext  := nil;
  fFormatContext := nil;

  fOpened := False;
end;

procedure TVideoPlayback_FFmpeg.SynchronizeTime(Frame: PAVFrame; var pts: double);
var
  FrameDelay: double;
begin
  if (pts <> 0) then
  begin
    // if we have pts, set video clock to it
    fTime := pts;
  end else
  begin
    // if we aren't given a pts, set it to the clock
    pts := fTime;
  end;
  // update the video clock
  FrameDelay := av_q2d(fCodecContext^.time_base);
  // if we are repeating a frame, adjust clock accordingly
  FrameDelay := FrameDelay + Frame^.repeat_pict * (FrameDelay * 0.5);
  fTime := fTime + FrameDelay;
end;

{**
 * Decode a new frame from the video stream.
 * The decoded frame is stored in fAVFrame. fTime is updated to the new frame's
 * time.
 * @param pts will be updated to the presentation time of the decoded frame. 
 * returns true if a frame could be decoded. False if an error or EOF occured.
 *}
function TVideoPlayback_FFmpeg.DecodeFrame(): boolean;
var
  FrameFinished: Integer;
  VideoPktPts: int64;
  pbIOCtx: PByteIOContext;
  errnum: integer;
  AVPacket: TAVPacket;
  pts: double;
begin
  Result := false;
  FrameFinished := 0;

  if fEOF then
    Exit;

  // read packets until we have a finished frame (or there are no more packets)
  while (FrameFinished = 0) do
  begin
    errnum := av_read_frame(fFormatContext, AVPacket);
    if (errnum < 0) then
    begin
      // failed to read a frame, check reason

      {$IF (LIBAVFORMAT_VERSION_MAJOR >= 52)}
      pbIOCtx := fFormatContext^.pb;
      {$ELSE}
      pbIOCtx := @fFormatContext^.pb;
      {$IFEND}

      // check for end-of-file (EOF is not an error)
      if (url_feof(pbIOCtx) <> 0) then
      begin
        fEOF := true;
        Exit;
      end;

      // check for errors
      if (url_ferror(pbIOCtx) <> 0) then
        Exit;

      // url_feof() does not detect an EOF for some mov-files (e.g. deluxe.mov)
      // so we have to do it this way.
      if ((fFormatContext^.file_size <> 0) and
          (pbIOCtx^.pos >= fFormatContext^.file_size)) then
      begin
        fEOF := true;
        Exit;
      end;

      // no error -> wait for user input
{
      SDL_Delay(100);  // initial version, left for documentation
      continue;
}

      // Patch by Hawkear:
      // Why should this function loop in an endless loop if there is an error?
      // This runs in the main thread, so it halts the whole program
      // Therefore, it is better to exit when an error occurs
      Exit;

    end;

    // if we got a packet from the video stream, then decode it
    if (AVPacket.stream_index = fStreamIndex) then
    begin
      // save pts to be stored in pFrame in first call of PtsGetBuffer()
      VideoPktPts := AVPacket.pts;
      fCodecContext^.opaque := @VideoPktPts;

      // decode packet
      avcodec_decode_video(fCodecContext, fAVFrame,
          frameFinished, AVPacket.data, AVPacket.size);

      // reset opaque data
      fCodecContext^.opaque := nil;

      // update pts
      if (AVPacket.dts <> AV_NOPTS_VALUE) then
      begin
        pts := AVPacket.dts;
      end
      else if ((fAVFrame^.opaque <> nil) and
               (Pint64(fAVFrame^.opaque)^ <> AV_NOPTS_VALUE)) then
      begin
        pts := Pint64(fAVFrame^.opaque)^;
      end
      else
      begin
        pts := 0;
      end;
      pts := pts * av_q2d(fStream^.time_base);

      // synchronize time on each complete frame
      if (frameFinished <> 0) then
        SynchronizeTime(fAVFrame, pts);
    end;

    // free the packet from av_read_frame
    av_free_packet( @AVPacket );
  end;

  Result := true;
end;

procedure TVideoPlayback_FFmpeg.GetFrame(Time: Extended);
var
  errnum: Integer;
  NewTime: Extended;
  TimeDifference: Extended;
  DropFrameCount: Integer;
  i: Integer;
  Success: boolean;
const
  FRAME_DROPCOUNT = 3;
begin
  if not fOpened then
    Exit;

  if fPaused then
    Exit;

  // requested stream position (relative to the last loop's start)
  NewTime := Time - fLoopTime;

  // check if current texture still contains the active frame
  if (fFrameTexValid) then
  begin
    // time since the last frame was returned
    TimeDifference := NewTime - fTime;

    {$IFDEF DebugDisplay}
    DebugWriteln('Time:      '+inttostr(floor(Time*1000)) + sLineBreak +
                 'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
                 'TimeBase:  '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
                 'TimeDiff:  '+inttostr(floor(TimeDifference*1000)));
    {$endif}

    // check if last time is more than one frame in the past 
    if (TimeDifference < fTimeBase) then
    begin
      {$ifdef DebugFrames}
      // frame delay debug display
      GoldenRec.Spawn(200,15,1,16,0,-1,ColoredStar,$00ff00);
      {$endif}

      {$IFDEF DebugDisplay}
      DebugWriteln('not getting new frame' + sLineBreak +
          'Time:      '+inttostr(floor(Time*1000)) + sLineBreak +
          'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
          'TimeBase:  '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
          'TimeDiff:  '+inttostr(floor(TimeDifference*1000)));
      {$endif}

      // we do not need a new frame now
      Exit;
    end;
  end;

  {$IFDEF VideoBenchmark}
  Log.BenchmarkStart(15);
  {$ENDIF}
  
  // fetch new frame (updates fTime)
  Success := DecodeFrame();
  TimeDifference := NewTime - fTime;

  // check if we have to skip frames
  if (TimeDifference >= FRAME_DROPCOUNT*fTimeBase) then
  begin
    {$IFDEF DebugFrames}
    //frame drop debug display
    GoldenRec.Spawn(200,55,1,16,0,-1,ColoredStar,$ff0000);
    {$ENDIF}
    {$IFDEF DebugDisplay}
    DebugWriteln('skipping frames' + sLineBreak +
        'TimeBase:  '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
        'TimeDiff:  '+inttostr(floor(TimeDifference*1000)));
    {$endif}

    // update video-time
    DropFrameCount := Trunc(TimeDifference / fTimeBase);
    fTime := fTime + DropFrameCount*fTimeBase;

    // skip half of the frames, this is much smoother than to skip all at once
    for i := 1 to DropFrameCount (*div 2*) do
      Success := DecodeFrame();
  end;

  // check if we got an EOF or error 
  if (not Success) then
  begin
    if fLoop then
    begin
      // we have to loop, so rewind
      SetPosition(0);
      // record the start-time of the current loop, so we can
      // determine the position in the stream (fTime-fLoopTime) later.
      fLoopTime := Time;
    end;
    Exit;
  end;

  // TODO: support for pan&scan
  //if (fAVFrame.pan_scan <> nil) then
  //begin
  //  Writeln(Format('PanScan: %d/%d', [fAVFrame.pan_scan.width, fAVFrame.pan_scan.height]));
  //end;

  // otherwise we convert the pixeldata from YUV to RGB
  {$IFDEF UseSWScale}
  errnum := sws_scale(fSwScaleContext, @(fAVFrame.data), @(fAVFrame.linesize),
          0, fCodecContext^.Height,
          @(fAVFrameRGB.data), @(fAVFrameRGB.linesize));
  {$ELSE}
  errnum := img_convert(PAVPicture(fAVFrameRGB), PIXEL_FMT_FFMPEG,
            PAVPicture(fAVFrame), fCodecContext^.pix_fmt,
            fCodecContext^.width, fCodecContext^.height);
  {$ENDIF}
  
  if (errnum < 0) then
  begin
    Log.LogError('Image conversion failed', 'TVideoPlayback_ffmpeg.GetFrame');
    Exit;
  end;

  {$IFDEF VideoBenchmark}
  Log.BenchmarkEnd(15);
  Log.BenchmarkStart(16);
  {$ENDIF}

  // TODO: data is not padded, so we will need to tell OpenGL.
  //   Or should we add padding with avpicture_fill? (check which one is faster)
  //glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

  glBindTexture(GL_TEXTURE_2D, fFrameTex);
  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0,
      fCodecContext^.width, fCodecContext^.height,
      PIXEL_FMT_OPENGL, GL_UNSIGNED_BYTE, fAVFrameRGB^.data[0]);

  if (not fFrameTexValid) then
    fFrameTexValid := true;

  {$ifdef DebugFrames}
  //frame decode debug display
  GoldenRec.Spawn(200, 35, 1, 16, 0, -1, ColoredStar, $ffff00);
  {$endif}

  {$IFDEF VideoBenchmark}
  Log.BenchmarkEnd(16);
  Log.LogBenchmark('FFmpeg', 15);
  Log.LogBenchmark('Texture', 16);
  {$ENDIF}
end;

procedure TVideoPlayback_FFmpeg.GetVideoRect(var ScreenRect, TexRect: TRectCoords);
var
  ScreenAspect: double;  // aspect of screen resolution
  ScaledVideoWidth, ScaledVideoHeight: double;
begin
  // Three aspects to take into account:
  //  1. Screen/display resolution (e.g. 1920x1080 -> 16:9)
  //  2. Render aspect (fixed to 800x600 -> 4:3)
  //  3. Movie aspect (video frame aspect stored in fAspect)
  ScreenAspect := ScreenW / ScreenH;

  case fAspectCorrection of
    acoStretch: begin
      ScaledVideoWidth  := RenderW;
      ScaledVideoHeight := RenderH;
    end;
    acoCrop: begin
      if (ScreenAspect >= fAspect) then
      begin
        ScaledVideoWidth  := RenderW;
        ScaledVideoHeight := RenderH * ScreenAspect/fAspect;
      end
      else
      begin
        ScaledVideoHeight := RenderH;
        ScaledVideoWidth  := RenderW * fAspect/ScreenAspect;
      end;
    end;
    acoLetterBox: begin
      ScaledVideoWidth  := RenderW;
      ScaledVideoHeight := RenderH * ScreenAspect/fAspect;
    end
    else
      raise Exception.Create('Unhandled aspect correction!');
  end;

  // center video
  ScreenRect.Left  := (RenderW - ScaledVideoWidth) / 2;
  ScreenRect.Right := ScreenRect.Left + ScaledVideoWidth;
  ScreenRect.Upper := (RenderH - ScaledVideoHeight) / 2;
  ScreenRect.Lower := ScreenRect.Upper + ScaledVideoHeight;

  // texture contains right/lower (power-of-2) padding.
  // Determine the texture coords of the video frame.
  TexRect.Left  := 0;
  TexRect.Right := fCodecContext^.width  / fTexWidth;
  TexRect.Upper := 0;
  TexRect.Lower := fCodecContext^.height / fTexHeight;
end;

procedure TVideoPlayback_FFmpeg.DrawGL(Screen: integer);
var
  ScreenRect: TRectCoords;
  TexRect: TRectCoords;
begin
  // have a nice black background to draw on
  // (even if there were errors opening the vid)
  // TODO: Philipp: IMO TVideoPlayback should not clear the screen at
  //       all, because clearing is already done by the background class
  //       at this moment.
  if (Screen = 1) then
  begin
    // It is important that we just clear once before we start
    // drawing the first screen otherwise the first screen
    // would be cleared by the drawgl called when the second
    // screen is drawn
    glClearColor(0, 0, 0, 0);
    glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);
  end;

  // exit if there's nothing to draw
  if (not fOpened) then
    Exit;

  {$IFDEF VideoBenchmark}
  Log.BenchmarkStart(15);
  {$ENDIF}

  // get texture and screen positions
  GetVideoRect(ScreenRect, TexRect);

  // we could use blending for brightness control, but do we need this?
  glDisable(GL_BLEND);

  glEnable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, fFrameTex);
  glColor3f(1, 1, 1);
  glBegin(GL_QUADS);
    // upper-left coord
    glTexCoord2f(TexRect.Left, TexRect.Upper);
    glVertex2f(ScreenRect.Left, ScreenRect.Upper);
    // lower-left coord
    glTexCoord2f(TexRect.Left, TexRect.Lower);
    glVertex2f(ScreenRect.Left, ScreenRect.Lower);
    // lower-right coord
    glTexCoord2f(TexRect.Right, TexRect.Lower);
    glVertex2f(ScreenRect.Right, ScreenRect.Lower);
    // upper-right coord
    glTexCoord2f(TexRect.Right, TexRect.Upper);
    glVertex2f(ScreenRect.Right, ScreenRect.Upper);
  glEnd;
  glDisable(GL_TEXTURE_2D);

  {$IFDEF VideoBenchmark}
  Log.BenchmarkEnd(15);
  Log.LogBenchmark('DrawGL', 15);
  {$ENDIF}

  {$IF Defined(Info) or Defined(DebugFrames)}
  ShowDebugInfo();
  {$IFEND}
end;

procedure TVideoPlayback_FFmpeg.ShowDebugInfo();
begin
  {$IFDEF Info}
  if (fTime+fTimeBase < 0) then
  begin
    glColor4f(0.7, 1, 0.3, 1);
    SetFontStyle (1);
    SetFontItalic(False);
    SetFontSize(27);
    SetFontPos (300, 0);
    glPrint('Delay due to negative VideoGap');
    glColor4f(1, 1, 1, 1);
  end;
  {$ENDIF}

  {$IFDEF DebugFrames}
    glColor4f(0, 0, 0, 0.2);
    glbegin(GL_QUADS);
      glVertex2f(0, 0);
      glVertex2f(0, 70);
      glVertex2f(250, 70);
      glVertex2f(250, 0);
    glEnd;

    glColor4f(1, 1, 1, 1);
    SetFontStyle (1);
    SetFontItalic(False);
    SetFontSize(27);
    SetFontPos (5, 0);
    glPrint('delaying frame');
    SetFontPos (5, 20);
    glPrint('fetching frame');
    SetFontPos (5, 40);
    glPrint('dropping frame');
  {$ENDIF}
end;

procedure TVideoPlayback_FFmpeg.Play;
begin
end;

procedure TVideoPlayback_FFmpeg.Pause;
begin
  fPaused := not fPaused;
end;

procedure TVideoPlayback_FFmpeg.Stop;
begin
end;

{**
 * Sets the stream's position.
 * The stream is set to the first keyframe with timestamp <= Time.
 * Note that fTime is set to Time no matter if the actual position seeked to is
 * at Time or the time of a preceding keyframe. fTime will be updated to the
 * actual frame time when GetFrame() is called the next time.
 * @param Time new position in seconds
 *}
procedure TVideoPlayback_FFmpeg.SetPosition(Time: real);
var
  SeekFlags: integer;
begin
  if not fOpened then
    Exit;

  if (Time < 0) then
    Time := 0;

  // TODO: handle fLoop-times
  //Time := Time mod VideoDuration;

  // Do not use the AVSEEK_FLAG_ANY here. It will seek to any frame, even
  // non keyframes (P-/B-frames). It will produce corrupted video frames as
  // FFmpeg does not use the information of the preceding I-frame.
  // The picture might be gray or green until the next keyframe occurs.
  // Instead seek the first keyframe smaller than the requested time
  // (AVSEEK_FLAG_BACKWARD). As this can be some seconds earlier than the
  // requested time, let the sync in GetFrame() do its job.
  SeekFlags := AVSEEK_FLAG_BACKWARD;

  fTime := Time;
  fEOF := false;
  fFrameTexValid := false; 

  if (av_seek_frame(fFormatContext, fStreamIndex, Floor(Time/fTimeBase), SeekFlags) < 0) then
  begin
    Log.LogError('av_seek_frame() failed', 'TVideoPlayback_ffmpeg.SetPosition');
    Exit;
  end;

  avcodec_flush_buffers(fCodecContext);
end;

function  TVideoPlayback_FFmpeg.GetPosition: real;
begin
  Result := fTime;
end;

initialization
  MediaManager.Add(TVideoPlayback_FFmpeg.Create);

end.