1FFMPEG-UTILS(1)                                                FFMPEG-UTILS(1)
2
3
4

NAME

6       ffmpeg-utils - FFmpeg utilities
7

DESCRIPTION

9       This document describes some generic features and utilities provided by
10       the libavutil library.
11

SYNTAX

13       This section documents the syntax and formats employed by the FFmpeg
14       libraries and tools.
15
16   Quoting and escaping
17       FFmpeg adopts the following quoting and escaping mechanism, unless
18       explicitly specified. The following rules are applied:
19
20       •   ' and \ are special characters (respectively used for quoting and
21           escaping). In addition to them, there might be other special
22           characters depending on the specific syntax where the escaping and
23           quoting are employed.
24
25       •   A special character is escaped by prefixing it with a \.
26
27       •   All characters enclosed between '' are included literally in the
28           parsed string. The quote character ' itself cannot be quoted, so
29           you may need to close the quote and escape it.
30
31       •   Leading and trailing whitespaces, unless escaped or quoted, are
32           removed from the parsed string.
33
34       Note that you may need to add a second level of escaping when using the
35       command line or a script, which depends on the syntax of the adopted
36       shell language.
37
38       The function "av_get_token" defined in libavutil/avstring.h can be used
39       to parse a token quoted or escaped according to the rules defined
40       above.
41
42       The tool tools/ffescape in the FFmpeg source tree can be used to
43       automatically quote or escape a string in a script.
44
45       Examples
46
47       •   Escape the string "Crime d'Amour" containing the "'" special
48           character:
49
50                   Crime d\'Amour
51
52       •   The string above contains a quote, so the "'" needs to be escaped
53           when quoting it:
54
55                   'Crime d'\''Amour'
56
57       •   Include leading or trailing whitespaces using quoting:
58
59                   '  this string starts and ends with whitespaces  '
60
61       •   Escaping and quoting can be mixed together:
62
63                   ' The string '\'string\'' is a string '
64
65       •   To include a literal \ you can use either escaping or quoting:
66
67                   'c:\foo' can be written as c:\\foo
68
69   Date
70       The accepted syntax is:
71
72               [(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
73               now
74
75       If the value is "now" it takes the current time.
76
77       Time is local time unless Z is appended, in which case it is
78       interpreted as UTC.  If the year-month-day part is not specified it
79       takes the current year-month-day.
80
81   Time duration
82       There are two accepted syntaxes for expressing time duration.
83
84               [-][<HH>:]<MM>:<SS>[.<m>...]
85
86       HH expresses the number of hours, MM the number of minutes for a
87       maximum of 2 digits, and SS the number of seconds for a maximum of 2
88       digits. The m at the end expresses decimal value for SS.
89
90       or
91
92               [-]<S>+[.<m>...][s|ms|us]
93
94       S expresses the number of seconds, with the optional decimal part m.
95       The optional literal suffixes s, ms or us indicate to interpret the
96       value as seconds, milliseconds or microseconds, respectively.
97
98       In both expressions, the optional - indicates negative duration.
99
100       Examples
101
102       The following examples are all valid time duration:
103
104       55  55 seconds
105
106       0.2 0.2 seconds
107
108       200ms
109           200 milliseconds, that's 0.2s
110
111       200000us
112           200000 microseconds, that's 0.2s
113
114       12:03:45
115           12 hours, 03 minutes and 45 seconds
116
117       23.189
118           23.189 seconds
119
120   Video size
121       Specify the size of the sourced video, it may be a string of the form
122       widthxheight, or the name of a size abbreviation.
123
124       The following abbreviations are recognized:
125
126       ntsc
127           720x480
128
129       pal 720x576
130
131       qntsc
132           352x240
133
134       qpal
135           352x288
136
137       sntsc
138           640x480
139
140       spal
141           768x576
142
143       film
144           352x240
145
146       ntsc-film
147           352x240
148
149       sqcif
150           128x96
151
152       qcif
153           176x144
154
155       cif 352x288
156
157       4cif
158           704x576
159
160       16cif
161           1408x1152
162
163       qqvga
164           160x120
165
166       qvga
167           320x240
168
169       vga 640x480
170
171       svga
172           800x600
173
174       xga 1024x768
175
176       uxga
177           1600x1200
178
179       qxga
180           2048x1536
181
182       sxga
183           1280x1024
184
185       qsxga
186           2560x2048
187
188       hsxga
189           5120x4096
190
191       wvga
192           852x480
193
194       wxga
195           1366x768
196
197       wsxga
198           1600x1024
199
200       wuxga
201           1920x1200
202
203       woxga
204           2560x1600
205
206       wqsxga
207           3200x2048
208
209       wquxga
210           3840x2400
211
212       whsxga
213           6400x4096
214
215       whuxga
216           7680x4800
217
218       cga 320x200
219
220       ega 640x350
221
222       hd480
223           852x480
224
225       hd720
226           1280x720
227
228       hd1080
229           1920x1080
230
231       2k  2048x1080
232
233       2kflat
234           1998x1080
235
236       2kscope
237           2048x858
238
239       4k  4096x2160
240
241       4kflat
242           3996x2160
243
244       4kscope
245           4096x1716
246
247       nhd 640x360
248
249       hqvga
250           240x160
251
252       wqvga
253           400x240
254
255       fwqvga
256           432x240
257
258       hvga
259           480x320
260
261       qhd 960x540
262
263       2kdci
264           2048x1080
265
266       4kdci
267           4096x2160
268
269       uhd2160
270           3840x2160
271
272       uhd4320
273           7680x4320
274
275   Video rate
276       Specify the frame rate of a video, expressed as the number of frames
277       generated per second. It has to be a string in the format
278       frame_rate_num/frame_rate_den, an integer number, a float number or a
279       valid video frame rate abbreviation.
280
281       The following abbreviations are recognized:
282
283       ntsc
284           30000/1001
285
286       pal 25/1
287
288       qntsc
289           30000/1001
290
291       qpal
292           25/1
293
294       sntsc
295           30000/1001
296
297       spal
298           25/1
299
300       film
301           24/1
302
303       ntsc-film
304           24000/1001
305
306   Ratio
307       A ratio can be expressed as an expression, or in the form
308       numerator:denominator.
309
310       Note that a ratio with infinite (1/0) or negative value is considered
311       valid, so you should check on the returned value if you want to exclude
312       those values.
313
314       The undefined value can be expressed using the "0:0" string.
315
316   Color
317       It can be the name of a color as defined below (case insensitive match)
318       or a "[0x|#]RRGGBB[AA]" sequence, possibly followed by @ and a string
319       representing the alpha component.
320
321       The alpha component may be a string composed by "0x" followed by an
322       hexadecimal number or a decimal number between 0.0 and 1.0, which
323       represents the opacity value (0x00 or 0.0 means completely transparent,
324       0xff or 1.0 completely opaque). If the alpha component is not specified
325       then 0xff is assumed.
326
327       The string random will result in a random color.
328
329       The following names of colors are recognized:
330
331       AliceBlue
332           0xF0F8FF
333
334       AntiqueWhite
335           0xFAEBD7
336
337       Aqua
338           0x00FFFF
339
340       Aquamarine
341           0x7FFFD4
342
343       Azure
344           0xF0FFFF
345
346       Beige
347           0xF5F5DC
348
349       Bisque
350           0xFFE4C4
351
352       Black
353           0x000000
354
355       BlanchedAlmond
356           0xFFEBCD
357
358       Blue
359           0x0000FF
360
361       BlueViolet
362           0x8A2BE2
363
364       Brown
365           0xA52A2A
366
367       BurlyWood
368           0xDEB887
369
370       CadetBlue
371           0x5F9EA0
372
373       Chartreuse
374           0x7FFF00
375
376       Chocolate
377           0xD2691E
378
379       Coral
380           0xFF7F50
381
382       CornflowerBlue
383           0x6495ED
384
385       Cornsilk
386           0xFFF8DC
387
388       Crimson
389           0xDC143C
390
391       Cyan
392           0x00FFFF
393
394       DarkBlue
395           0x00008B
396
397       DarkCyan
398           0x008B8B
399
400       DarkGoldenRod
401           0xB8860B
402
403       DarkGray
404           0xA9A9A9
405
406       DarkGreen
407           0x006400
408
409       DarkKhaki
410           0xBDB76B
411
412       DarkMagenta
413           0x8B008B
414
415       DarkOliveGreen
416           0x556B2F
417
418       Darkorange
419           0xFF8C00
420
421       DarkOrchid
422           0x9932CC
423
424       DarkRed
425           0x8B0000
426
427       DarkSalmon
428           0xE9967A
429
430       DarkSeaGreen
431           0x8FBC8F
432
433       DarkSlateBlue
434           0x483D8B
435
436       DarkSlateGray
437           0x2F4F4F
438
439       DarkTurquoise
440           0x00CED1
441
442       DarkViolet
443           0x9400D3
444
445       DeepPink
446           0xFF1493
447
448       DeepSkyBlue
449           0x00BFFF
450
451       DimGray
452           0x696969
453
454       DodgerBlue
455           0x1E90FF
456
457       FireBrick
458           0xB22222
459
460       FloralWhite
461           0xFFFAF0
462
463       ForestGreen
464           0x228B22
465
466       Fuchsia
467           0xFF00FF
468
469       Gainsboro
470           0xDCDCDC
471
472       GhostWhite
473           0xF8F8FF
474
475       Gold
476           0xFFD700
477
478       GoldenRod
479           0xDAA520
480
481       Gray
482           0x808080
483
484       Green
485           0x008000
486
487       GreenYellow
488           0xADFF2F
489
490       HoneyDew
491           0xF0FFF0
492
493       HotPink
494           0xFF69B4
495
496       IndianRed
497           0xCD5C5C
498
499       Indigo
500           0x4B0082
501
502       Ivory
503           0xFFFFF0
504
505       Khaki
506           0xF0E68C
507
508       Lavender
509           0xE6E6FA
510
511       LavenderBlush
512           0xFFF0F5
513
514       LawnGreen
515           0x7CFC00
516
517       LemonChiffon
518           0xFFFACD
519
520       LightBlue
521           0xADD8E6
522
523       LightCoral
524           0xF08080
525
526       LightCyan
527           0xE0FFFF
528
529       LightGoldenRodYellow
530           0xFAFAD2
531
532       LightGreen
533           0x90EE90
534
535       LightGrey
536           0xD3D3D3
537
538       LightPink
539           0xFFB6C1
540
541       LightSalmon
542           0xFFA07A
543
544       LightSeaGreen
545           0x20B2AA
546
547       LightSkyBlue
548           0x87CEFA
549
550       LightSlateGray
551           0x778899
552
553       LightSteelBlue
554           0xB0C4DE
555
556       LightYellow
557           0xFFFFE0
558
559       Lime
560           0x00FF00
561
562       LimeGreen
563           0x32CD32
564
565       Linen
566           0xFAF0E6
567
568       Magenta
569           0xFF00FF
570
571       Maroon
572           0x800000
573
574       MediumAquaMarine
575           0x66CDAA
576
577       MediumBlue
578           0x0000CD
579
580       MediumOrchid
581           0xBA55D3
582
583       MediumPurple
584           0x9370D8
585
586       MediumSeaGreen
587           0x3CB371
588
589       MediumSlateBlue
590           0x7B68EE
591
592       MediumSpringGreen
593           0x00FA9A
594
595       MediumTurquoise
596           0x48D1CC
597
598       MediumVioletRed
599           0xC71585
600
601       MidnightBlue
602           0x191970
603
604       MintCream
605           0xF5FFFA
606
607       MistyRose
608           0xFFE4E1
609
610       Moccasin
611           0xFFE4B5
612
613       NavajoWhite
614           0xFFDEAD
615
616       Navy
617           0x000080
618
619       OldLace
620           0xFDF5E6
621
622       Olive
623           0x808000
624
625       OliveDrab
626           0x6B8E23
627
628       Orange
629           0xFFA500
630
631       OrangeRed
632           0xFF4500
633
634       Orchid
635           0xDA70D6
636
637       PaleGoldenRod
638           0xEEE8AA
639
640       PaleGreen
641           0x98FB98
642
643       PaleTurquoise
644           0xAFEEEE
645
646       PaleVioletRed
647           0xD87093
648
649       PapayaWhip
650           0xFFEFD5
651
652       PeachPuff
653           0xFFDAB9
654
655       Peru
656           0xCD853F
657
658       Pink
659           0xFFC0CB
660
661       Plum
662           0xDDA0DD
663
664       PowderBlue
665           0xB0E0E6
666
667       Purple
668           0x800080
669
670       Red 0xFF0000
671
672       RosyBrown
673           0xBC8F8F
674
675       RoyalBlue
676           0x4169E1
677
678       SaddleBrown
679           0x8B4513
680
681       Salmon
682           0xFA8072
683
684       SandyBrown
685           0xF4A460
686
687       SeaGreen
688           0x2E8B57
689
690       SeaShell
691           0xFFF5EE
692
693       Sienna
694           0xA0522D
695
696       Silver
697           0xC0C0C0
698
699       SkyBlue
700           0x87CEEB
701
702       SlateBlue
703           0x6A5ACD
704
705       SlateGray
706           0x708090
707
708       Snow
709           0xFFFAFA
710
711       SpringGreen
712           0x00FF7F
713
714       SteelBlue
715           0x4682B4
716
717       Tan 0xD2B48C
718
719       Teal
720           0x008080
721
722       Thistle
723           0xD8BFD8
724
725       Tomato
726           0xFF6347
727
728       Turquoise
729           0x40E0D0
730
731       Violet
732           0xEE82EE
733
734       Wheat
735           0xF5DEB3
736
737       White
738           0xFFFFFF
739
740       WhiteSmoke
741           0xF5F5F5
742
743       Yellow
744           0xFFFF00
745
746       YellowGreen
747           0x9ACD32
748
749   Channel Layout
750       A channel layout specifies the spatial disposition of the channels in a
751       multi-channel audio stream. To specify a channel layout, FFmpeg makes
752       use of a special syntax.
753
754       Individual channels are identified by an id, as given by the table
755       below:
756
757       FL  front left
758
759       FR  front right
760
761       FC  front center
762
763       LFE low frequency
764
765       BL  back left
766
767       BR  back right
768
769       FLC front left-of-center
770
771       FRC front right-of-center
772
773       BC  back center
774
775       SL  side left
776
777       SR  side right
778
779       TC  top center
780
781       TFL top front left
782
783       TFC top front center
784
785       TFR top front right
786
787       TBL top back left
788
789       TBC top back center
790
791       TBR top back right
792
793       DL  downmix left
794
795       DR  downmix right
796
797       WL  wide left
798
799       WR  wide right
800
801       SDL surround direct left
802
803       SDR surround direct right
804
805       LFE2
806           low frequency 2
807
808       Standard channel layout compositions can be specified by using the
809       following identifiers:
810
811       mono
812           FC
813
814       stereo
815           FL+FR
816
817       2.1 FL+FR+LFE
818
819       3.0 FL+FR+FC
820
821       3.0(back)
822           FL+FR+BC
823
824       4.0 FL+FR+FC+BC
825
826       quad
827           FL+FR+BL+BR
828
829       quad(side)
830           FL+FR+SL+SR
831
832       3.1 FL+FR+FC+LFE
833
834       5.0 FL+FR+FC+BL+BR
835
836       5.0(side)
837           FL+FR+FC+SL+SR
838
839       4.1 FL+FR+FC+LFE+BC
840
841       5.1 FL+FR+FC+LFE+BL+BR
842
843       5.1(side)
844           FL+FR+FC+LFE+SL+SR
845
846       6.0 FL+FR+FC+BC+SL+SR
847
848       6.0(front)
849           FL+FR+FLC+FRC+SL+SR
850
851       hexagonal
852           FL+FR+FC+BL+BR+BC
853
854       6.1 FL+FR+FC+LFE+BC+SL+SR
855
856       6.1 FL+FR+FC+LFE+BL+BR+BC
857
858       6.1(front)
859           FL+FR+LFE+FLC+FRC+SL+SR
860
861       7.0 FL+FR+FC+BL+BR+SL+SR
862
863       7.0(front)
864           FL+FR+FC+FLC+FRC+SL+SR
865
866       7.1 FL+FR+FC+LFE+BL+BR+SL+SR
867
868       7.1(wide)
869           FL+FR+FC+LFE+BL+BR+FLC+FRC
870
871       7.1(wide-side)
872           FL+FR+FC+LFE+FLC+FRC+SL+SR
873
874       octagonal
875           FL+FR+FC+BL+BR+BC+SL+SR
876
877       hexadecagonal
878           FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
879
880       downmix
881           DL+DR
882
883       22.2
884           FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
885
886       A custom channel layout can be specified as a sequence of terms,
887       separated by '+' or '|'. Each term can be:
888
889       •   the name of a standard channel layout (e.g. mono, stereo, 4.0,
890           quad, 5.0, etc.)
891
892       •   the name of a single channel (e.g. FL, FR, FC, LFE, etc.)
893
894       •   a number of channels, in decimal, followed by 'c', yielding the
895           default channel layout for that number of channels (see the
896           function "av_get_default_channel_layout"). Note that not all
897           channel counts have a default layout.
898
899       •   a number of channels, in decimal, followed by 'C', yielding an
900           unknown channel layout with the specified number of channels. Note
901           that not all channel layout specification strings support unknown
902           channel layouts.
903
904       •   a channel layout mask, in hexadecimal starting with "0x" (see the
905           "AV_CH_*" macros in libavutil/channel_layout.h.
906
907       Before libavutil version 53 the trailing character "c" to specify a
908       number of channels was optional, but now it is required, while a
909       channel layout mask can also be specified as a decimal number (if and
910       only if not followed by "c" or "C").
911
912       See also the function "av_get_channel_layout" defined in
913       libavutil/channel_layout.h.
914

EXPRESSION EVALUATION

916       When evaluating an arithmetic expression, FFmpeg uses an internal
917       formula evaluator, implemented through the libavutil/eval.h interface.
918
919       An expression may contain unary, binary operators, constants, and
920       functions.
921
922       Two expressions expr1 and expr2 can be combined to form another
923       expression "expr1;expr2".  expr1 and expr2 are evaluated in turn, and
924       the new expression evaluates to the value of expr2.
925
926       The following binary operators are available: "+", "-", "*", "/", "^".
927
928       The following unary operators are available: "+", "-".
929
930       The following functions are available:
931
932       abs(x)
933           Compute absolute value of x.
934
935       acos(x)
936           Compute arccosine of x.
937
938       asin(x)
939           Compute arcsine of x.
940
941       atan(x)
942           Compute arctangent of x.
943
944       atan2(x, y)
945           Compute principal value of the arc tangent of y/x.
946
947       between(x, min, max)
948           Return 1 if x is greater than or equal to min and lesser than or
949           equal to max, 0 otherwise.
950
951       bitand(x, y)
952       bitor(x, y)
953           Compute bitwise and/or operation on x and y.
954
955           The results of the evaluation of x and y are converted to integers
956           before executing the bitwise operation.
957
958           Note that both the conversion to integer and the conversion back to
959           floating point can lose precision. Beware of unexpected results for
960           large numbers (usually 2^53 and larger).
961
962       ceil(expr)
963           Round the value of expression expr upwards to the nearest integer.
964           For example, "ceil(1.5)" is "2.0".
965
966       clip(x, min, max)
967           Return the value of x clipped between min and max.
968
969       cos(x)
970           Compute cosine of x.
971
972       cosh(x)
973           Compute hyperbolic cosine of x.
974
975       eq(x, y)
976           Return 1 if x and y are equivalent, 0 otherwise.
977
978       exp(x)
979           Compute exponential of x (with base "e", the Euler's number).
980
981       floor(expr)
982           Round the value of expression expr downwards to the nearest
983           integer. For example, "floor(-1.5)" is "-2.0".
984
985       gauss(x)
986           Compute Gauss function of x, corresponding to "exp(-x*x/2) /
987           sqrt(2*PI)".
988
989       gcd(x, y)
990           Return the greatest common divisor of x and y. If both x and y are
991           0 or either or both are less than zero then behavior is undefined.
992
993       gt(x, y)
994           Return 1 if x is greater than y, 0 otherwise.
995
996       gte(x, y)
997           Return 1 if x is greater than or equal to y, 0 otherwise.
998
999       hypot(x, y)
1000           This function is similar to the C function with the same name; it
1001           returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right
1002           triangle with sides of length x and y, or the distance of the point
1003           (x, y) from the origin.
1004
1005       if(x, y)
1006           Evaluate x, and if the result is non-zero return the result of the
1007           evaluation of y, return 0 otherwise.
1008
1009       if(x, y, z)
1010           Evaluate x, and if the result is non-zero return the evaluation
1011           result of y, otherwise the evaluation result of z.
1012
1013       ifnot(x, y)
1014           Evaluate x, and if the result is zero return the result of the
1015           evaluation of y, return 0 otherwise.
1016
1017       ifnot(x, y, z)
1018           Evaluate x, and if the result is zero return the evaluation result
1019           of y, otherwise the evaluation result of z.
1020
1021       isinf(x)
1022           Return 1.0 if x is +/-INFINITY, 0.0 otherwise.
1023
1024       isnan(x)
1025           Return 1.0 if x is NAN, 0.0 otherwise.
1026
1027       ld(var)
1028           Load the value of the internal variable with number var, which was
1029           previously stored with st(var, expr).  The function returns the
1030           loaded value.
1031
1032       lerp(x, y, z)
1033           Return linear interpolation between x and y by amount of z.
1034
1035       log(x)
1036           Compute natural logarithm of x.
1037
1038       lt(x, y)
1039           Return 1 if x is lesser than y, 0 otherwise.
1040
1041       lte(x, y)
1042           Return 1 if x is lesser than or equal to y, 0 otherwise.
1043
1044       max(x, y)
1045           Return the maximum between x and y.
1046
1047       min(x, y)
1048           Return the minimum between x and y.
1049
1050       mod(x, y)
1051           Compute the remainder of division of x by y.
1052
1053       not(expr)
1054           Return 1.0 if expr is zero, 0.0 otherwise.
1055
1056       pow(x, y)
1057           Compute the power of x elevated y, it is equivalent to "(x)^(y)".
1058
1059       print(t)
1060       print(t, l)
1061           Print the value of expression t with loglevel l. If l is not
1062           specified then a default log level is used.  Returns the value of
1063           the expression printed.
1064
1065           Prints t with loglevel l
1066
1067       random(x)
1068           Return a pseudo random value between 0.0 and 1.0. x is the index of
1069           the internal variable which will be used to save the seed/state.
1070
1071       root(expr, max)
1072           Find an input value for which the function represented by expr with
1073           argument ld(0) is 0 in the interval 0..max.
1074
1075           The expression in expr must denote a continuous function or the
1076           result is undefined.
1077
1078           ld(0) is used to represent the function input value, which means
1079           that the given expression will be evaluated multiple times with
1080           various input values that the expression can access through ld(0).
1081           When the expression evaluates to 0 then the corresponding input
1082           value will be returned.
1083
1084       round(expr)
1085           Round the value of expression expr to the nearest integer. For
1086           example, "round(1.5)" is "2.0".
1087
1088       sgn(x)
1089           Compute sign of x.
1090
1091       sin(x)
1092           Compute sine of x.
1093
1094       sinh(x)
1095           Compute hyperbolic sine of x.
1096
1097       sqrt(expr)
1098           Compute the square root of expr. This is equivalent to "(expr)^.5".
1099
1100       squish(x)
1101           Compute expression "1/(1 + exp(4*x))".
1102
1103       st(var, expr)
1104           Store the value of the expression expr in an internal variable. var
1105           specifies the number of the variable where to store the value, and
1106           it is a value ranging from 0 to 9. The function returns the value
1107           stored in the internal variable.  Note, Variables are currently not
1108           shared between expressions.
1109
1110       tan(x)
1111           Compute tangent of x.
1112
1113       tanh(x)
1114           Compute hyperbolic tangent of x.
1115
1116       taylor(expr, x)
1117       taylor(expr, x, id)
1118           Evaluate a Taylor series at x, given an expression representing the
1119           "ld(id)"-th derivative of a function at 0.
1120
1121           When the series does not converge the result is undefined.
1122
1123           ld(id) is used to represent the derivative order in expr, which
1124           means that the given expression will be evaluated multiple times
1125           with various input values that the expression can access through
1126           "ld(id)". If id is not specified then 0 is assumed.
1127
1128           Note, when you have the derivatives at y instead of 0,
1129           "taylor(expr, x-y)" can be used.
1130
1131       time(0)
1132           Return the current (wallclock) time in seconds.
1133
1134       trunc(expr)
1135           Round the value of expression expr towards zero to the nearest
1136           integer. For example, "trunc(-1.5)" is "-1.0".
1137
1138       while(cond, expr)
1139           Evaluate expression expr while the expression cond is non-zero, and
1140           returns the value of the last expr evaluation, or NAN if cond was
1141           always false.
1142
1143       The following constants are available:
1144
1145       PI  area of the unit disc, approximately 3.14
1146
1147       E   exp(1) (Euler's number), approximately 2.718
1148
1149       PHI golden ratio (1+sqrt(5))/2, approximately 1.618
1150
1151       Assuming that an expression is considered "true" if it has a non-zero
1152       value, note that:
1153
1154       "*" works like AND
1155
1156       "+" works like OR
1157
1158       For example the construct:
1159
1160               if (A AND B) then C
1161
1162       is equivalent to:
1163
1164               if(A*B, C)
1165
1166       In your C code, you can extend the list of unary and binary functions,
1167       and define recognized constants, so that they are available for your
1168       expressions.
1169
1170       The evaluator also recognizes the International System unit prefixes.
1171       If 'i' is appended after the prefix, binary prefixes are used, which
1172       are based on powers of 1024 instead of powers of 1000.  The 'B' postfix
1173       multiplies the value by 8, and can be appended after a unit prefix or
1174       used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as
1175       number postfix.
1176
1177       The list of available International System prefixes follows, with
1178       indication of the corresponding powers of 10 and of 2.
1179
1180       y   10^-24 / 2^-80
1181
1182       z   10^-21 / 2^-70
1183
1184       a   10^-18 / 2^-60
1185
1186       f   10^-15 / 2^-50
1187
1188       p   10^-12 / 2^-40
1189
1190       n   10^-9 / 2^-30
1191
1192       u   10^-6 / 2^-20
1193
1194       m   10^-3 / 2^-10
1195
1196       c   10^-2
1197
1198       d   10^-1
1199
1200       h   10^2
1201
1202       k   10^3 / 2^10
1203
1204       K   10^3 / 2^10
1205
1206       M   10^6 / 2^20
1207
1208       G   10^9 / 2^30
1209
1210       T   10^12 / 2^40
1211
1212       P   10^15 / 2^40
1213
1214       E   10^18 / 2^50
1215
1216       Z   10^21 / 2^60
1217
1218       Y   10^24 / 2^70
1219

SEE ALSO

1221       ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3)
1222

AUTHORS

1224       The FFmpeg developers.
1225
1226       For details about the authorship, see the Git history of the project
1227       (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
1228       the FFmpeg source directory, or browsing the online repository at
1229       <http://source.ffmpeg.org>.
1230
1231       Maintainers for the specific components are listed in the file
1232       MAINTAINERS in the source code tree.
1233
1234
1235
1236                                                               FFMPEG-UTILS(1)