DESCRIPTION
This document describes some generic features and utilities provided by the libavutil library.SYNTAX
This section documents the syntax and formats employed by the FFmpeg libraries and tools.Quoting and escaping
FFmpeg adopts the following quoting and escaping mechanism, unless explicitly specified. The following rules are applied: ' and \ are special characters (respectively used for quoting and escaping). In addition to them, there might be other special characters depending on the specific syntax where the escaping and quoting are employed.
 A special character is escaped by prefixing it with a \.
 All characters enclosed between '' are included literally in the parsed string. The quote character ' itself cannot be quoted, so you may need to close the quote and escape it.
 Leading and trailing whitespaces, unless escaped or quoted, are removed from the parsed string.
Note that you may need to add a second level of escaping when using the command line or a script, which depends on the syntax of the adopted shell language.
The function "av_get_token" defined in libavutil/avstring.h can be used to parse a token quoted or escaped according to the rules defined above.
The tool tools/ffescape in the FFmpeg source tree can be used to automatically quote or escape a string in a script.
Examples

Escape the string "Crime d'Amour" containing the "'" special
character:
Crime d\'Amour

The string above contains a quote, so the "'" needs to be escaped
when quoting it:
'Crime d'\''Amour'

Include leading or trailing whitespaces using quoting:
' this string starts and ends with whitespaces '

Escaping and quoting can be mixed together:
' The string '\'string\'' is a string '

To include a literal \ you can use either escaping or quoting:
'c:\foo' can be written as c:\\foo
Date
The accepted syntax is:
[(YYYYMMDDYYYYMMDD)[Tt ]]((HH:MM:SS[.m...]]])(HHMMSS[.m...]]]))[Z] now
If the value is ``now'' it takes the current time.
Time is local time unless Z is appended, in which case it is interpreted as UTC. If the yearmonthday part is not specified it takes the current yearmonthday.
Time duration
There are two accepted syntaxes for expressing time duration.
[][<HH>:]<MM>:<SS>[.<m>...]
HH expresses the number of hours, MM the number of minutes for a maximum of 2 digits, and SS the number of seconds for a maximum of 2 digits. The m at the end expresses decimal value for SS.
or
[]<S>+[.<m>...]
S expresses the number of seconds, with the optional decimal part m.
In both expressions, the optional  indicates negative duration.
Examples
The following examples are all valid time duration:
 55
 55 seconds
 12:03:45
 12 hours, 03 minutes and 45 seconds
 23.189
 23.189 seconds
Video size
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation.The following abbreviations are recognized:
 ntsc
 720x480
 pal
 720x576
 qntsc
 352x240
 qpal
 352x288
 sntsc
 640x480
 spal
 768x576
 film
 352x240
 ntscfilm
 352x240
 sqcif
 128x96
 qcif
 176x144
 cif
 352x288
 4cif
 704x576
 16cif
 1408x1152
 qqvga
 160x120
 qvga
 320x240
 vga
 640x480
 svga
 800x600
 xga
 1024x768
 uxga
 1600x1200
 qxga
 2048x1536
 sxga
 1280x1024
 qsxga
 2560x2048
 hsxga
 5120x4096
 wvga
 852x480
 wxga
 1366x768
 wsxga
 1600x1024
 wuxga
 1920x1200
 woxga
 2560x1600
 wqsxga
 3200x2048
 wquxga
 3840x2400
 whsxga
 6400x4096
 whuxga
 7680x4800
 cga
 320x200
 ega
 640x350
 hd480
 852x480
 hd720
 1280x720
 hd1080
 1920x1080
 2k
 2048x1080
 2kflat
 1998x1080
 2kscope
 2048x858
 4k
 4096x2160
 4kflat
 3996x2160
 4kscope
 4096x1716
 nhd
 640x360
 hqvga
 240x160
 wqvga
 400x240
 fwqvga
 432x240
 hvga
 480x320
 qhd
 960x540
 2kdci
 2048x1080
 4kdci
 4096x2160
 uhd2160
 3840x2160
 uhd4320
 7680x4320
Video rate
Specify the frame rate of a video, expressed as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation.The following abbreviations are recognized:
 ntsc
 30000/1001
 pal
 25/1
 qntsc
 30000/1001
 qpal
 25/1
 sntsc
 30000/1001
 spal
 25/1
 film
 24/1
 ntscfilm
 24000/1001
Ratio
A ratio can be expressed as an expression, or in the form numerator:denominator.Note that a ratio with infinite (1/0) or negative value is considered valid, so you should check on the returned value if you want to exclude those values.
The undefined value can be expressed using the ``0:0'' string.
Color
It can be the name of a color as defined below (case insensitive match) or a "[0x#]RRGGBB[AA]" sequence, possibly followed by @ and a string representing the alpha component.The alpha component may be a string composed by ``0x'' followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (0x00 or 0.0 means completely transparent, 0xff or 1.0 completely opaque). If the alpha component is not specified then 0xff is assumed.
The string random will result in a random color.
The following names of colors are recognized:
 AliceBlue
 0xF0F8FF
 AntiqueWhite
 0xFAEBD7
 Aqua
 0x00FFFF
 Aquamarine
 0x7FFFD4
 Azure
 0xF0FFFF
 Beige
 0xF5F5DC
 Bisque
 0xFFE4C4
 Black
 0x000000
 BlanchedAlmond
 0xFFEBCD
 Blue
 0x0000FF
 BlueViolet
 0x8A2BE2
 Brown
 0xA52A2A
 BurlyWood
 0xDEB887
 CadetBlue
 0x5F9EA0
 Chartreuse
 0x7FFF00
 Chocolate
 0xD2691E
 Coral
 0xFF7F50
 CornflowerBlue
 0x6495ED
 Cornsilk
 0xFFF8DC
 Crimson
 0xDC143C
 Cyan
 0x00FFFF
 DarkBlue
 0x00008B
 DarkCyan
 0x008B8B
 DarkGoldenRod
 0xB8860B
 DarkGray
 0xA9A9A9
 DarkGreen
 0x006400
 DarkKhaki
 0xBDB76B
 DarkMagenta
 0x8B008B
 DarkOliveGreen
 0x556B2F
 Darkorange
 0xFF8C00
 DarkOrchid
 0x9932CC
 DarkRed
 0x8B0000
 DarkSalmon
 0xE9967A
 DarkSeaGreen
 0x8FBC8F
 DarkSlateBlue
 0x483D8B
 DarkSlateGray
 0x2F4F4F
 DarkTurquoise
 0x00CED1
 DarkViolet
 0x9400D3
 DeepPink
 0xFF1493
 DeepSkyBlue
 0x00BFFF
 DimGray
 0x696969
 DodgerBlue
 0x1E90FF
 FireBrick
 0xB22222
 FloralWhite
 0xFFFAF0
 ForestGreen
 0x228B22
 Fuchsia
 0xFF00FF
 Gainsboro
 0xDCDCDC
 GhostWhite
 0xF8F8FF
 Gold
 0xFFD700
 GoldenRod
 0xDAA520
 Gray
 0x808080
 Green
 0x008000
 GreenYellow
 0xADFF2F
 HoneyDew
 0xF0FFF0
 HotPink
 0xFF69B4
 IndianRed
 0xCD5C5C
 Indigo
 0x4B0082
 Ivory
 0xFFFFF0
 Khaki
 0xF0E68C
 Lavender
 0xE6E6FA
 LavenderBlush
 0xFFF0F5
 LawnGreen
 0x7CFC00
 LemonChiffon
 0xFFFACD
 LightBlue
 0xADD8E6
 LightCoral
 0xF08080
 LightCyan
 0xE0FFFF
 LightGoldenRodYellow
 0xFAFAD2
 LightGreen
 0x90EE90
 LightGrey
 0xD3D3D3
 LightPink
 0xFFB6C1
 LightSalmon
 0xFFA07A
 LightSeaGreen
 0x20B2AA
 LightSkyBlue
 0x87CEFA
 LightSlateGray
 0x778899
 LightSteelBlue
 0xB0C4DE
 LightYellow
 0xFFFFE0
 Lime
 0x00FF00
 LimeGreen
 0x32CD32
 Linen
 0xFAF0E6
 Magenta
 0xFF00FF
 Maroon
 0x800000
 MediumAquaMarine
 0x66CDAA
 MediumBlue
 0x0000CD
 MediumOrchid
 0xBA55D3
 MediumPurple
 0x9370D8
 MediumSeaGreen
 0x3CB371
 MediumSlateBlue
 0x7B68EE
 MediumSpringGreen
 0x00FA9A
 MediumTurquoise
 0x48D1CC
 MediumVioletRed
 0xC71585
 MidnightBlue
 0x191970
 MintCream
 0xF5FFFA
 MistyRose
 0xFFE4E1
 Moccasin
 0xFFE4B5
 NavajoWhite
 0xFFDEAD
 Navy
 0x000080
 OldLace
 0xFDF5E6
 Olive
 0x808000
 OliveDrab
 0x6B8E23
 Orange
 0xFFA500
 OrangeRed
 0xFF4500
 Orchid
 0xDA70D6
 PaleGoldenRod
 0xEEE8AA
 PaleGreen
 0x98FB98
 PaleTurquoise
 0xAFEEEE
 PaleVioletRed
 0xD87093
 PapayaWhip
 0xFFEFD5
 PeachPuff
 0xFFDAB9
 Peru
 0xCD853F
 Pink
 0xFFC0CB
 Plum
 0xDDA0DD
 PowderBlue
 0xB0E0E6
 Purple
 0x800080
 Red
 0xFF0000
 RosyBrown
 0xBC8F8F
 RoyalBlue
 0x4169E1
 SaddleBrown
 0x8B4513
 Salmon
 0xFA8072
 SandyBrown
 0xF4A460
 SeaGreen
 0x2E8B57
 SeaShell
 0xFFF5EE
 Sienna
 0xA0522D
 Silver
 0xC0C0C0
 SkyBlue
 0x87CEEB
 SlateBlue
 0x6A5ACD
 SlateGray
 0x708090
 Snow
 0xFFFAFA
 SpringGreen
 0x00FF7F
 SteelBlue
 0x4682B4
 Tan
 0xD2B48C
 Teal
 0x008080
 Thistle
 0xD8BFD8
 Tomato
 0xFF6347
 Turquoise
 0x40E0D0
 Violet
 0xEE82EE
 Wheat
 0xF5DEB3
 White
 0xFFFFFF
 WhiteSmoke
 0xF5F5F5
 Yellow
 0xFFFF00
 YellowGreen
 0x9ACD32
Channel Layout
A channel layout specifies the spatial disposition of the channels in a multichannel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax.Individual channels are identified by an id, as given by the table below:
 FL
 front left
 FR
 front right
 FC
 front center
 LFE
 low frequency
 BL
 back left
 BR
 back right
 FLC
 front leftofcenter
 FRC
 front rightofcenter
 BC
 back center
 SL
 side left
 SR
 side right
 TC
 top center
 TFL
 top front left
 TFC
 top front center
 TFR
 top front right
 TBL
 top back left
 TBC
 top back center
 TBR
 top back right
 DL
 downmix left
 DR
 downmix right
 WL
 wide left
 WR
 wide right
 SDL
 surround direct left
 SDR
 surround direct right
 LFE2
 low frequency 2
Standard channel layout compositions can be specified by using the following identifiers:
 mono
 FC
 stereo
 FL+FR
 2.1
 FL+FR+LFE
 3.0
 FL+FR+FC
 3.0(back)
 FL+FR+BC
 4.0
 FL+FR+FC+BC
 quad
 FL+FR+BL+BR
 quad(side)
 FL+FR+SL+SR
 3.1
 FL+FR+FC+LFE
 5.0
 FL+FR+FC+BL+BR
 5.0(side)
 FL+FR+FC+SL+SR
 4.1
 FL+FR+FC+LFE+BC
 5.1
 FL+FR+FC+LFE+BL+BR
 5.1(side)
 FL+FR+FC+LFE+SL+SR
 6.0
 FL+FR+FC+BC+SL+SR
 6.0(front)
 FL+FR+FLC+FRC+SL+SR
 hexagonal
 FL+FR+FC+BL+BR+BC
 6.1
 FL+FR+FC+LFE+BC+SL+SR
 6.1
 FL+FR+FC+LFE+BL+BR+BC
 6.1(front)
 FL+FR+LFE+FLC+FRC+SL+SR
 7.0
 FL+FR+FC+BL+BR+SL+SR
 7.0(front)
 FL+FR+FC+FLC+FRC+SL+SR
 7.1
 FL+FR+FC+LFE+BL+BR+SL+SR
 7.1(wide)
 FL+FR+FC+LFE+BL+BR+FLC+FRC
 7.1(wideside)
 FL+FR+FC+LFE+FLC+FRC+SL+SR
 octagonal
 FL+FR+FC+BL+BR+BC+SL+SR
 downmix
 DL+DR
A custom channel layout can be specified as a sequence of terms, separated by '+' or ''. Each term can be:
 the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.)
 the name of a single channel (e.g. FL, FR, FC, LFE, etc.)
 a number of channels, in decimal, optionally followed by 'c', yielding the default channel layout for that number of channels (see the function "av_get_default_channel_layout")
 a channel layout mask, in hexadecimal starting with ``0x'' (see the "AV_CH_*" macros in libavutil/channel_layout.h.
Starting from libavutil version 53 the trailing character ``c'' to specify a number of channels will be required, while a channel layout mask could also be specified as a decimal number (if and only if not followed by ``c'').
See also the function "av_get_channel_layout" defined in libavutil/channel_layout.h.
EXPRESSION EVALUATION
When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the libavutil/eval.h interface.An expression may contain unary, binary operators, constants, and functions.
Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2.
The following binary operators are available: "+", "", "*", "/", "^".
The following unary operators are available: "+", "".
The following functions are available:
 abs(x)
 Compute absolute value of x.
 acos(x)
 Compute arccosine of x.
 asin(x)
 Compute arcsine of x.
 atan(x)
 Compute arctangent of x.
 between(x, min, max)
 Return 1 if x is greater than or equal to min and lesser than or equal to max, 0 otherwise.
 bitand(x, y)
 bitor(x, y)

Compute bitwise and/or operation on x and y.
The results of the evaluation of x and y are converted to integers before executing the bitwise operation.
Note that both the conversion to integer and the conversion back to floating point can lose precision. Beware of unexpected results for large numbers (usually 2^53 and larger).
 ceil(expr)
 Round the value of expression expr upwards to the nearest integer. For example, ``ceil(1.5)'' is ``2.0''.
 clip(x, min, max)
 Return the value of x clipped between min and max.
 cos(x)
 Compute cosine of x.
 cosh(x)
 Compute hyperbolic cosine of x.
 eq(x, y)
 Return 1 if x and y are equivalent, 0 otherwise.
 exp(x)
 Compute exponential of x (with base "e", the Euler's number).
 floor(expr)
 Round the value of expression expr downwards to the nearest integer. For example, ``floor(1.5)'' is ``2.0''.
 gauss(x)
 Compute Gauss function of x, corresponding to "exp(x*x/2) / sqrt(2*PI)".
 gcd(x, y)
 Return the greatest common divisor of x and y. If both x and y are 0 or either or both are less than zero then behavior is undefined.
 gt(x, y)
 Return 1 if x is greater than y, 0 otherwise.
 gte(x, y)
 Return 1 if x is greater than or equal to y, 0 otherwise.
 hypot(x, y)
 This function is similar to the C function with the same name; it returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin.
 if(x, y)
 Evaluate x, and if the result is nonzero return the result of the evaluation of y, return 0 otherwise.
 if(x, y, z)
 Evaluate x, and if the result is nonzero return the evaluation result of y, otherwise the evaluation result of z.
 ifnot(x, y)
 Evaluate x, and if the result is zero return the result of the evaluation of y, return 0 otherwise.
 ifnot(x, y, z)
 Evaluate x, and if the result is zero return the evaluation result of y, otherwise the evaluation result of z.
 isinf(x)
 Return 1.0 if x is +/INFINITY, 0.0 otherwise.
 isnan(x)
 Return 1.0 if x is NAN, 0.0 otherwise.
 ld(var)
 Load the value of the internal variable with number var, which was previously stored with st(var, expr). The function returns the loaded value.
 log(x)
 Compute natural logarithm of x.
 lt(x, y)
 Return 1 if x is lesser than y, 0 otherwise.
 lte(x, y)
 Return 1 if x is lesser than or equal to y, 0 otherwise.
 max(x, y)
 Return the maximum between x and y.
 min(x, y)
 Return the minimum between x and y.
 mod(x, y)
 Compute the remainder of division of x by y.
 not(expr)
 Return 1.0 if expr is zero, 0.0 otherwise.
 pow(x, y)
 Compute the power of x elevated y, it is equivalent to "(x)^(y)".
 print(t)
 print(t, l)

Print the value of expression t with loglevel l. If
l is not specified then a default log level is used.
Returns the value of the expression printed.
Prints t with loglevel l
 random(x)
 Return a pseudo random value between 0.0 and 1.0. x is the index of the internal variable which will be used to save the seed/state.
 root(expr, max)

Find an input value for which the function represented by expr
with argument ld(0) is 0 in the interval 0..max.
The expression in expr must denote a continuous function or the result is undefined.
ld(0) is used to represent the function input value, which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(0). When the expression evaluates to 0 then the corresponding input value will be returned.
 sin(x)
 Compute sine of x.
 sinh(x)
 Compute hyperbolic sine of x.
 sqrt(expr)
 Compute the square root of expr. This is equivalent to "(expr)^.5".
 squish(x)
 Compute expression "1/(1 + exp(4*x))".
 st(var, expr)
 Store the value of the expression expr in an internal variable. var specifies the number of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable. Note, Variables are currently not shared between expressions.
 tan(x)
 Compute tangent of x.
 tanh(x)
 Compute hyperbolic tangent of x.
 taylor(expr, x)
 taylor(expr, x, id)

Evaluate a Taylor series at x, given an expression representing
the "ld(id)"th derivative of a function at 0.
When the series does not converge the result is undefined.
ld(id) is used to represent the derivative order in expr, which means that the given expression will be evaluated multiple times with various input values that the expression can access through "ld(id)". If id is not specified then 0 is assumed.
Note, when you have the derivatives at y instead of 0, "taylor(expr, xy)" can be used.
 time(0)
 Return the current (wallclock) time in seconds.
 trunc(expr)
 Round the value of expression expr towards zero to the nearest integer. For example, ``trunc(1.5)'' is ``1.0''.
 while(cond, expr)
 Evaluate expression expr while the expression cond is nonzero, and returns the value of the last expr evaluation, or NAN if cond was always false.
The following constants are available:
 PI
 area of the unit disc, approximately 3.14
 E
 exp(1) (Euler's number), approximately 2.718
 PHI
 golden ratio (1+sqrt(5))/2, approximately 1.618
Assuming that an expression is considered ``true'' if it has a nonzero value, note that:
"*" works like AND
"+" works like OR
For example the construct:
if (A AND B) then C
is equivalent to:
if(A*B, C)
In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions.
The evaluator also recognizes the International System unit prefixes. If 'i' is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The 'B' postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as number postfix.
The list of available International System prefixes follows, with indication of the corresponding powers of 10 and of 2.
 y
 10^24 / 2^80
 z
 10^21 / 2^70
 a
 10^18 / 2^60
 f
 10^15 / 2^50
 p
 10^12 / 2^40
 n
 10^9 / 2^30
 u
 10^6 / 2^20
 m
 10^3 / 2^10
 c
 10^2
 d
 10^1
 h
 10^2
 k
 10^3 / 2^10
 K
 10^3 / 2^10
 M
 10^6 / 2^20
 G
 10^9 / 2^30
 T
 10^12 / 2^40
 P
 10^15 / 2^40
 E
 10^18 / 2^50
 Z
 10^21 / 2^60
 Y
 10^24 / 2^70
OPENCL OPTIONS
When FFmpeg is configured with "enableopencl", it is possible to set the options for the global OpenCL context.The list of supported options follows:
 build_options

Set build options used to compile the registered kernels.
See reference ``OpenCL Specification Version: 1.2 chapter 5.6.4''.
 platform_idx

Select the index of the platform to run OpenCL code.
The specified index must be one of the indexes in the device list which can be obtained with "ffmpeg opencl_bench" or "av_opencl_get_device_list()".
 device_idx

Select the index of the device used to run OpenCL code.
The specified index must be one of the indexes in the device list which can be obtained with "ffmpeg opencl_bench" or "av_opencl_get_device_list()".
AUTHORS
The FFmpeg developers.For details about the authorship, see the Git history of the project (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <http://source.ffmpeg.org>.
Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.