ffmpegutils
FFmpeg utilities
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 dAmour
containing the special character: Crime d\AmourThe 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>...][smsus]
S expresses the number of seconds, with the optional decimal part m. The optional literal suffixes s, ms or us indicate to interpret the value as seconds, milliseconds or microseconds, respectively.
In both expressions, the optional  indicates negative duration.
Examples
The following examples are all valid time duration:
55 seconds
0.2 seconds
 200ms

200 milliseconds, that's 0.2s
 200000us

200000 microseconds, that's 0.2s
 12:03:45

12 hours, 03 minutes and 45 seconds
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
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
FL+FR+LFE
FL+FR+FC
FL+FR+BC
FL+FR+FC+BC
 quad

FL+FR+BL+BR
 quad(side)

FL+FR+SL+SR
FL+FR+FC+LFE
FL+FR+FC+BL+BR
FL+FR+FC+SL+SR
FL+FR+FC+LFE+BC
FL+FR+FC+LFE+BL+BR
FL+FR+FC+LFE+SL+SR
FL+FR+FC+BC+SL+SR
FL+FR+FLC+FRC+SL+SR
 hexagonal

FL+FR+FC+BL+BR+BC
FL+FR+FC+LFE+BC+SL+SR
FL+FR+FC+LFE+BL+BR+BC
FL+FR+LFE+FLC+FRC+SL+SR
FL+FR+FC+BL+BR+SL+SR
FL+FR+FC+FLC+FRC+SL+SR
FL+FR+FC+LFE+BL+BR+SL+SR
FL+FR+FC+LFE+BL+BR+FLC+FRC
FL+FR+FC+LFE+FLC+FRC+SL+SR
 octagonal

FL+FR+FC+BL+BR+BC+SL+SR
 hexadecagonal

FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
 downmix

DL+DR
FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
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, followed by 'c', yielding the default channel layout for that number of channels (see the function
av_get_default_channel_layout
). Note that not all channel counts have a default layout.a number of channels, in decimal, followed by 'C', yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts.
a channel layout mask, in hexadecimal starting with 0x (see the
AV_CH_*
macros in libavutil/channel_layout.h.
Before libavutil version 53 the trailing character c to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by c or 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.
 atan2(x, y)

Compute principal value of the arc tangent of y/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.
 lerp(x, y, z)

Return linear interpolation between x and y by amount of z.
 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.  round(expr)

Round the value of expression expr to the nearest integer. For example, round(1.5) is 2.0.
 sgn(x)

Compute sign of x.
 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
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.
10^24 / 2^80
10^21 / 2^70
10^18 / 2^60
10^15 / 2^50
10^12 / 2^40
10^9 / 2^30
10^6 / 2^20
10^3 / 2^10
10^2
10^1
10^2
10^3 / 2^10
10^3 / 2^10
10^6 / 2^20
10^9 / 2^30
10^12 / 2^40
10^15 / 2^40
10^18 / 2^50
10^21 / 2^60
10^24 / 2^70
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.
SEE ALSO
ffmpeg (1), ffplay (1), ffprobe (1), libavutil (3)