# ffmpeg-utils

## 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:

[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((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 year-month-day part is not specified it takes the current year-month-day.

## 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 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 *width*x*height*, 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

- ntsc-film
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

- ntsc-film
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 multi-channel 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 left-of-center

- FRC
front right-of-center

- 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

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 non-zero return the result of the evaluation of*y*, return 0 otherwise.- if(x, y, z)
Evaluate

*x*, and if the result is non-zero 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 argumentis 0 in the interval 0..**ld**(0)*max*. The expression in*expr*must denote a continuous function or the result is undefined.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)`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, x-y)`

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 non-zero, 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 non-zero 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)