FFMPEG-UTILS(1)

NAME
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 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:

        [(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|ms|us]

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  55 seconds

0.2 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
    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

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

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(wide-side)
    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

22.2
    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 '+'. Each term can be:

•   the name of a single channel (e.g. FL, FR, FC, LFE, etc.), each optionally containing a custom name after a '@', (e.g. FL@Left, FR@Right, FC@Center, LFE@Low_Frequency, etc.)

A standard channel layout can be specified by the following:

•   the name of a single channel (e.g. FL, FR, FC, LFE, etc.)

•   the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.)

•   a number of channels, in decimal, followed by 'c', yielding the default channel layout for that number of channels (see the function "av_channel_layout_default"). 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_channel_layout_from_string" 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 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, 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

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 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.

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

SEE ALSO
ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3)

AUTHORS
The FFmpeg developers.

For details about the authorship, see the Git history of the project (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <https://git.ffmpeg.org/ffmpeg>.

Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.