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Tools for transcoding, streaming and playing of multimedia files


Library for working with various multimedia formats


Library for working with various multimedia formats


ffmpeg-utils - FFmpeg utilities


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


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:
o 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.
o A special character is escaped by prefixing it with a \.
o 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.
o 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.
o Escape the string Crime dAmour containing the special character:
        Crime d\Amour

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

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

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

o To include a literal \ you can use either escaping or quoting:
        c:\foo can be written as c:\\foo


The accepted syntax is:
        [(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]

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 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.

S expresses the number of seconds, with the optional decimal part m.
In both expressions, the optional - indicates negative duration.
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
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


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.


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
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
3.0 FL+FR+FC
3.0(back) FL+FR+BC
quad FL+FR+BL+BR
quad(side) FL+FR+SL+SR
5.0(side) FL+FR+FC+SL+SR
5.1(side) FL+FR+FC+LFE+SL+SR
6.0(front) FL+FR+FLC+FRC+SL+SR
hexagonal FL+FR+FC+BL+BR+BC
6.1(front) FL+FR+LFE+FLC+FRC+SL+SR
7.0(front) FL+FR+FC+FLC+FRC+SL+SR
7.1(wide-side) 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:
o the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.)
o the name of a single channel (e.g. FL, FR, FC, LFE, etc.)
o 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.
o 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.
o 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.


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, 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.
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


The FFmpeg developers.
For details about the authorship, see the Git history of the project (git://, e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <>.
Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.
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