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FFMPEG-UTILS(1) 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: | |
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. | |
Examples | |
o Escape the string "Crime d'Amour" 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 | |
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 | |
3.1.2 | |
FL+FR+FC+LFE+TFL+TFR | |
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 | |
5.1.2 | |
FL+FR+FC+LFE+BL+BR+TFL+TFR | |
octagonal | |
FL+FR+FC+BL+BR+BC+SL+SR | |
cube | |
FL+FR+BL+BR+TFL+TFR+TBL+TBR | |
5.1.4 | |
FL+FR+FC+LFE+BL+BR+TFL+TFR+TBL+TBR | |
7.1.2 | |
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR | |
7.1.4 | |
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBL+TBR | |
7.2.3 | |
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBC+LFE2 | |
9.1.4 | |
FL+FR+FC+LFE+BL+BR+FLC+FRC+SL+SR+TFL+TFR+TBL+TBR | |
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: | |
o 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: | |
o the name of a single channel (e.g. FL, FR, FC, LFE, etc.) | |
o the name of a standard channel layout (e.g. mono, stereo, 4.0, | |
quad, 5.0, 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_channel_layout_default"). 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_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(y, x) | |
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(idx) | |
Return a pseudo random value between 0.0 and 1.0. idx is the index | |
of the internal variable which will be used to save the seed/state. | |
randomi(idx, min, max) | |
Return a pseudo random value in the interval between min and max. | |
idx 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 / 2^50 | |
E 10^18 / 2^60 | |
Z 10^21 / 2^70 | |
Y 10^24 / 2^80 | |
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. | |
FFMPEG-UTILS(1) | |