Internal functions

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In addition to internal filters AviSynth has a fairly large number of other (non-clip) internal functions.

The input or/and output of these functions are not clips, but some other variables which can be used in a script.

Contents


Boolean functions

These return true or false, if the condition that they test holds or not, respectively.
IsBool
IsBool(var)  
Tests if var is of the bool type. var can be any expression allowed by the AviSynth Syntax.

Examples:

b = false
IsBool(b) = true
IsBool(1 < 2 && 0 == 1) = true
IsBool(123) = false
IsClip
IsClip(var)  
Tests if var is of the clip type. var can be any expression allowed by the AviSynth Syntax.

Examples:

c = AviSource(...)
IsClip(c) = true
IsClip("c") = false
IsFloat
IsFloat(var)  
Tests if var is of the float type. var can be any expression allowed by the AviSynth Syntax.

Examples:

f = Sqrt(2)
IsFloat(f) = true
IsFloat(2) = true   # ints are considered to be floats by this function
IsFloat(true) = false
IsInt
IsInt(var)  
Tests if var is of the int type. var can be any expression allowed by the AviSynth Syntax.

Examples:

IsInt(2) = true
IsInt(2.1) = false
IsInt(true) = false
IsString
IsString(var)  
Tests if var is of the string type. var can be any expression allowed by the AviSynth Syntax.

Examples:

IsString("test") = true
IsString(2.3) = false
IsString(String(2.3)) = true
Exist
Exist(filename)  
Tests if the file specified by filename exists.

Examples:

filename = ...
clp = Exist(filename) 
\ ? AviSource(filename) 
\ : Assert(false, "file: " + filename + " does not exist")
Defined
Defined(var)  
Tests if var is defined. Can be used inside Script_functions to test if an optional argument has been given an explicit value.
More formally, the function returns false if its argument (normally a function argument or variable) has the void ('undefined') type, otherwise it returns true.

Examples:

b_arg_supplied = Defined(arg)
myvar = b_arg_supplied ? ... : ...


Control functions

These facilitate flow of control (loading of scripts, arguments checks, global settings adjustment, etc.).
Apply
Apply(string func_string [, arg1 [, arg2 [, ... [, argn]]]] )  
Calls the function or filter func_string with arguments arg1, arg2, ..., argn (as many as supplied). Thus, it provides a way to call a function or filter by name providing arguments in the usual way as in a typical function call.
Consequently, Apply("f", x) is equivalent to f(x) which in turn is equivalent to Eval("f(" + String(x) + ")").

Examples:

# here the same call to BicubicResize as in the Eval() example is shown 
Apply("BicubicResize", last, 352, 288)
# Note that the clip argument must be supplied - 'last' is not implicitly assumed
Eval
Eval(expression [, string name])  
Evaluates an arbitrary expression as if it was placed inside the script at the point of the call and returns the result of evaluation (either to the variable that is explicitly assigned to or to the Last special variable.
You can use Eval to construct and evaluate expressions dynamically inside your scripts, based on variable input data. Below some specific examples are shown but you get the general idea.
Argument name will be shown in the error message besides the script name. Both will be followed with the line number in the script where the is error caused.

Examples:

# calls BicubicResize(last, 352, 288)
settings = "352, 288"
Eval( "BicubicResize(" + settings + ")" )

# results in Defined(u) == false
u = Eval("#")   

# increments a global based on a variable's value
Eval("global my_counter = my_counter + " + String(increment)) 

# multi-line example with comment and line continuation
Eval("""
ColorBars
BicubicResize(352, 288)
#FlipVertical
Subtitle(
\   "Width  = "  + String(Width) + "\n"
\ + "Height = " + String(Height)
\ , align=7, lsp=0)
""")
Import
Import(filename)  
Evaluates the contents of another script and returns that script's return value. Typically it is used to make available to the calling script library functions and the return value is not used. However this is simply a convention; it is not enforced by the AviSynth Syntax. See also the dedicated Import page in Internal filters for other possible uses.
Possible scenarios (an indicative list) where the return value could be of use is for the library script to:
  • indicate whether it succesfully initialised itself (a bool return value),
  • inform for the number of presets found on disk (an int return value);
the value then could be tested by the calling script to decide what action to take next.

Examples:

# here we do not care about the value (mylib.avsi contains only functions)
Import("mylib.avsi")  
...
# mysources.avsi loads predetermined file names from a folder into globals
okflag = Import("mysources.avsi")  
source = okflag ? global1 + global2 + global3 : BlankClip()
Select
Select(index, item0 [, item1 [, ...[, itemn]]])  
Returns the item selected by the index argument, which must be of int type (0 returns item0, 1 returns item1, ..., etc). Items can be any script variable or expression of any type and can even be mixed.
If index is out of range, an error is raised.

Examples:

# select a clip-brush from a set of presets
idx = 2
brush = Select(idx, AviSource("round.avi"), 
\        rectangle, diagonal, diagonal.FlipHorizontal)

Note - all branches are evaluated:

index=1
Select(index, "zero", "one", "two", 
\        Assert(false, "Select evaluates all branches")) 
## NOTE this code does not run - it throws Assert error
## because Select evaluates all branches

If this is not desired, use the conditional execution operator:

index=1
x = (index==0) ? "zero"
\ : (index==1) ? "one"
\ : (index==2) ? "two"
\ : Assert(false, "index out of range")
Default
Default(x, d)  
Returns x if Defined(x) is true, d otherwise. x must either be a function's argument or an already declared script variable (ie a variable which has been assigned a value) else an error will occur.

Examples:

function myfunc(clip c, ..., int "strength") {
    ...
    strength = Default(strength, 4) # if not supplied make it 4
    ...
}
Assert
Assert(condition [, err_msg])  
Does nothing if condition is true; throws an error, immediately terminating script execution, if condition is false. In the later case err_msg, if supplied, is presented to the user through a dialog box; else the standard message "Assert: assertion failed" shows up.

Examples:

function myfunc(clip c, ..., int "strength") {
    ...
    strength = Default(strength, 4) # if not supplied make it 4
    Assert(strength > 0, "'strength' must be positive")
    ...
}
NOP
NOP()  
This is a no-operation function provided mainly for conditional execution with non-return value items such as Import, when no "else" condition is desired. That is, use it whenever the AviSynth Syntax requires an operation (such as with the ?: operator) but your script does not need one.
Return value: 0 (int type).

Examples:

preset = want_presets ? AviSource("c:\presets\any.avi") : NOP
... 
loadlib ? Import("my_useful_functions.avs") : NOP
Undefined
Undefined()   v2.60
Returns the undefined state.
It's the state for which Defined() returns false.

Examples:

x = Undefined()
Defined(x) # == false


Global Options

SetMemoryMax
SetMemoryMax(amount)  
Sets the maximum memory that AviSynth uses (in MB) to the value of amount. Setting to zero just returns the current Memory Max value. In the 2.5 series the default Memory Max value is 25% of the free physical memory, with a minimum of 16MB.
The default Memory Max is also limited to 512MB.
Free memory <64 128 256 512 1024 2048 3072
Default Max 16 32 64 192 448 512 512
In some versions there is a default setting of 5MB, which is quite low. If you encounter problems (e.g. low speed) try to set this values to at least 32MB. Too high values can result in crashes because of 2GB address space limit.
Return value: Actual MemoryMax value set.

Examples:

SetMemoryMax(128)
SetWorkingDir
SetWorkingDir(path)  
Sets the default directory for AviSynth to the path argument.
This is primarily for easy loading of source clips, importing scripts, etc. It does not affect plugins' autoloading.
Return value is 0 if successful, -1 otherwise.

Examples:

SetWorkingDir("c:\my_presets")
AviSource("border_mask.avi")  # this loads c:\my_presets\border_mask.avi
SetPlanarLegacyAlignment
SetPlanarLegacyAlignment(mode)  
Set alignment mode for planar frames. mode can either be true or false.
Some older plugins illegally assume the layout of video frames in memory. This special filter forces the memory layout of planar frames to be compatible with prior versions of AviSynth. The filter works on the GetFrame() call stack, so it effects filters before it in the script.

Examples:

Example : Using an older version of Mpeg2Source() (1.10 or older):

LoadPlugin("...\Mpeg2Decode.dll")
Mpeg2Source("test.d2v")         # A plugin that illegally assumes the layout of memory
SetPlanarLegacyAlignment(true)  # Set legacy memory alignment for prior statements
ConvertToYUY2()     # Statements through to the end of the script have
...                             # advanced memory alignment.
OPT_AllowFloatAudio
global OPT_AllowFloatAudio = True  
This option enables WAVE_FORMAT_IEEE_FLOAT audio output. The default is to autoconvert Float audio to 16 bit.
OPT_UseWaveExtensible
global OPT_UseWaveExtensible = True  
This option enables WAVE_FORMAT_EXTENSIBLE audio output. The default is WAVE_FORMAT_EX.
Note: The default DirectShow component for .AVS files, "AVI/WAV File Source", does not correctly implement WAVE_FORMAT_EXTENSIBLE processing, so many application may not be able to detect the audio track. There are third party DirectShow readers that do work correctly. Intermediate work files written using the AVIFile interface for later DirectShow processing will work correctly if they use the DirectShow "File Source (async)" component or equivalent.
OPT_VDubPlanarHack
global OPT_VDubPlanarHack = True   v2.60
This option enables flipped YV24 and YV16 chroma planes. This is an hack for early versions of Virtualdub with YV24/YV16 support.
OPT_dwChannelMask
global OPT_dwChannelMask(int v)   v2.60
This option enables you to set ChannelMask. It overrides WAVEFORMATEXTENSIBLE.dwChannelMask[[1] which is set according to this table
0x00004, // 1   -- -- Cf
0x00003, // 2   Lf Rf
0x00007, // 3   Lf Rf Cf
0x00033, // 4   Lf Rf -- -- Lr Rr
0x00037, // 5   Lf Rf Cf -- Lr Rr
0x0003F, // 5.1 Lf Rf Cf Sw Lr Rr
0x0013F, // 6.1 Lf Rf Cf Sw Lr Rr -- -- Cr
0x0063F, // 7.1 Lf Rf Cf Sw Lr Rr -- -- -- Ls Rs
OPT_AVIPadScanlines
global OPT_AVIPadScanlines = True   v2.60
This option enables DWORD aligned planar padding. Default is packed aligned planar padding. See memory alignment used in the AVIFile output emulation.


Conversion functions

These convert between different types.
Value
Value(string)  
Converts a decimal string to its associated numeric value.

Examples:

Value ("-2.7") = -2.7
HexValue
HexValue(string)  
Converts a hexadecimal string to its associated numeric value.

Examples:

HexValue ("FF00") = 65280
Hex
Hex(int)   v2.60
Converts a numerical value to its hexadecimal value. See Colors for more information on specifying colors.

Examples:

Hex (10824234) = "A52A2A"
String
String(var [, string format_string])  
Converts a variable to a string. String arguments are passed along unchanged; booleans are converted to "true" or "false"; numbers (ints or floats) are formatted as described below; all other value types are converted to the empty string.
If the variable is float or integer, it first converts it to a float and then uses format_string to convert the float to a string.
The syntax of format_string is as follows:
%[flags][width][.precision]f
flags
- left align (instead right align)
+ always print the +/- sign
0 padding with leading zeros
' ' print a blank instead of a "+"
# always print the decimal point
width
the minimum width (the string is never truncated)
precision
the number of digits printed
You can also put arbitrary text around the format_string as defined above, similar to the C-language sprintf function.

Examples:

Subtitle( "Clip height is " + String(last.height) )

Subtitle( String(1.23, "%f" ))              # '1.23'
Subtitle( String(1.23, "%5.1f") )           # '  1.2'
Subtitle( String(1.23, "%1.3f") )           # '1.230'
Subtitle( String(24, "%05.0f") )            # '00024'

Subtitle( "PI=" + String(PI, "%0.0f") )     # "PI=3"
Subtitle( "PI=" + String(PI, "%2.0f") )     # "PI= 3"
Subtitle( "PI=" + String(PI, "%3.2f") )     # "PI=3.14"
Subtitle( "PI=" + String(PI, "%0.5f") )     # "PI=3.14159"
Subtitle( "PI=" + String(PI, "%6.3f") )     # "PI= 3.142"

Subtitle( "'" + String(32, "%0f") + "'" )   # '32.000000'
Subtitle( "'" + String(32, "%0.0f") + "'" ) # '32'
Subtitle( "'" + String(32, "%3.0f") + "'" ) # ' 32'
Subtitle( "'" + String(32, "%8.0f") + "'" ) # '      32'

# arbitrary text around format_string:
Subtitle( String(PI(), "PI = %1.5f (more or less)") ))
# another example of arbitrary text:
Subtitle( String(x, "Value of x is %.3f after AR calc") )
# same output as above but using string concatenation:
Subtitle( "Value of x is " + String(x, "%.3f") + " after AR calc") ) 


Numeric functions

These provide common mathematical operations on numeric variables.
Max
Max(float, float [, ...])  
Returns the maximum value of a set of numbers.
If all the values are of type Int, the result is an Int. If any of the values are of type Float, the result is a Float.
This may cause an unexpected result when an Int value greater than 16777216 is mixed with Float values.

Examples:

Max (1, 2) = 2
Max (5, 3.0, 2) = 5.0
Min
Min(float, float [, ...])  
Returns the minimum value of a set of numbers.

Examples:

Min (1, 2) = 1
Min (5, 3.0, 2) = 2.0
MulDiv
MulDiv(int, int, int)  
Multiplies two ints (m, n) and divides the product by a third (d) in a single operation, with 64 bit intermediate result. The actual equation used is (m * n + d / 2) / d .

Examples:

MulDiv (1, 1, 2) = 1
MulDiv (2, 3, 2) = 3
Floor
Floor(float)  
Converts from single-precision, floating-point value to int (round down on any fractional amount).

Examples:

Floor(1.2) = 1
Floor(1.6) = 1
Floor(-1.2) = -2
Floor(-1.6) = -2
Ceil
Ceil(float)  
Converts from single-precision, floating-point value to int (round up on any fractional amount).

Examples:

Ceil(1.2) = 2
Ceil(1.6) = 2
Ceil(-1.2) = -1
Ceil(-1.6) = -1
Round
Round(float)  
Converts from single-precision, floating-point value to int (round off to nearest integer).

Examples:

Round(1.2) = 1
Round(1.6) = 2
Round(-1.2) = -1
Round(-1.6) = -2
Int
Int(float)  
Converts from single-precision, floating-point value to int (round towards zero).

Examples:

Int(1.2) = 1
Int(1.6) = 1
Int(-1.2) = -1
Int(-1.6) = -1
Float
Float(int)  
Converts int to single-precision, floating-point value. Integer values that require more than 24-bits to be represented will have their lower 8-bits truncated yielding unexpected values.

Examples:

Float(4) = 4.0
Float(4) / 3 = 1.333 (while 4 / 3 = 1 , due to integer division)
Float(123456789) = 123456792.0 (error = -3, 0.000002%)
Float(1234567890) = 1234567936.0 (error = -46, 0.000004%)
Fmod
Fmod(float, float)   v2.60
Returns the modulo of the argument. Output is float.

Examples:

Fmod(3.5, 0.5) = 0 (since 3.5 - 7*0.5 = 0)
Fmod(3.5, 1.0) = 0.5 (since 3.5 - 3*1.0 = 0.5)
Pi
Pi()  
Returns the value of the π constant (the ratio of a circle's circumference to its diameter).

Examples:

d = Pi()    # d == 3.141592653
Exp
Exp(float)  
Returns the natural (base-e) exponent of the argument.

Examples:

Exp(1) = 2.7182818
Exp(0) = 1.0
Log
Log(float)  
Returns the natural (base-e) logarithm of the argument.

Examples:

Log(1) = 0.0
Log(10) = 2.30259
Log(Exp(1)) = 1.0
Log10
Log10(float)   v2.60
Returns the common logarithm of the argument.

Examples:

Log10(1.0) = 0
Log10(10.0) = 1.0
Log10(2.0) = 0.3010299957
Pow
Pow(float base, float power)  
Returns base raised to a power.

Examples:

Pow(2, 3) = 8
Pow(3, 2) = 9
Pow(3.45, 1.75) = 8.7334
Sqrt
Sqrt(float)  
Returns the square root of the argument.

Examples:

Sqrt(1) = 1.0
Sqrt(2) = 1.4142
Abs
Abs(float or int)  
Returns the absolute value of its argument (returns float for float, integer for integer).

Examples:

Abs(-3.8) = 3.8
Abs(-4) = 4
Sign
Sign(float)  
Returns the sign of the value passed as argument (1, 0 or -1).

Examples:

Sign(-3.5) = -1
Sign(3.5) = 1
Sign(0) = 0
Frac
Frac(float)  
Returns the fractional portion of the value provided.

Examples:

Frac(3.7) = 0.7
Frac(-1.8) = -0.8
Rand
Rand([int max] [, bool scale] [, bool seed])  
Returns a random integer value. All parameters are optional.
max
sets the maximum value+1 (default 32768) and can be set negative for negative results. It operates either in scaled or modulus mode (default scale=true only if Abs(max) > 32768, false otherwise).
scale
When true, scales the internal random number generator value to the maximum value, while modulus mode (scale=false) uses the remainder from an integer divide of the random generator value by the maximum. Modulus mode is recommended for smaller maximums.
seed
When true, seeds the random number generator with the current time. seed defaults to false and probably isn't necessary, although it's there just in case.
Typically, this function would be used with the Select function for random clips.

Examples:

Select(Rand(5), clip1, clip2, clip3, clip4, clip5)
Spline
Spline(float X, x1, y1, x2, y2, .... [, bool cubic])  
Interpolates the Y value at point X using the control points x1/y1, ... There have to be at least 2 x/y-pairs. The interpolation can be cubic (the result is a spline) or linear (the result is a polygon). Default is cubic.

Examples:

Spline(5, 0, 0, 10, 10, 20, 0, false) = 5
Spline(5, 0, 0, 10, 10, 20, 0, true) = 7
Continued Numerator, Denominator
ContinuedNumerator(float, int limit)   v2.60
ContinuedNumerator(int, int, int limit)   v2.60
ContinuedDenominator(float, int limit)   v2.60
ContinuedDenominator(int, int, int limit)   v2.60
The rational pair (ContinuedNumerator, ContinuedDenominator) returned has the smallest possible denominator such that the absolute error is less than 1/limit. More information can be found on wikipedia.
If limit is not specified in the Float case the rational pair returned is to the limit of the single precision floating point value. Thus (float)((double)Num/(double)Den) == V.
In the Int case if limit is not specified then the normalized original values will be returned, i.e. reduced by the GCD (greatest common divisor).

Examples:

ContinuedNumerator(PI(), limit=5000]) = 355
ContinuedDenominator(PI(), limit=5000) = 113

ContinuedNumerator(PI(), limit=50]) = 22
ContinuedDenominator(PI(), limit=50) = 7

ContinuedNumerator(355, 113, limit=50]) = 22
ContinuedDenominator(355, 113, limit=50) = 7


Trigonometry functions

relationships involving lengths and angles of triangles.
Sin
Sin(float)  
Returns the sine of the argument (assumes it is radians).

Examples:

Sin(Pi()/4) = 0.707
Sin(Pi()/2) = 1.0
Cos
Cos(float)  
Returns the cosine of the argument (assumes it is radians).

Examples:

Cos(Pi()/4) = 0.707
Cos(Pi()/2) = 0.0
Tan
Tan(float)   v2.60
Returns the tangent of the argument (assumes it is radians).

Examples:

Tan(Pi/4) = 1.0
Tan(Pi/2) = not defined
32 bit IEEE floats do not have sufficient resolution to exactly represent
pi/2 so AviSynth returns a large positive number for the value slightly less
than pi/2 and a large negative value for the next possible value which is
slightly greater than pi/2.
Asin
Asin(float)   v2.60
Returns the inverse of the sine of the argument (output is radians).

Examples:

Asin(0.707) = 0.7852471634 (~ Pi/4)
Asin(1.0) = 1.570796327 (~ Pi/2)
Acos
Acos(float)   v2.60
Returns the inverse of the cosine of the argument (output is in radians).

Examples:

Acos(0.707) = 0.7852471634 (~ Pi/4)
Acos(0.0) = 1.570796327 (~ Pi/2)
Atan
Atan(float)   v2.60
Returns the inverse of the tangent of the argument (output is in radians).

Examples:

Atan(0.707) = 0.6154085176
Atan(1.0) = 0.7853981634 (~ Pi/4)
Atan2
Atan2(float, float)   v2.60
Returns the angle between the positive x-axis of a plane and the point given by the coordinates (x, y) on it. Output is in radians. See wikipedia for more information.
y is the first argument and x is the second argument.

Examples:

Atan2(1.0, 0) = 1.570796327 (~ Pi/2)
Atan2(1.0, 1.0) = 0.7852471634 (~ Pi/4)
Atan2(-1.0, -1.0) = -2.356194490 (~ -3Pi/4)
Sinh
Sinh(float)   v2.60
Returns the hyperbolic sine of the argument. See wikipedia for more information.

Examples:

Sinh(2.0) = 3.626860408
Cosh
Cosh(float)   v2.60
Returns the hyperbolic cosine of the argument.

Examples:

Cosh(2.0) = 3.762195691
Tanh
Tanh(float)   v2.60
Returns the hyperbolic tangent of the argument.

Examples:

Tanh(2.0) = 0.9640275801


Bit functions

The functions are bitwise operators. They manipulate individual bits within integer variables. This means that their arguments (being integers) are converted to binary numbers, the operation is performed on their bits, and the resulting binary number is converted back again.
BitAnd
BitAnd(int, int)   v2.60
Returns the bitwise AND (sets bit to 1 if both bits are 1 and sets bit to 0 otherwise).

Examples:

BitAnd(5, 6) = 4 # since 5 = 101, 6 = 110, and 101&110 = 100
BitNot
BitNot(int)   v2.60
Returns the bit-inversion (sets bit to 1 if bit is 0 and vice-versa).

Examples:

BitNOT(5) = -6 
# since  5 = 101,  
# and ~101 = 1111 1111 1111 1111 1111 1111 1111 1010 = -6
Note: 1111 1111 1111 1111 1111 1111 1111 1010
= (2^32-1)-2^0-2^2 = 2^32-(1+2^0+2^2)
= (signed) -(1+2^0+2^2) = -6
BitOr
BitOr(int, int)   v2.60
Returns the bitwise inclusive OR (sets bit to 1 if one of the bits (or both) is 1 and sets bit to 0 otherwise).

Examples:

BitOr(5, 6) = 7 # since 5 = 101, 6 = 110, and 101|110 = 111
BitOr(4, 2) = 6 # since 4 = 100, 2 = 010, and 100|010 = 110
BitXor
BitXor(int, int)   v2.60
Returns the bitwise exclusive OR (sets bit to 1 if exactly one of the bits is 1 and sets bit to 0 otherwise).

Examples:

BitXor(5, 6) = 3 # since 5 = 101, 6 = 110, and 101^110 = 011
BitXor(4, 2) = 6 # since 4 = 100, 2 = 010, and 100^010 = 110
Bit shift left
BitLShift(int, int)   v2.60
BitShl(int, int)   v2.60
BitSal(int, int)   v2.60
Shift the bits of a number to the left.

Examples:

Shifts the bits of the number 5 two bits to the left:
BitLShift(5, 2) = 20 (since 101 << 2 = 10100)
Bit shift right
BitRShiftA(int, int)   v2.60
BitRShiftS(int, int)   v2.60
BitSar(int, int)   v2.60
Shift the bits of an integer to the right. (Arithmetic, Sign bit fill, Right Shift)

Examples:

Shifts the bits of the number -42 one bit to the right, treating it as signed:
BitRShiftA(-42, 1) = -21 
# (since 1111 1111 1111 1111 1111 1111 1101 0110 >> 1  
#      = 1111 1111 1111 1111 1111 1111 1110 1011)
Bit shift right, unsigned
BitRShiftL(int, int)   v2.60
BitRShiftU(int, int)   v2.60
BitShr(int, int)   v2.60
Shift the bits of an unsigned integer to the right. (Logical, zero fill, Right Shift)

Examples:

Shifts the bits of the number -42 one bit to the right, treating it as unsigned:
BitRShiftL(-42, 1) = 2147483627 
# (since 1111 1111 1111 1111 1111 1111 1101 0110 >> 1 
#      = 0111 1111 1111 1111 1111 1111 1110 1011)
Note: -42 = -(1+2^0+2^3+2^5) = (unsigned) (2^32-1)-(2^0+2^3+2^5) =
1111 1111 1111 1111 1111 1111 1101 0110
Bit rotate left
BitLRotate(int, int)   v2.60
BitRol(int, int)   v2.60
Rotates the bits of an integer to the left by the number of bits specified in the second operand. For each rotation specified, the high order bit that exits from the left of the operand returns at the right to become the new low order bit.

Examples:

Rotates the bits of the number -2147483642 one bit to the left:
BitLRotate(-2147483642, 1) = 13 
# (since 10000000000000000000000000000110 ROL 1
#      = 00000000000000000000000000001101)
Bit rotate right
BitRRotateL(int, int)   v2.60
BitRor(int, int)   v2.60
Rotates the bits of an integer to the right by the number of bits specified in the second operand. For each rotation specified, the low order bit that exits from the right of the operand returns at the left to become the new high order bit.

Examples:

Rotates the bits of the number 13 one bit to the right:
BitRRotate(13, 1) = -2147483642 
# (since 00000000000000000000000000001101 ROR 1 
#      = 10000000000000000000000000000110)
Bit test
BitTest(int, int)   v2.60
BitTst(int, int)   v2.60
Tests a single bit (that is, it returns true if its state is one, else it returns false). The second operand denotes the location of the bit which is specified as an offset from the low order end of the operand (starting at zero).

Examples:

Check the state of the fourth bit:
BitTest(3, 4) = False
BitTest(19, 4) = True

Check the state of the sign bit:
BitTest(-1, 31) = True
BitTest(2147483647, 31) = False
BitSet
BitSet(int, int)   v2.60
Sets a single bit to one (so it sets its state to one). The second operand denotes the location of the bit which is specified as an offset from the low order end of the operand (starting at zero).

Examples:

Set the state of the fourth bit to one:
BitSet(3, 4) = 19
BitSet(19, 4) = 19

Set the state of the sign bit to one:
BitSet(-1, 31) = -1
BitSet(2147483647, 31) = -1
Bit clear
BitClear(int, int)   v2.60
BitClr(int, int)   v2.60
Sets a single bit to zero (so it sets its state to zero). The second operand denotes the location of the bit which is specified as an offset from the low order end of the operand (starting at zero).

Examples:

Clear the bits of the number 5
BitClear(5, 0) = 4 (first bit is set to zero)
BitClear(5, 1) = 5 (second bit is already zero)
BitClear(5, 2) = 1 (third bit is set to zero)
BitClear(5, 3) = 5 (fourth bit is already zero)

Clear the state of the sign bit:
BitClear(-1, 31) = 2147483647
Bit change
BitChange(int, int)   v2.60
BitChg(int, int)   v2.60
Sets a single bit to its complement (so it changes the state of a single bit; 1 becomes 0 and vice versa). The second operand denotes the location of the bit which is specified as an offset from the low order end of the operand (starting at zero). The sign bit is bit 31.

Examples:

Change the state of the a bit of the number 5:
BitChange(5, 0) = 4 (first bit is set to zero)
BitChange(5, 1) = 7 (second bit is set to one)
BitChange(5, 2) = 1 (third bit is set to zero)
BitChange(5, 3) = 13 (fourth bit is set to one)

Change the state of the sign bit:
BitChange(-1, 31) = 2147483647


Runtime functions

These are internal functions which are evaluated at every frame. They can be used inside the scripts passed to runtime filters (ConditionalFilter, ScriptClip, FrameEvaluate) to return information for a frame.
Average
AverageLuma(clip [, int offset = 0])  
AverageChromaU(clip [, int offset = 0])  
AverageChromaV(clip [, int offset = 0])  
This group of functions return a float value with the average pixel value of a plane (Luma, U-chroma and V-chroma, respectively). They require an ISSE capable cpu. In v2.61 an offset argument is added which enables you to access other frames than the current one.

Examples:

threshold = 55
luma = AverageLuma()
luma < threshold 
\ ? Levels(0, 1.0 + 0.5*(threshold - luma)/threshold, 255, 10, 255) 
\ : last

luma = AverageLuma(1) # gives the average luma of the next frame
Difference
RGBDifference(clip1, clip2)  
LumaDifference(clip1, clip2)  
ChromaUDifference(clip1, clip2)  
ChromaVDifference(clip1, clip2)  
This group of functions return a float value between 0 and 255 of the absolute difference between two planes from two different clips – either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively. They require an ISSE capable cpu.

Examples:

ovl = Overlay(last, mov_star, x=some_xvalue, y=some_yvalue, mask=mov_mask)
ldif = LumaDifference(ovl) # implicit last for clip1
udif = ChromaUDifference(Tweak(hue=24), ovl)
...
Difference from previous
RGBDifferenceFromPrevious(clip)  
YDifferenceFromPrevious(clip)  
UDifferenceFromPrevious(clip)  
VDifferenceFromPrevious(clip)  
This group of functions return the absolute difference of pixel value between the current and previous frame of clip – either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively.

Examples:

scene_change = (YDifferenceFromPrevious) > threshold)
scene_change ? some_filter(...) : another_filter(...)
Difference to next
RGBDifferenceToNext(clip [, int offset = 1])  
YDifferenceToNext(clip [, int offset = 1])  
UDifferenceToNext(clip [, int offset = 1])  
VDifferenceToNext(clip [, int offset = 1])  
This group of functions return the absolute difference of pixel value between the current and next frame of clip – either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively. In v2.61 an offset argument is added, which enables you to access the difference between the RGB, luma or chroma plane of the current frame and of any other frame. Note that for example clip.RGBDifferenceToNext(-1) = clip.RGBDifferenceToPrevious, and clip.RGBDifferenceToNext(0) = 0.

Examples:

# both th1, th2 are positive thresholds; th1 is larger enough than th2
scene_change = (YDifferenceFromPrevious > th1) && (YDifferenceToNext < th2)
scene_change ? some_filter(...) : another_filter(...)
Color plane median, min, max, range
YPlaneMedian(clip [, int offset = 0])  
UPlaneMedian(clip [, int offset = 0])  
VPlaneMedian(clip [, int offset = 0])  
YPlaneMin(clip [, float threshold = 0, int offset = 0])  
UPlaneMin(clip [, float threshold = 0, int offset = 0])  
VPlaneMin(clip [, float threshold = 0, int offset = 0])  
YPlaneMax(clip [, float threshold = 0, int offset = 0])  
UPlaneMax(clip [, float threshold = 0, int offset = 0])  
VPlaneMax(clip [, float threshold = 0, int offset = 0])  
YPlaneMinMaxDifference(clip [, float threshold, int offset = 0])  
UPlaneMinMaxDifference(clip [, float threshold, int offset = 0])  
VPlaneMinMaxDifference(clip [, float threshold, int offset = 0])  
This group of functions return statistics about the distribution of pixel values on a plane (Luma, U-chroma and V-chroma, respectively). The statistics are, in order of presentation: maximum, minimum, median and range (maximum - minimum difference).
threshold is a percentage, stating how many percent of the pixels are allowed above or below minimum. The threshold is optional and defaults to 0. In v2.61 an offset argument is added, which enables you to access the statistics of other frames than the current one.

Examples:

# median and average are close only on even distributions; 
# this can be a useful diagnostic
have_intense_brights = YPlaneMedian() - AverageLuma() < threshold
...
# a simple per-frame normalizer to [16..235], CCIR, range
Levels(YPlaneMin(), 1.0, YPlaneMax(), 16, 235)


Script functions

These provide AviSynth script information.
ScriptName
ScriptName()   v2.60
Returns the path and filename of the loaded script as a string.

Examples:

name = ScriptName() # name = "F:\ProjectXYZ\video.avs"
ScriptFile
ScriptFile()   v2.60
Returns the filename of the loaded script as a string.

Examples:

file = ScriptFile() # file = "video.avs"
ScriptDir
ScriptDir()   v2.60
Returns the path of the loaded script as a string.

Examples:

folder = ScriptDir() # folder = "F:\ProjectXYZ"


String functions

These provide common operations on string variables.
LCase
LCase(string)  
Returns lower case of string.

Examples:

LCase("AviSynth") = "avisynth"
UCase
UCase(string)  
Returns upper case of string.

Examples:

UCase("AviSynth") = "AVISYNTH"
StrLen
StrLen(string)  
Returns length of string.

Examples:

StrLen("AviSynth") = 8
RevStr
RevStr(string)  
Returns string backwards.

Examples:

RevStr("AviSynth") = "htnySivA"
LeftStr
LeftStr(string, int)  
Returns first int count of characters.

Examples:

LeftStr("AviSynth", 3) = "Avi"
RightStr
RightStr(string, int)  
Returns last int count of characters.

Examples:

RightStr("AviSynth", 5) = "Synth"
MidStr
MidStr(string, int pos [, int length])  
Returns substring starting at pos for optional length or to end. pos=1 specifies start.

Examples:

MidStr("AviSynth", 3, 2) = "iS"
FindStr
FindStr(string, substring)  
Returns position of string within string (note this function is case-sensitive). Returns 0 if string is not found.

Examples:

Findstr("AviSynth", "Syn") = 4
FillStr
FillStr(int [, string])   v2.60
Fills a string. When int>1 it concatenates the string int times. string is " " (space) by default.

Examples:

FillStr(1, "AviSynth") = "AviSynth"
FillStr(2, "AviSynth") = "AviSynthAviSynth"
StrCmp
StrCmp(string, string)   v2.60
Compares two character strings. The comparison is case-sensitive. If the first string is less than the second string, the return value is negative. If it's greater, the return value is positive. If they are equal, the return value is zero. (The actual value seems to be language dependent so it can't be relied upon.)

Examples:

StrCmp("AviSynth", "AviSynth") = 0 # strings are equal.
StrCmp("AviSynth", "Avisynth") != 0 # strings are not equal.
StrCmpi
StrCmpi(string, string)   v2.60
Compares two character strings. The comparison is not case-sensitive. If the first string is less than the second string, the return value is negative. If it's greater, the return value is positive. If they are equal, the return value is zero. (The actual value seems to be language dependent so it can't be relied upon.)

Examples:

StrCmpi("AviSynth", "AviSynth") = 0 # strings are equal.
StrCmpi("AviSynth", "Avisynth") = 0 # strings are equal.
StrCmpi("abcz", "abcdefg") != 0 
# returns the difference betweeen "z" and "d" (which is positive).
Chr
Chr(int)  
Returns the ASCII character.
Note that characters above the ASCII character set (ie above 127) are code page dependent and may render different (visual) results in different systems. This has an importance only for user-supplied localised text messages.

Examples:

Chr(34) returns the quote character
Chr(9)  returns the tab   character
Ord
Ord(string)   v2.60
Gives the ordinal number (character code) of the first character of string (works like php ord or Basic Asc)

Examples:

Ord("a") = 97
Ord("AviSynth") = Ord("A") = 65
Ord("§") = 167
Time
Time(string)  
Returns a string with the current system time formatted as defined by string.
The string may contain any of the codes for output formatting presented below:
Code Description
%a

%A

Abbreviated weekday name

Full weekday name

%b

%B

Abbreviated month name

Full month name

%c Date and time representation appropriate for locale
%d Day of month as decimal number (01 - 31)
%H

%I

Hour in 24-hour format (00 - 23)

Hour in 12-hour format (01 - 12)

%j Day of year as decimal number (001 - 366)
%m Month as decimal number (01 - 12)
%M Minute as decimal number (00 - 59)
%p Current locale's A.M./P.M. indicator for 12-hour clock
%S Second as decimal number (00 - 59)
%U Week of year as decimal number, with Sunday as first day of week (00 - 53)
%w Weekday as decimal number (0 - 6; Sunday is 0)
%W Week of year as decimal number, with Monday as first day of week (00 - 53)
%x Date representation for current locale
%X Time representation for current locale
%y

%Y

Year without century, as decimal number (00 - 99)

Year with century, as decimal number

%z, %Z Time-zone name or abbreviation; no characters if time zone is unknown
%% Percent sign
The '#' flag may prefix any formatting code. In that case, the meaning of the format code is changed as follows:
Code with '#' flag Change in meaning
%#a, %#A, %#b,

%#B, %#p, %#X, %#z, %#Z, %#%

No change; flag is ignored.
%#c Long date and time representation, appropriate for current locale.

For example, "Tuesday, March 14, 1995, 12:41:29"

%#x Long date representation, appropriate to current locale.

For example, "Tuesday, March 14, 1995"

%#d, %#H, %#I,

%#j, %#m, %#M, %#S, %#U, %#w, %#W, %#y, %#Y

Remove leading zeros (if any).

Examples:

v = Time("%Y-%m-%d")        # "2010-03-01"
v = Time("%d-%b-%Y")        # "01-Mar-2010"
v = Time("%#d/%#m/%y")      # "1/3/10"
v = Time("%I:%M:%S %p, %z") # "08:04:42 PM, GMT Standard Time"
v = Time("%H:%M:%S %z")     # "20:04:42 GMT Standard Time"

Version functions

These provide AviSynth version information.
VersionNumber
VersionNumber()  
Returns AviSynth version number as a float.

Examples:

v = VersionNumber() # 2.60
VersionString
VersionString()  
Returns AviSynth version info as a string (first line used in Version() command).

Examples:

v = VersionString() # "AviSynth 2.60, build:Mar 31 2015 [16:38:54]"



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