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yading@10: .\" ========================================================================
yading@10: .\"
yading@10: .IX Title "FFMPEG-UTILS 1"
yading@10: .TH FFMPEG-UTILS 1 "2013-04-21" " " " "
yading@10: .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
yading@10: .\" way too many mistakes in technical documents.
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yading@10: .nh
yading@10: .SH "NAME"
yading@10: ffmpeg\-utils \- FFmpeg utilities
yading@10: .SH "DESCRIPTION"
yading@10: .IX Header "DESCRIPTION"
yading@10: This document describes some generic features and utilities provided
yading@10: by the libavutil library.
yading@10: .SH "SYNTAX"
yading@10: .IX Header "SYNTAX"
yading@10: This section documents the syntax and formats employed by the FFmpeg
yading@10: libraries and tools.
yading@10: .SS "Quoting and escaping"
yading@10: .IX Subsection "Quoting and escaping"
yading@10: FFmpeg adopts the following quoting and escaping mechanism, unless
yading@10: explicitly specified. The following rules are applied:
yading@10: .IP "\(bu" 4
yading@10: \&\f(CW\*(C`\*(Aq\*(C'\fR and \f(CW\*(C`\e\*(C'\fR are special characters (respectively used for
yading@10: quoting and escaping). In addition to them, there might be other
yading@10: special characters depending on the specific syntax where the escaping
yading@10: and quoting are employed.
yading@10: .IP "\(bu" 4
yading@10: A special character is escaped by prefixing it with a '\e'.
yading@10: .IP "\(bu" 4
yading@10: All characters enclosed between '' are included literally in the
yading@10: parsed string. The quote character \f(CW\*(C`\*(Aq\*(C'\fR itself cannot be quoted,
yading@10: so you may need to close the quote and escape it.
yading@10: .IP "\(bu" 4
yading@10: Leading and trailing whitespaces, unless escaped or quoted, are
yading@10: removed from the parsed string.
yading@10: .PP
yading@10: Note that you may need to add a second level of escaping when using
yading@10: the command line or a script, which depends on the syntax of the
yading@10: adopted shell language.
yading@10: .PP
yading@10: The function \f(CW\*(C`av_get_token\*(C'\fR defined in
yading@10: \&\fIlibavutil/avstring.h\fR can be used to parse a token quoted or
yading@10: escaped according to the rules defined above.
yading@10: .PP
yading@10: The tool \fItools/ffescape\fR in the FFmpeg source tree can be used
yading@10: to automatically quote or escape a string in a script.
yading@10: .PP
yading@10: \fIExamples\fR
yading@10: .IX Subsection "Examples"
yading@10: .IP "\(bu" 4
yading@10: Escape the string \f(CW\*(C`Crime d\*(AqAmour\*(C'\fR containing the \f(CW\*(C`\*(Aq\*(C'\fR special
yading@10: character:
yading@10: .Sp
yading@10: .Vb 1
yading@10: \&        Crime d\e\*(AqAmour
yading@10: .Ve
yading@10: .IP "\(bu" 4
yading@10: The string above contains a quote, so the \f(CW\*(C`\*(Aq\*(C'\fR needs to be escaped
yading@10: when quoting it:
yading@10: .Sp
yading@10: .Vb 1
yading@10: \&        \*(AqCrime d\*(Aq\e\*(Aq\*(AqAmour\*(Aq
yading@10: .Ve
yading@10: .IP "\(bu" 4
yading@10: Include leading or trailing whitespaces using quoting:
yading@10: .Sp
yading@10: .Vb 1
yading@10: \&        \*(Aq  this string starts and ends with whitespaces  \*(Aq
yading@10: .Ve
yading@10: .IP "\(bu" 4
yading@10: Escaping and quoting can be mixed together:
yading@10: .Sp
yading@10: .Vb 1
yading@10: \&        \*(Aq The string \*(Aq\e\*(Aqstring\e\*(Aq\*(Aq is a string \*(Aq
yading@10: .Ve
yading@10: .IP "\(bu" 4
yading@10: To include a literal \f(CW\*(C`\e\*(C'\fR you can use either escaping or quoting:
yading@10: .Sp
yading@10: .Vb 1
yading@10: \&        \*(Aqc:\efoo\*(Aq can be written as c:\e\efoo
yading@10: .Ve
yading@10: .SS "Date"
yading@10: .IX Subsection "Date"
yading@10: The accepted syntax is:
yading@10: .PP
yading@10: .Vb 2
yading@10: \&        [(YYYY\-MM\-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
yading@10: \&        now
yading@10: .Ve
yading@10: .PP
yading@10: If the value is \*(L"now\*(R" it takes the current time.
yading@10: .PP
yading@10: Time is local time unless Z is appended, in which case it is
yading@10: interpreted as \s-1UTC\s0.
yading@10: If the year-month-day part is not specified it takes the current
yading@10: year-month-day.
yading@10: .SS "Time duration"
yading@10: .IX Subsection "Time duration"
yading@10: The accepted syntax is:
yading@10: .PP
yading@10: .Vb 2
yading@10: \&        [\-][HH:]MM:SS[.m...]
yading@10: \&        [\-]S+[.m...]
yading@10: .Ve
yading@10: .PP
yading@10: \&\fI\s-1HH\s0\fR expresses the number of hours, \fI\s-1MM\s0\fR the number a of minutes
yading@10: and \fI\s-1SS\s0\fR the number of seconds.
yading@10: .SS "Video size"
yading@10: .IX Subsection "Video size"
yading@10: Specify the size of the sourced video, it may be a string of the form
yading@10: \&\fIwidth\fRx\fIheight\fR, or the name of a size abbreviation.
yading@10: .PP
yading@10: The following abbreviations are recognized:
yading@10: .IP "\fBntsc\fR" 4
yading@10: .IX Item "ntsc"
yading@10: 720x480
yading@10: .IP "\fBpal\fR" 4
yading@10: .IX Item "pal"
yading@10: 720x576
yading@10: .IP "\fBqntsc\fR" 4
yading@10: .IX Item "qntsc"
yading@10: 352x240
yading@10: .IP "\fBqpal\fR" 4
yading@10: .IX Item "qpal"
yading@10: 352x288
yading@10: .IP "\fBsntsc\fR" 4
yading@10: .IX Item "sntsc"
yading@10: 640x480
yading@10: .IP "\fBspal\fR" 4
yading@10: .IX Item "spal"
yading@10: 768x576
yading@10: .IP "\fBfilm\fR" 4
yading@10: .IX Item "film"
yading@10: 352x240
yading@10: .IP "\fBntsc-film\fR" 4
yading@10: .IX Item "ntsc-film"
yading@10: 352x240
yading@10: .IP "\fBsqcif\fR" 4
yading@10: .IX Item "sqcif"
yading@10: 128x96
yading@10: .IP "\fBqcif\fR" 4
yading@10: .IX Item "qcif"
yading@10: 176x144
yading@10: .IP "\fBcif\fR" 4
yading@10: .IX Item "cif"
yading@10: 352x288
yading@10: .IP "\fB4cif\fR" 4
yading@10: .IX Item "4cif"
yading@10: 704x576
yading@10: .IP "\fB16cif\fR" 4
yading@10: .IX Item "16cif"
yading@10: 1408x1152
yading@10: .IP "\fBqqvga\fR" 4
yading@10: .IX Item "qqvga"
yading@10: 160x120
yading@10: .IP "\fBqvga\fR" 4
yading@10: .IX Item "qvga"
yading@10: 320x240
yading@10: .IP "\fBvga\fR" 4
yading@10: .IX Item "vga"
yading@10: 640x480
yading@10: .IP "\fBsvga\fR" 4
yading@10: .IX Item "svga"
yading@10: 800x600
yading@10: .IP "\fBxga\fR" 4
yading@10: .IX Item "xga"
yading@10: 1024x768
yading@10: .IP "\fBuxga\fR" 4
yading@10: .IX Item "uxga"
yading@10: 1600x1200
yading@10: .IP "\fBqxga\fR" 4
yading@10: .IX Item "qxga"
yading@10: 2048x1536
yading@10: .IP "\fBsxga\fR" 4
yading@10: .IX Item "sxga"
yading@10: 1280x1024
yading@10: .IP "\fBqsxga\fR" 4
yading@10: .IX Item "qsxga"
yading@10: 2560x2048
yading@10: .IP "\fBhsxga\fR" 4
yading@10: .IX Item "hsxga"
yading@10: 5120x4096
yading@10: .IP "\fBwvga\fR" 4
yading@10: .IX Item "wvga"
yading@10: 852x480
yading@10: .IP "\fBwxga\fR" 4
yading@10: .IX Item "wxga"
yading@10: 1366x768
yading@10: .IP "\fBwsxga\fR" 4
yading@10: .IX Item "wsxga"
yading@10: 1600x1024
yading@10: .IP "\fBwuxga\fR" 4
yading@10: .IX Item "wuxga"
yading@10: 1920x1200
yading@10: .IP "\fBwoxga\fR" 4
yading@10: .IX Item "woxga"
yading@10: 2560x1600
yading@10: .IP "\fBwqsxga\fR" 4
yading@10: .IX Item "wqsxga"
yading@10: 3200x2048
yading@10: .IP "\fBwquxga\fR" 4
yading@10: .IX Item "wquxga"
yading@10: 3840x2400
yading@10: .IP "\fBwhsxga\fR" 4
yading@10: .IX Item "whsxga"
yading@10: 6400x4096
yading@10: .IP "\fBwhuxga\fR" 4
yading@10: .IX Item "whuxga"
yading@10: 7680x4800
yading@10: .IP "\fBcga\fR" 4
yading@10: .IX Item "cga"
yading@10: 320x200
yading@10: .IP "\fBega\fR" 4
yading@10: .IX Item "ega"
yading@10: 640x350
yading@10: .IP "\fBhd480\fR" 4
yading@10: .IX Item "hd480"
yading@10: 852x480
yading@10: .IP "\fBhd720\fR" 4
yading@10: .IX Item "hd720"
yading@10: 1280x720
yading@10: .IP "\fBhd1080\fR" 4
yading@10: .IX Item "hd1080"
yading@10: 1920x1080
yading@10: .IP "\fB2k\fR" 4
yading@10: .IX Item "2k"
yading@10: 2048x1080
yading@10: .IP "\fB2kflat\fR" 4
yading@10: .IX Item "2kflat"
yading@10: 1998x1080
yading@10: .IP "\fB2kscope\fR" 4
yading@10: .IX Item "2kscope"
yading@10: 2048x858
yading@10: .IP "\fB4k\fR" 4
yading@10: .IX Item "4k"
yading@10: 4096x2160
yading@10: .IP "\fB4kflat\fR" 4
yading@10: .IX Item "4kflat"
yading@10: 3996x2160
yading@10: .IP "\fB4kscope\fR" 4
yading@10: .IX Item "4kscope"
yading@10: 4096x1716
yading@10: .SS "Video rate"
yading@10: .IX Subsection "Video rate"
yading@10: Specify the frame rate of a video, expressed as the number of frames
yading@10: generated per second. It has to be a string in the format
yading@10: \&\fIframe_rate_num\fR/\fIframe_rate_den\fR, an integer number, a float
yading@10: number or a valid video frame rate abbreviation.
yading@10: .PP
yading@10: The following abbreviations are recognized:
yading@10: .IP "\fBntsc\fR" 4
yading@10: .IX Item "ntsc"
yading@10: 30000/1001
yading@10: .IP "\fBpal\fR" 4
yading@10: .IX Item "pal"
yading@10: 25/1
yading@10: .IP "\fBqntsc\fR" 4
yading@10: .IX Item "qntsc"
yading@10: 30000/1001
yading@10: .IP "\fBqpal\fR" 4
yading@10: .IX Item "qpal"
yading@10: 25/1
yading@10: .IP "\fBsntsc\fR" 4
yading@10: .IX Item "sntsc"
yading@10: 30000/1001
yading@10: .IP "\fBspal\fR" 4
yading@10: .IX Item "spal"
yading@10: 25/1
yading@10: .IP "\fBfilm\fR" 4
yading@10: .IX Item "film"
yading@10: 24/1
yading@10: .IP "\fBntsc-film\fR" 4
yading@10: .IX Item "ntsc-film"
yading@10: 24000/1001
yading@10: .SS "Ratio"
yading@10: .IX Subsection "Ratio"
yading@10: A ratio can be expressed as an expression, or in the form
yading@10: \&\fInumerator\fR:\fIdenominator\fR.
yading@10: .PP
yading@10: Note that a ratio with infinite (1/0) or negative value is
yading@10: considered valid, so you should check on the returned value if you
yading@10: want to exclude those values.
yading@10: .PP
yading@10: The undefined value can be expressed using the \*(L"0:0\*(R" string.
yading@10: .SS "Color"
yading@10: .IX Subsection "Color"
yading@10: It can be the name of a color (case insensitive match) or a
yading@10: [0x|#]RRGGBB[\s-1AA\s0] sequence, possibly followed by \*(L"@\*(R" and a string
yading@10: representing the alpha component.
yading@10: .PP
yading@10: The alpha component may be a string composed by \*(L"0x\*(R" followed by an
yading@10: hexadecimal number or a decimal number between 0.0 and 1.0, which
yading@10: represents the opacity value (0x00/0.0 means completely transparent,
yading@10: 0xff/1.0 completely opaque).
yading@10: If the alpha component is not specified then 0xff is assumed.
yading@10: .PP
yading@10: The string \*(L"random\*(R" will result in a random color.
yading@10: .SH "EXPRESSION EVALUATION"
yading@10: .IX Header "EXPRESSION EVALUATION"
yading@10: When evaluating an arithmetic expression, FFmpeg uses an internal
yading@10: formula evaluator, implemented through the \fIlibavutil/eval.h\fR
yading@10: interface.
yading@10: .PP
yading@10: An expression may contain unary, binary operators, constants, and
yading@10: functions.
yading@10: .PP
yading@10: Two expressions \fIexpr1\fR and \fIexpr2\fR can be combined to form
yading@10: another expression "\fIexpr1\fR;\fIexpr2\fR".
yading@10: \&\fIexpr1\fR and \fIexpr2\fR are evaluated in turn, and the new
yading@10: expression evaluates to the value of \fIexpr2\fR.
yading@10: .PP
yading@10: The following binary operators are available: \f(CW\*(C`+\*(C'\fR, \f(CW\*(C`\-\*(C'\fR,
yading@10: \&\f(CW\*(C`*\*(C'\fR, \f(CW\*(C`/\*(C'\fR, \f(CW\*(C`^\*(C'\fR.
yading@10: .PP
yading@10: The following unary operators are available: \f(CW\*(C`+\*(C'\fR, \f(CW\*(C`\-\*(C'\fR.
yading@10: .PP
yading@10: The following functions are available:
yading@10: .IP "\fBabs(x)\fR" 4
yading@10: .IX Item "abs(x)"
yading@10: Compute absolute value of \fIx\fR.
yading@10: .IP "\fBacos(x)\fR" 4
yading@10: .IX Item "acos(x)"
yading@10: Compute arccosine of \fIx\fR.
yading@10: .IP "\fBasin(x)\fR" 4
yading@10: .IX Item "asin(x)"
yading@10: Compute arcsine of \fIx\fR.
yading@10: .IP "\fBatan(x)\fR" 4
yading@10: .IX Item "atan(x)"
yading@10: Compute arctangent of \fIx\fR.
yading@10: .IP "\fBbetween(x, min, max)\fR" 4
yading@10: .IX Item "between(x, min, max)"
yading@10: Return 1 if \fIx\fR is greater than or equal to \fImin\fR and lesser than or
yading@10: equal to \fImax\fR, 0 otherwise.
yading@10: .IP "\fBbitand(x, y)\fR" 4
yading@10: .IX Item "bitand(x, y)"
yading@10: .PD 0
yading@10: .IP "\fBbitor(x, y)\fR" 4
yading@10: .IX Item "bitor(x, y)"
yading@10: .PD
yading@10: Compute bitwise and/or operation on \fIx\fR and \fIy\fR.
yading@10: .Sp
yading@10: The results of the evaluation of \fIx\fR and \fIy\fR are converted to
yading@10: integers before executing the bitwise operation.
yading@10: .Sp
yading@10: Note that both the conversion to integer and the conversion back to
yading@10: floating point can lose precision. Beware of unexpected results for
yading@10: large numbers (usually 2^53 and larger).
yading@10: .IP "\fBceil(expr)\fR" 4
yading@10: .IX Item "ceil(expr)"
yading@10: Round the value of expression \fIexpr\fR upwards to the nearest
yading@10: integer. For example, \*(L"ceil(1.5)\*(R" is \*(L"2.0\*(R".
yading@10: .IP "\fBcos(x)\fR" 4
yading@10: .IX Item "cos(x)"
yading@10: Compute cosine of \fIx\fR.
yading@10: .IP "\fBcosh(x)\fR" 4
yading@10: .IX Item "cosh(x)"
yading@10: Compute hyperbolic cosine of \fIx\fR.
yading@10: .IP "\fBeq(x, y)\fR" 4
yading@10: .IX Item "eq(x, y)"
yading@10: Return 1 if \fIx\fR and \fIy\fR are equivalent, 0 otherwise.
yading@10: .IP "\fBexp(x)\fR" 4
yading@10: .IX Item "exp(x)"
yading@10: Compute exponential of \fIx\fR (with base \f(CW\*(C`e\*(C'\fR, the Euler's number).
yading@10: .IP "\fBfloor(expr)\fR" 4
yading@10: .IX Item "floor(expr)"
yading@10: Round the value of expression \fIexpr\fR downwards to the nearest
yading@10: integer. For example, \*(L"floor(\-1.5)\*(R" is \*(L"\-2.0\*(R".
yading@10: .IP "\fBgauss(x)\fR" 4
yading@10: .IX Item "gauss(x)"
yading@10: Compute Gauss function of \fIx\fR, corresponding to
yading@10: \&\f(CW\*(C`exp(\-x*x/2) / sqrt(2*PI)\*(C'\fR.
yading@10: .IP "\fBgcd(x, y)\fR" 4
yading@10: .IX Item "gcd(x, y)"
yading@10: Return the greatest common divisor of \fIx\fR and \fIy\fR. If both \fIx\fR and
yading@10: \&\fIy\fR are 0 or either or both are less than zero then behavior is undefined.
yading@10: .IP "\fBgt(x, y)\fR" 4
yading@10: .IX Item "gt(x, y)"
yading@10: Return 1 if \fIx\fR is greater than \fIy\fR, 0 otherwise.
yading@10: .IP "\fBgte(x, y)\fR" 4
yading@10: .IX Item "gte(x, y)"
yading@10: Return 1 if \fIx\fR is greater than or equal to \fIy\fR, 0 otherwise.
yading@10: .IP "\fBhypot(x, y)\fR" 4
yading@10: .IX Item "hypot(x, y)"
yading@10: This function is similar to the C function with the same name; it returns
yading@10: "sqrt(\fIx\fR*\fIx\fR + \fIy\fR*\fIy\fR)", the length of the hypotenuse of a
yading@10: right triangle with sides of length \fIx\fR and \fIy\fR, or the distance of the
yading@10: point (\fIx\fR, \fIy\fR) from the origin.
yading@10: .IP "\fBif(x, y)\fR" 4
yading@10: .IX Item "if(x, y)"
yading@10: Evaluate \fIx\fR, and if the result is non-zero return the result of
yading@10: the evaluation of \fIy\fR, return 0 otherwise.
yading@10: .IP "\fBif(x, y, z)\fR" 4
yading@10: .IX Item "if(x, y, z)"
yading@10: Evaluate \fIx\fR, and if the result is non-zero return the evaluation
yading@10: result of \fIy\fR, otherwise the evaluation result of \fIz\fR.
yading@10: .IP "\fBifnot(x, y)\fR" 4
yading@10: .IX Item "ifnot(x, y)"
yading@10: Evaluate \fIx\fR, and if the result is zero return the result of the
yading@10: evaluation of \fIy\fR, return 0 otherwise.
yading@10: .IP "\fBifnot(x, y, z)\fR" 4
yading@10: .IX Item "ifnot(x, y, z)"
yading@10: Evaluate \fIx\fR, and if the result is zero return the evaluation
yading@10: result of \fIy\fR, otherwise the evaluation result of \fIz\fR.
yading@10: .IP "\fBisinf(x)\fR" 4
yading@10: .IX Item "isinf(x)"
yading@10: Return 1.0 if \fIx\fR is +/\-INFINITY, 0.0 otherwise.
yading@10: .IP "\fBisnan(x)\fR" 4
yading@10: .IX Item "isnan(x)"
yading@10: Return 1.0 if \fIx\fR is \s-1NAN\s0, 0.0 otherwise.
yading@10: .IP "\fBld(var)\fR" 4
yading@10: .IX Item "ld(var)"
yading@10: Allow to load the value of the internal variable with number
yading@10: \&\fIvar\fR, which was previously stored with st(\fIvar\fR, \fIexpr\fR).
yading@10: The function returns the loaded value.
yading@10: .IP "\fBlog(x)\fR" 4
yading@10: .IX Item "log(x)"
yading@10: Compute natural logarithm of \fIx\fR.
yading@10: .IP "\fBlt(x, y)\fR" 4
yading@10: .IX Item "lt(x, y)"
yading@10: Return 1 if \fIx\fR is lesser than \fIy\fR, 0 otherwise.
yading@10: .IP "\fBlte(x, y)\fR" 4
yading@10: .IX Item "lte(x, y)"
yading@10: Return 1 if \fIx\fR is lesser than or equal to \fIy\fR, 0 otherwise.
yading@10: .IP "\fBmax(x, y)\fR" 4
yading@10: .IX Item "max(x, y)"
yading@10: Return the maximum between \fIx\fR and \fIy\fR.
yading@10: .IP "\fBmin(x, y)\fR" 4
yading@10: .IX Item "min(x, y)"
yading@10: Return the maximum between \fIx\fR and \fIy\fR.
yading@10: .IP "\fBmod(x, y)\fR" 4
yading@10: .IX Item "mod(x, y)"
yading@10: Compute the remainder of division of \fIx\fR by \fIy\fR.
yading@10: .IP "\fBnot(expr)\fR" 4
yading@10: .IX Item "not(expr)"
yading@10: Return 1.0 if \fIexpr\fR is zero, 0.0 otherwise.
yading@10: .IP "\fBpow(x, y)\fR" 4
yading@10: .IX Item "pow(x, y)"
yading@10: Compute the power of \fIx\fR elevated \fIy\fR, it is equivalent to
yading@10: "(\fIx\fR)^(\fIy\fR)".
yading@10: .IP "\fBprint(t)\fR" 4
yading@10: .IX Item "print(t)"
yading@10: .PD 0
yading@10: .IP "\fBprint(t, l)\fR" 4
yading@10: .IX Item "print(t, l)"
yading@10: .PD
yading@10: Print the value of expression \fIt\fR with loglevel \fIl\fR. If
yading@10: \&\fIl\fR is not specified then a default log level is used.
yading@10: Returns the value of the expression printed.
yading@10: .Sp
yading@10: Prints t with loglevel l
yading@10: .IP "\fBrandom(x)\fR" 4
yading@10: .IX Item "random(x)"
yading@10: Return a pseudo random value between 0.0 and 1.0. \fIx\fR is the index of the
yading@10: internal variable which will be used to save the seed/state.
yading@10: .IP "\fBroot(expr, max)\fR" 4
yading@10: .IX Item "root(expr, max)"
yading@10: Find an input value for which the function represented by \fIexpr\fR
yading@10: with argument \fI\fIld\fI\|(0)\fR is 0 in the interval 0..\fImax\fR.
yading@10: .Sp
yading@10: The expression in \fIexpr\fR must denote a continuous function or the
yading@10: result is undefined.
yading@10: .Sp
yading@10: \&\fI\fIld\fI\|(0)\fR is used to represent the function input value, which means
yading@10: that the given expression will be evaluated multiple times with
yading@10: various input values that the expression can access through
yading@10: \&\f(CWld(0)\fR. When the expression evaluates to 0 then the
yading@10: corresponding input value will be returned.
yading@10: .IP "\fBsin(x)\fR" 4
yading@10: .IX Item "sin(x)"
yading@10: Compute sine of \fIx\fR.
yading@10: .IP "\fBsinh(x)\fR" 4
yading@10: .IX Item "sinh(x)"
yading@10: Compute hyperbolic sine of \fIx\fR.
yading@10: .IP "\fBsqrt(expr)\fR" 4
yading@10: .IX Item "sqrt(expr)"
yading@10: Compute the square root of \fIexpr\fR. This is equivalent to
yading@10: "(\fIexpr\fR)^.5".
yading@10: .IP "\fBsquish(x)\fR" 4
yading@10: .IX Item "squish(x)"
yading@10: Compute expression \f(CW\*(C`1/(1 + exp(4*x))\*(C'\fR.
yading@10: .IP "\fBst(var, expr)\fR" 4
yading@10: .IX Item "st(var, expr)"
yading@10: Allow to store the value of the expression \fIexpr\fR in an internal
yading@10: variable. \fIvar\fR specifies the number of the variable where to
yading@10: store the value, and it is a value ranging from 0 to 9. The function
yading@10: returns the value stored in the internal variable.
yading@10: Note, Variables are currently not shared between expressions.
yading@10: .IP "\fBtan(x)\fR" 4
yading@10: .IX Item "tan(x)"
yading@10: Compute tangent of \fIx\fR.
yading@10: .IP "\fBtanh(x)\fR" 4
yading@10: .IX Item "tanh(x)"
yading@10: Compute hyperbolic tangent of \fIx\fR.
yading@10: .IP "\fBtaylor(expr, x)\fR" 4
yading@10: .IX Item "taylor(expr, x)"
yading@10: .PD 0
yading@10: .IP "\fBtaylor(expr, x, id)\fR" 4
yading@10: .IX Item "taylor(expr, x, id)"
yading@10: .PD
yading@10: Evaluate a Taylor series at \fIx\fR, given an expression representing
yading@10: the \f(CW\*(C`ld(id)\*(C'\fR\-th derivative of a function at 0.
yading@10: .Sp
yading@10: When the series does not converge the result is undefined.
yading@10: .Sp
yading@10: \&\fIld(id)\fR is used to represent the derivative order in \fIexpr\fR,
yading@10: which means that the given expression will be evaluated multiple times
yading@10: with various input values that the expression can access through
yading@10: \&\f(CW\*(C`ld(id)\*(C'\fR. If \fIid\fR is not specified then 0 is assumed.
yading@10: .Sp
yading@10: Note, when you have the derivatives at y instead of 0,
yading@10: \&\f(CW\*(C`taylor(expr, x\-y)\*(C'\fR can be used.
yading@10: .IP "\fB\f(BItime\fB\|(0)\fR" 4
yading@10: .IX Item "time"
yading@10: Return the current (wallclock) time in seconds.
yading@10: .IP "\fBtrunc(expr)\fR" 4
yading@10: .IX Item "trunc(expr)"
yading@10: Round the value of expression \fIexpr\fR towards zero to the nearest
yading@10: integer. For example, \*(L"trunc(\-1.5)\*(R" is \*(L"\-1.0\*(R".
yading@10: .IP "\fBwhile(cond, expr)\fR" 4
yading@10: .IX Item "while(cond, expr)"
yading@10: Evaluate expression \fIexpr\fR while the expression \fIcond\fR is
yading@10: non-zero, and returns the value of the last \fIexpr\fR evaluation, or
yading@10: \&\s-1NAN\s0 if \fIcond\fR was always false.
yading@10: .PP
yading@10: The following constants are available:
yading@10: .IP "\fB\s-1PI\s0\fR" 4
yading@10: .IX Item "PI"
yading@10: area of the unit disc, approximately 3.14
yading@10: .IP "\fBE\fR" 4
yading@10: .IX Item "E"
yading@10: \&\fIexp\fR\|(1) (Euler's number), approximately 2.718
yading@10: .IP "\fB\s-1PHI\s0\fR" 4
yading@10: .IX Item "PHI"
yading@10: golden ratio (1+\fIsqrt\fR\|(5))/2, approximately 1.618
yading@10: .PP
yading@10: Assuming that an expression is considered \*(L"true\*(R" if it has a non-zero
yading@10: value, note that:
yading@10: .PP
yading@10: \&\f(CW\*(C`*\*(C'\fR works like \s-1AND\s0
yading@10: .PP
yading@10: \&\f(CW\*(C`+\*(C'\fR works like \s-1OR\s0
yading@10: .PP
yading@10: For example the construct:
yading@10: .PP
yading@10: .Vb 1
yading@10: \&        if (A AND B) then C
yading@10: .Ve
yading@10: .PP
yading@10: is equivalent to:
yading@10: .PP
yading@10: .Vb 1
yading@10: \&        if(A*B, C)
yading@10: .Ve
yading@10: .PP
yading@10: In your C code, you can extend the list of unary and binary functions,
yading@10: and define recognized constants, so that they are available for your
yading@10: expressions.
yading@10: .PP
yading@10: The evaluator also recognizes the International System unit prefixes.
yading@10: If 'i' is appended after the prefix, binary prefixes are used, which
yading@10: are based on powers of 1024 instead of powers of 1000.
yading@10: The 'B' postfix multiplies the value by 8, and can be appended after a
yading@10: unit prefix or used alone. This allows using for example '\s-1KB\s0', 'MiB',
yading@10: \&'G' and 'B' as number postfix.
yading@10: .PP
yading@10: The list of available International System prefixes follows, with
yading@10: indication of the corresponding powers of 10 and of 2.
yading@10: .IP "\fBy\fR" 4
yading@10: .IX Item "y"
yading@10: 10^\-24 / 2^\-80
yading@10: .IP "\fBz\fR" 4
yading@10: .IX Item "z"
yading@10: 10^\-21 / 2^\-70
yading@10: .IP "\fBa\fR" 4
yading@10: .IX Item "a"
yading@10: 10^\-18 / 2^\-60
yading@10: .IP "\fBf\fR" 4
yading@10: .IX Item "f"
yading@10: 10^\-15 / 2^\-50
yading@10: .IP "\fBp\fR" 4
yading@10: .IX Item "p"
yading@10: 10^\-12 / 2^\-40
yading@10: .IP "\fBn\fR" 4
yading@10: .IX Item "n"
yading@10: 10^\-9 / 2^\-30
yading@10: .IP "\fBu\fR" 4
yading@10: .IX Item "u"
yading@10: 10^\-6 / 2^\-20
yading@10: .IP "\fBm\fR" 4
yading@10: .IX Item "m"
yading@10: 10^\-3 / 2^\-10
yading@10: .IP "\fBc\fR" 4
yading@10: .IX Item "c"
yading@10: 10^\-2
yading@10: .IP "\fBd\fR" 4
yading@10: .IX Item "d"
yading@10: 10^\-1
yading@10: .IP "\fBh\fR" 4
yading@10: .IX Item "h"
yading@10: 10^2
yading@10: .IP "\fBk\fR" 4
yading@10: .IX Item "k"
yading@10: 10^3 / 2^10
yading@10: .IP "\fBK\fR" 4
yading@10: .IX Item "K"
yading@10: 10^3 / 2^10
yading@10: .IP "\fBM\fR" 4
yading@10: .IX Item "M"
yading@10: 10^6 / 2^20
yading@10: .IP "\fBG\fR" 4
yading@10: .IX Item "G"
yading@10: 10^9 / 2^30
yading@10: .IP "\fBT\fR" 4
yading@10: .IX Item "T"
yading@10: 10^12 / 2^40
yading@10: .IP "\fBP\fR" 4
yading@10: .IX Item "P"
yading@10: 10^15 / 2^40
yading@10: .IP "\fBE\fR" 4
yading@10: .IX Item "E"
yading@10: 10^18 / 2^50
yading@10: .IP "\fBZ\fR" 4
yading@10: .IX Item "Z"
yading@10: 10^21 / 2^60
yading@10: .IP "\fBY\fR" 4
yading@10: .IX Item "Y"
yading@10: 10^24 / 2^70
yading@10: .SH "OPENCL OPTIONS"
yading@10: .IX Header "OPENCL OPTIONS"
yading@10: When FFmpeg is configured with \f(CW\*(C`\-\-enable\-opencl\*(C'\fR, it is possible
yading@10: to set the options for the global OpenCL context.
yading@10: .PP
yading@10: The list of supported options follows:
yading@10: .IP "\fBbuild_options\fR" 4
yading@10: .IX Item "build_options"
yading@10: Set build options used to compile the registered kernels.
yading@10: .Sp
yading@10: See reference \*(L"OpenCL Specification Version: 1.2 chapter 5.6.4\*(R".
yading@10: .IP "\fBplatform_idx\fR" 4
yading@10: .IX Item "platform_idx"
yading@10: Select the index of the platform to run OpenCL code.
yading@10: .Sp
yading@10: The specified index must be one of the indexes in the device list
yading@10: which can be obtained with \f(CW\*(C`av_opencl_get_device_list()\*(C'\fR.
yading@10: .IP "\fBdevice_idx\fR" 4
yading@10: .IX Item "device_idx"
yading@10: Select the index of the device used to run OpenCL code.
yading@10: .Sp
yading@10: The specifed index must be one of the indexes in the device list which
yading@10: can be obtained with \f(CW\*(C`av_opencl_get_device_list()\*(C'\fR.
yading@10: .SH "SEE ALSO"
yading@10: .IX Header "SEE ALSO"
yading@10: \&\fIffmpeg\fR\|(1), \fIffplay\fR\|(1), \fIffprobe\fR\|(1), \fIffserver\fR\|(1), \fIlibavutil\fR\|(3)
yading@10: .SH "AUTHORS"
yading@10: .IX Header "AUTHORS"
yading@10: The FFmpeg developers.
yading@10: .PP
yading@10: For details about the authorship, see the Git history of the project
yading@10: (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
yading@10: \&\fBgit log\fR in the FFmpeg source directory, or browsing the
yading@10: online repository at <\fBhttp://source.ffmpeg.org\fR>.
yading@10: .PP
yading@10: Maintainers for the specific components are listed in the file
yading@10: \&\fI\s-1MAINTAINERS\s0\fR in the source code tree.