--- /dev/null
- @item uhd1
+@chapter Syntax
+@c man begin SYNTAX
+
+This section documents the syntax and formats employed by the FFmpeg
+libraries and tools.
+
+@anchor{quoting_and_escaping}
+@section Quoting and escaping
+
+FFmpeg adopts the following quoting and escaping mechanism, unless
+explicitly specified. The following rules are applied:
+
+@itemize
+@item
+@samp{'} and @samp{\} 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.
+
+@item
+A special character is escaped by prefixing it with a @samp{\}.
+
+@item
+All characters enclosed between @samp{''} are included literally in the
+parsed string. The quote character @samp{'} itself cannot be quoted,
+so you may need to close the quote and escape it.
+
+@item
+Leading and trailing whitespaces, unless escaped or quoted, are
+removed from the parsed string.
+@end itemize
+
+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 @code{av_get_token} defined in
+@file{libavutil/avstring.h} can be used to parse a token quoted or
+escaped according to the rules defined above.
+
+The tool @file{tools/ffescape} in the FFmpeg source tree can be used
+to automatically quote or escape a string in a script.
+
+@subsection Examples
+
+@itemize
+@item
+Escape the string @code{Crime d'Amour} containing the @code{'} special
+character:
+@example
+Crime d\'Amour
+@end example
+
+@item
+The string above contains a quote, so the @code{'} needs to be escaped
+when quoting it:
+@example
+'Crime d'\''Amour'
+@end example
+
+@item
+Include leading or trailing whitespaces using quoting:
+@example
+' this string starts and ends with whitespaces '
+@end example
+
+@item
+Escaping and quoting can be mixed together:
+@example
+' The string '\'string\'' is a string '
+@end example
+
+@item
+To include a literal @samp{\} you can use either escaping or quoting:
+@example
+'c:\foo' can be written as c:\\foo
+@end example
+@end itemize
+
+@anchor{date syntax}
+@section Date
+
+The accepted syntax is:
+@example
+[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
+now
+@end example
+
+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.
+
+@anchor{time duration syntax}
+@section Time duration
+
+There are two accepted syntaxes for expressing time duration.
+
+@example
+[-][@var{HH}:]@var{MM}:@var{SS}[.@var{m}...]
+@end example
+
+@var{HH} expresses the number of hours, @var{MM} the number of minutes
+for a maximum of 2 digits, and @var{SS} the number of seconds for a
+maximum of 2 digits. The @var{m} at the end expresses decimal value for
+@var{SS}.
+
+@emph{or}
+
+@example
+[-]@var{S}+[.@var{m}...]
+@end example
+
+@var{S} expresses the number of seconds, with the optional decimal part
+@var{m}.
+
+In both expressions, the optional @samp{-} indicates negative duration.
+
+@subsection Examples
+
+The following examples are all valid time duration:
+
+@table @samp
+@item 55
+55 seconds
+
+@item 12:03:45
+12 hours, 03 minutes and 45 seconds
+
+@item 23.189
+23.189 seconds
+@end table
+
+@anchor{video size syntax}
+@section Video size
+Specify the size of the sourced video, it may be a string of the form
+@var{width}x@var{height}, or the name of a size abbreviation.
+
+The following abbreviations are recognized:
+@table @samp
+@item ntsc
+720x480
+@item pal
+720x576
+@item qntsc
+352x240
+@item qpal
+352x288
+@item sntsc
+640x480
+@item spal
+768x576
+@item film
+352x240
+@item ntsc-film
+352x240
+@item sqcif
+128x96
+@item qcif
+176x144
+@item cif
+352x288
+@item 4cif
+704x576
+@item 16cif
+1408x1152
+@item qqvga
+160x120
+@item qvga
+320x240
+@item vga
+640x480
+@item svga
+800x600
+@item xga
+1024x768
+@item uxga
+1600x1200
+@item qxga
+2048x1536
+@item sxga
+1280x1024
+@item qsxga
+2560x2048
+@item hsxga
+5120x4096
+@item wvga
+852x480
+@item wxga
+1366x768
+@item wsxga
+1600x1024
+@item wuxga
+1920x1200
+@item woxga
+2560x1600
+@item wqsxga
+3200x2048
+@item wquxga
+3840x2400
+@item whsxga
+6400x4096
+@item whuxga
+7680x4800
+@item cga
+320x200
+@item ega
+640x350
+@item hd480
+852x480
+@item hd720
+1280x720
+@item hd1080
+1920x1080
+@item 2k
+2048x1080
+@item 2kflat
+1998x1080
+@item 2kscope
+2048x858
+@item 4k
+4096x2160
+@item 4kflat
+3996x2160
+@item 4kscope
+4096x1716
+@item nhd
+640x360
+@item hqvga
+240x160
+@item wqvga
+400x240
+@item fwqvga
+432x240
+@item hvga
+480x320
+@item qhd
+960x540
+@item 2kdci
+2048x1080
+@item 4kdci
+4096x2160
- @item uhd2
++@item uhd2160
+3840x2160
++@item uhd4320
+7680x4320
+@end table
+
+@anchor{video rate syntax}
+@section 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
+@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
+number or a valid video frame rate abbreviation.
+
+The following abbreviations are recognized:
+@table @samp
+@item ntsc
+30000/1001
+@item pal
+25/1
+@item qntsc
+30000/1001
+@item qpal
+25/1
+@item sntsc
+30000/1001
+@item spal
+25/1
+@item film
+24/1
+@item ntsc-film
+24000/1001
+@end table
+
+@anchor{ratio syntax}
+@section Ratio
+
+A ratio can be expressed as an expression, or in the form
+@var{numerator}:@var{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.
+
+@anchor{color syntax}
+@section Color
+
+It can be the name of a color as defined below (case insensitive match) or a
+@code{[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 (@samp{0x00} or @samp{0.0} means completely
+transparent, @samp{0xff} or @samp{1.0} completely opaque). If the alpha
+component is not specified then @samp{0xff} is assumed.
+
+The string @samp{random} will result in a random color.
+
+The following names of colors are recognized:
+@table @samp
+@item AliceBlue
+0xF0F8FF
+@item AntiqueWhite
+0xFAEBD7
+@item Aqua
+0x00FFFF
+@item Aquamarine
+0x7FFFD4
+@item Azure
+0xF0FFFF
+@item Beige
+0xF5F5DC
+@item Bisque
+0xFFE4C4
+@item Black
+0x000000
+@item BlanchedAlmond
+0xFFEBCD
+@item Blue
+0x0000FF
+@item BlueViolet
+0x8A2BE2
+@item Brown
+0xA52A2A
+@item BurlyWood
+0xDEB887
+@item CadetBlue
+0x5F9EA0
+@item Chartreuse
+0x7FFF00
+@item Chocolate
+0xD2691E
+@item Coral
+0xFF7F50
+@item CornflowerBlue
+0x6495ED
+@item Cornsilk
+0xFFF8DC
+@item Crimson
+0xDC143C
+@item Cyan
+0x00FFFF
+@item DarkBlue
+0x00008B
+@item DarkCyan
+0x008B8B
+@item DarkGoldenRod
+0xB8860B
+@item DarkGray
+0xA9A9A9
+@item DarkGreen
+0x006400
+@item DarkKhaki
+0xBDB76B
+@item DarkMagenta
+0x8B008B
+@item DarkOliveGreen
+0x556B2F
+@item Darkorange
+0xFF8C00
+@item DarkOrchid
+0x9932CC
+@item DarkRed
+0x8B0000
+@item DarkSalmon
+0xE9967A
+@item DarkSeaGreen
+0x8FBC8F
+@item DarkSlateBlue
+0x483D8B
+@item DarkSlateGray
+0x2F4F4F
+@item DarkTurquoise
+0x00CED1
+@item DarkViolet
+0x9400D3
+@item DeepPink
+0xFF1493
+@item DeepSkyBlue
+0x00BFFF
+@item DimGray
+0x696969
+@item DodgerBlue
+0x1E90FF
+@item FireBrick
+0xB22222
+@item FloralWhite
+0xFFFAF0
+@item ForestGreen
+0x228B22
+@item Fuchsia
+0xFF00FF
+@item Gainsboro
+0xDCDCDC
+@item GhostWhite
+0xF8F8FF
+@item Gold
+0xFFD700
+@item GoldenRod
+0xDAA520
+@item Gray
+0x808080
+@item Green
+0x008000
+@item GreenYellow
+0xADFF2F
+@item HoneyDew
+0xF0FFF0
+@item HotPink
+0xFF69B4
+@item IndianRed
+0xCD5C5C
+@item Indigo
+0x4B0082
+@item Ivory
+0xFFFFF0
+@item Khaki
+0xF0E68C
+@item Lavender
+0xE6E6FA
+@item LavenderBlush
+0xFFF0F5
+@item LawnGreen
+0x7CFC00
+@item LemonChiffon
+0xFFFACD
+@item LightBlue
+0xADD8E6
+@item LightCoral
+0xF08080
+@item LightCyan
+0xE0FFFF
+@item LightGoldenRodYellow
+0xFAFAD2
+@item LightGreen
+0x90EE90
+@item LightGrey
+0xD3D3D3
+@item LightPink
+0xFFB6C1
+@item LightSalmon
+0xFFA07A
+@item LightSeaGreen
+0x20B2AA
+@item LightSkyBlue
+0x87CEFA
+@item LightSlateGray
+0x778899
+@item LightSteelBlue
+0xB0C4DE
+@item LightYellow
+0xFFFFE0
+@item Lime
+0x00FF00
+@item LimeGreen
+0x32CD32
+@item Linen
+0xFAF0E6
+@item Magenta
+0xFF00FF
+@item Maroon
+0x800000
+@item MediumAquaMarine
+0x66CDAA
+@item MediumBlue
+0x0000CD
+@item MediumOrchid
+0xBA55D3
+@item MediumPurple
+0x9370D8
+@item MediumSeaGreen
+0x3CB371
+@item MediumSlateBlue
+0x7B68EE
+@item MediumSpringGreen
+0x00FA9A
+@item MediumTurquoise
+0x48D1CC
+@item MediumVioletRed
+0xC71585
+@item MidnightBlue
+0x191970
+@item MintCream
+0xF5FFFA
+@item MistyRose
+0xFFE4E1
+@item Moccasin
+0xFFE4B5
+@item NavajoWhite
+0xFFDEAD
+@item Navy
+0x000080
+@item OldLace
+0xFDF5E6
+@item Olive
+0x808000
+@item OliveDrab
+0x6B8E23
+@item Orange
+0xFFA500
+@item OrangeRed
+0xFF4500
+@item Orchid
+0xDA70D6
+@item PaleGoldenRod
+0xEEE8AA
+@item PaleGreen
+0x98FB98
+@item PaleTurquoise
+0xAFEEEE
+@item PaleVioletRed
+0xD87093
+@item PapayaWhip
+0xFFEFD5
+@item PeachPuff
+0xFFDAB9
+@item Peru
+0xCD853F
+@item Pink
+0xFFC0CB
+@item Plum
+0xDDA0DD
+@item PowderBlue
+0xB0E0E6
+@item Purple
+0x800080
+@item Red
+0xFF0000
+@item RosyBrown
+0xBC8F8F
+@item RoyalBlue
+0x4169E1
+@item SaddleBrown
+0x8B4513
+@item Salmon
+0xFA8072
+@item SandyBrown
+0xF4A460
+@item SeaGreen
+0x2E8B57
+@item SeaShell
+0xFFF5EE
+@item Sienna
+0xA0522D
+@item Silver
+0xC0C0C0
+@item SkyBlue
+0x87CEEB
+@item SlateBlue
+0x6A5ACD
+@item SlateGray
+0x708090
+@item Snow
+0xFFFAFA
+@item SpringGreen
+0x00FF7F
+@item SteelBlue
+0x4682B4
+@item Tan
+0xD2B48C
+@item Teal
+0x008080
+@item Thistle
+0xD8BFD8
+@item Tomato
+0xFF6347
+@item Turquoise
+0x40E0D0
+@item Violet
+0xEE82EE
+@item Wheat
+0xF5DEB3
+@item White
+0xFFFFFF
+@item WhiteSmoke
+0xF5F5F5
+@item Yellow
+0xFFFF00
+@item YellowGreen
+0x9ACD32
+@end table
+
+@anchor{channel layout syntax}
+@section 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:
+@table @samp
+@item FL
+front left
+@item FR
+front right
+@item FC
+front center
+@item LFE
+low frequency
+@item BL
+back left
+@item BR
+back right
+@item FLC
+front left-of-center
+@item FRC
+front right-of-center
+@item BC
+back center
+@item SL
+side left
+@item SR
+side right
+@item TC
+top center
+@item TFL
+top front left
+@item TFC
+top front center
+@item TFR
+top front right
+@item TBL
+top back left
+@item TBC
+top back center
+@item TBR
+top back right
+@item DL
+downmix left
+@item DR
+downmix right
+@item WL
+wide left
+@item WR
+wide right
+@item SDL
+surround direct left
+@item SDR
+surround direct right
+@item LFE2
+low frequency 2
+@end table
+
+Standard channel layout compositions can be specified by using the
+following identifiers:
+@table @samp
+@item mono
+FC
+@item stereo
+FL+FR
+@item 2.1
+FL+FR+LFE
+@item 3.0
+FL+FR+FC
+@item 3.0(back)
+FL+FR+BC
+@item 4.0
+FL+FR+FC+BC
+@item quad
+FL+FR+BL+BR
+@item quad(side)
+FL+FR+SL+SR
+@item 3.1
+FL+FR+FC+LFE
+@item 5.0
+FL+FR+FC+BL+BR
+@item 5.0(side)
+FL+FR+FC+SL+SR
+@item 4.1
+FL+FR+FC+LFE+BC
+@item 5.1
+FL+FR+FC+LFE+BL+BR
+@item 5.1(side)
+FL+FR+FC+LFE+SL+SR
+@item 6.0
+FL+FR+FC+BC+SL+SR
+@item 6.0(front)
+FL+FR+FLC+FRC+SL+SR
+@item hexagonal
+FL+FR+FC+BL+BR+BC
+@item 6.1
+FL+FR+FC+LFE+BC+SL+SR
+@item 6.1
+FL+FR+FC+LFE+BL+BR+BC
+@item 6.1(front)
+FL+FR+LFE+FLC+FRC+SL+SR
+@item 7.0
+FL+FR+FC+BL+BR+SL+SR
+@item 7.0(front)
+FL+FR+FC+FLC+FRC+SL+SR
+@item 7.1
+FL+FR+FC+LFE+BL+BR+SL+SR
+@item 7.1(wide)
+FL+FR+FC+LFE+BL+BR+FLC+FRC
+@item 7.1(wide-side)
+FL+FR+FC+LFE+FLC+FRC+SL+SR
+@item octagonal
+FL+FR+FC+BL+BR+BC+SL+SR
+@item downmix
+DL+DR
+@end table
+
+A custom channel layout can be specified as a sequence of terms, separated by
+'+' or '|'. Each term can be:
+@itemize
+@item
+the name of a standard channel layout (e.g. @samp{mono},
+@samp{stereo}, @samp{4.0}, @samp{quad}, @samp{5.0}, etc.)
+
+@item
+the name of a single channel (e.g. @samp{FL}, @samp{FR}, @samp{FC}, @samp{LFE}, etc.)
+
+@item
+a number of channels, in decimal, optionally followed by 'c', yielding
+the default channel layout for that number of channels (see the
+function @code{av_get_default_channel_layout})
+
+@item
+a channel layout mask, in hexadecimal starting with "0x" (see the
+@code{AV_CH_*} macros in @file{libavutil/channel_layout.h}.
+@end itemize
+
+Starting from libavutil version 53 the trailing character "c" to
+specify a number of channels will be required, while a channel layout
+mask could also be specified as a decimal number (if and only if not
+followed by "c").
+
+See also the function @code{av_get_channel_layout} defined in
+@file{libavutil/channel_layout.h}.
+@c man end SYNTAX
+
+@chapter Expression Evaluation
+@c man begin EXPRESSION EVALUATION
+
+When evaluating an arithmetic expression, FFmpeg uses an internal
+formula evaluator, implemented through the @file{libavutil/eval.h}
+interface.
+
+An expression may contain unary, binary operators, constants, and
+functions.
+
+Two expressions @var{expr1} and @var{expr2} can be combined to form
+another expression "@var{expr1};@var{expr2}".
+@var{expr1} and @var{expr2} are evaluated in turn, and the new
+expression evaluates to the value of @var{expr2}.
+
+The following binary operators are available: @code{+}, @code{-},
+@code{*}, @code{/}, @code{^}.
+
+The following unary operators are available: @code{+}, @code{-}.
+
+The following functions are available:
+@table @option
+@item abs(x)
+Compute absolute value of @var{x}.
+
+@item acos(x)
+Compute arccosine of @var{x}.
+
+@item asin(x)
+Compute arcsine of @var{x}.
+
+@item atan(x)
+Compute arctangent of @var{x}.
+
+@item between(x, min, max)
+Return 1 if @var{x} is greater than or equal to @var{min} and lesser than or
+equal to @var{max}, 0 otherwise.
+
+@item bitand(x, y)
+@item bitor(x, y)
+Compute bitwise and/or operation on @var{x} and @var{y}.
+
+The results of the evaluation of @var{x} and @var{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).
+
+@item ceil(expr)
+Round the value of expression @var{expr} upwards to the nearest
+integer. For example, "ceil(1.5)" is "2.0".
+
+@item clip(x, min, max)
+Return the value of @var{x} clipped between @var{min} and @var{max}.
+
+@item cos(x)
+Compute cosine of @var{x}.
+
+@item cosh(x)
+Compute hyperbolic cosine of @var{x}.
+
+@item eq(x, y)
+Return 1 if @var{x} and @var{y} are equivalent, 0 otherwise.
+
+@item exp(x)
+Compute exponential of @var{x} (with base @code{e}, the Euler's number).
+
+@item floor(expr)
+Round the value of expression @var{expr} downwards to the nearest
+integer. For example, "floor(-1.5)" is "-2.0".
+
+@item gauss(x)
+Compute Gauss function of @var{x}, corresponding to
+@code{exp(-x*x/2) / sqrt(2*PI)}.
+
+@item gcd(x, y)
+Return the greatest common divisor of @var{x} and @var{y}. If both @var{x} and
+@var{y} are 0 or either or both are less than zero then behavior is undefined.
+
+@item gt(x, y)
+Return 1 if @var{x} is greater than @var{y}, 0 otherwise.
+
+@item gte(x, y)
+Return 1 if @var{x} is greater than or equal to @var{y}, 0 otherwise.
+
+@item hypot(x, y)
+This function is similar to the C function with the same name; it returns
+"sqrt(@var{x}*@var{x} + @var{y}*@var{y})", the length of the hypotenuse of a
+right triangle with sides of length @var{x} and @var{y}, or the distance of the
+point (@var{x}, @var{y}) from the origin.
+
+@item if(x, y)
+Evaluate @var{x}, and if the result is non-zero return the result of
+the evaluation of @var{y}, return 0 otherwise.
+
+@item if(x, y, z)
+Evaluate @var{x}, and if the result is non-zero return the evaluation
+result of @var{y}, otherwise the evaluation result of @var{z}.
+
+@item ifnot(x, y)
+Evaluate @var{x}, and if the result is zero return the result of the
+evaluation of @var{y}, return 0 otherwise.
+
+@item ifnot(x, y, z)
+Evaluate @var{x}, and if the result is zero return the evaluation
+result of @var{y}, otherwise the evaluation result of @var{z}.
+
+@item isinf(x)
+Return 1.0 if @var{x} is +/-INFINITY, 0.0 otherwise.
+
+@item isnan(x)
+Return 1.0 if @var{x} is NAN, 0.0 otherwise.
+
+@item ld(var)
+Load the value of the internal variable with number
+@var{var}, which was previously stored with st(@var{var}, @var{expr}).
+The function returns the loaded value.
+
+@item log(x)
+Compute natural logarithm of @var{x}.
+
+@item lt(x, y)
+Return 1 if @var{x} is lesser than @var{y}, 0 otherwise.
+
+@item lte(x, y)
+Return 1 if @var{x} is lesser than or equal to @var{y}, 0 otherwise.
+
+@item max(x, y)
+Return the maximum between @var{x} and @var{y}.
+
+@item min(x, y)
+Return the maximum between @var{x} and @var{y}.
+
+@item mod(x, y)
+Compute the remainder of division of @var{x} by @var{y}.
+
+@item not(expr)
+Return 1.0 if @var{expr} is zero, 0.0 otherwise.
+
+@item pow(x, y)
+Compute the power of @var{x} elevated @var{y}, it is equivalent to
+"(@var{x})^(@var{y})".
+
+@item print(t)
+@item print(t, l)
+Print the value of expression @var{t} with loglevel @var{l}. If
+@var{l} is not specified then a default log level is used.
+Returns the value of the expression printed.
+
+Prints t with loglevel l
+
+@item random(x)
+Return a pseudo random value between 0.0 and 1.0. @var{x} is the index of the
+internal variable which will be used to save the seed/state.
+
+@item root(expr, max)
+Find an input value for which the function represented by @var{expr}
+with argument @var{ld(0)} is 0 in the interval 0..@var{max}.
+
+The expression in @var{expr} must denote a continuous function or the
+result is undefined.
+
+@var{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
+@code{ld(0)}. When the expression evaluates to 0 then the
+corresponding input value will be returned.
+
+@item sin(x)
+Compute sine of @var{x}.
+
+@item sinh(x)
+Compute hyperbolic sine of @var{x}.
+
+@item sqrt(expr)
+Compute the square root of @var{expr}. This is equivalent to
+"(@var{expr})^.5".
+
+@item squish(x)
+Compute expression @code{1/(1 + exp(4*x))}.
+
+@item st(var, expr)
+Store the value of the expression @var{expr} in an internal
+variable. @var{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.
+
+@item tan(x)
+Compute tangent of @var{x}.
+
+@item tanh(x)
+Compute hyperbolic tangent of @var{x}.
+
+@item taylor(expr, x)
+@item taylor(expr, x, id)
+Evaluate a Taylor series at @var{x}, given an expression representing
+the @code{ld(id)}-th derivative of a function at 0.
+
+When the series does not converge the result is undefined.
+
+@var{ld(id)} is used to represent the derivative order in @var{expr},
+which means that the given expression will be evaluated multiple times
+with various input values that the expression can access through
+@code{ld(id)}. If @var{id} is not specified then 0 is assumed.
+
+Note, when you have the derivatives at y instead of 0,
+@code{taylor(expr, x-y)} can be used.
+
+@item time(0)
+Return the current (wallclock) time in seconds.
+
+@item trunc(expr)
+Round the value of expression @var{expr} towards zero to the nearest
+integer. For example, "trunc(-1.5)" is "-1.0".
+
+@item while(cond, expr)
+Evaluate expression @var{expr} while the expression @var{cond} is
+non-zero, and returns the value of the last @var{expr} evaluation, or
+NAN if @var{cond} was always false.
+@end table
+
+The following constants are available:
+@table @option
+@item PI
+area of the unit disc, approximately 3.14
+@item E
+exp(1) (Euler's number), approximately 2.718
+@item PHI
+golden ratio (1+sqrt(5))/2, approximately 1.618
+@end table
+
+Assuming that an expression is considered "true" if it has a non-zero
+value, note that:
+
+@code{*} works like AND
+
+@code{+} works like OR
+
+For example the construct:
+@example
+if (A AND B) then C
+@end example
+is equivalent to:
+@example
+if(A*B, C)
+@end example
+
+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.
+@table @option
+@item y
+10^-24 / 2^-80
+@item z
+10^-21 / 2^-70
+@item a
+10^-18 / 2^-60
+@item f
+10^-15 / 2^-50
+@item p
+10^-12 / 2^-40
+@item n
+10^-9 / 2^-30
+@item u
+10^-6 / 2^-20
+@item m
+10^-3 / 2^-10
+@item c
+10^-2
+@item d
+10^-1
+@item h
+10^2
+@item k
+10^3 / 2^10
+@item K
+10^3 / 2^10
+@item M
+10^6 / 2^20
+@item G
+10^9 / 2^30
+@item T
+10^12 / 2^40
+@item P
+10^15 / 2^40
+@item E
+10^18 / 2^50
+@item Z
+10^21 / 2^60
+@item Y
+10^24 / 2^70
+@end table
+
+@c man end EXPRESSION EVALUATION
+
+@chapter OpenCL Options
+@c man begin OPENCL OPTIONS
+
+When FFmpeg is configured with @code{--enable-opencl}, it is possible
+to set the options for the global OpenCL context.
+
+The list of supported options follows:
+
+@table @option
+@item build_options
+Set build options used to compile the registered kernels.
+
+See reference "OpenCL Specification Version: 1.2 chapter 5.6.4".
+
+@item platform_idx
+Select the index of the platform to run OpenCL code.
+
+The specified index must be one of the indexes in the device list
+which can be obtained with @code{ffmpeg -opencl_bench} or @code{av_opencl_get_device_list()}.
+
+@item device_idx
+Select the index of the device used to run OpenCL code.
+
+The specified index must be one of the indexes in the device list which
+can be obtained with @code{ffmpeg -opencl_bench} or @code{av_opencl_get_device_list()}.
+
+@end table
+
+@c man end OPENCL OPTIONS
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