yading@10: =head1 NAME
yading@10: 
yading@10: ffmpeg-utils - FFmpeg utilities
yading@10: 
yading@10: =head1 DESCRIPTION
yading@10: 
yading@10: 
yading@10: This document describes some generic features and utilities provided
yading@10: by the libavutil library.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 SYNTAX
yading@10: 
yading@10: 
yading@10: This section documents the syntax and formats employed by the FFmpeg
yading@10: libraries and tools.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Quoting and escaping
yading@10: 
yading@10: 
yading@10: FFmpeg adopts the following quoting and escaping mechanism, unless
yading@10: explicitly specified. The following rules are applied:
yading@10: 
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: C<'> and C<\> 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: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: A special character is escaped by prefixing it with a '\'.
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: All characters enclosed between '' are included literally in the
yading@10: parsed string. The quote character C<'> itself cannot be quoted,
yading@10: so you may need to close the quote and escape it.
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: Leading and trailing whitespaces, unless escaped or quoted, are
yading@10: removed from the parsed string.
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
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: 
yading@10: The function C<av_get_token> defined in
yading@10: F<libavutil/avstring.h> can be used to parse a token quoted or
yading@10: escaped according to the rules defined above.
yading@10: 
yading@10: The tool F<tools/ffescape> in the FFmpeg source tree can be used
yading@10: to automatically quote or escape a string in a script.
yading@10: 
yading@10: 
yading@10: =head3 Examples
yading@10: 
yading@10: 
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: Escape the string C<Crime d'Amour> containing the C<'> special
yading@10: character:
yading@10: 	
yading@10: 	Crime d\'Amour
yading@10: 
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: The string above contains a quote, so the C<'> needs to be escaped
yading@10: when quoting it:
yading@10: 	
yading@10: 	'Crime d'\''Amour'
yading@10: 
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: Include leading or trailing whitespaces using quoting:
yading@10: 	
yading@10: 	'  this string starts and ends with whitespaces  '
yading@10: 
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: Escaping and quoting can be mixed together:
yading@10: 	
yading@10: 	' The string '\'string\'' is a string '
yading@10: 
yading@10: 
yading@10: 
yading@10: =item *
yading@10: 
yading@10: To include a literal C<\> you can use either escaping or quoting:
yading@10: 	
yading@10: 	'c:\foo' can be written as c:\\foo
yading@10: 
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Date
yading@10: 
yading@10: 
yading@10: The accepted syntax is:
yading@10: 	
yading@10: 	[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
yading@10: 	now
yading@10: 
yading@10: 
yading@10: If the value is "now" it takes the current time.
yading@10: 
yading@10: Time is local time unless Z is appended, in which case it is
yading@10: interpreted as UTC.
yading@10: If the year-month-day part is not specified it takes the current
yading@10: year-month-day.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Time duration
yading@10: 
yading@10: 
yading@10: The accepted syntax is:
yading@10: 	
yading@10: 	[-][HH:]MM:SS[.m...]
yading@10: 	[-]S+[.m...]
yading@10: 
yading@10: 
yading@10: I<HH> expresses the number of hours, I<MM> the number a of minutes
yading@10: and I<SS> the number of seconds.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Video size
yading@10: 
yading@10: Specify the size of the sourced video, it may be a string of the form
yading@10: I<width>xI<height>, or the name of a size abbreviation.
yading@10: 
yading@10: The following abbreviations are recognized:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<ntsc>
yading@10: 
yading@10: 720x480
yading@10: 
yading@10: =item B<pal>
yading@10: 
yading@10: 720x576
yading@10: 
yading@10: =item B<qntsc>
yading@10: 
yading@10: 352x240
yading@10: 
yading@10: =item B<qpal>
yading@10: 
yading@10: 352x288
yading@10: 
yading@10: =item B<sntsc>
yading@10: 
yading@10: 640x480
yading@10: 
yading@10: =item B<spal>
yading@10: 
yading@10: 768x576
yading@10: 
yading@10: =item B<film>
yading@10: 
yading@10: 352x240
yading@10: 
yading@10: =item B<ntsc-film>
yading@10: 
yading@10: 352x240
yading@10: 
yading@10: =item B<sqcif>
yading@10: 
yading@10: 128x96
yading@10: 
yading@10: =item B<qcif>
yading@10: 
yading@10: 176x144
yading@10: 
yading@10: =item B<cif>
yading@10: 
yading@10: 352x288
yading@10: 
yading@10: =item B<4cif>
yading@10: 
yading@10: 704x576
yading@10: 
yading@10: =item B<16cif>
yading@10: 
yading@10: 1408x1152
yading@10: 
yading@10: =item B<qqvga>
yading@10: 
yading@10: 160x120
yading@10: 
yading@10: =item B<qvga>
yading@10: 
yading@10: 320x240
yading@10: 
yading@10: =item B<vga>
yading@10: 
yading@10: 640x480
yading@10: 
yading@10: =item B<svga>
yading@10: 
yading@10: 800x600
yading@10: 
yading@10: =item B<xga>
yading@10: 
yading@10: 1024x768
yading@10: 
yading@10: =item B<uxga>
yading@10: 
yading@10: 1600x1200
yading@10: 
yading@10: =item B<qxga>
yading@10: 
yading@10: 2048x1536
yading@10: 
yading@10: =item B<sxga>
yading@10: 
yading@10: 1280x1024
yading@10: 
yading@10: =item B<qsxga>
yading@10: 
yading@10: 2560x2048
yading@10: 
yading@10: =item B<hsxga>
yading@10: 
yading@10: 5120x4096
yading@10: 
yading@10: =item B<wvga>
yading@10: 
yading@10: 852x480
yading@10: 
yading@10: =item B<wxga>
yading@10: 
yading@10: 1366x768
yading@10: 
yading@10: =item B<wsxga>
yading@10: 
yading@10: 1600x1024
yading@10: 
yading@10: =item B<wuxga>
yading@10: 
yading@10: 1920x1200
yading@10: 
yading@10: =item B<woxga>
yading@10: 
yading@10: 2560x1600
yading@10: 
yading@10: =item B<wqsxga>
yading@10: 
yading@10: 3200x2048
yading@10: 
yading@10: =item B<wquxga>
yading@10: 
yading@10: 3840x2400
yading@10: 
yading@10: =item B<whsxga>
yading@10: 
yading@10: 6400x4096
yading@10: 
yading@10: =item B<whuxga>
yading@10: 
yading@10: 7680x4800
yading@10: 
yading@10: =item B<cga>
yading@10: 
yading@10: 320x200
yading@10: 
yading@10: =item B<ega>
yading@10: 
yading@10: 640x350
yading@10: 
yading@10: =item B<hd480>
yading@10: 
yading@10: 852x480
yading@10: 
yading@10: =item B<hd720>
yading@10: 
yading@10: 1280x720
yading@10: 
yading@10: =item B<hd1080>
yading@10: 
yading@10: 1920x1080
yading@10: 
yading@10: =item B<2k>
yading@10: 
yading@10: 2048x1080
yading@10: 
yading@10: =item B<2kflat>
yading@10: 
yading@10: 1998x1080
yading@10: 
yading@10: =item B<2kscope>
yading@10: 
yading@10: 2048x858
yading@10: 
yading@10: =item B<4k>
yading@10: 
yading@10: 4096x2160
yading@10: 
yading@10: =item B<4kflat>
yading@10: 
yading@10: 3996x2160
yading@10: 
yading@10: =item B<4kscope>
yading@10: 
yading@10: 4096x1716
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Video rate
yading@10: 
yading@10: 
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: I<frame_rate_num>/I<frame_rate_den>, an integer number, a float
yading@10: number or a valid video frame rate abbreviation.
yading@10: 
yading@10: The following abbreviations are recognized:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<ntsc>
yading@10: 
yading@10: 30000/1001
yading@10: 
yading@10: =item B<pal>
yading@10: 
yading@10: 25/1
yading@10: 
yading@10: =item B<qntsc>
yading@10: 
yading@10: 30000/1001
yading@10: 
yading@10: =item B<qpal>
yading@10: 
yading@10: 25/1
yading@10: 
yading@10: =item B<sntsc>
yading@10: 
yading@10: 30000/1001
yading@10: 
yading@10: =item B<spal>
yading@10: 
yading@10: 25/1
yading@10: 
yading@10: =item B<film>
yading@10: 
yading@10: 24/1
yading@10: 
yading@10: =item B<ntsc-film>
yading@10: 
yading@10: 24000/1001
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Ratio
yading@10: 
yading@10: 
yading@10: A ratio can be expressed as an expression, or in the form
yading@10: I<numerator>:I<denominator>.
yading@10: 
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: 
yading@10: The undefined value can be expressed using the "0:0" string.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head2 Color
yading@10: 
yading@10: 
yading@10: It can be the name of a color (case insensitive match) or a
yading@10: [0x|#]RRGGBB[AA] sequence, possibly followed by "@" and a string
yading@10: representing the alpha component.
yading@10: 
yading@10: The alpha component may be a string composed by "0x" 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: 
yading@10: The string "random" will result in a random color.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 EXPRESSION EVALUATION
yading@10: 
yading@10: 
yading@10: When evaluating an arithmetic expression, FFmpeg uses an internal
yading@10: formula evaluator, implemented through the F<libavutil/eval.h>
yading@10: interface.
yading@10: 
yading@10: An expression may contain unary, binary operators, constants, and
yading@10: functions.
yading@10: 
yading@10: Two expressions I<expr1> and I<expr2> can be combined to form
yading@10: another expression "I<expr1>;I<expr2>".
yading@10: I<expr1> and I<expr2> are evaluated in turn, and the new
yading@10: expression evaluates to the value of I<expr2>.
yading@10: 
yading@10: The following binary operators are available: C<+>, C<->,
yading@10: C<*>, C</>, C<^>.
yading@10: 
yading@10: The following unary operators are available: C<+>, C<->.
yading@10: 
yading@10: The following functions are available:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<abs(x)>
yading@10: 
yading@10: Compute absolute value of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<acos(x)>
yading@10: 
yading@10: Compute arccosine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<asin(x)>
yading@10: 
yading@10: Compute arcsine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<atan(x)>
yading@10: 
yading@10: Compute arctangent of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<between(x, min, max)>
yading@10: 
yading@10: Return 1 if I<x> is greater than or equal to I<min> and lesser than or
yading@10: equal to I<max>, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<bitand(x, y)>
yading@10: 
yading@10: 
yading@10: =item B<bitor(x, y)>
yading@10: 
yading@10: Compute bitwise and/or operation on I<x> and I<y>.
yading@10: 
yading@10: The results of the evaluation of I<x> and I<y> are converted to
yading@10: integers before executing the bitwise operation.
yading@10: 
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: 
yading@10: 
yading@10: =item B<ceil(expr)>
yading@10: 
yading@10: Round the value of expression I<expr> upwards to the nearest
yading@10: integer. For example, "ceil(1.5)" is "2.0".
yading@10: 
yading@10: 
yading@10: =item B<cos(x)>
yading@10: 
yading@10: Compute cosine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<cosh(x)>
yading@10: 
yading@10: Compute hyperbolic cosine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<eq(x, y)>
yading@10: 
yading@10: Return 1 if I<x> and I<y> are equivalent, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<exp(x)>
yading@10: 
yading@10: Compute exponential of I<x> (with base C<e>, the Euler's number).
yading@10: 
yading@10: 
yading@10: =item B<floor(expr)>
yading@10: 
yading@10: Round the value of expression I<expr> downwards to the nearest
yading@10: integer. For example, "floor(-1.5)" is "-2.0".
yading@10: 
yading@10: 
yading@10: =item B<gauss(x)>
yading@10: 
yading@10: Compute Gauss function of I<x>, corresponding to
yading@10: C<exp(-x*x/2) / sqrt(2*PI)>.
yading@10: 
yading@10: 
yading@10: =item B<gcd(x, y)>
yading@10: 
yading@10: Return the greatest common divisor of I<x> and I<y>. If both I<x> and
yading@10: I<y> are 0 or either or both are less than zero then behavior is undefined.
yading@10: 
yading@10: 
yading@10: =item B<gt(x, y)>
yading@10: 
yading@10: Return 1 if I<x> is greater than I<y>, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<gte(x, y)>
yading@10: 
yading@10: Return 1 if I<x> is greater than or equal to I<y>, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<hypot(x, y)>
yading@10: 
yading@10: This function is similar to the C function with the same name; it returns
yading@10: "sqrt(I<x>*I<x> + I<y>*I<y>)", the length of the hypotenuse of a
yading@10: right triangle with sides of length I<x> and I<y>, or the distance of the
yading@10: point (I<x>, I<y>) from the origin.
yading@10: 
yading@10: 
yading@10: =item B<if(x, y)>
yading@10: 
yading@10: Evaluate I<x>, and if the result is non-zero return the result of
yading@10: the evaluation of I<y>, return 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<if(x, y, z)>
yading@10: 
yading@10: Evaluate I<x>, and if the result is non-zero return the evaluation
yading@10: result of I<y>, otherwise the evaluation result of I<z>.
yading@10: 
yading@10: 
yading@10: =item B<ifnot(x, y)>
yading@10: 
yading@10: Evaluate I<x>, and if the result is zero return the result of the
yading@10: evaluation of I<y>, return 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<ifnot(x, y, z)>
yading@10: 
yading@10: Evaluate I<x>, and if the result is zero return the evaluation
yading@10: result of I<y>, otherwise the evaluation result of I<z>.
yading@10: 
yading@10: 
yading@10: =item B<isinf(x)>
yading@10: 
yading@10: Return 1.0 if I<x> is +/-INFINITY, 0.0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<isnan(x)>
yading@10: 
yading@10: Return 1.0 if I<x> is NAN, 0.0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<ld(var)>
yading@10: 
yading@10: Allow to load the value of the internal variable with number
yading@10: I<var>, which was previously stored with st(I<var>, I<expr>).
yading@10: The function returns the loaded value.
yading@10: 
yading@10: 
yading@10: =item B<log(x)>
yading@10: 
yading@10: Compute natural logarithm of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<lt(x, y)>
yading@10: 
yading@10: Return 1 if I<x> is lesser than I<y>, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<lte(x, y)>
yading@10: 
yading@10: Return 1 if I<x> is lesser than or equal to I<y>, 0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<max(x, y)>
yading@10: 
yading@10: Return the maximum between I<x> and I<y>.
yading@10: 
yading@10: 
yading@10: =item B<min(x, y)>
yading@10: 
yading@10: Return the maximum between I<x> and I<y>.
yading@10: 
yading@10: 
yading@10: =item B<mod(x, y)>
yading@10: 
yading@10: Compute the remainder of division of I<x> by I<y>.
yading@10: 
yading@10: 
yading@10: =item B<not(expr)>
yading@10: 
yading@10: Return 1.0 if I<expr> is zero, 0.0 otherwise.
yading@10: 
yading@10: 
yading@10: =item B<pow(x, y)>
yading@10: 
yading@10: Compute the power of I<x> elevated I<y>, it is equivalent to
yading@10: "(I<x>)^(I<y>)".
yading@10: 
yading@10: 
yading@10: =item B<print(t)>
yading@10: 
yading@10: 
yading@10: =item B<print(t, l)>
yading@10: 
yading@10: Print the value of expression I<t> with loglevel I<l>. If
yading@10: I<l> is not specified then a default log level is used.
yading@10: Returns the value of the expression printed.
yading@10: 
yading@10: Prints t with loglevel l
yading@10: 
yading@10: 
yading@10: =item B<random(x)>
yading@10: 
yading@10: Return a pseudo random value between 0.0 and 1.0. I<x> is the index of the
yading@10: internal variable which will be used to save the seed/state.
yading@10: 
yading@10: 
yading@10: =item B<root(expr, max)>
yading@10: 
yading@10: Find an input value for which the function represented by I<expr>
yading@10: with argument I<ld(0)> is 0 in the interval 0..I<max>.
yading@10: 
yading@10: The expression in I<expr> must denote a continuous function or the
yading@10: result is undefined.
yading@10: 
yading@10: I<ld(0)> 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: C<ld(0)>. When the expression evaluates to 0 then the
yading@10: corresponding input value will be returned.
yading@10: 
yading@10: 
yading@10: =item B<sin(x)>
yading@10: 
yading@10: Compute sine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<sinh(x)>
yading@10: 
yading@10: Compute hyperbolic sine of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<sqrt(expr)>
yading@10: 
yading@10: Compute the square root of I<expr>. This is equivalent to
yading@10: "(I<expr>)^.5".
yading@10: 
yading@10: 
yading@10: =item B<squish(x)>
yading@10: 
yading@10: Compute expression C<1/(1 + exp(4*x))>.
yading@10: 
yading@10: 
yading@10: =item B<st(var, expr)>
yading@10: 
yading@10: Allow to store the value of the expression I<expr> in an internal
yading@10: variable. I<var> 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: 
yading@10: 
yading@10: =item B<tan(x)>
yading@10: 
yading@10: Compute tangent of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<tanh(x)>
yading@10: 
yading@10: Compute hyperbolic tangent of I<x>.
yading@10: 
yading@10: 
yading@10: =item B<taylor(expr, x)>
yading@10: 
yading@10: 
yading@10: =item B<taylor(expr, x, id)>
yading@10: 
yading@10: Evaluate a Taylor series at I<x>, given an expression representing
yading@10: the C<ld(id)>-th derivative of a function at 0.
yading@10: 
yading@10: When the series does not converge the result is undefined.
yading@10: 
yading@10: I<ld(id)> is used to represent the derivative order in I<expr>,
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: C<ld(id)>. If I<id> is not specified then 0 is assumed.
yading@10: 
yading@10: Note, when you have the derivatives at y instead of 0,
yading@10: C<taylor(expr, x-y)> can be used.
yading@10: 
yading@10: 
yading@10: =item B<time(0)>
yading@10: 
yading@10: Return the current (wallclock) time in seconds.
yading@10: 
yading@10: 
yading@10: =item B<trunc(expr)>
yading@10: 
yading@10: Round the value of expression I<expr> towards zero to the nearest
yading@10: integer. For example, "trunc(-1.5)" is "-1.0".
yading@10: 
yading@10: 
yading@10: =item B<while(cond, expr)>
yading@10: 
yading@10: Evaluate expression I<expr> while the expression I<cond> is
yading@10: non-zero, and returns the value of the last I<expr> evaluation, or
yading@10: NAN if I<cond> was always false.
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: The following constants are available:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<PI>
yading@10: 
yading@10: area of the unit disc, approximately 3.14
yading@10: 
yading@10: =item B<E>
yading@10: 
yading@10: exp(1) (Euler's number), approximately 2.718
yading@10: 
yading@10: =item B<PHI>
yading@10: 
yading@10: golden ratio (1+sqrt(5))/2, approximately 1.618
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: Assuming that an expression is considered "true" if it has a non-zero
yading@10: value, note that:
yading@10: 
yading@10: C<*> works like AND
yading@10: 
yading@10: C<+> works like OR
yading@10: 
yading@10: For example the construct:
yading@10: 	
yading@10: 	if (A AND B) then C
yading@10: 
yading@10: is equivalent to:
yading@10: 	
yading@10: 	if(A*B, C)
yading@10: 
yading@10: 
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: 
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 'KB', 'MiB',
yading@10: 'G' and 'B' as number postfix.
yading@10: 
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: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<y>
yading@10: 
yading@10: 10^-24 / 2^-80
yading@10: 
yading@10: =item B<z>
yading@10: 
yading@10: 10^-21 / 2^-70
yading@10: 
yading@10: =item B<a>
yading@10: 
yading@10: 10^-18 / 2^-60
yading@10: 
yading@10: =item B<f>
yading@10: 
yading@10: 10^-15 / 2^-50
yading@10: 
yading@10: =item B<p>
yading@10: 
yading@10: 10^-12 / 2^-40
yading@10: 
yading@10: =item B<n>
yading@10: 
yading@10: 10^-9 / 2^-30
yading@10: 
yading@10: =item B<u>
yading@10: 
yading@10: 10^-6 / 2^-20
yading@10: 
yading@10: =item B<m>
yading@10: 
yading@10: 10^-3 / 2^-10
yading@10: 
yading@10: =item B<c>
yading@10: 
yading@10: 10^-2
yading@10: 
yading@10: =item B<d>
yading@10: 
yading@10: 10^-1
yading@10: 
yading@10: =item B<h>
yading@10: 
yading@10: 10^2
yading@10: 
yading@10: =item B<k>
yading@10: 
yading@10: 10^3 / 2^10
yading@10: 
yading@10: =item B<K>
yading@10: 
yading@10: 10^3 / 2^10
yading@10: 
yading@10: =item B<M>
yading@10: 
yading@10: 10^6 / 2^20
yading@10: 
yading@10: =item B<G>
yading@10: 
yading@10: 10^9 / 2^30
yading@10: 
yading@10: =item B<T>
yading@10: 
yading@10: 10^12 / 2^40
yading@10: 
yading@10: =item B<P>
yading@10: 
yading@10: 10^15 / 2^40
yading@10: 
yading@10: =item B<E>
yading@10: 
yading@10: 10^18 / 2^50
yading@10: 
yading@10: =item B<Z>
yading@10: 
yading@10: 10^21 / 2^60
yading@10: 
yading@10: =item B<Y>
yading@10: 
yading@10: 10^24 / 2^70
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 OPENCL OPTIONS
yading@10: 
yading@10: 
yading@10: When FFmpeg is configured with C<--enable-opencl>, it is possible
yading@10: to set the options for the global OpenCL context.
yading@10: 
yading@10: The list of supported options follows:
yading@10: 
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<build_options>
yading@10: 
yading@10: Set build options used to compile the registered kernels.
yading@10: 
yading@10: See reference "OpenCL Specification Version: 1.2 chapter 5.6.4".
yading@10: 
yading@10: 
yading@10: =item B<platform_idx>
yading@10: 
yading@10: Select the index of the platform to run OpenCL code.
yading@10: 
yading@10: The specified index must be one of the indexes in the device list
yading@10: which can be obtained with C<av_opencl_get_device_list()>.
yading@10: 
yading@10: 
yading@10: =item B<device_idx>
yading@10: 
yading@10: Select the index of the device used to run OpenCL code.
yading@10: 
yading@10: The specifed index must be one of the indexes in the device list which
yading@10: can be obtained with C<av_opencl_get_device_list()>.
yading@10: 
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 SEE ALSO
yading@10: 
yading@10: 
yading@10: 
yading@10: ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libavutil(3)
yading@10: 
yading@10: 
yading@10: =head1 AUTHORS
yading@10: 
yading@10: 
yading@10: The FFmpeg developers.
yading@10: 
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: B<git log> in the FFmpeg source directory, or browsing the
yading@10: online repository at E<lt>B<http://source.ffmpeg.org>E<gt>.
yading@10: 
yading@10: Maintainers for the specific components are listed in the file
yading@10: F<MAINTAINERS> in the source code tree.
yading@10: 
yading@10: 
yading@10: