1084 lines
22 KiB
Plaintext
1084 lines
22 KiB
Plaintext
@chapter Syntax
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@c man begin SYNTAX
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This section documents the syntax and formats employed by the FFmpeg
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libraries and tools.
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@anchor{quoting_and_escaping}
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@section Quoting and escaping
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FFmpeg adopts the following quoting and escaping mechanism, unless
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explicitly specified. The following rules are applied:
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@itemize
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@item
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@samp{'} and @samp{\} are special characters (respectively used for
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quoting and escaping). In addition to them, there might be other
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special characters depending on the specific syntax where the escaping
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and quoting are employed.
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@item
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A special character is escaped by prefixing it with a @samp{\}.
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@item
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All characters enclosed between @samp{''} are included literally in the
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parsed string. The quote character @samp{'} itself cannot be quoted,
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so you may need to close the quote and escape it.
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@item
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Leading and trailing whitespaces, unless escaped or quoted, are
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removed from the parsed string.
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@end itemize
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Note that you may need to add a second level of escaping when using
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the command line or a script, which depends on the syntax of the
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adopted shell language.
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The function @code{av_get_token} defined in
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@file{libavutil/avstring.h} can be used to parse a token quoted or
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escaped according to the rules defined above.
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The tool @file{tools/ffescape} in the FFmpeg source tree can be used
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to automatically quote or escape a string in a script.
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@subsection Examples
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@itemize
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@item
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Escape the string @code{Crime d'Amour} containing the @code{'} special
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character:
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@example
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Crime d\'Amour
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@end example
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@item
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The string above contains a quote, so the @code{'} needs to be escaped
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when quoting it:
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@example
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'Crime d'\''Amour'
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@end example
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@item
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Include leading or trailing whitespaces using quoting:
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@example
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' this string starts and ends with whitespaces '
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@end example
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@item
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Escaping and quoting can be mixed together:
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@example
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' The string '\'string\'' is a string '
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@end example
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@item
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To include a literal @samp{\} you can use either escaping or quoting:
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@example
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'c:\foo' can be written as c:\\foo
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@end example
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@end itemize
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@anchor{date syntax}
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@section Date
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The accepted syntax is:
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@example
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[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
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now
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@end example
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If the value is "now" it takes the current time.
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Time is local time unless Z is appended, in which case it is
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interpreted as UTC.
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If the year-month-day part is not specified it takes the current
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year-month-day.
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@anchor{time duration syntax}
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@section Time duration
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There are two accepted syntaxes for expressing time duration.
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@example
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[-][@var{HH}:]@var{MM}:@var{SS}[.@var{m}...]
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@end example
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@var{HH} expresses the number of hours, @var{MM} the number of minutes
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for a maximum of 2 digits, and @var{SS} the number of seconds for a
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maximum of 2 digits. The @var{m} at the end expresses decimal value for
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@var{SS}.
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@emph{or}
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@example
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[-]@var{S}+[.@var{m}...]
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@end example
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@var{S} expresses the number of seconds, with the optional decimal part
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@var{m}.
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In both expressions, the optional @samp{-} indicates negative duration.
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@subsection Examples
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The following examples are all valid time duration:
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@table @samp
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@item 55
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55 seconds
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@item 12:03:45
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12 hours, 03 minutes and 45 seconds
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@item 23.189
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23.189 seconds
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@end table
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@anchor{video size syntax}
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@section Video size
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Specify the size of the sourced video, it may be a string of the form
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@var{width}x@var{height}, or the name of a size abbreviation.
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The following abbreviations are recognized:
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@table @samp
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@item ntsc
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720x480
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@item pal
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720x576
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@item qntsc
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352x240
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@item qpal
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352x288
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@item sntsc
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640x480
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@item spal
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768x576
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@item film
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352x240
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@item ntsc-film
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352x240
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@item sqcif
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128x96
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@item qcif
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176x144
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@item cif
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352x288
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@item 4cif
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704x576
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@item 16cif
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1408x1152
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@item qqvga
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160x120
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@item qvga
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320x240
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@item vga
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640x480
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@item svga
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800x600
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@item xga
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1024x768
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@item uxga
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1600x1200
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@item qxga
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2048x1536
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@item sxga
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1280x1024
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@item qsxga
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2560x2048
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@item hsxga
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5120x4096
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@item wvga
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852x480
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@item wxga
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1366x768
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@item wsxga
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1600x1024
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@item wuxga
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1920x1200
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@item woxga
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2560x1600
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@item wqsxga
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3200x2048
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@item wquxga
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3840x2400
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@item whsxga
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6400x4096
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@item whuxga
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7680x4800
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@item cga
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320x200
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@item ega
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640x350
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@item hd480
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852x480
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@item hd720
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1280x720
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@item hd1080
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1920x1080
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@item 2k
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2048x1080
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@item 2kflat
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1998x1080
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@item 2kscope
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2048x858
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@item 4k
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4096x2160
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@item 4kflat
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3996x2160
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@item 4kscope
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4096x1716
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@item nhd
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640x360
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@item hqvga
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240x160
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@item wqvga
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400x240
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@item fwqvga
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432x240
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@item hvga
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480x320
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@item qhd
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960x540
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@item 2kdci
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2048x1080
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@item 4kdci
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4096x2160
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@item uhd2160
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3840x2160
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@item uhd4320
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7680x4320
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@end table
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@anchor{video rate syntax}
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@section Video rate
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Specify the frame rate of a video, expressed as the number of frames
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generated per second. It has to be a string in the format
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@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
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number or a valid video frame rate abbreviation.
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The following abbreviations are recognized:
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@table @samp
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@item ntsc
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30000/1001
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@item pal
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25/1
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@item qntsc
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30000/1001
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@item qpal
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25/1
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@item sntsc
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30000/1001
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@item spal
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25/1
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@item film
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24/1
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@item ntsc-film
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24000/1001
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@end table
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@anchor{ratio syntax}
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@section Ratio
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A ratio can be expressed as an expression, or in the form
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@var{numerator}:@var{denominator}.
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Note that a ratio with infinite (1/0) or negative value is
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considered valid, so you should check on the returned value if you
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want to exclude those values.
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The undefined value can be expressed using the "0:0" string.
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@anchor{color syntax}
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@section Color
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It can be the name of a color as defined below (case insensitive match) or a
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@code{[0x|#]RRGGBB[AA]} sequence, possibly followed by @@ and a string
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representing the alpha component.
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The alpha component may be a string composed by "0x" followed by an
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hexadecimal number or a decimal number between 0.0 and 1.0, which
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represents the opacity value (@samp{0x00} or @samp{0.0} means completely
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transparent, @samp{0xff} or @samp{1.0} completely opaque). If the alpha
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component is not specified then @samp{0xff} is assumed.
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The string @samp{random} will result in a random color.
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The following names of colors are recognized:
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@table @samp
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@item AliceBlue
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0xF0F8FF
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@item AntiqueWhite
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0xFAEBD7
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@item Aqua
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0x00FFFF
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@item Aquamarine
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0x7FFFD4
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@item Azure
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0xF0FFFF
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@item Beige
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0xF5F5DC
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@item Bisque
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0xFFE4C4
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@item Black
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0x000000
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@item BlanchedAlmond
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0xFFEBCD
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@item Blue
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0x0000FF
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@item BlueViolet
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0x8A2BE2
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@item Brown
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0xA52A2A
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@item BurlyWood
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0xDEB887
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@item CadetBlue
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0x5F9EA0
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@item Chartreuse
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0x7FFF00
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@item Chocolate
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0xD2691E
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@item Coral
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0xFF7F50
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@item CornflowerBlue
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0x6495ED
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@item Cornsilk
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0xFFF8DC
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@item Crimson
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0xDC143C
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@item Cyan
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0x00FFFF
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@item DarkBlue
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0x00008B
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@item DarkCyan
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0x008B8B
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@item DarkGoldenRod
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0xB8860B
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@item DarkGray
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0xA9A9A9
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@item DarkGreen
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0x006400
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@item DarkKhaki
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0xBDB76B
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@item DarkMagenta
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0x8B008B
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@item DarkOliveGreen
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0x556B2F
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@item Darkorange
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0xFF8C00
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@item DarkOrchid
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0x9932CC
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@item DarkRed
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0x8B0000
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@item DarkSalmon
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0xE9967A
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@item DarkSeaGreen
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0x8FBC8F
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@item DarkSlateBlue
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0x483D8B
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@item DarkSlateGray
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0x2F4F4F
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@item DarkTurquoise
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0x00CED1
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@item DarkViolet
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0x9400D3
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@item DeepPink
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0xFF1493
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@item DeepSkyBlue
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0x00BFFF
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@item DimGray
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0x696969
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@item DodgerBlue
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0x1E90FF
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@item FireBrick
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0xB22222
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@item FloralWhite
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0xFFFAF0
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@item ForestGreen
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0x228B22
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@item Fuchsia
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0xFF00FF
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@item Gainsboro
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0xDCDCDC
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@item GhostWhite
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0xF8F8FF
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@item Gold
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0xFFD700
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@item GoldenRod
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0xDAA520
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@item Gray
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0x808080
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@item Green
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0x008000
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@item GreenYellow
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0xADFF2F
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@item HoneyDew
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0xF0FFF0
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@item HotPink
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0xFF69B4
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@item IndianRed
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0xCD5C5C
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@item Indigo
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0x4B0082
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@item Ivory
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0xFFFFF0
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@item Khaki
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0xF0E68C
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@item Lavender
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0xE6E6FA
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@item LavenderBlush
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0xFFF0F5
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@item LawnGreen
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0x7CFC00
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@item LemonChiffon
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0xFFFACD
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@item LightBlue
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0xADD8E6
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@item LightCoral
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0xF08080
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@item LightCyan
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0xE0FFFF
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@item LightGoldenRodYellow
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0xFAFAD2
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@item LightGreen
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0x90EE90
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@item LightGrey
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0xD3D3D3
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@item LightPink
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0xFFB6C1
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@item LightSalmon
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0xFFA07A
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@item LightSeaGreen
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0x20B2AA
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@item LightSkyBlue
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0x87CEFA
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@item LightSlateGray
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0x778899
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@item LightSteelBlue
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0xB0C4DE
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@item LightYellow
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0xFFFFE0
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@item Lime
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0x00FF00
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@item LimeGreen
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0x32CD32
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@item Linen
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0xFAF0E6
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@item Magenta
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0xFF00FF
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@item Maroon
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0x800000
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@item MediumAquaMarine
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0x66CDAA
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@item MediumBlue
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0x0000CD
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@item MediumOrchid
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0xBA55D3
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@item MediumPurple
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0x9370D8
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@item MediumSeaGreen
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0x3CB371
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@item MediumSlateBlue
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0x7B68EE
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@item MediumSpringGreen
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0x00FA9A
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@item MediumTurquoise
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0x48D1CC
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@item MediumVioletRed
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0xC71585
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@item MidnightBlue
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0x191970
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@item MintCream
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0xF5FFFA
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@item MistyRose
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0xFFE4E1
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@item Moccasin
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0xFFE4B5
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@item NavajoWhite
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0xFFDEAD
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@item Navy
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0x000080
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@item OldLace
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0xFDF5E6
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@item Olive
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0x808000
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@item OliveDrab
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0x6B8E23
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@item Orange
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0xFFA500
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@item OrangeRed
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0xFF4500
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@item Orchid
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0xDA70D6
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@item PaleGoldenRod
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0xEEE8AA
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@item PaleGreen
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0x98FB98
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@item PaleTurquoise
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0xAFEEEE
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@item PaleVioletRed
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0xD87093
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@item PapayaWhip
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0xFFEFD5
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@item PeachPuff
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0xFFDAB9
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@item Peru
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0xCD853F
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@item Pink
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0xFFC0CB
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@item Plum
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0xDDA0DD
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@item PowderBlue
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0xB0E0E6
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@item Purple
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0x800080
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@item Red
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0xFF0000
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@item RosyBrown
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0xBC8F8F
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@item RoyalBlue
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0x4169E1
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@item SaddleBrown
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0x8B4513
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@item Salmon
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0xFA8072
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@item SandyBrown
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0xF4A460
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@item SeaGreen
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0x2E8B57
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@item SeaShell
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0xFFF5EE
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@item Sienna
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0xA0522D
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@item Silver
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0xC0C0C0
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@item SkyBlue
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0x87CEEB
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@item SlateBlue
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0x6A5ACD
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@item SlateGray
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0x708090
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@item Snow
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0xFFFAFA
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@item SpringGreen
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0x00FF7F
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@item SteelBlue
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0x4682B4
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@item Tan
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0xD2B48C
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@item Teal
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0x008080
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@item Thistle
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0xD8BFD8
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@item Tomato
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0xFF6347
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@item Turquoise
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0x40E0D0
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@item Violet
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0xEE82EE
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@item Wheat
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0xF5DEB3
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@item White
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0xFFFFFF
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@item WhiteSmoke
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0xF5F5F5
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@item Yellow
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0xFFFF00
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@item YellowGreen
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0x9ACD32
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@end table
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@anchor{channel layout syntax}
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@section Channel Layout
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|
|
A channel layout specifies the spatial disposition of the channels in
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a multi-channel audio stream. To specify a channel layout, FFmpeg
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makes use of a special syntax.
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|
|
Individual channels are identified by an id, as given by the table
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below:
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@table @samp
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@item FL
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front left
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@item FR
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front right
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@item FC
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front center
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@item LFE
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low frequency
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@item BL
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back left
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@item BR
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back right
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@item FLC
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front left-of-center
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@item FRC
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front right-of-center
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@item BC
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back center
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@item SL
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side left
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@item SR
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side right
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@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, followed by 'c', yielding the default channel
|
|
layout for that number of channels (see the function
|
|
@code{av_get_default_channel_layout}). Note that not all channel counts have a
|
|
default layout.
|
|
|
|
@item
|
|
a number of channels, in decimal, followed by 'C', yielding an unknown channel
|
|
layout with the specified number of channels. Note that not all channel layout
|
|
specification strings support unknown channel layouts.
|
|
|
|
@item
|
|
a channel layout mask, in hexadecimal starting with "0x" (see the
|
|
@code{AV_CH_*} macros in @file{libavutil/channel_layout.h}.
|
|
@end itemize
|
|
|
|
Before libavutil version 53 the trailing character "c" to specify a number of
|
|
channels was optional, but now it is required, while a channel layout mask can
|
|
also be specified as a decimal number (if and only if not followed by "c" or "C").
|
|
|
|
See also the function @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 atan2(x, y)
|
|
Compute principal value of the arc tangent of @var{y}/@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 minimum 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
|