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1268 lines
24 KiB
Plaintext
1268 lines
24 KiB
Plaintext
FFMPEG-UTILS(1) FFMPEG-UTILS(1)
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NAME
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ffmpeg-utils - FFmpeg utilities
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DESCRIPTION
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This document describes some generic features and utilities provided by
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the libavutil library.
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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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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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o ' and \ are special characters (respectively used for quoting and
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escaping). In addition to them, there might be other special
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characters depending on the specific syntax where the escaping and
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quoting are employed.
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o A special character is escaped by prefixing it with a \.
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o All characters enclosed between '' are included literally in the
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parsed string. The quote character ' itself cannot be quoted, so
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you may need to close the quote and escape it.
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o Leading and trailing whitespaces, unless escaped or quoted, are
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removed from the parsed string.
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Note that you may need to add a second level of escaping when using the
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command line or a script, which depends on the syntax of the adopted
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shell language.
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The function "av_get_token" defined in libavutil/avstring.h can be used
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to parse a token quoted or escaped according to the rules defined
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above.
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The tool tools/ffescape in the FFmpeg source tree can be used to
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automatically quote or escape a string in a script.
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Examples
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o Escape the string "Crime d'Amour" containing the "'" special
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character:
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Crime d\'Amour
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o The string above contains a quote, so the "'" needs to be escaped
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when quoting it:
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'Crime d'\''Amour'
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o Include leading or trailing whitespaces using quoting:
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' this string starts and ends with whitespaces '
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o Escaping and quoting can be mixed together:
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' The string '\'string\'' is a string '
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o To include a literal \ you can use either escaping or quoting:
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'c:\foo' can be written as c:\\foo
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Date
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The accepted syntax is:
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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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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. If the year-month-day part is not specified it
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takes the current year-month-day.
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Time duration
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There are two accepted syntaxes for expressing time duration.
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[-][<HH>:]<MM>:<SS>[.<m>...]
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HH expresses the number of hours, MM the number of minutes for a
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maximum of 2 digits, and SS the number of seconds for a maximum of 2
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digits. The m at the end expresses decimal value for SS.
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or
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[-]<S>+[.<m>...][s|ms|us]
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S expresses the number of seconds, with the optional decimal part m.
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The optional literal suffixes s, ms or us indicate to interpret the
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value as seconds, milliseconds or microseconds, respectively.
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In both expressions, the optional - indicates negative duration.
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Examples
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The following examples are all valid time duration:
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55 55 seconds
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0.2 0.2 seconds
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200ms
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200 milliseconds, that's 0.2s
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200000us
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200000 microseconds, that's 0.2s
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12:03:45
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12 hours, 03 minutes and 45 seconds
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23.189
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23.189 seconds
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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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widthxheight, or the name of a size abbreviation.
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The following abbreviations are recognized:
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ntsc
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720x480
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pal 720x576
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qntsc
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352x240
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qpal
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352x288
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sntsc
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640x480
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spal
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768x576
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film
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352x240
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ntsc-film
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352x240
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sqcif
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128x96
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qcif
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176x144
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cif 352x288
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4cif
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704x576
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16cif
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1408x1152
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qqvga
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160x120
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qvga
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320x240
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vga 640x480
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svga
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800x600
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xga 1024x768
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uxga
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1600x1200
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qxga
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2048x1536
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sxga
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1280x1024
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qsxga
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2560x2048
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hsxga
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5120x4096
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wvga
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852x480
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wxga
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1366x768
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wsxga
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1600x1024
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wuxga
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1920x1200
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woxga
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2560x1600
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wqsxga
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3200x2048
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wquxga
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3840x2400
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whsxga
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6400x4096
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whuxga
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7680x4800
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cga 320x200
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ega 640x350
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hd480
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852x480
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hd720
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1280x720
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hd1080
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1920x1080
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2k 2048x1080
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2kflat
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1998x1080
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2kscope
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2048x858
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4k 4096x2160
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4kflat
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3996x2160
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4kscope
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4096x1716
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nhd 640x360
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hqvga
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240x160
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wqvga
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400x240
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fwqvga
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432x240
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hvga
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480x320
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qhd 960x540
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2kdci
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2048x1080
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4kdci
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4096x2160
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uhd2160
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3840x2160
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uhd4320
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7680x4320
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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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frame_rate_num/frame_rate_den, an integer number, a float number or a
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valid video frame rate abbreviation.
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The following abbreviations are recognized:
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ntsc
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30000/1001
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pal 25/1
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qntsc
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30000/1001
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qpal
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25/1
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sntsc
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30000/1001
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spal
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25/1
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film
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24/1
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ntsc-film
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24000/1001
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Ratio
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A ratio can be expressed as an expression, or in the form
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numerator:denominator.
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Note that a ratio with infinite (1/0) or negative value is considered
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valid, so you should check on the returned value if you want to exclude
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those values.
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The undefined value can be expressed using the "0:0" string.
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Color
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It can be the name of a color as defined below (case insensitive match)
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or a "[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 (0x00 or 0.0 means completely transparent,
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0xff or 1.0 completely opaque). If the alpha component is not specified
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then 0xff is assumed.
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The string random will result in a random color.
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The following names of colors are recognized:
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AliceBlue
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0xF0F8FF
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AntiqueWhite
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0xFAEBD7
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Aqua
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0x00FFFF
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Aquamarine
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0x7FFFD4
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Azure
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0xF0FFFF
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Beige
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0xF5F5DC
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Bisque
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0xFFE4C4
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Black
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0x000000
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BlanchedAlmond
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0xFFEBCD
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Blue
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0x0000FF
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BlueViolet
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0x8A2BE2
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Brown
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0xA52A2A
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BurlyWood
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0xDEB887
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CadetBlue
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0x5F9EA0
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Chartreuse
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0x7FFF00
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Chocolate
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0xD2691E
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Coral
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0xFF7F50
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CornflowerBlue
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0x6495ED
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Cornsilk
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0xFFF8DC
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Crimson
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0xDC143C
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Cyan
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0x00FFFF
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DarkBlue
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0x00008B
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DarkCyan
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0x008B8B
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DarkGoldenRod
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0xB8860B
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DarkGray
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0xA9A9A9
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DarkGreen
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0x006400
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DarkKhaki
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0xBDB76B
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DarkMagenta
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0x8B008B
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DarkOliveGreen
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0x556B2F
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Darkorange
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0xFF8C00
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DarkOrchid
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0x9932CC
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DarkRed
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0x8B0000
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DarkSalmon
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0xE9967A
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DarkSeaGreen
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0x8FBC8F
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DarkSlateBlue
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0x483D8B
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DarkSlateGray
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0x2F4F4F
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DarkTurquoise
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0x00CED1
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DarkViolet
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0x9400D3
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DeepPink
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0xFF1493
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DeepSkyBlue
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0x00BFFF
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DimGray
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0x696969
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DodgerBlue
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0x1E90FF
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FireBrick
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0xB22222
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FloralWhite
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0xFFFAF0
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ForestGreen
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0x228B22
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Fuchsia
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0xFF00FF
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Gainsboro
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0xDCDCDC
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GhostWhite
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0xF8F8FF
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Gold
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0xFFD700
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GoldenRod
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0xDAA520
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Gray
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0x808080
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Green
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0x008000
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GreenYellow
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0xADFF2F
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HoneyDew
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0xF0FFF0
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HotPink
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0xFF69B4
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IndianRed
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0xCD5C5C
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Indigo
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0x4B0082
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Ivory
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0xFFFFF0
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Khaki
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0xF0E68C
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Lavender
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0xE6E6FA
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LavenderBlush
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0xFFF0F5
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LawnGreen
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0x7CFC00
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LemonChiffon
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0xFFFACD
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LightBlue
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0xADD8E6
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LightCoral
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0xF08080
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LightCyan
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0xE0FFFF
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LightGoldenRodYellow
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0xFAFAD2
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LightGreen
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0x90EE90
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LightGrey
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0xD3D3D3
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LightPink
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0xFFB6C1
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LightSalmon
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0xFFA07A
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LightSeaGreen
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0x20B2AA
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LightSkyBlue
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0x87CEFA
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LightSlateGray
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0x778899
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LightSteelBlue
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0xB0C4DE
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LightYellow
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0xFFFFE0
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Lime
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0x00FF00
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LimeGreen
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0x32CD32
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Linen
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0xFAF0E6
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Magenta
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0xFF00FF
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Maroon
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0x800000
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MediumAquaMarine
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0x66CDAA
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MediumBlue
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0x0000CD
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MediumOrchid
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0xBA55D3
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MediumPurple
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0x9370D8
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MediumSeaGreen
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0x3CB371
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MediumSlateBlue
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0x7B68EE
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MediumSpringGreen
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0x00FA9A
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MediumTurquoise
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0x48D1CC
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MediumVioletRed
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0xC71585
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MidnightBlue
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0x191970
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MintCream
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0xF5FFFA
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MistyRose
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0xFFE4E1
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Moccasin
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0xFFE4B5
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NavajoWhite
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0xFFDEAD
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Navy
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0x000080
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OldLace
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0xFDF5E6
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Olive
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0x808000
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OliveDrab
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0x6B8E23
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Orange
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0xFFA500
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OrangeRed
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0xFF4500
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Orchid
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0xDA70D6
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PaleGoldenRod
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0xEEE8AA
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PaleGreen
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0x98FB98
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PaleTurquoise
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0xAFEEEE
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PaleVioletRed
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0xD87093
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PapayaWhip
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0xFFEFD5
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PeachPuff
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0xFFDAB9
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Peru
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0xCD853F
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Pink
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0xFFC0CB
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Plum
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0xDDA0DD
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PowderBlue
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0xB0E0E6
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Purple
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0x800080
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Red 0xFF0000
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RosyBrown
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0xBC8F8F
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RoyalBlue
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0x4169E1
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SaddleBrown
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0x8B4513
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Salmon
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0xFA8072
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SandyBrown
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0xF4A460
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SeaGreen
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0x2E8B57
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SeaShell
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0xFFF5EE
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Sienna
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0xA0522D
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Silver
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0xC0C0C0
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SkyBlue
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0x87CEEB
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SlateBlue
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0x6A5ACD
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SlateGray
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0x708090
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Snow
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0xFFFAFA
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SpringGreen
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0x00FF7F
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SteelBlue
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0x4682B4
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Tan 0xD2B48C
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Teal
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0x008080
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Thistle
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0xD8BFD8
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Tomato
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0xFF6347
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Turquoise
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0x40E0D0
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Violet
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0xEE82EE
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Wheat
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0xF5DEB3
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White
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0xFFFFFF
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WhiteSmoke
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0xF5F5F5
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Yellow
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0xFFFF00
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YellowGreen
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0x9ACD32
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Channel Layout
|
|
A channel layout specifies the spatial disposition of the channels in a
|
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multi-channel audio stream. To specify a channel layout, FFmpeg makes
|
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use of a special syntax.
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|
|
Individual channels are identified by an id, as given by the table
|
|
below:
|
|
|
|
FL front left
|
|
|
|
FR front right
|
|
|
|
FC front center
|
|
|
|
LFE low frequency
|
|
|
|
BL back left
|
|
|
|
BR back right
|
|
|
|
FLC front left-of-center
|
|
|
|
FRC front right-of-center
|
|
|
|
BC back center
|
|
|
|
SL side left
|
|
|
|
SR side right
|
|
|
|
TC top center
|
|
|
|
TFL top front left
|
|
|
|
TFC top front center
|
|
|
|
TFR top front right
|
|
|
|
TBL top back left
|
|
|
|
TBC top back center
|
|
|
|
TBR top back right
|
|
|
|
DL downmix left
|
|
|
|
DR downmix right
|
|
|
|
WL wide left
|
|
|
|
WR wide right
|
|
|
|
SDL surround direct left
|
|
|
|
SDR surround direct right
|
|
|
|
LFE2
|
|
low frequency 2
|
|
|
|
Standard channel layout compositions can be specified by using the
|
|
following identifiers:
|
|
|
|
mono
|
|
FC
|
|
|
|
stereo
|
|
FL+FR
|
|
|
|
2.1 FL+FR+LFE
|
|
|
|
3.0 FL+FR+FC
|
|
|
|
3.0(back)
|
|
FL+FR+BC
|
|
|
|
4.0 FL+FR+FC+BC
|
|
|
|
quad
|
|
FL+FR+BL+BR
|
|
|
|
quad(side)
|
|
FL+FR+SL+SR
|
|
|
|
3.1 FL+FR+FC+LFE
|
|
|
|
5.0 FL+FR+FC+BL+BR
|
|
|
|
5.0(side)
|
|
FL+FR+FC+SL+SR
|
|
|
|
4.1 FL+FR+FC+LFE+BC
|
|
|
|
5.1 FL+FR+FC+LFE+BL+BR
|
|
|
|
5.1(side)
|
|
FL+FR+FC+LFE+SL+SR
|
|
|
|
6.0 FL+FR+FC+BC+SL+SR
|
|
|
|
6.0(front)
|
|
FL+FR+FLC+FRC+SL+SR
|
|
|
|
3.1.2
|
|
FL+FR+FC+LFE+TFL+TFR
|
|
|
|
hexagonal
|
|
FL+FR+FC+BL+BR+BC
|
|
|
|
6.1 FL+FR+FC+LFE+BC+SL+SR
|
|
|
|
6.1 FL+FR+FC+LFE+BL+BR+BC
|
|
|
|
6.1(front)
|
|
FL+FR+LFE+FLC+FRC+SL+SR
|
|
|
|
7.0 FL+FR+FC+BL+BR+SL+SR
|
|
|
|
7.0(front)
|
|
FL+FR+FC+FLC+FRC+SL+SR
|
|
|
|
7.1 FL+FR+FC+LFE+BL+BR+SL+SR
|
|
|
|
7.1(wide)
|
|
FL+FR+FC+LFE+BL+BR+FLC+FRC
|
|
|
|
7.1(wide-side)
|
|
FL+FR+FC+LFE+FLC+FRC+SL+SR
|
|
|
|
5.1.2
|
|
FL+FR+FC+LFE+BL+BR+TFL+TFR
|
|
|
|
octagonal
|
|
FL+FR+FC+BL+BR+BC+SL+SR
|
|
|
|
cube
|
|
FL+FR+BL+BR+TFL+TFR+TBL+TBR
|
|
|
|
5.1.4
|
|
FL+FR+FC+LFE+BL+BR+TFL+TFR+TBL+TBR
|
|
|
|
7.1.2
|
|
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR
|
|
|
|
7.1.4
|
|
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBL+TBR
|
|
|
|
7.2.3
|
|
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBC+LFE2
|
|
|
|
9.1.4
|
|
FL+FR+FC+LFE+BL+BR+FLC+FRC+SL+SR+TFL+TFR+TBL+TBR
|
|
|
|
hexadecagonal
|
|
FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
|
|
|
|
downmix
|
|
DL+DR
|
|
|
|
22.2
|
|
FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
|
|
|
|
A custom channel layout can be specified as a sequence of terms,
|
|
separated by '+'. Each term can be:
|
|
|
|
o the name of a single channel (e.g. FL, FR, FC, LFE, etc.), each
|
|
optionally containing a custom name after a '@', (e.g. FL@Left,
|
|
FR@Right, FC@Center, LFE@Low_Frequency, etc.)
|
|
|
|
A standard channel layout can be specified by the following:
|
|
|
|
o the name of a single channel (e.g. FL, FR, FC, LFE, etc.)
|
|
|
|
o the name of a standard channel layout (e.g. mono, stereo, 4.0,
|
|
quad, 5.0, etc.)
|
|
|
|
o a number of channels, in decimal, followed by 'c', yielding the
|
|
default channel layout for that number of channels (see the
|
|
function "av_channel_layout_default"). Note that not all channel
|
|
counts have a default layout.
|
|
|
|
o 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.
|
|
|
|
o a channel layout mask, in hexadecimal starting with "0x" (see the
|
|
"AV_CH_*" macros in libavutil/channel_layout.h.
|
|
|
|
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 "av_channel_layout_from_string" defined in
|
|
libavutil/channel_layout.h.
|
|
|
|
EXPRESSION EVALUATION
|
|
When evaluating an arithmetic expression, FFmpeg uses an internal
|
|
formula evaluator, implemented through the libavutil/eval.h interface.
|
|
|
|
An expression may contain unary, binary operators, constants, and
|
|
functions.
|
|
|
|
Two expressions expr1 and expr2 can be combined to form another
|
|
expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and
|
|
the new expression evaluates to the value of expr2.
|
|
|
|
The following binary operators are available: "+", "-", "*", "/", "^".
|
|
|
|
The following unary operators are available: "+", "-".
|
|
|
|
The following functions are available:
|
|
|
|
abs(x)
|
|
Compute absolute value of x.
|
|
|
|
acos(x)
|
|
Compute arccosine of x.
|
|
|
|
asin(x)
|
|
Compute arcsine of x.
|
|
|
|
atan(x)
|
|
Compute arctangent of x.
|
|
|
|
atan2(y, x)
|
|
Compute principal value of the arc tangent of y/x.
|
|
|
|
between(x, min, max)
|
|
Return 1 if x is greater than or equal to min and lesser than or
|
|
equal to max, 0 otherwise.
|
|
|
|
bitand(x, y)
|
|
bitor(x, y)
|
|
Compute bitwise and/or operation on x and y.
|
|
|
|
The results of the evaluation of x and 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).
|
|
|
|
ceil(expr)
|
|
Round the value of expression expr upwards to the nearest integer.
|
|
For example, "ceil(1.5)" is "2.0".
|
|
|
|
clip(x, min, max)
|
|
Return the value of x clipped between min and max.
|
|
|
|
cos(x)
|
|
Compute cosine of x.
|
|
|
|
cosh(x)
|
|
Compute hyperbolic cosine of x.
|
|
|
|
eq(x, y)
|
|
Return 1 if x and y are equivalent, 0 otherwise.
|
|
|
|
exp(x)
|
|
Compute exponential of x (with base "e", the Euler's number).
|
|
|
|
floor(expr)
|
|
Round the value of expression expr downwards to the nearest
|
|
integer. For example, "floor(-1.5)" is "-2.0".
|
|
|
|
gauss(x)
|
|
Compute Gauss function of x, corresponding to "exp(-x*x/2) /
|
|
sqrt(2*PI)".
|
|
|
|
gcd(x, y)
|
|
Return the greatest common divisor of x and y. If both x and y are
|
|
0 or either or both are less than zero then behavior is undefined.
|
|
|
|
gt(x, y)
|
|
Return 1 if x is greater than y, 0 otherwise.
|
|
|
|
gte(x, y)
|
|
Return 1 if x is greater than or equal to y, 0 otherwise.
|
|
|
|
hypot(x, y)
|
|
This function is similar to the C function with the same name; it
|
|
returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right
|
|
triangle with sides of length x and y, or the distance of the point
|
|
(x, y) from the origin.
|
|
|
|
if(x, y)
|
|
Evaluate x, and if the result is non-zero return the result of the
|
|
evaluation of y, return 0 otherwise.
|
|
|
|
if(x, y, z)
|
|
Evaluate x, and if the result is non-zero return the evaluation
|
|
result of y, otherwise the evaluation result of z.
|
|
|
|
ifnot(x, y)
|
|
Evaluate x, and if the result is zero return the result of the
|
|
evaluation of y, return 0 otherwise.
|
|
|
|
ifnot(x, y, z)
|
|
Evaluate x, and if the result is zero return the evaluation result
|
|
of y, otherwise the evaluation result of z.
|
|
|
|
isinf(x)
|
|
Return 1.0 if x is +/-INFINITY, 0.0 otherwise.
|
|
|
|
isnan(x)
|
|
Return 1.0 if x is NAN, 0.0 otherwise.
|
|
|
|
ld(var)
|
|
Load the value of the internal variable with number var, which was
|
|
previously stored with st(var, expr). The function returns the
|
|
loaded value.
|
|
|
|
lerp(x, y, z)
|
|
Return linear interpolation between x and y by amount of z.
|
|
|
|
log(x)
|
|
Compute natural logarithm of x.
|
|
|
|
lt(x, y)
|
|
Return 1 if x is lesser than y, 0 otherwise.
|
|
|
|
lte(x, y)
|
|
Return 1 if x is lesser than or equal to y, 0 otherwise.
|
|
|
|
max(x, y)
|
|
Return the maximum between x and y.
|
|
|
|
min(x, y)
|
|
Return the minimum between x and y.
|
|
|
|
mod(x, y)
|
|
Compute the remainder of division of x by y.
|
|
|
|
not(expr)
|
|
Return 1.0 if expr is zero, 0.0 otherwise.
|
|
|
|
pow(x, y)
|
|
Compute the power of x elevated y, it is equivalent to "(x)^(y)".
|
|
|
|
print(t)
|
|
print(t, l)
|
|
Print the value of expression t with loglevel l. If l is not
|
|
specified then a default log level is used. Returns the value of
|
|
the expression printed.
|
|
|
|
Prints t with loglevel l
|
|
|
|
random(idx)
|
|
Return a pseudo random value between 0.0 and 1.0. idx is the index
|
|
of the internal variable which will be used to save the seed/state.
|
|
|
|
randomi(idx, min, max)
|
|
Return a pseudo random value in the interval between min and max.
|
|
idx is the index of the internal variable which will be used to
|
|
save the seed/state.
|
|
|
|
root(expr, max)
|
|
Find an input value for which the function represented by expr with
|
|
argument ld(0) is 0 in the interval 0..max.
|
|
|
|
The expression in expr must denote a continuous function or the
|
|
result is undefined.
|
|
|
|
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 ld(0).
|
|
When the expression evaluates to 0 then the corresponding input
|
|
value will be returned.
|
|
|
|
round(expr)
|
|
Round the value of expression expr to the nearest integer. For
|
|
example, "round(1.5)" is "2.0".
|
|
|
|
sgn(x)
|
|
Compute sign of x.
|
|
|
|
sin(x)
|
|
Compute sine of x.
|
|
|
|
sinh(x)
|
|
Compute hyperbolic sine of x.
|
|
|
|
sqrt(expr)
|
|
Compute the square root of expr. This is equivalent to "(expr)^.5".
|
|
|
|
squish(x)
|
|
Compute expression "1/(1 + exp(4*x))".
|
|
|
|
st(var, expr)
|
|
Store the value of the expression expr in an internal variable. 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.
|
|
|
|
tan(x)
|
|
Compute tangent of x.
|
|
|
|
tanh(x)
|
|
Compute hyperbolic tangent of x.
|
|
|
|
taylor(expr, x)
|
|
taylor(expr, x, id)
|
|
Evaluate a Taylor series at x, given an expression representing the
|
|
"ld(id)"-th derivative of a function at 0.
|
|
|
|
When the series does not converge the result is undefined.
|
|
|
|
ld(id) is used to represent the derivative order in expr, which
|
|
means that the given expression will be evaluated multiple times
|
|
with various input values that the expression can access through
|
|
"ld(id)". If id is not specified then 0 is assumed.
|
|
|
|
Note, when you have the derivatives at y instead of 0,
|
|
"taylor(expr, x-y)" can be used.
|
|
|
|
time(0)
|
|
Return the current (wallclock) time in seconds.
|
|
|
|
trunc(expr)
|
|
Round the value of expression expr towards zero to the nearest
|
|
integer. For example, "trunc(-1.5)" is "-1.0".
|
|
|
|
while(cond, expr)
|
|
Evaluate expression expr while the expression cond is non-zero, and
|
|
returns the value of the last expr evaluation, or NAN if cond was
|
|
always false.
|
|
|
|
The following constants are available:
|
|
|
|
PI area of the unit disc, approximately 3.14
|
|
|
|
E exp(1) (Euler's number), approximately 2.718
|
|
|
|
PHI golden ratio (1+sqrt(5))/2, approximately 1.618
|
|
|
|
Assuming that an expression is considered "true" if it has a non-zero
|
|
value, note that:
|
|
|
|
"*" works like AND
|
|
|
|
"+" works like OR
|
|
|
|
For example the construct:
|
|
|
|
if (A AND B) then C
|
|
|
|
is equivalent to:
|
|
|
|
if(A*B, C)
|
|
|
|
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.
|
|
|
|
y 10^-24 / 2^-80
|
|
|
|
z 10^-21 / 2^-70
|
|
|
|
a 10^-18 / 2^-60
|
|
|
|
f 10^-15 / 2^-50
|
|
|
|
p 10^-12 / 2^-40
|
|
|
|
n 10^-9 / 2^-30
|
|
|
|
u 10^-6 / 2^-20
|
|
|
|
m 10^-3 / 2^-10
|
|
|
|
c 10^-2
|
|
|
|
d 10^-1
|
|
|
|
h 10^2
|
|
|
|
k 10^3 / 2^10
|
|
|
|
K 10^3 / 2^10
|
|
|
|
M 10^6 / 2^20
|
|
|
|
G 10^9 / 2^30
|
|
|
|
T 10^12 / 2^40
|
|
|
|
P 10^15 / 2^50
|
|
|
|
E 10^18 / 2^60
|
|
|
|
Z 10^21 / 2^70
|
|
|
|
Y 10^24 / 2^80
|
|
|
|
SEE ALSO
|
|
ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3)
|
|
|
|
AUTHORS
|
|
The FFmpeg developers.
|
|
|
|
For details about the authorship, see the Git history of the project
|
|
(https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
|
|
the FFmpeg source directory, or browsing the online repository at
|
|
<https://git.ffmpeg.org/ffmpeg>.
|
|
|
|
Maintainers for the specific components are listed in the file
|
|
MAINTAINERS in the source code tree.
|
|
|
|
FFMPEG-UTILS(1)
|