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229 lines
5.0 KiB
Groff
229 lines
5.0 KiB
Groff
.TH fb.modes 8 "Aug 1996" local "Linux frame buffer utils"
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.SH NAME
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fb.modes \- frame buffer modes file
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.SH DESCRIPTION
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.I /etc/fb.modes
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contains an unlimited number of video mode descriptions. The general format
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of a video mode is:
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.sp
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mode
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.RI \" name \"
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.RS
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geometry
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.RI < xres >
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.RI < yres >
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.RI < vxres >
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.RI < vyres >
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.RI < depth >
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.br
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timings
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.RI < pixclock >
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.RI < left >
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.RI < right >
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.RI < upper >
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.RI < lower >
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.RI < hslen >
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.RI < vslen >
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.br
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.B options
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.RI < value >
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.RE
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endmode
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.SH OPTIONS
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geometry options:
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.RS
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.TP
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.I xres
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visible horizontal resolution (in pixels)
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.TP
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.I yres
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visible vertical resolution (in pixels)
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.TP
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.I vxres
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virtual horizontal resolution (in pixels)
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.TP
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.I vyres
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virtual vertical resolution (in pixels)
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.TP
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.I depth
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display depth (in bits per pixel)
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.RE
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.PP
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timing options:
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.RS
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.TP
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.I pixclock
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length of one pixel (in picoseconds)
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.TP
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.I left
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left margin (in pixels)
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.TP
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.I right
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right margin (in pixels)
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.TP
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.I upper
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upper margin (in pixel lines)
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.TP
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.I lower
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lower margin (in pixel lines)
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.TP
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.I hslen
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horizontal sync length (in pixels)
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.TP
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.I vslen
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vertical sync length (in pixel lines)
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.RE
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.PP
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other options:
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.RS
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the first value of this options is the default
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.TP
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.IR \fBhsync "\ {" low | high }
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the horizontal sync polarity
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.TP
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.IR \fBvsync "\ {" low | high }
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the vertical sync polarity
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.TP
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.IR \fBcsync "\ {" low | high }
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the composite sync polarity
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.TP
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.IR \fBextsync "\ {" false | true }
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enable or disable external resync. If enabled the sync timings are not
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generated by the frame buffer device and must be provided externally
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instead. Note that this option may not be supported by every frame buffer
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device
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.TP
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.IR \fBlaced "\ {" false | true }
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enable or disable interlace. If enabled the display will be split in two
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frames, each frame contains only even and odd lines respectively. These two
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frames will be displayed alternating, this way twice the lines can be
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displayed and the vertical frequency for monitor stays the same, but the
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visible vertical frequency gets halved
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.TP
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.IR \fBdouble "\ {" false | true }
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enable or disable doublescan. If enabled every line will be displayed twice
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and this way the horizontal frequency can easily be doubled, so that the
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same resolution can be displayed on different monitors, even if the
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horizontal frequency specification differs. Note that this option may not be
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supported by every frame buffer device
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.RE
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.SH INTERNALS
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Generally a frame buffer display is organized as follows:
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.sp
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.ad c
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+\-\-\-+\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-+\-\-\-+\-\-\-+
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " ^ "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " | "\ " \fI5 "\ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " v "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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+\-\-\-#################\-\-\-+\-\-\-+
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " ^ "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " | "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " | "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RI "| " 1 " # " \fB| " " 2 " # " 3 " | " 4 " |"
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.br
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.RB "|" "<\->" "#" "<\-\-\-\-\-\-+\-\-\-\-\-\->" "#" "<\->" "|" "<\->" "|"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " | "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " | "\ " \fI6 "\ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " | "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ #\ \ \ \ \ \ \ " v "\ \ \ \ \ \ \ #\ \ \ |\ \ \ |"
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.br
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+\-\-\-#################\-\-\-+\-\-\-+
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " ^ "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " | "\ " \fI7 "\ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " v "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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+\-\-\-+\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-+\-\-\-+\-\-\-+
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " ^ "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " | "\ " \fI8 "\ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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.RB "|\ \ \ |\ \ \ \ \ \ \ " v "\ \ \ \ \ \ \ |\ \ \ |\ \ \ |"
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.br
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+\-\-\-+\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-+\-\-\-+\-\-\-+
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.sp
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.ad n
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.RS
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.I 1
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\t left margin
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.br
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.I 2
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\t xres
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.br
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.I 3
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\t right margin
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.br
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.I 4
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\t horizontal sync len
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.br
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.I 5
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\t upper margin
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.br
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.I 6
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\t yres
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.br
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.I 7
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\t lower margin
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.br
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.I 8
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\t vertical sync len
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.RE
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.sp
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The area bordered with `#' is the visible display area. Horizontal and
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vertical frequencies can now easily be calculated, for this the sum of
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horizontal or vertical values are important
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.RS
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.sp
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htotal\ =\ left\ +\ xres\ +\ right\ +\ hslen
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.br
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vtotal\ =\ upper\ +\ yres\ +\ lower\ +\ vslen
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.sp
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.RE
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The length of one line can now be calculated with pixclock
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.RS
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.sp
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line\ =\ pixclock\ *\ htotal
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.sp
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.RE
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and we have the horizontal frequency
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.RS
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.sp
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hfreq\ =\ 1E12\ /\ line\ =\ 1E12\ /\ (pixclock\ *\ htotal)
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.sp
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.RE
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To get the vertical frequency vtotal must eventually adjusted. If the
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display is laced, vtotal must be halved or if the display is a doublescan
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one, vtotal must be doubled. Now we can calculate the length of one frame
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.RS
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.sp
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if\ (lace)\ \ \ vtotal\ /=\ 2
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.br
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if\ (double)\ vtotal\ *=\ 2
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.sp
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frame\ =\ vtotal\ *\ line
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.sp
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.RE
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and we get also the vertical frequency
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.RS
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.sp
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vfreq\ =\ 1E12\ /\ frame\ =\ hfreq\ /\ vtotal
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.sp
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.RE
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.SH SEE ALSO
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.BR fbset "(8), " fbdev (4)
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