On Mon, 2009-11-23 at 12:59 -0700, Michal Jaegermann wrote: > If we are already there then maybe you can explain? :-) > > 'man -k mode | grep VESA' prints > > cvt [] (1) - calculate VESA CVT mode lines > gtf [] (1) - calculate VESA GTF mode lines > > but what is a difference? 'man cvt' at least says "VESA Coordinated > Video Timing". V.E.R.A. for a change brings "Generalized Timing > Format (VESA)" when asked for "gtf". I am afraid that this still > does not tell me very much. Results with the same paramaters are > slightly different. 'xvidtune' allows to "tune" an image to your > monitor before you will hit "Show". They're both timing generation formulas. GTF is older, a bit more complex, and generally matches the physical requirements of CRTs. CVT is newer, simpler, and has a cheat code for reduced bandwidth consumption on LCDs. This is important, among other reasons, because the DVI link speed is 165MHz: atropine:~% cvt 1920 1200 60 # 1920x1200 59.88 Hz (CVT 2.30MA) hsync: 74.56 kHz; pclk: 193.25 MHz Modeline "1920x1200_60.00" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync atropine:~% cvt -r 1920 1200 60 # 1920x1200 59.95 Hz (CVT 2.30MA-R) hsync: 74.04 kHz; pclk: 154.00 MHz Modeline "1920x1200R" 154.00 1920 1968 2000 2080 1200 1203 1209 1235 +hsync -vsync and so a non-reduced-blanking timing for 1920x1200 won't fit on a single DVI link. tl;dr version: GTF for CRTs, CVT for LCDs. - ajax
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