cvt modeline generator
libv at skynet.be
Sat Jan 7 06:42:15 PST 2006
On Sat, Jan 07, 2006 at 03:13:01PM +0100, Nicolas Mailhot wrote:
> I am wondering if the cvt modeline generator is still not slightly
> I've just stumbled on page 55 of this manual :
> which lists the standard frequencies and pixel clocks a video projector
> For example for 750*576 at 50 (SDTV, basically the mode you find on PAL
> DVDs) this document states:
> hsync: 31,25 kHz, field rate: 50 Hz, pclk: 27 MHz
> And the CVT generator will output:
> hsync: 29.58 kHz, field rate: 49.62 Hz, pclk: 26.50 MHz
> Which seems a lot less sane to me.
> Am I missing something ?
> Nicolas Mailhot
The mode is 720x576 at 50Hz, 750 isn't rounded to 8.
CVT rounds the pixelclock down to 250kHz, as done in the CVTd6r1.xls.
A dotclock of 26.75 gives you 50.09Hz.
Also, this is CVT timing, not a pre-defined mode. For instance; CVT will
generate modes with a VTotal of 596 while PAL would have a VTotal of 625.
You will not generate an exact PAL mode with gtf either.
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