Let's put it this way - if you're changing "resolution" (pixel
format) and/or refresh rate, then the vertical and horizontal
frequencies almost always change. No, there is nothing in the
sync rates that "denotes the resolution of the image", other than
the total number of lines per frame (and from this, and the
specific rates in question, the timing standard in use can usually
be identified). But no, since the analog video standard for PCs
does not include a true "blanking" or "display enable" signal
(nor anything from which these can readily be derived), you cannot
clearly identify the number of active lines per frame, which is
part of the pixel format description. You (or rather, your monitor)
are always basically guessing what standard timing is in use
(under the assumption that it IS in fact a standard timing).
No, there really aren't. IF you happen to be looking at an image
which consists of, say, alternating vertical lines, then yes, you can
tell where the "pixels" were supposed to be. Anything beyond
that is just a guess; again, there is NO pixel-level timing information
guaranteed in the VGA interface. You cannot unambiguously
determine the pixel locations within the video signal for any and
all video content. The best you can do is to try to generate a
pixel sampling clock from what timing information you DO have
(generally, just by multiplying up the horizontal sync rate) and
taking your best guess at how it should align with the active video
period.
Sure, but that's a specific (and very fortunate) case. Again,
there's no way to distinguish pixels within, say, a flat white
field, or a single HORIZONTAL line, so there's really no
guarantee of "discrete" values. This is one of the problems which
has traditionally plagued analog interfaces for fixed-format
displays (such as LCDs), since those DO require accurate sampling
at the pixel times. There is a new analog video signal standard
in the works which is designed to address this (the VESA NAVI
standard), but since it's not published yet I can't go into the details
of it here.
If you really want to get into the details of all this (and I guarantee
you that they're a LOT less interesting than you might think..
),
it's covered in chapters 6-9 of my book, "Display Interfaces:
Fundamentals & Standards," published by J. Wiley & Sons.
Bob M.