[mythtv-users] PVR-150 (Model 1045) - $64.99 @ CompUSA + FAQ

Robert Denier denier at umr.edu
Fri Sep 9 02:39:15 UTC 2005

Normal video cards typically do 640x480 or 800x600 as typical modes your
allowed to run the tv out on.  Of the two 640x480 is pretty close the
the 720x480 that is the NTSC standard.  Of course the 720 doesn't mean
alot.  Dish network, for instance, uses 480x480 encoding.  (This is all
from my memory, but should be right.)

Now, the difference in 720 or 640 or 480 as the number of horizontal
datapoints, in some ways doesn't matter as much as correctly outputing
an interlaced signal.  (Yes sampling resolution matters, but quite often
your better off not capturing at the highest resolution possible,
especially if the original doesn't have that much detail or your final
copy is a lower bitrate.)

NTSC video uses 29.97 frames per second or twice that in fields.  So in
order to output the video without artifacts you have to sample in the
way the signal is sent, meaning 59.93 (or whatever) fields per second at
240 lines.  A field is all the even number or odd numbered lines.  So a
picture is made by drawing the even lines, then the odd numbered lines.
Both sets together are called a frame.

You also need to _output_ that information back the way you recorded it,
meaning each field cleanly output, if you want it to look the best.  It
seems to me that no tv cards properly support interlaced output but
instead just scan the section of memory where the progressive image is
rendered and output that with the end result possibly drawing a field
using part of two fields of video.

Where will you notice this?  Well mostly in action scenes, and most
people would probably have to look a bit to see it.  Of course I've also
seen tv out's that never properly use the entire tv screen so that could
be an issue with some cards as well.

Again the quality of tv out's vary.  Most here seems to think nvidia
beats ati, and from what I've seen the 350 is the best you can do.  I
don't have one, so I can't tell for sure myself..

Thats about the best I can do in about 10 minutes, although to be honest
you can find better explanations just by searching google.  Google can
be very useful in such endeavors..

On Thu, 2005-09-08 at 19:10 -0700, Blake wrote:
> On Thu, 08 Sep 2005 19:05:52 -0700, Robert Denier <denier at umr.edu> wrote:
> > In fairness I'd think the 350 is about the only way to get s-video truly
> > correct.  Of course if you don't need s-video then yes, the 350 would
> > seem silly to me...
> Sorry, what does that mean: "s-video truly correct"? Are we talking  
> resolution or...what?
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