[mythtv-users] HDTV Video Modes with MythTV

[James Oltman]

Yeah you are right.  I caught that after I sent it.  I meant to say 1,
3, 5 etc all the way to 1079 then 2, 4, 6 , etc to 1080.  That is your
interlaced frame.  540p is 1 field of 540 lines then another UPDATED
field of 540 lines.  This makes the picture look smoother.  In 1080i
you have a total of 1080 lines but they are made up of 2 fields of 540
lines.  So in actuallity, the 540p might look better because it is
smoother.  If you want the ultimate go with 1080p.  I think only CRT
projectors can handle it.

On 8/12/05, Hamish Moffatt <hamish at cloud.net.au> wrote:
> On Thu, Aug 11, 2005 at 09:17:26AM -0500, James Oltman wrote:
> > On 8/11/05, Hamish Moffatt <hamish at cloud.net.au> wrote:
> > > However in 1080i you have 1080 lines, updated 30 times per second.
> > > In 540p, you only have 540 lines! The resolution is halved, and it's
> > > not much more than 480i.
> >
> > You are confusing frames, and fields.  In 1080i, you have 2 fields of
> > 540 lines a piece.  The first field uses lines 1, 3, 5, etc all the
> > way to 539 or whatever.  The second field uses lines 2, 4, 6, 8 etc
> > all the way to 540.  Those two fields equal one frame of 1080i (i =
> > interlaced).  When you have 540p you are actually writing all 540
> > lines in both fields, thus making for a cleaner, smoother picture.  If
> 
> Yes, this is true. But, you only have 540 lines! You wrote them twice as
> often, but there were only 540 unique lines. In 1080i mode, you have
> 1080 unique lines updated half as often.
> 
> Theoretically you could make it equivalent to 1080i by displaying
> alternating lines (odd/even) of a 1080 line frame on your 540p display.
> ie perform the interlacing in software.
> 
> > anyone can add/correct me, please chime in.  I am fairly certain that
> > is how this works.  It's been about a year since I played with HDTV
> > modelines.
> 
> That is how it works, but it does not make them equivalent.
> 
> 
> cheers
> Hamish
> --
> Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>
> 
> 
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