[opendtv] Re: HDTV Buyer's Guide 2008

  • From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 24 Jan 2008 21:56:46 -0800 (PST)

XStreamXP plans direct-to-home 1080p  SAT broadcasts...
 coming end of this year:

Cable systems also are considering sending 1080p via
next gen IPTV/MPEG4 capable STB/DVR/iDCR HDTVs.

ALIS alternately paints interlaced fields, 540 lines at a time,
with half a line offset between pixes, as explained here:

So the "internal 1080p @ 60 Hz" panel mimics the
quick-and-easy CRT display process....and does NOT need
to perform a problematic prediction process to deinterleave 1080i....
your eyeballs do the work.

The result from my 3-year old Hitachi is a superior display
picture compared to nearly any 720/768p set I've seen.

Hitachi, et.al. make 1366x768, 1024x1024  & 1280x1024 ALIS panels.
Although they may not support the full 1920 pixels horizontally,
the ALIS cost containment approach isn't all that bad considering
Cable STBs have a hard time conveying even 1300 pixel rez
and many SAT/Cable feeds have undergone
downrezzing (HD-Lite) to 1280...and even 1024.

Recall that ALIS technology came out when 720/768p DLPs
and LCDs were throwing away every other 1080i frame...
resulting in 540p vertical resolution....hence the hype wrt
1080p.....and now 120 Hz refresh....to finally exceed ALIS....


Craig Birkmaier <craig@xxxxxxxxx> wrote: At 12:14 PM -0500 1/24/08, Manfredi, 
Albert E wrote:
>The one *possible* excuse for writing 1080i is the vertical interlace
>scheme of some displays, where the 1920 pixels are painted in two groups
>of 960. It's a stretch to call that 1080i. Maybe 1920i makes more sense.

I do not know of any display that ever did this.

The ALIS technology was a cheap way to scan a plasma panel using 
traditional interlacing techniques. IN essence they scan 540 lines 
per field then shift the fields up and down one pixel for playout.

>Most of the time, all 1080i seems to mean is that the input signal, e.g.
>HDMI, cannot reach 1080 at 60p. If I decipher the confused marketese

Actually, I think the new versions of HDMI can go well beyond 1080@60P.

 From Wikipedia: http://en.wikipedia.org/wiki/HDMI

Devices are manufactured to adhere to various versions of the 
specification, where each version is given a number, such as 1.0 or 
1.3. Each subsequent version of the specification uses the same 
cables, but increases the throughput and/or capabilities of what can 
be transmitted over the cable. For example, previously, the maximum 
pixel clock rate of the interface was 165 MHz, sufficient for 
supporting 1080p at 60 Hz or WUXGA (1920x1200), but HDMI 1.3 
increased that to 340 MHz, providing support for WQXGA (2560x1600) 
and beyond across a single digital link.

The problem is that MPEG-2 decoders cannot deal with pixel clocks 
above ~62 Mpixels per second. Enough for 1080@30i and 720@60P, but 
only half of what is needed for 1080@60P.

Today 1080i is typically de-interlaced after decoding and displayed 
either as 720@60P or 1080@60P.


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