Re: HDTV and latency

On Mon, 15 Aug 2005 15:12:58 -0400 Jim Gilliland <usemylastname@xxxxxxxxxxxx> wrote:
| octorok wrote:
|> I recently bought and returned a Samsung 56" DLP HDTV. I returned it
|> because of latency issues while playing videogames. I am now aware that
|> the latency was caused by the HDTV "upconverting" a 480i signal to it's
|> native resolution of 768p.
|>
|> I want to buy a 46" or bigger HDVT that can resolve 480i, 480p, and
|> 720p natively (without upconversion latency) but I don't know where to
|> look for this info, and the spec sheets offered by manufacturers aren't
|> helping.
|
| All LCD, DLP, and Plasma displays are of fixed resolution. Any signal
| that reaches them must be converted (up or down) to match the native
| resolution of the display. The conversion always takes a bit of time,
| but the delay is usually small enough to be unnoticeable.

If input is progressive and output is the same frame rate, conversion
can be done very fast. Otherwise for handling interlaced input, or
changing frame rate, there will be a delay needed to assemble enough
data. Shortest case would be one interlace field plus a few lines.
Longest would be a full frame plus a few lines in a good implementation.
That doesn't mean all implementations are good. It might be cheaper
to do it with a longer latency, which is of little or no consequence for
most broadcasts (as long as the audio matches).

480p in to 1080p out (what an advanced display may actually be doing
despite this not being an actual broadcast standard) would be a matter
of converting 4 lines in to 9 lines out, if the frame rates are exactly
the same, and you are willing to view a pillarbox or stretched display.

--
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| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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.

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