Re: How does digital TV broadcast prevent ghosting effects?

MRW wrote:

Good morning world!

I've been reading about the new digital TV standards (8-VSB, DVB-T,
ISDB-T) and they all mention that the standards are more robust
compared to the analog standard. For example, all state that
practically ghosting effects are eliminated with DVB-T and ISDB-T
providing more robust response to mulitpath effects than 8-VSB.

How do these standards eliminate ghosting effects?

I also read a similar scheme for analog TV using Ghost Canceling
Reference (GCR) signals from both transmitter and receiver. Is this
pretty much the same idea?

Thanks!

With analog video signals, ghosting is caused by mutipath distortion,
where a 'second copy' of the signal arrives at the receiver delayed by a
small amount of time. That second copy is displayed as a second image,
offset on the screen by a distance equal to the path delay times the
horizontal scanning rate of the CRT.

With digital video, the broadcast is sent in several types of frames.
Each frame is labeled with a sequence number indicating where in time it
should be displayed. While mutipath distortion can still interfere with
digital signal reception, it does not manifest itself as a second image
offset on the screen spatially from the original. The only way to
produce a ghost in a digital stream would be to spoof the packet timing
data.

--
Paul Hovnanian mailto:Paul@xxxxxxxxxxxxx
------------------------------------------------------------------
668: The Neighbor of the Beast
.

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