[opendtv] Re: Why Europe should choose 720P for HDTV

At 2:07 PM -0500 12/11/04, Tom Barry wrote:
>I'm not sure I'm able to provide any really convincing theoretical
>arguments, though I'll mention one thing.  See the paper on Craig's site
>on "An Increase of Vertical Resolution in Progressive Scanned Moving
>Images", at http://opendtv.org/Progressive.html .
>
>This paper talks about how our eyes can gather more detail from an image
>by tracking motion, considering multiple adjacent frames at a time.  I
>believe we can also do this for interlaced images.  So, either way, we
>pick up a bit more detail than the number of lines or pixels might suggest.

Yes, interlace does provide a workable compromise between spatial and 
temporal resolution...one that has served us well for more than a 
half-century. But it comes with a price...artefacts.

For ANY given raster, the images will be sharper from a progressive 
scan camera versus an interlaced camera. Where we get into trouble is 
trying to equate different formats with similar pixel clocks, such as 
720@60P versus 1080@60i.

Clearly, the 1080 line format has more spatial resolution along each 
line, but the vertical resolution is subjective. We.ve been through 
all of the arguments before; the general consensus is that an 
interlace factor of 0.60 should be applied, bringing down the 1080 to 
648, which is below the vertical resolution of 720P, but above 540, 
which is what is being sampled each field. This does indicate that 
the human visual system is integrating information between fields to 
provide the perception of improved vertical resolution. At least 
until an artefact comes along to spoil the illusion.

Bottom line. There is no reasonable justification for the continued 
used of spatio/temporal undersampling for digital television.

Regards
Craig
 
 
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