[opendtv] Re: Europe now debates i vs p
- From: Doug McDonald <mcdonald@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 13 Sep 2004 10:32:58 -0500
Craig Birkmaier wrote:
> At 9:16 AM -0500 9/13/04, Doug McDonald wrote:
>
>>The signal above 25 MHZ is NOT aliasing. It is real signal.
>
>
> It may be real, however, it did not come from any commercial HD
> camera that may be in use today. Existing cameras typically begin to
> roll of the high end frequency response at about 20 MHz, and there is
> NOTHING left at 25MHz.
Are you sure that is true for 720p cameras? If is it, then there
is room for quite a bit ... a very lot indeed ... of additional
detail in 720p pictures.
>
>>I think it fair to say that the real signal has content to
>>30 MHz. And why should it not? These are the sharpest and
>>clearest pictures I have ever seen on a TV ... the static
>>logos and score blocks are extremely sharp on the screen.
>>Both ABC and Fox apparently take pride in having the sharpest HDTV
>>pictures around, and they most certainly do, at least on my TV.
>
>
> What you most likely are seeing at 25MHz is some form of compression
> artifact.
Actually, if I had not been careful to avoid it, it could
also have been real content from computer generated
stuff. The first day our local NBC station did HD, they
had a computer generated bug that had very high frequency
content indeed.
If indeed there is nothing real above 25 MHZ, then there is
no need for 720p horizontal resolution. For a couple of
weeks before yesterday Fox broadcast 720p football signals which
were camera generated at 720p, cut down to professional grade
digital, not MPEG, 480i, and then upconverted to 720p. Those
signals did indeed cut off at about 20-22 MHZ. And they looked
good ... real real good indeed ... but not the wow factor of the
real 720p.
If they are not getting any real signal above 25 MHz, they
need to get better cameras, considering the alias point is 37 MHZ.
Doug McDonald
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