[mythtv-users] dumb hdtv questions

[Cory Papenfuss]

>> 	Just from a raw pixel rate you've got this:
>>
>> Signal	Resolution	Pixels			Relative pixelrate
>> NTSC:	720x480 at 30Hz	= 0.345Mpixel at 30Hz	= 1:1 (480i)
>
> Actually, as I understand it, broadcast NTSC can be more accurately
> presented at around 352x480, perhaps 480x480 at most.   SDTV (which
> would describe what you get from an interlaced DVD or a digital SDTV
> broadcast) is as much as 720x480i.
>
 	You are pretty much correct... I just said NTSC as opposed to PAL 
DVD.  NTSC spec is an *analog* spec, which is rather subtle to describe in 
terms of a digital resolution... thus the reams of disinformation and 
misunderstanding.  Broadcast NTSC has 6MHz channels, but due to the VSB 
modulation frequency folding, 4.2MHz is allocated for video.  At 80 
"lines" per MHz, that's 448 4:3 horizontal dots.  With a 0.7 Kell factor, 
that amounts to 640x480 maximum "perceived" resolution.  DVD is a little 
better than that at 720x480.  The OP was talking about MPEG2 though... 
so DVD resolution is a valid comparison.

>> 480p:	720x480 at 60Hz	= 0.345Mpixel at 60Hz	= 2:1
> Known as EDTV though in theory that's any progressive frame rate.  This one
> confuses me a bit.   Films are shot at 24fps, so therefore doing them at
> 60fps interlaced (30 full frames/second) contains as much information as
> doing them at 30fps or 24fps progressive.  With the right decoders should
> be able to lok th same.
>
 	Yes... do a little reading on 'telecining'.

-Cory

*************************************************************************
* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *
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