[opendtv] Re: --FCC OKs WiFi between TV channels
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 29 May 2004 09:45:26 -0400
At 10:53 AM -0700 5/28/04, John Willkie wrote:
>Also, any paragraph that starts off with "The display is decoupled from the
>source..." is a paragraph that I won't read further. You see, you first
>have to explain why/how the coupling occured in the first place.
Why waste my time. You know exactly what i was talking about. With
analog TV the receiver scans the image as it is transmitted -
SYNCHRONOUSLY. No frame buffer or image scaling is required to
present the NTSC source on the display.
With DTV the receiver must process the transport stream, decode the
video using multiple frames of buffer in the decoder, and typically
another buffer in the display processor where image scaling takes
place to accommodate the source to the local display parameters. The
user may also have some control over the way in which the source is
accommodated to the display - full screen undistorted, full screen
with cropping and/or distortion, or letterbox.
>
>When I watch ER on a 4:3 set, how is the 16:9 content coupled to my set?
>(It ain't, the way you "think" about it.)
First, you are probably watching an NTSC broadcast of ER which is not
transmitted in 16:9. But let's assume you have a DTV receiver and are
watching an HD broadcast where the source is 16:9.
With the DTV receiver, the source is decoded producing an HD raster
in the display buffer. The receiver then creates various outputs
which can be connected to different display types.
An NTSC/S-video version - this could be 16:9 letterboxed into 4:3, a
simple crop of the side panels to fill the 4:3 screen 9possibly
guided by pan and scan metadata, or a geometric distortion of the
16:9 to fill the 4;3 screen, possible with mild cropping.
A 16:9 HD version for the analog component or DVI output - depending
on the receiver this may be 720P or 1080i ( a few can do either).
A 4:3 HD version with cropping and/or geometric distortion - not all
receivers offer this since most 4:3 HD sets have the ability to
determine how the 16:9 source will be accommodated.
>
>And, it appears to me, that an NTSC set attached to an ATSC STB is VIRTUALLY
>the same as a 4:3 "HDTV" set showing the same content. What would be the
>difference while watching ER? Does the NTSC set have lower effective
>resolution? (I'd tend to doubt it.)
Hardly. Assuming a versatile STB as described above, both the NTSC
display and the 4:3 HD display would be able to show either 16:9
letterbox or full screen with cropping and/or distortion. The NSTC
set would provide much lower resolution only 480 active interlaced
lines, of which only 360 would be used if showing the 16:9 letterbox
version. The 4:3 HD set would show at least 540 progressive lines, or
810 interlaced lines, or the full 1080 interlaced lines squeezed to
cover the 16:9 area of the screen.
No comparison at all.
Regards
Craig
>
>John Willkie
>
>-----Original Message-----
>From: opendtv-bounce@xxxxxxxxxxxxx
>[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Craig Birkmaier
>Sent: Friday, May 28, 2004 7:17 AM
>To: opendtv@xxxxxxxxxxxxx
>Subject: [opendtv] Re: --FCC OKs WiFi between TV channels
>
>
>At 7:49 PM -0700 5/27/04, John Willkie wrote:
>>I find it hard to believe that a 4:3 set actually is HDTV, since the only
>>HDTV table 3 formats are 16:9. What makes these sets qualify? Because
>they
>>can handle MP@HL video? Then, why not display HDTV content natively?
>>
>
>
>Too much Tequila John? You really are off the wall today.
>
>The display is decoupled from the source in Digital TV. All sets must
>accommodate all ATSC formats, as well as legacy 4:3 525 line sources.
>Thus by default, any screen (aspect ratio) will have some unused
>areas if the source is displayed accurately (some sets fill the
>screen by distorting or cropping the source. What's more, no
>lithographed display can display all formats natively, unless you
>want them to be presented in windows (i.e. 640 x 480, 854 x 480,
>1280 x 720 and 1920 x 1080); image scaling is a prerequisite for any
>ATSC conformant display.
>
>Let's say the display is based on a lithographed technology with 1280
>x 1024 samples (a common workstation format with a 1.25:1 aspect
>ratio). If you prefer, we could use a 1600 x 1200 panel that is 4:3.
>Now tell me that these displays are incapable of using a 1280 x 720
>subset to display HD properly...
>
>Regards
>Craig
>
>
>
>
>
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