[opendtv] Re: News: CEA FORECASTS CONSUMER ELECTRONICS REVENUE
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sat, 13 Jan 2007 10:20:24 -0800
Craig wrote:
> Try a more realistic raster that better reflects the frequency
> response of NTSC. 480 x 480 interlaced is about right.
>
> >And the video bandwidth is 4.2 MHz.
The actual video bandwidth of composite NTSC is less that 3.5 MHz given the
bandpass filtering that allows for insertion of the 3.58 color subcarrier.
> The reason why 704 (13.5 MHz sampling) is overkill for NTSC.
Component digital NTSC video, as used universally in production and in
studio/station distribution is 4.2 MHz. It is originated by cameras and
computer imagers that over sample, which is important when producing the
final 4.2 MHz image. Digitizing it components at 13.5 MHZ makes for a better
final product regardless of final distribution, but particularly in DVDs.
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Craig Birkmaier
> Sent: Saturday, January 13, 2007 9:04 AM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: News: CEA FORECASTS CONSUMER ELECTRONICS REVENUE
>
>
> At 11:14 PM -0500 1/12/07, Albert Manfredi wrote:
> >First of all, I assume the 704 X 480 analog SD occupying 6 MHz more
> >or less represents NTSC. So in fact, it is 704 X 480 at 60i. And for
> >good, clear reception, in the 6 MHz channel, you need about 40 dB of
> >C/N. Less than that and the image quality suffers very rapidly,
> >compared with an SD 480i.
>
> Try a more realistic raster that better reflects the frequency
> response of NTSC. 480 x 480 interlaced is about right.
>
> >And the video bandwidth is 4.2 MHz.
>
> The reason why 704 (13.5 MHz sampling) is overkill for NTSC.
>
> >
> >Compare that to 1920 X 1080 at 30p or 60i. The video bandwidth now
> >is 31 MHz, and all you need to decode this essentially error free in
> >a 6 MHz channel is 15 dB of C/N, give or take a few fractions of a
> >dB. And this is very predictable, from what my STB's signal monitor
> >tells me.
>
> Rubbish. Take a look at a spectrum analyzer of ANY MPEG-2 encoded HD
> source with a bit rate of say 17Mbps (about the max video payload for
> ATSC). The only stuff you will see above 20 MHz is the noise from
> quantization errors. Black to white pixel transitions can throw some
> nasty high frequency spikes - these "details" were not in the source,
> they are artifacts of compression. The C/N of the channel is
> completely irrelevant to this discussion - the frequency response is
> no longer a function of an analog channel, it is a function of the
> digital encoder.
>
> Regards
> Craig
>
>
>
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