Archived from groups: alt.video.digital-tv (
More info?)
In article <c6u9cp$rer$1$8300dec7@news.demon.co.uk>,
"Stephen Neal" <stephen.neal@nospam.please.as-directed.com> writes:
> John S. Dyson wrote:
>> In article <c6s30i$e1e$1$8302bc10@news.demon.co.uk>,
>> "Stephen Neal" <stephen.neal@nospam.please.as-directed.com> writes:
>>>
>>> I am approaching this as a 50Hz viewer watching material converted
>>> from 60Hz - so we are throwing away temporal information rather than
>>> making it up though - so we probably benefit in that way, though
>>> when 576/50 stuff is converted to 480/60 you have the benefit of
>>> sharper source material?
>>>
>> Well -- NTSC has the same horizontal detail, and high end NTSC
>> cameras have had double the number of vertical pixels (giving a
>> wider/flatter vertical response than expected.)
>
> These cameras are available in 576/50i - they are widely used in Europe. I
> would expect they are also available in 480/60i models as well.
>
Even my ENG style double pixel camera (of the 1995 vintage) can max out
anything that the SDTV standard needs.
>> camera designs is probably a similar order of magnitude.
>>
>> (My own camera has 960+Vertical pixels, which are DSPed
>> down to 480 with more detail in combo with the necessary
>> interline flicker reduction than is commonly assumed from
>> people used to 480V (or 576V) pixels.)
>
> Yep - you are making a specific camera comparison though - not a general
>
Remember: my camera isn't an example of the epitome of perfection... It is
just that with full decoders, still essentially impossible with composite
PAL, then NTSC can capture alot more detail than PALites might guess.
(Pal decoding is problematical because of the phase cycle being twice
as long, with slower frame rates, which makes complicated motion compensation on
a PAL 3D comb both problematical and required.) This problem of full
PAL decoding isn't just related to the 50Hz issue (which isn't the hardest
part of the problem), but because of the long term digital filtering needed
to comb out the artifacts (well, not technically quite true, but the idea
is correct.)
>
>>
>> Given composite encoding, that tends to limit the available
>> vertical resolution without interfering with the chroma. Composite
>> encoding is mostly legacy (or commercials) at the studio level
>> nowadays.
>
> Composite is all but dead surely - only old regional stations and the final
> stage of the analogue broadcast chain is now PAL in the UK. (Certainly all
> UK commercials are delivered in 16:9 component - with only very occasional
> composite issues)
>
Much of the historical complaining about NTSC from PAL land has been in the
timeframe of composite still being king. NTSC has been consumer-land
3D decodable for approx 10yrs now, which mitigates most problems with
the 3.58MHz subcarrier. (That choice is necessary because of the thrifty
6MHz channel witdth in the US.) Comparing video (even on late 1990's
pro monitors) sometimes utilizes old fashioned line combs, and doesn't
really decode the video as well as the consumer can see it.
Even given the nice, wide channel widths, the effective chroma resolution
(both H and V) of video that is encoded with PAL is disappointing
considering the fat sidebands on the chroma subcarrier. Almost all
practical decoding schemes effectively require significant spatial averaging,
sometimes mitigated with some dynamic filter coefficients. The same
thing is sort of true for NTSC als, but the 3D filtering can seriously
help the small detail (including for chroma), while also the NTSC chroma detail
is intrinsically twice as great in the vertical direction.
BY spending lots of spectrum space, the PAL signal (esp UK) can provide
lots of luma detail (even if interfered with by chroma and vice versa.)
The advantage of the complex PAL encoding is greatly decreased with the
introduction of stable electronics... Production still needs to do
proper set-up for color, no matter the encoding -- so claiming that NTSC
is much more of a burden is 'interesting'. Perhaps old equipment that
drifts several degrees between usage might add some burden, right?
🙂.
>
> Digital TV in both the US and UK mainly uses 4:2:0 sampling for MPEG2 -
> chroma resolution subsampled vertically to match the horizontal
> sub-sampling? This is the same in both line standards - though DVCam is
> different I think (4:1:1 in 480/60, 4:2:0 in 576/50)?
>
DVCPRO is more serious format in the US (actually generally superior to DVCam
for pro use.) Metal evaporated tape can be workable, but not really
the best choice. DVCPRO is Metal particle, and uses 4:1:1 in PAL
countries -- it is supposedly better
for generation loss. 4:2:0 tends to be more common for distribution formats.
My own home gear is actually mostly 4:2:2, and I cannot see why a pro
would even bother with 4:2:0 or 4:1:1 for production, other than for
low end work. The supposedly more 'edit friendly' 4:1:1 isn't a good
match for 4:2:0, and supposedly 4:2:0 in production has its own set of
disadvantages.
>
> Not sure what point you were trying to make there?
>
The biggest point: NTSC derived formats dont' have vastly
inferior spatial resolution WRT PAL formats (essentially the same,
for the baseband composite schemes because of the better decodability
of NTSC.) The only real advantage of PAL in the real world is the generous
bandwidth for the OTA transmissions. The serious (and deadly) disadvantage
of PAL (again, given the timeframe of historical complaints) has been
the unfortunate 50Hz flicker... Yes, your brain can learn to filter it out,
but NATURALLY, the HVS is more sensitive at 50Hz flicker by AFAIR
2orders of magnitude. That probably helps to confound perception to avoid
seeing defects in video. My guess is that one reason why 100Hz TVs
have been criticized is that people are actually seeing the picture
now!!!
John
You may want to question why they've gone
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