[opendtv] Chroma Formats and Why Europe should choose 720P for HDTV
- From: Terry Harvey <tjharvey@xxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 15 Dec 2004 22:06:53 -0700
Tom,
4:4:4? I would be surprised if you could see the difference between 4:4:4
and 4:2:2: I can't.
I can see the difference between 4:2:0 and 4:2:2 only because of an
interlaced raster. On a High Definition display I doubt if you could see
it. (Especially with the current 'state-of-the-art consumer displays).
No one mentions the recording issues: with limited luma/ chroma resolution
formats such as HDCam and DV100, there is a lot less than 1920 pixels per line.
I think the merits of 720p50 outweighs any consideration of an interlaced
standard. 720p (50 or 60) provides the best balance between temporal and
spatial resolution. And it is relatively sane as far as bandwidth is concerned.
24p should be only relegated to Hollywood where the producers there like
and are accustomed to film judder. (I know, I know... 24p is to facilitate
program production for Europe and America etc etc.)
1080p is nice but the bandwidth requirements are crazy for everyday broadcast.
I will concede that 480i to 720p on Fox looks awful. But how about 720p
capture resizing to 480p for transmission and resize to 720p for display?
This would produce a nice display, save bandwidth and would keep both the
bean counters and the engineers relatively happy: it isn't a perfect world!
Imagine with WM10... seven HD like program streams per ATSC OTA multiplex!
Terry Harvey
At 08:21 PM 12/15/2004 -0500, Tom Barry wrote:
>My own experiments in just playing around a bit suggest you can upscale
>most anything to about 50% large in either dimension and probably get
>away with it.
>
>I also believe the very commonly held belief that the eye is less
>sensitive to chroma and therefore a little chroma sub sampling can also
>be gotten away with most of the time.
>
>The problem is those two beliefs above somewhat clash when you start
>upscaling 4:2:0 to larger sizes, say DVD to 1080p, sitting up close.
>The chroma is just a bit too sparse and it starts to look a bit washed
>out on larger displays. 4:2:2 might be enough (and is probably
>necessary for interlace) but Craig and I were talking about HD DVDs and
>4:4:4 seemed it would certainly do the trick without any sidebars for
>caveats.
>
>- Tom
>
>PS - anybody know of any of the popular free codecs that would allow me
>to encode in 4:2:2?
>
>Tom McMahon wrote:
>
> > I am not necessarily disagreeing with anyone here but let me just say that:
> >
> > * The primary reasons we just added the 4:4:4 Profile to the H.264/AVC
> FRExt Amendment were 1) To support non-YCbCr color spaces
> > (like RGB, SMPTE XYZ' or multispectral imagery) where chroma
> subsampling simply makes no sense and 2) to support the post industry
> > where you are doing many generations of postprocessing and can't afford
> all the chroma up/downconversion each time. (Yes, there is
> > going to be I-frame and other forms of compression in post.)
> >
> > * The primary justification for including the new H.264/AVC 4:2:2
> Profile was for interlaced applications.
> >
> > * After spending a few years looking at the highest possible quality
> progressive D-Cinema imagery on the biggest screens with the
> > best (2K black chip) projectors going thru both 4:2:0 and 4:4:4 codecs,
> I see no reason not to use 4:2:0 chroma format for
> > compression (so long as the imagery is progressive).
> >
> > -----Original Message-----
> > From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx] On Behalf Of Tom Barry
> > Sent: Wednesday, December 15, 2004 2:00 PM
> > To: opendtv@xxxxxxxxxxxxx
> > Subject: [opendtv] Re: Why Europe should choose 720P for HDTV
> >
> > As that's two posts correcting me now I guess I better clarify my
> sloppiness. The "it" that I was claiming we couldn't currently see
> > was the full glory of 4:4:4 1080p and not referring to seeing the
> difference between the lower resolutions bandied about.
> >
> > - Tom
> >
> > John Shutt wrote:
> >
> >
> >>3 out of 4 programs on PBS's HD schedule are actually widescreen SD
> >>upconverted to 1080i. The difference is very noticeable.
> >>
> >>John Shutt
> >>
> >>----- Original Message -----
> >>From: "Doug McDonald" <mcdonald@xxxxxxxxxxxx>
> >>
> >>>>Just because we couldn't see it on almost all current displays (1080i
> >>>>or
> >>>> 720p fixed) doesn't mean we shouldn't do it.
> >>>>
> >>>
> >>>That last is false ... it CAN be easily seen, and noticed, as it is
> >>>actually AVAILABLE TODAY, almost every day. It is visible on Fox OTA
> >>>TV. It is clearly inferior to true HD 720p.
> >>
> >>
> >>
> >
> >
> >
> >
> >
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