[opendtv] Re: Chroma Formats, P versus I, and Resolution Issues

  • From: Tom Barry <trbarry@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 15 Dec 2004 20:21:11 -0500

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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