[opendtv] Re: 1080i vrs 720P
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 02 Oct 2005 12:22:21 -0400
Craig Birkmaier wrote:
> We could easily have allowed only progressive formats. This would not
> have precluded 1920 x 1080 at 24P and 30P.
However they did include 1280x720p at 24, 30, and 60p. I don't think I
have ever seen any ATSC broadcast that seemed to have any more
resolution than 720p in any format. If that's the case then any
broadcaster that chooses can use 720p would not lose anything by it
except some extra royalties to MPEG-LA.
Meanwhile, 1080i does sometimes look better on my 1080i RPTV for some
reason and is probably okay as a legacy format, assuming it's okay to
use that word for our new HDTV system. AFAIK, the broadcasters using
1080i are happy with it.
If CRT driven lower priced 1080i RPTV's like mine gradually disappear
then we will probably also see a decline in 1080i as a delivery format.
Meanwhile better downsampling 720p cameras are supposed to be arriving.
So things may take care of themselves over time.
- Tom
> At 1:35 PM -0400 9/29/05, John Golitsis wrote:
>
>>On 29-Sep-05, at 1:13 PM, Craig Birkmaier wrote:
>>
>>
>>> This is the unfortunate reality of having an DTV standard
>>> that includes interlaced formats.
>>
>>Funny how you wanted a DTV standard that offered many different
>>emission signal configurations, but not one that offers many
>>different image configurations.
>
>
> It's not funny, because it is not true.
>
> The truth is that a properly designed digital image architecture can
> support true scalability for any compliant display. There is no need
> for formats, because ANY raster can be presented properly using the
> required scaling capabilities, needed when there is more than ONE
> possible raster size and/or aspect ratio.
>
> The problem comes when you add the additional complexity required to
> deal with interlaced formats. This requires not on image scaling
> capabilities, but sophisticated de-interlacing capabilities. Even
> standards converters that cost more than six figures cannot do a good
> job with de-interlacing, as it is impossible to properly predict the
> information that was not sampled in the first place. It's even worse
> when you have to rely on a $10-20 chip in the decoder/display to do
> the de-interlacing.
>
> The truth is that I and many others pushed very hard during the
> Advanced Television process to eliminate interlace from the digital
> televisions standard - both for SD and HD formats. This would have
> required that any interlaced source be de-interlaced, using the best
> professional equipment - before encoding for emission. It would have
> made it much easier to build display systems that use only
> progressive rasters, and with a cheap convolution filter, it would
> still have been possible to re-interlace the decoded source for
> presentation on legacy interlaced displays.
>
> But this did not happen. What happened is that interlace was
> entrenched in both SD and HD for many decades, and the MPEG-2
> standard was corrupted to deal with interlace...and sadly the same
> has happened with H.264. This was done to control the IP in MPEG-2
> and H.264, by updating old IP that was about to move into the public
> domain. Without interlace there would be little need for MPEG-LA, as
> all of the necessary IP is now in the public domain.
>
>
>
>>SA never had a box that only supported 1080i. The earlier models had
>>1080i output only, but had no trouble internally converting 720p.
>>Believe me 'cause I've had just about every single one of them, plus
>>a friend who was the VP of Technology at my cable company.
>
>
> Wrong. SA builds what the MSOs ask for. The first boxes that Cox
> ordered only supported 1080i.
>
>
>>> To the best of
>>> my knowledge, Cox now passes through the bits they get; and to the
>>> best of my knowledge the local CBS affiliate is using the entire
>>> transport stream for CBS HD broadcasts.
>>
>>"To the best of your knowledge" is a guess.
>
>
> I'll try to check into this. But I am virtually certain that I am correct.
>
>
>>> This is simply the
>>> reality of pushing 1080i beyond what is desirable given the
>>> application and the available bandwidth.
>>
>>Yet 1080i football looks better to my eye (primarily sharper), and
>>I'm hardly a sole voice in the wilderness here, either. Hockey too
>>has looked better to me in 1080i versus 720p.
>
>
> Probably because you have a 1080i display. Internal processing can
> have a major impact on image quality. And interlacing progressive
> source will cause a loss in quality.
>
>
>>But don't assume I'm pro-1080i or anti-720p as everything I do at
>>work is 720p, which was my choice.
>>
>
>
> We could easily have allowed only progressive formats. This would not
> have precluded 1920 x 1080 at 24P and 30P.
>
> Regards
> Craig
>
>
> ----------------------------------------------------------------------
> You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
> - Using the UNSUBSCRIBE command in your user configuration settings at
> FreeLists.org
>
> - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
> unsubscribe in the subject line.
>
>
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts: