[opendtv] Re: 1080p @ 60 is Next?

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 14 May 2007 21:25:52 -0400

At 2:24 AM +0200 5/12/07, Olivier Houot wrote:
Mr. Hoffmann,

first i have to say i like the EBU demo principle, especially the way the sources have been elaborated. I just regret the big screen behaviour has not been given due attention. It should not be dismissed out of hand, but tested, and the results should be an input to the final decision .

I don't mean that the difference between SDTV and HDTV is invisible on a 50 inch screen, i say that HDTV is primarily about having a bigger picture. As often mentionned on this reflector, the initial target was a 30° viewing angle.

I completely agree that the design goal for HDTV was as you describe - BIG screen, WIDE viewing angle and a sharp picture.

But HDTV is just one of the potential applications for television. As we are learning these applications span the range from BELOW NTSC/PAL quality for mobile devices, to well beyond HDTV for special venues. In between there will continue to be a large number of displays that DO NOT deliver the HD viewing experience, despite the fact that they may offer HD resolutions - a 27-32 inch diagonal flat panel with 1-2 Mpixel native resolution can deliver the information, f you are sitting 30 inches away, but it will nominally be viewed at 5-7 picture heights.

And you have omitted a VERY IMPORTANT consideration in your analysis. The MAIN reason we need more pixels on the kinds of large screens you have described is to keep the viewer from seeing the raster and other artifacts at the designed viewing distance. I have a friend who has the same size Samsung DLP RPTV as mine, however he has the newer 1080P version, while I have the 720P version. The quality of the delivered images is nearly identical at this screen size. But there is a slightly improved overall experience due to the display oversampling relative to the nominal viewing distance.

When we deliver HIGH QUALITY samples to a display processor, it is relatively easy to resample the image to the native resolution of the display. We can downsample and deliver VERY GOOD images, and we can upsample, and deliver VERY GOOD images. There COULD BE some additional sharpness if the delivered source is 1080P versus 720P, however, you need more bandwidth to deliver this extra information. What the EBU tests demonstrated is that we need to tune the emission raster and encoding to best fit the bandwidth available to deliver the content.

Trying to cram more information through a pipe that cannot handle it will actually result in LOWER delivered image quality than a lower resolution raster that is properly encoded. The net result is that EVERYONE gets less image quality when the channel is stressed.

It's not about numbers. It 's about maintaining the quality of the samples through the emission chain.

Regards
Craig


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