[opendtv] Re: News: If There's a High-Definition TV in Your Future, Wait Till

At 4:45 PM -0400 8/28/07, Manfredi, Albert E wrote:

Craig Birkmaier wrote:


 Why use a de-interlacing display. Get a DVD player with
 progressive output.


Why do you assume that one method must be better than the other? There's
no guarantee that the DVD player can deinterlace better than the
display. If the interface from DVD to display is component video, which
can be either progressive or interlaced, then the final image quality
will not necessarily be better from a progressive DVD player output.
Because the DVD player has access to additional information that may help it making decisions regarding how to de-interlace specific scenes. When you connect a DVD player to a display via an analog component input ( or a digital input for that matter), the source has already been decoded by the DVD player. Any information in the transport stream is eliminated - the display can only decide how to de-interlace based on picture content. The DVD player can use information in the transport stream to guide the de-interlacing process. The main information of interest is the progressive flag, which is typically set for scenes that are progressive throughout. We tried to amend MPEG-2 to use additional fields to provide information about breaks in the 3:2 pull down sequence and to identify scenes that are interlaced, but the amendment was defeated because some companies said that using these reserved bits could break their players.
Now you can also buy upsampling DVD players with 1080 line outputs. The important point is that de-interlacing is a black art, and we can only expect a TV to do the minimal job required, This is why de-interlaced SDTV tends to look so crappy on most current displays. 


 > The main point i was trying to make by posting the article

 and comment is that the Average Consumer who buys an HD
 capable display will have little use for one of the HD
 disc formats.


I know that was your point, and has been for some time. My take on this
is that DVDs are "good enough," even though a screen of around 40" can
show improvement with better source material that regular DVD.
Yes DVDs are good enough for movies. There are applications - like sports - that can used the additional resolution in HDTV. This is also true for many non-broadcast applications like training point-of- sale and other forms of information display like in a museum.
Saying that we can show improvement over a movie on standard def DVD is not saying much. One could argue that a good NTSC signal might have more detail than many movies. Movies ARE NOT about resolution. 



The 10 Mb/s peak bandwidth of DVDs makes them about the same as ED, if
properly deinterlaced. So, "good enough," IMO, which doesn't mean it
couldn't be better.
The major problem with standard definition DVDs is that they must look decent on millions of old interlaced tube TVs. Any high levels of vertical detail can cause small area flicker on these interlaced sets. The compressionist must strike a balance between the needs of the interlaced audience and those with progressive displays that can handle more vertical detail. Typically this means filtering out some of the detail that causes flicker on interlaced sets. This could easily have been avoided by encoding all source for progressive displays at the maximum detail level possible, and adding a cheap convolution filer the to interlaced outputs of the player. But it was not avoided, so most SD DVDS are dumbed down for the lowest common denominator interlaced displays.
Obviously we could do even better by increasing the line count - aka 576P and the number of samples per line to achieve equal H &V resolution. A 1024 x 576P encoding is MUCH CLOSER to 720P than it is to its interlaced 704 x 576 line ancestors.
The peak bandwidth constraint at 10-11 Mbps is a limiting factor, but good progressive source will help, not make thing worse in terms of compression efficiency. H.264 could help too. 




 For what it is worth, I am happy to let the broadcasters
 waste their bandwidth on 720P. It is in the world of
 downloaded content that 480/576P will get a strong
 foothold. The 480 x 320 stuff on my iPhone looks
 outstanding.


That's neither here nor there. Low quality sound on a telephone or cell
phone does not mean that there's no reason to pursue high quality audio
in other appliances. Low quality video in cell phone or PC applications

does not mean that low quality video is all we should pursue either.
There is NOTHING low quality about the video on my iPhone. It is the appropriate level of resolution for a screen this size at the designed viewing distance of 12-30 inches. In fact it can easily be scaled up for my 720P TV display. I have done this and it still looks better than an upconverted NTSC source.
The point is not the pursuit of low OR high quality video. In an ideal world we would always pursue a level of image quality that is adequate for the application and the viewing requirements. I never see compression artifacts on video that is properly encoded for my iPhone. I always see compression artifacts in DTV programming, no matter if the source is SDTV, EDTV or HDTV.
Its all a matter of optimizing the entire chain that the source must travel though to the display. There is no one size fits all solution, as bandwidth is still the limiting factor, not our ability to encode high quality pictures. 

Regards
Craig


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