[opendtv] Re: 625 video quality is good enough....

At 12:25 PM -0700 10/18/04, Dale Kelly wrote:
>I agree, 50/60P should be the ultimate format when technology can
>accommodate. However, I don't know that it can be done in a transport
>constrained to MPEG2.

Don't confuse the transport and the method of video encoding. MPEG-2 
TS could care less about the content of the packets. The standard has 
already been updated to transport MPEG-4 content.

And don't get hung up on  the bandwidth needed to deal with 50/60P 
display refresh at higher pixel counts. Compression works more 
efficiently as image entropy is reduced. The real enemy of 1080@60P 
is not bandwidth - it's still expensive to deal with 150 msamples 
/sec, but it is clearly possible (e.g an Apple Cinema display).

The real enemy of 1080@60P is noise. We cannot saturate the spectra 
of a 1920 x 1080 raster even at 24P today. HD cameras produce no 
useful information above 22-24 MHz. If we push the sampling rate 
higher, we capture significantly more noise and very little 
additional image detail. This is a compression killer.

The reality is that the MPEG-2 encoding tools don't care. 1280 x 720 
@50P is fully supported by MPEG-2, as is 1080@50i. The limitation on 
MPEG-2 is the 62,668,800 samples per second clock. There is no good 
reason to EVER update MPEG-2 for 1080@50/60P. The encoding tools are 
already outdated.  MPEG-4 part 10 (AVC) offers superior encoding 
tools and a far better path to the compression of 2Mpixel (and 
beyond) progressive formats.

But let's not lose sight of the real objective. Acquisition and 
display are decoupled in our new digital world. There may well be 
good reasons to acquire 2 MPixel rasters (and beyond) for archival 
and post production purpose. But this DOES NOT mean that we need to 
use 2 Mpixel emission formats when 1 Mpixel displays are more than 
adequate for virtually EVERY consumer display application. We need to 
deliver high quality samples, not compression artifacts.

>
>I had forgotten about the advantage 50Hz countries have in the film world.
>The "pull down" conversion is one the more valued features of my DTV set.


As we move to displays that present entire frames this issue too will 
go away. DLP, LCD and plasma display can present 24P without any 
pulldown.

It seems that we should be promoting a path to real convergence in 
international video standards, rather than trying to sustain 
geographic differences designed to protect existing markets.

Regards
Craig
 
 
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