[opendtv] Re: 625 video quality is good enough....
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 19 Oct 2004 10:53:43 -0400
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already outdated.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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