[opendtv] Re: 1080p@60 for MPEG-2
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 13 Nov 2007 07:19:32 -0500
At 2:00 PM -0500 11/12/07, Tom Barry wrote:
As much as I am attracted to the idea of 1080p/60 due to the shear
numbers I don't really think it makes much sense for broadcast,
cable, or satellite in the next decade or so, even with AVC. It's
already been shown those distributors all are willing to compromise
HD picture quality to save bandwidth and ad more channels.
Yup. And the trend here is toward H.264, especially for HD due to the
improved efficiency - both DBS systems in the U.S. are moving in this
direction, and it may not take long for the cable industry to follow
for competitive reasons. And frankly, the cost differential for
adding H.264 decoding is not that great.
I do seriously want faster frame rates but for the moment would be
perfectly happy to instead have a higher quality 720p/60 delivery
scaled up to 1080p or higher by the display.
This is where the real action will take place. 720P just makes good
sense for emission, both in terms of the quality delivered at
economically feasible bit rates, and because it is easy to scale up
720P for 1080P displays.
Where 1080p/60 encoding might make sense in in newer video disc
technologies where they will easily have the available space. Sadly
however there is no compatible way either HD DVD or Blu-Ray can
support this under the current specs.
One thing that amazes me is the lack of high frame rate content
distributed on DVD. It has really become a movie distribution medium
for most folks. This may have something to do with the fact that SD
DVD using 720 x 480/576 at 50i/60i can look pretty crappy by the time
the source is de-interlaced and processed for display on any of the
progressive display technologies. IT may also have to do with the
fact that most of the high frame rate content on TV today is sports,
which is typically consumed live - only the season highlights
typically make it to DVD.
I'd expect the next generation of highdef discs (some new standard)
to embrace both higher frame rates and bit depths. For this cycle
it is just not going to happen but eventually folks will start
making libraries of media this good to (re)release on future media.
This is already possible. In fact, you can put high quality stuff on
red laser disc - the only issue is program length and the need for a
software HDTV decoder.
I don't think it will be too long before the declining storage cost
of electronic media makes it cheap to electronically 'film',
process, and store at, say, 72 FPS and then release 24 FPS movies
but archive for the future faster frame rate higher definition sales.
I'd love to see more high frame rate production, but this does not
seem to be happening. What is happening is the ability to create the
missing frames to create 72P or 120P streams for display. Sony's top
of the line Bravia's operate with a 120 fps clock and create the
in-between frames for display. And Jeroen will be quick to add that
Phillips is offering frame prediction capabilities in some of its new
displays.
Bottom line, there is a great deal that can be done to improve the
display of of source material locally using display oversampling and
frame prediction techniques. The key to making this work is the
delivery of high quality samples to the receiver. This is why it
makes more sense to resample to lower resolutions for emission, so
that the delivered quality can be maintained. Even if we could get
1080@60P through the ATSC emission channel, the quality would be
compromised during peak bit rate scenes. The expected scenario would
be that some networks would get on the 1080@60P bandwagon, but in
loop low-pass filters would reduce the level of resolution on the fly
to prevent the creation of serious compression artifacts. Which begs
the question...
Why bother?
Regards
Craig
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