[opendtv] Re: 4k @ 60 fps encoded into 15 Mbps using HEVC
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 23 Oct 2012 19:59:55 -0400
Perceived life of 1080i acquisition and production gear?
I think you give too little weight to a network's or local affiliate's
physical plant. Servers don't output ASI streams, they output uncompressed
video. Production switchers, cameras, video and solid state recorders,
monitors, routers, and existing in-house cabling are all geared towards the
uncompressed HD-SDI digital video as their interconnection format.
Can 4K pass through a plant built around HD-SDI? Can 1080p60? 1080i30 (in
the traditional sense of 30 frames per second, 60 fields per second) is the
top end of HD-SDI. 1080p60 requires dual link HD-SDI, which is vary rare in
actual production equipment, and doubles the cabling, patch field, and
router cross point requirements. 1080p30 does fit within a single HD-SDI
link, but it doesn't have the temporal resolution for fast motion sports.
1080i30 (with it's 60 fields per second) does. So does 720p60, the "other
white meat" of present HD formats.
We came across this bottleneck called "everything prior to the emission
encoder" when we had the naive notion to try to downconvert HD material to
480p60 wide screen for secondary channels. Turns out that 480p60 is too
high of a bitrate for SD-SDI, and no HD-SDI products would support such a
low bitrate. The best that could be done was to encode 480p60 as 720p60
with either a black picture frame or black right side and bottom, but then
no ATSC encoder could intelligently take only the active video portion and
encode it to 480p60WS. So even though 480p60 is a valid ATSC format, there
is no practical way to use it.
So it is much more complicated to switch to another video format than just
changing a couple of pieces "acquisition and production gear."
There is nothing wrong with keeping 1080i30 in a future format, and let it
die a natural death (on the equipment owner's timeline) much as 480i has in
most facilities.
John
----- Original Message -----
From: "Craig Birkmaier" <craig@xxxxxxxxx>
My best guess is that CBS. Sony et al, are trying to get interlace
into h.265 for two reasons:
2. To protect and extend the perceived life of 1080i acquisition and
production gear.
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