[mythtv-users] Hauppauge HD PVR (A bit more info for those starved for it)

Chris Ribe chrisribe at gmail.com
Fri Feb 29 19:40:04 UTC 2008

> > I look forward to the day when more broadcasters actually use higher
> > bitrates...  Here, only CW and NBC use such a high bitrate.
> >
> > Mike
> Doesn't CBS broadcast in 1080i too?  I thought only Fox and ABC used 720p?

Bitrate, not resolution.  For example, here at WCJB-TV in sunny Gainesville,
Florida, we use our 19.2 Mbits to broadcast 2 program streams.  One is ABC,
which is broadcast at 720p , and one is the CW, which is broadcast in a 480i

Before these signals leave the building, they are joined together in a muxer
- a fancy computer that takes one HD-SDI video signal, one SDI video signal,
and puts out a single SMPTE 310 signal, which is a fancy name for baseband
ATSC,  I believe.

Anyhow, the muxer tries to squeeze as much video quality into the 19.2 Mbits
as it can, and it dynamically reapportions bandwidth between the 2 program
streams.  When all is said and done, the CW usually ends up with about 5
Mbits and ABC gets about 12.5 Mbits.   I honestly do not know what happens
to the other 1,700,000 bits per second.

The end result is that the CW looks quite good, an ABC does not.  Our
neighbors at WUFT, the University of Florida PBS station, do things a little
differently.  They have 3 program streams, one which is usually 1080i and
two standard def.  The give their HD channel about 14 Mbit and squeeze their
SD channels into about 2 Mbit apiece.

The half-wits at WOGX (FOX out of Ocala)  use their  19.2 Mbits to broadcast
an HD and an SD version of the *same thing*.  I'm sure the many people stuck
with an SDTV and a digital tuner that doesn't downscale appreciate this.


TV/IT Engineer
WCJB-TV Gainesville, FL
(352) 416 0648
cribe at wcjb.com
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