[opendtv] Re: Check SAP on FOX during NASCAR Race
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 13 Jun 2007 13:01:11 -0400
----- Original Message -----
From: <dan.grimes@xxxxxxxx>
DG: I was able to do a couple of other tests which show that it is coming
from KVVU that way. I monitored the SAP off Cox Cable and Off Air and both
were the same and only SAP had the problem (main and mono were fine).
Other programming has the same issues, but not as bad as the NASCAR races.
HO: NASCAR race - Monday, June 4, 2007 12:45pm - 1:00pm
Same compliment of audio on all three services - Stereo, SAP, Monaural.
All have complete commentary, music and sound effects.
The SAP channel has about 6 db lower level, reduced frequency response
range and a clipped type tick, tick noise every few seconds which often
correlates with audio edges-say raised voice, etc.
JS: "Main" and "Mono" are one and the same. The main audio is mono, then
there is a separate L-R audio that is DBX compressed that is used to allow
the receiver to create stereo audio. There is a third carrier that is also
DBX compressed and bandwidth limited for the SAP channel, which is why it
usually sounds so lousy. There is also an optional fourth channel called
PRO which is even further bandwidth limited, intended for use as a studio to
field talent backchannel.
DG: Yes, but unfortunately I am always out of the house during the live
races. But with the rain delay at Dover, I was able to watch it live at
work off of Cox Cable and Off Air. So now I know it is a live problem and
not a VCR problem.
I did talk to the Chief Engineer at KVVU. He said it is a direct pass
through from the Fox satellite through Master Control to the transmitter.
He said he was going to check it in Master Control. I asked if he would
call me back to tell me what he found, but has not up to this point. But
can there be a direct pass through? Perhaps they are getting an ATSC
encoded feed, but wouldn't that need to be converted to NTSC for the analog
transmission? Or does the exciter get the same digital stream and spit out
two signals? I would think that the Master Control equipment would work
with SDI, perhaps with embedded audio, but would need to go to an ATSC
encoder before the exciter. But I don't have any experience with a Master
Control for an ATSC transmission, so I cannot speak to this.
JS: Any "direct pass through" has to go through a BTSC audio generator of
some sort. We use Orban Optimods, as does the majority of broadcasters who
broadcast BTSC (or MTS) stereo audio. The SAP channel of the Optimod has
level adjustments and compander settings that can easily cause the breathing
audio that you're experiencing.
John
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