[mythtv-users] HDTV on Myth -- is it a "myth?"
jcw at wilsonet.com
Tue Oct 12 19:01:48 UTC 2004
On Tuesday 12 October 2004 11:16, Anthony Vito wrote:
> > You don't need a high 80s signal to get a good recording though. My
> > *strongest* signals (I live about 20 miles outside Seattle) are in the
> > high 60s. All the high 60s recordings are perfect. A few of my stations
> > come in with signals in the low 50s, and while I get the occasional
> > failed recording due to lack of signal lock, when they do record, 99%
> > of the video is perfectly fine (every once in a blue moon, there's some
> > pixelization in the video stream where I presume the signal dropped a
> > bit).
> I wrote an entry in the pchdtv forum on signal strength and how the
> green and red lights on the back of the pcHDTV card relate.
Good stuff, I'll have to peek at my card a bit. Unfortunately, I have a
rooftop antenna that I have to manually adjust, so its a bit hard for me to
correlate antenna position w/lights without a LOT of up and down, but I'll
have to see what I can see...
> I live in Rochester NY. As of a few weeks ago when Fox came online
> all the local stations are broadcasting digitally. CBS is the only one
> left broadcasting in 480p. Not all the content is HD yet, some of it
> is upscaled, but it's getting better. The needed signal strength to
> not have errors in the stream varies widely among the channels for me.
> Fox "needs" the lowest signal only >50, non-coincidentally it's also
> the lowest channel(frequency) at 28... next up is CBS requiring >65 or
> so, at channel 45... ABC and NBC are 58 and 59.. I can't remember
> which is which... They both require >85 to be decoded correctly....
> So that driver is doing some crazyness... ( maybe just a simple
> normalization by frequency is needed? )
Interesting. Fox is the lowest channel here also (18), and works fine in Myth
when it can get a lock (i.e., when the signal is over 50 -- might even work
at lower thresholds if I set the threshold even lower manually in the db,
since the slider only goes down to 50). However, NBC is the highest channel
here (48), and also works fine at 50. ABC, CBS, WB and PBS all come in around
60-70, no problems with any of them.
Are you running a straight-up pcHDTV 1.3 driver, or are you using the 1.4ulmo
> The common indicator that tells me if I'm pulling in the channel no
> matter what station is the lights. If I see any red at all, even a
> blink here and there, that station is not going to come it. I believe
> that the red light is linked to the error-correction of the ATSC chip,
> if the error-correction fails, the red light gets a bit of juice.
I'm thinking maybe I can use this info to determine actual levels where my
problem channels (NBC and Fox) are actually non-viable... Maybe they're fine
even at 45, and I can safely mod my database for that minimum level...
> I think there are plans to get the LED status out of the driver.
> For now
> I might run some optical fiber to the coffee table so I have the ATSC
> decode status close at hand!
> Thanks for listening to me rank :) hope it helped.
Jarod C. Wilson, RHCE
jcw at wilsonet.com
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