[mythtv-users] Changing Physical Locations (zip code and cable provider)
beww at beww.org
Sun Dec 31 20:17:16 UTC 2006
On Dec 31, 2006, at 11:27 AM, mailing list wrote:
> Brian, I followed your instructions and everything seemed to work
> out on that front. Big thanks!
> Now here's the thing, At my old location I was on broadcast (rabbit
> ears) and recording and playback seemed fine. But at the new
> location using cable, Playback is choppy and seems to stutter every
> other second.
> Is there something different about processing cable input?? I
> didn't change any settings except for broadcast to cable somewhere
> and the refilling of the database.
Well RF is RF is RF..., but cable signals differ in a few ways:
The frequency assignments are different, and can be "standard", "HRC"
or "IRC". You seem to have that set correctly though.
The aural carriers on a cable system are run from 15-17 db. below the
visual ones, as opposed to 10db. down for a normal broadcast signal.
This is unlikely to cause the problem you describe, normally it
causes an increased tendency for buzzing in the audio, especially
with a lot of white or characters on the screen.
You will never have an upper adjacent channel from an off-air
antenna, unless you are between two markets. This is the reason for
the lower level of the cable aural carriers. This problem usually
results only in diagonal lines in the picture though.
Signal levels from a cable system tend to vary a lot more than
antenna signals. This is because the attenuation of coax cable varies
with temperature. This is especially true on the coasts where they
use black pvc-jacketed cable to prevent salt corrosion - sun shining
on black plastic gets a lot hotter than on bare aluminum.
So the mere fact you are using cable instead of the antenna shouldn't
really cause your problem, though it is possible that if the cable
signals are particularly noisy they might be causing larger mpeg
files. Noise compresses extremely poorly.
You are somewhat on the low end of the CPU requirements for SD (don't
even think about HD on that CPU), and the PCI video card is perhaps a
tad marginal as well.
But if it worked before it should work now. I would first make sure
you have as clean a signal as possible going into the card, then
perhaps try reducing the max bitrate a bit and see if that helps.
If your cable system is using so-called "baseband" converters the
output can be pretty non-standard. I am assuming that you are putting
the cable RF directly into the PVR card. BB converters are pretty
rare anymore, they cost too much :-)
Since you're running Mythdora you might post the problem on their
forum, if you haven't already.
More information about the mythtv-users