[mythtv-users] Capture card with best tuner - BT8x8, SA713x or PVR-250?

Joe V joevph at yahoo.com
Sat Aug 23 03:54:41 EDT 2003


Richard,

Now that I've dropped the capture resolution down to
352x480, the pauses (when one actually happens) are
only a couple of seconds long (not as bad as before). 
They are, however, still happening, and there is
clearly frameloss (the best way to see this is to
watch  ESPN or CNN or MSNBC, where they have the
ticker at the bottom - it's very choppy).

The hard drive has DMA enabled on it (Red Hat 9 does
this by default).  If I run hdparm and do the quick
tests, I get good numbers (in the first test 300+
MB/sec in most cases).  Also, hdparm reports that I'm
using udma5.

The options, "Automatically Flag Commercials" and,
"Strict Commercial Detection" are enabled, but
"Automatically Skip Commercials" is not checked.

Currently, my setup (in terms of splitters) is as
such:
- Splitter on the wire that enters my apartment - this
was installed by the cable company so that I had one
line for my TV, one line for my cable modem.
- The TV line has a splitter on it (three way) with
two of the cables connected (Myth box and TV, I
planned on the third one being a second tuner for the
Myth box).  Instead of a splitter, I tried putting in
an amplifier, but it just made the signal worse.  The
splitter actually seems to help out a bit.

The only interference I can think of is that the PC is
next to the TV, and has it's side panels off.  That's
because it's a temporary case, and I don't have proper
cooling in it.

The signal is very bad even coming off the main wire. 
I took some still shots (which show the diagonal lines
on one channel and the noise on another), and I also
captures a quick video clip (three seconds) with the
same camera that shows the diagonal lines also.

Anybody who wants to look at the images can go to
http://www.vulturesnest.net/catv.html.  I have enough
of a transfer cap that plenty of people can look at
them.  Feel free to check out the rest of the site
too.  :)

-- Joe

--- Richard Lee-Morlang <rick at webtownis.bc.ca> wrote:
> On Fri, 2003-08-22 at 22:33, Joe V wrote:
> 
> > My setup is an Athlon XP 2400+, 512MB of DDR RAM,
> and
> > a Western Digital 100GB hard drive.  Clearly, this
> > should be good enough for "Live TV".
> 
> 
> Absolutely. I'm fairly confident I could throw
> another capture card in
> my box, and be able to record two signals while
> watching something else
> without any difficulty. 
> 
> 
> > Given that setup, I'm not too keen on having any
> > noticable disruptions in the picture.  By
> noticable, I
> > mean, the picture pauses for 2-5 seconds, with no
> > sound.
> 
> 
> Wow. I have trouble imagining a cable signal so bad
> that it would cause
> those sorts of problems on your hardware. Is there
> any chance your
> recordings directory isn't on a DMA-enabled drive?
> Or do you happen to
> have automatic commercial skipping turned on? 
> 
> Maybe you should stick a still image of a typical
> "marginal" picture up
> somewhere. I've got a few channels that often look
> like every show was
> filmed in a mild blizzard, and none of them are so
> bad as to cause those
> sorts of problems.
> 
> 
> > using the v4l2 drivers and bttv 0.9.x as well as
> the
> > default bttv in Red Hat 9, and the latest bttv
> 0.7.x.
> 
> 
> I'm running Redhat 9's default driver, I believe,
> which appears to be
> 0.7.96.
> 
> 
> > I guess I'll have to hope that the management will
> fix
> > the signal, and in the meantime, play around with
> it
> > further.  Although my goal is to have everything
> in
> > one box, I wonder if using a dedicated backend
> would
> > help out.
> 
> 
> Any chance that there's any local equipment that is
> interfering? When I
> first setup myth, I noticed the picture was
> significantly worse than
> with my TV or VCR tuners. After some experimentation
> I noticed that the
> splitter I was using degraded the signal a bit (I'm
> assuming it was too
> close to the computer and was picking up a lot of
> the EM noise), the
> signal amplifier was adding even more noise (maybe
> for the same
> reasons), and the hub I'd added was the worst
> contributor of all. 
> 
> Rick
> 
> > _______________________________________________
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> mythtv-users at mythtv.org
>
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> 


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