[mythtv-users] Fast CPU, DMA enabled on HD, Xv enabled, still getting pauses in Live TV

[Joe V]

Vince,

Thanks for the tip.  I know somebody who works for a
cable modem company (I used to work for the same
company), and he might have access to a signal booster
that I can test with.  I have my main cable line
coming in, then split two ways (one for the TV, one
for the cable modem), and then the cable modem line is
split three ways (with a 7/7/3.5 dBmV) splitter.  The
cable modem goes on the 3.5dBmV line (to keep a
cleaner signal), and the MythTV machine is on one of
the 7dBmV lines.  The two-way splitter is a
3.5/3.5dBmV splitter.  The idea then is to split the
TV line again, so that I can have three cables - one
for the TV, and two for the MythTV box (one right now,
and another one once I put in another encoder, which
will probably be a PVR-250 once the driver stabilizes
a bit).

Yeah, I used to work for a cable modem company, but
I'm a programmer, I'm not really familiar with the
signal tech, maybe somebody can enlighten me here.  :)
 However, I'm guessing that the 7dBmV lines are higher
noise.

Now then, I re-installed Red Hat this afternoon, and
rebuilt MythTV, no special optimizations.  I reduced
the capture size to 352x480 (RTJPEG, default settings,
no audio compression) and at the beginning had a bunch
of dropped frames ("rebuffering..."), and then
finally, "IOBOUND - blocking in
ThreadFileWriter::Write()" (first time I've seen
this).  DMA (UDMA5 to be precise) is enabled, didn't
have to tweak any settings.

In the hour and fifteen minutes (or so) since seeing
that message on the console, I have only seen the
"rebuffering" message once.  I'll admit, I'm not
watching and listening to the image right now (it's on
a monitor, the interlacing is killing me), so it could
be skipping, but, I'm more concerned about the
messages.  If I can get rid of the messages, then I'll
watch it (and get a scan converter to hook it up to
the TV).

I'm thinking that perhaps with some of the default
services Red Hat has enabled (i.e. anacron) might
cause a flurry of disk activity in the beginning, but
then things settle down.  It is my plan to disable
these services.

I'm slightly disappointed that I can't capture at at
least 480x480, but if it's a problem with the signal,
that would explain things.  The image looks good on a
TV, but then again, a TV doesn't have to deal with
capturing frame by frame, buffering, processing, and
then displaying (at least not to the same extent that
MythTV does).

Progress is good.  :)

-- Joe

--- Vince Busam <vince at busam.com> wrote:
> Not sure this will help but...
> 
> I have a Athlon 1800+ and get good recording on most
> of my channels (using an
> old fashion antenna).  On channel 2 and sometimes 4
> and 5 the recording
> stutters.  When this happens there is sometimes no
> sound.  While these channels
> are fine on my regular TV, they look weak when
> played through my tuner card.
> 
> My guess is that the weak signal is causing the
> video capture card's tuner
> problems.  Don't know if this is a good guess but,
> if I'm right, maybe this
> could be your problem too - either a weak signal or
> bad tuner card.  I have two
> tuner cards (PVR 250 and AverTV) and am still
> getting the system up and working,
> so I'm not sure which card (or both) are giving me
> problems.
> 
> I think my weak signal problem is that I'm splitting
> the signal into seven
> outputs without any amplification and I'm in a
> fringe area to start with.  But I
> do have a big antenna.
> 
> Vince
> 
> 
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> mythtv-users at mythtv.org
>
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