[mythtv-users] System Spec Survey

Rolando J. Nieves rjnieves at earthlink.net
Sat Jan 17 11:08:05 EST 2004

Thanks to everybody that replied. I would like to use the Pinnacle and take
advantage of the hardware encoding of the card but since it generates too
much data (between 60-120K per frame) and my hard drives seem to be
throttling the system (profiling revealed communication between backend and
frontend seems to top out at 2.5MB/s*), I'll have to use another capture
card. Hopefully the PVR-250 I ordered recently helps in the data flow area
(6000Kbit/s for DVD-quality video should be less than 1MB/s between backend
and frontend).

Again, thanks for all the replies.


* With the frontend "RemoteFile" class receiving 64k blocks of data from the
back end in about 25ms. Most of the delay was caused by the backend reading
the data off disk. Maybe I should hack Myth a bit and amortize the read time
per 64k block using bigger block reads? hmmm...
-----Original Message-----
From: David jeske [mailto:jeske at chat.net]
Sent: Friday, January 16, 2004 2:00 PM
To: Rolando Nieves; Discussion about mythtv
Cc: mythtv-users at mythtv.org
Subject: Re: [mythtv-users] System Spec Survey

-- Rolando Nieves wrote:
> Ok, so my last message was a bit winded ... I'll get to the point
> this one. If you have successfully fielded a MythTV box using
> an MJPEG card or a framegrabber and encoding to RTJPEG in MythTV,
> you're satisfied with the results, I would definitely appreciate a
> short description of the hardware you used to build the Myth box.
> CPU, Mobo, and HD should be enough. I'm just trying to determine
> kind of a system I need to field a MythTV box using the Pinnacle
> DC10+ card without "prebuffering pause"s every 5 seconds.

I'm running on a P4-2.4ghz, 512MB. My initial setup was with an ATI
TV Wonder VE. Initially my setup would pause every 2-3 minutes. I was
using RTJpeg and the CPU was always 80% idle. I simply increased the
process priority of the mythfrontend and the problem went away.

nice -10 mythfrontend

Now I'm running a PVR-250 alongside the ATI TV Wonder, and I'm about
65% idle using rtjpeg while doing two records and one playback.

I experimented with using direct to MPEG-4 encoding instead of
RTJpeg, but the results were not good. The cpu was 40% idle, but I
couldn't get rid of the pauses/stutter. In comparison, if I
mythtranscode at the lowest process priority, the transcoder will
take 85-95% of the cpu and the playback does not stutter at all.

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