[mythtv-users] stutter while recording two programs at once

[Judd Tracy]

On 8/29/06, Brad DerManouelian <myth at dermanouelian.com> wrote:
> On Aug 29, 2006, at 10:15 AM, Steven Adeff wrote:
>
> > On 8/29/06, Tony Lill <ajlill at ajlc.waterloo.on.ca> wrote:
> >> Brad DerManouelian <myth at dermanouelian.com> writes:
> >>
> >>> I've got an AMD64 box with a SATA II drive formatted as JFS
> >>> dedicated
> >>> to recorded programs. music, photo, videos are on a separate SATA
> >>> drive and the system runs from a PATA drive - all are 7200 RPM with
> >>> 8MB buffers.
> >>>
> >>> I've got a PVR-350 and an HD-5500 card in the box which is also my
> >>> frontend. I'm getting weird stuttering when recording on both tuners
> >>> at the same time. The HD stream looks perfect but the stream from
> >>> the
> >>> PVR-350 will show a single frame from about a second before the
> >>> current position. It happens intermittently but often enough to be
> >>> REALLY annoying. I've found that it's in the recording this way
> >>> since
> >>> the rogue frames happen at the same place when I play back every
> >>> time. I have a feeling it MIGHT only be happening when watching a
> >>> program and recording two others at the same time. I had anticipated
> >>> 3GB/sec on the SATAII drive would be enough bandwidth to watch 1,
> >>> record 2. Is this not the case? Is there a good way to test? Do I
> >>> finally need to submit and start transcoding every program I watch
> >>> and deal with sub-par quality?
> >>>
> >> Are you getting any messages from the ivtv driver about your
> >> application not reading fast enough? Look in
> >> /var/log/messages.
> >>
> >> There's a known problem where database access slows
> >> things down enough to cause dropped frames. It's more likely to
> >> happen
> >> in the first minute of the recording, 'cause it hits the database
> >> more
> >> often then.
> >
> > it may also be a pci latency issue, I had similar occur with a PCI ATA
> > card I'm using for part of my RAID array once I changed the latency
> > this went away.
>
> The only thing that looks like an error or warning in my /var/log/
> messages is:
> Aug 27 16:11:13 mythtv kernel: ivtv0: Unreasonably low latency timer,
> setting to 64 (was 32)
>
> Oh.. and ssh attacks attempted and failed on my system. :)

Try taking a look at this:
http://www.mythtv.org/wiki/index.php/PCI_Latency

Judd