[mythtv-users] Jerky picture esp on panning shots

[William Powers]

Greg Cope wrote:
> Hi All,
>
> I get quite a jerky picture especially on panning shots.  Everything
> is still watchable, but is just not quite right.  Along with a size
> issue (My display is too small so I am missing 10 or so edge pixel)
>
> The Jerky picture is similar to the effect of panning shots on some
> LCD's that can't quite seem to keep up with the picture changing.
>
> WAF is quite low because of this, otherwise she is starting to use
> myth, which must mean its pretty good otherwise!
>
> Hardware is Via SP13000, FC4, atrpms, 2xNovaT DVB's 512Mb ram, Sony
> CRT TV via Svideo.  OpenChrome Drivers.
>
> Is this;
>
> - Myth - something wrong with my config.
>
> - Bit rate issue - the BBC here use high bit rates so recordings tend
> to be very large and therefore probably good quality, with lots of
> data to shift/change
>
> - X issue/Openchrome issue.
>
> - The TV (doubt that as its pretty good otherwise).
>
> Any ideas?
>
> Greg
I get jerkiness while watching HD recordings, but only when the backend 
is also busy with something that involves a lot of unrelated I/O, such 
as transcoding, compiling, etc.  FWIW, my jerkiness started out as 
full-blown stuttering and I've managed to get it down to just an 
occasional hesitation.  Things that helped along the way, in order of 
importance:

1.  Upgrading from a 2.8G P4 Northwood to a dual-core Pentium D 820.
     (Simply O/C'ing the 2.8G Northwood did *not* visibly help.)
2.  Changing the hard drive used to store recordings from a PATA100 to a 
SATA150.
3.  Enabling write-caching on the hard drive used to store recordings.
4.  Setting 'swappiness' to '0'.
5.  Tinkering with PCI latencies (decrease the VGA card, increase the 
sound card and IDE controller).

Things I haven't tried yet:

1.  Increasing physical memory from 512M of memory to 1G.
2.  Disabling swap altogether.
3.  SATA300.
4.  NCQ.
5.  Striping the recordings mount.

Bill