[mythtv-users] Initial experience with an ION backend

[Jim Stichnoth]

My Zotac IONITX "C" board arrived yesterday (with a single-core
hyperthreaded Atom 230).  Before setting it up in its permanent
position as a completely silent myth frontend, I thought I would see
how it might perform as a combined BE/FE machine.  I installed
MythDora 10.21 onto a spare 160GB SATA drive and "borrowed" one of the
HDHRs on the network, which receives ATSC OTA broadcasts.

Assuming one uses VDPAU, my main concern with the ION board is how
well it can keep up with commercial flagging, especially if one is
interested in real-time flagging.  I configured the backend to allow
commflagging to start while the program records, and to allow only one
job at a time (since it's only a single core).

I started with a one-hour 720p program on FOX.  Commflagging completed
in 1 hour 15 minutes, and took about 55 minutes of CPU time according
to "top".  It was using close to 100% CPU for most of it, but dropped
down to 50% for some reason during the last 15 minutes (with the rest
of the CPU being mostly idle).  Mythweb was reporting 60-70 fps while
flagging was going on.  I guess the 720p recording is at 60 fps.

Next, a 30-minute 480i program on a PBS subchannel.  Commflagging
didn't actually start until 15 minutes in (because of the previous
commflagging job taking an hour and 15 minutes).  But it caught up to
real-time by the time the 30-minute program ended!

Finally, a 1080i program on NBC.  I started recording the Today show
which goes from 7:00-11:00am, though I actually started recording
around 7:30.  By 10:15, mythweb is reporting 63% complete and a frame
rate of 26 fps, and "top" shows 148 minutes of CPU time.  I'm guessing
that the 1080i recording is treated as 30 fps and commflagging is
running a bit behind real-time.

While a single recording was going on, "top" reported the mythbackend
process taking 7-11% CPU time.

My conclusion is that if your recording/commflagging requirements are
modest, an ION system could make a perfectly suitable combined BE/FE
myth system.  It should easily commflag standard definition programs
in real-time, and almost keep up with real-time for high definition
programs.  (I am very pleasantly surprised by this, as I expected
commflagging performance to be much worse.)  If you tend to have
bursts of simultaneous recordings, like when the networks compete in
lucrative timeslots, and you care about near real-time commflagging,
you might want to consider a dual-core Atom board and hope the cooling
fan is unnecessary (though if you already have a spinning disk for the
recordings, maybe the fan isn't so bad, as far as noise is concerned).

Jim