[mythtv-users] FYI: MythTV on Celeron 1.1GHz

[Vince Busam]

I (finally) have MythTV working on my system, although when watching TV Live the
picture is like slow motion, with some jerks but apparently without losing
frames.  Sound is normal - doesn't seem to be affected by slow motion picture.
Separate recording and playback are fine.

I believe the CPU can't keep up with live TV, although the hard disk may
contribute to the problem.  Here is the data on my system for your information.

Celeron 1.1 GHz, 256KB PC133 RAM, VT133 chip (BTC motherboard), AverTV video
capture.  On board audio and VGA (set to 1024x768).  RedHat 9 (KDE), MythTV 0.8
from RPMs, Alsa Driver 0.9.3a.  (Running MythTV froze my system before I
switched to the Alsa driver.)

             CPU%
Task**     mythbackend  mythfrontend  system
------     -----------  ------------  ------------
Live TV*     75-93%        3-4%        5-8%
Recording    52-61%                    0.9-5%
Playback                  25-33%       2.5-5.1%

* CPU state seems to be about 85% user and 5-8% system.  I have about 3.5MB free
memory and swap used is <1MB.

** All with MythTV's default settings, e.g. 480x480 recording.

I used "top" in a different desktop under X, so some initial percentages where
different when I switched to the desktop with top.  Above are steady-state
values while viewing top's output.

So I think this shows a CPU bottleneck - unless a slow hard disk is causing
MythTV to eat up some CPU.  This is unlikely unless MythTV is polling the disk
I/O completion or availability.

xvinfo shows one screen and two adapters:  "video4linux" and "Trident Backend
Scaler".  Linux did not automatically detect the video card so I manually set my
Video Card type to "Trident Blade 3D(generic)".  I ran "dga" (hitting "b" key)
and it reports write speed of around 55,000K/s and read speed of about 8,500K/s.

I ran top and increase the speed (hit s, set to .3) Then ran hdparm -t
dev/hda  -- saw hdparm peak at 25%, but most reading were lower.

hdparm -c -d  tells me 32-bit I/O is on and DMA is on.
hdparm -tT    tells me buffer-cache reads are 89.51 MB/sec but buffered disk
reads on 10.11 MB/sec which does not seem good!  (should be about 40 according
to other MythTV posts)

Other /dev/hda settings:
  multcount   16(on)
  unmasking   on
  readahead   8(0n)

/proc/ide/hda/cache says 512.  Some other posts to the MythTV list have it set
to 2048.  (Can't figure out how to change it.)

The disk is ExcelStor Technology ES3220, 5400rpm, 9.5ms, 2mb cache, S.M.A.R.T,
Ultra ATA 33/66.

elevator settings:  read_latency 2048, write_latency 8192.

Hope this info helps somebody.

Vince