[mythtv-users] Digital Pegs CPU

Rod Smith mythtv at rodsbooks.com
Sat Nov 29 19:23:47 UTC 2008

On Friday 28 November 2008 02:41:39 pm Paulin wrote:
> You are correct.  I did screw up and they were the same card.  Anyway I
> tried again and I believe this is the H1250 card now.  Here you go.
> Size: 3195849224

That's an HD recording -- 1920x1080 resolution and 38,609,200 bps vs. 720x480 
resolution and 6,000,000 bps for your other (SD) recording. Since your SD 
recording is consuming 70% of your 1GHz VIA CPU's CPU time, IIRC, it's no 
surprise that an HD recording will consume 100% of the CPU time and produce 
stuttering results. If anything, I'm surprised it's only stuttering once 
every few seconds, as per your description.

I don't want to say it's impossible to play your HD recording on your 1GHz VIA 
CPU, but IMHO it's not worth the effort to try, unless you've got a sure-fire 
recipe from somewhere. The way I see it, you've got a few choices:

1) Ditch the digital card, get another SD card, and record directly. This is
   a good option if all your HD channels are available in analog SD form from
   your cable company and if you're watching on an SD set with no plans to
   upgrade in the immediate future.

2) As above, but use a digital converter box to tune HD channels. This may be
   a good option if you want to receive OTA (which is going all-digital in
   February) or if you want to tune some HD channels that you can't tune
   directly in SD. Note that a cable box from your cable provider qualifies
   as a digital converter box.

3) After recording, transcode every HD recording to SD. This will work well
   if you don't mind the delay. (I'd guesstimate that it'll take 4-10 hours to
   transcode every hour of HD content, given your CPU. If you've got a faster
   system you can use as a transcode-only backend, the time can be reduced.)
   If you've got an HD TV set, you'll lose HD quality, although your
   transcoded HD recordings will probably still look better than the SD
   recordings sent via an analog signal.

4) Reconfigure your digital card to tune only SD digital channels, rather than
   HD digital channels. This might or might not be possible, depending on the
   signal source(s) available to you. If it is possible, the resulting quality
   should be similar to a downconverted/transcoded HD signal, as in #3, but
   without the delay.

5) Upgrade your motherboard and CPU. Based on my experience with a 3GHz Intel
   Celeron-D, I recommend at least a 3GHz Intel CPU (or equivalent AMD CPU).
   A 2GHz CPU might be adequate for playing back HD content, but only just
   -- there'll be very little margin for other things happening (such as
   commflagging or database updates) while watching a recording.

Sorry to be the bearer of bad news, but I think you're just trying to do more 
than your CPU is capable of doing.

Rod Smith

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