[mythtv-users] HDTV on Myth -- not a "myth" CONCLUSION

[Jarod Wilson]

On Tuesday 12 October 2004 00:29, Joe Barnhart wrote:
> First off, I want to thank everyone who shared
> information and enlightened me on this topic.  As
> always, I have learned a tremendous amount from the
> keep knowledge well of this list.

Me too! :-)

> 2. Xv has higher computational load than XvMC.  A
> marginal processor won't cut it.  The hyperthreading
> of the P4 is an advantage, but it isn't clear yet how
> much.  I know my Athlon 2500+ is not up to the task of
> decoding 1080i material on Xv.

D'oh. You have a 2500? I could have sworn you had a 2800. That makes a whole 
lot more sense now. The 2500 runs a lower system bus speed (333 max, IIRC), 
and you've likely only got 256k on-chip cache, versus my 3200, which is 
running on a 400MHz system bus with 512k on-chip cache. I think the cache is 
likely a big win for HDTV. I've got a system with a 2600/333/256 in it, maybe 
I'll give that a shot at some point for comparison's sake... You must be 
drilling the cpu pretty good in Xv mode...

> 3. The video card makes a tangible difference.  I
> tried an nVidia 5200 card as a drop-in replacement for
> my GF4MX card, and I was able to smoothly decode 1080i
> on Xv, but only while there was no commercial flagging
> going on in the background.  One other difference in
> the card was AGP 8x in the 5200 vs. 4x for the GE4MX.
> Neither card chose to use fast writes, however.

Good to know. I'm glad I decided to get a 5200 for the hell of it when I got 
the new mobo for my box. :-)

> 6. Don't use alsa 1.0.6 drivers, they have been
> implicated in video jerkiness.  Do enable "extra audio
> buffering."  Do use gcc 3.4 instead of 3.5 for
> slightly better performance (what about earlier
> releases? I'm on gcc 3.3)

I believe that should be use 3.4 instead of 3.3 for slightly better 
performance. I'm not even sure there's been a 3.5 release yet, 3.4 is pretty 
bleeding edge. I'm going to try moving my box to Fedora Core 3 next weekend, 
which includes 3.4, so I'll finally rebuild Myth w/3.4 at that point. 
Definitely interested to see if I get any performance gain...

> 7. If stability is of highest importance, match the
> hardware and software used by the developers of HDTV
> on Myth.  Use the Pentium 4, enable HT, and choose Xv
> on an nVidia card.  If you want to contribute and help
> debug new platforms, choose something else. ;-)

One of these days, maybe I'll try swapping in a Radeon video card for 
giggles... I have too many "one of these days" projects...

> I hope this adequately summarizes what I've learned in
> the last couple of days.  I'm limping along with my
> Athlon 2500 and GeForce 5200 card right now, but
> planning to replace the mobo with a more capable one
> and dedicate this one to a BE server with lots and
> lots of HD-3000 cards and stacks of cheap Fry's hard
> disks (I wish).

:-p

One of these days, I'll also get around to finishing the HDTV page on my web 
site. Pretty much all of this is good info for it (as well as the mythtv.info 
wiki, as Doug mentioned).

-- 
Jarod C. Wilson, RHCE
jcw at wilsonet.com

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