[mythtv-users] HDTV question

Tue Oct 21 19:20:15 EDT 2003

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Brandon Beattie
Sent: Tuesday, October 21, 2003 5:51 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] HDTV question

On Tue, Oct 21, 2003 at 09:50:51AM -0400, Jason Schloer wrote:
> 
> On Mon, Oct 20, 2003 at 09:26:25AM -0400, Jason Schloer wrote:
> > Okay so I've had the pcHDTV a couple weeks now and haven't had much
> > chance to play with it. I did notice fairly quickly though that it
> > wasn't playing things back quickly enough. So I went out and bought
a
> > different GeForce with IDCT acceleration so I could use that.
Compiled
> > myth for it tried it out, got the black and white overlays
indicative
> > that it was working, but it was still slow, if not slower than
before.
> > So I took it back and bought a faster processor, from XP 2000+ to XP
> > 2600+. Tried it out again and again it was choppy audio and video.
So
> I
> > think my bottleneck may be elsewhere. I need to do more testing,
like
> > checking CPU usage while watching to find out if it is pegged or has
> > some room. I was wondering if anyone who's had some experience with
HD
> > streams could be of any help. Where should I check? I've got a 7200
> RPM
> > HD, 512 megs of ram, Asus A7N8X mobo. I'm running a vanilla Mandrake
> 9.1
> > kernel. Also, will any of the hardware decoders help with this?
Thanks
> > for all your help can't wait to start really using this stuff. 
> > 
> > Jason Schloer
> > P.S.
> > The stream I was trying to watch is a 0 fps 480P stream with a 48000
> hz
> > AC3 audio track.
> > 
> > 
> 
> > _______________________________________________
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> > mythtv-users at mythtv.org
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> 
> -----Original Message-----
> From: mythtv-users-bounces at mythtv.org
> [mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Brandon Beattie
> Sent: Monday, October 20, 2003 11:43 AM
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] HDTV question
> 
> I'm running a 2600+ (333fsb) AMD XP system (Via motherboard that is
> junk).  Every once in a while I get choppy audio/video but this is due
> to bugs, not lack of hardware resources.  Try running 'mplayer
> /dev/video32' and see how that runs, or run xine.  If both of those
are
> still choppy, then check bios settings.  Sometimes running optimal
> settings actually slows down a system as I have found out.  Also check
> how much disk io you're using.  It shouldn't be a problem, but maybe
> your drive is very slow?  (I run a 7200 ATA 100 drive, with my root
> filesystem on another drive than where I store data to, but I've seen,
> and also at one time, ran it off a single 7200 rpm drive).  Running
that
> mplayer command won't store to disk, just memory.  I still need to try
> xvmc support in Myth.  I spent my few hours this weekend debugging
> another pchdtv issue with the 2.4.20 debian kernel, (buffer
> overrun/btatsc irq mask clearing) and upgrading to 2.4.22 fixed this
> problem, but that's all I had time for, and to find out that
> mythfrontend locks when changing a channel for myself).
> 
> 
> I just noticed your specs, not sure how I missed them before, but you
> should be fine.  I use about 87% CPU when watching a 1080i stream and
> about 14% when watching a 480p stream.  Let me know how mplayer
(Latest
> version) and xine-hd work.
> 
> --Brandon
> 
> 
> Okay, so I got home last night and took a look at it, turns out I
still
> had my XvMC enabled version of Myth installed. Noticed when I brought
up
> the pause menu. Recompiled without XvMC and it worked much better.
Still
> a little choppy but not maxing out CPU, so I turned on the
experimental
> AV sync and it works nice and smooth. Oh the other thing I realized is
I
> wasn't watching a 480p stream. Got confused because it had those nice
> black bars on the sides, but it was actually a 60 fps 720p stream. So
> I'm a little less worried now. I think a little more tweaking and it
> should be all good. Anyway, thanks all for the help.
> 
> -Jason
> PS
> My drive seems to be okay btw. I sent the whole file to /dev/null in
> under 3 minutes, for a 1 hour show. 
> 
> 

I'll have to try the AV sync options sometime.  As for writing to
/dev/null, depdning on your filesystem, it's writing that is most IO
entensive for the drive.  I'm starting to experience problems when doing
an updatedb and recording two hdtv streams (from 2 hd cards) at the same
time.  All 256MB of memory gets used up, so I'm looking at getting more
memory and letting the kernel use more to handle hopefully up to 4 hd
streams at once.  I also will be moving to another filesystem, as ext3
has the worst writing speeds of any current fs.

--Brandon

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> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

Wow, 4 HD streams. What are you doing? I'm lucky to get 4 usable HD
streams at all. Anyway, as for the test I actually was trying to just
test the read speed since the write speed shouldn't matter much for
watching an existing recording which is what I was trying to do. Because
of all of this I'm thinking of taking the 200+ CPU I replaced and
building a backend. Then using the 2600+ for the frontend. So that said
what should I use for an HDTV frontend given the limitiation of using an
AMD Athlon XP. I'd like to have spdif out though I don't mind buying a
CHEAP card to do it. 

So currently I have:
Athlon XP 2000+
Athlon XP 2600+
Asus A7N8X
Geforce 4 Ti 4200 64 MB
60 GB drive
 4 GB drive (probably for the frontend machine, just for OS essentially)
512 MB Corsair PC2700 

I'd like to be able to watch an HD stream and possibly a PIP SD stream I
haven't had much luck with XvMC acceleration in fact it seems to always
slow things down even with IDCT. Anyway, I'd love to hear people's input
as far as what they think I'll need. I'm trying to do it as cheaply as
possible. Oh and I still need a VGA to component converter, so if I can
use an ATI with that dongle and people think I'll get a reasonable
picture without too much work I'd love to hear about it. Thanks again.
-Jason