[mythtv-users] HDTV question

[Brandon Beattie]

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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> 
> -----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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