[mythtv-users] HDTV question

Tue Oct 21 18:10:15 EDT 2003

On Tue, Oct 21, 2003 at 06:20:15PM -0400, Jason Schloer wrote:
> -----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.
> > > 
> > > 
> > 
> > > _______________________________________________
> > > mythtv-users mailing list
> > > mythtv-users at mythtv.org
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > 
> > -----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
> 
> > _______________________________________________
> > mythtv-users mailing list
> > 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
> 
> 
> 
> 
> 

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

I'll probably turn my 2600+ into a backend when a CPU comes out that can
de-interlace 1080i in realtime.  -- But to note, if your backend server
will be doing any transcoding (Such as mine will to every show recorded
(For changing the resolution to 1024x576 and de-interlacing) a backend
with some CPU is needed.  Also, if you start writing a lot to disk you
can need more CPU.

As mentioned earlier (And I hope the guy who replied right before you
also reads this) is I will probably go to JFS.  Reason is because it's
fairly stable (I've had some ext3 problems, but changing back to ext2
solved them).  I have looked through dozens of bench marks and everyone
has different results.  JFS I believe has steadily been in the top few
each time.  I also need a journaling filesystem (It would not be good to
fsk a terabyte of disk (Which I hope to have in the next year *wish*)
if you loose power often and for long amounts of time).  

If you're wondering, the benchmark that I believe shows the best results
for comparing is: http://fsbench.netnation.com/  (It is done with bonnie
and iozone, not "rm <file> or "copy file" as I've seen way to many
"tests" done this way lately.  I don't mean to start an FS war either.
JFS also does show good results when dealing with >1GB files.  If I'm
wrong, let me know, no fs wars though. :)

--Brandon