[mythtv-users] Another performance question...

[James L. Paul]

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On Friday 05 December 2003 21:58, Jeremy Hanmer wrote:
> I'm running the following system with no problems:
>
> 1.43ghz athlon-xp
> 512MB ram
> 7200rpm drive connected via firewire for all recordings (hdparm reports
> 28MB/s read speed)
> basically the same capture card (WinTV-DBX)
> Nvidia GeForce4MX with 64 megs
>
> so it looks like you should have more than enough power.  My first guess
> would be either motherboard (DMA issues, perhaps?) or buggy video
> drivers since it's a relatively new card (or are you maybe just not
> running the binary nvidia drivers?).

If disk DMA is confirmed to be working, I don't see it as an issue. At 30MB/s 
he's still an order of magnitude above the speed needed. Also, this wouldn't 
explain why only fast-moving video would be jerky and "talking head" video 
would be smooth.

> It may also be a matter of compilation flags, but with a 2ghz machine,
> I'd expect smooth recording/playback even with very laid-back
> optimizations.

I agree. Even with no optimizations he should be ok. My Athlon 1.4GHz kept up 
with a very similar config with about 50% CPU.

> To rule out a problem with Fedora (which I've heard there are plenty
> of), you could try KnoppMyth.  It's just a bootable cdrom image with a
> debian installation on it...should to the trick for testing.

Good idea. I suspect something weird going on. The only bit of (likely 
useless) advice I have is to pause the video for a second or two then resume 
playing live TV. Perhaps he is just a bit too close on the heels of the 
ringbuffer and needs to back of a second or so to prevent payback from 
running into the front of the buffer. It's a long shot in the dark, yes.

> http://hust.la/KnoppMyth/
>
> On Fri, 2003-12-05 at 22:14, Mark Frey wrote:
> > Not to add more noise on this sort of issue, but...I suppose I am
> > going to add more noise ;)
> >
> > I find myself unable to get live tv stutter-free on the following
> > machine:
> >
> > Intel P4 2.0GHz
> > 512 MB ram
> > 5400rpm HD (hdparm says throughput = 30MB/s, DMA is on)
> > NVidia GeforceFX 5200 video card with open source drivers
> > Latest Alsa with drivers for MAudio Delta66 soundcard
> > bt878 capture card, using btaudio (quite new version of bttv, whatever
> > installed with Fedora Core)
> > Latest MythTV from CVS
> >
> > If I try and run with the default live-TV settings (480x480, RTJpeg),
> > I'll be fine for "talking-head" type shows (News, etc.), but sports
> > programming (basketball for example) will cause more-or-less constant
> > stuttering (quarter second lurches every 1 or 2 seconds). Processor
> > usage stays near but below 50%.
> >
> > I've read through all the posts I can find, and it seems like some
> > people have no problem with performance with this spec machine, while
> > others have trouble with even beefier machines. I'm trying to figure
> > out what the magic is to make this work. I've instrumented the code to
> > try and determine where my machine is falling down. So far, from what
> > I can tell the decoder thread winds up spending alot of time waiting
> > for the ring buffer read thread to fetch data. Whether this is because
> > the hard drive is unable to keep up (the size on disk of each frame is
> > bigger for sports programming because it doesn't compress as well), or
> > because the read thread is getting starved because
> > compression/decompression is taking alot of processor time I don't
> > know. I'm kind of new to Linux so I don't know the best way to monitor
> > hard drive use (any pointers?)
> >
> > I've turned jitter reduction on and off, messed with the audio
> > buffering settings, all to no avail.
> >
> > My question is: Should this machine be able to do this? Are others
> > able to get smooth playback with this sort of setup, specifically for
> > sports programming?
> >
> > Thanks for any tips anyone can offer.
> >
> > -Mark
> >
> >
> > ______________________________________________________________________
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users at mythtv.org
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
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