[mythtv-users] Trouble with HD playback

[John Goerzen]

On Fri, Oct 29, 2004 at 10:47:47AM -0700, Jarod Wilson wrote:
> On Friday 29 October 2004 07:02, John Goerzen wrote:

Thanks for the detailed and helpful reply, Jarod.  Let me try to give
some more info...

[snip]

> 
> Sounds very similar to what I saw with ALSA 1.0.6a. Backing off to 1.0.5a and 
> enabling aggressive sound card buffering fixed all my audio problems.
> 
> > I thought at first that the problem could be an underpowered CPU.
> 
> I still think that's the problem, after seeing that you're running an Athlon 
> XP 2200 and a Radeon. Which brings other issues to mind (I'll get to that at 
> the end)...

Could be right...

> > However, top showed no process consuming large amounts of CPU time and
> > the CPU hovered around 50% idle.
> 
> You never got to the point where video was actually being decoded and 
> displayed. My Athlon XP 3200 runs around 85% utilization right now when 
> playing back HDTV content (I have kernel deint enabled).

Sigh.

> I don't get perfectly smooth playback of HD previews myself.

Good :-)

> > Configuration:
> > MythTV 0.16
> > Athlon XP 2200+ 1.8GHz
> 
> Definitely under-powered.

I tried mplayer, which seems to confirm that.  I haven't yet researched
what else this motherboard can take, but assuming it could take a fast
enough Socket A CPU, do you have a suggestion?

> > 256MB RAM, 100MB free
> 
> Not sure if 256 is sub-optimal for HD, I've got 512.

I've got plenty of RAM free, so I'm pretty sure that's not the issue.

> > ATI Radeon 9200 video card
> 
> Ick. My Radeon 9000 had multiple issues playing back HD content. But they 
> differed depending on the driver used... Switching to an nVidia card 
> immediately cured all those problems. However, its been a while, maybe the 
> fglrx driver sucks a little less wrt HD playback now... :-)

My motherboard has some sort of on-board nvidia stuff.  I stopped using
it because the ATI card had a DVI out port, which I briefly experimented
with using to drive the TV.  When I stopped, it was all set up for the
ATI, and the ATI seemed to work better and a little faster, so I kept
it.  Plus it freed up some system RAM (the onboard stuff uses system RAM
for the framebuffer -- that's icky too.)

The fglrx driver has done quite a good job for me.

> >   XFree86 4.3.0
> >   ATI fglrx 3.14.1 driver
> >   Originally was using 640x480 resolution.  Also tried 800x600.  No
> >   difference.  24bpp.  Xv enabled, Xvmc disabled (I think -- I have no
> >     idea how to turn Xvmc on or off)
> 
> Ouch, you're tacking some serious scaling on top of trying to decode. Sounds 
> like you're outputting through SVideo.

Yes, I have had trouble making 960x540p work correctly through the
SVideo out port.  A proper VGA-to-component adapter is on the list but
not purchased yet :-)

It was my impression that with Xv support in hardware, scaling was done
in hardware (by the video card), and thus not an issue... am I mistaken there?

> > Debian sid
> > Sound using ALSA, AC97 onboard
> 
> Native ALSA output, or OSS emu output? My audio experience improved a bit when 
> I started outputting raw AC3 to my amp.

Native ALSA, but not AC3.  My system does have both coax and optical
digital out, but I haven't played with them yet.

> > Let me know if there's any other information I can provide.
> 
> Why you're not getting any video at all, I don't know, but you're definitely 
> short on processing power. How do those files look when played back with 
> mplayer?

That was an interesting test.  I tried the ABC file.  It played
*beautifully* for the first 10 seconds or so.  Perfect video and sound.
Then after 10 seconds, the sound dropped out -- video continued.
mplayer displayed a message saying my system was way too slow, CPU
utilization was indeed 99%, and yet the video continued playing until
what I assume was the natural end of the clip.

I have no idea how it managed that if my system was way too slow.  Or
with 99% CPU utilization for that matter.

While we're on the topic, are HD streams really such a higher bitrate
than DVDs?  This machine has no trouble at all playing DVDs.  I know the
resolution is somewhat higher, but that just seems extreme...

Thanks again.

-- John