[mythtv-users] Trouble with HD playback

[Jarod Wilson]

On Friday 29 October 2004 07:02, John Goerzen wrote:
>
> I downloaded the ABC and CBS test files from wilsonet.com that were
> posted here recently.  I have a pcHDTV card on order and thought they
> would help me get things set up in advance of its arrival.

They definitely should.

> These are .nuv files, and I just overwrote the .nuv files for two
> programs I was going to delete.  That saved me having to manually add
> records to the MySQL database.

That's what I did too. There's an import script somewhere that makes adding 
files easy, but overwriting something you're already done watching works 
quite well.

> When I tried to play the files, I got no picture at all (black screen).

That's not good.

> The sound worked fine for the first 3-5 secnods.  After that, it got
> choppy.  It's not that any sound was dropped; rather, there were little
> pauses inserted throughout the playback.  It was as if it alternated
> between pause and playback every tenth of a second or so.

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)...

> 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).

> My hard drive is running in UDMA133 mode and didn't appear to be
> stressed either.

The hard drive definitely shouldn't be an issue.

> Next strange thing: if I would highlight the program in question in the
> recorded programs guide, the show would start playing like usual in the
> little window.  It looked like it might possibly be a little slow, but
> it's hard to tell in a small window without sound.

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

> Configuration:
> MythTV 0.16
> Athlon XP 2200+ 1.8GHz

Definitely under-powered.

> 256MB RAM, 100MB free

Not sure if 256 is sub-optimal for HD, I've got 512.

> Samsung SP1604N hard drive

I'm now running the SATA version of this drive in my pcHDTV box.

> 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... :-)

>   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.

> 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.

> Deinterlacing: tried disabling it, or using kernel

Kernel deint is the most cpu-intensive of the deint filters, I believe. I'd 
start with deint disabled entirely to minimize cpu usage. I'm most partial to 
kernel deint, but all of them work for me.

> 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?

-- 
Jarod C. Wilson, RHCE
jcw at wilsonet.com

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