[geeks] mp3 skippage

[Kris Kirby]

On Wed, 14 Mar 2001, Jonathan Katz wrote:
> I have a AMD K6-3/400 w/ 128M of RAM. Win2k, ATI Rage 128 Pro,
> 12GB ATA66 disk, AD1816-based (soundblaster clone) PnP ISA
> sound card, netgear 10/100 ethernet. A pretty solid machine.

Dual Celeron 433, 384MB of RAM, Win2K, Same video, Twin ATA66 Seagate 5400
RPM 17.2GB drives, SB16, Yamaha SA2 (SAx), PCI NE2K (RTL8029), AMI
MegaRAID 433 (Single channel SCSI-LVD-RAID). (What interrupts? I don't
have any left; LPT1 is off!)

> Over the past year or so I've had the system it went from win98
> to win2k (not an upgrade, reload w/ ntfs, etc.) Anywho, it 

No NTFS; I want to be able to recover when windows poops something big.

> was working fine (could play mp3s w/o problem.) Now when I
> go to play mp3s they "skip" -- either they get decoded too
> fast for a buffer on the sound card (sounds like it is being
> remixed with a frame or two played out of order) or it skips
> like when you drive too fast over rail-road tracks and the CD
> player in the car skips. Needless to say this is really
> annoying. It doesn't just do it on MP3s but all sounds (system
> "ding" when you click the wrong thing, windows startup .WAV,
> etc.)

It's a windows drive issue, I'm certain. I've had it crop up a few times
and hoped it would go away, seems it did or I gave up. Took over six
months and two installs to happen. Major bummer. I was chocking it up to a
"hung" interrupt, but... I don't think it happens when I pull the NICs. 

> Things we know it isn't:
> o Disk I/O contention. My mp3s live on the RAID array. Playing
> them 'over the wire' on my P3/450 laptop this doesn't occur.

30GB RAID5 - Lost 10GB once before when one of two drives in a RAID1
stripe died. 

> o CPU can't handle the mp3. using 'task manager' the CPU usage
>   never seems to go above 20%, even w/ Netscape open. It's
>   usually <10%. However, when it does 'skip' the graph showing
>   cpu usage is pegged, but the analog/number readout shows
>   otherwise.

Not an issue; dual procs. 

> o Win2k. I loaded OpenBSD (2.8/latest) on another 10GB drive I
>   own, and mpg123 has the same problem.

Interrupt problem; are you reading the MP3s over the 'net? 10/100 cards
don't like suspended interrupts, which is exactly what happens when a
fifo-less I/O card is used (sound-card).

Someone will probably try to debate this with me, but I've seen real-world
confirmation. 

> Theories:
> o Buffer on the soundcard isn't working (overfull/underrun). I
>   have no way of knowing this/testing this. Maybe get another
>   soundcard?

Maybe. 

> o the FP on the AMD processor isn't the world's best, and is
>   causing this headache

AMD's FPU is ok. I've got a K5-75 that, when doing nothing but, can play
MP3s all day long a 60-65% load.

> Any ideas/inputs/suggestions are welcome. I've even elevated
> the process priority of winamp (which I did upgrade to its
> latest version) to 'real-time.' I also reniced the mpg123
> priority to a full -20, to no avail.

Duh-uh... Wanna get locked out of your machine? If you're going to do
something like that, renice your shell as well.

-----
Kris Kirby, KE4AHR          | TGIFreeBSD... 'Nuff said.
<kris at nospam.catonic.net>   |    
-------------------------------------------------------
"Fate, it seems, is not without a sense of irony."