[mythtv-users] Problems with audio - WinTV PVR-250

[Matt White]

I've been running MythTV for a couple of months now, when I get a chance
to play with things.  I started out with an ATI TV Wonder, but last
month, I picked up a PVR-250 to replace it.

My main problem is that I seem to be getting quite a bit of skipping in
the audio at times.  It seems to occur most often on a dark or hazy
picture, but it also occurs at times when there is an almost-blank white
screen.

See below for details of my system....

Before I put the PVR card in, the system would record fine, but didn't
quite have the horsepower (crappy PC133 memory subsystem, I'm guessing)
to record & play at the same time - I'd get skipping.  I was running
640x480 MPEG4 (2200).  I replaced the TV Wonder with the PVR, and now
I can record and play at the same time with no difference (ie. I get
audio skipping either way).

I've seen this behaviour ever since I put the PVR card in, but I wanted
to do some testing before coming to the list with my problems :-)

I was originally running my audio out for the system through the Game
Theatre XP's coaxial digital output to my amp (nice sound).  However,
as you might guess, when the audio skips even a bit, it knocks sound
out entirely for several seconds as the amp tries to figure out what
is going on with the bitstream.

Last night, I switched to using the plain audio output on the onboard
Intel 810, and it's better, because it doesn't have to take that extra
time to sync back up again, but the skipping is still there.  It almost
sounds like the audio is slowing down when the picture gets dark (!)

I also tried killing off myth entirely and doing a cat test from
/dev/video0.  I recorded about 20 minutes of a show that I had seen
problems with (Third Watch - even got an episode that Myth had recorded,
so it was a good test).  In the Myth recording, I get the skips, but
in the direct recording, it's perfect!

I've tried multiple settings with the ivtv driver, as well, and it
doesn't seem to affect this at all.  I'm currently using 640x480,
bitrate 6000000, max_bitrate 8000000, dnr off.

My next test step is to replace the motherboard, memory (and probably
CPU) with something a little better, but since that's a bit more of
an expensive jump, I thought I'd see if anyone could see something
stupid that I'm missing :-)

Has anyone else seen this?  Any ideas?  I appreciate any suggestions/
assistance that you can offer!

My setup:

Pentium 4 1.5 MHz on Asus P4B (i845) motherboard
This is a cheap motherboard that uses PC133 memory

Drives:
   hda (boot & os): Samsung SV1021H (10 GB)
   hdb (myth storage): IBM DTLA-307075 (75 GB)

DMA & 32 bit enabled on both - /proc/ide/piix shows UDMA 5 for both
drives.

Memory: 768 MB PC133

Video Output: NVidia GeForce4 MX 420 (output via SVideo to a 42"
widescreen)

Audio: On-board intel-810 based plus a Hercules Game Theatre XP

lspci shows:

00:00.0 Host bridge: Intel Corp. 82845 845 (Brookdale) Chipset Host
	Bridge (rev 03)
00:01.0 PCI bridge: Intel Corp. 82845 845 (Brookdale) Chipset AGP
	Bridge (rev 03)
00:1e.0 PCI bridge: Intel Corp. 82801BA/CA/DB PCI Bridge (rev 12)
00:1f.0 ISA bridge: Intel Corp. 82801BA ISA Bridge (LPC) (rev 12)
00:1f.1 IDE interface: Intel Corp. 82801BA IDE U100 (rev 12)
00:1f.2 USB Controller: Intel Corp. 82801BA/BAM USB (Hub #1) (rev 12)
00:1f.4 USB Controller: Intel Corp. 82801BA/BAM USB (Hub #2) (rev 12)
00:1f.5 Multimedia audio controller: Intel Corp. 82801BA/BAM AC'97
	Audio (rev 12)
01:00.0 VGA compatible controller: nVidia Corporation NV17
	[GeForce4 MX 420] (rev a3)
02:09.0 Multimedia audio controller: Cirrus Logic CS 4614/22/24
	[CrystalClear SoundFusion Audio Accelerator] (rev 01)
02:0a.0 Ethernet controller: Intel Corp. 82557/8/9 [Ethernet Pro 100]
	(rev 08)
02:0d.0 Multimedia video controller: Internext Compression Inc:
	Unknown device 0016 (rev 01)


Software versions:

OS: Gentoo
MythTV from CVS (latest test 2003/06/17 ~10:30 PM)
ivtv driver from CVS (2003/06/09 7:00 PM, and again last night
	2003/06/17 ~11:00 PM)
NVidia binary driver (v4363)
Alsa 0.9.0_rc6 (with intel8x0 and cs46xx drivers)

-- 
Matt White                          whitem at arts.usask.ca
Arts and Science Computer Labs      University of Saskatchewan

We ride never worried 'bout the fall
I guess that's just the cowboy in us all
         - Tim McGraw..."The Cowboy in Me"