[mythtv] WriteAudio: buffer underrun, when playing from CD/DVD combo drives
Mr. Demeanour
mrdemeanour at jackpot.uk.net
Sun Mar 15 15:23:25 UTC 2009
Hi,
I'm running 0.21 svn-fixes, compiled locally.
Hardware is an Via EPIA SP fanless motherboard, with 512 Mb of RAM. The
system boots Debian lenny off an NFS server; there is no local hard
disk. This machine runs the frontend only - the backend is elsewhere.
Problem: I cannot play CDs or DVDs in MythTV, due to "WriteAudio: buffer
underrun" problems. I can play both CDs and DVDs in Xine, however, and
CD audio also works fine in alsaplayer and vlc. Interestingly, Mplayer
_doesn't_ work; it has the same trouble with CD audio exhibited by
MythTV (it pauses output at the same places).
At one time this hardware worked; I can't think of anything _relevant_
that I changed, other than updating MythTV. When CD and DVD playback
last worked, this system was booting off a local hard disk - I changed
quite a lot of things to get network boot working the way I wanted, but
I can't see how those changes might have given rise to this problem.
The following output shows an audio CD being played:
2009-03-15 13:27:42.129 CD status has changed.
2009-03-15 13:27:45.445 Opening audio device 'default'. ch 2(2) sr 44100
2009-03-15 13:27:45.446 Opening ALSA audio device 'default'.
2009-03-15 13:27:54.914 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.117 WriteAudio: buffer underrun
2009-03-15 13:28:00.160 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.220 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.281 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.348 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.384 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.451 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.487 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.523 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.589 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.625 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.695 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.731 AO: dropping back audio_buffer_unused
2009-03-15 13:28:00.799 AO: dropping back audio_buffer_unused
2009-03-15 13:28:18.564 WriteAudio: buffer underrun
2009-03-15 13:28:23.733 WriteAudio: buffer underrun
Each "buffer underrun" message corresponds to either the initial pause
before playback commences, or a stutter during playback. Playback
consistently runs OK for the first 10-20 seconds, then stops for a few
seconds. Thereafter audio becomes choppy over a timescale of one or two
seconds.
The optical drive is as follows:
hdb: MATSHITACD-RW CW-8124, ATAPI CD/DVD-ROM drive
The following all work fine (on the whole):
- DVB-T Live TV
- DVB-T recording (to an NFS mount)
- Playback of recordings
- Ripping of CDs (from this frontend) to FLAC
- Playback of ripped CDs
Audio playback uses ALSA:default, through the stereo analogue output.
Things I have tried:
- Using an external Samsung USB CD/DVD combo drive
- Using an external SB Live! USB soundcard
- Using PATA_VIA driver instead of BLK_DEV_VIA82CXXX and BLK_DEV_IDE
- Tinkering with kernel scheduler options
- Disabling ACPI either on the motherboard or in the kernel, or both
- running as root
None of these have had any effect on the problem.
Mythfrontend has the following options set:
- Aggressive Sound card Buffering
- Extra audio buffering
mythtv at sila:~$ lspci
00:00.0 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 Host Bridge
00:00.1 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 Host Bridge
00:00.2 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 CPU Host
Bridge
00:00.3 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 Host Bridge
00:00.4 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 Host Bridge
00:00.7 Host bridge: VIA Technologies, Inc. CN333/CN400/PM880 Host Bridge
00:01.0 PCI bridge: VIA Technologies, Inc. VT8237/VX700 PCI Bridge
00:0d.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306 Fire II IEEE
1394 OHCI Link Layer Controller (rev 80)
00:0f.0 IDE interface: VIA Technologies, Inc.
VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)
00:10.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 81)
00:10.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 81)
00:10.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 81)
00:10.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 81)
00:10.4 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 86)
00:11.0 ISA bridge: VIA Technologies, Inc. VT8237 ISA bridge
[KT600/K8T800/K8T890 South]
00:11.5 Multimedia audio controller: VIA Technologies, Inc.
VT8233/A/8235/8237 AC97 Audio Controller (rev 60)
00:12.0 Ethernet controller: VIA Technologies, Inc. VT6102 [Rhine-II]
(rev 78)
01:00.0 VGA compatible controller: VIA Technologies, Inc.
CN400/PM800/PM880/PN800/PN880 [S3 UniChrome Pro] (rev 02)
sila:/home/mythtv# hdparm -i /dev/hdb
/dev/hdb:
Model=MATSHITACD-RW CW-8124, FwRev=DZ13, SerialNo=
Config={ Fixed Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic }
RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
BuffType=unknown, BuffSize=0kB, MaxMultSect=0
(maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: sdma0 sdma1 sdma2 mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 *udma2
AdvancedPM=no
Drive conforms to: Unspecified: ATA/ATAPI-2,3,4,5,6
* signifies the current active mode
At one time I suspected IRQ problems, but I think this is now OK
(especially since the same problems were encountered using the external
soundcard and CD combo):
sila:/home/mythtv# cat /proc/interrupts
CPU0
0: 6636678 XT-PIC-XT timer
1: 2 XT-PIC-XT i8042
2: 0 XT-PIC-XT cascade
7: 1 XT-PIC-XT
8: 1 XT-PIC-XT rtc0
10: 70938 XT-PIC-XT uhci_hcd:usb4, uhci_hcd:usb5
11: 4 XT-PIC-XT ehci_hcd:usb1, VIA8233A
14: 493429 XT-PIC-XT ide0
15: 523550 XT-PIC-XT uhci_hcd:usb2, uhci_hcd:usb3, eth0,
via at pci:0000:01:00.0
NMI: 0 Non-maskable interrupts
TRM: 0 Thermal event interrupts
SPU: 0 Spurious interrupts
ERR: 1
Unfortunately the BIOS on this motherboard doesn't enable me to rejig
the IRQs on the PCI devices. All of the devices are motherboard devices
- there is nothing in the solitary PCI slot, and the graphics is
motherboard graphics. AFAICS there is no APIC on this motherboard.
Google turns up a lot of "WriteAudio: buffer underrun" problems, but
none of the solutions I've seen have worked for me. Has anyone got a
suggestion that I might not have tried?
Thanks,
--
MrD.
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