[mythtv-users] DMA buffer DeQueue failed!

Gary Raposo gary at raposo.ca
Tue Nov 4 14:19:34 EST 2003 

I was reading through Steven Finnegan's thread "No Playback, Live TV OK" 
and thought I'd check if my live TV stream was affected.  Sure enough, the 
live TV was perfectly fine!  No glitches whatsoever.  Checked 
/var/log/messages and none of the DMA errors were being logged.

I then started recording and instantly /var/log/messages started logging 
the "DMA buffer DeQueue failed!" messages BUT the live TV is completely 
unaffected -> perfect video and audio!  When the recording completed, the 
errors stopped.  I checked the recorded content and it was full of 
glitches.  Typical errors:

Nov  4 14:00:22 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
Nov  4 14:00:22 mythtv kernel: ivtv: DEC: free_q: 0 elements
Nov  4 14:00:22 mythtv kernel: ivtv: DEC: dma_q: 0 elements
Nov  4 14:00:22 mythtv kernel: ivtv: DEC: full_q: 60 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: free_q: 0 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: dma_q: 0 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: full_q: 70 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: free_q: 0 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: dma_q: 0 elements
Nov  4 14:00:28 mythtv kernel: ivtv: DEC: full_q: 76 elements

I don't understand this.  Maybe someone can shed some light as to the 
difference between watching live TV and recording.  Wouldn't both be using 
the same IVTV drivers?  Why is the live TV unaffected when the recording is 
going on.

The only other errors I could find in /var/log/messages were logged on reboot:

Nov  4 12:49:51 mythtv kernel: bttv: driver version 0.7.104 loaded
Nov  4 12:49:51 mythtv kernel: bttv: using 4 buffers with 2080k (8320k 
total) for capture
Nov  4 12:49:51 mythtv kernel: bttv: Host bridge is PCI device 1039:0651 
(Silicon Integrated Systems [SiS])
Nov  4 12:49:51 mythtv insmod: 
/lib/modules/2.4.20-20.9/kernel/drivers/media/video/bttv.o: init_module: No 
such device
Nov  4 12:49:51 mythtv insmod: Hint: insmod errors can be caused by 
incorrect module parameters, including invalid IO or IRQ 
parameters.       You may find more information in syslog or the output 
from dmesg
Nov  4 12:49:51 mythtv insmod: 
/lib/modules/2.4.20-20.9/kernel/drivers/media/video/bttv.o: insmod bttv failed
Nov  4 12:49:51 mythtv modprobe: modprobe: Can't locate module rivatv

Not too sure why the system is trying to load bttv when these are PVR-250's.

Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module 
char-major-10-134
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb0
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb1
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb2
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb3
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb4
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb5
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb6
Nov  4 12:49:53 mythtv modprobe: modprobe: Can't locate module fb7
Nov  4 12:49:54 mythtv kernel: ivtv: ivtv-api.c: unknown ioctl 0x803c7601
Nov  4 12:49:54 mythtv kernel: ivtv: ivtv-api.c: unknown ioctl 0x803c7601
Nov  4 12:49:54 mythtv modprobe: modprobe: Can't locate module char-major-81-2

The fbx errors are expected from what I've read since I don't have a 
PVR-250.  I'm not too sure what ivtv-api.c error is all about.

Here's a snippet from /etc/modules.conf if it helps.  I tried doubling the 
default size of all the buffers but that doesn't seem to help.

alias char-major-81     videodev
alias char-major-81-0   ivtv
alias char-major-81-1   ivtv
alias char-major-61 lirc_i2c
options ivtv tuner=2 yuv_buffers=120 mpg_buffers=60 vbi_buffers=20 
num_devices=2 dec_mpg_buffers=16 dec_yuv_buffers=70 dec_mpg_qlen=
4 dec_yuv_qlen=15 ivtv_debug=1
options tuner type=2
options msp3400 once=1 simple=1
add below ivtv msp3400 saa7115 tuner
add above ivtv lirc_dev lirc_i2c

top shows the system running with idle in the high 90's... ie, 99% 
idle.  I'm sure this system has enough horsepower to do the job.  Any 
suggestions?

Gary

At 02:01 am 03/11/2003, you wrote:
>Hi guys,
>
>Been working on this all night and making absolutely no progress.  It's 
>2am so I thought I'd bounce it off you guys and try some more tomorrow.
>
>MythTV 0.12
>Latest IVTV CVS tarball
>ALSA 0.9.8
>RedHat Linux 9
>
>Asus Pundit 2.4GHz/512MB/120GB/2xPVR250
>
>My problems started when I attempted to upgrade IVTV in order to get some 
>better quality out of my cable line.  The upgrade seemed to have worked 
>just fine BUT I started noticing dropped frames... very noticeable!  Whole 
>chunks of the stream appeared to have been chopped right out.  In any 
>case, /var/log/messages logs the following errors continuously while 
>recording.  The CPU is sitting at almost 99% idle and there is no paging 
>during this time yet I still log buffer errors.
>
>...
>Nov  3 01:51:02 mythtv kernel: ivtv: Nov  3 01:51:02 mythtv kernel: ivtv: 
>DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: full_q: 100 elements got 1, want 1
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:02 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:20 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:38 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:51:56 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:52:15 mythtv kernel: ivtv: DEC: full_q: 100 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DMA buffer DeQueue failed! got 1, want 1
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: free_q: 0 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: dma_q: 0 elements
>Nov  3 01:52:33 mythtv kernel: ivtv: DEC: full_q: 100 elements
>...
>
>Has anyone ever seen this?  No luck googling these errors.  Not too sure 
>if this is something I should take up on the IVTV list or not.
>
>Thanks.
>
>Gary Raposo                                              gary at raposo.ca
>Eschew obfuscation...                              http://www.raposo.ca
>
>
>
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Gary Raposo                                              gary at raposo.ca
Eschew obfuscation...                              http://www.raposo.ca

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