[linux-dvb] buffer underruns with budget-av/-ci (vpeirq)
mldvb at mortal-soul.de
Sat Oct 14 16:27:12 CEST 2006
I own a KNC ONE DVB Plus with a Cineview module (Alphacrypt Light). From the
beginning I ran into data corruption problems with the mpeg stream as soon as
I made the usual X <-> VT switch or put some load on the Athlon64 3500+
machine with its RAID 5 (3 SATA disks).
After some looking around, I soon discovered it was related to a buffer
underrun because the following showed up in my logs every time a corruption
saa7146 (0) vpeirq: used 1 times >80% of buffer (65612 bytes now)
I searched the mailing list archives and learned this problem had been
reported earlier and that I should increase the DMA buffer size- which I did.
Running now at the maximum of 1410kb, things have pretty much been fixed. I
can put load on the machine, do random X <-> VT switches and everything works
most of the time. But there still is the occasional underrun even though the
machine is not under load.
For example, I am running mythtv on my box for scheduling recordings. From
time to time, I get 3-4 underrun msgs in a short time (a matter of minutes),
even though nothing is recording and the machine is far from being loaded. I
don't know what mythtvbackend is doing then (maybe checking for EPG updates
from time to time).
Here the relevant parts of my log when the dvb modules are being loaded:
Oct 14 09:19:22 saa7146: found saa7146 @ mem ffffc20000014000 (revision 1, irq
Oct 14 09:19:22 saa7146 (0): dma buffer size 1443840
Oct 14 09:19:22 DVB: registering new adapter (KNC1 DVB-C Plus).
Oct 14 09:19:22 adapter failed MAC signature check
Oct 14 09:19:22 encoded MAC from EEPROM was
Oct 14 09:19:22 saa7146_vv: saa7146 (0): registered device video0 [v4l2]
Oct 14 09:19:22 KNC1-0: MAC addr = 00:09:d6:6d:61:b5
Oct 14 09:19:22 DVB: registering frontend 0 (Philips TDA10021 DVB-C)...
Oct 14 09:19:22 budget-av: ci interface initialised.
Oct 14 09:19:22 budget-av: cam inserted A
Oct 14 09:19:22 dvb_ca adapter 0: DVB CAM detected and initialised
Oct 14 09:19:22 saa7146: register extension 'budget_ci dvb'.
Oct 14 09:19:35 budget-av: cam inserted A
Oct 14 09:19:36 dvb_ca adapter 0: DVB CAM detected and initialised
If there is anything I can do to help fix or investigate this, please let me
know. I am more than willing to help...
Have a nice weekend and thanks for any help in advance,
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