[linux-dvb] buffer underruns with budget-av/-ci (vpeirq)

Matthias Dahl mldvb at mortal-soul.de
Sun Oct 15 17:04:48 CEST 2006


I know its bad practice to reply to oneself, nevertheless I wanted to add more 
information to this: having just switched over to 2.6.19rc2, the problem has 
gotten worse. Now every single X <-> VT switch results in a...

saa7146 (0) vpeirq: used 1 times >80% of buffer (65612 bytes now)

... msg. Sometimes I get corruptions in the mpeg stream because of this and 
sometimes it's just fine. Even during normal playback of a stream, those msgs 
appear without any load on the machine. (with 2.6.19rc2 that is)

Is there anything I can do to get to the bottom of this?

Thanks a lot in advance.

On Saturday 14 October 2006 16:27, Matthias Dahl wrote:
> Hi everyone.
> 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
> occurred:
> 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 66) (0x1894,0x0021).
> 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
> ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff
> 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
> successfully
> 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
> successfully
> 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,
> matthew.

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