[mythtv-users] HDTV digital static with DVB

Preston Crow pc-mythtv05b at crowcastle.net
Tue Nov 8 20:35:04 EST 2005


On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
> I chased video glitches from my DVB setup for ages, and with a lot of 
> help from the list, I finally nailed it.  It was the Si 3112  SATA 
> controller chip doing nasties on the PCI bus and corrupting the mpeg 
> stream from the DVB card.
> 
> This would correlate with your observation that it is worse with system 
> load, in particular disk access.

I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
file on the SATA drive, I get some glitches.  If I do the same to a file
on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
get a perfect recording.

So it doesn't look like it's the SATA chipset doing something nasty.  In
fact, the SATA drive, being on a faster bus, gives me a better recording
than the PATA drive.  This makes it look more like my original theory of
being an issue that can be solved in the DVB driver.  Of course, it
could be the SATA chipset or anything else on the PCI bus, but if
something were corrupting the DVB traffic, wouldn't it also corrupt
other traffic, like disk I/O?

Instead of it being a kernel buffer that is too small, perhaps it is too
slow to pull the data off of the card?

--PC



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