Saturday, 10 November 2012

mythtv 0 byte recordings

there seems to be a problem going around where mythtv is failing to record shows (on DVB tuners) and recording that the show HAS been recorded, but with a zero byte file size.

I have had this happen on my machine, which is currently running mythbuntu 12.10 64 bit.

When it happens on my machine, further recordings and live tv all fail too.
A quick google gives me the following impression.

  1. This seems to happen when folks have multiple DVB tuners.
  2. setting "quick tuning" to always may help.
  3. altering the vmalloc of your kernel may give the DVB cards more headroom? (perhaps multiple tuners, along with nvidia graphics blobs can quickly use up the default 128M?)

so, as I am in category 1, I have tried fixes 2 and 3. incidentally, fix 3 should be done in this manner for most grub2 based distros.

sudo nano /etc/default/grub
change the line which looks this (you may have other options already like splash)
GRUB_CMDLINE_LINUX_DEFAULT="quiet" 
by appending vmalloc=512M ie..
GRUB_CMDLINE_LINUX_DEFAULT="quiet vmalloc=512M" 
then save & run
"sudo update-grub"

I've done this.. I'll let you know if it doesn't work (might be 2 weeks before the next program is missed, and I'll bet it is my wife's favourite gardening program again)

2 comments:

Neil said...

seems to be working so far. my hunch is the vmalloc change is "what done it"!

Tony Whitmore said...

Thanks for the post Neil. I was having a similar problem. Only one tuner but setting the fast tuning to "always" seems to have fixed it. For now...