[mythtv-users] Recorded material stutters, live TV is perfect. Why?

[Michael T. Dean]

On 05/02/2008 01:42 PM, Mark Knecht wrote:

>  On Fri, May 2, 2008 at 10:38 AM, Michael T. Dean wrote:
>
> > On 05/02/2008 01:16 PM, Brian Wood wrote:
> >
> >> On May 2, 2008, at 11:05 AM, Mark Boyum wrote:
> >>
> >>> You haven't indicated what type of material you are recording /
> >>>  playing.  Assuming it is SD, I would say that even at 20% your
> >>>  system should be able to perform decent playback.  I would
> >>> suspect the problem is related to using a wireless network.
> >>> Just to test, try connecting that frontend via Cat5.
> >>
> >> Following this thread I'd missed that you were using a wireless
> >> network. I agree that is almost certainly at least part of your
> >> problem.
> >
> > And the 20% CPU is probably due to the rebuffering which is due to
> > the stuttering which is due to the data transfer issues.  I.e. the
> > jump from 12% to 20% CPU is not causing the issue, but a symptom of
> > it.  That's also why it doesn't stabilize after reducing the speed
> > back to real-time (because it's still stuttering...).
>
>  Ah, interesting thought. I was going a different direction with it. I
>  noticed that the jump to 20% happens even when I slow down playback
>  first. I was thinking that whatever the software component is that
>  does the building of frames for different speeds might need updates
>  in Gentoo. Maybe I'm using the wrong flags. Is that software part of
>  Myth proper or is it a library that Myth calls like fftw or
>  something?

The timestretch code in Myth is an integrated version of a standard 
library (i.e. no need to update anything).

Note, however, that 0.21 has some code which attempts to set the 
read-buffer size appropriately "on the fly."  I.e. if it starts to 
stutter, it attempts to increase the buffer size.  The code isn't 
perfect and tends to have serious issues in less-than-ideal (read 
wireless) network conditions.

You're typically better off letting the backend stream the recordings 
rather than using NFS or CIFS or whatever when you're having these 
issues.  If you want to work on fixing the code, I think Stuart A. had 
some ideas.

Fix the network, fix the playback.  (Think Heroes season 1.)

Mike