MythTV frontend rebuffering problem

Brandon Beattie brandon+plug at beatties.us
Wed Aug 30 15:28:15 MDT 2006


On Wed, Aug 30, 2006 at 03:09:45PM -0600, Andrew Jorgensen wrote:
> On 8/30/06, Roberto Mello <rmello at fslc.usu.edu> wrote:
> >The problem seems to be specifically on the transmission of data. I don't
> >the computer can't process the stream fast enough, otherwise mplayer
> >playing those very same files over the NFS share would be just as choppy.
> 
> Actually mplayer is pretty clever.  Not that myth isn't but mplayer
> uses a longer cache and has some really good decode algorithms.  But
> now that I mention that I think they both use ffmpeg for mpeg4 (or are
> you using rtjpeg? or mpeg2?).
> 
> Anyway, the longer cache that mplayer uses could mask a problem with
> your network.  You could have one side configured full-duplex and the
> other side half-duplex for instance.
> 
> >It seems to be something strictly related to the way the myth protocol 
> >works.

Myth keeps a very small buffer for several reasons, but it's not worth
going into and it's not something you can tweak minus hacking the code.
Now I've also seen problems with some switches and network cards.  My
gigabit switch will cause prebuffering pauses all the time, but my
10/100 switch won't.  I know some network cards need to be throttled so
it doesn't starve the system when it gets bursts of large data packets.
Next question is why are you using nfs? Myth has it's own protocol.
Maybe you're not using nfs for myth, but you did bring it up.  There are
also some nfs tweaks (read myth-users mail web archive).  But it is true
mplayer is a _lot_ more forgiving for network hicups than myth is.  You
can always try a transfer and see how much throughput you get, and how
stable it is.

--Brandon



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