[mythtv-users] playback issue with mythbackend going cpu bound causing playback issue, and one use local access, another uses myth://

Roger Heflin rogerheflin at gmail.com
Fri Jul 1 00:01:50 UTC 2011


I have a separate backend w/2 frontends.

One frontend works fine and does not use remote file transfer, the 
other frontend uses remote file transfer when doing playback, on some 
videos this causes excessively high network loads and high cpus loads 
on the backend (note network is wired Gbit) on some transcoded files 
(transcoded to SD) in these cases I can copy back the un-transcoded 
1080i original and play it just fine, and it has a much higher bitrate 
that the transcoded content that is not working, so something odd is 
going on.   Also, all of my stuff is trancoded to the same format and 
only some transcoded recording have these issues.

What is causing one frontend to use remote file vs local?   both 
frontends have the storage location mounted via nfs in the exact same 
directory as is on the actual backend.  One shows 
ringbuf(localfilename) the other shows RingBuf(myth://192.168.), so 
there has to be something configured for one to use local vs myth:, 
but looking through the menus I don't find anything that looks like it 
would control this.

And any ideas what is causing the backend behavior?   On the same 
frontend a working video produces a network rate of about 
450Kbyte/second (about right for bitrate), the non-working video 
produces an IO rate of about 12.5MByte per second.   I have confirmed 
that both the frontend and backend are connected with properly working 
gigabit, on the bad videos mythbackend on the backend maxes out the 
cpu attempting to send out this excessive network traffic, as soon as 
the video is stopped the traffic goes away, on the good videos the cpu 
usage is reasonable.   The other frontend appears to work because it 
is not using remote file transfer.

Vidoes play just fine using nfs with mplayer on the frontend having 
the issues, I suspect it will play just fine on that frontend if I can 
get it to not use remote file transfer bypassing whatever is going on 
when the backend server streams the data.


More information about the mythtv-users mailing list