[mythtv-users] Stop transcode/commflag from hogging the CPU while recording/playback is in progress

Sam Varshavchik mrsam at courier-mta.com
Tue May 9 20:56:43 EDT 2006

I'm using the following patch to make myth behave much better on my test 
box, which is comparatively low-powered.  My test box is a dual Celeron 500 
(!). Yup, it's pretty old, but it's still has plenty of kick left in it, and 
it's got enough juice to run LiveTV out of my PVR-350's TV-Out.  I'm using 
the xorg ivtv PVR-350 framebuffer module, to run xorg -- and mythfrontend -- 
on the PVR-350's TV-Out framebuffer.

I think someone told me a few weeks ago that this couldn't be done -- 
simultaneously recording off the PVR-350, and playing back through its 
TV-Out plug -- but it definitely works: I can definitely watch Live TV, 
which is essentially a simultaneous record and playback operation.

I came up with the following patch when I ran into a minor glitch when I 
queued up two consecutive programs to be recorded, after the other.

What happens is that after the first recording finishes, the backend begins 
recording the second program.  Meanwhile, commflag cranks up, begins 
scanning the first recording for commercial breaks, pegging both I/O and 
CPU, and generally messing up the second recording, which is already in 

The following patch makes mythtranscode and mythcommflag automatically wait 
if something is currently being recorded or played back.  When the current 
recording or playback stops, mythtranscode/mythcommflag picks up where it 
halted. In my scenario, the first mythcommflag job patiently waits until the 
second recording is done, then chews through the first recording; then the 
second mythcommflag job runs and does the second recording.

While I'm thinking about whether or not let mythtranscode or mythcommflag 
continue to run, but with judicious pauses, I've uploaded the patch anyway, 
hopefully others might also find it useful: 

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