[mythtv-users] Performance issues with version 0.21_pre15014
hakon at alstadheim.priv.no
Sat Dec 22 23:00:02 UTC 2007
I'm running myth on gentoo, currently at mythtv 0.21_pre15014, which
gets pulled from svn. I recently upgraded from 0.20.<something> in
preparation of working on dvb-t reception issues. I haven't got to that
yet, because getting up and running with my old analog channels has
Myth has frequently been maxing out my cpu, also before the upgrade.
Cpuinfo says I have a "Intel(R) Pentium(R) 4 CPU 2.00GHz", with ~70%
going to recording to MPEG4 (simple Haupaugue card) and ~30% to
playback. Very occasionally I had lost video frames before the upgrade.
Totally watchable and better total user-experience than xdtv.
After the upgrade both the backend and the frontend occasionaly want
>80% of the cpu. As I have a single core, this means something has to
give. Now, the interesting thing is that just recording (without
watching) in myth, and playing back the recording in vlc AS IT IS BEING
RECORDED, works ok, with vlc taking 20-40% and mythbackend the rest (a
tiny bit is going to X and other things like mysql, same as when running
myth FE/BE). Some dropped video-frames, but the sound is rock solid, no
glitches. Myth on the other hand, when anything appears, will frequently
skip entire sections of sound and video, making it impossible to
understand what is going.
This thing with extreme cpu use does not happen always. The sure way to
get nothing on the screen is to start watching a channel with a noisy
signal (hard to compress), although even there I got OK performance once
quite recently. What happened was that when the first frame finally
appeared (after ~30 seconds), and I tried changing channels and then
hitting escape, the keyboard became totally unresponsive, and the video
started running quite smoothly.
This is with the "CPU+" playback profile. "CPU-" invariably gives no
output (screen and sound) or just some mpeg artefacts (colored squares
on the screen or something such), never more than one frame (I've tried
waiting for one hour at least once).
I've tried recompiling ffmpeg and mpeg libraries, unmasking testing
versions, but that does not help. Still, recording with myth and
watching AT THE SAME TIME in vlc, is just dandy. What should I try? The
options I see right now is switching to xdtv (no recordings), or
downgrading. Spending two hours hacking the database to downgrade seems
very unproductive, but do I have a choice ?
More information about the mythtv-users