[mythtv] Re: mythtv-dev Digest, Vol 1, Issue 314

[John Coiner]

John Joseph Roets <jjr at sunflower.com> wrote:
> Hello all.
> I'm running Myth and getting jerky/jittery video.
> Video is jittery to very jittery in live TV mode (and sometimes, in
> playback mode). 

That box should be fast enough. I haven't checked out CVS in a while, 
but stock 0.7 had low jitter, generally unnoticeable.

Try building a kernel with power management entirely disabled, and see 
if that makes a difference. My myth box is okay with APM support 
compiled in, but it does strange jittery things if I compile in ACPI 
support...

If you want to play with the code, there is a 'jitterometer' class in 
the libNuppelVideo/ directory. There is some code in the player, which 
is commented out, that instantiates a jitterometer (search for 'jmeter' 
in NuppelVideoPlayer.cpp)

Every 100 cycles, the jitterometer calculates the standard deviation of 
the cycle times, and prints this information out. It usually measures 
about 5ms of jitter on the playback thread, measured right after the 
call to videoOutput->Show() returns. (... and usually the jitter is not 
noticeable, even during fast action programming, like baseball or auto 
racing.)

If your playback thread measures okay, you might be dropping frames in 
the recorder. But that's less likely.

-- john