[mythtv] Re: mythtv-dev Digest, Vol 1, Issue 314
jcoiner at stanfordalumni.org
Tue Jan 21 22:41:08 EST 2003
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
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'
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
If your playback thread measures okay, you might be dropping frames in
the recorder. But that's less likely.
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