[mythtv] Random blockiness that probably isn't CPU or PCI bus bandwidth-related

Kyle Rose krose+mythtv at krose.org
Mon Jan 10 01:37:37 EST 2005


Short version: I ditched the single frontend/backend dealie and
replaced it with a separate 3.2 P4 HT frontend and Athlon 1800 333 FSB
backend.  Now, when recording HDTV (HD-2000) concurrently with a
recording from one of my ivtv cards, I get intermittent blockiness on
the HDTV stream.

Thing is, I get no bttv: buffer overrun errors, except during the
times I expect them (e.g., another recording starting).  This suggests
the driver is getting the data correctly, but it is being ditched or
overwritten before mythtv gets it.  Does this jive with the
understanding of some of the HDTV developers here?  (Daniel?  John?)

What should my next step be here?  I haven't kept close track of the
current state of the art in HDTV ringbuffers as it changed a lot in a
short period of time; is there a separate thread that can be set with
RT/FIFO priority in order to stop this problem?  If the ringbuffer
size is static, how can I adjust it; if it's dynamic, how does it
behave?

Thanks,
Kyle


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