[mythtv] Buffer Time stamps
Andrew Kimpton
awk at awkward.org
Sat Aug 12 12:34:45 UTC 2006
I'm working out some kinks in adding Plextor Convert-X support to the
backend on Mac OS X. I can transfer video and and audio fine from the
device (and initialize it, do channel changes etc). But...
I'm getting exceedingly 'glitchy' (stuttering) audio playback and a
lot of :
NVP: Prebuffer wait timed out 10 times
messages from the frontend.
I know that my machine is not overloaded (I can use Shark on Mac OS X
to see that between them the frontend and backend only use 65% of the
CPU on my machine). So I think something must be going wrong with the
time stamps being placed on the buffers in NVR::BufferIt and from the
NVR::doAudioThread. Can someone give me a brief synopsis on how this
is supposed to work, and also what the player side does with the time
stamps.
What I'm doing closely follows the existing GO7007/V4L2 code -
BufferIt applies TimeStamps based on 'now' (I've not changed BufferIt
at all) and my doAudioThread (which is new) timestamps the received
USB buffers using the same mechanism as the existing GO7007/V4L2 code.
Also there's probably a better way on Mac OS X to get timing
information than calling gettimeofday - however I'd like to
understand the expected resolution and units of the timing info. It
looks like the buffers are stamped with a delta in milliseconds since
the NVR thread started - is it that simple ?
Thanks
Andrew 8-)
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