[mythtv] Audio problems

Neil Whelchel koyama at firstlight.net
Sat Aug 28 06:43:52 EDT 2004

On Sat, 28 Aug 2004, Ed Wildgoose wrote:

> Neil Whelchel wrote:
> >Hello,
> >Seems like an audio problem with the latest CVS copy of mythtv using ALSA.
> >Some (possibly corrupted) video files produce the following error:
> >
> >Audio buffer overflow, audio data lost![] afree=0 need=4096
> >
> >
> Is the audio out of sync with the video at this point? ie before it
> overflows?
> The error basically means that the audio is somehow getting ahead of the
> video, but not sure how it has happened if you are clock the video to
> the audio...
> Adding some debug statements to the audio code and main loop will
> quickly bring you up to speed on how this bit works
> Ed W

There doesn't seem to be an A/V sync problem associated with this issue.
However, I have concluded that the cause is definitely a corrupted file as
the problem is completely re-producible at the exact locations in the
files. I also noticed a few missing video frames right at the
point that the messages are produced.

It seems that the cause of the corrupted files is that I am running NFS for
everything to a central file server. At some point during recording from
one of the back-end boxes the file server becomes overloaded and is unable
to keep up with writing the data to the disk, leaving a few missing bytes,
blocks or whatever within the file.

I can understand this causing problems or momentary loss of audio or
video, but it should not cause the audio playback to fall into a failure
state, so therefor this is surely a bug. ;)

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