Hi,
When using the dmix plugin to mix sounds for multiple apps, mplayer
performance is poor. (video slows down and speeds up a few times a
second)
This is due to tracking issues between the sound and the video --
mplayer is unable to get accurate delay info from the sound driver and
so keeps thinking the sound is out of sync.
>From the man page I have found this help for mplayer:
-autosync <factor> Gradually adjusts the A/V sync based on audio
delay measurements. Specifying -autosync 0, the
default, will cause frame timing to be based entirely on
audio delay measurements. Specifying -autosync 1 will
do the same, but will subtly change the A/V correction
algorithm. An uneven video framerate in a movie which
plays fine with -nosound can often be helped by setting
this to an integer value greater than 1. The higher the
value, the closer the timing will be to -nosound. Try
-autosync 30 to smooth out problems with sound drivers
which do not implement a perfect audio delay
measurement. With this value, if large A/V sync offsets
occur, they will only take about 1 or 2 seconds to
settle out. This delay in reaction time to sudden A/V
offsets should be the only side-effect of turning this
option on, for all sound drivers.
So the problem goes away if I set -autosync 30 or so. The sideeffect
being that sound syncing will be more gradual if it is ever required.
Has anyone else had the same problem?
In particular:
-autosync 30 to smooth out problems with sound drivers
which do not implement a perfect audio delay
measurement.
I find that this only happens when the dmix mixer is being used -- is
there a problem with audio delay measurements in the dmix driver? if
so is there a fix or a workaround that I can implement by changing
ALSA settings?
Thanks,
Nick
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