[Bug 635256] alsasrc: suggestion for improvement of timestamping accuracy for alsa (and others) sound

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=635256
  GStreamer | gst-plugins-base | 0.10.x

--- Comment #39 from Pontus Oldberg <pontus.oldberg at invector.se> 2012-01-02 13:07:40 UTC ---
I have spent some time looking into this the past weeks and have come up with a
fix that is a bit more extensive than the previous one.

Note, that it still is a experimental version, but I thought it would be good
to have it here for further discussion.

Basically this suggestion introduces a new property (in the audiosrc element)
that tells the system to run the alsasrc in a single thread instead of having a
separate read thread and the pipeline thread. Time stamps are now taken in the
same thread as data is read which solves the problem of having reads and taking
the timestamps unsynchronized.

As I understand it, having a separate read thread solves the problem were
poorly written alsa drivers would loose data if not served instantly when new
data is available. This is why the read thread wasn't removed completely.

This implementation starts up with dual threaded alsasrc as default, and by
setting the "single-thread" property to true it goes into a single-thread mode
of operation. Driver timestamping is also disabled in dual thread mode since it
does not work properly, as discussed before.

Comments, suggestions anyone ?

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