Hi,
Some precisions about python and gstreamer. As Rene
mentionned,
Python "virtually" handles multi-threaded
applications (like a
gstreamer-based one), but the Python VM can only be executed
by ONE
thread at a time. This is what the GIL (Global Interpreter
Lock) is
for.
This is why, in the gst-python bindings, we release the
GIL whenever
we call C code from Python and reaquire it when we return
from that C
call. In the same way, whenever in some C callbacks we call
some
Python call we aquire the GIL and release it once we have
stopped
calling the Python part.
The GIL protects data which is common to the Python VM as
a whole
(one python VM per process, which may include several
threads).
From my understanding, your env variable is common to the
JAVA VM
(only one per process), therefore you need to do something
similar to
what we do in gst-python with the GIL.
Hope this helps.
Edward
P.S. On a side note, I thought Java didn't have the issue
Python has
with multi-threading ... so maybe this is not needed and
Java already
provides you with a thread-safe way to access those global
values.
On 1/17/07, René Stadler <mail renestadler.de> wrote:
> Am Dienstag, den 16.01.2007, 20:12 +0100 schrieb
Patrick Holthaus:
> > Hey!
> >
> > > The chain function is executed in the
streaming thread. Could this be
> > > the problem here? If I understand this
correctly, you are calling into
> > > the Java intepreter or something. Maybe it
doesn't like that if the
> > > call is coming from a thread it doesn't know
about.
> >
> > This might be the reason. I have read that the env
pointer is not valid in
> > another thread. But how could i change it to use
the thread that is created
> > by the Java VM? (The jmf_GSTDataSource.c file)
> >
> > Greets
> > Patrick
>
> You can't, the processing is driven by GStreamer-owned
threads. You
> need some form of synchronization. E.g. for Python,
one needs to grab
> the GIL (global interpreter lock).
>
> --
> Regards,
> René Stadler
>
>
>
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--
Edward Hervey
Multimedia editing developer / Fluendo S.A.
http://www.pitivi.org/
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