Multiple pipelines in an application

[Hannes Weisbach]

Hello,

I'm writing an application which handles two video streams from USB
video class devices, which runs on the Raspberry Pi.  The cameras
stream H.264.  The application needs to store a high-quality version
locally on disk (using filesink).  Additionally a downscaled, lower
quality RTP stream should be provided.  Decompression and compression
is done using the Raspberry's hardware acceleration (with gst-omx).  I
have implemented the streams using qt-gstreamer.

Right now my application has two pipelines, one for each camera
stream.  Occasionally, the program crashes, around the time the second
pipeline goes into playing state.

After a bit of googling I found an old message from this list [0],
saying that multiple pipelines in one application are not easily
doable.  I was wondering if that limitation still applies, or if I
have a bug somewhere else.

Launching my application in gdb lets the segfault trigger even less
often, suggesting some kind of race condition.  When I caught a crash
in gdb, the crashing function was reported as video_orc_unpack_I420.
However, the function was called with broken parameters (way too large
n), so the cause might be elsewhere.  Also the stack seemed to be
corrupted.

Anyway, I had no problems running just one pipeline in my application,
so I'd appreciate a comment on whether its possible/advisable to have
multiple pipelines in an application or if I should refactor to have
only one pipeline (and possible start two instances of the
application).

Thank you for your time,
with best regards,
Hannes Weisbach

[0] http://lists.freedesktop.org/archives/gstreamer-devel/2006-June/012599.html