[gst-devel] Mixing pipeline

Ross Burton ross at burtonini.com
Tue Dec 14 05:48:01 CET 2004


I'm trying to create a small application which mixes two sources
together, where one source is shorter than the other and starts at an
arbitrary time in the stream.  However, this is causing problems.

The basic pipeline:

gst-launch adder name=a ! alsasink
  { filesrc location=foo.wav ! spider ! queue ! a. }
  { filesrc location=bar.wav ! spider ! queue ! a. }

does the mixing correctly but stops playing when the first source fires
EOS.  Thomas (IIRC) has said this is probably a bug, would the bug be in
gstreamer core, adder, or gst-launch (and thus a custom application
could work around it).  Also, when all sources have fired EOS the
pipeline doesn't EOS, so gst-launch never returns.  I believe this is a
design decision of the adder element, so I presume my app would  need to
monitor the sources and when they have all fired EOS I close the
pipeline myself.

(Note that http://bugzilla.gnome.org/show_bug.cgi?id=161179 already
contains comments on adder bugs from Ronald)

The second problem is adding new elements to a pipeline whilst it is
running.  I've a small python script which creates the above pipeline
but adds one of the threads into the pipeline and links it up mid-play
(with a callback on the iterate signal).  This crashes the application
in grand style, which may or may not be related to the bugs in #161179.
Should this work?

Thanks for any assistance, this was meant to be a quick project but is
rapidly looking like my True Enemy.

Ross Burton                                 mail: ross at burtonini.com
                                          jabber: ross at burtonini.com
                                     www: http://www.burtonini.com./
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