RE: gstreamermm, Gst::AudioSink and virtual functions


      Thanks for your help so far. I’ve made some progress but I’m still stuck.

I am still trying to create a ‘do nothing’ audiosink upon which I can build.

Is there a clear statement somewhere of what an C++ audiosink class must provide?

I was able to create a a ‘do nothing’ sink using “gst-element-maker mydemosink audiosink”

which seems to work but there is nothing obvious to translate from that code into the C++ version.


The latest output is:


(gst-launch-1.0:16830): GStreamer-CRITICAL **: gst_object_set_parent: assertion 'GST_IS_OBJECT (object)' failed


** (gst-launch-1.0:16830): CRITICAL **: gst_audio_ring_buffer_open_device: assertion 'GST_IS_AUDIO_RING_BUFFER (buf)' failed


(gst-launch-1.0:16830): GStreamer-CRITICAL **: gst_object_unparent: assertion 'GST_IS_OBJECT (object)' failed

ERROR: Pipeline doesn't want to pause.


I thought the ring buffer was provided by the parent class AudioBaseSink  but it seems not.


Note for testing this I’m using:


   gst-launch-1.0 -v audiotestsrc blocksize=8000 num-buffers=10 ! audio/x-raw,rate=8000,channels=1 ! myaudiosink


The simplest MyAudioSink.hpp to reproduce this:


#include <gstreamermm.h>

#include <gstreamermm/audiosink.h>


class MyAudioSink: public Gst::AudioSink                     



   explicit MyAudioSink(Gst::AudioSink::BaseObjectType* gobj):

      Glib::ObjectBase(typeid (MyAudioSink)), // type must be registered before use





   virtual ~MyAudioSink()




   static void class_init(Gst::ElementClass<MyAudioSink> *klass)



                          "Sink/Audio", "A test audio sink", "author");

      klass->add_pad_template(Gst::PadTemplate::create("sink", Gst::PAD_SINK, Gst::PAD_ALWAYS,






A C++ myaudiofilter derived from AudioFilter on the other hand seems to just work:


gst-launch-1.0 audiotestsrc blocksize=8000 num-buffers=10 ! audio/x-raw,rate=8000,channels=1 ! myaudiofilter ! fakesink


Calling create_ring_buffer() in the constructor MyAudioSink causes a seg fault:


(gst-inspect-1.0:23564): GStreamer-CRITICAL **: gst_object_set_parent: assertion 'GST_IS_OBJECT (object)' failed


(gst-inspect-1.0:23564): GLib-GObject-CRITICAL **: g_object_get_qdata: assertion 'G_IS_OBJECT (object)' failed


(gst-inspect-1.0:23564): GLib-GObject-CRITICAL **: g_object_get_qdata: assertion 'G_IS_OBJECT (object)' failed

Segmentation fault (core dumped)


#3  fault_handler_sighandler (signum=11) at gst-launch.c:94

#4  <signal handler called>

#5  0x00007eff8272b898 in Glib::wrap_auto(_GObject*, bool) () from /usr/lib/x86_64-linux-gnu/

#6  0x00007eff82df5bcf in Glib::wrap(_GstAudioRingBuffer*, bool) () from /usr/lib/x86_64-linux-gnu/

#7  0x00007eff82df16c6 in Gst::AudioBaseSink::create_ring_buffer() () from /usr/lib/x86_64-linux-gnu/

#8  0x00007eff830f5eb4 in MyAudioSink::MyAudioSink


I tried putting it in some of the vfunc’s like open, reset , write and start instead but none of them are invoked before it starts asserting.


Its not immediately obvious where to set a breakpoint to try and track this down

I’m wading through glib and gstreamer source trying to find out without much success so far.

Any tips would be appreciated.





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