can't insert custom audio filter into libvlc pipeline

[dsurvi]

Hello,

I am building a custom audio filter I want to use inside a program written in c using libvlc. I downloaded and compiled vlc 2.2.8 and my filter on ubuntu and after launching vlc everything works fine, filter gets loaded in the pipeline and does its job. But when in my c program, when calling using libvlc api I can't insert my filter into the audio pipeline. I verify this by using verbose=2 and my filter never gets loaded. Piece of code I use for instantiation of libvlc:
const char * const vlc_args[] =
{
"--verbose=2",
"--audio-filter=vibbro"
};
inst = libvlc_new (sizeof(vlc_args)/sizeof(vlc_args[0]), vlc_args);

This happens even if calling libvlc_audio_filter_list_get lists my filter among the available ones.
Can you point what I'm doing wrong or any way to insert my filter into the pipeline? My filter is build using gain.c as model. The fact is that I can't also insert gain into the pipeline.

Thank you