It should not be required.

Thank you for your feedback. I was not sure if this was indeed a bug or the expected behavior. I had to do this in my machines and the users of my application too as you can see in these issues:

https://github.com/wwmm/pulseeffects/issues/142
https://github.com/wwmm/pulseeffects/issues/136

Is there any more info I should provide?

I don't think any extra information will be needed, we need someone to look at it now and reproduce.

How it works is that GST lv2 plugin should register each lv2 plugins and plugins directory. These will be added into the registry cache and looked up for update. The only downside is that you need not to reset back file timestamp in your package manager. So far this only happens with ostree/atomic. I don't think it's you case. Mostly newly added files need to be newer then the cache.

I have fixed this in frei0r a while ago, we need to look into lv2 to find out what it does and why it does not work. Then we should check ladspa, as lv2 is based on it.

Did a quick try, which seems like needed, but it does not seem to fully fix the issues:

> diff --git a/ext/lv2/gstlv2.c b/ext/lv2/gstlv2.c
> index 2c8253dc8..181f3ca5f 100644
> --- a/ext/lv2/gstlv2.c
> +++ b/ext/lv2/gstlv2.c
> @@ -255,7 +255,8 @@ plugin_init (GstPlugin * plugin)
>    side_right_role = lilv_new_uri (world, LV2_PORT_GROUPS__sideRight);
>  
>    gst_plugin_add_dependency_simple (plugin,
> -      "LV2_PATH", GST_LV2_DEFAULT_PATH, NULL, > GST_PLUGIN_DEPENDENCY_FLAG_NONE);
> +      "LV2_PATH", GST_LV2_DEFAULT_PATH, NULL,
> +      GST_PLUGIN_DEPENDENCY_FLAG_RECURSE);
>  
>    /* ensure GstAudioChannelPosition type is registered */
>    if (!gst_audio_channel_position_get_type ())


I've removed a plugin, and then the plugin didn't go away and inspecting that plugin caused a crash. But I confirm it's totally buggy.

So lilv also implement a cache, can clearly removing a plugin folder didn't trigger that cache to be updated. So yet, gst need some help, but apparently lilv cache is not better.

Correction, my patch work, it's the path that is broken. Instead of reading the libdir from the lilv2 pkconfig, it gets the meson configure time libdir. That's fails for my case because I installed git master gstreamer in a prefix, while lilv has libdir=/usr/lib64/lv2 which is not included in the path.

Ok, here's what we need to reproduce (Heiku OS excluded):

    # Set default LV2 path
    lv2_path = Options.options.default_lv2_path
    if lv2_path == '':
        if conf.env.DEST_OS == 'darwin':
            lv2_path = lilv_path_sep.join(['~/Library/Audio/Plug-Ins/LV2',
                                           '~/.lv2',
                                           '/usr/local/lib/lv2',
                                           '/usr/lib/lv2',
                                           '/Library/Audio/Plug-Ins/LV2'])
        elif conf.env.DEST_OS == 'haiku':
            lv2_path = lilv_path_sep.join(['~/.lv2',
                                           '/boot/common/add-ons/lv2'])
        elif conf.env.DEST_OS == 'win32':
            lv2_path = lilv_path_sep.join(['%APPDATA%\\\\LV2',
                                           '%COMMONPROGRAMFILES%\\\\LV2'])
        else:
            libdirname = os.path.basename(conf.env.LIBDIR)
            lv2_path = lilv_path_sep.join(['~/.lv2',
                                           '/usr/%s/lv2' % libdirname,
                                           '/usr/local/%s/lv2' % libdirname])

That explain why you cannot install both 32bit and 64bit plugin on Debian, they use two folders lib/arch, which is not supported by lilv build system. On our side, we hardcode /usr/lib, it should check the pkgconfig libdir basename instead. And then we are missing the .lv2 folder in user home directory. Finally, we just don't support Windows and OSX at all. While at it we should fix it properly.

Created attachment 365713 [details] [review]
lv2: Recursively monitor the lv2 plugin path

Otherwise we might not update the cache when needed.

Created attachment 365724 [details] [review]
lv2: Try and reflect better lilv default path

While keeping it simple, this patch tries and mimic lilv default path.
It does not matter if some path are duplicated due to symlink because in
the end it's lilv that will walk these paths. The worst case is that we
update our cache more often then strictly needed.

Attachment 365713 [details] pushed as 8c850b3 - lv2: Recursively monitor the lv2 plugin path
Attachment 365724 [details] pushed as fbd9a62 - lv2: Try and reflect better lilv default path

If needed (and if no issues are found) we can backport this to 1.12. Thanks for reporting.

Considering the time non rolling release distributions take to do major updates to GStreamer it would be good to have this backported to 1.12 if possible.

Thank you for the fix.

Noted, let's make sure it's all stable for everyone though, I'll come back in a week or so.