Lilv 0.16.0 is out. Lilv is a C library to make the use of LV2 plugins as simple as possible for applications.

This release fixes many bugs and adds several convenient functions to the API. Upgrading is recommended.

Changes:

• Add lilv_world_ask() for easily checking if a statement exists
• Add lilv_world_get() and lilv_port_get() for easily getting one value
• Add lilv_nodes_merge()
• Make lilv_plugin_get_port_by_designation() return a const pointer
• Require a URI for lilv_state_to_string() and fail gracefully otherwise
• Fail gracefully when lilv_state_new_from_string() is called on NULL
• Make state loading functions fall back to lv2:default for port values, so a plugin description can be loaded as default state
• Ignore state ports with no value instead of printing an error
• Support atom:supports in lilv_port_supports_event()
• Add va_list variant of lilv_plugin_get_num_ports_of_class()
• Fix several plugin functions that failed to load data if called first
• Correctly depend on serd at build time (fix compilation in odd cases)
• Disable timestamps in HTML documentation for reproducible build
• lilvmm.hpp: Support varargs for Plugin::get_num_ports_of_class()
• lilvmm.hpp: Add several missing methods
• Update to waf 1.7.8 and autowaf r90 (install docs to versioned directory)

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Sratom 0.4.2 is out. Sratom is a small C library for serialising LV2 atoms to/from Turtle.

This releases fixes a few minor bugs and memory leaks, and shrinks the code slightly by making of the new sord_get() function.

Changes:

• Fix serialisation of nested tuples
• Fix memory leaks
• Use new sord API to clean up and shrink code
• Disable timestamps in HTML documentation for reproducible build
• Update to waf 1.7.9 and autowaf r90 (install docs to versioned directory)

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Today I implemented better UI generation for LV2 plugin controls in Jalv, particularly grouping controls under headings which makes a big difference. Unfortunately few plugins group their controls currently, but hopefully more host support will provide the incentive to do so.

Other improvements:

• Added a spinbutton to slider controls for precisely setting values numerically
• Much more efficient layout to pack more controls on the screen at once
• Support for named scale points (“ticks”) on non-enumeration ports

Here is the UI generated for Amsynth (after I added the necessary metadata):

Still pretty utilitarian, but much more usable, which is the important thing. Of course, this plugin is quite large, and has a pretty good custom UI, but I happened to be polishing up its metadata anyway and the controls group nicely so I used it as my test case.

Maybe some day this code will get smarter and evolve into a library that can be used by other Gtk hosts. Better group layout is the obvious “next level” advancement, a flat linear list of controls is pretty limited. Unfortunately there’s no stock Gtk container which can do text-like reflow, which would be ideal. Perhaps a simpler scheme based on a maximum reasonable width for a controller would do, where the table will expand to have more columns if the window is wide enough for several.

Most of the metadata required to generate a good UI is also useful for other purposes, for example groups make building a decent menu of many controls feasible (e.g. to add automation lanes in Ardour), and some types of host UIs like a modular patcher inherently need to generate their own “UI” of sorts.

Good metadata is not at odds with custom UIs, they each have their uses, but it is important to remove the burden of custom UIs for simple plugins with just a few controls that really don’t need them. It’s a waste of that most precious of all resources – developer time – to have to code UIs for a few sliders and toggles. Hopefully better host generated UIs and support for more advanced controls like file selectors free up developers to spend more time making useful plugins and less time wrestling with GUI toolkits.

It is, after all, all about the sound.

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LV2 has been slowly but surely moving towards message-based control to overcome the limitations of static ports. The required low level facilities have been available for a while now, but the lack of a standard way to document message-based parameters and host UI support has been a sticking point. One particularly pressing need is file parameters. The current sample example has a stop-gap UI to enable sample loading, but parameters really should be host controllable and simple plugins should not need a custom UI to be usable. Today I did some work towards resolving that situation.

Here is ConvoLV2 running in Jalv:

Note this is the built-in UI generated by Jalv and not a custom plugin UI. Unlike traditional LADSPA style controls, the impulse parameter is not a port, but is set by sending a message to an event port. The plugin lists parameters with the new patch:writable property, so the host knows which controls to display (or which parameters it can automatically set). Parameters are described as normal RDF properties, so any existing property can be used, or plugins can define them as needed in their data files (don’t let the “RDF” scare you, the description of a Property is as simple as LV2 ports). One nice advantage of this over ports is that a project can describe a parameter once and use it in many plugins, without having to describe the parameter every time. This really adds up when you have hundreds of plugins with, say, an identical gain parameter.

These conventions will be established in the next LV2 release (1.4.0), and the sampler example will serve as a test case. When host support becomes established, we can also move towards using messages for numeric parameters, which will finally allow for dynamic parameters, control ramps, and so on.

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