Develop a softsynth with LV2

[f00bar]

I am trying to implement an LV2 softsynth

main.cpp

#include <lv2/lv2plug.in/ns/ext/atom/atom.h>
#include <lv2/lv2plug.in/ns/ext/atom/util.h>
#include <lv2/lv2plug.in/ns/ext/midi/midi.h>
#include <lv2/lv2plug.in/ns/ext/urid/urid.h>
#include <lv2/lv2plug.in/ns/lv2core/lv2.h>

struct Fatsaw
{
const LV2_Atom_Sequence* midi_in;
float* output_L;
float* output_R;
};

static const char* URI="http://example.org/fatsaw";

static LV2_Handle instanceCreate(const LV2_Descriptor* descriptor,double rate
,const char* bundle_path,const LV2_Feature* const* features)
{
return new Fatsaw;
}

static void portConnect(LV2_Handle fatsaw,uint32_t port,void* data)
{
Fatsaw* obj=(Fatsaw*)fatsaw;
switch(port)
{
case 0:
obj->midi_in=(const LV2_Atom_Sequence*)data;
break;
case 1:
obj->output_L=(float*)data;
break;
case 2:
obj->output_R=(float*)data;
break;
}
}

static void activate(LV2_Handle fatsaw)
{

}

static void process(LV2_Handle fatsaw, uint32_t n_samples)
{
// Write code here
}

static void deactivate(LV2_Handle fatsaw)
{
}

static void instanceDestroy(LV2_Handle fatsaw)
{
Fatsaw* obj=(Fatsaw*)fatsaw;
delete obj;
}

static const void* extensionDataGet(const char* uri)
{return nullptr;}

static const LV2_Descriptor descriptor =
{
URI,
instanceCreate,
portConnect,
activate,
process,
deactivate,
instanceDestroy,
extensionDataGet
};

LV2_SYMBOL_EXPORT const LV2_Descriptor* lv2_descriptor(uint32_t index)
{
switch (index)
{
case 0:
return &descriptor;
default:
return nullptr;
}
}

manifest.ttl

@prefix atom: <http://lv2plug.in/ns/ext/atom#> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
@prefix midi: <http://lv2plug.in/ns/ext/midi#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix urid: <http://lv2plug.in/ns/ext/urid#> .

<http://example.org/fatsaw>
a lv2:Plugin;
lv2:binary <fatsaw.so>;
doap:name "Fatsaw";
doap:license <http://usefulinc.com/doap/licenses/gpl>;


lv2:port
[
a lv2:InputPort,atom:AtomPort;
lv2:index 1;
lv2:symbol "midi_in";
lv2:name "MIDI in";
],
[
a lv2:OutputPort,lv2:AudioPort;
lv2:index 1;
lv2:symbol "output_L";
lv2:name "Output L";
],
[
a lv2:OutputPort,lv2:AudioPort;
lv2:index 2;
lv2:symbol "output_R";
lv2:name "Output R";
].

g++ main.cpp -shared -fpic -std=c++11 -o fatsaw.so
cp * $HOME/.lv2/fatsaw.lv2


Ardour claims it is invalid. What is missing?

I want to implement a clone of TrancsenderSE. This synth has 10 detuned sawtooth/squarewave oscillators + 5 oscillators one octave down. The envelope controls a LP filter. To get the thing working, the plug-in has to know the current beat, because the gate produces a rythm pattern. BTW the lv2 docs could have been better.

[ssj71]

hmm. I don't see anything blatantly wrong, but I'm not an expert. I just copied other people's plugin ttl when I made my synth plugin. You would probably do well to test using jalv rather than ardour while you're just getting started. It might give a bit more verbose error message. Falktx also has made a program that installs with carla that will scan/validate your ttl . Sorry I can't help more.
EDIT, if you do IRC hop onto #lad and you might get help a bit faster.

[tramp]

along with the manifest.ttl, you need a fatsaw.ttl
in the manifest you only point to the library witch contain your plug, the description comes in the fatsaw.ttl.
here is a example synth
http://lv2plug.in/browser/trunk/plugins ... order=name

[f00bar]

along with the manifest.ttl, you need a fatsaw.ttl
in the manifest you only point to the library witch contain your plug, the description comes in the fatsaw.ttl.
here is a example synth
http://lv2plug.in/browser/trunk/plugins ... order=name

That is just convention, but it is a good idea to give each port a uniq number in the ttl file (was 1 1 2 inseat of 0 1 2).

[sysrqer]

falkTX, I don't want to derail the thread but just to say thank you for posting that, they look amazing. Do you know if the vst builds with those if it is enabled?

[f00bar]

falkTX, can you give a short introduction to your build system. Is it just copying the plugins directory and clear all sub-directories?

[f00bar]

So I define a macro, then I get a different backend. But I need timepos for trigging the trance gate.

#if DISTRHO_PLUGIN_WANT_TIMEPOS
# warning LV2 TimePos still TODO
#endif

[tramp]

along with the manifest.ttl, you need a fatsaw.ttl
in the manifest you only point to the library witch contain your plug, the description comes in the fatsaw.ttl.
here is a example synth
http://lv2plug.in/browser/trunk/plugins ... order=name

That is just convention, . . .

This is true for .h / .hpp files as well.

[f00bar]

So I define a macro, then I get a different backend. But I need timepos for trigging the trance gate.

#if DISTRHO_PLUGIN_WANT_TIMEPOS
# warning LV2 TimePos still TODO
#endif

The basic LV2 time stuff is done, but no one made a plugin that needed it until now.
if you look at the code, the missing bits are:

Code: Select all

// TODO:
// - tick
// - barStartTick
// - ticksPerBeat

the other stuff on the TimePos struct is already working.
Do you need any of those 3 in the TODO?

I do need to know where to start the gate sequence. So as long as there is a reference framecount where I know the values of beat and tick, it is fine.