[ALPHA] ladspa.m.lv2 - Some questions :D - Linux-audio-dev

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[ALPHA] ladspa.m.lv2 - Some questions :D

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Florian Paul Schmidt

22 Apr 2013 22 Apr '13

5:33 a.m.

Hi, These last few days I found some time to work on ladspa.m.lv2, an LV2 plugin to load ladspa.m.proto instrument definition files: https://github.com/fps/ladspa.m.lv2 It is in a somewhat usable state, i.e. used in ardour3 it loads the example instrument generated by this python script: https://github.com/fps/ladspa.m.proto/blob/master/example_instrument.py which is a very simple polyphonic sawtooth synth with exponential envelopes and an echo with differing delay times per voice. There's still some things to do (e.g. expose control ports, implement All-Notes-Off midi messages, lots of optimizations - right now I care more for correctness than for efficiency, etc.) and I also have some questions: 1] This one is regarding waf. I'm not used to writing wscript files and I adapted the whole thing from the example sampler from the LV2-distribution. I wonder how I can make waf to use e.g. -fPIC and other compiler flags needed for my 64-bit system. Right now I have put a little makefile into the repository which passes the missing options along as CXXFLAGS environment variable. This is a dirty hack. So if anyone waf guru might want to take a look, I'd be so ever grateful. https://github.com/fps/ladspa.m.lv2/blob/master/makefile https://github.com/fps/ladspa.m.lv2/blob/master/wscript 2] I'm a little bit puzzled by how the patch_set messages together with the LV2 worker extension works. If you take a look at this run() function https://github.com/fps/ladspa.m.lv2/blob/master/instrument.cc#L702 you'll see that I have an extra LV2_ATOM_SEQUENCE_FOR_EACH at the start of the function to process the patch_set messages. I tried to integrate that into the loop later on (that iterates over the sample_count frames and lets the midi events take effect at their respective frame), but once I do that, patch loading stops to work. I must be missing something fundamental. So if any LV2 guru might want to take a look, I'd be very grateful, too Thanks and have fun, Flo -- Florian Paul Schmidt http://fps.io

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hermann meyer

23 Apr 23 Apr

10:47 a.m.

Am 22.04.2013 07:33, schrieb Florian Paul Schmidt:

...

Hi I'm far from being a waf expert, but I will try to help you out here: You can use conf.env['cshlib_LINKFLAGS'].append("-fPIC") or conf.env['shlib_LINKFLAGS'].append("-fPIC") or conf.env['cxxshlib_LINKFLAGS'].append("-fPIC") somewhere in the def configure(conf): part to set the link flag and you can use in the obj = bld cflags = '-Wall -O3 -march=native', or cxxflags = '-Wall -O3 -march=native', depending on your seated obj = bld(features = 'c cshlib', or obj = bld(features = 'cxx cxxshlib', greets hermann

...

2] I'm a little bit puzzled by how the patch_set messages together with the LV2 worker extension works. If you take a look at this run() function https://github.com/fps/ladspa.m.lv2/blob/master/instrument.cc#L702 you'll see that I have an extra LV2_ATOM_SEQUENCE_FOR_EACH at the start of the function to process the patch_set messages. I tried to integrate that into the loop later on (that iterates over the sample_count frames and lets the midi events take effect at their respective frame), but once I do that, patch loading stops to work. I must be missing something fundamental. So if any LV2 guru might want to take a look, I'd be very grateful, too Thanks and have fun, Flo

Florian Paul Schmidt

11:37 a.m.

On 04/23/2013 12:47 PM, hermann meyer wrote:

...

Am 22.04.2013 07:33, schrieb Florian Paul Schmidt:

Hi, thanks for the info, but I would expect that there's a maybe more portable way, at least for the -fPIC option> Flo -- Florian Paul Schmidt http://fps.io

hermann meyer

25 Apr 25 Apr

6 a.m.

Am 23.04.2013 13:38, schrieb Florian Paul Schmidt:

...

Hi, thanks for the info, but I would expect that there's a maybe more portable way, at least for the -fPIC option> Flo

So you mean command-line options? Or do you look for some automatism? However, here are command-line options implementations for this: def options(opt): opt.load('compiler_c') autowaf.set_options(opt) comp = opt.add_option_group ('Set additional build flags', '') comp.add_option('--cflags', type='string', default='-Wall', dest='cflags', help='C base compiler flags [Default: %default]') comp.add_option('--linkflags', type='string', default='', dest='cshlibLINKFLAGS', help='C base link flags [Default: %default]') def configure(conf): conf.load('compiler_c') autowaf.configure(conf) autowaf.display_header('Amp Configuration') opt = conf.options if opt.cflags: conf.env['CFLAGS'] += opt.cflags.split() if opt.cshlibLINKFLAGS: conf.env['LINKFLAGS_cshlib'] += opt.cshlibLINKFLAGS.split() [.....] autowaf.display_msg(conf, "LV2 bundle directory", conf.env['LV2DIR']) autowaf.display_msg(conf, "Cflags in use", conf.env['CFLAGS']) autowaf.display_msg(conf, "Linkflags in use", conf.env['LINKFLAGS_cshlib']) greets hermann

David Robillard

9 May 9 May

8:46 p.m.

On Tue, 2013-04-23 at 12:47 +0200, hermann meyer wrote: [...]

...

> 2] I'm a little bit puzzled by how the patch_set messages together > with the LV2 worker extension works. If you take a look at this run() > function > > https://github.com/fps/ladspa.m.lv2/blob/master/instrument.cc#L702 > > you'll see that I have an extra LV2_ATOM_SEQUENCE_FOR_EACH at the > start of the function to process the patch_set messages. I tried to > integrate that into the loop later on (that iterates over the > sample_count frames and lets the midi events take effect at their > respective frame), but once I do that, patch loading stops to work. I > must be missing something fundamental. So if any LV2 guru might want > to take a look, I'd be very grateful, too

(Sorry for the late reply, I don't monitor LAD very closely these days) You should be able to handle all the events in one loop. However here you seem to be iterating over all events *for every frame*? That would cause a problem with loading since you'll issue a ton of identical load requests, but it also probably isn't what you want for MIDI either. You'll trigger everything repeatedly and the timing is wrong. I think you need to unify your two loops here. The general pattern for sample-accurate event receiving is work through time in the event loop, outputting everything up to the current event. So you start with t=0. The next event loop in the loop is at t=5, so render the output for 0..5, process the event (to e.g. trigger a voice or whatever), then continue. After the loop output everything from the last event to the end of the cycle. So your event processing loop is your processing loop, and proceeds in 'chunks' delimited by events. The magic of the worker extension is you can do non-RT things like load new sample banks, which will happen RT-safe (with latency) if running realtime, but if freewheeling (e.g. for export) the scheduled work will execute immediately/synchronously. Thus you can get sample accurate exporting, e.g. with a patch load at t=0 and a note on at t=1 the note is guaranteed to play with the new patch (in the export). You don't need to worry about this, but it's why things are the way they are... plus it's pretty cool :) Hopefully that makes sense, the simplest example of how to do this is in the metro example: http://lv2plug.in/browser/trunk/plugins/eg03-metro.lv2/metro.c#L296 tl;dr: Do that :) -dr

Florian Paul Schmidt

9:02 p.m.

On 05/09/2013 10:46 PM, David Robillard wrote:

...

Nope, I do not iterate over all events in every frame. Before iterating over the frames I get the first event and then on every frame I iterate over those events that have that frame time.. This is similar to how the jack_midi example code does it.. // First the worker events stuff ONCE per run() call LV2_ATOM_SEQUENCE_FOREACH(self->control_port, ev) { [...] } // Then the iteration over the frames... LV2_Atom_Event *ev = lv2_atom_sequence_begin(&(self->control_port)->body); [...] for (unsigned frame_index = 0; frame_index < sample_count; ++frame_index) { [...] while (false == lv2_atom_sequence_is_end(&(self->control_port)->body, self->control_port->atom.size, ev) && ev->time.frames == frame_index) { [...] ev = lv2_atom_sequence_next(ev); } [...] // Did we reach the end of a chunk or the last of the sample_count? if (0 == (frame_index + 1) % buffer_size || sample_count == frame_index + 1) { process(self, frame_index % buffer_size + 1, chunk_index * buffer_size); ++chunk_index; } }

...

The general pattern for sample-accurate event receiving is work through time in the event loop, outputting everything up to the current event. So you start with t=0. The next event loop in the loop is at t=5, so render the output for 0..5, process the event (to e.g. trigger a voice or whatever), then continue. After the loop output everything from the last event to the end of the cycle. So your event processing loop is your processing loop, and proceeds in 'chunks' delimited by events. The magic of the worker extension is you can do non-RT things like load new sample banks, which will happen RT-safe (with latency) if running realtime, but if freewheeling (e.g. for export) the scheduled work will execute immediately/synchronously. Thus you can get sample accurate exporting, e.g. with a patch load at t=0 and a note on at t=1 the note is guaranteed to play with the new patch (in the export). You don't need to worry about this, but it's why things are the way they are... plus it's pretty cool :) Hopefully that makes sense, the simplest example of how to do this is in the metro example: http://lv2plug.in/browser/trunk/plugins/eg03-metro.lv2/metro.c#L296

I do use the worker extension. The only problem I saw was when I tried to integrate the patch_set messages in that same loop. Flo -- Florian Paul Schmidt http://fps.io

David Robillard

9:16 p.m.

On Thu, 2013-05-09 at 23:02 +0200, Florian Paul Schmidt wrote:

...

On 05/09/2013 10:46 PM, David Robillard wrote:

I see, I misread the code. I suppose that works if you need to iterate over every frame for other reasons.

...

I do use the worker extension. The only problem I saw was when I tried to integrate the patch_set messages in that same loop.

There shouldn't be a difference. Assuming that, in the integrated case, you're scheduling the exact same work (easy enough to check) nothing should be any different, unless something is wrong with the asynchronous work stuff and some really fine timing problems are happening... everything looks good though, the work stuff shouldn't be affected by / affect state... What kind of problem? -dr

Florian Paul Schmidt

9:25 p.m.

On 05/09/2013 11:16 PM, David Robillard wrote:

...

I do use the worker extension. The only problem I saw was when I tried to integrate the patch_set messages in that same loop. There shouldn't be a difference. Assuming that, in the integrated case, you're scheduling the exact same work (easy enough to check) nothing should be any different, unless something is wrong with the asynchronous work stuff and some really fine timing problems are happening... everything looks good though, the work stuff shouldn't be affected by / affect state... What kind of problem?

For some reason patch setting didn't work in this case at all. I sprinkled some debugging output into the code to see what was up. It seems the load_instrument function never got called. But before putting any more effort into diagnosing the problem, I'll take your work as to that it should really work that way, too. I'll just assume that I messed up somewhere else and see if I can try to widen my understanding of the worker extension (I basically built this plugin based on the eg-sampler plugin from the lv2 distribution, so some parts I just copied and pasted with only minor adjustments).. Flo -- Florian Paul Schmidt http://fps.io

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David Robillard
Florian Paul Schmidt
hermann meyer