Re: [Jack-Devel] dropped midi messages on os x using the IAC driver? at a loss!

you can use jack_midi_dump (it may only be in the jack1 tools
directory, but it will work with jack2 just as well) to track what
MIDI data shows up at your JACK port(s).

On 3/17/12, Iain Duncan <[hidden]> wrote:
> Hi folks, I'm sure this isn't a jack bug or it would have been noticed ages
> ago, but I'm hoping someone has some advice on how to figure out what the
> heck's going on.
>
> I have a jack app, it sends out midi. Seems to be fine about 99% of the
> time, and maybe once every hundred messages, a midi message gets dropped. I
> am sending out the messages using jack_midi_event_reserve, and that seems
> ok, can't imagine it would work 99% of the time if I'm doing it wrong.  I
> have some debug printf showing that my app thinks it's written the dropped
> message to the jack midi buffer.
>
> Using jack pilot, I have my app routed to the IAC loopback driver on os x,
> and I have a vst synth (Zebra2) playing on a channel in Reaper. I also have
> a midi monitor open spying on the output. The dropped messages are printed
> in my app, and then don't show up in the midi monitor. So I guess either:
>
> - they aren't really going out from my app
>
> - or are they aren't really getting through the IAC driver.
>
> - or something else I can't fathom.
>
> Does anyone have any experience with midi message loss on os x? Suggestions
> on how to figure this out or even how to debug it would be luverly. I'm
> pretty new to Jack, OS X, IAC, the works. :-/
>
> Below is the code for how the messages are going out in case I did
> something dumb!
>
> Thanks
> Iain
>
>     ... in the jack process audio callback method
>
>     // grab our output buffers, needs to happen each time process is called
>     int num_audio_ports = NUM_AUDIO_PORTS;
>     sample_t *audio_output_bufs[ num_audio_ports ];
>     for( int port_index=0; port_index < NUM_AUDIO_PORTS; port_index++ ){
>         audio_output_bufs[ port_index ] = (sample_t *)
> jack_port_get_buffer( audio_out_ports[port_index], nframes);
>     }
>     for(jack_nframes_t frame_index=0; frame_index < nframes; frame_index++){
>         // get midi and audio output for each port
>         // the redundant layer is to keep jack types out of the engine code
>         DataFloat audio_samples[NUM_AUDIO_PORTS];
>         int num_midi_messages_from_engine;
>         // call the engine's process method
>         // writes num_audio_ports samples into audio_samples
>         // writes num_midi_messages_from_engine 3 char midi messages into
> midi_from_engine_buf
>         engine->processSample(audio_samples, num_audio_ports,
>             midi_from_engine_buf, num_midi_messages_from_engine );
>
>         // if the engine wrote midi output data, send them out
>         for( int i=0; i < num_midi_messages_from_engine; i++ ){
>             //cout << "Midi messages from engine: " <<
> num_midi_messages_from_engine << "\n\n";
>             // reserve 3 chars of space from the midi out port buffer as
> the per note buf
>             midi_out_msg_buf = jack_midi_event_reserve(midi_out_port_buf,
> frame_index, 3);
>             // copy the midi message, jack will send this out
>             midi_out_msg_buf[0] = midi_from_engine_buf[ (i * 3) + 0 ];
>             midi_out_msg_buf[1] = midi_from_engine_buf[ (i * 3) + 1 ];
>             midi_out_msg_buf[2] = midi_from_engine_buf[ (i * 3) + 2 ];
>             printf("    - sending jack midi message: %i %i %i\n",
> midi_from_engine_buf[ (i * 3) + 0 ],
>                 midi_from_engine_buf[ (i * 3) + 1 ],  midi_from_engine_buf[
> (i * 3) + 2 ]);
>
>         }
>
>         // copy the audio samples from my buff to the jack buff
>         for( int port_index=0; port_index < NUM_AUDIO_PORTS; port_index++ ){
>             audio_output_bufs[port_index][frame_index] =
> (sample_t)audio_samples[port_index];
>         }
>     }
>

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