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

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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