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Hi,
On Thursday 05 January 2012, Dave Stikkolorum wrote:

quoted text
> Hi all,

>

> I try to write a c program that sends midi notes to the Hydrogen drum

> sequencer.

> I use the alsa library to create a client with an output port.

>

> I attached two files.

>

> loopqueue.c works but loop.c doesn't.

>

> A base drum (note:28) is being send.

>

> I am not succeeding to use direct delivery,

> but it only works with the queue.

>

> Any ideas why?

In both programs you need to connect the output port to some input port (for

instance, a soft synth). To do so, you can insert a call to

snd_seq_connect_to() after creating your port:

	snd_seq_connect_to(seq, port, 20, 0);

Where 20:0 are the client:port numbers of the receiving port.
The problem in loop.c is that you are using the function snd_seq_ev_set_note()

that includes a duration as the 5th parameter. This function will create two

MIDI events in a queue, the first one will be the noteon event, and the second

one will be a noteoff event,  scheduled adding the specified duration to the

start time of the former noteon event. That requires a queue for event

scheduling.
If you don't mind about noteoff events, because most percussion synths don't

bother about them anyway, replace that function call by

snd_seq_ev_set_noteon(). There is also a snd_seq_ev_set_noteoff() function as

well. 
You may be interested in my C++/Qt4 wrapper around the ALSA sequencer API:

http://drumstick.sourceforge.net/docs/index.html
Here is how a simple program playing a note-on MIDI message using drumstick

looks like:
#include

#include 
int main(int argc, char **argv) {

    QApplication app(argc, argv, false);
    // create a client object on the heap

    drumstick::MidiClient *client = new drumstick::MidiClient;

    client->open();

    client->setClientName( "MyClient" );
    // create the port

    drumstick::MidiPort *port = client->createPort();

    port->setPortName( "MyPort" );

    port->setCapability( SND_SEQ_PORT_CAP_READ | SND_SEQ_PORT_CAP_SUBS_READ );

    port->setPortType( SND_SEQ_PORT_TYPE_MIDI_GENERIC );

    // subscribe the port to some other client:port

    port->subscribeTo( "20:0" ); // or "name:port", like in "KMidimon:0"
    // create an event object on the stack, to send a note on message

    drumstick::NoteOnEvent ev( 0, 66, 100 ); 
    ev.setSource( port->getPortId() );

    ev.setSubscribers();   // deliver to all the connected ports

    ev.setDirect();        // not scheduled, deliver immediately

    client->output( &ev ); // or outputDirect() if you prefer not buffered

    client->drainOutput(); // flush the buffer
    // close and clean

    client->close();

    delete client;

    return 0;

}
One program that uses Drumstick to play metronome and drum patterns is

KMetronome: http://kmetronome.sourceforge.net/kmetronome.shtml
Regards,

Pedro

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