Yeah mate - I like it when you dream ....
Do you dream in mosaics of computer screens and code ?
On 15 February 2002, Takashi Iwai wrote:
> At Fri, 15 Feb 2002 07:21:24 +0100 (MET),
> Guenther Sohler wrote:
> >
> > I have simplified the seq.c in the alsa-driver-test direcory for me
> > to also understand.
> >
> > The program is now quite short and outputs a note and quits
> >
> > here is it
> > -----------
> >
> > #include <stdio.h>
> > #include "alsa/asoundlib.h"
> >
> >
> > int main(int argc, char *argv[])
> > {
> > snd_seq_t *handle;
> > snd_seq_event_t ev;
> >
> > snd_seq_open(&handle, "hw", SND_SEQ_OPEN_DUPLEX, 0);
> > snd_seq_alloc_queue(handle);
> >
> > bzero(&ev, sizeof(ev));
> > ev.dest.client=65;
> > ev.dest.port=0;
> > ev.type = SND_SEQ_EVENT_NOTEON;
> > ev.data.note.channel = 0;
> > ev.data.note.note = 64 ;
> > ev.data.note.velocity = 127;
> > snd_seq_event_output_direct(handle, &ev);
> > sleep(1);
> > ev.type = SND_SEQ_EVENT_NOTEOFF;
> > snd_seq_event_output_direct(handle, &ev);
> > snd_seq_drain_output(handle);
> > return 0;
> > }
> >
> > There are two questions ?
> >
> > Why doesn't it work if I allocate no queue ? There is no need for a queue as i
> > directly output events
>
> No, you don't need to allocate a queue if you schedule by yourself.
> your program lack the schedule of events, i.e.
>
> snd_seq_ev_set_direct(&ev);
>
> before output the event packet. this is equivalent with
>
> ev.queue = SND_SEQ_QUEUE_DIRECT;
>
> if this is specified, the event is sent immediately to the
> destination, so you don't need any queue.
> as default, the event is scheduled using a specified queue, and as
> default, the queue is #0. that's why you had to allocate a queue.
>
> one more note: you don't need to call snd_seq_drain_output() when you
> send events via snd_seq_event_output_direct(). the drain_output() is
> necessary for buffered outputs via normal snd_seq_event_output()
> functions.
>
>
> > What does "hw" mean ? what are the other possibilities ?
>
> originally it means "hardware".
> in future it can be other ones, such like "network:foo", etc.
> (well, we can dream :)
>
>
> ciao,
>
> Takashi
>
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--
Matt
For electronic musicians ...
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