thank you for your info.
now i know that my procedure was almost correct.
Until now i had good success in porting my app to alsa. it will be completed
soon.
rds guenther
On 15-Feb-02 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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Guenther Sohler
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