Most simple use of sequencer in ALSA

Most simple use of sequencer in ALSA

[Guenther Sohler]

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
What does "hw" mean ? what are the other possibilities ?



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Re: Most simple use of sequencer in ALSA

[Takashi Iwai]

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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Re: Most simple use of sequencer in ALSA

[Matthew Flax]

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
> 
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/alsa-devel

-- 
Matt

For electronic musicians ...
Vector Bass          : http://mffmvectorbass.sourceforge.net/
For developers ...
TimeScale Audio Mod  : http://mffmtimescale.sourceforge.net/
Multimedia Time Code : http://mffmtimecode.sourceforge.net/
3D Audio Library     : http://mffm3daudiolib.sourceforge.net/

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Re: Most simple use of sequencer in ALSA

[Guenther Sohler]

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
> 
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/alsa-devel

Guenther Sohler

NewLogic Technologies AG 
Millennium Park 6
A-6890 Lustenau
                                           Phone: +43-5577-62000-507
E-Mail: guenther.sohler@newlogic.com       Fax:   +43-5577-62000-988


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mixer problem with creative audixy - was most simple alsa seq application

[Guenther Sohler]

Thank you very much for the advice.
I dont need thr queue any more
Now almost all midi works again in my application - but now for alsa(instead of
oss)
But there is another problem now. I use an audixy card in my pc connected to an
external amplifier. 
Even the amplifier is set to the maximal volume, midi synth is quite silent
whereas pcm is very loud.

Obviously the problem is in the mixer

alsmixer shows me a lot of volumes to adjust, but actually just the volume of
"music" show en effect. maximum volume on music makes me hear a silent tune.
but "master" and all other volumes do not show(sound) a change in the volume.

In my application i can now select where the output goes to

64:0 is the external midi and 65:0-3 is the awe synth
64:0 does not work all the time. but directly piping midi date to the
respective /dev/snd/midixxxx always works(i hear a tune on the external
keyboard).
whats the problem here ?


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Most simple use of sequencer in ALSA

[Guenther Sohler]

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
What does "hw" mean ? what are the other possibilities ?



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Alsa-devel mailing list
Alsa-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/alsa-devel

Most simple use of sequencer in alsa

[Guenther Sohler]

Yesterday I was trying to use the sequencer to send a NOTEON EVENT to my
wavetable device. I did

*open the sequencer
*allocated a port_info structure
*filled in port and client to port_info
*attached info to sequencer
*allocated event
*freed event
* freed port structure

I was not able to get further as My program now caused a segfault which i was
not able to solve.

Can anyone email me a simple program to put a NOTEON event to any client/port
of the sequencer. I do not understand pmidi because it is too complex for me to
understand. I'd wish to get/receive/see a simple program with approx 30 lines

Can anybody help me ?

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Re: Most simple use of sequencer in alsa

[Ricardo Colon]

Take a look at the seq.c file. It's in the directory of test programs that
come with ALSA. It's definitely the simplest example.

Otherwise, I can't really help you unless I see your code.

Thanks.

					-- R:

On Thu, 14 Feb 2002, Guenther Sohler wrote:

> Yesterday I was trying to use the sequencer to send a NOTEON EVENT to my
> wavetable device. I did
>
> *open the sequencer
> *allocated a port_info structure
> *filled in port and client to port_info
> *attached info to sequencer
> *allocated event
> *freed event
> * freed port structure
>
> I was not able to get further as My program now caused a segfault which i was
> not able to solve.
>
> Can anyone email me a simple program to put a NOTEON event to any client/port
> of the sequencer. I do not understand pmidi because it is too complex for me to
> understand. I'd wish to get/receive/see a simple program with approx 30 lines
>
> Can anybody help me ?
>
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/alsa-devel
>


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