Re: Simple alsa sequencer question

[Ryan Pavlik <rpav@mephle.com>]

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On Mon, 27 Oct 2003 11:54:21 +0100
Takashi Iwai <tiwai@suse.de> wrote:

> At Sat, 25 Oct 2003 02:41:06 -0700,
> Ryan Pavlik wrote:
<snip>
> > Shouldn't I get numbers in ev->time.time.tv_*?  I'm just getting
> > zeros... what did I miss? ;)
> 
> no, it should be, as long as the event is delivered to these
> subscribers (i.e. setting the destination as SND_SEQ_ADDR_SUBSCRIBERS).
> 
> btw, to update the timestamp of every event to a certain port, you can
> set the timestamp attribute on the port_info, too.

OK, I've attached some code to show what I'm doing exactly.

I'm trying to receive input from an external sequencer that's tagged
with the event arrival time.  The docs indicate this should be no
problem, and I believe I've done what they say, but I'm obviously not
doing something right. :-)

I prefer time in realtime, not midi time, for accuracy and time
calculation reasons, but neither seems to work.

Also, I seem to be getting a lot of type 42 messages (active sense).
Now, only one piece of gear (Roland, go figure ;) generates these, and
the MTP/AV i'm using blocks them (thankfully).  The Roland gear is
off, and the MTP/AV shows no input traffic.  Why am I still getting
these messages...?  (For my ruby lib, i'm filtering them at the moment
since they're the useless, but saving a little CPU would be nice,
too.)

Thanks,

-- 
Ryan Pavlik <rpav@mephle.com>

"I believe in exploiting debts, not having them." - 8BT

[-- Attachment #2: test.c --]
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#include <alsa/asoundlib.h>

#define CLIENT 72
#define PORT    0

void subscribe_to(snd_seq_t *seq, int port, int client, int c_port);

int main() {
    snd_seq_t       *seq;
    int              port;
    snd_seq_event_t *ev;

    /* Open the sequencer */
    snd_seq_open(&seq, "default", SND_SEQ_OPEN_INPUT, 0);
    snd_seq_set_client_name(seq, "test");

    /* Our port */
    port = snd_seq_create_simple_port(seq, "test port",
                                      SND_SEQ_PORT_CAP_WRITE|SND_SEQ_PORT_CAP_SUBS_WRITE,
                                      SND_SEQ_PORT_TYPE_MIDI_GENERIC|SND_SEQ_PORT_TYPE_APPLICATION);


    subscribe_to(seq, port, CLIENT, PORT);

    for(;;) {
        snd_seq_event_input(seq, &ev);
        printf("Type: %d Time: %d %d\n", ev->type, ev->time.time.tv_sec,
               ev->time.time.tv_nsec);
        /* This prints 0 0 ... what do I do to receive time? */
    }
}

void subscribe_to(snd_seq_t *seq, int port, int client, int c_port) {
    snd_seq_addr_t sender, dest;
    snd_seq_port_subscribe_t *subs;
    int queue;
    snd_seq_event_t ev;

    sender.client = client;
    sender.port   = c_port;
    dest.client   = snd_seq_client_id(seq);
    dest.port     = port;
    queue         = snd_seq_alloc_queue(seq);

    snd_seq_port_subscribe_alloca(&subs);
    snd_seq_port_subscribe_set_sender(subs, &sender);
    snd_seq_port_subscribe_set_dest(subs, &dest);
    snd_seq_port_subscribe_set_queue(subs, queue);
    snd_seq_port_subscribe_set_time_update(subs, 1);
    snd_seq_port_subscribe_set_time_real(subs, 1);
    snd_seq_subscribe_port(seq, subs);
}