ah I think I get it now -- snd_seq_ev_set_queue_pos_tick is a macro which
constructs a special event type, it's not a function on the queue. So I
have to construct of these events then pass it to the timer at 0:0 ?
$aconnect -i
client 0: 'System' [type=kernel]
0 'Timer '
I'd still like to understand the ideas behind the architecture here though
-- why do we have snd_seq_queue_tempo_set_tempo as a direct function on
the queue to change tempo, but we have to send this event to a port to
change position ?
On Mon, Apr 4, 2016 at 10:11 AM, Charles Fox <[email protected]> wrote:
> Thanks very much Clemens.
>
> I saw this function in the API, but from from the name and signature,
> snd_seq_ev_set_queue_pos_tick(ev,q,ttime), I thought it was a method for a
> single event rather for the whole queue. Could you explain what the ev
> argument is for and what I need to put in it; and also why its called
> snd_seq_ev_set_queue_pos_tick rather than snd_seq_queue_set_pos_tick ?
>
> (I can see in the API docs this text, which I think tells what I need to
> put in ev, but I don't understand why this is needed, why's it not just
> snd_seq_queue_set_pos_tick(q,ttime) ?
>
> ((ev)->type = SND_SEQ_EVENT_SETPOS_TICK
> <http://www.alsa-project.org/alsa-doc/alsa-lib/group___seq_events.html#ggaef39e1f267006faf7abc91c3cb32ea40aeb233aee7f0548cd3b0fdc811c15d3ec>
> ,\
> snd_seq_ev_set_dest
> <http://www.alsa-project.org/alsa-doc/alsa-lib/group___seq_middle.html#gaff2d03c7db0d6d5cfeec429d160d9459>(ev,
> SND_SEQ_CLIENT_SYSTEM
> <http://www.alsa-project.org/alsa-doc/alsa-lib/group___sequencer.html#ga5437f98c59679c92ee4d940ac643169e>,
> SND_SEQ_PORT_SYSTEM_TIMER
> <http://www.alsa-project.org/alsa-doc/alsa-lib/group___seq_port.html#ga02870ceddec24d3cc5609ec728b0cb92>
> ),\
> (ev)->data.queue.queue = (q),\
> (ev)->data.queue.param.time.tick = (ttime))
>
> )
>
> thanks
>
>
>
>
> charles
>
>
>
>
>
>
>
>
>
>
>
> On Mon, Apr 4, 2016 at 9:12 AM, Clemens Ladisch <[email protected]>
> wrote:
>
>> Charles Fox wrote:
>> > The midiarp.c demo in the tutorial shows how to read the tick state,
>> > and how to get and set the tempo. So I was expecting to find
>> > a function called something like snd_seq_queue_set_tick , but there
>> > doesn't seem to be one in the API.
>>
>> To set a queue's timer's position, send a message
>> SND_SEQ_EVENT_SETPOS_TICK
>> and/or SND_SEQ_EVENT_SETPOS_TIME to the global timer port.
>>
>> There are macros snd_seq_ev_set_queue_pos_tick() and
>> snd_seq_ev_set_queue_pos_real() to help you construct such messages.
>>
>>
>> Regards,
>> Clemens
>>
>
>
>
--
Dr Charles Fox
Director, Ibex Automation Ltd, www.ibexautomation.co.uk
Academic Fellow, University of Leeds
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