Re: [LAD] alsa sequencer latency ( snd_seq_ev_schedule_real ) - need help!

On Saturday 10 January 2009 16:13:44 Fons Adriaensen wrote:
> On Sat, Jan 10, 2009 at 03:59:06PM -0500, nescivi wrote:
> > since I get no response here...
> > which list you recommend I post this question to?
> > I also got no reaction on the alsa-dev list... alsa-user then?
> >
> > > int SC_AlsaMidiClient::sendEvent(int outputIndex, int uid,
> > > snd_seq_event_t* evt, float late)
> > > {
> > > snd_seq_real_time time;
> > >
> > > if ((outputIndex < 0) || (outputIndex >= mNumOutPorts)) return
> > > errIndexOutOfRange;
> > >
> > > snd_seq_ev_set_source(evt, mOutPorts[outputIndex]);
> > > if (uid == 0) {
> > > // send to all subscribed ports
> > > snd_seq_ev_set_subs(evt);
> > > } else {
> > > // send to specific port
> > > int cid, pid;
> > > SC_AlsaParseUID(uid, cid, pid);
> > > snd_seq_ev_set_dest(evt, cid, pid);
> > > }
> > >
> > > long latelong;
> > > if (late > 0.f) {
> > > latelong = (long) (late * 1000000000);
> > > // new time calculation. The old one was not correct
> > > time.tv_sec = (long)(latelong / 1000000000); // seconds
> > > time.tv_nsec = (long)(latelong % 1000000000); // nanoseconds
> > > } else {
> > > time.tv_sec = time.tv_nsec = 0;
> > > }
> > >
> > > // evt->flags = evt->flags | SND_SEQ_TIME_STAMP_REAL;
> > >
> > > post("MIDI (ALSA): sending event, time %i, %i, late %f, latelong
> > > %i\n", time.tv_sec, time.tv_nsec, late, latelong);
> > >
> > > snd_seq_ev_schedule_real(evt, mQueue, 1, &time);
> > > snd_seq_event_output_direct(mHandle, evt);
> > > // snd_seq_event_output(mHandle, evt);
> > >
> > > return errNone;
> > > }
>
> If 'late' > 2.147 then 'latelong' will go negative.
> Could this happen when you schedule an event more than
> 2 seconds ahead of due time ?

no, it happens even if I set late to 0.1.
It is really strange. Sometimes it just works for a while, and then it just
takes minutes before any event comes out.
The values print out fine, just something weird seems to be happening in the
actual scheduling.

> Alternative:
>
> time.tv_sec = (long)(floorf (late));
> time.tv_nsec = (long)((late - time.tv_sec) * 1e9f);

thanks, I'll try that too.

sincerely,
Marije
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Received on Sun Jan 11 08:15:01 2009