stopping sequencer output queue gracefully

stopping sequencer output queue gracefully

[r10 kindsofpeople]

Is there example code around that shows how to stop MIDI playback 
gracefully?

At present, I'm doing a snd_seq_drop_output() and a snd_seq_stop_queue(), 
and getting some interesting behavior when I try to restart.

I'm also wondering if Alsa does anything to track or handle the stuck notes 
that result, or if my client needs to be responsible for tracking these and 
turning them off before stopping the queue.

John

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Re: stopping sequencer output queue gracefully

[Steve deRosier]

John,

Not sure of an answer to the first part of your question but for what I 
usually do is a snd_seq_free_queue() and a snd_seq_close().

But the answer to the second part: you need to keep track of what notes 
are on yourself... or take the easy way out and just run an all notes 
off message for every channel, or actually do a note off message for 
every note; that way no matter what you know you'll never stick a note. 
  Don't forget to turn the pedal controllers off also.

- Steve


r10 kindsofpeople wrote:
> Is there example code around that shows how to stop MIDI playback 
> gracefully?
> 
> At present, I'm doing a snd_seq_drop_output() and a snd_seq_stop_queue(), 
> and getting some interesting behavior when I try to restart.
> 
> I'm also wondering if Alsa does anything to track or handle the stuck notes 
> that result, or if my client needs to be responsible for tracking these and 
> turning them off before stopping the queue.
> 
> John
> 
> _________________________________________________________________
> Talk now to your Hotmail contacts with Windows Live Messenger. 
> http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://get.live.com/messenger/overview
> 
> 
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Re: stopping sequencer output queue gracefully

[Clemens Ladisch]

r10 kindsofpeople wrote:
> Is there example code around that shows how to stop MIDI playback 
> gracefully?
> 
> At present, I'm doing a snd_seq_drop_output() and a snd_seq_stop_queue(), 
> and getting some interesting behavior when I try to restart.

What do you mean with "interesting"?

After snd_seq_stop_queue(), you have to call snd_seq_drain_output() to
actually send the stop event.

> I'm also wondering if Alsa does anything to track or handle the stuck notes 
> that result, or if my client needs to be responsible for tracking these and 
> turning them off before stopping the queue.

A queue is just a tool for delivering events; ALSA doesn't try to
interpret the events sent through it.  Besides, different devices may
have different rules about sending of note-on/note-off events.

I'd just send an All Notes Off message.


HTH
Clemens

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