[linux-audio-dev] alsa sequencer filter client

[Matthias Nagorni]

On Mon, 26 Jan 2004, Garett Shulman wrote:

> Matthias Nagorni wrote:
> 
> > On Sun, 25 Jan 2004, Garett Shulman wrote:
> > 
> >  
> > > Hello, I am trying to create a very simple midi filter client for the alsa
> > > sequencer based on aseqview-0.1.4. I have alsa 0.9.8. This code shows the
> > >    
> > 
> > Maybe you can base it on my MIDI router example in
> > http://www.suse.de/~mana/alsa090_howto.html
> > 
> > A QT MIDI router which you could take as example code is located at
> > ftp://ftp.suse.com/pub/people/mana/qmidiroute-0.0.2.tar.bz2
> > 
> > Matthias
> > 
> >  
> Matthias, Thank you for the suggestion. Your howto is exactly the information
> I need. Very nice. The code I was working with before is callback based. Do
> you have any opinion about callback vs. polling in regards to the alsa
> sequender? Do you think I will get less overhead if I use bits of the code in
> your howto in the callback framework? Thanks. -Garett

Discussed this briefly with Takashi (author of ALSA sequencer). Currently 
there is no wrapper library implemented, so the polling method I use in my 
MIDI examples is the only way to handle the asynchronous MIDI events.
If you want, you can regard the "midi_route" function as callback 
function. You could even write a wrapper function yourself which has a 
function pointer as argument, the while(1) { poll (... } as body and will 
call its argument function whenever poll returns, indicating that a new 
MIDI event is available for read. 

Matthias

-- 
Dr. Matthias Nagorni
SuSE Linux AG
Maxfeldstr. 5             phone: +49 911 74053375
D - 90409 Nuernberg       fax  : +49 911 74053483