Subject: Re: [linux-audio-dev] high level midi api
From: martijn sipkema (msipkema_AT_sipkema-digital.com)
Date: Mon Oct 29 2001 - 00:05:47 EET
> >i would like to have a midi api that is cross
> >platform and that makes good timing possible. also
> >synchronisation of audio and midi should be possible.
> >i don't think the serial interface suffices for this. and
> >i don't like a /dev/sequencer approach to timing.
>
> it would appear that you don't know anything about ALSA at this point
> in time. ALSA has support for almost everything you've mentioned,
> limited only by h/w manufacturer's willingness to share their h/w
> specs with us.
you are right, i am not familiar with alsa. from what i understand from
looking at it briefly:
- the midi driver accessed through rawmidi does not supprot scheduling,
i.e. it has read() and write() that have to be called at the right time and
the bytes are sent immediately.
- the alsa sequencer handles the scheduling of midi events and calls write()
on rawmidi ports at the time they are to be sent.
if i am wrong about this, then i'll need to look into alsa better, although
i'm
not sure where to find up to date documentation on alsa midi then.
if the above is correct however, than how should any timing a midi interface
have be supported through rawmidi?
and should synchronisation be in a sequencer device or in the application?
low latency patches and scheduler improvements should make accurate
timing possible from user space.
i am not criticising alsa, i just want to have the best midi possible and
would
like to start an open discussion on how that should look.
regards,
--martijn
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