Subject: RE: [Alsa-devel] Re: [linux-audio-dev] midi events in jack callback / ALSA Sequencer
From: mikko.a.helin_AT_nokia.com
Date: Thu Aug 22 2002 - 14:51:48 EEST
Why is it important to keep the API simple, shouldn't it be functional in first place and make the API usage simply?
Anyway (IMHO), there should really be an API which combines audio and MIDI playback, recording and timing of events and makes it possible to keep MIDI in sync with audio (ALSA sequencer API seems to support only tick and time synchronization modes, no audio clock sync mode). Professional API's like ASIO and VST (and DirectMusic) synchronizes everything to audio clock (sample position). Even when MTC is used the audio clock is the main clock source, digital I/O or world clock is used to sync the audio clock to the audio clock of the external device. There is no need for other sync modes than audio (_maybe the tick mode could be useful if ALSA takes care of sending MIDI clock, SPP, MTC etc. data to external devices). Sequencer application can easily convert sample position from the beginning of the song to measures / beats, time etc. whatever is needed when the time signature, tempo and sample rate is known - reading the sample position from the sound card is no problem at all!
, PCI chipset's DMA registers have usually such current play position register, or if not, the sample position can be calculated by measuring the time between IRQ's and calculating the time between current time and the time when last interrupt was received.
-Mikko
> etc. Of course
> you
> > might be using one big monolithic (cubase?) sequencer
> application which
> does
> > do everything you need....
>
> No, I like the concept of a lot of small applications. And I
> want those to
> be able
> to sync (slave) to MIDI clock.
>
>
> I think it is important to keep the API as simple as possible.
>
> --martijn
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