From alsa-devel-owner@alsa.jcu.cz  Fri Apr  3 22:46:20 1998
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From: Frank van de Pol <F.K.W.van.de.Pol@Inter.NL.net>
Message-Id: <199804022043.WAA19748@obelix.fvdpol.inter.nl.net>
Subject: Re: ALSA 0.0.7
To: alsa-devel@jcu.cz
Date: Thu, 2 Apr 1998 22:43:51 +0200 (MET DST)
In-Reply-To: <Pine.LNX.3.96.980402115035.24388D-100000@entry.jcu.cz> from "Jaroslav Kysela" at Apr 2, 98 12:22:23 pm
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Jaroslav Kysela wrote:
> 
> > - It has one stereo ADC and two stereo DAC's, with somewhat
> >   hackish 4 channel mode.
> 
> No problem. You can make 1 PCM device with playback & record ability and
> second PCM device with playback only (if DAC's can be programmed
> separately). This doesn't assume use of 4 channel mode for playback, but
> it can be used from user space. Note: What about synchro ioctl's for PCM
> to allow start/stop record/playback with two or more devices at one time
> to make this thing more precise? Anyone from application programmers have
> some idea?
> 

To synchronize (many?) devices an approach that is similar like the one OSS 
has can be taken:

- provide all devices with an option to arm it for recording or
  playback until a 'Go' event is sent to the device(s). When a device is
  opened it will be allocated, initialised etc. but no data will yet be played
  or recorded. The playback or recording will be triggered by this 'Go' event.

- provide an function (ioctl()) to emit this 'Go' event to the devices. When
  (for instance in a system with an AudioPCI and GUS MAX card) all three DAC's 
  are armed, and waiting for the final 'Go'; all these (six) channels will
  instantly start playing. Multitrack recorders here we come!

- If (once) an event scheduler is added to ALSA, starting audio
  recording and playback simultanious with midi events will give us a good
  'foundation' for building application that do harddisk recording combined
  with midi sequencing (Cubase VST comes to my mind).

How about this? 

Regards,

Frank.


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