Subject: Re: [ecasound] full-duplex sync
From: CLOTILDE Guy Daniel (guy.clotilde_AT_wanadoo.fr)
Date: Fri Oct 12 2001 - 19:38:23 EEST
hum so I think my post was irrelevant for you.
That's ok. To please you, I will think twice (maybe three times :) before responding to your next time.
On Fri, 12 Oct 2001 08:50:42 -0400
John Denker <jsd_AT_research.att.com> wrote:
> At 03:16 PM 10/12/01 +0400, CLOTILDE Guy Daniel wrote:
>
> >Yes
> >Ecasound does it.
>
> That's encouraging!
>
> >About the hardware, the best you have, the best it will be but even with a
> >low-end card you can achieve non-noticeable latencies.
>
> That's confusing! We are not primarily worried about latency. We have
> already achieved reasonably low latency; further reductions are not critical.
>
> Things that may be "non-noticeable" to you are noticeable to us. What we
> care about is !exact! sync between input and output.
>
> >Above all, tuning your kernel can lead you up to a 1,5 millisecond of latency.
>
> To repeat: We need the sync to be reproducible down to the last sample, to
> within a few microseconds. Yes, microseconds. Latency is not the same as
> sync. A millisecond or two of latency is fine with us, but we really,
> really need good sync.
>
> >A google search with 'morton low-latency kernel patch' should lead you to
> >the one that match your kernel version.
>
> To repeat: That won't solve the problem of interest.
>
> >On Thu, 11 Oct 2001 15:18:59 -0400
> >"John S. Denker" <jsd_AT_research.att.com> wrote:
> >
> > > Hi --
> > >
> > > We need to do full-duplex. Simultaneous play + record.
> > > It is absolutely essential to get the timing right.
> > > We have hardware that is documented to support this; see
> > > http://www.midiman.net/support/manuals/pdf/DELTA1010.PDF
> > > (Look in the middle of page 24.)
> > >
> > > The alsa driver is supposed to support this, too; see e.g.
> > > http://www.alsa-project.org/alsa-doc/alsa-lib/group_pcm.html#a46
> > >
> > > HOWEVER.... When I try to do this with ecasound, I find that there is
> > > considerable run-to-run variability in the timing relationship between
> > > the played and recorded signals.
> > >
> > > I read the documentation and even grepped for terms like "sync" and
> > > "full duplex" without success.
> > >
> > > I looked through the ecasound code and grepped for likely terms
> > > without success.
> > >
> > > I searched the mailing-list archives. I found a lot of discussion
> > > of MIDI-synch (which is !not! what I'm interested in) but not much
> > > about full-duplex analog sync.
> > >
> > > A secondary goal is to have minimal delay between play & record.
> > > The primary goal is that whatever delay there is should be
> > > absolutely stable and reproducible.
> > >
> > > So....
> > > -- Does ecasound have this capability?
> > > -- If so, how do we invoke it?
> > > -- If not, does anybody have any suggestions for what we should do???
> > > (There are several crude workarounds, but doing it right ought
> > > to be easier than kludging it.)
>
> --
> To unsubscribe send message 'unsubscribe' in the body of the
> message to <ecasound-list-request_AT_wakkanet.fi>.
-- To unsubscribe send message 'unsubscribe' in the body of the message to <ecasound-list-request_AT_wakkanet.fi>.
This archive was generated by hypermail 2b28 : Fri Oct 12 2001 - 19:33:13 EEST