Subject: Re: [ecasound] full-duplex sync
From: CLOTILDE Guy Daniel (guy.clotilde_AT_wanadoo.fr)
Date: Fri Oct 12 2001 - 14:16:53 EEST
Hi
Yes
Ecasound does it.
It's the system (hardware, drivers and kernel) who needs to be tuned.
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.
With drivers I mean you can try OSS or alsa.
Above all, tuning your kernel can lead you up to a 1,5 millisecond of latency.
A google search with 'morton low-latency kernel patch' should lead you to the one that match your kernel version.
And this is where the real thing begin! ahahahahhaaaaaaaaa!
Well, seriously it's not so easy, but it can be achieved with some readings.
Ah before you try to recompile your kernel, I got to say that for me, it didn't work unless I type 'make mrproper' before 'make menuconfig' on Mandrake.
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.)
>
> Thanks --- jsd
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