[LAD] hard realtime performance synth

[David McClanahan]

Hi,

Thanks for the response. Some thoughts


1. Bristol synth was one the first synths I tried. I had installed
Ubuntu(Karma I think. BTW: Ubuntu is based off Debian and that packaging
system didn't seem to save me from breaking things) and then used various
"apt" commands suggested on the Ubuntu Studio site to install sections I
wanted(including the "realtime" kernel). When I ran Bristol(or ZynAddSub for
that matter) it would lockup and not even display the keyboard interface. I
eventually discovered that networking(the loop device interface) was not
hooked in. I got a little further in that graphic interface came up and I
got a plink or 2 before lockup. I'll take a look at the suggestions given
however.

2. As for some of other suggestions, I don't care what interface(X11,curses
etc) is available on the sound host(the dell in this case). As long as I
could control it and get some usable status output that'd be ok. (I'll check
into linux sampler). I could see it functioning perfectly well via some
midi/serial connection  which I think ALSA has.

3. I'm a little worried about what some are calling realtime systems. The
realtime system that is part of Ubuntu Studio and others may be more
preemptible than the normal kernel(as in kernel calls themselves can be
preempted), but that's not a hard realtime system. A hard realtime
system(simplistic I know) might entail a task whose sole job is to pump out
a sinusoidal sound sample to the D-to-A on the sound card. A hard realtime
scheduler would run that task at 44Khz no matter what. This would entail
developing code that when the machine instructions were analyzed, would run
in the time constraints(aka the 44Khz). RTLinux appears to be suitable and
RTAI might be. Perhaps others.

The way things are now even with the "realtime kernel" on U. Studio. , xruns
can occur because there's no hard limit on accessing resources-only
priorities. This may work fine on newer/faster machines but not on the older
ones. Some may say, "Go buy a faster machine". My answer is that won't
necessarily solve the problem which is a proliferation of "systems" on top
of systems without any assurance they'll all work together on time. I could
go buy a new systems but I have the feeling I'd be still "tuning" to get
things running. Roland, Korg, Yamaha put out turnkey products on what I
suspect is simpler hardware and my question is there any reason why similar
turnkey systems could not be developed on a Linux system(even on an older
machine). There may be some reason. I just don't think I've heard it yet.

david


David
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