[Ardour-Dev] Ardour VST freeze

Paul Davis paul at linuxaudiosystems.com
Sun Mar 1 12:49:03 PST 2009

On Sun, Mar 1, 2009 at 2:07 PM, Martin Profittlich
<martin at profittlich.com>wrote:

> Hello!
> The current SVN version of ardourvst (2.0-ongoing, rev. 4709) crashes
> when I try to freeze a track with a VST plugin (Guitar Rig in my case).
> This happens because during freeze two threads are accessing the plugin
> at the same time. If I put a mutex around processReplacing() in
> vst_plugin.cc, the freeze completes, but of course with a horrible
> performance due to locking (xruns galore) and with audible artifacts,
> because time-based effects get confused by the merged stream.

nice detective work. can you show me a backtrace of the dual thread access?

I guess the two threads are the freeze thread and the regular JACK
> thread. Is this correct?
> I think the solution would be to prevent the JACK thread from accessing
> the plugin during freeze altogether, but I'm not sure what the proper
> way to do this is. Any suggestions?

it should be possible by setting Session::processing_prohibited, see for
example libs/ardour/session.cc:4106
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