Re: [ecasound] LADSPA latency ouput value

--- On Wed, 2/18/09, Julien <julien@recisio.com> wrote:

> From: Julien <julien@recisio.com>
> Subject: Re: [ecasound] LADSPA latency ouput value
> To: sergstesh@yahoo.com
> Cc: ecasound-list@lists.sourceforge.net
> Date: Wednesday, February 18, 2009, 3:08 AM
> I have read the following discussion:
>
> http://ardour.org/node/761
>
> they says that LADSPA spec include a latency report using a
> output.
> Ardour have a delay compensation mechanism which read
> latency of each
> plugins.
>
> Quoting :
>
> Steve Harris and I came up with a kludge solution for
> LADSPA (an output
> control port called “latency”), and a few other LADSPA
> developers
> supported it. in VST, its a host->plugin callback called
> getInitialDelay().
>
> ecasound in verbose mode display outputs of LADSPA plugins
> which contain
> the latency output but the value is read at initialisation
> time so it is
> not the effective latency !
>
> If you have the following package installed :
>
> ladspa-sdk
> swh-plugins
>
> You can analyse the LADSPA plugin I use :
>
> analyseplugin
> /usr/lib/ladspa/fast_lookahead_limiter_1913.so
>
> Plugin Name: "Fast Lookahead limiter"
> Plugin Label: "fastLookaheadLimiter"
> Plugin Unique ID: 1913
> Maker: "Steve Harris <steve@plugin.org.uk>"
> Copyright: "GPL"
> Must Run Real-Time: No
> Has activate() Function: Yes
> Has deativate() Function: No
> Has run_adding() Function: Yes
> Environment: Normal or Hard Real-Time
> Ports: "Input gain (dB)" input, control, -20 to
> 20, default 0
> "Limit (dB)" input, control, -20 to 0, default 0
> "Release time (s)" input, control, 0,01 to 2,
> default 0,5075
> "Attenuation (dB)" output, control, 0 to 70
> "Input 1" input, audio
> "Input 2" input, audio
> "Output 1" output, audio
> "Output 2" output, audio
> "latency" output, control
>
> which display the output latency !
>
> Is there a way to display this output at the end of the
> mixing
> processus ?
>
> Thanks,
> Julien.
>
> Le mercredi 18 février 2009 à 02:54 -0800, Sergei
> Steshenko a écrit :
> >
> >
> > --- On Wed, 2/18/09, Julien <julien@recisio.com>
> wrote:
> >
> > > From: Julien <julien@recisio.com>
> > > Subject: [ecasound] LADSPA latency ouput value
> > > To: ecasound-list@lists.sourceforge.net
> > > Date: Wednesday, February 18, 2009, 1:48 AM
> > > Hello,
> > >
> > > I use LADSPA plugin with ecasound (one plugins at
> the end
> > > of the chain
> > > setup) but the output latency of the plugin is
> not use (or
> > > display) by
> > > ecasound !
> > >
> > > Do you plan to adjust the output file according
> to the
> > > latency output of
> > > the plugin use. For example if the plug have 7ms
> of
> > > latency, I will have
> > > 7 ms of silence at the beginning of the output
> file even if
> > > the input
> > > file contain sound in the first 7 ms. The end of
> the file
> > > is just
> > > truncate : the last 7 ms of the input file is not
> present
> > > in the output
> > > file because of the latency offset.
> > >
> > > It would be nice if you can "offset"
> the output
> > > file, or another way to
> > > work around this issue is to just display the
> value return
> > > by the LADSPA
> > > plugin on the "latency output".
> > >
> > > I really need this information in order to
> synchronize
> > > file.
> > >
> > > Thanks,
> > > Best Regards,
> > > Julien.
> > >
> > >
> >
> > Julien,
> >
> > off the top of my head LADSPA plugins do not report
> latency - AFAIR not
> > part of LADSPA spec.
> >
> > Furthermore, FFT-based plugins may have huge latency,
> e.g. 1 second -
> > depends on the task.
> >
> > In more general terms - FIR filter works with its
> worst/longest latency,
> > while IIR filter starts producing sound more or less
> immediately - provided its FIR part is short :-).
> >
> > So, I guess, the only choice you have is to
> measure/calculate latency
> > yourself and to adjust your setup accordingly.
> >
> > Regards,
> > Sergei.
> >

Julien,

I am not familiar with all details of these new developments.

You report shows "latency" as control output (_not_ control input); I am
not sure 'ecasound' has an infrastructure for LADSPA control outputs.

And, anyway, I am not an 'ecasound' developer.

Regards,
  Sergei.

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Received on Wed Feb 18 16:15:02 2009