Re: [ecasound] LADSPA latency ouput value

From: Sergei Steshenko <sergstesh@email-addr-hidden>
Date: Wed Feb 18 2009 - 12:54:25 EET

--- On Wed, 2/18/09, Julien <julien@email-addr-hidden> wrote:

> From: Julien <julien@email-addr-hidden>
> Subject: [ecasound] LADSPA latency ouput value
> To: ecasound-list@email-addr-hidden
> 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.


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.



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Received on Wed Feb 18 16:15:01 2009

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