Re: [ecasound] LADSPA latency ouput value

From: Sergei Steshenko <sergstesh@email-addr-hidden>
Date: Fri Feb 20 2009 - 21:05:14 EET

--- On Fri, 2/20/09, Joel Roth <joelz@email-addr-hidden> wrote:

> From: Joel Roth <joelz@email-addr-hidden>
> Subject: Re: [ecasound] LADSPA latency ouput value
> To: ecasound-list@email-addr-hidden
> Date: Friday, February 20, 2009, 10:49 AM
> On Fri, Feb 20, 2009 at 07:10:23AM -0800, Sergei Steshenko
> wrote:
> > Let's forget for a time being about LADSPA and
> 'ecasound' and let's think
> > about the following:
> >
> > 1) there may be more than one plugin in chain setup;
> > 2) the plugins can be connected in various topologies
> (serially, in parallel).
> >
> > Given the above, what latency should be
> reported/used/compensated for ?

> So,
> I'm dealing with a group of tracks that are implemented
> as
> parallel chains.

> Each track in Nama is a chain, and each chain can have
> a series of plugins. Many LADSPA plugins report their
> latency, so it's easy to sum up the plugin latencies
> for
> each chain and add compensation so each chain adds
> the same latency as the chain which add the most latency.
> The latter is the immediate case that I am dealing with.
> Does this make sense? Am I missing something?
> Regards,
> Joel

Yes, it makes sense.



P.S. Regarding

If I'm recording while monitoring a backing track--a very
common scenario--then latency is an issue even with no
effects applied.

WAV file 1 --> buffering --> soundcard DAC --> monitor --> performer

        microphone/line input --> soundcard ADC --> buffering --> WAV file 2

It would be great to have a simple tool to measure the
latency of this signal path, perhaps comparing the positions
of peaks of a click track.

- acquire a small (amplified) speaker and drive it by the computer which
produces "WAV file 2".

Place that small speaker close to the microphone - I think with such a setup it should be trivial to measure latency of

microphone/line input --> soundcard ADC --> buffering

chain. You might need feed into the microphone some special signal and have a matched filter for it - to minimize ambient noise influence.


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Received on Sat Feb 21 00:15:01 2009

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