Re: [Audacity-devel] Dynamic Compressor Effect

[Peter S. <pet...@gm...>]

On Sun, Mar 28, 2021 at 12:46 PM Max Maisel <mm...@po...> wrote:

> Hi James,
>
> it's no problem for me to wait for the 3.0.1 release.
>

Max,

I'm hoping that between us we can get the real time preview working before
this
gets released - it will make it much more useful (and more fun).

Peter



> The latency is mainly caused by various kinds of lookahead. One
> lookahead is selected directly by the user, another lookahead is
> implicit in case of the exponential fit envelope detector because the
> algorithm needs to process the signal backwards in the attack stage.
>
> Latencies in the range of minutes are extreme cases if users select
> high lookahead times or, in case of exponential fit, high attack times.
> But I don't want to limit the ranges of the lookahead and attack time
> sliders for offline processing just because of latency in realtime
> mode.
>
> When using the analog simulation envelope detector together with low
> lookahead (a few milliseconds) like a real analog compressor, there is
> almost no noticably latency.
>
> Max
>
> On Saturday, 27 March 2021 at 14:41, James Crook wrote:
> > Hi Max.
> >
> > The previous update I had on this was about the long latency.
> > Disabling realtime preview is sort of OK, but something seems wrong.
> > A one minute latency is colossal.  That points to something
> > underlying wrong.
> >
> > Also 3.0.1 has now become very very much a maintenance release for
> > addressing the 3.0.0 unitary project issues.  Paul would love to get
> > some structural
> > changes in that improve independence between pieces of code, and I am
> > saying no.
> > We'd also like to get portaudio and FFmpeg library updates in, and I
> > am saying no.
> >
> > It is pretty clear that the release after 3.0.1 is going to be quite
> > soon, so as RM
> > I'm sorry to have to say that your compressor will have to sit out
> > for 3.0.1.
> >
> > 3.0.1 is due to actually release on 17th April, so it's a further
> > delay of about 3
> > weeks for you in seeing progress on your compressor getting in to
> > Audacity.
> >
> > Is there a good reason for the very long latency?
> >
> > --James.
> >
> >
> >
> >
> > On Sat, 27 Mar 2021 at 07:56, Max Maisel <mm...@po...> wrote:
> > > Hi all,
> > >
> > > I've polished my Dynamic Compressor effect and think it is ready
> > > now
> > > for inclusion.
> > >
> > > Since my last mail (see
> > > https://sourceforge.net/p/audacity/mailman/message/37109016/ for
> > > the
> > > initial message), I mainly reworked the user interface accoring to
> > > your
> > > feedback and fixed several bugs.
> > >
> > > The effect is basically realtime capable but for now realtime
> > > preview
> > > is disabled after some discussion with Steve because there are
> > > bad user experience due to high processing latency in the effect at
> > > some settings.
> > >
> > > Main probleme here is, that the RealtimeEffectManager gives the
> > > effect
> > > a small block, e.g. 256 samples, and expects the same amount of
> > > samples
> > > in return. So if an effect like my compressor has a high processing
> > > latency, there can be an initial silence for over one minute which
> > > the
> > > users will think is a bug. Any changes made to the effect settings
> > > will
> > > only take effect after this long time as well.
> > >
> > > A possible solution would be latency compensation in the
> > > RealtimeEffectManager so that the effect can request the required
> > > amount of samples in advance at the beginning or when the user
> > > changes
> > > settings. The silence at the beginning can then be discarded so
> > > that
> > > users do not notice it. But this is out of scope of the compressor
> > > effect changes.
> > >
> > > The lastest revision including CI builds can be found in my pull
> > > request at https://github.com/audacity/audacity/pull/676.
> > >
> > > The latest documentation for the effect is can be found at
> > > https://alphamanual.audacityteam.org/man/Dynamic_Compressor.
> > >
> > > I'm looking forward to further feedback and integration.
> > >
> > > Max
> > >
> > >
> > >
> > >
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