Re: [linux-audio-dev] more on LADSPA

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Subject: Re: [linux-audio-dev] more on LADSPA
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Wed Nov 22 2000 - 01:32:03 EET


This is why I propose not to use LADSPA when implementing
"applications-as-plugins".
With all the bells and whistles an app such your HDR requires,
LADSPA will loose its simplictiy failing to deliver its initial goal.

As for the samplerate issues, we would need some kind of arbitration
between plugs and the host, but some problems may arise if you run
several plugs (like your HRD) which are rate dependent.

What if HDR1 works only at 48kHz and HDR2 only at 44.1kHz ?

IMHO the samplerate should be dictated by the host, but we could
give the plugs the possiblity to ask the host for a certain samplerate.

If all plugs accept samplerate X then run the net with this rate,
otherwise I'm afraid but we will have to interpolate.

I understand that (assuming ardour runs as a plugin within the virtual studio
host) you want to let the user specify the samplerate from within ardour's
 control panel and that's Ok.

But what does happen if another "application" is running at the same time
but cannot handle the new sampling rate (perhaps due to algorithmic constraints
or other stuff) ?
At this point the ideal would be the host popping up a dialog and informing
the user that there is a problem with the samplerate.
3 choices:
- deactivate the plug which cannot handle the new samplingrate
- insert a resampler at the ins and outs of the problematic plugin
- keep the old samplingrate

everyone happy with such a scheme ?

As said I'd like the samplerate be a property of the host in order
to perform eventual arbitration.

thoughts ?

Benno.

On Tue, 21 Nov 2000, you wrote:
> how do we propose to handle plugins that wish to operate at and only
> at a given sample rate ?
>
> the specific case i am thinking of here is an HDR plugin. suppose its
> editor has been used to set its recording rate to 44.1kHz, but the
> current audio interface rate is 48kHz.
>
> this seems like quite a conundrum. the rate of the recording is a
> property of the recording, not the audio interface (i've learned of a
> mistake there with ardour). but we surely can't be requiring that the
> recording's data be continuously up-or-down sampled ?
>
> if a plugin can't request a required sample rate of the host, then a
> plugin cannot be used for recording without making the sample rate a
> property of the host. this in turn creates an ugly user experience,
> where all the properties of other digital recording media (ADAT, CD's,
> DAT) etc. fly out the window, and a recording no longer can specify
> its "rate", and using it in a host set to N kHZ has a different result
> than in one at X kHZ.
>
> does anyone think that this is really OK ? most plugins are not rate
> dependent, so this is quite unusual :)
>
> --p


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