[linux-audio-dev] PTAF link and comments

Steve Harris S.W.Harris at ecs.soton.ac.uk
Tue Feb 4 02:53:01 UTC 2003


On Tue, Feb 04, 2003 at 02:22:31 +0100, David Olofson wrote:
> On Tuesday 04 February 2003 00.41, Steve Harris wrote:
> > On Mon, Feb 03, 2003 at 02:52:54 -0800, Tim Hockin wrote:
> > > > 	* Process mode: Mixed/RT/Off-Line.
> > >
> > > do we really want anything like this?  I have a 1-10 'quality'
> > > level.
> >
> > Not the same thing. I think offline processing allows seek, reverse
> > etc.
> 
> How would you handle (audio time?) seeking and reverse processing?
> 
> Well, of course, it's no problem if the plugin is *designed* for it...

Yes, there was a proposed extension to LADSPA that used seek/read/write
style i/o to access non RT data.
 
> > Its very inconvienient for certain algorithms. The plugin doesn't
> > know ahead of time how big the buffer is going to be, so it cant
> > prealoocate an intermediate buffer.
> 
> Actually, plugins do know the *maximum* buffer size they can get. This 
> is a critical API feature for many plugins.

OK, that would be enough, but its not ideal. Sometimes the most
convienient (and efficient) thing for the plguin to do is to accumulate
into the output buffer.
 
> > Mix is not the same as wet/dry. Imagine you have an effect with an
> > inherant delay of 64 samples, the dry output is the input delayed
> > by 64 samples.
> 
> Good point. But that also means that plugins with delay *have* to do 
> this properly, or they'll ruin the host's efforts to compensate for 
> FX latency.

I was more worried about the comb filtering, but yes, that too.

- Steve



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