[gmpi] Re: 3.9 (draft) use cases and stuff

  • From: "Koen Tanghe" <koen@xxxxxxxxxxxxxxxxxxx>
  • To: <gmpi@xxxxxxxxxxxxx>
  • Date: Fri, 20 Feb 2004 01:15:26 +0100

On Thursday, February 19, 2004 9:37 PM [GMT+1=CET],
Jeff McClintock <xxxjeffmcc@xxxxxxxxxxxxx> wrote:

> 2. Tempo sync
>   A plugin wants to do a tempo-synced delay.  The plugin needs to find the
> current tempo, and when that tempo changes.
>
> A tempo synced delay does not need to know the future. It's got to accept
> that if some audio enters the delay just before a tempo change, then that
> audio will emerge at the wrong time.  That's a rare situation though, and
> hard to fix.

Unless we can do sample-per-sample processing instead of block based in the
future (then you can be off with at most 1 sample), but let's forget about
that...

> 3. Quantizing

> Very scary, If the tempo changes, then the plugin's delay compensation has
> to change?

First thing that sprung to my mind too...

>   I've never implemented plugin delay compensation, so i may be wrong,
> but I figure it's not something you can recalculate on the fly because it
> involves inserting delays into the graph.

No idea, but it seems to be not trivial at all, indeed!

>   I think in this example, the quantizer has to request enough processing
> delay to cope with a reasonable tempo range, or simply run offline.

Yes, that seems to be the only thing it can do.

Or maybe (just thinking out loud here), it could be allowed to send events
with time stamps that go back in time. The receiver of the events can then
still use the info (for storing at the right moment), but only the real-time
playback possibility is gone. Don't know if this is a good idea though
(makes me think of the "send as fast as you can / jitter" or "use a fixed
delay" issue we discussed some time ago...)

Koen



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