Re: [ecasound] gates - major change

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Subject: Re: [ecasound] gates - major change
From: Kai Vehmanen (k@eca.cx)
Date: Thu Dec 14 2000 - 02:49:08 EET

On Wed, 13 Dec 2000, Jeremy Hall wrote:

> When we do gates now, when the gate is triggerred, frames are written to
> the output device. When the signal falls below the threshold, we stop
> writing frames. How then do we maintain synch? If enm, for example, is
> used, how do we keep from losing continuity?

Yes, you understood right. The new gates (this applies only to -gc and
-ge) do not guarantee synch nor continuity. This is common for ecasound.
The engine doesn't guarantee these things, but still, most operators
behave nicely. Pitch-shifter (-ei) is another operator that directly
modifies the length of passing buffers (thus causing sync problems if
multiple chains are used). If we didn't allow this, we'd just have remove
-ei and the new -gc and -ge complitely...

> This should be a switch, not a force-to.

Of course, if someone needs the old -gc and -ge, we need to come up with
an alternative. This is no problem. I just don't think the old -gc and -ge
had many uses. In many cases, the noisegate (-enm, still works as before)
works a lot better. And there seems to be better (more generic) ways
to do exactly what -gc and -ge do.

For instance, we could add a controller with params
-kgc:param,low,high,start-time,len ... notice the 'start-time,len' params
are exactly the same as with -gc (-gc:start-time,len). To simulate -gc,
you'd issue:

ecasound -i file.wav -o /dev/dsp -ea:100 -ksc:1,0,100,2,3
ecasound -i file.wav -o /dev/dsp -gc:2,3

When 'gate' is open, -ksc outputs the lower control value, which in
this case is 0 (-ea:0 -> mute); when open, the high value is used (100 ->
-ea:100 -> let signal go through).

But, I can add a switch to -gc and -ge, if you need the old behaviour
back. Then we'd have -gc:start-time,len,mode ... So we'd have just
more parameters... 

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