Subject: Re: [linux-audio-dev] Ideas for AES/LAAGA/whatever (was Re: sound API libraries, servers, etc.)
From: Jim Peters (jim_AT_aguazul.demon.co.uk)
Date: Wed Apr 25 2001 - 23:08:28 EEST
Jörn Nettingsmeier wrote:
> in real-world audio files (i.e. all but computer-generated music),
> there is no such thing as silence. there is always noise, and with
> open microphones, there is an *important* ambiance component in the
> moments where no intentional sound takes place.
> plus i doubt that any ADC in the world will give you all-zeroes,
> even when you shorten the input.
Sorry - I'm coming from a different angle here. I'm thinking more in
terms of synthesis, where for example you may have an oscillator
controlled by a triggered envelope. When the envelope is complete, we
do certainly have silence. If I set up a network of modules to
emulate a rack of analogue synth boxes to play a tune controlled by a
sequencer, then a lot of the time many of these will be playing
silence - unless I play all the sounds all together all of the time.
So, saving time spent on processing silence seems worthwhile -
particularly if a single analogue-style voice consists of a network of
5-6 plugins. This approach might buy me twice the number of
simulateneously active instruments, or more.
For my imagined application, the risk of underruns due to the
variation in CPU usage would be just about as troublesome as something
unexpectedly peaking into the red - just adjust the sample-rate down a
notch, and carry on.
> as a consequence, to implement your idea you need a noise-gate with
> a threshold, which i think is a bad idea. when i gate, i do so
> *intentionally* and *explicitly*. i don't want clever plugins to do
> that for me.
From my design, anything coming in `live' would be treated as raw data
(not silence, even if by fluke it was all zeros). You would indeed
have to gate it if you really wanted it to be treated as silence.
Jim
--
Jim Peters / __ | \ Aguazul
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