Subject: Re: [linux-audio-dev] mixing algorithms...
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Sun Sep 21 2003 - 23:36:09 EEST
On Sun, Sep 21, 2003 at 03:10:46PM -0400, David E. Storey wrote:
> dither in a case like that? Doesn't averaging also imply truncation of
> your source signal? Am I missing something here? I've tried looking to
> see what jack and ardour do, but was lefting wondering WHERE to look.
JACK just adds them, its the users resposibility to ensure they dont clip
too much. People are used to reducing the volume when they hear clipping.
If you want to guarantee no clips you have to either divide by the number
of channels (not recommended, it gets quieter when you add more channels)
or put a limiter after the add (such as the LADSPA Lookahead Limiter). A
lookahead limiter will add latency though.
If you just want to make the cliping less bad you could add a compressor
with a high ratio and fast attack or a soft clip (also available in
LADSPA form). I usually run a jack-rack with Lookahead Limiters in it at
the end of my JACK chain when playing live.
If your woking in >16 bit maths and outputing 16bit you should dither,
otherwise you dont have to. Its the resposibility of the process that
reduces the bit-width.
- Steve
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