Re: Intercom
- From: Tim Wescott <tim@xxxxxxxxxxxxxxxx>
- Date: Tue, 07 Aug 2007 11:42:34 -0500
On Tue, 07 Aug 2007 10:09:35 -0400, Jerry Avins wrote:
eran wrote:
Hiwere?
I need some confirmation on a intercom application.
I want to add several audio signals that where sampled by a A/D linear
conversion and then FIR filtered.
Can I just add the samples in two compliment format ?
Yes. Well, sort of yes. You add them in the format appropriate to them
which I assume to be two's complement. Beware of overflow. Strictly,
adding two signals requires an extra bit to avoid it. Adding four
requires two extra bits. If you don't have the bits to spare, then
you're better off saturating than allowing the sum to wrap around.
Jerry
And you're even better off with some sort of a soft saturation scheme, and
you're off better yet if you do some sort of automatic volume limiting or
companding no keep the saturation at a minimum.
Allowing the sum to wrap (as happens with most C compilers) makes the
distortion _really bad_.
--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com
Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.
- References:
- Intercom
- From: eran
- Re: Intercom
- From: Jerry Avins
- Intercom
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