Subject: Re: [linux-audio-dev] Combining audio streams
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Fri Feb 08 2002 - 17:57:51 EET
On Fri, Feb 08, 2002 at 04:37:56 +0100, Christian Naeger wrote:
>
> If there are say two input streams, and I simply add the 16bit shorts from
> both streams, I get lots and lots of overflows. If I divide each stream by
> two before adding them, it sounds very bad.
You are probably causing an overflow in your maths, something like this
should work fine:
short out, in1, in2;
int tmp = (in1 + in2) / 2;
if (tmp > SHTR_MAX) {
out = SHRT_MAX;
} else if (tmp < SHRT_MIN) {
out = SHRT_MIN;
} else {
out = tmp;
}
If your hearing is very good then you could be hearing distorion from the
bottom bit, in which case you will need to dither the audio, but that
is a whole lot harder.
- Steve
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