[squeak-dev] Sound mixing makes nasty noises

tim Rowledge tim at rowledge.org
Mon Dec 28 21:48:38 UTC 2020

> On 2020-12-28, at 10:36 AM, Herbert <herbertkoenig at gmx.net> wrote:
> Inside Squeak I saw a lot of clipping as expected, outside I saw
> wrapping whenever it clipped inside.

That would be an interesting thing to prove conclusively. It's not unimagineable that there could be a bug in a unix sound library. Just ofr a moment I got excited looking at the pulse driver code when I spotted it is using 
audioIn.pa_spec.format = PA_SAMPLE_S16LE;
... because I could have sworn that squeak is generating 16 bit BIG endian samples. But no...

Maybe if we make a crafted sound buffer with a clean waveform that we know never gets clipped but does hit the maxval/minval and play it directly with no mixing related calls (because the mixer code does volume scaling etc and internal clipping) we might see what comes out of pulseaudio and indeed alsa. 

tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
MIPS:  Meaningless Indicator of Processor Speed.

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