[pulseaudio-discuss] PA volume effects

[Lennart Poettering]

On Mon, 27.04.09 18:53, Daniel Mack (daniel at caiaq.de) wrote:

> > > 'aplay -Dplughw foo.wav', it is clearly audible that PA adds some kind
> > > of amplification to the material (I would guess ~3dB), even though all
> > > GUI accessible levels are set to 100%.
> > > 
> > > The driver I'm working on does not have any volume control features,
> > > hence this must be done in software.
> > > 
> > > Has that been encountered before?
> > 
> > Please try to reproduce this, then do "ls" in pacmd and paste it
> > somehere. This should show if PA does digital amplification for any of
> > the active streams.
> 
> It's always reproducable, here is the output:
> 
> 	http://caiaq.de/download/tmp/pacmd-distortion.txt
> 
> Let me know if I can provide more details.

Hmm, that output suggests everything is in order. Both the sink and
the stream are fixed to 0dB so PA shouldn't touch the data at all,
just pass it through to the device.

Hmm, what makes me wonder though is the 's24be' sample format. There
might be something wrong with the conversion code for that. 

s24be is 24 bit packed big endian. Is that really the native sampling
format of the device?

(Hmm, ich weiss ja nicht, was das genau für nen Device ist, aber wenn
Ihr das Dingen kurz nach Friedrichshain ausleihen wollt, dann schau
ich's mir mal an und fix Euch den Converter-code ;-))

Lennart

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Lennart Poettering                        Red Hat, Inc.
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