[pulseaudio-discuss] The volume control ways in PulseAudio

[Aaron Chou]

Thanks for your email!

On Fri, Jul 17, 2020 at 4:20 PM Tanu Kaskinen <tanuk at iki.fi> wrote:

> On Fri, 2020-07-17 at 10:57 +0800, Aaron Chou wrote:
> > Hi, all:
> >
> > I am the newer about PulseAudio.
> > When I have some time to learn it, I found that there are two ways in
> > volume control, which is software control and hardware control.
> > I can not understand these two ways.
> > The software way means the volume data will not be sent to the hardware?
> > It is unbelievable.
>
> Software volume means that PulseAudio modifies the signal to be softer
> or louder. Hardware volume means that PulseAudio sends the signal
> unmodified and tells the hardware to the modification, which requires
> that the hardware provides an interface for controlling the volume (I'm
> currently using a USB sound card that doesn't provide such interface).
>
em...
I also have an appearance with a USB sound card, and something else is
abnormal.
Such as the volume is set to 0, but it also can play music when the system
reboot or power off.
So I doubt that the volume is not be set to hardware through PulseAudio.

Can I have the following flow chart：

app->pulseaudio(software control)->alsa lib->alsa driver

BTW:
Do you know how the USB sound driver receives the volume data from
PulseAudio?
The ioctl? or other else? I can not determine.

Regards.
Aaron.



> --
> Tanu
>
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