On Fri, 2020-07-17 at 17:15 +0800, Aaron Chou wrote: > Thanks for your email! > > On Fri, Jul 17, 2020 at 4:20 PM Tanu Kaskinen <tanuk@xxxxxx> 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 If you mean that can you forcibly disable hardware volume, the answer is no, there's currently no such option. > BTW: > Do you know how the USB sound driver receives the volume data from > PulseAudio? > The ioctl? or other else? I can not determine. PulseAudio calls snd_mixer_selem_set_playback_volume() in alsa-lib. I don't know what that function does internally, you can look at its implementation yourself. -- Tanu https://www.patreon.com/tanuk https://liberapay.com/tanuk _______________________________________________ pulseaudio-discuss mailing list pulseaudio-discuss@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
