On 04/03/2008, John Sigler <linux.kernel@xxxxxxx> wrote: > James Courtier-Dutton wrote: > > > John Sigler wrote: > > > >> I have an RME AES-32 PCI board. > >> http://www.rme-audio.de/en_products_hdsp_aes32.php > >> > >> When I boot, every channel has its volume set to 0. > >> > > >> http://lxr.linux.no/linux/sound/pci/rme9652/hdspm.c#L3396 > >> http://lxr.linux.no/linux/sound/pci/rme9652/hdspm.c#L965 > >> > >> Apparently, it's not the board's firmware, it's the device driver > >> which mutes every channel at initialization. > >> > >> Does anybody know why this is done? > > > > It was done to protect one's ears. > > > Could you expand on your explanation? Some time ago, there was no way to tell, from user space, if 100% or 50% was 0db, -50dB or +50dB. As a result, the safest value to use was the minimum value being either 0% or mute. That has changed with alsa 1.0.16, as dB gain information is now available. > > Intuitively, I would have initialized every input channel and output > channel to "leave the signal as is" (what you refer to as 0 dB). > > > As a matter of fact, 32768 is exactly 50% of 65536, but I'm not sure I > understand the point you're making. The driver source code seems to > imply that 32768 is special in that it is named UNITY_GAIN. That would > seem to indicate that this volume level corresponds to 0 dB, wouldn't it? But the value of 50% does not correspond to 0 dB for all sound cards. > > > > Now that we have these dB gain levels, we could potentially set all > > mixer controls to 0dB, i.e. not gain and not attenuation, with only > > the master output control being set to a lower value so as to avoid > > ears breaking. > > > I don't know where the master output control is. Do you see it in the > outputs of 'amixer' or 'amixer contents' I provided in one of my > previous messages? > version 1.0.16 of amixer will have the dB values. You also have to have version 1.0.16 of alsa-driver and alsa-lib. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
