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? Intuitively, I would have initialized every input channel and output channel to "leave the signal as is" (what you refer to as 0 dB). >> I used amixer to change the volume. >> >> Simple mixer control 'Chn',1 >> Capabilities: volume volume-joined >> Playback channels: Mono >> Capture channels: Mono >> Limits: 0 - 65536 >> Mono: 32768 [50%] >> >> What is the meaning of the level? >> Does 100% mean the signal is left unmodified? >> and 50% means the amplitude is multiplied by 0.50? >> >> http://lxr.linux.no/linux/sound/pci/rme9652/hdspm.c#L377 >> >> #define UNITY_GAIN 32768 >> #define MINUS_INFINITY_GAIN 0 >> >> So, volume = 32768 means "leave the signal as is" and volume = 0 >> means "mute the channel". Is that correct? >> >> What would volume = 16384 and volume = 49152 mean? >> (What is the scale?) > > There is no scale there. > It can have a range of value between 0 and 65536 > 32768 being about 50% of 65536. 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? > 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? Regards. ------------------------------------------------------------------------- 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
