On 03/03/2008, John Sigler <linux.kernel@xxxxxxx> wrote: > (I'll try answering some of my questions.) > > > 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. > > Is this done by the board's firmware? > > > 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. > > > > 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. Now, the ALSA mixer has been improved, and we can now report gain levels instead of these mostly meaningless percentage values. Try running "alsamixer", it will show dB values for each mixer control if the driver has been updated to report the information. So, 0 dB means "leave the signal as is" -X dB means "attenuate the signal by X db" X db means "gain the signal by X db" 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. James ------------------------------------------------------------------------- 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
