Lennart Poettering wrote: > On Wed, 17.02.10 12:47, Eliot Blennerhassett (linux@xxxxxxxxxxxxxxxx) wrote: > >> For our cards this is adjustable, but lets say for consumer cards it is >> fixed. This information is not currently available via the ALSA >> API. > > I wonder how realistic it would even be to add an API for > this. i.e. can we even know the refernce level? On many cards most > likely not. For example, for my integrated USB speakers speaking of a > reference voltage would already be misleading... Certainly. Same for laptop speakers. Perhaps could define 0dB as the highest valid volume setting that doesn't cause distortion in the audio when playing a full scale digital signal. Otherwise the absolute reference might be dBSPL at X metres from the speaker ;) (before anyone answers - in this context I'm joking.) > Yepp, that's the exactly what I was asking, Jaroslav's measurements > suggested to shift one of the mixer controls from 0..x dB to -x..0 dB > and I was just wondering why, since we don't define the ref level in > ALSA, hence the shift is kinda arbitrary... > > Anyway, I am not pushing for adding an API for reference levels to > ALSA. We define controls with names like "LineIn0 Level","LineOut1 Level" which we document as having units of dBu. Given that no other driver has this, its the de-facto standard ;) > As mentioned for the PA case I decided to shift 0dB to max > amplification in any case, which I think is a workable way to avoid > this problem. Sure. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
