'Twas brillig, and David Henningsson at 07/12/10 08:35 did gyre and gimble: > On 2010-12-04 19:09, Colin Guthrie wrote: >> 'Twas brillig, and David Henningsson at 02/12/10 10:38 did gyre and >>> Let's play with the idea that we added a configurable "Direction" key to >>> these profiles that controlled whether we moved up or down to the >>> nearest step. Wouldn't that help? Then we could have "Mic Boost" first >>> in chain, then set it to move down rather than up. >>> Or maybe that we should instead say that if we're above 0 dB, we move >>> down, and if we're below 0 dB, we move up? Would that make sense? >> >> I'm not really sure here. A specific direction key may complicate what >> is already a rather complicated thing, so if we can possibly do things >> sensibly without it, then I'd suggest that would be more attractive (if >> it works reliably enough). > > We want to maximise quality while avoiding digital distortion, that's > basically the problem in a nutshell. We're assuming (sometimes > incorrectly; but that's our best guess) that this golden spot will be > achieved with all sliders at 0 dB. > > I think my approach makes sense, unless I'm missing something: If we're > aiming for something above 0 dB, let's round down to make sure we avoid > distortion, and if we're below 0 dB, let's round up to make sure we get > maximum quality. I see what you mean here. At present we always pass +1 to the various alsa functions that take it (e.g. snd_mixer_selem_set_playback_dB()), but after we adjust for base volume, we may be requesting alsa volumes of >0dB (e.g. if our base volume is at 30%, then 35% will be a +dB in alsa). So yeah, I think you are correct here, the rounding needs to factor this in. It's a pity there is not a fourth option to these calls in alsa (i.e. in addition to -1, 0, +1) that did "appropriate rounding", but we can deal with this I guess. > And then we always start with the control that's closest to the physical > hardware and work our way in. I guess so. > What's in and out here; that's currently determined by the order in > which PulseAudio reads them in, right? That complicates matters a little > given the include file structure and so I'm thinking maybe we should add > a "extremity=<number>" key to the config file? (This is unrelated to the > direction key suggested previously.) We would then start with the one > having the highest "extremity" score. I guess that would allow for a clearer, more deterministic approach. > Otherwise we would get in trouble if we have a profile with a volume > control B (with extremity=2), which then includes a file with both > control A (with extremity=1) and control C (with extremity=3) in the > same include file. > > I think that would actually make things clearer. What do you think? While I've never completely grasped absolutely everything in the mixer profiles stuff, I think you speak sense :) Cheers Col -- Colin Guthrie gmane(at)colin.guthr.ie http://colin.guthr.ie/ Day Job: Tribalogic Limited [http://www.tribalogic.net/] Open Source: Mageia Contributor [http://www.mageia.org/] PulseAudio Hacker [http://www.pulseaudio.org/] Trac Hacker [http://trac.edgewall.org/]
